JP6759678B2 - Braking control device - Google Patents

Description

The present invention relates to a vehicle braking control device.

Conventionally, in a vehicle equipped with an automatic transmission, a technique for reducing a shock at the time of downshifting has been developed.
For example, Patent Document 1 below describes a shift-down prediction means for predicting a shift-down of an automatic transmission in a vehicle braking control device having an automatic transmission mounted on the vehicle and a braking device that applies braking force to the vehicle. Based on the information from the downshift prediction means, the braking force addition control means that automatically applies the braking force to the braking device from the time of prediction until a predetermined time elapses after the completion of the downshift, and the implementation of the downshift. It is provided with an additional amount limiting means for reducing the amount of braking force applied by the braking force additional control means, and prevents a shift shock during a downshift in a power-off state.

Japanese Patent No. 3543904

The above-mentioned prior art is aimed at preventing a shock (sudden deceleration) due to a sudden change in the rotation speed on the output shaft side of the automatic transmission after the downshift is executed because the gear ratio is different before and after the downshift. ..
On the other hand, during the downshift execution, there is a time zone in which the frictional engagement element in the automatic transmission is temporarily disengaged to be in the neutral state, that is, torque is released. During this time period, the deceleration torque approaches 0 and the vehicle accelerates, causing a shock associated with this acceleration.
In the above-mentioned conventional technique, the shock on the acceleration side at the time of downshifting is not taken into consideration, and there is room for improvement.
The present invention has been made in view of such circumstances, and an object of the present invention is to reduce an acceleration side shock at the time of downshifting.

To achieve the above object, the present invention is to provide a brake control apparatus for a vehicle having an automatic transmission and a braking device, the to that braking force generated by the brake device during downshift execution of the automatic transmission The braking force control unit includes a braking force control unit for increasing, and the braking force control unit increases the braking force generated by the braking device when the downshift is executed during braking based on the deceleration operation of the driver. When the execution of the downshift is completed, the braking force is temporarily reduced as compared with that before the execution of the downshift, and then returned to the braking force before the execution of the downshift.
In the present invention, the braking force control unit acquires a control signal instructing the automatic transmission to shift down, and the braking force after the acquisition of the control signal and before the shift down is executed by the automatic transmission. It is characterized by starting to increase.
The present invention further includes an input unit for inputting the downshift instruction by the driver, and the braking force control unit executes the downshift when the downshift is executed based on the instruction. It is characterized in that the braking force is not increased, the braking force is temporarily decreased after the shift down is executed, and then the braking force is returned to the braking force before the shift down is executed.

According to the present invention, since the braking force is increased during downshift execution, it is possible to prevent the vehicle from accelerating when the friction engaging element in the automatic transmission is temporarily disengaged and the vehicle is in the neutral state. However, it is advantageous in reducing the shock on the acceleration side at the time of downshifting and improving the riding feeling.
According to the present invention, since the braking force starts to increase before the automatic transmission performs downshifting, the rate of change in torque input to the drive wheels of the vehicle is reduced, and the acceleration side shock during downshifting is reduced. It is advantageous in reducing the amount more effectively.
According to the present invention, the braking force generated by the braking device is increased when the downshift is executed during braking based on the driver's deceleration operation, and the shift is completed when the downshift execution is completed. Since the braking force is temporarily reduced compared to before the downshift, the acceleration side shock during downshifting is reduced, and the deceleration side shock after downshifting is reduced, which is advantageous in further improving the riding feeling. It becomes.
According to the present invention, when the downshift is executed based on the driver's instruction, the braking force is not increased during the execution of the downshift, and the braking force is temporarily decreased after the downshift is executed. Even when the downshift timing cannot be predicted, it is advantageous in reducing the deceleration side shock after the friction engaging element is engaged (after the downshift is executed).

It is a block diagram which shows the structure of the vehicle 20 which mounted the braking control device which concerns on embodiment. It is explanatory drawing which shows the brake mechanism 50 of the vehicle 20. It is a timing chart which shows the operating state of each part at the time of downshifting. It is a timing chart which shows the operating state of each part at the time of downshifting. It is a timing chart which shows the operating state of each part at the time of downshifting. It is a timing chart which shows the operating state of each part at the time of downshifting.

Hereinafter, preferred embodiments of the braking control device according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory view showing a drive unit of a vehicle 20 equipped with the braking control device according to the embodiment.
The vehicle 20 travels by driving driving wheels (not shown) by the engine 22. An automatic transmission 24 is connected between the engine 22 and the drive wheels. The automatic transmission 24 and the drive wheels are connected via an output shaft 23.
The automatic transmission 24 includes a torque converter (TC) 26, a transmission mechanism 28, and a hydraulic control unit 30. The transmission mechanism 28 has a plurality of hydraulic friction engagement elements such as a planetary gear, a hydraulic clutch, and a hydraulic brake built-in, and the shift stage is determined according to the combination of engagement of these plurality of hydraulic friction engagement elements. The hydraulic control unit 30 houses a plurality of solenoid valves that supply and release hydraulic pressure from a hydraulic unit (not shown) to the plurality of hydraulic friction engaging elements. The solenoid valves of the hydraulic control unit 30 are electrically connected to the ECU 10, and are switched and controlled according to a drive signal from the ECU 10.

The ECU 10 includes a CPU, a ROM for storing and storing a control program, a RAM as an operating area for the control program, an EEPROM for holding various data in a rewritable manner, an interface unit for interfacing with peripheral circuits, and the like. To.
In the present embodiment, the CPU of the ECU 10 executes the control program to function as a braking force control device (braking force control unit 102) and a shift control unit 104.
In the present embodiment, the processing of the braking force control unit 102 and the shift control unit 104 is executed on the same ECU 10, but for example, the processing of the braking force control unit 102 is performed by a separate ECU (for example, a brake ECU). ) May be executed.

The ECU 10 includes a wheel speed sensor 32 that detects the rotation speed of each wheel, a brake switch 36 that detects the presence or absence of operation of the brake pedal 505, an accelerator opening sensor 40 that detects the amount of operation of the accelerator pedal 38, and an automatic transmission. A shift sensor 42 for detecting the current shift of 24, a shift switch 46 for detecting the operating position of the shift lever 44, a hydraulic pressure sensor 512 for detecting the hydraulic pressure of the brake fluid, and the like are connected.

The shift lever 44 can switch the shift mode of the automatic transmission 24 by the operation of the driver. In the present embodiment, the shift lever 44 has a parking range (P range), a neutral range (N range), a reverse range (R range), and a traveling range (in which automatic transmission is performed by the automatic transmission 24 during traveling). It can be operated between the D range) and the manual range (M range) that allows the driver to switch gears while driving.

Further, the output side of the ECU 10 is connected to the solenoid valve of the hydraulic control unit 30 and the brake mechanism 50 provided on the wheel. The brake mechanism 50 is a braking device that applies a braking force to the vehicle 20.
FIG. 2 is an explanatory view showing a brake mechanism 50 of the vehicle 20.
As shown in the figure, wheel cylinders 501A to 501D are connected to the master cylinder 503 via a liquid passage 502, and when the driver depresses the brake pedal 505, the master cylinder 503 responds to the operation of the brake pedal 505. The brake fluid (working fluid) inside is pressurized, and the brake fluid is supplied to the wheel cylinders 501A to 501D via the liquid passage 502. The wheel cylinders 501A to 501D are provided corresponding to the front, rear, left, and right wheels of a vehicle (not shown).

As shown in the figure, the liquid passage 502 has two liquid passages (the first), for example, in the case of X piping, a liquid passage 502F for the left front wheel and the right rear wheel and a liquid passage 502R for the right front wheel and the left rear wheel. It is composed of one fluid passage), and the liquid passages 502F for the left front wheel and the right rear wheel are branched into two liquid passages 502A and 502B on the downstream side thereof. The liquid passages 502A and 502B are connected to the wheel cylinder 501A of the left front wheel and the wheel cylinder 501B of the right rear wheel, respectively.
Similarly, the liquid passages 502R for the right front wheel and the left rear wheel are also branched into two liquid passages 502C and 502D on the downstream side thereof, and the liquid is supplied to the wheel cylinder 501C of the right front wheel and the wheel cylinder 501D of the left rear wheel. Roads 502C and 502D are connected, respectively.

Then, when the brake pedal 505 is depressed, hydraulic pressure is generated in the wheel cylinders 501A to 501D via the respective liquid passages 502A to 502D, and a braking force corresponding to the hydraulic pressure of the brake fluid is generated in each wheel cylinder 501A to 501D. It is designed to do.
By the way, as shown in the figure, a hydraulic unit 506 provided with various valves and liquid passages is provided between the master cylinder 503 and the wheel cylinders 501A to 501D.

The hydraulic unit 506 independently supplies and discharges the brake fluid to the wheel cylinders 501A to 501D according to the operating state of the vehicle regardless of whether or not the brake pedal 505 is operated, so that the wheel cylinders 501A to 501D The braking force generated in the wheel can be controlled individually.
By controlling the braking force of each wheel in this way, the vehicle behavior is stabilized even when the vehicle behavior becomes unstable (or when it is predicted that the vehicle behavior will become unstable). It is possible to plan.

Hereinafter, the hydraulic unit 506 will be described. In the hydraulic unit 506, switching valves 508 are provided on the liquid passage 502F for the left front wheel and the right rear wheel and the liquid passage 502R for the right front wheel and the left rear wheel, respectively. Has been done. Further, on each of the liquid passages 502A to 502D on the downstream side of the switching valve 508, a fluid holding valve (hereinafter, simply referred to as a holding valve) 507A to be turned on and off in response to a control signal from the braking force control unit 102 of the ECU 10 Each 507D is provided.

Further, on the upstream side of one of the switching valves 508, a hydraulic pressure sensor 512 for detecting the hydraulic pressure of the brake fluid in the liquid passage (first fluid passage) 502R is provided. The hydraulic pressure sensor 512 is for detecting the brake hydraulic pressure when the driver depresses the brake pedal 505, and the braking force required by the driver is obtained from the brake fluid pressure.

Further, in order to supply the brake fluid to the liquid passages 502R and 502F on the downstream side of the switching valve 508 and on the upstream side of the holding valves 507A to 507D in addition to the supply of the brake fluid by the driver's brake pedal operation. One end of the second liquid passage (second fluid passage) 513 of the above is connected.
A pump 515 driven by a motor 514 is connected to the other end side of the second liquid passage 513, and check valves 524 and 525 are interposed on the upstream side and the downstream side of the pump 515, respectively.

Further, the pump 515 and the master cylinder 503 are connected by a liquid passage 516. Then, when the pump 515 operates, the brake fluid supplied from the master cylinder 503 via the liquid passage 516 is pressurized and directly supplied to the respective liquid passages 502A to 502D.
Further, an intake valve 517 is interposed on the liquid passage 516. Here, the intake valve 517 is an on / off type solenoid valve that selectively switches the liquid passage 516 into a communication state or a cutoff state, and its operation is controlled based on a control signal from the braking force control unit 102 of the ECU 10. It has become so.

On the other hand, drain fluid passages 520A to 520D are connected between the holding valves 507A to 507D and the wheel cylinders 501A to 501D, respectively, and control signals from the ECU 10 are connected to the drain fluid passages 520A to 520D. Pressure reducing valves 521A to 521D whose operation is controlled based on the above are interposed.
Further, these drainage liquid passages 520A to 520D are connected to the liquid passage 516 via a check valve 523.

Further, the braking force control unit 102 of the ECU 10 is connected to a switching valve 508, a holding valve 507A to 507D, a pressure reducing valve 521A to 521D, an intake valve 517, a pressure reducing valve 521A to 521D, and a motor 514, and the braking force of the ECU 10 is connected. The open / closed state of each valve is controlled based on the control signal from the control unit 102, and braking force can be applied to the wheel cylinders 501A to 501D.

Next, shift control by the ECU 10 will be described.
When the operating position of the shift lever 44 is in the traveling range (D range), the ECU 10 operates the hydraulic pressure control unit 30 by the shift control unit 104 to perform automatic transmission.
More specifically, the ECU 10 stores a shift map (not shown) for setting a target shift stage for selecting and setting a shift stage at the time of automatic transmission. On the shift map for setting the target shift stage, the shift stage based on the vehicle speed V (the average value of the detected values of the four wheel speed sensors 32) and the accelerator opening (the detected value of the accelerator opening sensor 40). That is, the target shift stage is set in advance.
When the shift lever 44 is in the D range while the vehicle is running, the shift map for setting the target shift stage is based on the vehicle speed V detected by the wheel speed sensor 32 and the accelerator opening detected by the accelerator opening sensor 40. The target shift stage is read from.
Then, the shift control signal read and set in this way is supplied to the corresponding solenoid valve in the hydraulic control unit 30, whereby the corresponding hydraulic friction engaging element of the hydraulic clutch, hydraulic brake, etc. of the transmission mechanism 28 is gripped. The change is carried out and the shift is achieved.

FIG. 3 is a timing chart showing the operating state of each part at the time of downshifting, FIG. 3A is a shift control signal, FIG. 3B is a state of a hydraulic friction engaging element, and FIG. 3C is an input torque to the drive wheels (automatic transmission). (Input torque from 24 to the output shaft 23), FIG. 3D shows the brake torque generated by the brake mechanism 50, and FIG. 3E shows the drive wheel torque obtained by combining C and D. The horizontal axis of each figure is time.
As shown in FIG. 3D, in FIG. 3, it is assumed that the brake mechanism 50 is operated by the operation of the brake pedal 505 by the driver to generate the brake torque.

When the shift control signal instructing the shift down (shift down from the 4th speed to the 3rd speed) is input from the ECU 10 at the time T1, the gripping of the hydraulic friction engaging element is started at the time T2 after the lapse of a predetermined time. ..
In the re-grasping of the hydraulic friction engaging element, first, the engagement of the hydraulic friction engaging element on the releasing side is released, and the transmission mechanism 28 is temporarily put into a substantially neutral state. When the vehicle is in the substantially neutral state in this way, the input torque to the drive wheels is lost, and the vehicle is in the acceleration state as indicated by reference numeral P.
After that, the hydraulic friction engaging element on the coupling side is engaged, and the shift is completed at time T3. At this time, since the gear ratio changes before and after the shift, the rotation speed of the output shaft 23 is slower than the engine rotation speed on the engine 22 side immediately after the shift (shift down) from the high speed stage side to the low speed stage side. Become. That is, at the time of downshifting, if the output of the engine 22 is constant, sudden deceleration of the vehicle as indicated by the symbol Q occurs immediately after the shift is completed.
When shifting from the low speed stage side to the high speed stage side (shift up), the rotation speed of the output shaft 23 becomes faster than the engine rotation speed on the engine 22 side, and if the output of the engine 22 is constant, the vehicle suddenly moves. It will be accelerated.

Therefore, in the present embodiment, the braking force control unit 102 of the ECU 10 increases the braking force generated by the brake mechanism 50 during the downshift execution of the automatic transmission 24.
The term "shift down" means that the engagement of the hydraulic friction engaging element on the releasing side is from the start of the disengaging operation to the completion of the engagement of the hydraulic friction engaging element on the coupling side, that is, from time T2 to T3 in FIG. Refers to the period (period SD).
The braking force control unit 102 increases the braking force by the brake mechanism 50 in accordance with the timing when the input torque to the drive wheels is released, for example, as shown by reference numeral R in FIG. 3D. This braking force cancels the torque on the acceleration side caused by torque loss and reduces the shock on the acceleration side at the time of downshifting.
Further, as shown by reference numeral S in FIG. 3D, when the shift is completed thereafter, the braking force control unit 102 may temporarily reduce the braking force of the brake mechanism 50 as compared with that before the shift down execution. As a result, sudden deceleration due to a change in the gear ratio can be prevented, and the shock at the time of shifting can be further reduced.
That is, the braking force control unit 102 increases the braking force generated by the braking mechanism 50 when downshifting is executed during braking based on the driver's deceleration operation. Further, when the execution of the downshift is completed, the braking force is temporarily reduced as compared with that before the execution of the downshift, and then returned to the braking force before the execution of the downshift.
As a result, as shown in FIG. 3E, it is possible to cancel the change in torque due to shifting and improve the riding feeling.

The amount of increase / decrease in braking force in FIG. 3D is, for example, the difference between the product of the input torque to the automatic transmission 24 and the gear ratio and the output torque to the automatic transmission 24. That is, the amount of increase / decrease in braking force = AT input torque x gear ratio-AT output torque. The input torque to the automatic transmission 24 is the output torque of the engine 22, which is constantly monitored by the ECU 10. Further, the output torque to the automatic transmission 24 is monitored by the torque converter 26, and can be acquired by the ECU 10 via CAN (Control Area Network).

Further, as shown in FIG. 4, the braking force generated by the brake mechanism 50 may be increased before the automatic transmission 24 shifts down.
FIG. 4 is another timing chart showing the operating state of each part at the time of downshifting.
Each of the figures of FIGS. 4A to 4D shows the same contents as those of FIG. Further, also in FIG. 4, it is assumed that the brake mechanism 50 is operated by the operation of the brake pedal 505 by the driver as in FIG. 3, and the brake torque is generated.

In the example of FIG. 4, when the braking force control unit 102 acquires the shift control signal instructing the automatic transmission 24 to shift down, after the shift control signal is acquired and before the shift down operation is started in the automatic transmission 24. Start increasing the braking force.
That is, when the shift control signal instructing the shift down (shift down from the 4th speed to the 3rd speed) is output from the ECU 10 at the time T4, before the re-grasping of the hydraulic friction engaging element is started at the time T6. The braking force of the brake mechanism 50 is increased from a certain time T5. The time T5 is, for example, substantially the same time as the time T4 at which the shift control signal is output.
Further, when the shift is completed at the time T7, the braking force of the brake mechanism 50 is temporarily reduced as compared with that before the shift down is executed, as in FIG.
In this way, by starting the increase in braking force at an early stage, the gradient of the drive wheel torque shown in FIG. 4E becomes small, sudden acceleration / deceleration due to shifting can be prevented, and the riding feeling can be further improved. it can.

Further, as shown in FIG. 5, when the downshift is performed when the brake pedal 505 is not operated and the brake mechanism 50 is not operating, the shift is performed as shown by the reference numeral U in FIG. 5D. A braking force is generated by the brake mechanism 50 during downshifting, and after the downshift is completed, the braking force is returned to the braking force before downshifting, that is, set to 0.
Even in the case of FIG. 5, the increase in braking force may be started after the shift control signal for instructing the shift down is acquired and before the shift down operation is started in the automatic transmission 24 as shown in FIG.

Further, when the operation position of the shift lever 44 is in the manual range (M range), the automatic transmission 24 re-grasps the hydraulic friction engaging element of the transmission mechanism 28 according to the operation to the shift lever 44, and shifts. Achieved. That is, when the operating position of the shift lever 44 is in the manual range, the shift lever 44 functions as an input unit for inputting a shift down instruction by the driver.
In this case, the braking force control unit 102 does not increase the braking force during the execution of the downshift based on the driver's instruction as shown in FIG. 6D, but applies the braking force as shown by the symbol V after the execution of the downshift. Temporarily reduce it and then return it to the braking force before the downshift.
This is because the speed change mechanism 28 operates immediately at the time of shift change by the driver's operation, and it is difficult to increase the braking force until torque is lost during downshift execution. Therefore, only the braking force of the brake mechanism 50 is reduced according to the deceleration after the downshift is completed.

As described above, according to the braking force control unit 102 according to the embodiment, the braking force is increased during the downshift execution, so that the frictional engagement element in the automatic transmission 24 is temporarily disengaged. It is advantageous in preventing the vehicle from accelerating when it is in the neutral state, reducing the shock on the acceleration side at the time of downshifting, and improving the riding feeling.
Further, if the braking force control unit 102 starts increasing the braking force before the automatic transmission 24 shifts down, the rate of change of the torque input to the drive wheels of the vehicle can be reduced. This is advantageous in reducing the acceleration side shock at the time of downshifting more effectively.
Further, in the braking force control unit 102, when the downshift is executed during braking based on the deceleration operation of the driver, the braking force generated by the brake mechanism 50 is increased, and the execution of the downshift is completed. By temporarily reducing the braking force compared to before the downshift, the acceleration side shock at the time of downshifting is reduced and the deceleration side shock after the downshift is executed, and the riding feeling is reduced. It will be advantageous in improving.
Further, when the braking force control unit 102 executes the downshift based on the driver's instruction, the braking force is not increased during the execution of the downshift, and the braking force is temporarily applied after the downshift is executed. If it is reduced, even if the downshift timing cannot be predicted, it is advantageous in reducing the deceleration side shock after the friction engaging element is engaged (after the downshift is executed).

10 ... ECU, 102 ... Braking force control unit, 104 ... Shift control unit, 20 ... Vehicle, 22 ... Engine, 23 ... Output shaft, 24 ... Automatic transmission, 26 ... Torque converter, 28 …… Transmission mechanism, 30 …… Hydraulic control unit, 50 …… Brake mechanism.

Claims (3)

A braking control device for a vehicle equipped with an automatic transmission and a braking device.
Comprising a braking force control unit that increases the to that braking force generated by the brake device during downshift execution of the automatic transmission,
When the downshift is executed during braking based on the deceleration operation of the driver, the braking force control unit increases the braking force generated by the braking device, and when the execution of the downshift is completed. The braking force is temporarily reduced as compared with that before the execution of the downshift, and then returned to the braking force before the execution of the downshift.
A braking control device characterized by this. The braking force control unit acquires a control signal instructing the automatic transmission to shift down, and starts increasing the braking force after the acquisition of the control signal and before the shift down is executed by the automatic transmission. To do,
The braking control device according to claim 1. Further provided with an input unit for inputting the downshift instruction by the driver.
When the downshift based on the instruction is executed, the braking force control unit does not increase the braking force during the execution of the downshift, and temporarily applies the braking force after the execution of the downshift. And then return to the braking force before the shift down was performed.
The braking control device according to claim 1 or 2.

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