JP2019119229A - Brake force control system - Google Patents

Abstract

To make it possible to reduce generation of unpleasant noise without occurrence of a trouble such as increase in a cost of manufacture, brake force performance reduction, tuning difficulty and so on at the time of transition from an engine brake to a friction brake by an automatic brake.SOLUTION: This brake force control system comprises a required deceleration change part which performs such that immediately after changeover from an engine brake to a friction brake by a brake selection part, a required deceleration 52, which is required by an automatic brake request part, is changed from a first required deceleration 63 to a second required deceleration 64 so as to approach an actual deceleration 53, and is returned again to the required deceleration 52 which is required by the automatic brake request part. In this case, the second required deceleration 64 is set to a deceleration lower than an intermediate deceleration 72 which is intermediate between the first required deceleration 63 and the actual deceleration 53.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a braking force control system.

  In Patent Document 1, as a result of detecting the distance between the vehicle and the obstacle and the relative speed, if it is determined that there is a possibility of contact with the obstacle but the degree of danger is low, the engine brake is It is described that it is generated and then a hydraulic brake (frictional brake) is generated as needed.

Japanese Patent Application Laid-Open No. 5-240075

  Adaptive cruise control (ACC) is known as a device mounted on a vehicle and capable of automatically performing constant-speed traveling while maintaining a constant inter-vehicle distance. The ACC (Adaptive Cruise Control) is known. The constant speed traveling / inter-vehicle distance control device automatically decelerates by controlling the brake system of the own vehicle when it is detected that a leading vehicle approaches.

  In such a constant speed traveling / inter-vehicle distance control apparatus, an engine brake is also used from the viewpoint of suppressing heat generation of a brake pad or the like of a friction brake and reducing deceleration shock at the initial stage of deceleration. That is, when the required deceleration of the automatic brake is less than a predetermined value (for example, the limit value of the braking force by the engine brake), the braking force is applied by the engine brake. Then, when the required deceleration becomes equal to or more than a predetermined value, the engine brake is switched to the friction brake to perform deceleration along the required deceleration from the constant speed traveling / inter-vehicle distance control device.

However, when changing from an engine brake to a friction brake, the friction brake is a friction braking force according to the required deceleration from the constant speed traveling / inter-vehicle distance control device from the state where the actual deceleration (friction braking force) is zero. Will be generated rapidly. As a result, an overshoot occurs in the friction braking force.
And, when the friction braking force is generated by the electric brake booster, the above-mentioned friction braking force overshoot causes the bottom of the brake pedal to stick to the pedal end even though the driver does not operate the brake pedal. An accompanying sound is generated.

In addition, depending on the vehicle, the vehicle is equipped with a skid prevention device (vehicle behavior stabilization device) that supports stable traveling by preventing the vehicle from bulging or rolling inward when bending a curve. ing. The anti-slip device individually controls the braking force of each wheel to realize stable traveling of the vehicle. And, when realizing the friction braking force of the constant speed traveling and inter-vehicle distance control device with the sideslip prevention device, the overshoot of the friction braking force causes the operation noise of the operation initial stage of the sideslip prevention device The sound when the fluid is pumped into the hydraulic system increases.
Therefore, the commodity nature of the vehicle is reduced by the generation of these unpleasant noises (bottoming noise and operation noise).

As measures against these problems, it may be considered to provide an end rubber at the end of the pedal end or cylinder for the electric brake booster. However, in this case, there is a problem that the manufacturing cost of the vehicle increases because it is necessary to provide an end rubber.
In addition, it is conceivable to perform tuning or the like to make the rise of the deceleration of the friction braking force gentle with respect to the electric brake booster and the anti-slip device. However, in this case, the response of the electric brake booster or the anti-slip device is lowered to cause a reduction in braking performance and a difficulty in tuning.

  Therefore, the object of the present invention is to generate an unpleasant sound without causing problems such as an increase in manufacturing cost, a decrease in braking performance, and a difficulty in tuning when shifting from an engine brake to a friction brake by automatic braking. To reduce the

  In the braking force control system according to the present invention, an engine brake control unit for controlling generation of an engine brake of a vehicle and a brake pedal are connected, and the hydraulic pressure is controlled by the operation of the actuator with respect to the wheel cylinder of each wheel of the vehicle. A friction brake control unit that controls an electric brake system that supplies friction brakes, a deceleration detection unit that detects an actual deceleration of the vehicle, and the above-mentioned vehicle in order to take a necessary distance from the vehicle in front. An automatic brake request unit that automatically requests a brake operation without a brake pedal operation, and the engine brake control unit when the requested deceleration requested by the automatic brake request unit is less than a predetermined value, the engine The braking force is generated by the brake, and the friction brake control unit is controlled when the required deceleration is equal to or more than the predetermined value. The brake selection unit for generating the braking force by the friction brake by the electric brake system, and the required deceleration requested by the automatic brake request unit immediately after switching from the engine brake to the friction brake by the brake selection unit The present invention is characterized by further comprising: a required deceleration changing unit for performing control to once bring the actual deceleration detected by the deceleration detection unit back to the required deceleration requested by the automatic brake request unit.

  According to the present invention, when transitioning from an engine brake to a friction brake by an automatic brake, generation of unpleasant noise is reduced without causing problems such as an increase in manufacturing cost, a decrease in braking performance, and difficulty in tuning. It can be so.

It is a block diagram showing the system configuration of the braking force control system which is one embodiment of the present invention. It is a flow chart explaining operation of a braking force control system which is one embodiment of the present invention. It is a graph explaining the operation of the braking force control system which is one embodiment of the present invention. It is a graph explaining the operation of the braking force control system which is one embodiment of the present invention. It is a graph explaining the operation of the braking force control system which is one embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a system configuration of a braking force control system 1 according to an embodiment of the present invention. A vehicle equipped with the braking force control system 1 is provided with an electric brake system 101. In the vehicle, wheel cylinders 103FR, 103RL, 103RR, and 103FL are provided on the right front wheel 102a, the left rear wheel 102b, the right rear wheel 102c, and the left front wheel 102d, respectively. The electric brake system 101 is a device that generates a friction braking force on each of the wheels by supplying hydraulic pressure (hydraulic pressure) to the wheel cylinders 103FR, 103RL, 103RR, and 103FL via the piping tube 104.

The electric brake system 101 includes a hydraulic brake device 111 and a skid prevention device 121.
The hydraulic brake device 111 includes an electric brake booster (not shown) to which the brake pedal 112 is connected. When the driver operates the brake pedal 112, the electric brake booster assists the driver's operation of the brake pedal 112 by driving the actuator (motor or the like), and the hydraulic pressure (hydraulic pressure (hydraulic pressure) is generated by a cylinder (not shown). Generate). The hydraulic pressure is transmitted to the wheel cylinders 103FR, 103RL, 103RR, and 103FL via the piping tube 104 to generate friction braking forces on the wheels.

  The skid prevention device 121 is a device for supporting a stable traveling by preventing a behavior in which the vehicle is slated to the outside of the curve or rolled in when the vehicle bends a curve, for example, ABS (Anti-Slip) The side-slip prevention device 121 also executes the function of The anti-slip device 121 transmits the hydraulic pressure (hydraulic pressure) individually to the wheel cylinders 103FR, 103RL, 103RR, and 103FL via the piping tube 104 by driving a motor and various solenoid valves (not shown). A braking force can be generated individually for each wheel.

The engine 131 is an engine serving as a drive source of the vehicle. The vehicle equipped with the braking force control system 1 may be a hybrid vehicle.
The connection of each electronic component by the diagram shown in FIG. 1 has a part connected by communication using CAN (Controller Area Network) and a part connected directly.
The braking force control system 1 is configured around a constant speed traveling / inter-vehicle distance control unit 11, a brake control unit 21 and an engine control unit 31. The brake control unit 21 and the engine control unit 31 are connected to a constant-speed travel and inter-vehicle distance control unit 11.

  The brake control unit 21 is connected to the electric brake system 101 and serves as a friction brake control unit that controls the electric brake system 101. That is, the brake control unit 21 is configured by one or more ECUs (Electronic Control Units), controls the hydraulic brake device 111 according to the operation of the brake pedal 112, and automatically controls the skid prevention device 121. Do also. The brake control unit 21 is connected to a brake pedal stroke sensor 22 that detects the moving stroke and the moving speed of the brake pedal 112. The brake control unit 21 controls an actuator, etc. of the electric brake booster of the hydraulic brake device 111 by detecting the moving stroke of the brake pedal 112 and the like by the brake pedal stroke sensor 22.

  The engine control unit 31 includes, for example, one or a plurality of ECUs including an FI (Fuel Injection) -ECU, is connected to the engine 131, and executes various controls of the engine 131. In particular, the engine control unit 31 serves as an engine brake control unit that controls the generation of an engine brake.

  A millimeter-wave radar 17, a monocular camera 18, an engine control unit 31, and a vehicle speed sensor 19 are connected to the constant-speed traveling / inter-vehicle distance control unit 11. The constant speed traveling / inter-vehicle distance control unit 11 can be controlled to automatically accelerate / decelerate the vehicle within a preset vehicle speed, and can follow the traveling while maintaining an appropriate inter-vehicle distance from the vehicle in front. I assume. The constant speed traveling / inter-vehicle distance control unit 11 is configured of one or more ECUs. The constant speed traveling / inter-vehicle distance control unit 11 realizes the functions of the automatic brake request unit 12, the brake selection unit 13, the required deceleration change unit 14, the emergency brake request unit 15, and the difference calculation unit 16. Details of the functions of these units will be described later.

  A millimeter-wave radar 17 and a monocular camera 18 are connected to the constant-speed traveling and inter-vehicle distance control unit 11 to detect a distance and a positional relationship with a leading vehicle etc. In addition, infrared laser, stereo camera, etc. A system using a sensor or an imaging device may be used. Furthermore, the vehicle speed sensor 19 connected to the constant speed traveling / inter-vehicle distance control unit 11 serves as a deceleration detection unit that detects the deceleration of the vehicle.

  Next, the operation of the electric brake system 101 will be described. FIG. 2 is a flow chart for explaining the operation of the electric brake system 101. 3 to 5 are graphs illustrating the operation of the electric brake system 101.

  The constant speed traveling / inter-vehicle distance control unit 11 controls the vehicle to travel at a constant speed while keeping the distance between the preceding vehicle and the inter-vehicle constant. Therefore, as long as the vehicle-to-vehicle distance does not change, the engine control unit 31 controls the engine 131 to control the vehicle to travel at a predetermined constant speed. In the case of a hybrid vehicle, constant speed traveling may be performed by controlling a motor / generator which is a drive source of the vehicle.

  Here, it demonstrates also with reference to FIGS. 3-5. 3 and 5 are graphs in which the “horizontal axis” represents “time” and the vertical axis represents “frictional brake request” and “deceleration”. Here, the “friction brake request” indicates whether the brake selection unit 13 has requested the generation of the friction brake. When the friction brake demand is 0.0, it indicates OFF (no friction brake demand), and when 1.0, it indicates ON (friction brake demand). In addition, "deceleration" indicates the deceleration of the vehicle (negative velocity when decelerating the vehicle), and 0.0 indicates that the deceleration of the vehicle is zero, The lower the value of 0.0, the greater the deceleration of the vehicle.

  The friction brake demand 51, the demand deceleration 52, the actual deceleration 53 and the engine brake upper deceleration 54 are shown in the diagrams in FIGS. The friction brake request 51 indicates ON and OFF of the friction brake request. The required deceleration 52 indicates the degree of deceleration of the vehicle required by the automatic brake request unit 12. The actual deceleration 53 is the deceleration of a real vehicle. This can be obtained from the vehicle speed detected by the vehicle speed sensor 19. The engine brake upper limit deceleration 54 is a limit value (upper limit) of the above-mentioned deceleration by the engine brake. FIG. 4 is an enlarged view of a broken line area 55 in FIG.

  First, as shown in FIG. 3, in the area 61 where the required deceleration 52 is flat and indicates 0.0, there is no request for an automatic brake, and the vehicle is traveling at a predetermined constant speed. After that, when the inter-vehicle distance between the leading vehicle and the host vehicle is reduced, the automatic brake request unit 12 makes an automatic brake request as shown in FIG. 2 so as to restore the inter-vehicle distance (Yes in S1). The deceleration of the vehicle at this time is also requested by the automatic brake request unit 12 (requested deceleration 52).

  That is, as shown in FIG. 4, when the required deceleration 52 is time 62, an automatic brake request is made from the automatic brake request unit 12, and the required deceleration 52 is gradually expanded from 0.0. Thus, at first, braking is started by the engine brake (S2). That is, the brake selection unit 13 controls the engine 131 via the engine control unit 31 to apply the engine brake based on the automatic brake request and the required deceleration degree output from the automatic brake request unit 12. In this case, in order to realize the deceleration of the vehicle according to the required deceleration 52 by the engine brake, it is possible to control to shift change to a predetermined stage.

  As the required deceleration 52 requested by the automatic brake request unit 12 increases as it is, the required deceleration 52 reaches the engine brake upper limit deceleration 54 (or the value of the predetermined required deceleration 52 in front of that). May). The value at that time is the first required deceleration 63. When the required deceleration 52 is larger than the first required deceleration 63, the brake selection unit 13 needs to change the braking to a friction brake. That is, the first required deceleration 63 is the required deceleration 52 immediately before the braking shifts to the friction brake.

  As described above, the deceleration of the vehicle by the engine brake has the limit value. When the required deceleration of the automatic brake request unit 12 reaches the engine brake upper limit deceleration 54 which is the limit value (or when it reaches a predetermined value close to the value), the brake selection unit 13 determines the required deceleration 52. The means for realizing the above is switched from the engine brake to the friction brake (S3: Yes or less). That is, the brake selection unit 13 switches the friction brake request from the OFF state (0.0) to the ON state (1.0). The friction brake in this case may be generated by the operation of the hydraulic brake device 111 or may be generated by the operation of the anti-slip device 121. If the required deceleration of the automatic brake request unit 12 has not reached the limit value or the like, the process returns to S2. Even if the means for realizing the required deceleration 52 is switched from the engine brake to the friction brake, the engine brake may also be operated.

  Also in the case of Yes in S3, the transition control from the engine brake to the friction brake is not uniform. That is, in the case of Yes in S3, it is determined whether the request for the emergency brake has been made from the emergency brake request unit 15 (S4). That is, when it is necessary to urgently avoid a collision with an obstacle such as a preceding vehicle in front of the vehicle, the emergency brake request unit 15 automatically requests the brake operation without operating the brake pedal 112. When the request for the emergency brake is made from the emergency brake request unit 15 (Yes in S4), the process proceeds to S9. When that is not right (No of S4), it progresses to S5. The emergency brake request unit 15 may be realized by a control unit (ECU) of a different system from the constant speed traveling / inter-vehicle distance control unit 11.

  In the case of No in S4, the difference calculation unit 16 calculates the difference between the first required deceleration 63 and the actual deceleration 53 at that time (S5). Then, the request deceleration changing unit 14 determines whether the calculated difference is less than a predetermined value (S6). And when the said difference is less than the said predetermined value (Yes of S6), it progresses to S9. When that is not right (No of S6), it progresses to S7.

As shown in FIGS. 2 to 4, in S7, the required deceleration changing unit 14 reduces the required deceleration 52 at a predetermined reduction rate from the first required deceleration 63 to the second required deceleration 64. The braking is performed by the friction brake. In this case, as shown in FIGS. 3 and 4, the required deceleration changing unit 14 causes the second required deceleration 64 to approach the actual deceleration 53 or to have substantially the same value. Further, as shown in FIG. 4, the slope of the required deceleration 52 a which is a predetermined reduction rate from the first required deceleration 63 to the second required deceleration 64 is the inclination of the line 71.
Further, in this case, as shown in FIG. 4, the required deceleration changing unit 14 sets the second required deceleration 64 to an intermediate deceleration 72 which is an intermediate value between the first required deceleration 63 and the actual deceleration 53. Also set it to a lower value. In other words, it is a gentle friction brake.

As shown in FIGS. 2 and 4, when the required deceleration changing unit 14 changes the required deceleration 52 to the second required deceleration 64, the required deceleration requested by the automatic brake requesting unit 12 is immediately reduced. It returns to the speed 52 (S8). In this case, the increase rate when increasing the required deceleration from the second required deceleration 64 toward the required deceleration 52 required by the automatic brake request unit 12 is taken as a predetermined increase rate. The slope of the required deceleration 52b, which is the predetermined increase rate in this case, is the slope of the line 73 in FIG. The portion of the required deceleration 52 shown by the broken line in FIG. 4 is the required deceleration output from the automatic brake request unit 12 when the required deceleration change unit 14 does not change the required deceleration 52. 52 is shown.
Then, the required deceleration changing unit 14 sets the absolute value of the increase rate indicated by the inclination of the line 73 to be smaller than the absolute value of the reduction rate indicated by the inclination of the line 71.

As described above, immediately after switching from the engine brake to the friction brake, the required deceleration 52 is once reduced to the second required deceleration 64 and returns to the original required deceleration 52 again. As a result, control for instantaneously returning the required deceleration 52 to the required deceleration 52 requested by the automatic brake request unit 12 is performed momentarily as the required deceleration 52 is once approached to the actual deceleration 53 or substantially the same value.
As described above, after the processes of S7 and S8 are performed, braking is performed according to the required deceleration 52 requested by the automatic brake request unit 12 by the friction brake (S9).

  In the case of Yes in S4 described above and Yes in S6, the processing in S7 and S8 described above is omitted, and the processing in S9 is executed. A graph corresponding to FIG. 3 in this case is FIG. In this case, as shown in FIG. 5, when the engine brake is switched to the friction brake (time 81), the actual deceleration 53 tends to overshoot.

According to the braking force control system 1 of the present embodiment described above, immediately after switching from the engine brake to the friction brake, the required deceleration 52 is brought closer to the actual deceleration 53 or made substantially the same value (second required deceleration 64). Then, the control to return to the required deceleration 52 requested by the automatic brake request unit 12 is performed again. Such a series of processing is instantaneously performed in a short time (about 0.1 s to 0.2 s, for example).
Further, as shown in FIG. 4, the required deceleration changing unit 14 sets the second required deceleration 64 to a value lower than the intermediate deceleration 72 which is an intermediate value between the first required deceleration 63 and the actual deceleration 53. Set
Furthermore, as described above, the second required deceleration 64 may be substantially the same as the actual deceleration 53.

  As a result, by reducing the deceleration when switching from the engine brake to the friction brake, the overshoot of the actual deceleration is suppressed and the noise with the bottom of the brake pedal 112 in the hydraulic brake device 111 or the skid prevention device 121 It is possible to reduce the generation of operation noise. In fact, in the example shown in FIG. 5, the actual deceleration 53 drops sharply at a time near the first deceleration 63, and the actual deceleration 53 tends to be an overshoot. That is, bottoming of the brake pedal 112 may occur. However, in the example of FIG. 3, the actual deceleration 53 has a gentle downward slope at times near the first deceleration 63 and the second deceleration 64, and no overshoot has occurred. Therefore, it is possible to suppress an increase in manufacturing cost due to the addition of the end rubber and a decrease in responsiveness of the friction brake. Thus, the marketability of the vehicle can be improved. In addition, when the driver does not operate the brake pedal 112, if the brake pedal 112 is automatically depressed greatly and bottomed, the driver may feel discomfort, but in the example of FIG. Absent.

  In addition, the required deceleration is increased from the second required deceleration 64 toward the required deceleration 52 by the automatic brake request unit 12. As a result, after reducing the required deceleration 52 to the second required deceleration 64, the actual deceleration 53 can be made to follow the original required deceleration 52 by the automatic brake request unit 12.

  Further, the required deceleration changing unit 14 sets the absolute value of the increase rate indicated by the inclination of the line 73 to be smaller than the absolute value of the reduction rate indicated by the inclination of the line 71. As a result, by increasing the reduction rate of the required deceleration 52a, it is possible to quickly reduce the deceleration when switching from the engine brake to the friction brake. Further, the overshoot of the actual deceleration 53 can be suppressed at an early timing. Furthermore, by setting the increasing rate of the required deceleration 52b small, the increasing rate of the actual deceleration 53 after reducing the required deceleration 52b is at a level at which there is no occurrence of the actual deceleration 53 overshoot (the bottoming Level) can be suppressed.

  Furthermore, when there is a request for emergency braking (Yes in S4), the processes in S7 and S8 are prohibited. This makes it possible to enhance the generation of braking force (braking ability) at the time of emergency automatic braking.

  Furthermore, when the difference between the first required deceleration 63 and the actual deceleration 53 at that time is less than the predetermined value (Yes in S6), the processes in S7 and S8 are prohibited. As a result, the difference between the first required deceleration 63 and the actual deceleration 53 does not generate the operation noise of the hydraulic brake device 111 or the side slip prevention device 121, or generates only a noise that the occupant does not mind. In the case of the difference between the two, it is possible to perform the early switching from the engine brake to the friction brake without performing the processes of S7 and S8.

Reference Signs List 1 braking force control system 12 automatic brake request unit 13 brake selection unit 14 request deceleration change unit 15 emergency brake request unit 16 difference calculation unit 21 brake control unit (friction brake control unit)
31 Engine control unit (engine brake control unit)
22 Brake pedal stroke sensor (deceleration detection unit)
52 Demand deceleration 53 Actual deceleration 54 Engine brake upper limit deceleration (predetermined value)
63 first required deceleration 64 second required deceleration 72 middle deceleration 101 electric brake system 103 FR, 103 RL, 103 RR, 103 FL wheel cylinder 112 brake pedal

Claims (7)

An engine brake control unit for controlling generation of an engine brake of the vehicle;
A friction brake control unit for controlling an electric brake system in which a brake pedal is connected and a hydraulic pressure is supplied to a wheel cylinder of each wheel of the vehicle by an operation of an actuator to generate a friction brake;
A deceleration detection unit that detects an actual deceleration of the vehicle;
An automatic brake request unit that automatically requests a brake to be operated without operating the brake pedal so that the vehicle takes a necessary distance from a leading vehicle;
When the requested deceleration requested by the automatic brake request unit is less than a predetermined value, the engine brake control unit is instructed to generate a braking force by the engine brake, and the requested deceleration is equal to or greater than the predetermined value A brake selection unit that controls the friction brake control unit to generate a braking force by the friction brake by the electric brake system;
Immediately after switching from the engine brake to the friction brake in the brake selection unit, the required deceleration requested in the automatic brake request unit is once brought close to the actual deceleration detected in the deceleration detection unit, and automatic braking is performed again. A braking force control system, comprising: a required deceleration changing unit for performing control to restore the required deceleration requested by a requesting unit. Assuming that the required deceleration immediately before the brake selection unit switches from the engine brake to the friction brake is a first required deceleration, and the required deceleration immediately after the switching is a second required deceleration.
2. The apparatus according to claim 1, wherein the required deceleration changing unit sets the second required deceleration to a deceleration lower than an intermediate deceleration intermediate between the first required deceleration and the actual deceleration. The braking force control system described in.   The braking force control system according to claim 2, wherein the required deceleration changing unit makes the second required deceleration similar to the actual deceleration.   The requested deceleration changing unit is configured to request the automatic brake request based on an absolute value of a reduction rate at the time of reducing the requested deceleration from the first requested deceleration to the second requested deceleration, and the second requested deceleration. The braking force control system according to claim 3, wherein an absolute value of an increase rate at which the required deceleration is increased toward the required deceleration required by the unit is made different.   The braking force control system according to claim 4, wherein the required deceleration changing unit makes the increase rate smaller than the reduction rate. And an emergency brake request unit that automatically requests a brake to operate without operating the brake pedal in order to avoid a collision with an obstacle in front of the vehicle.
The requested deceleration changing unit, when requested by the emergency brake request unit to operate the brake, reduces the requested deceleration requested by the automatic brake request unit from the first requested deceleration to the second requested deceleration. The braking force control system according to any one of claims 2 to 5, wherein the speed is prohibited. A difference calculation unit configured to calculate a difference between the first required deceleration degree and the actual deceleration degree;
When the difference calculated by the difference calculation unit is less than a predetermined value, the required deceleration change unit requests the required deceleration requested by the automatic brake request unit from the first required deceleration to the second request deceleration. The braking force control system according to any one of claims 2 to 6, wherein the braking force control system is prohibited.

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