U.S. patent application number 14/113902 was filed with the patent office on 2014-02-13 for lubrication control apparatus for vehicle in-wheel motor unit.
This patent application is currently assigned to Nissan Motor Co., Ltd.. The applicant listed for this patent is Yasuhiro Yamauchi. Invention is credited to Yasuhiro Yamauchi.
Application Number | 20140041619 14/113902 |
Document ID | / |
Family ID | 49831613 |
Filed Date | 2014-02-13 |
United States Patent
Application |
20140041619 |
Kind Code |
A1 |
Yamauchi; Yasuhiro |
February 13, 2014 |
LUBRICATION CONTROL APPARATUS FOR VEHICLE IN-WHEEL MOTOR UNIT
Abstract
Each oil pump (32) is drivingly controlled in such a way that,
in a low vehicle speed region lower than a set vehicle speed VSP1
at which a stirring resistance by oil within an in-wheel unit case
(3) is not in excess of an allowance level, a suction and supply
quantity denoted by a solid line characteristic is provided. In
other words, the oil pump(s) is stopped until the vehicle speed
reaches to a predetermined vehicle speed VSP0 at which a remaining
oil within an oil passage is scattered in all directions and
becomes disappeared after the start of vehicle in an oil pump
stopped state including a vehicle stop at which the lubrication is
not necessary.
Inventors: |
Yamauchi; Yasuhiro;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yamauchi; Yasuhiro |
Yokohama-shi |
|
JP |
|
|
Assignee: |
Nissan Motor Co., Ltd.
|
Family ID: |
49831613 |
Appl. No.: |
14/113902 |
Filed: |
February 29, 2012 |
PCT Filed: |
February 29, 2012 |
PCT NO: |
PCT/JP2012/055057 |
371 Date: |
October 25, 2013 |
Current U.S.
Class: |
123/196R |
Current CPC
Class: |
F16H 57/0006 20130101;
F16H 57/0436 20130101; F16H 57/0486 20130101; F16H 57/0479
20130101; B60K 2007/0092 20130101; F16H 57/0402 20130101; F16H
57/0426 20130101; B60K 2007/0038 20130101; B60K 17/046 20130101;
F01M 11/00 20130101; B60K 7/0007 20130101; F16H 57/043
20130101 |
Class at
Publication: |
123/196.R |
International
Class: |
F01M 11/00 20060101
F01M011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2011 |
JP |
2011-099077 |
Apr 27, 2011 |
JP |
2011-099078 |
Apr 27, 2011 |
JP |
2011-099079 |
Sep 15, 2011 |
JP |
2011-201799 |
Sep 15, 2011 |
JP |
2011-201802 |
Sep 15, 2011 |
JP |
2011-201803 |
Claims
1. A lubrication control apparatus for in-wheel motor units for use
in an in-wheel motor driven vehicle in which road wheels are driven
by means of the individual in-wheel motor units in order for the
vehicle to be travelable and in which individual oil pumps
lubricate within the in-wheel motor units through oil sucked and
supplied from lower parts of respective in-wheel motor unit cases,
the lubrication control apparatus comprising: oil pump driving
control means for drivingly controlling the oil pumps to stop the
oil pumps when the vehicle is in a vehicle stopped state and to
activate the oil pumps when a vehicle speed has reached to a
predetermined vehicle speed.
2. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 1,
wherein the predetermined vehicle speed to activate the oil pumps
is a vehicle speed at which a remaining oil in an oil suction and
supply passage to suck and supply oil is scattered in all
directions and becomes disappeared.
3. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 1,
wherein the oil pump driving control means sets the predetermined
vehicle speed in accordance with a traveling distance of the
vehicle in the oil pump stopped state.
4. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 3,
wherein the oil pump driving control means determines the vehicle
traveling distance in the oil pump stopped state by an integration
of the vehicle speed with respect to time during a travel in the
oil pump stopped state to contribute on the setting of the
predetermined vehicle speed.
5. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 1,
wherein the oil pump driving control means drivingly controls the
oil pumps such that oil suction and supply quantities from the oil
pumps are gradually increased as the vehicle speed is increased in
a low vehicle speed region which is lower than a set vehicle speed
at which a stirring resistance of oil at each of the lower parts
within the in-wheel motor unit cases does not exceed an allowance
level after the vehicle speed has reached to the predetermined
vehicle speed.
6. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 5,
wherein the in-wheel motor driven vehicle is travelable by driving
at least pair of right and left road wheels through the individual
in-wheel motor units and the oil pump driving control means
drivingly controls the oil pumps such that the oil suction and
supply quantities when the vehicle speed is increased and reached
to the set vehicle speed are predetermined quantities at which oil
levels at the lower parts within the respective cases of the
in-wheel motor units which provide the pair of left and right
in-wheel motor units are mutually the same.
7. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 6,
wherein the oil pump driving control means drivingly controls the
oil pumps such that each of the oil suction and supply quantities
from the oil pumps is maintained at a predetermined quantity in a
high vehicle speed region of the vehicle speed equal to or higher
than the set vehicle speed.
8. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 6,
wherein the predetermined quantity related to each of the oil
suction and supply quantities is a minimum oil quantity required
for the lubrication within each of the in-wheel motor units.
9. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 1,
wherein the oil pump driving control means drivingly controls the
oil pumps to activate the oil pumps under a condition such that the
vehicle speed is raised to the predetermined vehicle speed at which
a remaining oil in an oil suction and supply passage to suck and
supply oil is scattered in all directions and becomes disappeared
after the travel start of the vehicle and drivingly controls the
oil pumps to activate the oil pumps from a vehicle speed lower than
the predetermined vehicle speed including the stop of the vehicle
in accordance with a demanded driving torque of the vehicle.
10. The lubrication control apparatus for the in-wheel motor units
for use in the in-wheel motor driven vehicle as claimed in claim 1,
wherein the oil pump driving control means activates the oil pumps
when the vehicle speed has reached to the predetermined vehicle
speed after the start of traveling of the vehicle and drivingly
controls the oil pumps such that the oil pumps are activated at a
lower vehicle speed than the predetermined vehicle speed.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubrication control
apparatus which is useful in a drive unit (hereinafter, referred to
as an in-wheel motor unit) for each of road wheels and which is
used for an electric automotive vehicle travelable by driving the
respective road wheels through individual electrically driven
motors.
BACKGROUND ART
[0002] The in-wheel motor unit is, for example, as shown in a
Patent Document 1, provided with a speed reduction gear mechanism
such as a planetary gear set in addition to the above-described
electrically driven motor and constitutes a single unit to transmit
a rotational power from the electrically driven motor to a
corresponding one of the road wheels under a speed reduction by
means of the above-described speed reduction gear mechanism to
drive the corresponding road wheel.
[0003] Hence, it is necessary to lubricate the above-described
speed reduction gear mechanism in each of the in-wheel motor
units.
However, a resting of the lubrication for the speed reduction
mechanism on stirred up oil by means of a rotary body within the
in-wheel motor unit introduces an increase in a consumed electric
power of the in-wheel motor unit (an electrically driven motor) due
to an oil stirring resistance and introduces a worsening of an
electric power consumption (a travelling distance per unit power
(km/kWh) or an index representing an electric power required for
the traveling for a predetermined distance) which provides a most
important task for the electric automotive vehicle.
[0004] As described in Patent Document 1, an oil pump whose
electric power consumption is considerably small as compared with
the electric power consumption due to the oil stirring up
resistance is, in many cases, used to suck oil within the lower
part of the in-wheel motor unit and this oil is supplied toward a
lubrication request location to perform a predetermined
lubrication.
[0005] When this lubrication is carried out, a lubrication control
technique described in Patent Document 1 is such that a lubrication
oil quantity in one of the in-wheel motor units at a higher
temperature side (oil suction supply quantity by means of an oil
pump) is larger than the lubrication oil quantity in the other of
the in-wheel motor units at a lower temperature side in a case
where oil temperatures within a pair of in-wheel motor units (left
and right in-wheel motor units which are for left and right road
wheels) are mutually different from each other to eliminate an oil
temperature difference between the left and right in-wheel motor
units.
[0006] According to the lubrication control technique of the
in-wheel motor unit, a left-and-right road wheel driving force
difference caused by the oil temperature difference between the
left and right in-wheel motor units are relieved so that a
traveling stability of the in-wheel motor drive electric automotive
vehicle can be improved.
PRE-PUBLISHED DOCUMENT
[0007] Patent Document 1: Japanese Patent Application First
Publication No. 2008-195233
DISCLOSURE OF THE INVENTION
Task to be Solved by the Invention
[0008] However, the lubrication control technique described in
Patent Document 1 makes oil suction and supply quantity of the oil
pump between the left and right in-wheel motor units different in
accordance with the oil temperature difference between the left and
right in-wheel motor units. Basically, the oil pump is continued to
be operated even during a stop of the vehicle unless the ignition
switch is in the ON state. Hence, the following problem occurs as
will be described below.
[0009] That is to say, since the in-wheel motor unit is directly
coupled to the corresponding one of the road wheels, the in-wheel
motor unit is not disposed at an inside of the vehicle body which
can need a noise sound countermeasure but it is always exposed to
an outside of the vehicle body. Thus, it is difficult to make a
sound shielding countermeasure.
Therefore, during a vehicle stop state in which the in-wheel motor
drive vehicle is in a state of no sound, or in a low-speed region
in which almost no sound traveling is carried out, an operation
sound of the oil pump(s) gives a noise of a sense of
uncomfortablity by an occupant or by a surrounding person outside
the vehicle.
[0010] However, in the lubrication control technique described in
Patent Document 1 which continues the oil pump unless the ignition
switch is in the ON state even in a vehicle stop state in which no
noise state occurs or even in a state in which a low vehicle speed
region in which almost no sound traveling state occurs, the
operation sound of the oil pump(s) during the vehicle stop or in
the low vehicle speed region unavoidably provides a problem of
hearing to the person outside of the vehicle from the sound having
the sense of uncomfortablity.
[0011] From the viewpoint such that it is basically not necessary
for the lubrication of the in-wheel motor unit at the time of the
vehicle stop and, while oil is left within a lubrication oil
passage even at the low vehicle speed region, the lubrication of
the in-wheel motor unit is possible by means of the in-wheel motor
unit and the number of rotations of the oil pump may be reduced as
low as possible and the oil pumps may be stopped, this idea is
embodied. That is to say, it is an object of the present invention
to provide a lubrication control apparatus for the in-wheel motor
unit for the vehicle which can eliminate the problem of solving the
operation sound (noise) of the oil pump(s) in the in-wheel motor
unit during the vehicle stop or at the low vehicle speed region and
can avoid the worsening of the traveling distance per unit electric
power due to a wasteful operation of the oil pump.
Means to Solve the Task
[0012] In order to achieve the above-described object, a
lubrication control apparatus for the vehicular in-wheel motor unit
for the vehicle according to the present invention is structured as
follows.
First, the in-wheel motor driven vehicle which is a prerequisite of
the present invention and the lubrication control apparatus for the
in-wheel motor unit used in the in-wheel motor driven vehicle will
be described below. The in-wheel motor driven vehicle is travelable
by driving the road wheels through the individual in-wheel drive
units. In addition, the lubrication control apparatus used in this
vehicle is arranged to lubricate within the above-described
in-wheel motor units through oil sucked and supplied from the lower
parts of the in-wheel motor unit casings.
[0013] The present invention is characterized in the structure such
that oil pump drivingly control means (oil pump drivingly control
section) as will be described later is installed for the
lubrication control apparatus for the in-wheel motor unit.
The oil pump drivingly control means drivingly controls the oil
pump in such a way that the oil pump is stopped in a state in which
the vehicle is stopped and the oil pump is activated when the
vehicle has arrived at a predetermined vehicle speed.
Effect Achievable by the Invention
[0014] In the lubrication control apparatus for the in-wheel motor
unit for the vehicle according to the present invention, the oil
pump is drivingly controlled in such a way that, while the vehicle
speed is from the vehicle stopped state and has reached to the
predetermined vehicle speed, the oil pump is stopped and the oil
pump is drivingly controlled to activate the oil pump when the
vehicle speed has reached to the predetermined vehicle speed.
Hence, the oil pump is drivingly controlled to activate the oil
pump at the time of the arrival of the vehicle speed at the
predetermined vehicle speed. Hence, a wasteful operation of the oil
pump at the low vehicle speed region equal to or below the
predetermined vehicle speed can be prevented. Hence, the wasteful
operation of the oil pump at the time of the vehicle stop or at the
low vehicle speed region equal to or lower than the above-described
predetermined vehicle speed can be prevented. Then, the operation
sound of the oil pump during the vehicle stop or during the low
vehicle speed region at which no sound or almost no sound traveling
occurs can be avoided. In addition, the worsening of the electric
power consumption due to the wasteful operation of the oil pump
during the vehicle stop or during the vehicle traveling at the low
vehicle speed region can be avoided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a longitudinal cross sectional side view
representing an in-wheel motor unit having a lubrication control
apparatus in a first preferred embodiment according to the present
invention.
[0016] FIGS. 2 (a) and 2(b) are an oil guide installed within an
oil gallery of an in-wheel motor unit shown in FIG. 1, FIG. 2 (a)
representing a detailed longitudinal side sectional view of the oil
guide viewed from an arrow-marked direction, with the cross section
on a line of II to II in FIG. 2 (b), and FIG. 2(b) representing a
detailed front view of the oil guide viewed from a right side of
FIG. 2(a).
[0017] FIG. 3 is a flowchart representing a lubrication control
program executed by an oil pump controller in FIG. 1.
[0018] FIG. 4 is a flowchart representing a sub routine related to
an oil pump variable flow quantity control in the lubrication
control program shown in FIG. 3.
[0019] FIG. 5 is a characteristic line diagram representing an oil
suction and supply quantity control characteristic of an oil pump
drivingly controlled by the lubrication control program shown in
FIG. 3.
[0020] FIG. 6 is a timing chart representing an oil temperature
variation characteristic of the in-wheel motor unit in FIG. 1 for
each of oil immersion quantities of a rotor.
[0021] FIG. 7 is a characteristic line diagram representing a
variation characteristic of an oil pump target revolution speed
required to achieve a constant flow quantity shown in FIG. 5 in a
constant flow quantity control area shown in FIG. 5.
[0022] FIG. 8 is a characteristic line diagram representing a
variation characteristic related to a reduction margin .DELTA.VSP0
of an oil pump activation vehicle speed VSP0 shown in FIG. 5 with
an integration value of a demanded drive torque as a parameter.
[0023] FIG. 9 is a characteristic line diagram representing a
variation characteristic related to a reduction margin .DELTA.VSP0
of oil pump activation vehicle speed VSP0 shown in FIG. 5 with a
traveling distance in the oil pump stopped state as a
parameter.
[0024] FIG. 10 is a timing chart representing an explanation of a
relationship between the time integration value of a vehicle speed
during a traveling of the vehicle in a stopped state of the oil
pump and a traveling distance in the oil pump stopped state.
[0025] FIG. 11 is a flowchart representing a subroutine related to
an oil pump variable flow quantity control in a second preferred
embodiment which accords with a time integration value of a
traveling distance demanded torque in a state of a stopped state of
the oil pump from among the oil pump variable flow quantity
controls in the lubrication control program in FIG. 3.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0026] A detailed explanation of the present invention will,
hereinafter, be made on a basis of preferred embodiments shown in
the attached drawings.
Structure of a First Embodiment
[0027] FIG. 1 shows a longitudinal cross sectional side view
representing an in-wheel motor unit in which a lubrication control
apparatus in a first preferred embodiment according to the present
invention is equipped.
In FIG. 1, reference numeral 1 denotes a case main frame of an
in-wheel motor unit, reference numeral 2 denotes a rear cover of a
case main frame 1, a unit case 3 of an in-wheel motor unit is
formed by means of a mutual uniting of a case main frame 1 and a
rear cover 2.
[0028] In-wheel motor unit shown in FIG. 1 houses an electrically
driven motor 4 and a planetary gear type speed reduction gear set 5
(hereinafter, referred simply as to a speed reduction gear set)
within a unit case 3. Electrically driven motor 4 includes: an
annular stator 6 which is fitted to an inner circumferential
portion of case main frame 1 to be fixed; and a rotor 7
concentrically arranged onto an inner circumferential portion of
annular stator 6 with a radial gap.
[0029] Speed reduction gear set 5 serves to perform a drive
coupling between an input axle 8 and an output axle 9 opposed to
each other and coaxially arranged with each other. Speed reduction
gear set 5 includes: a sun gear 11; and a stationary ring gear 12
coaxially arranged with a deviation toward an axial line direction
toward which ring gear 12 approaches to output axle 9; a stepped
planetary pinion 13 (a stepped pinion) 13 meshed with sun gear 11
and ring gear 12; a pinion shaft 14 to rotatably support stepped
planetary pinion 13; and carriers 15a, 15b supporting pinion shaft
14.
[0030] Input shaft 8 is integrally formed with sun gear 11 at an
inner end near to output axle 9 and its input axle 8 is extended
toward a backward direction directed to rear cover 2 from sun gear
11. Output axle 9 is extended from speed reduction gear set 5
toward an opposite direction (forward direction) from speed
reduction gear set 5 and is projected from the opening of a front
end (a right side of the drawing) of case main frame 1 and a road
wheel 16 is coupled at this projection section as will be described
later.
[0031] Coaxial abutting terminals of both of input axle 8 and
output axle 9 are fitted mutually relatively rotatably and an
intervention of a bearing 17 which may be constituted by a ball
bearing to set an inter input/output axle bearing fitting
section.
Locations of input axle 8 and output axle 9 spaced apart from this
bearing 17 in the axial line direction are journalled on unit case
3 through a bearing 18 which may be constituted by the ball bearing
and a bearing 19 which may be constituted by a double-row angular
bearing.
[0032] It should be noted that bearing 19 is intervened between an
inner periphery of an end lid 20 enclosing a front end opening of
case main frame 1 and an outer periphery of a wheel hub 21 fitted
to a projection section of output axle 9 projected from a front end
opening of case main frame 1.
[0033] Electrically driven motor 4 couples its rotor connected to
input axle 8 and its connected position is an axial line direction
position between speed reduction gear set 5 and bearing 18.
[0034] Above-described ring gear 12 is fixed and installed within
the front end opening of case main frame 1 in a whirl stop state
and in a stopper state. When the stopper state is carried out, a
seal adapter 22 serves as the stopper for ring gear 12 by means of
a seal adapter 22. Seal adapter 22 is attached onto a front end
opening of case main frame 1 and a bolt 20a serves to attach end
lid 20 onto seal adapter 22.
[0035] Stepped planetary pinion 13 is a stepped pinion (a planetary
gear) integrally provided with a large diameter gear section 13a
meshed with sun gear 11 on input axle 8; and a small diameter gear
section 13b meshed with ring gear 12 and which rolls stepped
planetary pinion 13 along the inner periphery of ring gear 12.
This stepped planetary pinion 13 is arranged in a direction such
that large diameter gear section 13a is positioned far away from
output shaft 9 and small diameter gear section 13b is positioned
near to output axle 9.
[0036] Stepped planetary pinion 13 is arranged at equal intervals
in a circumferential direction with, for example, four per couple.
Common carriers 15a, 15b rotatably support stepped planetary pinion
13 via a pinion shaft 14 maintaining this circumferential direction
equal interval arrangement.
Carriers 15a, 15b and stepped planetary pinion 13 (a pinion shaft
14) are extended from output axle 9 toward input axle 8 side and is
attached onto output axle 9.
[0037] Next, an essential of coupling road wheel 16 to output axle
9 will be described in details.
A brake drum 25 is integrally and concentrically coupled to wheel
hub 21 and a plurality of wheel bolts 26 are embedded and
penetrated through wheel hub 21 and brake drum 25 so as to be
projected in an axial line direction of the in-wheel motor unit. A
wheel disk for the corresponding road wheel is tightly contacted
against a bottom surface of brake drum 25 in order for wheel bolts
26 to be penetrated through bolt holes penetrated through the wheel
disk and, in this state, wheel nuts 27 are tightly screwed into
wheel bolts 26 so that an attachment of road wheel 16 to output
axle 9 is carried out.
[0038] <Action of the in-Wheel Motor Unit>
When a power is supplied to stator 6 of electrically driven motor
4, a generated electromagnetic force causes rotor 7 of electrically
driven motor 4 to be rotationally driven so that a rotational
driving force is transmitted to sun gear 11 of speed reduction gear
set 5 via input axle 8. Thus, sun gear 11 causes stepped planetary
pinion 13 to be rotated via a large diameter gear section 13a. At
this time, fixed ring gear 12 functions as a reaction force
receiver. Thus, stepped planetary pinion 13 performs a planetary
motion so that small diameter section 13b rolls along ring gear 12.
The planetary motion of stepped planetary pinion 13 is transmitted
to output shaft 9 via carriers 15a, 15b and output axle 9 is
rotated in the same direction as input axle 8.
[0039] Speed reduction gear set 5 due to the above-described
transmission action transmits a rotation from electrically driven
motor 4 to input shaft 8 with the speed reduction determined by a
ratio determined from a teeth number determined according to the
teeth number of sun gear 11 and the teeth number of ring gear 12.
The rotation of output axle 9 is transmitted to road wheel 16 via
coupled wheel hub 21 and wheel bolts 26 so that this road wheel 16
can rotationally be driven.
[0040] It should be noted that another road wheel (not shown) at an
opposite side in the leftward or rightward directions which
constitutes a pair of road wheels with road wheel 16 is
rotationally driven by the in-wheel motor unit of the same
specification and the vehicle can be travelled according to the
rotational drive at the same driving force of the left and right
road wheels which constitute these pairs. When the vehicle is
braked, rod wheel 16 is frictionally braked due to a press of brake
shoe 27 onto an inner peripheral surface of a drum of brake drum
25.
[0041] <Lubrication Oil Passage of in-Wheel Motor Unit>
In the above-described in-wheel motor unit, it is necessary to
lubricate speed reduction gear set 5 interposed between input axle
8 and output axle 9.
[0042] It should be noted that, since it is not necessary to
lubricate electrically driven motor 4, a partitioning wall may be
disposed between electrically driven motor 4 and speed reduction
gear set 5 and within case main frame 1 to block a housing chamber
of electrically driven motor 4 and another housing chamber of speed
reduction gear set 5. However, in this case, it is not possible to
mutually approach electrically driven motor 4 and planetary gear
set 5 in order for electrically driven motor 4 and speed reduction
gear set 5 to be overlapped in a radial direction of the in-wheel
motor unit as shown in FIG. 1. Consequently, a mountability of the
in-wheel motor unit due to an elongation of its axial direction is
reduced.
[0043] Therefore, as shown in FIG. 1 in the first embodiment, the
housing chamber of electrically driven motor 4 and the housing
chamber of speed reduction gear set 5 are made in common to each
other (standardized) and electrically driven motor 4 and speed
reduction gear set 5 approach each other within the same chamber
within case main frame 1 with electrically driven motor 4 and speed
reduction gear overlapped in the radial direction, so that a size
of the axial line direction can be reduced. Thus, the mountability
of the in-wheel motor unit can be improved.
[0044] In this embodiment, the following lubrication control
apparatus can carry out the lubrication of speed reduction gear set
5, the lubrication of bearing 17 between input axle 8 and output
axle 9, and the lubrication of bearing 18 between input axle 8 and
a unit case 3.
[0045] First, a lubrication oil passage for the above-described
purpose will, hereinafter, be explained. Lubricating oil 31 is
retained at the lower part within unit case 3 and an electrically
driven oil pump 32 is disposed at the lower part of unit case
3.
Oil pump 32 includes a suction port 32a and a discharge port 32b,
suction port 32a being opened to a reserving section of oil 31 at
the lower part of unit case 3 via an oil filter 33.
[0046] A lubricating oil storage quantity of oil 31 provides a
quantity such that its level 31a is not lower than a suction port
32a regardless of a vibration of the vehicle and a gradient of the
vehicle. Even if the vibration of the vehicle occurs and at the
time of gradient of the vehicle, oil pump 32 can suck oil 31 from
suction port 32a. The storage quantity of oil 31 for all of
in-wheel motor driven road wheels is to be the same level as a
static oil level 31a at the lower part of the in-wheel motor
unit.
[0047] A circular oil gallery 34 which is concentric to input shaft
8 is formed on input shaft 8 and a discharge port 32b of oil pump
32 is passed to this oil gallery 34.
Oil gallery 34 is defined among an end surface of input axle 8
which is far away from output shaft 9, an end surface of bearing
18, and an oil cap 35 fitted into a rear cover 2 and which is
opposed against both end surfaces of input axle 8 and bearing
18.
[0048] An oil guide 38 is intervened among end surface of input
axle 8 which is far away from output axle 9, an end surface of
bearing 18, and oil cap 35.
This oil guide 38 is a wholly circular plate form as clearly shown
in FIGS. 2(a) and 2(b). A guide envelope 38a is projected at the
center section and a guide hole 38b is fitted on the peripheral
section of oil guide 38.
[0049] Above-described oil guide 38 includes a guide envelope 38a
inserted into a corresponding end of a hollow hole 8a disposed at a
center of input axle 8 as shown in FIG. 1 and an opposing end of
hollow hole 8a is opened within a mutual fitting empty portion of
input axle 8 and output axle 9.
[0050] A radial oil hole 42 which extends toward an outer direction
in the radial direction of carrier 15a is provided on carrier 15a
and a radial oil hole 8b is formed in input axle 8 so as to be
aligned in a row of this radial oil hole 42.
A radial outer end of radial oil hole 42 disposed on carrier 15a is
passed through a hollow hole 43 at the center of pinion shaft 14.
An oil injection hole 44 which extends in a radial outward
direction from hollow center hole 43 is disposed on pinion shaft 14
so that oil can be supplied to a lubrication required location of
speed reduction gear set 5 by means of a centrifugal force from oil
injection hole 44.
[0051] Input axle 8 further includes a radial oil hole 8c extended
toward bearing 17 and intervened at the mutual fitting section of
input and output axles 8, 9 and oil can be supplied to bearing 17
from this radial oil hole 8c.
[0052] An action of lubrication oil passage as will be described
with reference to FIGS. 1 and 2 will, hereinafter, be described
below.
During an operation of the in-wheel motor unit, an oil pump 32 is
driven in a case where it is necessary to lubricate both of
bearings 17, 18 and speed reduction gear set 5. When
(corresponding) oil pump 32 is driven, a lubricating oil 31 at the
lower part of in-wheel motor unit case 3 is sucked via a port 32a
as shown in an arrow-mark in FIG. 1 and is sucked via a port 32a
and discharged from port 32a and this discharge oil is, thereafter,
reached to oil gallery 34.
[0053] During the rotational drive of road wheel 16 by means of the
in-wheel motor unit, oil within a hollow hole 43 of pinion shaft 14
and within oil injection hole 44, upon receipt of a centrifugal
force, is injected from oil injection hole 44 as denoted by an
arrow-marked direction shown in FIG. 1 and is supplied to the
lubrication required location of speed reduction gear set 5.
The oil injection quantity from related injection hole 44 is
supplemented by oil directed from oil gallery 34 to pinion shaft
hollow hole 43 via guide envelope 38a of oil guide 38, hollow hole
8a of input axle 8, radial hole 8b in the radial direction, radial
oil hole 8b, and radial directional oil hole 42 and the supply of
oil to speed reduction gear set 5 can continuously be carried
out.
[0054] The stored oil within oil gallery 34 is, on the other hand,
directed toward bearing 18 as shown in the arrow mark in FIG. 1
passing through a circumferential portion guide hole 38b disposed
on oil guide 38 to perform lubrication for bearing 18.
Oil reached to hollow hole 8a of input axle 8 from oil gallery 34
via guide envelope 38a of oil guide 38 is simultaneously reached to
bearing 17 between input and output axles 8, 9 via radial oil hole
8c as shown in the arrow mark shown in FIG. 1 so as to be served as
the lubrication of bearing 17.
[0055] Speed reduction gear set 5 generates a metallic powder
during a power transmission since speed reduction gear set 5 is a
mechanical element and a metallic powder is mixed within oil
circulated therein.
Oil in which the metallic powder is mixed and part of it is
adsorbed on a permanent magnet within electrically driven motor 4
and an adhesion quantity of metallic powder onto electrically
driven motor 4 is increased along a passage of time. In this way,
if the adhesion quantity of the metallic powder to electrically
driven motor 4 is increased, a reduction of performance of
electrically driven motor 4 is introduced so that a power
performance of in-wheel motor unit type electric automotive vehicle
is reduced.
[0056] During this circulation, part of metallic powder mixed in
oil is adsorbed onto the permanent magnet within electrically
driven motor 4 and, as the passage of time, the adhesion quantity
of metallic powder onto electrically driven motor 4 is
increased.
In this way, if the adhesion quantity of metallic powder to
electrically driven motor 4 is increased, the reduction in the
performance of electrically driven motor 4 is introduced and the
dynamic performance of the in-wheel motor electric automotive
vehicle is reduced.
[0057] The following countermeasure is taken in the in-wheel motor
unit shown in FIG. 1 to solve the above-described problem.
An axial line directional groove 47 is disposed on a housing inner
peripheral surface 3a to which a lower section 6a of stator 6
immersed into an oil reservoir is fitted and both ends 47a, 47b of
axial line direction groove 47 are opened to spaces 45, 46 at both
sides in the axial line direction of electrically driven motor 4. A
traffic of oil between a housing space 45 at which speed reduction
gear set 5 is placed and a housing space 46 at the opposite side of
the housing space is carried out almost via axial line direction
groove 47.
[0058] In addition, a permanent magnet 48 is fixed within housing
(unit case) 3, permanent magnet 48 being in a proximity of opening
end 47a of axial line direction groove 47 near to housing space 46
at which speed reduction gear set 5 is positioned.
It should be noted that stator 6 may be mold formed so that oil is
not immersed into at least lower section 6a of stator 6.
[0059] It should be noted that the metallic powder mixed when oil
passes through speed reduction gear set 5 is adsorbed on permanent
magnet 37 when the metallic powder enters opening end 47a of axial
line direction groove 47 from the oil reservoir within speed
reduction gear set housing space 45 so that the metallic powder can
be removed from oil.
Thus, the adhesion of the metallic powder onto electrically driven
motor 4 can be prevented and the performance of electrically driven
motor 4 due to the adhesion of metallic powder onto electrically
driven motor 4 is reduced so that the above-described problem can
be avoided.
[0060] <Lubrication Control of the in-Wheel Motor Unit>
When the above-described lubrication of the in-wheel motor unit
(planetary gear set 5 and bearings 17, 18) is carried out, oil pump
controller 51 shown in FIG. 1 controls the above-described
lubrication via a driving control of (corresponding) oil pump 32 as
follows.
[0061] Oil pump controller 51 inputs: a signal from oil temperature
sensor 52 detecting an oil temperature Temp of lubricating oil 31;
a signal from vehicle speed sensor 53 detecting a vehicle speed
VSP; and a signal from a demanded driving torque calculating
section 54 calculating a demanded driving torque Td of the
vehicle.
Demanded driving torque calculating section 54 does not to only
calculate demanded driving torque Td but also calculate demanded
driving torque Td irrespective of the driver's intention such as a
creep torque and so forth.
[0062] Oil pump controller 51 executes a control program shown in
FIGS. 3 and 4 on a basis of the above-described input information
and drivingly controls (corresponding) oil pump 32 so that the
suction and supply quantity of oil by means of this oil pump 32 is
as illustrated in FIG. 5.
[0063] At a step S11 in FIG. 3, oil pump controller 51 determines
whether vehicle speed VSP is equal to or higher than a set vehicle
speed VSP1 shown in FIG. 5.
This setting vehicle speed VSP1 is a lowest vehicle speed (for
example, 30 km/h) of a high vehicle speed region at which the oil
stirring resistance to rotor 7 immersed into oil 31 as shown in D
of FIG. 1 due to the large diameter of rotor 7 exceeds an allowance
level (almost negligible level). In this high vehicle speed region,
oil level 31a at the lower part of in-wheel motor unit case is
different between right and left road wheels. At this time, oil
immersion quantity D of rotor 7 between the right and left road
wheels, namely, the oil stirring resistance to rotor 7 is largely
different so that a large driving force difference between the
right and left road wheels is generated and a traveling stability
of the vehicle becomes worsened.
[0064] It should be noted that FIG. 6 is a characteristic graph
representing how an oil temperature Temp within the in-wheel motor
unit is varied in accordance with oil immersion quantity D of rotor
7 in a non-load state under a certain vehicle speed VSP equal to or
higher than set vehicle speed VSP1.
As oil immersion quantity D of rotor 7 becomes larger, a time
variation rate of oil temperature Temp becomes abrupt. This means
that, as oil immersion quantity D of rotor 7 becomes larger, the
oil stirring resistance to rotor 7 becomes larger so that a
reduction in the road wheel driving force due to a power loss is
severe.
[0065] Hence, when a high vehicle speed region (VSP.gtoreq.VSP1) at
which the oil stirring resistance is in excess of the allowance
level, oil levels 31a of the left and right in-wheel motor units
are often made different from each other. At this time, an oil
stirring resistance difference to rotor 7 becomes large so that the
large driving force difference between the right and left road
wheels is generated and such a problem that a traveling stability
of the vehicle becomes worsened occurs.
[0066] In a case where vehicle speed VSP at step S11 is determined
to be equal to or larger than set vehicle speed VSP1, at a step S12
of FIG. 3, oil pumps 32 in the left and right in-wheel motor units
are drivingly controlled so that oil suction and supply quantities
Q are maintained to provide constant flow quantity Qconst shown in
FIG. 5. Hence, step S12 corresponds to oil pump driving control
means according to the present invention.
[0067] Oil pump controller 51 when this drive control is carried
out derives an oil pump target revolution number Nop from oil
temperature Temp on a basis of the constant flow quantity (Qconst)
achieving characteristic, for example, in FIG. 7 with this
characteristic taken into consideration since oil suction and
supply quantity Q is varied in accordance with oil temperature Temp
even under the same rotation speed of (each) oil pump 32, is
commanded to oil pump 32 (each oil pump 32 of the left and right
in-wheel motor units) as shown in FIG. 1 so that (corresponding)
oil pump 32 is drivingly controlled at constant flow quantity
Qconst shown in FIG. 5 in the high vehicle speed region
(VSP.gtoreq.VSP1) under any oil temperature Temp according to the
driving control described above.
[0068] The above-described constant flow quantity Qconst is a unit
oil quantity required at minimum to lubricate speed reduction gear
set 5 within the (corresponding) in-wheel motor unit and is set to
an oil quantity at the time of the vehicle speed at which, for
example, this unit required oil quantity is largest.
[0069] In a case where (each) oil pump 32 is drivingly controlled
so that oil suction supply quantities Q by means of oil pumps 32 of
the left and right in-wheel motor units are maintained at constant
flow quantities Qconst, oil levels 31a at the lower parts within
the left and right in-wheel motor units are continued to be the
same even during the operations of oil pumps 32 due to the same
static oil levels at the lower parts of left and right in-wheel
motor units as described above.
[0070] Since oil levels 31a at the lower parts of left and right
in-wheel motor units are maintained at the same level even during
the operation of oil pumps 32, the stirring resistances to rotor 7
within the left and right in-wheel motor units in the high vehicle
speed region (VSP.gtoreq.VSP1) exceeding the allowance level are
maintained to be the same so that the driving force difference
between the left and right road wheels is not generated and the
above-described problem of worsening the traveling stability can be
avoided.
[0071] In addition, since constant flow quantity Qconst described
above shown in FIG. 5 is a minimum unit demanded oil quantity
required to lubricate speed reduction gear set 5 within each of the
in-wheel motor units. Hence, while speed reduction gear set 5 is
lubricated as demanded by a minimum oil required to lubricate speed
reduction gear set 5 (a minimum pump consumption electric power)
within each of the in-wheel motor units, the above-described
problem can be achieved.
[0072] In a case where the vehicle speed (VSP) is determined to be
in a low vehicle speed region (VSP<VSP1) at step S11 of FIG. 3,
control is advanced to a step S13 which corresponds to the oil pump
driving control means according to the present invention and (each)
oil pump 32 is under a variable flow quantity control as will be
described hereinbelow.
[0073] The reason is that, in a case of the vehicle speed which is
in the low vehicle speed region (VSP<VSP1), the rotational speed
of rotor 7 is slow and the oil stirring resistance is equal to or
below the allowance level, so that the problem on the traveling
stability described above is not generated. In addition, the reason
is that a degree of lubrication demand is low so that, from the
viewpoint of the electric power consumption and the oil pump noise
as will be described later, the operation of oil pump(s) 32 is
avoided as least as possible or the number of rotations of the oil
pump(s) is suppressed as low as possible.
[0074] Hereinafter, the oil pump noise will be explained. Each oil
pump 32 is not installed at the inner part of the vehicle body in
which the noise countermeasure is possible but installed in the
in-wheel motor unit exposed to the outside of the vehicle body.
Hence, the noise countermeasure is impossible or difficult to be
attained. Especially, during a vehicle stop in which the in-wheel
motor driven vehicle is in a stopped state in which no sound state
occurs or in a low vehicle speed region (VSP<VSP1) in which no
sound traveling occurs, the operation sound of oil pump(s) 32 gives
a sound having the sense of discomfort for persons surrounding the
outside of the vehicle. Hence, the rotation speed of (each) oil
pump 32 is reduced as low as possible and it is preferable to make
(each) oil pump 32 in a non-operation state as least as possible.
From the viewpoint of the traveling distance per unit power
(electric power consumption), it is preferable to do so.
[0075] Therefore, in the variable flow quantity control of (each)
oil pump 32 in the low vehicle speed region (VSP<VSP1) executed
at step S13, in a case where demanded driving torque Td is 0 and
traveling distance L is 0 in the oil pump stopped state, as denoted
as a solid line characteristic (basic characteristic) at the low
vehicle speed region (VSP<VSP1), (each) oil suction and supply
quantity Q by means of (corresponding) oil pump 32 is set to 0 to
keep (each) oil pump 32 in a stopped state until vehicle speed VSP
is raised to an oil pump activation vehicle speed VSP0 (corresponds
to a predetermined vehicle speed according to the present
invention). During a time duration at which vehicle speed VSP is
raised from oil pump activation vehicle speed VSP0 to reach to set
vehicle speed VSP1, (each) oil pump 32 is drivingly controlled for
oil suction supply quantity Q to be increased from zero to constant
flow quantity Qconst gradually in a second order curved line
shape.
[0076] Since, as appreciated from above-described constant flow
quantity Qconst, oil levels 31a at the lower parts of left and
right in-wheel motor units are made equal to each other, the oil
suction and supply quantity of (each) oil pump 32 (a predetermined
quantity according to the present invention) and make correspondent
on the minimum unit demanded (required) oil quantity required to
lubricate speed reduction gear set 5 within the in-wheel motor unit
as will be described hereinabove.
[0077] When the above-described drive control of oil pump(s) 32 in
the low vehicle speed region (VSP<VSP1) is carried out, oil pump
controller 51 determines oil pump target rotation speed Nop to
achieve oil suction supply quantity Q which is varied from zero to
constant flow quantity Qconst as described above in the same
thinking as described above with reference to FIG. 7 and commanded
to oil pump suction and supply quantity as shown in FIG. 1.
According to the driving control described above, regardless of oil
temperature Temp, (each) oil pump 32 can be controlled along a
characteristic denoted by a solid line in FIG. 5 in the low vehicle
speed region (VSP<VSP1).
[0078] It should, herein, be noted that oil pump activation vehicle
speed VSP0 is defined as a vehicle speed when a remaining oil
stored within a lubrication oil passage (oil suction and supply
passage) from oil gallery 34 to oil injection hole 44 is started to
be injected by means of a centrifugal force in response to the
start of the road wheel drive through the in-wheel motor unit and
the remaining oil has all disappeared or defined as the vehicle
speed when the remaining oil becomes a quantity below a
predetermined quantity to generate a failure in a lubrication (in
this specification, referred to as a vehicle speed at which the
remaining oil becomes disappeared).
The reason is that, if (each) oil pump 32 is left stopped even
after reaching to oil pump activation vehicle speed VSP0 defined as
described above, the lubrication oil to speed reduction gear set 5
is temporarily not supplied and there is a possibility of
introducing a temporary failure in speed reduction gear set 5.
[0079] However, when demanded driving torque Td becomes larger than
0, demanded lubrication oil quantity of speed reduction gear set 5
becomes increased, oil pump activation vehicle speed VSP0 is
reduced as shown in a broken line characteristic in FIG. 5, and it
becomes necessary to activate (each) oil pump 32 at an early
timing. For example, when, so-called, a hill hold occurs at which
the vehicle is stopped according to a torque of electrically driven
motor 4 when the vehicle is traveling on an ascending slope, speed
reduction gear set 5 is in the torque transmission state. Hence, it
is necessary to lubricate speed reduction gear set 5. Even if
vehicle speed VSP is in the vehicle stopped state, the demanded
lubrication oil quantity of speed reduction gear set 5 is as
denoted by Qo shown in FIG. 5 even if vehicle speed VSP is in the
stopped state of 0.
[0080] In this embodiment, as a map related to a reduction margin
of oil pump activation vehicle speed VSP0 shown by .DELTA.VSP0 in
FIG. 5, a map related to reduction margin .DELTA.VSP0 of oil pump
activation vehicle speed VSP0 which becomes large, for example, as
shown in FIG. 8, in accordance with an increase in an integrated
value .SIGMA.Td of demanded driving torque Td is previously
determined by experiments or so and prepared.
It should be noted that reduction margin LVSP0 of oil pump
activation vehicle speed VSP0 has a maximum value .alpha. is VSP0
as apparent from FIG. 5 and the map in FIG. 8 means that oil pump
activation vehicle speed VSP0 provides 0 since .DELTA.VSP0=.alpha.
when integration value .SIGMA.Td of the demanded driving torque is
equal to or larger than a certain value (set torque) .SIGMA.Tdm and
(each) oil pump 32 is driven from the vehicle stopped state to
enable a satisfaction of the demand when, for example, the
hill-hold occurs, as described above.
[0081] Oil pump controller 51 executes the driving control for
(corresponding) oil pump 32 such that oil suction and supply
quantity Q is varied along a solid line characteristic in FIG. 5
according to the above-described control in a case where
integration value .SIGMA.Td of demanded driving torque Td is 0,
when executing step S13 in FIG. 3 in the low vehicle speed region
(VSP<VSP1).
However, if integration value .SIGMA.Td of demanded driving torque
Td exceeds 0, reduction margin .DELTA.VSP0 of oil pump activation
vehicle speed VSP0 which accords with integration value .SIGMA.Td
of demanded driving torque Td from the map shown in FIG. 8 is
determined and (each) oil pump 32 is drivingly controlled so as to
achieve the variation characteristic of oil suction and supply
quantity Q as denoted by a broken line in FIG. 5 so that
(VSP0-.DELTA.VSP0) is the new oil pump activation vehicle speed
when .SIGMA.Td>0.
[0082] On the other hand, if traveling distance L in the oil pump
stopped state becomes larger than 0 due to the start of the
vehicle, the remaining oil quantity is reduced due to the injection
according to the centrifugal force and becomes disappeared to a
degree such that the lubrication failure of the in-wheel motor unit
occurs. Hence, oil pump activation vehicle speed VSP0 is reduced as
denoted by the broken line characteristic in FIG. 5 in accordance
with traveling distance L in the oil pump stopped state and it is
necessary to activate (each) oil pump 32 when the remaining oil
quantity becomes disappeared (empty).
[0083] In this embodiment, the map related to reduction margin VSP0
of oil pump activation vehicle speed VSP0 which becomes large as
shown in, for example, FIG. 9 in accordance with the increase in
traveling distance L in the oil pump stopped state is previously
determined according to the experiments or so on and prepared.
It should be noted that the map shown in FIG. 9 means that oil
pump(s) 32 is driven when oil pump activation vehicle speed VSP0
provides 0 since .DELTA.VSP0=.alpha. when traveling distance L in
the oil pump stopped state is equal to or larger than a certain
value Lm. Thus, regardless of the nullification of the remaining
oil described above due to the fact that L.gtoreq.Lm and, in spite
of the fact that traveling distance is equal to or below a
predetermined quantity, oil pump(s) 32 is left in the non-operation
state so that the in-wheel motor unit(s) does not fall in the
lubrication failure state.
[0084] Then, oil pump controller 51 executes step S13 in FIG. 3 in
the low vehicle speed region (VSP<VSP1) to drivingly control oil
pump(s) 32 in accordance with traveling distance L in the oil pump
stopped state. This is executed in the following way on a basis of
FIG. 4.
[0085] At a step S21 in FIG. 4, oil pump controller 51 determines a
traveling distance L in the oil pump stopped state by a time
integration of vehicle speed VSP during the traveling of the oil
pump stopped state.
As shown in FIG. 10, in a two dimensional coordinate with a
traveling time in the oil pump stopped state taken as a lateral
axis and with a time integration value of vehicle speed VSP during
the traveling time in the oil pump stopped state taken as a
longitudinal axis, the time integration value of vehicle speed VSP
at a time of traveling time in the oil pump stopped state is
denoted by an area of hatching in FIG. 10 and represents traveling
distance L in the oil pump stopped state. The area illustrated by
hatching in FIG. 10 denotes a case where traveling distance L in
the oil pump stopped state is Lm in FIG. 9.
[0086] At the next step S23, oil pump controller 51 subtracts
reduction margin .DELTA.VSP0 from oil pump activation vehicle speed
VSP0 from basic oil pump activation vehicle speed VSP0 shown in
FIG. 5 to determine a new oil pump activation vehicle speed VSP0
(=VSP0-.DELTA.VSP0) which accords with traveling distance L in the
oil pump stopped state.
[0087] At a step S24, oil pump controller 51 determines whether
vehicle speed VSP is equal to or below oil pump activation vehicle
speed VSP0 (=VSP0-.DELTA.VSP0) corresponding to traveling distance
L or in excess of oil pump activation vehicle speed VSP0
(=VSP0-.DELTA.VSP0).
If VSP.ltoreq.VSP0, oil pump controller 51 stops oil pump(s) 32 by
determining oil suction and supply quantity Q to be zero at a step
S25. If VSP<VSP0, at a step S26, oil pump controller 51 searches
and determines oil suction and supply quantity Q by means of
corresponding oil pump 32 which accords with present vehicle speed
VSP from the oil suction and supply quantity characteristic Q by
means of corresponding oil pump 32 so that corresponding oil pump
32 is driven to achieve oil suction and supply quantity Q.
[0088] As described hereinabove, oil pump(s) 32 is drivingly
controlled to achieve the oil suction and supply quantity
(quantities) in accordance with traveling distance L in the oil
pump stopped state in the low vehicle speed region (VSP<VSP1) in
FIG. 5 when the oil pump driving control shown in FIG. 4 is carried
out.
Hence, during a time duration from the time at which the vehicle is
started in the oil pump stopped state to the time at which the
vehicle speed reaches to predetermined vehicle speed VSP0 (which is
different according to traveling distance L in the oil pump stopped
state and VSP0=0 when L.gtoreq.Lm) at which the remaining oil is
scattered in all directions and becomes disappeared, oil pump(s) 32
is stopped and oil pump(s) 32 can be activated when reaching to the
predetermined vehicle speed (VSP0) at which the remaining oil is
scattered in all directions and becomes disappeared.
[0089] <Effect of the First Embodiment>
[0090] In the lubrication control of the in-wheel motor unit(s)
carried out in this embodiment, oil pump(s) 32 is left stopped
during the time duration from the time at which the vehicle is
started to be traveled in the oil pump stopped state as described
above to the time at which the vehicle speed reaches to
predetermined vehicle speed VSP0 at which the remaining oil is
scattered in all directions and becomes disappeared. Hence, an
wasteful operation of oil pump(s) 32 can be prevented in the low
vehicle speed region equal to or below predetermined vehicle speed
VSP0 including the stop of the vehicle.
[0091] Hence, the operation sound of oil pump(s) 32 can be avoided
from being noisy sound during the vehicle stop or in the low
vehicle speed region which is in the no sound state or in almost no
sound travel. In addition, the worsening of the traveling distance
per unit power (electric power consumption) due to the wasteful
operation of oil pump(s) 32 during the vehicle stop or in the low
vehicle speed region can be avoided.
[0092] On the other hand, when vehicle speed VSP has reached to
predetermined vehicle speed VSP0, oil pump(s) 32 is activated.
Hence, a lubrication failure of the corresponding in-wheel motor
unit can be prevented from occurring since there are no cases where
oil pump(s) 32 are not activated in spite of the fact that the
remaining oil in the oil suction and supply passage is scattered in
all directions and becomes disappeared.
[0093] Then, since the oil pump activation vehicle speed is reduced
in accordance with traveling distance L in the oil pump stopped
state, oil pump(s) 32 is activated at the vehicle speed lower than
a basic oil pump activation vehicle speed VSP0 shown in FIG. 5 and
the following effects can be achieved.
[0094] In other words, if traveling distance L of the vehicle in
the oil pump stopped state becomes long, the remaining oil within
the oil suction and supply passage becomes slightly scattered in
all directions and at last becomes disappeared due to the
continuation of the slight scattering by means of a small
centrifugal force so that the corresponding in-wheel motor unit
cannot be lubricated any more as desired even in the vehicle speed
further lower than basic oil pump activation vehicle speed VSP0
shown in FIG. 5
[0095] However, as described above in this embodiment, when
traveling distance L of the vehicle in the oil pump stopped state
is long, oil pump(s) 32 is activated at the vehicle speed lower
than basic oil pump activation vehicle speed VSP0 shown in FIG. 5.
Hence, an event of the lubrication failure which is generated in a
case where traveling distance L of the vehicle in the oil pump
stopped state is long can be avoided.
[0096] In this embodiment, since traveling distance L in the oil
pump stopped state is determined according to the time integration
of vehicle speed VSP during the traveling in the oil pump stopped
state as described above with reference to FIG. 10 at step S21 in
FIG. 4. Hence, a traveling distance meter (odometer) to measure
traveling distance L is not needed and is very advantageous in
terms of cost.
[0097] Furthermore, after the vehicle speed has reached to
predetermined vehicle speed VSP0, oil pump(s) 32 is drivingly
controlled so that oil suction and supply quantity Q from
(corresponding) oil pump 32 is gradually increased in accordance
with the rise in vehicle speed VSP in the low vehicle speed region
below set vehicle speed VSP1 at which the stirring resistance of
oil 31 at the lower part within the in-wheel motor unit case is not
in excess of the allowance level. Hence, an abrupt increase of the
pump driving load after the activation of oil pump(s) 32 can be
avoided so that the worsening of the durability of oil pump(s) 32
can be prevented.
[0098] In addition, oil pump(s) 32 is drivingly controlled in such
a way that oil suction and supply quantity Q at a time of rise in
vehicle speed VSP to reach to set vehicle speed VSP1 provides
predetermined quantity Qconst which give the oil levels is mutually
at the same level as for the lower parts of the left and right
in-wheel motor units. Hence, during a transfer from the low vehicle
speed region (VSP<VSP1) to the high vehicle speed region
(VSP.gtoreq.VSP1), the oil levels at the lower parts within the
cases of the left and right in-wheel motor units can be set to be
equal to each other. Thus, the problem such that a large left and
right road wheel driving force difference is generated at the time
of the transfer to the high vehicle speed region (VSP.gtoreq.VSP1)
to worsen the traveling (running) stability can be avoided.
[0099] In the high speed region (VSP.gtoreq.VSP1) of the vehicle
speed, oil pumps 32 are drivingly controlled for oil suction and
supply quantity (quantities) Q to be maintained at above-described
predetermined quantity (quantities) Qconst. Hence, even during the
operation of oil pump(s) 32, oil levels 31a at the lower parts
within the left and right in-wheel motor units can be maintained at
the same level even during the operation of oil pump(s) 32.
Hence, even if the oil stirring resistance to rotor 7 is in the
high vehicle speed region (VSP.gtoreq.VSP1) exceeding the allowance
level, the oil stirring resistance to rotor 7 within the left and
right in-wheel motor units is maintained at the same value so that
the driving force difference between the left and right road wheels
is not generated and the problem such that the traveling stability
of the vehicle becomes worsened can be avoided. Then, since this
effect is achieved through the simple constant flow quantity
control by means of (each) oil pump 32, it is considerably
advantageous in terms of cost.
[0100] In addition, above-described constant flow quantity Qconst
in FIG. 5 provides the minimum unit required oil quantity required
to lubricate speed reduction gear set 5 within the corresponding
in-wheel motor unit. Hence, while speed reduction gear set 5 is
lubricated with minimum oil as required (a minimum pump consumption
power), the above-described effect can be achieved.
Structure of a Second Embodiment
[0101] Next, referring to FIG. 11, a second preferred embodiment
according to the present invention will be described with reference
to FIGS. 1 to 10. It should be noted that the explanation of a part
or parts common to the above-described first embodiment will
suitably be omitted.
[0102] In this second embodiment, above-described setting torque
.SIGMA.Tdm is a lower limitation value of demanded driving torque
Td required to activate (each) oil pump 32 from the vehicle stopped
state. Since .SIGMA.Td.gtoreq..SIGMA.Tdm, oil suction and supply
quantity Q.sub.0 during the vehicle stopped state shown in FIG. 5
in a case where oil pump(s) 32 is activated from the vehicle
stopped state is made correspondence to the lubrication oil
quantity required for the in-wheel motor unit due to the presence
of demanded driving torque Td at the time of the vehicle stopped
state. Thus, as demanded driving torque Td (its integration value
.SIGMA.Td) becomes larger (in more details, as a torque difference
.SIGMA.Td-.SIGMA.Tdm becomes larger), oil suction and supply
quantity Q.sub.0 at the time of the stop of the vehicle shown in
FIG. 5 becomes increased due to the presence of demanded driving
torque Td at the time of the vehicle stop.
[0103] Oil pump controller 51 executes step S13 in FIG. 3 in the
low vehicle speed region (VSP<VSP1) to perform the driving
control of oil pump(s) 32 in the second embodiment in accordance
with integration value .SIGMA.Td of demanded driving torque Td. At
this time, the following is executed on a basis of FIG. 11.
[0104] At a step S31 in FIG. 11, demanded driving torque Td is
integrated with respect to time when the traveling in the oil pump
stopped state is started to determine integrated value .SIGMA.Td of
demanded driving torque Td.
At the next step S32, on a basis of the map corresponding to FIG.
8, reduction margin .DELTA.VSP0 of oil pump activation vehicle
speed VSP0 is searched from time integration value of .SIGMA.Td of
demanded deriving torque Td determined at step S31.
[0105] At the next step S33, oil pump controller 51 subtracts
above-described basic reduction margin .DELTA.VSP0 from basic oil
pump activation vehicle speed VSP0 shown in FIG. 5 to determine a
new oil pump activation vehicle speed VSP0 (=VSP0-.DELTA.VSP0)
which accords with time integration value .SIGMA.Td of demanded
driving torque Td.
[0106] At the next step S34, oil pump controller 51 checks to see
whether a new oil pump activation vehicle speed VSP0
(=VSP0-.DELTA.VSP0) in accordance with time integration value of
.SIGMA.Td of demanded driving torque Td is "0" or larger than
"0".
If VSP0 (=VSP0-.DELTA.VSP0) is "0", the routine goes to a step S35.
At step S35, oil pump controller 51 searches and determines oil
suction and supply quantity Q.sub.0 (refer to FIG. 5) which accords
with demanded driving torque Td (or its integration value
.SIGMA.Td) for the case when VSP0=0 and oil pump(s) 32 is drivingly
controlled to achieve Q=Q.sub.0.
[0107] In a case where a new oil pump activation vehicle speed VSP0
(=VSP0-.DELTA.VSP0) which accords with time integration value
.SIGMA.Td of demanded driving torque Td is determined to be larger
than "0" at step S34, the routine goes to a step S36. At step S36,
oil pump controller 51 checks to see whether vehicle speed VSP is
equal to or below new oil pump activation vehicle speed VSP0
(=VSP0-.DELTA.VSP0) which accords with time integration value
.SIGMA.Td of demanded driving torque Td or higher than new oil pump
activation vehicle speed VSP0.
[0108] At step S36, if vehicle speed VSP is determined to be higher
than new oil pump activation vehicle speed VSP0 (=VSP-.DELTA.VSP0)
which accords with time integration value .SIGMA.Td of demanded
driving torque Td, the vehicle speed is before the oil pump
activation as appreciated from FIG. 5. At a step S37, when oil
suction and supply quantity Q by means of oil pump(s) 32 is
determined as 0 to stop oil pump (s) 32.
[0109] In a case where vehicle speed VSP is determined to be higher
than new oil pump activation vehicle speed VSP0 (=VSP0-.DELTA.VSP0)
which accords with time integration value .SIGMA.Td of demanded
driving torque Td, the vehicle speed is the vehicle speed after the
oil pump activation as appreciated from FIG. 5. Hence, at a step
S38, oil pump suction and supply quantity Q by means of
(corresponding) oil pump 32 is determined as the oil suction and
supply quantity corresponding to vehicle speed VSP and
(corresponding) oil pump 32 is drivingly controlled for oil suction
and supply quantity Q corresponding to vehicle speed VSP to be
achieved.
[0110] As described hereinabove, when the driving control of oil
pump(s) 32 shown in FIG. 11 which accords with demanded driving
torque Td (time integration value .SIGMA.Td) is executed, oil
pump(s) 32 is drivingly controlled so that the oil suction and
supply quantity characteristic in the low vehicle speed region
(VSP<VSP1) shown in FIG. 5 is varied sequentially from a solid
line characteristic to broken line characteristics at the left side
of FIG. 5 as demanded driving torque Td (time integration value
.SIGMA.Td) becomes larger from zero to achieve the oil suction and
supply quantity characteristic which accords with demanded driving
torque Td (time integration value .SIGMA.Td).
[0111] That is to say, in a case where integration value .SIGMA.Td
of demanded driving torque indicates 0, oil pump(s) 32 is drivingly
controlled for oil suction and supply quantity Q to be varied along
the solid line characteristic of FIG. 5 in a case where integration
value .SIGMA.Td of demanded driving torque Td is 0 and, in a case
where integration value .SIGMA.Td of demanded driving torque Td is
in excess of 0, oil pump controller 51 determines reduction margin
.DELTA.VSP0 of oil pump activation vehicle speed VSP0 in accordance
with integration value .SIGMA.Td of demanded driving torque Td from
the map shown in FIG. 8 and performs the driving control of oil
pump(s) 32 to achieve the variation characteristic of oil suction
and supply quantity Q as illustrated in the broken line in FIG. 5
with (VSP0-.DELTA.VSP0) as the new oil pump activation vehicle
speed when .SIGMA.Td>0.
[0112] <Effect of the Second Embodiment>
[0113] In the second embodiment, in a case where demanded driving
torque Td of the vehicle is present, oil pump(s) 32 are activated
from the vehicle speed lower than predetermined vehicle speed VSP0
including the stop of the vehicle in accordance with demanded
driving torque Td (its integration value .SIGMA.Td) irrespective of
the vehicle speed rise condition (VSP.gtoreq.VSP0). Hence, oil
pump(s) 32 can suck and supply oil having a quantity responding to
a degree of demand of the lubrication of the in-wheel motor unit
which becomes higher in accordance with demanded driving torque Td
(its integration value .SIGMA.Td). Hence, the problem such that the
oil quantity of the lubrication becomes insufficient for demanded
driving torque Td is not generated so that the lubrication as
demanded can be performed which accords with demanded driving
torque Td.
[0114] In addition, in this embodiment, the driving control of the
oil pumps) 32 in accordance with demanded driving torque Td (its
time integration value .SIGMA.Td) is performed by reducing
predetermined vehicle speed VSP0 to activate oil pump(s) 32 as
demanded driving torque Td (its time integration value .SIGMA.Td)
becomes larger and setting predetermined vehicle speed VSP0 to zero
when demanded driving torque Td (its time integration value
.SIGMA.Td) is equal to or larger than set torque .SIGMA.Tdm. Hence,
a control accuracy can be increased and the above-described effects
can further be remarkable according to the control with
predetermined vehicle speed VSP0 as a reference.
[0115] Furthermore, in a case where, in response to a case where
.SIGMA.Td.gtoreq..SIGMA.Tdm, oil pump(s) 32 is activated from the
vehicle stopped state, oil suction and supply quantity Q.sub.0
(refer to FIG. 5) in a case where (each) oil pump 32 is activated
from the vehicle stopped state is defined to be larger in
accordance with a magnitude of an excessive quantity of demanded
driving torque .SIGMA.Td with respect to setting torque .SIGMA.Tdm.
Hence, the demanded oil suction and supply quantity at the time of
the vehicle stop in accordance with demanded driving torque Td (its
integration value .SIGMA.Td) is achieved. Thus, in a case where the
lubrication oil quantity becomes insufficient with respect to
demanded driving torque Td. Thus, during the hill-hold driving of
the vehicle, the lubrication as demanded in accordance with
demanded driving torque Td can be performed.
[0116] In addition, when the lubrication control in accordance with
above-described demanded driving torque Td is performed, in place
of demanded driving torque Td itself, oil pump(s) 32 using time
integration value .SIGMA.Td is drivingly controlled as described
above. Hence, this control becomes more practical so that the
above-described effect can be assured.
[0117] Furthermore, after the vehicle speed has reached to
predetermined vehicle speed VSP0, as shown in FIG. 5, oil pump(s)
32 is drivingly controlled so as to be gradually increased as the
rise in vehicle speed VSP of oil suction and supply quantity Q from
(each) oil pump 32 in a low speed region lower than a set vehicle
speed VSP1 at which the stirring resistance of oil 31 at a lower
part of in-wheel motor unit case. Thus, the abrupt increase in the
pump driving load after the activation of (each) oil pump 32 can be
avoided and the worsening of the durability of (each) oil pump 32
can be prevented.
[0118] In addition, oil pump(s) 32 is drivingly controlled for oil
suction and supply quantity Q to be the constant quantity Qconst by
which the oil levels at the lower parts of the left and right
in-wheel motor units are made equal to each other when the vehicle
speed is increased and has reached to set vehicle speed VSP1.
Hence, during the transition of the vehicle speed from low vehicle
speed region (VSP<VSP1) to high vehicle speed region
(VSP.gtoreq.VSP1), the oil levels at the lower parts of the left
and right in-wheel motor unit cases can be set to mutually be the
same so that the problem such that the large left and right road
wheel driving force differences are generated and the traveling
stability is worsened at the time of the transition to high vehicle
speed driving region (VSP.gtoreq.VSP1) of the vehicle speed can be
avoided.
[0119] Then, in the high vehicle speed region (VSP.gtoreq.VSP1),
oil pump(s) 32 is drivingly controlled to maintain oil suction and
supply quantity Q at predetermined quantity
[0120] Qconst so that, even during the operation of (each) oil pump
32, oil levels 31a at the lower parts of the left and right
in-wheel motor units are continued to remain the same. Hence, even
if the vehicle speed is in the high vehicle speed region
(VSP.gtoreq.VSP1) at which each of the oil stirring resistances to
rotor 7 exceeds the allowance level, the oil stirring resistances
to rotor 7 within the left and right in-wheel motor units are
maintained to be the same. Thus, the driving force difference
between the left and right road wheels is not generated and the
problem such that the traveling stability of the vehicle becomes
worsened can be avoided.
Then, its effect can be achieved by the simple constant flow
quantity control of oil pump(s) 32 and, therefore, it is
considerably advantageous in terms of cost.
[0121] In this addition, above-described constant flow quantity
Qconst in FIG. 5 is the minimum unit required oil quantity required
to lubricate speed reduction gear set 5 within each of the in-wheel
motor units. Hence, while speed reduction gear set 5 is lubricated
as requested by a minimum oil (a minimum pump consumed electric
power), the above-described effect can be achieved.
Other Embodiments
[0122] It goes without saying that although, in the above-described
embodiment, when the above-described control is executed, time
integration value .SIGMA.Td is used in place of demanded driving
torque Td itself, demanded driving torque Td itself may be
used.
[0123] In addition, in the above-described embodiment, basic
predetermined vehicle speed VSP0 to activate oil pump(s) 32 is
predefined as an initial value as shown in FIG. 5 and this
predetermined vehicle speed VSP0 is reduced by quantity .DELTA.VSP0
shown in FIG. 8 which accords with a magnitude of demanded driving
torque Td (its time integration value .SIGMA.Td). However, oil
pump(s) 32 may be activated when demanded driving torque Td (its
integration value .SIGMA.Td) indicates a predetermined value.
* * * * *