U.S. patent application number 13/389574 was filed with the patent office on 2012-06-07 for electric operating machine.
Invention is credited to Kazuhiko Funabashi, Yoshihiro Hoshi, Hiromi Ozawa, Nobuhiro Takano, Hideyuki Tanimoto, Chikai Yoshimizu.
Application Number | 20120139456 13/389574 |
Document ID | / |
Family ID | 43530201 |
Filed Date | 2012-06-07 |
United States Patent
Application |
20120139456 |
Kind Code |
A1 |
Takano; Nobuhiro ; et
al. |
June 7, 2012 |
ELECTRIC OPERATING MACHINE
Abstract
When a main switch (12) is turned ON, an electric operating
machine (1) is put in the standby mode. With a trigger (13) being
pulled in the standby mode, a power supply circuit (16) applies a
voltage to a drive part (30). The power supply circuit (16) adjusts
the voltage applied to the drive part (30) for a voltage
corresponding to the pulling rate of the trigger (13). When the
current running toward the drive part (30) exceeds the rated value
of the drive part (30), the power supply circuit (16) automatically
stops power supply to the drive part (30). On the other hand, when
the output voltage of a battery (50) drops and the battery (50) is
put in an overdischarge state, power supply to the drive part (30)
is automatically stopped. When it is detected that the battery (50)
undergoes an abnormal event, power supply to the drive part (30) is
automatically stopped.
Inventors: |
Takano; Nobuhiro;
(Hitachinaka-shi, JP) ; Funabashi; Kazuhiko;
(Hitachinaka-shi, JP) ; Tanimoto; Hideyuki;
(Hitachinaka-shi, JP) ; Yoshimizu; Chikai;
(Hitachinaka-shi, JP) ; Ozawa; Hiromi;
(Hitachinaka-shi, JP) ; Hoshi; Yoshihiro;
(Hitachinaka-shi, JP) |
Family ID: |
43530201 |
Appl. No.: |
13/389574 |
Filed: |
August 27, 2010 |
PCT Filed: |
August 27, 2010 |
PCT NO: |
PCT/JP2010/005311 |
371 Date: |
February 8, 2012 |
Current U.S.
Class: |
318/139 ;
310/50 |
Current CPC
Class: |
H01M 10/4221 20130101;
H01M 10/42 20130101; H01M 10/48 20130101; H01M 50/209 20210101;
H02J 7/00306 20200101; A01D 69/02 20130101; H02J 7/0063 20130101;
H01M 50/579 20210101; H02J 7/0029 20130101; H02P 29/027 20130101;
H02J 7/0031 20130101; H01M 10/0525 20130101; Y02E 60/10 20130101;
H02K 7/145 20130101; H02K 3/26 20130101; G05B 19/048 20130101; H02J
7/0026 20130101; H01M 10/425 20130101 |
Class at
Publication: |
318/139 ;
310/50 |
International
Class: |
H02P 7/292 20060101
H02P007/292; H02K 7/14 20060101 H02K007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 28, 2009 |
JP |
2009-199066 |
Sep 30, 2009 |
JP |
2009-229092 |
Jan 14, 2010 |
JP |
2010-006186 |
Claims
1. An electric operating machine comprising: a power source part
including a battery mounting part for mounting a battery, and a
voltage conversion part converting and outputting the voltage input
from the battery; and an electric motor to which a work tool
rotating in association therewith is connected and that rotates
upon application of the voltage output from the voltage conversion
part, characterized in that the power source part further includes
a voltage measuring part measuring the voltage applied to the
electric motor and outputting it to the voltage conversion part;
and the voltage conversion part adjusts the output voltage so that
the voltage output from the voltage measuring part has a given
level.
2. The electric operating machine according to claim 1
characterized in that a battery of any voltage is mounted on or
dismounted from the battery mounting part.
3. The electric operating machine according to claim 1
characterized in that the power source part further comprises an
overcurrent protection part blocking the current running toward the
electric motor when the current running toward the electric motor
exceeds a given value.
4. The electric operating machine according to claim 1
characterized in that the electric operating machine further
comprises a first announcing part announcing that an overcurrent is
running when the current running toward the electric motor exceeds
a given value.
5. The electric operating machine according to claim 1
characterized in that the power source part further comprises an
overdischarge protection part blocking the current running toward
the electric motor when the voltage output from the battery becomes
lower than a predetermined voltage.
6. The electric operating machine according to claim 1
characterized in that the electric operating machine further
comprises a second announcing part announcing that the battery is
overly discharging when the voltage output from the battery becomes
lower than a predetermined voltage.
7. The electric operating machine according to claim 5
characterized in that the power source part further comprises a
voltage determination part determining the predetermined voltage
based on battery information of the battery that is output from the
battery.
8. The electric operating machine according to claim 1
characterized in that the power source part further comprises a
battery abnormality stop part blocking the current running toward
the electric motor according to battery abnormality signals output
from the battery when the battery undergoes an abnormal event.
9. The electric operating machine according to claim 8
characterized in that the battery abnormality stop part blocks the
current running toward the electric motor until the battery is
dismounted from the battery mounting part since it receives the
battery abnormality signals.
10. The electric operating machine according to claim 1
characterized in that the electric operating machine further
comprises a third announcing part announcing that the battery
undergoes an abnormal event when the battery undergoes an abnormal
event.
11. The electric operating machine according to claim 1
characterized in that the electric operating machine further
comprises a trigger, and the voltage measuring part applies to the
voltage conversion part a voltage according to the pulling rate of
the trigger.
12. The electric operating machine according to claim 1
characterized in that the power source part further comprises a
trigger switch part blocking the current running toward the
electric motor when the pulling rate of the trigger is lower than a
given rate and allowing a current to run through the electric motor
when the pulling rate of the trigger is equal to or higher than the
given rate.
13. The electric operating machine according to claim 12
characterized in that the power source part further comprises a
main switch part blocking the current running from the battery to
the trigger switch part when it is turned OFF and allowing the
current when it is turned ON.
14. The electric operating machine according to claim 13
characterized in that the electric operating machine further
comprises a first light emitting part emitting light when the main
switch part is ON.
15. The electric operating machine according to claim 1
characterized in that the electric operating machine further
comprises a remaining battery level display displaying the
remaining battery level according the voltage output from the
battery.
16. The electric operating machine according to claim 1
characterized in that the power source part further comprises a
constant voltage circuit outputting a constant voltage from the
voltage output from the battery.
17. The electric operating machine according to claim 16
characterized in that the electric operating machine further
comprises a sound reproducing part operating upon application of a
voltage output from the constant voltage circuit, decoding sound
data, and reproducing sound information.
18. The electric operating machine according to claim 16
characterized in that the electric operating machine further
comprises a radio operating upon application of a voltage output
from the constant voltage circuit and detecting sound information
in radio waves received by an antenna.
19. The electric operating machine according to claim 16
characterized in that the electric operating machine further
comprises a speaker amplifying the sound information and making
sound by a voltage output from the constant voltage circuit.
20. The electric operating machine according to claim 1
characterized in that the electric motor is a coreless motor.
21. The electric operating machine according to claim 20
characterized in that the electric operating machine further
comprises a coupling part on whose one end the power source part is
arranged and on whose other end the electric motor is arranged.
22. The electric operating machine according to claim 1
characterized in that the electric operating machine further
comprises a second light emitting part emitting light when the
electric motor is powered.
23. The electric operating machine according to claim 1
characterized in that the electric operating machine further
comprises a fourth announcing part announcing the power supply when
the electric motor is powered.
24. The electric operating machine according to claim 20
characterized in that the coreless motor includes a rotor and a
stator; the rotor includes a fixed output shaft; one of the rotor
and stator comprises a disc-shaped coil substrate including
multiple nearly annular coils arranged in the circumferential
direction around the output shaft when seen in the axial direction
of the output shaft; and the other of the rotor and stator
comprises a magnet generating a magnetic flux passing through the
coil substrate in the axial direction of the output shaft.
25. An electric operating machine comprising: a coreless motor; a
power source part comprising a mounting part to which a lithium
rechargeable battery is detachably mounted; and a coupling part
holding the coreless motor at one end and holding the power source
part at the other end, characterized in that: the coreless motor
includes a rotor and a stator; the rotor includes a fixed output
shaft; one of the rotor and stator comprises a disc-shaped coil
substrate including multiple nearly annular coils arranged in the
circumferential direction around the output shaft when seen in the
axial direction of the output shaft; and the other of the rotor and
stator comprises a magnet generating a magnetic flux passing
through the coil substrate in the axial direction of the output
shaft.
26. An electric operating machine comprising: a coreless motor; a
power source part comprising a mounting part to which a
rechargeable battery is detachably mounted; a coupling part holding
the coreless motor at one end and holding the power source part at
the other end; a grip part extending in the longitudinal direction
of the coupling part, including a trigger operable by the operator
for controlling the drive of the coreless motor, and being
continued from or close to the power source part; and a handle
provided on the coupling part at a distance from the power source
part and grip part for being held by the operator, characterized in
that: the coreless motor includes a rotor and a stator; the rotor
includes a fixed output shaft; one of the rotor and stator
comprises a disc-shaped coil substrate including multiple nearly
annular coils arranged in the circumferential direction around the
output shaft when seen in the axial direction of the output shaft;
the other of the rotor and stator comprises a magnet generating a
magnetic flux passing through the coil substrate in the axial
direction of the output shaft; and the coreless motor is heavier
than the rechargeable battery mounted on the mounting part and the
gravity center of the electric operating machine is located on the
coreless motor side with respect to the handle.
27. The electric operating machine according to claim 26
characterized in that the coreless motor comprises an aluminum
alloy motor case housing the rotor.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electric operating
machine driven by a motor.
BACKGROUND ART
[0002] Recently, electric operating machines having a motor that
drives a rotary blade (for example, electric lawn mowers) attract
attention and are increasingly used. Using electric power as power
source, electric operating machines (lawn mowers) are quiet,
discharge no exhaust gas, and excellent in running cost.
[0003] For example, Patent Literature 1 discloses an electric lawn
mower having adjustable motor rotation speed. This electric lawn
mower has a converter to change the voltage applied to the motor so
as to change the motor rotation speed. Then, the blade rotation
speed can be changed according to the lawn grass to mow or the lawn
shape. Electric driving produces low driving noise.
CITATION LIST
Patent Literature
[0004] [PTL 1] [0005] Unexamined Japanese Patent Application KOKAI
Publication No. 2006-217843.
SUMMARY OF INVENTION
Technical Field
[0006] The electric lawn mower described in the Patent Literature 1
changes the rotation speed according to the battery output.
Therefore, when a battery of different output is mounted, the motor
does not rotate at a desired rotation speed, which is inconvenient.
Furthermore, batteries have different weights depending on their
output. When a battery of different output is mounted, the weight
balance of the electric lawn mower is changed, which may lower the
operability.
[0007] The present invention is made in view of the above problems
and a purpose of the present invention is to provide an electric
operating machine that can control the rotation speed of the motor
regardless of the output of the battery mounted and allow for
mounting/dismounting of batteries of different outputs.
Furthermore, another purpose of the present invention is to provide
an electric operating machine that is lightweight and well-balanced
and therefore excellent in operability.
Solution to Problem
[0008] In order to achieve the above purpose, the electric
operating machine according to the first aspect of the present
invention is:
[0009] an electric operating machine comprising:
[0010] a power source part including a battery mounting part for
mounting a battery;
[0011] and a voltage conversion part converting and outputting the
voltage input from the battery; and
[0012] an electric motor to which a work tool rotating in
association therewith is connected and that rotates upon
application of the voltage output from the voltage conversion part,
characterized in that
[0013] the power source part further includes a voltage measuring
part measuring the voltage applied to the electric motor and
outputting it to the voltage conversion part is further provided;
and
[0014] the voltage conversion part adjusts the output voltage so
that the voltage output from the voltage measuring part has a given
level.
[0015] For example, a battery of any voltage is mounted on or
dismounted from the battery mounting part.
[0016] The power source part of the electric operating machine may
further comprise an overcurrent protection part blocking the
current running toward the electric motor when the current running
toward the electric motor exceeds a given value.
[0017] Furthermore, the electric operating machine may further
comprise a first announcing part announcing that an overcurrent is
running when the current running toward the electric motor exceeds
a given value.
[0018] The power source part of the electric operating machine may
further comprise an overdischarge protection part blocking the
current running toward the electric motor when the voltage output
from the battery becomes lower than a predetermined voltage.
[0019] Furthermore, the electric operating machine may further
comprise a second announcing part announcing that the battery is
overly discharging when the voltage output from the battery becomes
lower than a predetermined voltage.
[0020] Furthermore, the power source part of the electric operating
machine may further comprise a voltage determination part
determining the predetermined voltage based on battery information
of the battery that is output from the battery.
[0021] Furthermore, the power source part of the electric operating
machine may further comprise a battery abnormality stop part
blocking the current running toward the electric motor according to
battery abnormality signals output from the battery when the
battery undergoes an abnormal event.
[0022] Furthermore, the battery abnormality stop part may block the
current running toward the electric motor until the battery is
dismounted from the battery mounting part since it receives the
battery abnormality signals.
[0023] Furthermore, the electric operating machine may further
comprise a third announcing part announcing that the battery
undergoes an abnormal event when the battery undergoes an abnormal
event.
[0024] Furthermore, it is possible that:
[0025] the electric operating machine further comprises a trigger,
and
[0026] the voltage measuring part applies to the voltage conversion
part a voltage according to the pulling rate of the trigger.
[0027] Furthermore, the power source part of the electric operating
machine may further comprise a trigger switch part blocking the
current running toward the electric motor when the pulling rate of
the trigger is lower than a given rate and allowing a current to
run through the electric motor when the pulling rate of the trigger
is equal to or higher than the given rate.
[0028] The power source part of the electric operating machine may
further comprise a main switch part blocking the current running
from the battery to the trigger switch part when it is turned OFF
and allowing the current when it is turned ON.
[0029] Furthermore, for example, the electric operating machine may
further comprise a first light emitting part emitting light when
the main switch part is ON.
[0030] Furthermore, the electric operating machine may further
comprise a remaining battery level display displaying the remaining
battery level according the voltage output from the battery.
[0031] Furthermore, the power source part of the electric operating
machine may comprise a constant voltage circuit outputting a
constant voltage from the voltage output from the battery.
[0032] Furthermore, the electric operating machine may further
comprise a sound reproducing part operating upon application of a
voltage output from the constant voltage circuit, decoding sound
data, and reproducing sound information.
[0033] Furthermore, the electric operating machine may further
comprise a radio operating upon application of a voltage output
from the constant voltage circuit and detecting sound information
in radio waves received by an antenna.
[0034] Furthermore, the electric operating machine may comprise a
speaker amplifying the sound information and making sound by a
voltage output from the constant voltage circuit.
[0035] Furthermore, it is preferable that the electric motor is a
coreless motor.
[0036] Furthermore, the electric operating machine may further
comprise a coupling part on whose one end the power source part is
arranged and on whose other end the electric motor is arranged.
[0037] Furthermore, the electric operating machine may comprise a
second light emitting part emitting light when the electric motor
is powered.
[0038] Furthermore, the electric operating machine may further
comprise a fourth announcing part announcing the power supply when
the electric motor is powered.
[0039] Furthermore, it is possible that:
[0040] the coreless motor includes a rotor and a stator;
[0041] the rotor includes a fixed output shaft;
[0042] one of the rotor and stator comprises a disc-shaped coil
substrate including multiple nearly annular coils arranged in the
circumferential direction around the output shaft when seen in the
axial direction of the output shaft; and
[0043] the other of the rotor and stator comprises a magnet
generating a magnetic flux passing through the coil substrate in
the axial direction of the output shaft.
[0044] Furthermore, in order to achieve the above purpose, the
electric operating machine according to the second aspect of the
present invention is:
[0045] an electric operating machine comprising:
[0046] a coreless motor;
[0047] a power source part comprising a mounting part to which a
lithium rechargeable battery is detachably mounted; and
[0048] a coupling part holding the coreless motor at one end and
holding the power source part at the other end, characterized in
that:
[0049] the coreless motor includes a rotor and a stator;
[0050] the rotor includes a fixed output shaft;
[0051] one of the rotor and stator comprises a disc-shaped coil
substrate including multiple nearly annular coils arranged in the
circumferential direction around the output shaft when seen in the
axial direction of the output shaft; and
[0052] the other of the rotor and stator comprises a magnet
generating a magnetic flux passing through the coil substrate in
the axial direction of the output shaft.
[0053] Furthermore, in order to achieve the above purpose, the
electric operating machine according to the third aspect of the
present invention is:
[0054] an electric operating machine comprising:
[0055] a coreless motor;
[0056] a power source part comprising a mounting part to which a
rechargeable battery is detachably mounted;
[0057] a coupling part holding the coreless motor at one end and
holding the power source part at the other end;
[0058] a grip part extending in the longitudinal direction of the
coupling part, including a trigger operable by the operator for
controlling the drive of the coreless motor, and being continued
from or close to the power source part; and
[0059] a handle provided on the coupling part at a distance from
the power source part and grip part for being held by the operator,
characterized in that:
[0060] the coreless motor includes a rotor and a stator;
[0061] the rotor includes a fixed output shaft;
[0062] one of the rotor and stator comprises a disc-shaped coil
substrate including multiple nearly annular coils arranged in the
circumferential direction around the output shaft when seen in the
axial direction of the output shaft;
[0063] the other of the rotor and stator comprises a magnet
generating a magnetic flux passing through the coil substrate in
the axial direction of the output shaft; and
[0064] the coreless motor is heavier than the rechargeable battery
mounted on the mounting part and the gravity center of the electric
operating machine is located on the coreless motor side with
respect to the handle.
[0065] Furthermore, the coreless motor may comprise an aluminum
alloy motor case housing the rotor.
Advantageous Effects of Invention
[0066] The electric operating machine according to the first aspect
of the present invention can control the rotation speed of the
motor regardless of the battery output and allow for
mounting/dismounting of batteries of different outputs.
Furthermore, the electric operating machines according to the
second and third aspects of the present invention are lightweight
and well-balanced and therefore excellent in operability.
BRIEF DESCRIPTION OF DRAWINGS
[0067] [FIG. 1] An illustration showing the appearance of an
electric operating machine according to an embodiment of the
present invention;
[0068] [FIG. 2] An enlarged view of the operation part of the
electric operating machine in FIG. 1;
[0069] [FIG. 3] A cross-sectional view of the drive part of the
electric operating machine in FIG. 1;
[0070] [FIG. 4] An exploded cross-sectional view of the rotor of
the electric operating machine in FIG. 1;
[0071] [FIG. 5] A top view of the rotor in FIG. 4;
[0072] [FIG. 6] A top view of the coil substrate part of the rotor
in FIG. 4;
[0073] [FIG. 7] An illustration showing the connection in the
operation part of the electric operating machine in FIG. 1;
[0074] [FIG. 8] An illustration showing a modification example of
the electric operating machine in FIG. 1;
[0075] [FIG. 9]
[0076] An illustration showing the connection in the operation part
of the electric operating machine in FIG. 8;
[0077] [FIG. 10] A block diagram of the power supply circuit
installed in the operation part of the electric operating machine
in FIG. 1;
[0078] [FIG. 11] A circuit diagram of a specific example of the
booster circuit and speed adjustment part of the power supply
circuit in FIG. 10;
[0079] [FIG. 12] A circuit diagram of a specific example of the
current detection part of the power supply circuit in FIG. 10;
[0080] [FIG. 13] A circuit diagram of a specific example of the
battery voltage detection part of the power supply circuit in FIG.
10;
[0081] [FIG. 14] An illustration showing a modification example of
the electric operating machine in FIG. 1;
[0082] [FIG. 15] An illustration showing the electric operating
machine in FIG. 14 being held;
[0083] [FIG. 16] An illustration showing a belt for holding the
electric operating machine in FIG. 14; and
[0084] [FIG. 17] An illustration showing the working manner with
the electric operating machine in FIG. 14.
DESCRIPTION OF EMBODIMENTS
[0085] The electric operating machine according to an embodiment of
the present invention will be described hereafter with reference to
the drawings. Here, the electric operating machine according to
this embodiment is an electric lawn mower 1 including a motor that
drives a rotary blade.
[0086] As shown in FIG. 1, an electric lawn mower 1 includes an
operation part 10, a coupling part 20 held at the forefront of the
operation part (power source part) 10 at one end, a drive part 30
held at the other end of the coupling part 20, and a blade (work
tool) 39 coupled to the drive part 30. A battery mounting part 11
is provided at the rear end of the operation part 10. A main switch
12, a remaining battery level display 14, and a main LED (light
emitting diode) 15 are provided on the top surface of the operation
part 10. A power supply circuit 16 is provided inside the operation
part 10. A D-shaped handle 21 is provided on the coupling part 20
at a distance from the operation part 10 and a grip 22 with a
trigger 13 is provided next to the D-shaped handle 21. A running
indicator LED 40 is provided on the top surface of the drive part
30.
[0087] The battery mounting part 11 is used to mount a battery 50.
The battery mounting part 11 supplies the output of the battery 50
to the power supply circuit 16.
[0088] The main switch 12 is a switch turning ON/OFF the power
supply circuit 16. When the main switch 12 is turned ON, the power
supply circuit 16 is put in the standby mode. The power supply
circuit 16 is not activated and supplies no electric power while
the main switch 12 is OFF.
[0089] The trigger 13 is a switch controlling the value of electric
power supplied to the drive part 30 from the power supply circuit
16. When the trigger 13 is pulled in the standby mode while the
main switch 12 is ON, the electric power according to the pulling
rate of the trigger 13 is supplied to the drive part 30 from the
power supply circuit 16.
[0090] The remaining battery level display 14 is, for example, a
liquid crystal screen that changes display according to the output
of the battery 50. Checking on the screen displayed by the
remaining battery level display 14, the user of the electric lawn
mower 1 can know the approximate remaining operation time.
[0091] The main LED 15 is a first light emitting part emitting
light when the main switch 12 is turned ON. Since the main LED 15
emits light when the main switch 12 is turned on, the operator can
easily confirm that the main switch 12 is ON/OFF.
[0092] The power supply circuit 16 converts the voltage output from
the battery 50 to a voltage of a value corresponding to the pulling
rate of the trigger 13 regardless of the output voltage magnitude
from the battery 50 and outputs it. The power supply circuit 16
further include a function of protecting the battery 50 and drive
part 30 against overcurrent and overvoltage, imposing mandatory OFF
on the output according to the output voltage of the battery 50 or
the value of current supplied to the drive part 30. Details of
operation and a specific circuit of the power supply circuit 16
will be described later.
[0093] Since the power supply circuit 16 applies to the drive part
30 a voltage of a value according to the pulling rate of the
trigger 13 regardless of the output voltage of the battery 50, the
type of the battery 50 does not matter. This embodiment is
explained as a case in which the battery 50 is, for example, a
lithium ion rechargeable battery. The battery 50 comprises a
substrate, multiple battery cells provided on the substrate, and
plus and minus terminals provided on the substrate. The battery 50
also comprises an LD terminal. When a circuit provided on the
substrate of the battery 50 detects overdischarge from the battery
cells, abnormal signals are output from the LD terminal. The
battery 50 also comprises an ID terminal. Battery information such
as specification of the battery 50 stored in the memory on the
substrate of the battery 50 is output from the ID terminal. The
battery 50 applies a voltage between the plus and minus terminals
to the power supply circuit 16.
[0094] As described later, the electric lawn mower 1 further
comprises a speaker, a radio, and a sound reproducing device, which
are driven by the electric power supplied from the operation part
10.
[0095] The coupling part 20 includes a hollow tube made of a
lightweight, rigid material such as aluminum alloy and reinforced
plastic. The coupling part 20 mechanically connects the operation
part 10 and drive part 30 and supplies the electric power output
from the power supply circuit 16 to the drive part 30 via a
conductive wire running through the inside thereof.
[0096] Holding the D-shaped handle 21 and grip 22, the user uses
the electric lawn mower 1. The operation part 10 and drive part 30
are provided on the coupling part 20 at a distance as described
above; therefore, the gravity center of the electric lawn mower 1
is away from the operation part 10. The user receives a proper
weight, improving the operability.
[0097] The drive part 30 rotates the attached blade 39 with the
input electric power. The drive part 30 consists of, for example, a
coreless motor.
[0098] The drive part 30 consisting of a coreless motor assures a
higher level of quietness. Furthermore, a lithium ion battery is
used to drive the coreless motor; a lightweight, low power
consumption electric lawn mower 1 having extended operation time
can be constructed. Furthermore, using a booster circuit 300 as
described later, sufficiently high rotation speed operation is
available with a small capacity battery.
[0099] The running indicator LED 40 is a second light emitting part
emitting light while the drive part 30 is powered. The running
indicator LED 40 consists of, for example, an organic EL. The
running indicator LED 40 emits light while the drive part 30 is
powered. Then, the running indicator LED 40 emits light even if the
drive part 30 does not rotate because of, for example, shortage in
torque. In this way, the user can know whether or not the drive
part 30 is powered from the running indicator LED 40. Furthermore,
when the user cannot know whether or not the drive part 30 is
driven from the driving sound of the drive part 30, the running
indicator LED 40 allows the user to know whether or not the drive
part 30 is driven.
[0100] As shown in FIG. 2, the battery 50 is detachably fitted in
the battery mounting part 11 in the direction from the top surface
to bottom surface. With the battery 50 being fitted in the battery
mounting part 11, the output terminals of the battery 50 are
connected to the input terminals of the operation part 10.
[0101] The drive part 30 consisting of a coreless motor primarily
comprises, as shown in FIG. 3, a motor case 29, a coil substrate
31, a central shaft (output shaft) 32, a brush 33, a commutator 34,
an upper yoke 35, a lower yoke 36, a magnet part 37, and a brush
cap 38.
[0102] The motor case 29 immobilizes the upper yoke 35, lower yoke
36, and brush cap 38. The coil substrate 31 is secured by the
central shaft 32 passing through the center of the motor case 29.
The commutator 34 is fixed to one surface of the coil substrate 31.
The upper yoke 35 is fixed to the motor case 29 at a not-shown
position. The lower yoke 36 is fitted in and fixed to the motor
case 29. The magnet part 37 is fixed to one surface of the lower
yoke 36. The brush cap 38 is fixed to the motor case 29. The brush
33 is supported and biased toward the commutator 34 by a spring
that the motor case 29 includes.
[0103] The motor case 29 is a hollow case made of a lightweight,
rigid material such as aluminum alloy and reinforced plastic. The
coil substrate 31 is a nearly disc-shaped plate on which multiple
coils are arranged.
[0104] Passing through the coil substrate 31 and commutator 34, the
central shaft 32 is secured to the coil substrate 31. The coil
substrate 31 and commutator 34 rotates as one piece as the central
shaft 32 rotates. The electric power supplied from the operation
part 10 via a conductive wire passing through the inside of the
coupling part 20 is supplied to the coil substrate 31 via the brush
33. The commutator 34 consists of commutator segments and
insulating segments connected to the coil substrate 31 and
alternately arranged in a circle around the central shaft. The
commutator 34 allows only one direction of current supplied from
the brush 33 to run to the coil substrate 31. The magnet part 37
has planar magnets magnetized in the axial direction and arranged
in the circumferential direction, forming a magnetic circuit via
the upper and lower yokes 35 and 36.
[0105] As shown in FIG. 4, the rotor of the coreless motor
comprises a central shaft 32, a flange 132, and, from the top in
FIG. 4, a commutator 34 and a coil substrate 31 consisting of five
coil substrate parts 131. The commutator 34 and coil substrate 31
are each a printed-wiring board composed of an insulator substrate
and a conductor pattern.
[0106] As shown in FIG. 5, a conductor pattern for commutator
segments 134 making contact with the brush 33 is formed on the top
surface of the commutator 34. The conductor pattern has an annular
form around the central shaft 32 seen in the axial direction of the
central shaft 32. Each commutator segment 134 has a through-hole
penetrating the commutator 34 at the outer end. A conductor pattern
on the top surface of the coil substrate part 131 provides multiple
coil segments 131a arranged in a radial pattern about the central
shaft 32 and bent in given directions about the axis of the central
shaft 32.
[0107] As shown in FIG. 6, each coil segment 131c is connected to
the corresponding commutator segment 134 via a through-hole at the
inner end. Each coil segment 131c has multiple through-holes
penetrating the coil substrate part 131 at the outer end.
[0108] A conductor pattern on the bottom surface of the coil
substrate part 131 is nearly equal to the coil segments 131a and
131c shown in FIGS. 5 and 6 and provides multiple not-shown coil
segments arranged in a radial pattern about the central shaft 32.
The outer end of each not-shown coil segment is connected to the
corresponding coil segment on the top surface via solder filled in
the through-hole. The inner end of each not-shown coil segment is
connected to the corresponding commutator segment 134 of the
commutator 34 via solder filled in the through-hole. Then, the
multiple coil segments 131a and 131c and multiple not-shown coil
segments in the coil region constitute multiple coils in the form
of a nearly horizontal U-shape (an example of a nearly annular
form) seen in the axial direction of the central shaft 32. The
multiple coils are arranged in the circumferential direction around
the central shaft 32. The ends of the coils are connected to the
corresponding commutator segments 134 of the commutator 34.
[0109] The conductor pattern for the commutator segments 134 of the
commutator 34 has a thickness larger than the coil segments of the
coil substrate parts in order to curb damage due to abrasion by the
brush 33. Not-shown insulating layers are interposed between the
commutator 34 and coil substrate 31 and between multiple coil
substrate parts 131.
[0110] The magnetic flux of the magnetic circuit formed via the
upper and lower yokes 35 and 36 passes through the coils of the
coil substrate 31 in the axial direction of the central shaft 32.
The motor case 29 housing the magnet part 37 and upper and lower
yokes 35 and 36 constitutes the stator of the coreless motor. The
central shaft 32 and coil substrate 31 secured to the central shaft
32 as the rotor and the magnet part 37, upper and lower yokes 35
and 36, and brush 33 as the stator constitute the direct current
rectifier motor of the coreless motor. Here, the magnet part 37 and
upper and lower yokes 35 and 36 constitute a magnetic flux
generation means forming a magnetic circuit. The magnetic flux
generation means is not restricted to this structure as long as the
magnetic flux passes through the coils of the coil substrate 31 in
the axial direction of the central shaft 32. For example, the
magnetic flux generation means can consist of multiple permanent
magnets, electromagnets, or only coils.
[0111] The blade 39 rotates in conjunction with the central shaft
32 rotates. As the blade 39 rotates, the target is mowed.
[0112] The connection between the operation part 10 and trigger 13
of the electric lawn mower 1 in FIG. 1 is shown in detail in FIG.
7.
[0113] The grip 22 is formed integrally with the operation part 10
and provided along the periphery of the coupling part 20. The grip
22 is provided with a rotation shaft 25, to which the trigger 13 is
coupled. A wire 24 is connected to the trigger 13. The trigger 13
is coupled to a variable speed switch 26 provided in the operation
part 10 via the wire 24. The grip 22 may be close to the operation
part 10 with a space therebetween, which is regarded as equivalent
to a situation where the grip 22 is next to the operation part
10.
[0114] When the trigger 13 is pulled, the wire 24 is tugged about
the rotation shaft 25. The wire 24 transfers the pulling rate of
the trigger 13 to the variable speed switch 26. The variable speed
switch 26 supplies the pulling rate of the trigger 13 to the power
supply circuit 16. The power supply circuit 16 adjusts the output
voltage according to the pulling rate of the trigger 13.
[0115] The electric lawn mower 1 can have a U-shaped handle 23 as
shown in FIG. 8 in place of the D-shaped handle 21. In such a case,
the U-shaped handle 23 is provided on the coupling part 20 at a
distance from the operation part 10 and the trigger 13 is provided
at one end of the U-shaped handle 23.
[0116] The U-shaped handle 23 consists of a U-shaped hollow pipe
and has grips 22 at the ends. The trigger 13 is provided to one of
the grips 22.
[0117] As shown in FIG. 9, the U-shaped handle 23 comprises grips
22 at the ends, a rotation shaft 25 at one of the grips 22, a
trigger 13 coupled to the rotation shaft 25, a wire 24 coupling the
variable speed switch 26 in the operation part 10 to the trigger
13, and a resin cover 27 covering the wire 24.
[0118] When the trigger 13 is pulled, the wire 24 is tugged about
the rotation shaft 25. The wire 24 transfers the pulling rate of
the trigger 13 to the variable speed switch 26. The variable speed
switch 26 supplies the pulling rate of the trigger 13 to the power
supply circuit 16. The power supply circuit 16 adjusts the output
voltage according to the pulling rate of the trigger 13. The resin
cover 27 protects the wire 24 from mechanical stress.
[0119] The power supply circuit 16 will be described hereafter with
reference to FIGS. 10 to 13.
[0120] The power supply circuit 16 comprises, as shown in FIG. 10,
input terminals I1, I2, I3, and I4, a main switch circuit 100, a
trigger switch circuit 200, a booster circuit 300, a speed
adjustment circuit (speed adjustment part, voltage measuring part)
400, a control circuit 500, a current detection circuit 600, a
battery voltage detection circuit 700, a battery abnormality
detection circuit 800, a constant voltage circuit 900, and output
terminals O1 and O2.
[0121] After the battery 50 is mounted on the battery mounting part
11, the input terminal I1 is connected to the plus terminal (+) of
the battery 50; the input terminal I2, to the minus terminal (-) of
the battery 50; the input terminal I3, to the LD terminal of the
battery 50; and the input terminal I4, to the ID terminal of the
battery 50. On the other hand, the running indicator LED 40 and
drive part 30 are series-connected between the output terminals O1
and O2.
[0122] The input terminal I1 is connected to the main switch
circuit 100. The input terminal I2 is grounded. The input terminal
I3 is connected to the battery abnormality detection circuit 800.
The input terminal I4 is connected to the control circuit 500.
[0123] The output of the main switch circuit 100 is supplied to the
trigger switch circuit 200, battery voltage detection circuit 700,
constant voltage circuit 900, and anode of the main LED 15. The
cathode of the main LED 15 is connected to the remaining battery
level display 14. The main switch circuit 100 consists of, for
example, a switch activated as the main switch 12 is turned ON and
a self-arc extinguishing element such as IGBT (insulated gate
bipolar transistor) and MOSFET (metal oxide semiconductor field
effect transistor).
[0124] The trigger switch circuit 200 is connected between the main
switch circuit 100 and booster circuit 300. The trigger switch
circuit 200 consists of, for example, a switch activated as the
trigger 13 is pulled and a self-arc extinguishing element such as
IGBT and MOSFET. [0076] The booster circuit 300 is connected
between the trigger switch circuit 200 and output terminal O1. The
booster circuit 300 is, for example, a flyback booster circuit.
[0077]
[0125] The speed adjustment circuit 400 is so connected as to
provide feedback on the output of the booster circuit 300 to the
booster circuit 300. The speed adjustment circuit 400 consists of,
for example, a voltage dividing resistor and a variable resistor
having a resistance varied according to the pulling rate of the
trigger 13.
[0126] The control circuit 500 receives the output of the constant
voltage circuit 900, output of the current detection circuit 600,
output of the battery voltage detection circuit 700, and the input
to the input terminal I4. The output of the control circuit 500 is
supplied to the main switch circuit 100, trigger switch circuit
200, and speaker 910. The control circuit 500 is, for example, a
microcomputer.
[0127] The current detection circuit 600 is connected to the output
terminal O2 at one terminal and grounded at the other terminal. The
current detection circuit 600 is, for example, an ampere meter.
[0128] The battery voltage detection circuit 700 is connected to
the output of the main switch circuit 100 as described above. The
output of the battery voltage detection circuit 700 is supplied to
the control circuit 500.
[0129] The output of the battery abnormality detection circuit 800
is supplied to the main switch circuit 100. The battery voltage
detection circuit 700 is, for example, an off-latch circuit.
[0130] The output of the constant voltage circuit 900 is supplied
to the control circuit 500, speaker 910, sound reproducing circuit
920, and radio 930. The constant voltage circuit 900 is a circuit
outputting a constant value voltage from the voltage output from
the battery 50 and consists of, for example, a three-terminal
regulator and a smoothing capacitor.
[0131] The power supply circuit 16 having the above-described
structure is driven by a voltage applied between the input
terminals I1 and I2.
[0132] After the battery 50 is mounted on the battery mounting part
11, electric power is supplied from the battery 50 to the main
switch circuit 100.
[0133] The main switch circuit 100 is a switch associated with
ON/OFF of the main switch 12. The main switch circuit 100 is turned
ON when the main switch 12 is turned ON. The main switch circuit
100 is turned OFF when the main switch 12 is turned OFF. The main
switch circuit 100 is further turned ON/OFF by the control circuit
500 while the main switch 12 is ON.
[0134] While the main switch 12 is ON, the main switch circuit 100
supplies the electric power output from the battery 50 to the
trigger switch circuit 200, constant voltage circuit 900, and
remaining battery level display 14. While the main switch 12 is
OFF, the main switch circuit 100 blocks the electric power supplied
from the battery 50.
[0135] The trigger witch circuit 200 is a switch associated with
the trigger 13. The trigger switch circuit 200 is turned ON when
the pulling rate of the trigger 13 is equal to or higher than a
given value. The trigger switch circuit 200 is further turned
ON/OFF by the control circuit 500. While the trigger switch circuit
200 is ON, the trigger switch circuit 200 supplies the electric
power supplied from the main switch circuit 100 to the booster
circuit 300. While the trigger switch circuit 200 is OFF, the
trigger switch circuit 200 blocks the electric power.
[0136] The booster circuit 300 boosts the electric power supplied
from the trigger switch circuit 200 and outputs it from the output
terminal O1. The output of the booster circuit 300 is adjusted by
the speed adjustment circuit 400. The booster circuit 300 adjusts
the output so that the voltage input from the speed adjustment
circuit 400 always stays constant. The voltage boosted by the
booster circuit 300 is applied to the drive part 30 connected to
the output terminals O1 and O2.
[0137] The speed adjustment circuit 400 is a circuit measuring the
voltage applied to the motor and adjusting the output of the
booster circuit 300 according to the pulling rate of the trigger
13. The speed adjustment circuit 400 provides feedback on the
output of the booster circuit 300, whereby the booster circuit 30
outputs a voltage of a target value. The speed adjustment circuit
400 supplies the voltage divided between the voltage dividing
resistor and variable resistor to the booster circuit 300.
[0138] The current detection circuit 600 detects the current
running toward the drive part 30 and outputs it to the control
circuit 500. The battery voltage detection circuit 700 detects the
voltage output from the battery 50 and outputs it to the control
circuit 500.
[0139] The control circuit 500 mandatorily turns OFF the main
switch circuit 100 or trigger switch circuit 200, for example, when
the current running toward the drive part 30 exceeds the rated
value of the drive part 30 or when the voltage output from the
battery 50 becomes lower than a given value. The control circuit
500 executes programs stored in the memory in advance so as to turn
OFF the main switch circuit 100 or trigger switch circuit 200
according to the current running toward the drive part 30, which is
detected by the current detection circuit 600, and the voltage
output from the battery 50, which is detected by the battery
voltage circuit 700. Furthermore, when the control circuit 500
detects no electric power being supplied to the drive part 30 for a
given period of time while the main switch circuit 100 is ON, the
control circuit 500 automatically turns OFF the main switch circuit
100. Furthermore, the control circuit 500 receives battery
information from the ID terminal via the input terminal 4.
Receiving battery information, the control circuit 500 makes
reference to a table stored in the internal memory in advance and
reads the voltage at which the battery starts overly discharging
based on the battery information. For example, the control circuit
500 obtains an overdischarge voltage of 8 V if the battery
information includes a rated voltage of 14.4 V and an overdischarge
voltage of 10 V if the battery information includes a rated voltage
of 18 V. The control circuit 500 automatically turns OFF the main
switch circuit 100 when the output voltage of the battery 50
becomes lower than the overdischarge voltage. The overdischarge
voltage is a reference voltage where the battery 50 reaches a state
of overdischarge when the actual output voltage of the batter 50
constantly decreases. Also, the overdischarge voltage is larger
than this output voltage by a predetermined value. When the output
voltage of the battery 50 falls below the overdischarge voltage,
the main switch circuit 100 is automatically turned OFF as
overdischarge occurs shortly thereafter.
[0140] The battery abnormality detection circuit 800 turns OFF the
main switch circuit 100 when it receives signals from the LD
terminal and mandatorily keeps the main switch circuit 100 OFF
until it receives no input from the LD terminal or the battery 50
is dismounted.
[0141] The constant voltage circuit 900 is a circuit outputting a
voltage of a constant value from the voltage output from the
battery 50. The output of the constant voltage circuit 900 is
supplied to the control circuit 500 and also to the speaker 910,
sound reproducing circuit 920, and radio 930.
[0142] The speaker 910 makes sound based on input sound
information.
[0143] Furthermore, when the current detection circuit 600 detects
more than a given value of current running toward the drive part
30, the control circuit 500 instructs the speaker 910 to make sound
for the case of overcurrent. Similarly, when the battery 50 starts
overly discharging, the speaker 910 announces the overdischarge.
When the battery 50 undergoes an abnormal event, the speaker 910
announces that the battery 50 undergoes an abnormal event.
[0144] The sound reproducing circuit 920 operates on the output of
the constant voltage circuit 900. The sound reproducing circuit 920
decodes sound data such as music data stored in the internal memory
and outputs them to the speaker 910. The radio 930 has an antenna.
The radio 930 tunes the antenna properties and receives radio waves
of a particular frequency, detects sound information superimposed
on carrier waves from the received radio waves, and outputs the
detected sound information to the speaker. These operations are
performed on the output of the constant voltage circuit 900;
therefore, they are activated as the main switch circuit 100 is
turned ON.
[0145] An example of a specific circuit of the booster circuit 300
will be described hereafter.
[0146] As shown in FIG. 11, the booster circuit 300 consists of,
for example, a smoothing circuit 301, a booster circuit 310, a
rectifier diode 320, and a smoothing capacitor 330. The speed
adjustment circuit 400 consists of a series circuit composed of a
voltage dividing resistor 410, a voltage dividing resistor 420, a
variable resistor 430.
[0147] The smoothing capacitor 301 is parallel-connected between
the trigger switch circuit 200 and booster circuit 310. The booster
circuit 310 is series-connected between the trigger switch circuit
200 and rectifier diode 320. The rectifier diode 320 is
series-connected between the booster circuit 310 and output
terminal O1. The smoothing capacitor 330 is parallel-connected
between the rectifier diode 320 and output terminal O1.
[0148] The speed adjustment circuit 400 is connected between the
output terminals O1 and 02. The output of the speed adjustment
circuit 400 is connected to the booster circuit 310. In the speed
adjustment circuit 400, the voltage dividing resistors 410 and 420
are series-connected and the variable resistor 430 is further
series-connected thereto.
[0149] The smoothing capacitor 301 removes extra vibration of the
voltage supplied from the trigger switch circuit 200 so as to
smooth the waveform.
[0150] The booster circuit 310 is a booster chopper circuit
consisting of, for example, an FET (field effect transistor) 311, a
switching IC (integrated circuit) 312, and a choke coil 313.
[0151] With the switching IC 312 repeatedly turning ON/OFF the FET
311, the booster circuit 310 boosts the input voltage by means of
the flyback effect of the choke coil 313 and outputs the boosted
voltage.
[0152] The FET 311 is turned ON when a voltage equal to or higher
than a threshold voltage is applied to the gate terminal by the
switching IC 312, allowing a current to run between the source and
drain terminals. The FET 311 is turned OFF when a voltage lower
than the threshold voltage is applied to the gate terminal,
allowing no current to run between the source and drain
terminals.
[0153] The switching IC 312 applies a high level of voltage equal
to or higher than a threshold voltage of the FET 311 or a low level
of voltage lower than the threshold voltage to the gate terminal of
the FET 311 to turn ON/OFF the FET 311 according to the voltage
input from the speed adjustment circuit 400. The switching IC 312
adjusts the ON/OFF switching frequency of the voltage applied to
the gate terminal of the FET 311 so that the voltage input from the
speed adjustment circuit 400 has a target value. For example, the
switching IC 312 increases the ON/OFF switching speed of the FET
311 when the voltage input from the speed adjustment circuit 400 is
lower than a target value, and decreases the ON/OFF switching speed
of the FET 311 when the voltage input from the speed adjustment
circuit 400 is higher than the target value.
[0154] The choke coil 313 yields flyback effect as the ON/OFF
switching of the FET 311 occurs. The flyback effect causes the
voltage between the terminals of the choke coil 313 to rise.
[0155] The rectifier diode 320 rectifies the output of the booster
circuit 310. The smoothing capacitor 330 removes extra vibration of
the voltage rectified by the rectifier diode 320 so as to smooth
the waveform.
[0156] The voltage divided between the voltage dividing resistor
410 and the voltage dividing resistor 420 and variable resistor 430
is supplied to the switching IC 312.
[0157] The variable resistor 430 has a resistance varied according
to the pulling rate of the trigger 13. The resistance of the
variable resistor 430 drops as the pulling rate of the trigger 13
is increased and rises as the pulling rate of the trigger 13 is
decreased.
[0158] For example, as the user increases the pulling rate of the
trigger 13, the resistance of the variable resistance 430 drops and
the voltage applied to the switching IC 312 from the speed
adjustment circuit 400 drops. Then, the switching IC 312 shortens
the switching cycle of the FET 311. As the cycle of switching
ON/OFF the FET 311 is shortened, the peak value of the voltage
between the terminals of the choke coil 313 rises and the voltage
supplied to the switching IC 312 from the speed adjustment circuit
400 rises.
[0159] As described above, the speed adjustment circuit 400
provides feedback on the output of the booster circuit 300, whereby
the booster circuit 300 adjusts the output so that the voltage
input from the speed adjustment circuit 400 always stays
constant.
[0160] The above operation is performed also when the voltage
supplied to the booster circuit 300 from the trigger switch circuit
200 varies because of the decrease in the output of the battery 50,
the replacement to another battery from the battery 50, or the
like. For example, when the output of the battery 50 drops, the
voltage output from the booster circuit 300 accordingly drops. As
the output of the booster circuit 300 drops, the voltage supplied
to the booster circuit 300 from the speed adjustment circuit 400
drops. Then, the booster circuit 300 further raises the output
voltage. The output voltage of the booster circuit 300 is adjusted
until the voltage input from the speed adjustment circuit 400 has a
target value.
[0161] In this way, the booster circuit 300 and speed adjustment
circuit 400 allow the electric lawn mower 1 to operate at a target
rotation speed regardless of different output from the battery
50.
[0162] Incidentally, the voltage dividing resistors 410 and 420 and
variable resistor 430 have relatively high impedances compared with
the drive part 30. Therefore, the speed adjustment circuit 400
consumes almost no electric power.
[0163] The control circuit 500, current detection circuit 600,
voltage detection circuit 700, and battery abnormality detection
circuit 800 of the power supply circuit 16 will be described
hereafter with reference to FIGS. 12 and 13.
[0164] As shown in FIG. 12, the current detection circuit 600
consists of, for example, a current detection resistor 610, an
operational amplifier 620, a grounding resistor 621, a feedback
resistor 622, and a current limiting resistor 630.
[0165] The current detection resistor 610 connects the booster
circuit 300, speed adjustment circuit 400, and drive part 30 and
the ground. The terminal of the current detection resistor 610 that
is not grounded is connected to the + terminal of the operational
amplifier 620. The output of the operational amplifier 620 is
connected to its own - (minus) terminal via the feedback resistor
622 and further grounded via the grounding resistor 621.
Furthermore, the output of the operational amplifier 620 is
supplied to the control circuit 500 via the current limiting
resistor 630.
[0166] The current detection resistor 610 detects the total current
running toward the booster circuit 300, speed adjustment circuit
400, and drive part 30. However, since the current running from the
booster circuit 300 and speed adjustment circuit 400 to the ground
is much smaller in quantity than the current running toward the
drive part 30, the total current running toward the booster circuit
300, speed adjustment circuit 400, and drive part 30 is nearly
equal in quantity to the current running toward the drive part
30.
[0167] The operational amplifier 620, grounding resistor 621, and
feedback resistor 622 form a noninverting amplifying circuit. The +
terminal of the operational terminal 620 serves as the noninverting
input terminal (+) and the - terminal of the operational terminal
620 serves as the noninverting input terminal (-). The noninverting
input terminal (+) of the operational terminal 620 receives the
voltage between the current detection resistor 610 and ground. The
noninverting input terminal (-) of the operational terminal 620 is
grounded via the grounding resistor 621 and receives negative
feedback on the output of the operational terminal 620 from the
feedback resistor 622. The amplified output is limited in current
by the current limiting resistor 630 and supplied to the control
circuit 500.
[0168] Receiving a signal having a voltage equal to or higher than
a threshold from the current detection circuit 600, the control
circuit 500 mandatorily turns OFF the trigger switch circuit 200.
Once the trigger switch circuit 200 is mandatorily turned OFF, the
electric power supplied from the main switch circuit 100 is not
supplied to the booster circuit 300 even if the trigger 13 is
pulled. Here, the current detection resistor 610, grounding
resistor 621, feedback resistor 622, and current limiting resistor
630 are selected so that the control circuit 500 receives a signal
having a voltage equal to or higher than a threshold when the
detected current exceeds a nearly rated value of the drive part 30
(for example, 15 A).
[0169] As described above, when the current running toward the
drive part 30 is equal to or higher than a given value, the control
circuit 500 mandatorily turns OFF the trigger switch circuit 200.
However, even though the trigger switch circuit 200 is turned OFF,
the main switch circuit 100 stays ON and the electric power is
supplied to the constant voltage circuit 900.
[0170] As described above, when the current detection circuit 600
detects the current running toward the drive part 30 having an
abnormal value, the control circuit 500 mandatorily turns OFF the
trigger switch circuit 200 to stop the power supply to the drive
part 30.
[0171] Furthermore, when the battery voltage detection circuit 700
detects the output voltage of the battery 50 being equal to or
lower than a given value, the control circuit 500 mandatorily turns
OFF the main switch circuit 100. The battery voltage detection
circuit 700 consists of, for example, as shown in FIG. 13, a series
circuit composed of voltage dividing resistors 710 and 720.
[0172] The voltage dividing resistor 710 is connected to the output
of the main switch circuit 100 at one end and to one end of the
voltage dividing resistor 720 at the other end. The other end of
the voltage dividing resistor 720 is grounded.
[0173] The control circuit 500 receives the voltage applied to the
voltage dividing resistor 720. When the received voltage becomes
equal to or lower than a voltage at which the battery 50 starts
overly discharging, the control circuit 500 mandatorily turns OFF
the main switch circuit 100.
[0174] As described above, the battery voltage detection circuit
700 measures the voltage output from the main switch circuit 100 so
as to measure the voltage output from the battery 50 and supplies
it to the control circuit 500. When the output voltage of the
battery 50 that is detected by the battery voltage detection
circuit 700 has an abnormal value, the control circuit 500
mandatorily turns OFF the main switch circuit 100 to stop the
output of the battery 50. In this way, overdischarge of the battery
50 is prevented.
[0175] Furthermore, when there is no voltage input from the current
detection circuit 600 for more than a given period of time stored
in the memory while there is voltage input from the battery voltage
detection circuit 700, the control circuit 500 mandatorily and
automatically turns OFF the main switch circuit 100. In this way,
the electric lawn mower 1 is automatically powered off when it is
left with the main switch circuit kept ON.
[0176] Furthermore, when the circuit provided on the substrate of
the battery 50 detects any abnormal event with the battery cells,
the battery abnormality detection circuit 800 automatically stops
the power supply from the battery 50.
[0177] As described above, the present embodiment drives the motor
of an electric lawn mower with fixed (stable) output regardless of
the type and output of the power source. Furthermore, the power
source is automatically turned off when the battery starts overly
discharging, a current exceeding the rated value of the motor
occurs, or the battery undergoes some abnormal event.
[0178] The present invention is not confined to the above
embodiment and has various modifications and applications.
[0179] For example, in the above embodiment, the coupling part 20
is a cylindrical pipe. The coupling part 20 is not restricted in
shape to the above-described embodiment as long as it has an
electric wire inside for supplying electric power from the
operation part 10 to the drive part 30. The coupling part 20 can
be, for example, arc-shaped or made of a shape-changeable flexible
material.
[0180] Furthermore, in the above embodiment, the remaining battery
level display 14 is a liquid crystal screen. The remaining battery
level display 14 is not necessarily a liquid crystal screen as long
as the remaining battery level is known. For example, the voltage
output from the battery 50 can be applied directly or via a voltage
divider to a light emitting diode that widely changes brightness
according to the applied voltage. In such a case, the brightness of
the light emitting diode is proportional to the output of the
battery 50. The brightness of the light emitting diode drops as the
electric power of the battery 50 diminishes and the voltage drops.
Checking on the brightness of the light emitting diode, the
remaining level of the battery 50 can be known by the user.
[0181] Furthermore, in the above embodiment, the running indicator
LED 40 indicates whether or not the drive part 30 is in operation.
It is not necessarily a light emitter. For example, sound from the
speaker 910 can be used to inform the operator. Alternatively,
another speaker for announcing the operation can be provided.
[0182] Furthermore, in the above embodiment, the control circuit
500 controls the ON/OFF of the main switch circuit 100 and trigger
switch circuit 200 upon overdischarge and overcurrent. It is not
necessarily the control circuit 500 that is in charge of the
control. For example, the following structure can be used when the
current running toward the drive part 30 exceeds a given value. A
GTO (gate turnoff thyristor) is series-connected between the
battery 50 and drive part 30 and a Zener diode having a breakdown
voltage nearly equal to the threshold voltage of this self-arc
extinguishing element is connected to the gate of the
[0183] GTO so that a voltage exceeding the breakdown voltage is
applied to the Zener diode when a given value of current runs
through the drive part 30. In this way, the current runs into the
gate of the GTO and the GTO is turned OFF when the current running
toward the drive part 30 exceeds a given value. After the GTO is
turned OFF, the electric power output from the battery 50 is not
supplied to the drive part 30.
[0184] Furthermore, in the above embodiment, the battery
abnormality detection circuit 900 detects abnormal events of the
battery 50 based on signals from the LD terminal of the battery 50.
It is not necessary based on signals from the LD terminal. For
example, the battery abnormality detection circuit 900 measures the
temperature of the battery 50 and determines that the battery 50 is
abnormal when the temperature exceeds a given temperature.
Alternatively, the battery abnormality detection circuit 900
measures the resistance of the T terminal of the battery 50 and
detects any abnormal event of the battery according to the
resistance of the T terminal. Furthermore, the battery 50 is a
lithium ion battery in the above explanation. The battery can be a
lead rechargeable battery or nickel-cadmium battery or even other
kinds of batteries as long as it has capability of supplying
electric power to the power supply circuit 16. Here, when the
battery 50 is a lithium ion battery, which is lighter than a
nickel-cadmium battery or nickel-hydrogen battery, a lightweight
coreless motor can be used as the motor provided at the other end
of the coupling part 20 with a well-balanced manner; an overall
lightweight, well-operable electric lawn mower 1 can be
provided.
[0185] Furthermore, in the above embodiment, the control circuit
500 makes reference to a table stored in the internal memory to
determine the discharging voltage of the battery 50 based on
battery information supplied from the battery 50. This is not
restrictive. For example, the discharging voltage can be determined
from specific information contained in battery information. In such
a case, the discharging voltage can be half the rated voltage of
the battery 50 that is contained in battery information.
[0186] Furthermore, in the above embodiment, the operation part 10
and drive part 30 are provided on the coupling part 20 at a
distance from each other. They are not necessarily provided at a
distance or provided on the coupling part 20 as long as the
electric power output from the operation part 10 is supplied to the
drive part 30. For example, the operation part 10 and drive part 30
can be provided at one end of the coupling part 20 side by side or
the operation part 10 and drive part 30 can be connected only by a
conductive wire without the coupling part 20.
[0187] The electric lawn mower 1 can have a blade 39 provided at an
angle with respect to the coupling part 20 as shown in FIG. 14.
This allows the operator to maintain his/her natural posture during
general operation of the electric lawn mower 1 in which the
operator swings his/her hands holding the grip (grip part) 22 (not
shown) and D-shaped handle 21 around his/her hip as indicated by
the arrow O in FIG. 17. The electric lawn mower 1 shown in FIG. 14
is designed to have, for example, a total length A of approximately
180 cm and a blade inclination angle B of approximately 38 degrees
with respect to the coupling part, whereby the blade 39 is nearly
parallel to the ground surface when the distance C between the grip
22 and ground surface is 70 to 90 cm, which is slightly above the
hip of the operator. Additionally, the D-shaped handle 21 can be
attached by the operator at any point on the coupling part 20. The
distance E between the D-shaped handle 21 and grip 22, namely the
distance between the trigger 13 to which the operator applies a
force and the holding part of the D-shaped handle 21, is designed
to be nearly equal to the shoulder width of the operator, for
example, at least 20 cm and desirably 30 cm, whereby the operator
can perform the operation in his/her natural posture.
[0188] A belt holder 28 holding a belt 65 that can be placed over a
shoulder of the operator as shown in FIGS. 15 and 16 is provided
between the D-shaped handle 21 and grip 22. As shown in FIGS. 15
and 17, the belt 65 is engaged with the belt holder 28 and then the
belt 65 is placed over a shoulder of the operator. The weight of
the electric lawn mower 1 is received by the shoulder during the
operation, less tiring the operator.
[0189] Furthermore, a 14.4 V or 18 V lithium ion (Li-ion) battery
(lithium rechargeable battery) or nickel-cadmium (Ni--Cd) battery
having a common mounting part can be mounted on the operation part
10 of the electric lawn mower 1. Incidentally, a 14.4 V lithium
battery includes, for example, eight lithium ion battery cells
comprising, four battery cells connected in series while parallelly
connected with other four, connected in series, of the eight
battery cells and has a weight of approximately 550 g and a
capacity of 3.0 Ah, or a 14.4 V lithium battery includes, for
example, four series-connected lithium ion battery cells and has a
weight of approximately 300 g and a capacity of 1.5 Ah. A 18 V
lithium ion battery includes, for example, ten lithium ion battery
cells comprising, five battery cells connected in series, while
connected to other five, of the ten battery cells connected in
series, and has a weight of approximately 700 g and a capacity of
3.0 Ah, or a 18 V lithium ion battery includes, for example, five
series-connected lithium ion battery cells and has a weight of
approximately 400 g and a capacity of 1.5 Ah. A 14.4 V
nickel-cadmium battery includes, for example, 12 series-connected
nickel-cadmium battery cells and has a weight of approximately 800
g and a capacity of 3.0 Ah. A 18 V nickel-cadmium battery includes,
for example, 15 series-connected nickel-cadmium battery cells and
has a weight of approximately 1000 g and a capacity of 3.0 Ah.
[0190] The drive part 30 of the electric lawn mower 1 is relatively
lightweight because of no gear or core. The motor case 29 is formed
by molding aluminum alloy. The summed weight of the drive part 30
and the blade 39 is, for example, approximately 1500 g. Therefore,
as shown in FIG. 14, the gravity center G1 of the electric lawn
mower 1 when a 18 V nickel-cadmium battery is mounted on the
operation part 10, the gravity center G2 when a 18 V lithium ion
battery having a capacity 3.0 Ah is mounted, the gravity center G3
when a 14.4 V lithium ion battery having a capacity 3.0 Ah is
mounted, and the gravity center G4 when a 14.4 V lithium ion
battery having a capacity of 1.5 Ah is mounted are all on the drive
part 30 side with respect to the D-shaped handle 21. In other
words, the gravity center of the electric lawn mower 1 is always on
the drive part 30 side with respect to the D-shaped handle 21 with
any battery mentioned above being mounted on the operation part
10.
[0191] If the gravity center is located on the operation part 10
side with respect to the D-shaped handle 21, the operator has to
horizontally swing the D-shaped handle 21 while lifting it.
However, here, the gravity center of the electric lawn mower 1 is
located on the drive part 30 side with respect to the D-shaped
handle 21, whereby the electric lawn mower 1 automatically lowers
the coreless motor to the ground while the operator holds the
electric lawn mower 1 by holding the grip 22 and D-shaped handle
21. The operator does not need to apply a force to lower the
forefront of the electric lawn mower 1 during the operation, which
reduces the operator's workload and improves the operability. The
belt holder 28 between the D-shaped handle 21 and grip 22 allows
the coreless motor to automatically fall to the ground when the
belt 65 is placed over the shoulder, giving excellent operability.
With the belt 65 being placed over the shoulder, the operator can
hold the grip 22 in the rear of the belt holder 28 and applies to
the grip 22 a force toward the ground. In this way, the electric
lawn mower 1 is supported by the belt holder 28 and grip 22. The
electric lawn mower 1 can be swung about the belt holder 28 simply
by applying to the D-shaped handle 21 a force in the swing
direction. The blade 39 can easily be moved to the target site,
improving the operability.
[0192] In the above embodiment, the motor case 29 is made of
aluminum alloy. The motor case 29 can be made of resin and a weight
can be provided near the drive part 30 to have the gravity center
on the drive part 30 side with respect to the D-shaped handle 21.
However, the motor case 29 made of aluminum alloy provides better
cooling action, which curbs rise in the temperature of the coil
substrate 31, and increases the strength, which improves the
life.
[0193] Furthermore, the blade 39 of the electric lawn mower 1 is
directly driven by the central shaft 32 of the coreless motor,
namely the blade 39 is directly connected to the coreless motor
without any gear or the like, curbing mechanical loss. Furthermore,
no gear noise occurs, curbing unwanted noise. Furthermore, the
coreless motor rotates as a magnetic flux passing through the coil
substrate 31 in the axial direction of the central shaft 32 occurs.
Therefore, the motor does not protrude in the axial direction of
the central shaft 32 even though the motor is provided where the
drive part 30 side is (where the blade 39 side is). The drive part
30 can significantly be downsized in the axial direction of the
central shaft 32. Therefore, any reduction in the operability due
to the protrusion of the drive part 30 in the axial direction of
the central shaft 32 is curbed.
[0194] The coreless motor in the above embodiment is a coreless
motor having a coil substrate 31 in the rotor part and a brush 33
with a magnet part 37 in the stator part. It can be a
brushless-type coreless motor comprising a coil substrate in the
stator part and a magnet in the rotor part.
[0195] Furthermore, in the above embodiment, the gravity center is
located on the coreless motor side with respect to the D-shaped
handle 21 regardless of any battery, 14.4 V or 18 V lithium ion
battery or nickel-cadmium rechargeable battery, being mounted.
However, from the viewpoint of providing an electric lawn mower
that is overall lightweight, well-balanced, quiet, and operable for
a prolonged time, the structure allowing only lithium ion batteries
to be mounted may be used.
[0196] Furthermore, in the above embodiment, an electric operating
machine applied to an electric lawn mower using an electric motor
is described. The present invention is applicable to any electric
machine and similarly applicable to a wide range of other operating
machines using an electric motor. Particularly, the present
invention is suitable for sanders, polishers, routers, and dust
collectors in which the rotation of an electric motor is directly
transferred to the work tool (rotary blade, fan, etc.) via no
reduction gears.
[0197] Having described and illustrated the principles of this
application by reference to one or more preferred embodiments, it
should be apparent that the preferred embodiments may be modified
in arrangement and detail without departing from the principles
disclosed herein and that it is intended that the application be
construed as including all such modifications and variations
insofar as they come within the spirit and scope of the subject
matter disclosed herein.
[0198] This application claims the benefit of Japanese Patent
Applications JP2009-199066 filed Aug. 28, 2009, JP2009-229092 filed
Sep. 30, 2009 and JP2010-006186 filed Jan. 14, 2010, the entire
disclosure of which is incorporated by reference herein.
REFERENCE SIGNS LIST
[0199] 1 electric lawn mower [0200] 10 operation part [0201] 11
battery mounting part [0202] 12 main switch [0203] 13 trigger
[0204] 14 remaining battery level display [0205] 15 main LED [0206]
16 power supply circuit [0207] 20 coupling part [0208] 21 D-shaped
handle [0209] 22 grip [0210] 23 U-shaped handle [0211] 24 wire
[0212] 25 rotation shaft [0213] 26 variable speed switch [0214] 27
resin cover [0215] 30 drive part [0216] 40 running indicator LED
[0217] 50 battery [0218] 100 main switch circuit [0219] 200 trigger
switch circuit [0220] 300 booster circuit [0221] 400 speed
adjustment circuit [0222] 500 control circuit [0223] 600 current
detection circuit [0224] 700 battery voltage detection circuit
[0225] 800 battery abnormality detection circuit [0226] 900
constant voltage circuit [0227] 910 speaker [0228] 920 sound
reproducing circuit [0229] 930 radio
* * * * *