U.S. patent application number 14/434419 was filed with the patent office on 2016-08-11 for control device for a hybrid vehicle.
The applicant listed for this patent is Nissan Motor Co., Ltd.. Invention is credited to Morihiro NAGAMINE, Shunsuke SHIGEMOTO.
Application Number | 20160229391 14/434419 |
Document ID | / |
Family ID | 50731049 |
Filed Date | 2016-08-11 |
United States Patent
Application |
20160229391 |
Kind Code |
A1 |
SHIGEMOTO; Shunsuke ; et
al. |
August 11, 2016 |
CONTROL DEVICE FOR A HYBRID VEHICLE
Abstract
A control device in a hybrid vehicle includes a controller
capable of switching, between an operating state and a
non-operating state, a fuel-cut recovery control in which engine
rotation speed is kept at or above a predetermined rotation speed
by starting supply of fuel upon the engine rotation speed falling
to the predetermined rotation speed from a state in which the
engine rotation speed is higher than the predetermined rotation
speed and the supply of fuel is stopped.
Inventors: |
SHIGEMOTO; Shunsuke;
(Isehara-shi, Kanagawa, JP) ; NAGAMINE; Morihiro;
(Setagaya-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nissan Motor Co., Ltd. |
Yokohama-shi, Kanagawa |
|
JP |
|
|
Family ID: |
50731049 |
Appl. No.: |
14/434419 |
Filed: |
October 30, 2013 |
PCT Filed: |
October 30, 2013 |
PCT NO: |
PCT/JP2013/079423 |
371 Date: |
April 9, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10S 903/93 20130101;
Y02T 10/72 20130101; B60L 15/2054 20130101; B60W 20/30 20130101;
Y02T 10/7072 20130101; B60W 2540/12 20130101; B60W 10/18 20130101;
F02D 29/02 20130101; B60W 10/06 20130101; F02D 41/126 20130101;
Y10S 903/947 20130101; B60W 10/02 20130101; B60W 20/14 20160101;
B60W 10/107 20130101; B60L 2240/507 20130101; B60L 50/16 20190201;
B60W 30/18127 20130101; B60K 6/387 20130101; B60W 2710/0644
20130101; F02N 11/0822 20130101; Y02T 10/70 20130101; B60W 10/08
20130101; Y02T 10/62 20130101; Y02T 10/64 20130101; B60K 6/48
20130101; B60K 6/543 20130101; B60Y 2200/92 20130101; Y02T 10/40
20130101; B60W 2710/1005 20130101; B60L 7/24 20130101; B60L
2240/423 20130101; B60L 2240/486 20130101; B60W 20/00 20130101;
F02N 2200/102 20130101; B60L 15/2009 20130101 |
International
Class: |
B60W 20/14 20060101
B60W020/14; B60W 10/02 20060101 B60W010/02; B60W 10/06 20060101
B60W010/06; B60K 6/387 20060101 B60K006/387; B60W 10/18 20060101
B60W010/18; B60W 20/30 20060101 B60W020/30; B60K 6/543 20060101
B60K006/543; B60W 10/107 20060101 B60W010/107; B60W 10/08 20060101
B60W010/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2012 |
JP |
2012-251776 |
Claims
1. A control device for a hybrid vehicle, comprising: a
continuously variable transmission coupled to an output shaft of an
engine; a clutch interposed between the transmission and a drive
wheel; a motor coupled to the drive wheel; a boosting configured to
use a negative pressure of the engine to assist a
brake-pedal-depressing force applied by a driver; and a controller
programmed to control an output state of the engine and the motor,
a gear speed ratio of the transmission, and engaging and releasing
of the clutch according to an operation state the controller
programmed to switch, between an operating state and a
non-operating state, a fuel-cut recovery control in which the
engine rotation speed is kept at or above a predetermined rotation
speed by starting supply of fuel upon the engine rotation speed
falling to the predetermined rotation speed from a state in which
the engine rotation speed is higher than the predetermined rotation
speed and the supply of fuel is stopped; a deceleration
regeneration mode being a mode in which, when the vehicle
decelerates from a high-vehicle-speed state higher than a
predetermined vehicle speed to a vehicle speed equal to or lower
than the predetermined vehicle speed with the clutch in an engaged
state, the clutch is switched from an engaged state to a released
state and a regenerative torque is imparted by the motor to the
drive wheel; and when the deceleration regeneration mode is set,
the fuel-cut recovery control is switched to the operating state
prior to the clutch being switched from an engaged state to a
released state, and the engine rotation speed being kept at or
above the predetermined rotation speed.
2. The hybrid vehicle control device according to claim 1, further
comprising a brake request detection device configured to detect
whether or not a brake request made by the driver is satisfied; the
controller, upon the brake request detection device detecting that
the brake request is satisfied when the engine rotation speed is
kept at or above the predetermined rotation speed, is programmed to
reduce the engine rotation speed to below the predetermined
rotation speed.
3. The hybrid vehicle control device according to claim 2, wherein
the controller is programmed to switch the clutch from a released
state to an engaged state when the braking force required by the
driver is equal to or greater than a predetermined value while the
engine rotation speed is reduced to below the predetermined
rotation speed.
4. The hybrid vehicle control device according to claim 2, wherein
the controller is programmed to increase the engine rotation speed
to or above the predetermined rotation speed when the braking
requested by the driver is equal to or greater than a predetermined
braking force while the engine rotation speed is reduced to below
the predetermined rotation speed.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. National stage application of
International Application No. PCT/JP2013/079423, filed Oct. 30,
2013, which claims priority to JP Patent Application No.
2012-251776 filed on Nov. 16, 2012, the contents of each of which
are hereby incorporated herein by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a control device for a
hybrid vehicle that has an engine and an electric motor mounted
thereon as power sources, the device making it possible to select
between an electric travel mode (EV mode), in which traveling is
performed using the electric motor only, and a hybrid travel mode
(HEV mode), in which traveling is performed using the electric
motor and the engine.
[0004] 2. Background Information
[0005] Conventionally known hybrid vehicles of such description
include the type disclosed in Japanese Laid-Open Patent Application
No. 2002-139136, in which an engine, which is one of the power
sources, is decouplably drive-coupled to a wheel by a continuously
variable transmission and a clutch, and an electric motor, which is
the other power source, is permanently coupled to the wheel.
[0006] In this hybrid vehicle, when the accelerator pedal is
released and the vehicle speed is equal to or less than a
predetermined vehicle speed, stopping the engine and releasing the
clutch make it possible to perform regenerative travel (EV travel)
in EV mode in which only the electric motor is used. Releasing the
clutch as described above during EV travel decouples the engine in
a stopped state (as well as the transmission, if present) from the
wheels and prevents the engine (transmission) from being dragged
(caused to co-rotate) during regenerative travel in EV mode, making
it possible to prevent the corresponding energy loss and improve
energy efficiency.
SUMMARY
[0007] In the technique disclosed in Japanese Laid-Open Patent
Application No. 2002-139136, if a predetermined vehicle speed that
is a threshold value at which the engine is stopped is set in a
high-vehicle-speed region, the time taken for the vehicle to come
to a stop increases, creating the possibility of the driver
repeating the operation of depressing and easing the brake pedal in
the meantime. When the braking operation is repeated in a state in
which the engine is stopped, the negative pressure of the brake
booster (boosting means or device) decreases, increasing the risk
of producing a state in which the brake pedal cannot be
significantly depressed and the driver is imparted with a sense of
unease.
[0008] With a focus on the abovementioned problem, an object of the
present invention is to provide a control device for a hybrid
vehicle capable of preventing a sense of unease from being imparted
to the driver even when a brake pedal is operated, while a clutch
between an engine and a drive wheel is released and the vehicle is
decelerating.
[0009] In order to achieve the above object, the present invention
is a hybrid vehicle provided with a negative pressure brake booster
for using a negative pressure of an engine to assist the
brake-pedal-depressing force applied by the driver using, wherein
when a clutch disposed between an engine and a drive wheel is to be
released and a regenerative torque is to be applied to the drive
wheel using an electric motor, a fuel cut recover control is
switched to an operational state prior to the clutch being released
and the engine rotation speed is maintained at or above a
predetermined rotation speed.
[0010] Specifically, keeping the engine rotation speed at or above
a predetermined rotation speed ensures a negative pressure, and
even if the driver repeats the brake pedal operation prior to the
vehicle coming to a stop, a boosting device is able to deliver an
assist function, making it possible for the brake pedal to be
depressed. Accordingly, braking can be performed without imparting
the driver with a sense of unease. In addition, since negative
pressure can be obtained, the predetermined vehicle speed Vnew can
be set so as to be relatively high, making it possible to recover
regenerative energy in a more efficient manner. Furthermore, since
it is possible to maintain the rotating state of the continuously
variable transmission and to secure a supply of hydraulic pressure
due to operation of the oil pump, the continuously variable
transmission can be shifted to a desired gear speed ratio, and an
appropriate gear speed ratio can be obtained, e.g., during a
restart or when there is a request for a reacceleration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Referring now to the attached drawings which form a part of
this original disclosure.
[0012] FIG. 1 is a schematic system diagram showing a driving
system and an overall control system of a hybrid vehicle with a
mode switching control device representing a first embodiment of
the present invention;
[0013] FIG. 2A is a schematic system diagram showing a driving
system and an overall control system of another type of hybrid
vehicle to which the regenerative braking control device of the
present invention can be applied
[0014] FIG. 2B is a logic diagram showing the manner in which
transmission friction elements in an auxiliary transmission
provided in a V-belt type continuously variable transmission in a
driving system of the hybrid vehicle of FIG. 2A are engaged;
[0015] FIG. 3 is a time chart showing a control process in the EV
deceleration mode according to the first embodiment;
[0016] FIG. 4 is a time chart showing a control process in the EV
deceleration mode according to a second embodiment;
[0017] FIG. 5 is a time chart showing a control process in the EV
deceleration mode according to a third embodiment; and
[0018] FIG. 6 is a time chart showing a control process in the EV
deceleration mode according to a fourth embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
First Embodiment
[0019] FIG. 1 is a schematic system diagram showing a driving
system and an overall control system of a hybrid vehicle with a
control device according to a first embodiment. The hybrid vehicle
in FIG. 1 has an engine 1 and an electric motor 2 mounted thereon
as drive sources, and the engine 1 is started by a starter motor 3.
The engine 1 is drivingly coupled to a drive wheel 5 by a
V-belt-type continuously variable transmission 4 so as to be
capable of being decoupled as appropriate. An overview of the
V-belt-type continuously variable transmission 4 will now be given
below.
[0020] The V-belt-type continuously variable transmission 4 is a
continuously variable transmission mechanism CVT comprising a
primary pulley 6, a secondary pulley 7, and a V-belt 8 extended
between the pulleys 6, 7. The primary pulley 6 is coupled to a
crank shaft of the engine 1 via a torque converter T/C having a
lock-up clutch. The secondary pulley 7 is coupled to the drive
wheel 5 via a clutch CL and a final gear set 9 in the sequence
mentioned. Thus, in a state in which the clutch CL is engaged,
power from the engine 1 is inputted through the torque converter
T/C into the primary pulley 6, reaches the drive wheel 5 through
the V-belt 8, the secondary pulley 7, the clutch CL, and the final
gear set 9, and contributes towards traveling of the hybrid
vehicle.
[0021] During the transmitting of engine power, reducing the pulley
V-groove width of the primary pulley 6 and increasing the pulley
V-groove width of the secondary pulley 7 results in an increase in
the arc diameter by which the V-belt 8 is wound around the primary
pulley 6 and a reduction in the arc diameter by which the V-belt 8
is wound around the secondary pulley 7, making it possible for the
V-belt-type continuously variable transmission 4 to upshift to a
high-side pulley ratio (high-side gear speed ratio). When the
upshift to a high-side gear speed ratio is performed to the limit,
the gear speed ratio is set to a maximum gear speed ratio.
[0022] Conversely, increasing the pulley V-groove width of the
primary pulley 6 and reducing the pulley V-groove width of the
secondary pulley 7 results in a reduction in the arc diameter by
which the V-belt 8 is wound around the primary pulley 6 and an
increase in the arc diameter by which the V-belt 8 is wound around
the secondary pulley 7, making it possible for the V-belt-type
continuously variable transmission 4 to downshift to a low-side
pulley ratio (low-side gear speed ratio). When the downshift to a
low-side gear speed ratio is performed to the limit, the gear speed
ratio is set to a minimum gear speed ratio.
[0023] The continuously variable transmission 4 has an input
rotation sensor 6a for detecting the rotation speed of the primary
pulley 6 and an output rotation sensor 7a for detecting the
rotation speed of the secondary pulley 7. The actual gear speed
ratio is calculated on the basis of the rotation speeds detected by
the rotation sensors, and the pulleys are hydraulically or
otherwise controlled so that the actual gear speed ratio reaches a
target gear speed ratio.
[0024] The electric motor 2 is permanently coupled to the drive
wheel 5 via a final gear set 11, and the electric motor 2 is driven
via an inverter 13 by power from a battery 12.
[0025] The inverter 13 converts DC power from the battery 12 to AC
power and supplies the AC power to the electric motor 2, and
increases and decreases the power supplied to the electric motor 2
to control the driving force and the rotation direction of the
electric motor 2.
[0026] In addition to the motor driving described above, the
electric motor 2 also functions as a generator, and is also
utilized for regenerative braking described further below. During
regenerative braking, the inverter 13 applies a power generation
load corresponding to the regenerative braking force on the
electric motor 2, whereby the electric motor 2 is made to function
as a power generator and the power generated by the electric motor
2 is stored in the battery 12.
[0027] In the hybrid vehicle according to the first embodiment,
when the electric motor 2 is driven in a state in which the clutch
CL is released and the engine 1 is stopped, only the power from the
electric motor 2 passes through the final gear set 11 and reaches
the drive wheel 5, and [the vehicle] travels in electric travel
mode (EV mode) in which only the electric motor 2 is used for
travel. Keeping the clutch CL released during this period prevents
the engine 1, which is in a stopped state, from being dragged, and
suppressing wasteful power consumption during EV travel.
[0028] When the engine 1 is started using the starter motor 3 and
the clutch CL is engaged in the above EV travel state, power from
the engine 1 sequentially passes through the torque converter T/C,
the primary pulley 6, the V-belt 8, the secondary pulley 7, the
clutch CL, and the final gear set 9 and reaches the drive wheel 5,
and the hybrid vehicle travels in hybrid travel mode (HEV mode) in
which the engine 1 and the electric motor 2 are used for
travel.
[0029] Bringing the hybrid vehicle to a stop from the above travel
state or keeping the vehicle in the stopped state is achieved by
clamping, using a caliper 15, a brake disc 14 which rotates with
the drive wheel 5, and braking the brake disc 14. The caliper 15 is
connected to a master cylinder 18 for outputting a brake liquid
pressure corresponding to the brake-pedal-depressing force through
a negative pressure-type brake booster 17 (corresponding to a
boosting means) in response to the depression force acting on a
brake pedal 16 depressed by the driver. The caliper 15 uses the
brake liquid pressure to cause the caliper 15 to operate and brake
the brake disc 14. The negative pressure-type brake booster 17 uses
the engine 1 intake negative pressure to assist the
brake-pedal-depressing force applied by the driver, and can
sufficiently perform the boosting function if the negative pressure
detected by a negative pressure sensor 17a is equal to or greater
than a predetermined value. In both the EV mode and the HEV mode,
the drive wheel 5 of the hybrid vehicle is driven by a torque
corresponding to a driving force command produced by the driver
depressing an acceleration pedal 19, and the hybrid vehicle is
caused to travel by a driving force corresponding to that requested
by the driver.
[0030] A hybrid controller 21 selects the travel mode of the hybrid
vehicle, controls the output of the engine 1, controls the rotation
direction and the output of the electric motor 2, controls the
shift of the continuously variable transmission 4, controls the
engaging/releasing of the clutch CL, and controls the
charging/discharging of the battery 12. The hybrid controller 21
controls the above elements through a corresponding engine
controller 22, motor controller 23, transmission controller 24, and
battery controller 25.
[0031] Accordingly, a signal from a brake switch 26, which is a
normally open switch that switches from OFF to ON during braking
when the brake pedal 16 is depressed, a signal from a stroke sensor
16a for detecting the stroke amount for the brake pedal 16, and a
signal from an accelerator position sensor 27 for detecting the
accelerator pedal depression amount (accelerator position) APO, are
inputted into the hybrid controller 21. The hybrid controller 21
also exchanges internal information with the engine controller 22,
the motor controller 23, the transmission controller 24, and the
battery controller 25.
[0032] The engine controller 22 controls the output of the engine 1
in response to a command from the hybrid controller 21. The motor
controller 23 controls the rotation direction and the output of the
electric motor 2 through the inverter 13 in response to a command
from the hybrid controller 21. The transmission controller 24
controls the engaging/releasing of the clutch CL and the shift of
the continuously variable transmission 4 (V-belt-type continuously
variable transmission mechanism CVT) using oil from an
engine-driven oil pump O/P in response to a command from the hybrid
controller 21. The battery controller 25 controls the
charging/discharging of the battery 12 in response to a command
from the hybrid controller 21.
[0033] In FIG. 1, a dedicated clutch CL is provided to the
continuously variable transmission 4 in order to decouplably couple
the V-belt-type continuously variable transmission mechanism CVT
(secondary pulley 7) and the drive wheel 5.
[0034] However, if the continuously variable transmission 4 is
internally provided with an auxiliary transmission 31 between the
V-belt-type continuously variable transmission mechanism CVT
(secondary pulley 7) and the drive wheel 5 as shown as an example
in FIG. 2(a), a friction element (e.g., a clutch or a brake)
governing the shifting of the auxiliary transmission 31 may be
utilized so as to decouplably couple the V-belt-type continuously
variable transmission mechanism CVT (secondary pulley 7) and the
drive wheel 5 to each other. Such a feature is beneficial in terms
of cost as there is no need to further provide a dedicated clutch
for decouplably coupling the V-belt-type continuously variable
transmission mechanism CVT (secondary pulley 7) and the drive wheel
5 with each other.
[0035] The auxiliary transmission 31 in FIG. 2A comprises a
Ravigneaux planetary gear set comprising composite sun gears 31s-1,
31s-2, an inner pinion 31pin, an outer pinion 31pout, a ring gear
31r, and a carrier 31c for rotatably supporting the pinions 31pin,
31pout.
[0036] From among the composite sun gears 31s-1, 31s-2, the sun
gear 31s-1 is coupled to the secondary pulley 7 so as to operate as
an input rotation member, and the sun gear 31s2 is disposed
coaxially, albeit capable of freely rotating, with respect to the
secondary pulley 7.
[0037] The inner pinion 31pin is engaged with the sun gear 31s-1,
and each of the inner pinion 31pin and the sun gear 31s2 is engaged
with the outer pinion 31pout.
[0038] The outer pinion 31pout is engaged with the inner periphery
of the ring gear 31r, and the carrier 31c is coupled to the final
gear set 9 so as to operate as an output rotation member.
[0039] The carrier 31c and the ring gear 31r can be coupled as
appropriate by a high clutch H/C, the ring gear 31r can be fixed as
appropriate by a reverse brake RIB, and the sun gear 31s2 can be
fixed as appropriate by a low brake L/B.
[0040] The auxiliary transmission 31 is such that engaging the high
clutch H/C, the reverse brake RIB, and the low brake L/B, which are
transmission friction elements, in the combinations indicated by
circles in FIG. 2B and releasing the remaining elements as
indicated by crosses in FIG. 2B makes it possible to select the
shift stage from a forward first speed, a forward second speed, and
reverse. When the high clutch H/C, the reverse brake R/B, and the
low brake L/B are all released, the auxiliary transmission 31 is in
a neutral state in which power transmission does not take place.
From this state, if the low brake L/B is engaged, the auxiliary
transmission 31 is placed in a state in which the first forward
speed is selected (speed reduction state); if the high clutch H/C
is engaged, the auxiliary transmission 31 is placed in a state in
which the second forward speed is selected (directly connected
state); and if the reverse brake R/B is engaged, the auxiliary
transmission 31 is placed in a state in which reverse gear is
selected (reverse state).
[0041] The continuously variable transmission 4 in FIG. 2A is such
that releasing all of the transmission friction elements H/C, R/B,
and L/B and putting the auxiliary transmission 31 in a neutral
state make it possible to decouple the V-belt-type continuously
variable transmission mechanism CVT (secondary pulley 7) and the
drive wheel 5 from each other. Accordingly, in the continuously
variable transmission 4 in FIG. 2A, the transmission friction
elements H/C, R/B, and LB of the auxiliary transmission 31 fulfill
the function of the clutch CL in FIG. 1, and the V-belt-type
continuously variable transmission mechanism CVT (secondary pulley
7) and the drive wheel 5 can be decouplably coupled to each other
without further providing a clutch CL as shown in FIG. 1.
[0042] The continuously variable transmission 4 shown in FIG. 2A is
controlled through a working medium of oil from the engine-driven
oil pump O/P. The above control of the continuously variable
transmission 4 is performed as follows by the transmission
controller 24 through a line pressure solenoid 35, a lock-up
solenoid 36, a primary pulley pressure solenoid 37, a low brake
pressure solenoid 38, a high clutch pressure and reverse brake
pressure solenoid 39, and a switch valve 41. In addition to the
signal described above with reference to FIG. 1, a signal from a
vehicle speed sensor 32 for detecting the vehicle speed VSP and a
signal from an acceleration sensor 33 for detecting the vehicle
acceleration/deceleration degree G are inputted into the
transmission controller 24.
[0043] The line pressure solenoid 35 adjusts, in response to a
command from the transmission controller 24, the pressure of the
oil from the oil pump O/P to a line pressure PL corresponding to
the driving force required for the vehicle and supplies the line
pressure PL as a secondary pulley pressure to the secondary pulley
7 at all times, whereby the secondary pulley 7 clamps the V-belt 8
at a thrust corresponding to the line pressure PL so that no
slippage takes place.
[0044] The lock-up solenoid 36 directs the line pressure PL towards
the torque converter T/C as appropriate in response to a lock-up
signal from the transmission controller 24, and thereby puts the
torque converter T/C in a lock-up state in which the input and
output elements are directly connected as required.
[0045] The primary pulley pressure solenoid 37 adjusts the line
pressure PL to a primary pulley pressure in response to a CVT gear
speed ratio command from the transmission controller 24 and
supplies the primary pulley pressure to the primary pulley 6,
whereby the V-groove width of the primary pulley 6 and the V-groove
width of the secondary pulley 7 supplied with the line pressure PL
are controlled so that the CVT gear speed ratio matches the command
from the transmission controller 24, and the CVT gear speed ratio
command from the transmission controller 24 is realized.
[0046] When the transmission controller 24 issues a first speed
selection command for the auxiliary transmission 31, the low brake
pressure solenoid 38 feeds the line pressure PL as a low brake
pressure to the low brake L/B and thereby causes the low brake L/B
to engage, and the first speed selection command is realized.
[0047] When the transmission controller 24 issues a second speed
selection command or a reverse selection command for the auxiliary
transmission 31, the high clutch pressure and reverse brake
pressure solenoid 39 supplies the line pressure PL to the switch
valve 41 as a high clutch pressure and a reverse brake
pressure.
[0048] When the second speed selection command is issued, the
switch valve 41 directs the line pressure PL from the solenoid 39
to the high clutch H/C as a high clutch pressure, and causes the
high clutch H/C to engage, whereby the second speed selection
command for the auxiliary transmission 31 is realized.
[0049] When the reverse selection command is issued, the switch
valve 41 directs the line pressure PL from the solenoid 39 towards
the reverse brake R/B as a reverse brake pressure, and causes the
reverse brake R/B to engage, whereby the reverse selection command
for the auxiliary transmission 31 is realized.
[0050] EV Deceleration Regeneration Mode
[0051] The EV deceleration regeneration mode of the hybrid vehicle
according to the first embodiment will now be described with
reference to the vehicle driving system in FIG. 1. In a case in
which the acceleration pedal 19 is released during HEV travel so as
to make a shift to coasting (inertial travel), or in a case in
which the brake pedal 16 is subsequently depressed and the vehicle
is braked, regenerative deceleration control in which the electric
motor 2 performs regenerative braking is performed. The kinetic
energy of the vehicle is thereby converted into electrical power,
and the electrical power is stored in the battery 12, whereby
energy efficiency is improved.
[0052] When regenerative braking is performed during HEV travel
(i.e., during HEV regeneration), since the clutch CL is in an
engaged state, the regenerative braking energy decreases by an
amount corresponding to the reverse driving force of the engine
(engine braking) and the friction in the continuously variable
transmission 4, resulting in poor engine regeneration
efficiency.
[0053] Therefore, when the vehicle speed falls below a
predetermined vehicle speed, there is selected an EV deceleration
regeneration mode, in which the clutch CL is put in a released
state, the engine 1 and the continuously variable transmission 4
are decoupled from the drive wheel 5 and a shift is made to EV
travel to produce an EV regeneration state, the drag in the engine
1 and the continuously variable transmission 4 is thereby removed,
and the corresponding energy regeneration amount is thereby
saved.
[0054] While the clutch CL is released as described above, the
engine 1 is stopped so that an unnecessary operation does not take
place from the viewpoint of fuel economy. Therefore, injection of
fuel into the engine 1 is prohibited from restarting (i.e.,
fuel-cut recovery is prevented) so that the discontinuation of fuel
injection into the engine 1 (i.e., fuel cut), which was in place
during the above coasting, is maintained when the clutch CL is
released. As a result, the engine 1 is stopped when the clutch CL
is released. Fuel-cut recovery refers to a control in which fuel
injection is restarted when, in a state in which fuel injection is
discontinued, the engine rotation speed falls below the minimum
rotation speed at which the engine 1 is capable of self-rotating
(e.g., the idling rotation speed), whereby an engine operation
state is obtained without starting the engine using the starter
motor 3. Note that in order to stop the operation of the engine 1
in EV mode, the fuel-cut recovery control is prohibited from
operating, whereby the engine 1 is stopped.
[0055] However, a problem was presented that when the engine 1 is
stopped as described above, it is not possible to obtain a negative
pressure in the engine 1, preventing the assist function from the
negative pressure-type brake booster 17 from being obtained.
[0056] For example, in a configuration in which the travel mode is
switched so as to shift to EV travel when the vehicle speed falls
below a predetermined vehicle speed during coasting while HEV
travel is being performed, setting the predetermined vehicle speed
at a higher vehicle speed makes it possible to obtain a higher
regenerative energy and can therefore be said to be preferable.
However, assuming that the deceleration degree is uniform, setting
a higher vehicle speed [as the predetermined speed] increases the
length until the vehicle comes to a stop and therefore gives the
driver more opportunities to repeat the operations of depressing
and easing the brake pedal 16.
[0057] In the negative pressure-type brake booster 17, if the brake
pedal 16 is repeatedly operated with the engine 1 in a stopped
state of operation, there is a risk of the consumption of negative
pressure preventing a sufficient assist force from being obtained,
resulting in a risk of producing a state in which the brake pedal
16 cannot be significantly depressed and of imparting the driver
with a sense of unease. This is because the negative pressure-type
brake booster 17 has a structure in which, when the piston position
in the master cylinder is returned after the brake pedal 16 is
depressed, negative pressure is lost.
[0058] Accordingly, in the first embodiment, when the clutch CL is
put in a released state and regenerative braking is performed using
the electric motor 2, the engine rotation speed is kept to a
predetermined rotation speed or above in order to ensure negative
pressure is produced.
[0059] FIG. 3 is a time chart showing the control process in the EV
deceleration regeneration mode of the first embodiment. The initial
state is one in which at [a speed] equal to or higher than the
predetermined vehicle speed Vnew at which the lock-up clutch is
engaged, the acceleration pedal 19 is released and [the vehicle is]
coasting in HEV travel mode. The description will be given together
with a comparative example in which the predetermined speed is set
to Vold which is lower than Vnew and the engine 1 is not operated
when the clutch CL is released.
[0060] When, at time t1, the vehicle speed falls below the
predetermined vehicle speed Vnew, the fuel-cut recovery control is
started. Then, both the clutch CL and the lock-up clutch are
released. Accordingly, even when the engine rotation speed rapidly
falls to the vicinity of the idling rotation speed due to the
clutch CL and the lock-up clutch being released, the fuel-cut
recovery control causes the fuel injection to restart, and the
engine is put in an idling state at which the idling rotation speed
is maintained and a predetermined torque is outputted. It is
thereby possible to ensure that negative pressure is produced,
making it possible to ensure that the negative pressure-type brake
booster 17 delivers the assist function. In addition, it is
possible to ensure operation of the oil pump O/P for supplying
hydraulic pressure to the continuously variable transmission 4,
making it possible to continuously maintain the gear speed ratio
control of the continuously variable transmission 4, and produce
the desired gear speed ratio.
[0061] Releasing the clutch CL results in a deficit amounting to
the engine friction torque. Therefore, the regenerative torque from
the electric motor 2 is increased to ensure the control torque is
obtained.
[0062] In contrast, in the comparative example, the engine 1 is not
operated when the clutch is released, preventing the negative
pressure from being obtained. Therefore, it is necessary to set the
predetermined vehicle speed to a lower vehicle speed so as to
shorten the state in which the clutch CL is released. Accordingly,
the predetermined vehicle speed is set to Vold which is lower than
Vnew, and the clutch CL is not released until [the vehicle speed]
has fallen to Vold at time t2. Accordingly, in the comparative
example, while the vehicle speed falls from Vnew to Vold, the
clutch CL cannot be released and no regenerative energy can be
obtained, but in the first embodiment, it is possible to obtain
sufficient regeneration energy during this period.
[0063] As described above, in the first embodiment, the following
effects are obtained.
(1) The hybrid vehicle control device according to the first
embodiment is provided with:
[0064] a continuously variable transmission 4 (transmission)
coupled to an output shaft of an engine 1;
[0065] a clutch CL interposed between the continuously variable
transmission 4 and a drive wheel;
[0066] an electric motor (motor) (2) coupled to the drive
wheel;
[0067] a negative pressure-type brake booster 17 (boosting means or
device) for using a negative pressure of the engine 1 to assist the
brake-pedal-16-depressing force applied by a driver; and
[0068] a hybrid controller 21 (control means or controller) for
controlling the output state of the engine 1 and the electric motor
2, the gear speed ratio of the continuously variable transmission
4, and engaging/releasing of the clutch CL according to the
operation state,
[0069] the hybrid controller 21 being capable of switching, between
an operating state and a non-operating state, a fuel-cut recovery
control in which the engine rotation speed is kept at or above an
idling rotation speed by starting supply of fuel upon engine
rotation speed falling to the idling rotation speed from a state in
which the engine rotation speed is higher than the idling rotation
speed (predetermined rotation speed) and the supply of fuel is
stopped;
[0070] an EV deceleration regeneration mode being a mode in which
when the vehicle decelerates from a high-vehicle-speed state higher
than a predetermined vehicle speed to a vehicle speed equal to or
lower than the predetermined vehicle speed with the clutch in an
engaged state, the clutch CL is switched from an engaged state to a
released state and a regenerative torque is imparted by the
electric motor 2 to the drive wheel; and
[0071] when the EV deceleration regeneration mode is set, the
fuel-cut recovery control being switched to the operating state
prior to the clutch CL being switched from an engaged state to a
released state, and the engine rotation speed being kept at or
above an idling rotation speed (predetermined rotation speed).
[0072] In other words, keeping the engine rotation speed at or
above the idling rotation speed makes it possible to ensure that a
negative pressure is produced, and even if the driver repeats the
brake pedal operation prior to the vehicle coming to a stop, the
negative pressure-type brake booster 17 is able to deliver an
assist function, making it possible for the brake pedal 16 to be
depressed. Accordingly, braking can be performed without imparting
the driver with a sense of unease.
[0073] In addition, operating the fuel-cut recovery control prior
to releasing the clutch CL makes it possible to produce a state in
which the engine 1 is self-rotating without the engine rotation
speed decreasing when the clutch CL is released. If the fuel-cut
recovery control was already functioning prior to the vehicle speed
reaching the predetermined vehicle speed, the fuel-cut recovery
control is simply continued.
[0074] In addition, since negative pressure can be obtained, the
predetermined vehicle speed Vnew can be set so as to be relatively
high, making it possible to recover regenerative energy in a more
efficient manner. Furthermore, since it is possible to maintain the
rotating state of the continuously variable transmission 4 and to
obtain a supply of hydraulic pressure due to operation of the oil
pump O/P, the continuously variable transmission 4 can be shifted
to a desired gear speed ratio, and an appropriate gear speed ratio
can be obtained, e.g., during a restart or when there is a request
for a reacceleration.
Second Embodiment
[0075] A second embodiment will now be described. The basic
configuration is the same as that of the first embodiment;
therefore, a description will be given with regards to the
differences. In the first embodiment, when the EV deceleration
regeneration mode is selected, the engine 1 is put in an idling
state. In contrast, in the second embodiment, as a brake request
made by the driver, the negative pressure of the negative
pressure-type brake booster 17 is detected by the negative pressure
sensor 17a, and the presence of a predetermined value (negative
pressure necessary for braking) is determined. If the predetermined
value is not available, a negative pressure request is outputted,
and the operation state of the engine 1 is maintained. If the
negative pressure is available, the negative pressure request is
stopped, i.e., the fuel-cut recovery control is prohibited from
taking place. The negative pressure necessary for braking refers
to, e.g., a value at which a rapid deceleration to a state in which
the vehicle has come to a stop is possible.
[0076] FIG. 4 is a time chart showing the control process in the EV
deceleration regeneration mode of the second embodiment. The
initial state is one in which at a speed equal to or higher than
the predetermined vehicle speed Vnew at which the lock-up clutch is
engaged, the acceleration pedal 19 is released, the brake pedal 16
is depressed, a brake request is outputted, and the vehicle is
decelerating in HEV travel mode.
[0077] When, at time t1, the vehicle speed falls below the
predetermined vehicle speed Vnew, the fuel-cut recovery control is
started. Then, both the clutch CL and the lock-up clutch are
released. Accordingly, even when the engine rotation speed rapidly
falls to the vicinity of the idling rotation speed due to the
clutch CL and the lock-up clutch being released, the fuel-cut
recovery control causes the fuel injection to restart, and the
engine is put in an idling state at which the idling rotation speed
is maintained and a predetermined torque is outputted. Negative
pressure is thereby obtained, making it possible to ensure that the
negative pressure-type brake booster 17 delivers the assist
function.
[0078] When, at time t11, a negative pressure necessary for braking
is obtained, there is no longer a need to produce a negative
pressure; therefore, the fuel-cut recovery control is prohibited,
and the operation of the engine 1 is thereby stopped. It is thereby
possible to suppress wasteful fuel consumption.
[0079] As described above, in the second embodiment, the following
effects are obtained.
(2) The hybrid vehicle control device according to the second
embodiment has a negative pressure sensor 17a (brake request
detection means or device) for detecting a negative pressure
(whether or not a brake request made by the driver is
satisfied);
[0080] the hybrid controller 21, upon it being detected that the
brake request is satisfied while the engine rotation speed is kept
at or above the idling rotation speed, reduces the engine rotation
speed to below the idling rotation speed.
[0081] It is thereby possible to suppress wasteful fuel consumption
and improve fuel economy.
Third Embodiment
[0082] A third embodiment will now be described. The basic
configuration is the same as that of the second embodiment;
therefore, a description will be given with regards to the
differences. In the third embodiment, when the operation of the
engine 1 is stopped as with the second embodiment and the braking
force requested by the driver subsequently becomes equal to or
greater than a predetermined value, the clutch CL is engaged to
ensure negative pressure is obtained. In the third embodiment, with
regards to the required braking force value, a determination is
made on the basis of whether or not the stroke amount detected by
the stroke sensor 16a is equal to or greater than a predetermined
value. However, the above is not provided by way of limitation; any
configuration capable of detecting the brake request made by the
driver, such as one for detecting, e.g., the master cylinder
pressure or the depression force, is also possible.
[0083] FIG. 5 is a time chart showing the control process in the EV
deceleration regeneration mode of the third embodiment. The initial
state is one in which at a speed equal to or higher than the
predetermined vehicle speed Vnew at which the lock-up clutch is
engaged, the acceleration pedal 19 is released, the brake pedal 16
is depressed, a brake request is outputted, and the vehicle is
decelerating in HEV travel mode. The control process is identical
to that in the second embodiment until time t11; therefore, a
description will be given with regards to the period after time
t11.
[0084] When, at time t12, the driver depresses the brake pedal 16,
and a requested braking force equal to or greater than a
predetermined value is detected, the clutch CL switches from a
released state to an engaged state. Then, the engine rotation speed
increases to that determined according to the vehicle speed and the
gear speed ratio, and it becomes possible to generate a negative
pressure. At this time, the torque increases by an amount
corresponding to the engine friction, and the regenerative torque
of the electric motor 2 is reduced by a corresponding amount. The
fuel-cut recovery control remains OFF at this time, making it
possible to ensure a negative pressure is obtained while preventing
the fuel economy from worsening due to injection of fuel.
[0085] As described above, in the third embodiment, the following
effects are obtained.
(3) The hybrid controller 21 switches the clutch CL from a released
state to an engaged state when the braking force required by the
driver is equal to or greater than a predetermined value while the
engine is stopped (while the engine rotation speed is reduced to
below the idling rotation speed). Accordingly, it is possible to
increase the engine rotation speed without using the starter motor
3 or another element, and to ensure a negative pressure is obtained
while improving the durability of the starter motor 3. In addition,
there is no need to perform injection of fuel, and the fuel economy
can be improved.
[0086] In the third embodiment, the negative pressure of the engine
1 is used. However, a configuration in which the continuously
variable transmission 4 is provided with a pump or a similar
element capable of generating a negative pressure, and the negative
pressure is produced using the pump or a similar element, is also
possible. In such a case, the negative pressure can be efficiently
obtained by engaging the clutch CL, even if the lock-up clutch is
kept released.
Fourth Embodiment
[0087] A fourth embodiment will now be described. The basic
configuration is the same as that of the second embodiment;
therefore, a description will be given with regards to the
differences. In the fourth embodiment, when the operation of the
engine 1 is stopped as with the second embodiment and the braking
force requested by the driver subsequently becomes equal to or
greater than a predetermined value, the fuel-cut recovery control
is switched to an operating state, the engine 1 is cranked using
the starter motor 3, and the engine is started, whereby a negative
pressure is obtained.
[0088] FIG. 6 is a time chart showing the control process for the
EV deceleration regeneration mode of the fourth embodiment. The
initial state is one in which at a speed equal to or higher than
the predetermined vehicle speed Vnew at which the lock-up clutch is
engaged, the acceleration pedal 19 is released, the brake pedal 16
is depressed, a brake request is outputted, and the vehicle is
decelerating in HEV travel mode. The control process is identical
to that in the second embodiment until time t11; therefore, a
description will be given with regards to the period after time
t11.
[0089] When, at time t13, the driver depresses the brake pedal 16,
and a required braking force equal to or greater than a
predetermined value is detected, the fuel-cut recovery control is
switched from a prohibited state to a permitted state, and the
engine 1 is cranked and started using the starter motor 3. It is
thereby possible for the engine 1 to maintain the idling rotation
speed, and for a negative pressure to be obtained. The clutch CL
remains released, and the regenerative torque of the electric motor
2, etc., remains unaffected, making it possible to prevent
phenomena such as a variation in the braking torque during
braking.
[0090] In addition, since the engine 1 is operating, even if the
driver depresses the acceleration pedal 19 and issues a
reacceleration request or a restart request at this time, a
sufficient torque can be swiftly obtained, making it possible to
improve the response to the reacceleration request or the restart
request.
[0091] As described above, in the fourth embodiment, the following
effects are obtained.
(4) The hybrid controller 21 increases the engine rotation speed to
or above the idling rotation speed when the braking requested by
the driver is equal to or greater than a predetermined braking
force while the engine 1 is stopped (while the engine rotation
speed is reduced to below the idling rotation speed). It is thereby
possible for the engine 1 to maintain the idling rotation speed,
and for a negative pressure to be obtained. In addition, since the
engine 1 is operating, even if the driver issues a reacceleration
request or a restart request, a sufficient torque can be swiftly
obtained, making it possible to improve the response to the
reacceleration request or the restart request.
[0092] The present invention was described above with reference to
embodiments. However, the present invention is not limited to the
configurations described above; other configurations may also be
included in the present invention.
[0093] The first embodiment indicated an example in which the
engine rotation speed is kept at or above the predetermined
rotation speed by performing fuel-cut recovery on the engine 1.
However, from the viewpoint of simply securing a sufficient engine
rotation speed, a sufficient engine rotation speed may be secured
using the starter motor 3 or a similar element without injecting
fuel.
[0094] In addition, in the embodiments, a sufficient engine
rotation speed is secured on the basis of a negative pressure
requirement or a braking force request. However, a configuration is
also possible in which a sufficient engine rotation speed is
secured on the basis of, e.g., an alternator power generation
requirement.
[0095] Furthermore, the embodiments indicated configurations in
which the engine is restarted by engaging the clutch CL or using
the starter motor 3; however, other configurations are possible.
Specifically, a technical feature being put in practical use in
recent years is a vehicle with an idling-stop function wherein the
alternator is replaced with a motor generator, an alternator
function is added to the motor generator to impart the motor
generator with an engine-starting function, and the engine is
thereby restarted from an idling-stopped state using the motor
generator instead of a starter motor. The present invention may be
configured so that the engine is restarted using a motor generator
as described above.
[0096] In addition, in the present embodiment, whether or not the
vehicle is in a braking state is determined on the basis of whether
the brake switch is ON or OFF. However, this is not provided by way
of limitation; the determination can be made on the basis of an
output value from the stroke sensor of the brake pedal or on the
basis of an output value from a brake liquid pressure sensor for
detecting the master cylinder pressure or another parameter.
* * * * *