JP6701656B2 - Vehicle braking control device - Google Patents

Description

  The present invention relates to a vehicle braking control device.

  BACKGROUND ART Conventionally, speed maintenance control is known in which a braking force is adjusted so that the speed of a vehicle on a downhill on a slope does not exceed a target speed. For example, in Patent Document 1, when the driver operates the accelerator pedal to accelerate while the speed maintaining mode is being executed, a map that associates the slope angle of the slope and the target speed with the speed after acceleration can be updated. Have been described.

  Generally, a driver increases the speed of the vehicle by operating the accelerator pedal when he feels that the speed of the vehicle is slow while descending a slope, and releases the accelerator pedal operation when the speed of the vehicle reaches a desired speed. Here, the configuration described in Patent Document 1 controls the braking force so that the vehicle speed becomes equal to or lower than the target speed when the vehicle speed exceeds the target speed. Therefore, when the driver operates the accelerator pedal to accelerate the vehicle while the speed maintaining mode is being executed, the speed of the vehicle may temporarily exceed the speed desired by the driver.

  In this regard, as described in Patent Document 2, it is possible to apply the braking force according to the pedal return direction operation amount of the accelerator pedal operation amount. However, depending on the size of the slope of the downhill road, the braking force may become excessive or insufficient, which may cause a problem that the occupant feels uncomfortable.

JP, 2006-213294, A JP, 2010-285033, A

  The present invention has been made to solve the above problem, and an object of the present invention is to provide a braking control device for a vehicle that improves speed maintaining performance in speed maintaining control of a vehicle while going down a slope.

  A braking control device for a vehicle according to the present invention includes a braking device that applies a braking force to the vehicle, and a control device that executes a speed maintaining control that adjusts the braking force so that the speed of the vehicle does not exceed a target speed. Prepare A feature of the braking control device according to the present invention is that the control device obtains an accelerator pedal operation amount of a driver and a road surface slope of a downhill road on which the vehicle is located, and calculates the accelerator pedal operation amount and the road surface slope. On the basis of the above, the braking device is controlled so that the braking force is applied to the vehicle from a time point when the magnitude of the change in the accelerator pedal operation amount in the pedal returning direction is smaller as the road surface gradient is larger. It has been done.

  Here, the control device changes the target speed according to an accelerator pedal operation of a driver, and the vehicle at a time point when the magnitude of the change in the accelerator pedal operation amount in the pedal return direction is smaller as the road surface gradient is larger. The speed may be set to the new target speed after the accelerator pedal operation is released.

  According to the features of the present invention described above, when the slope of the downhill road is relatively large, the braking force is applied at an earlier timing after the operation of the accelerator pedal in the pedal returning direction is started. When the slope of the downhill road is relatively small, the braking force is applied at a later timing after the operation of the accelerator pedal in the pedal returning direction is started. Therefore, depending on the road slope, when the road slope on the downhill road is large and the vehicle is easy to accelerate, it is possible to prevent the speed of the vehicle from exceeding the speed desired by the driver, and it is also possible to prevent the braking force from being excessive or insufficient. The problem of giving an occupant a feeling of strangeness is less likely to occur.

1 is a schematic configuration diagram of a vehicle equipped with a vehicle braking control device according to an embodiment of the present invention. It is a schematic block diagram of the braking device shown in FIG. 3 is a flowchart of speed maintenance control executed by the control device shown in FIG. 1. 6 is an example of a map in which an accelerator pedal return amount and a precharge braking force are associated with each other. 3 is a time chart showing the operation of the vehicle braking control device according to the embodiment of the present invention. 8 is a time chart showing the operation of the vehicle braking control device according to the modification of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a vehicle equipped with a vehicle braking control device 10 according to an embodiment of the present invention. Hereinafter, “**” added to the end of various variables and the like is added to the end of various variables and the like to indicate which of the wheels FR, FL, RR, and RL the various variables and the like relate to. It is a comprehensive notation such as "fr" or "fl".

  The vehicle braking control device 10 includes a braking device 30 that generates a friction braking force by wheel cylinder hydraulic pressure on the wheels **. As shown in FIG. 2, the braking device 30 includes a brake hydraulic pressure generation unit 32 that generates hydraulic pressure according to the stroke (or pedaling force) of the brake pedal BP, and a wheel cylinder W** arranged on a wheel **. Brake fluid pressure adjusting sections 33 to 36 capable of adjusting the wheel cylinder fluid pressure supplied to the wheel cylinder, and a return brake fluid supplying section 37. In the wheel **, the friction braking member (brake pad) is pressed against the brake disc that rotates integrally with the wheel by a pressing force corresponding to the wheel cylinder hydraulic pressure of W**, so that the friction control according to the wheel cylinder hydraulic pressure is performed. Power is given.

  The brake fluid pressure generation unit 32 includes a vacuum booster VB that responds to the brake pedal BP and a master cylinder MC that is connected to the vacuum booster VB. The vacuum booster VB uses the air pressure (negative pressure) in the intake pipe of the engine (not shown) to assist the operating force of the brake pedal BP at a predetermined ratio and transmit the assisted operating force to the master cylinder MC. Has become.

  The master cylinder MC has two output ports, receives the supply of the brake fluid from the reservoir RS, and outputs the hydraulic pressure (master cylinder hydraulic pressure Pm) corresponding to the assisted operating force to the two ports. It is supposed to occur from each. Since the configurations and operations of the master cylinder MC and the vacuum booster VB are well known, their detailed description will be omitted here.

  A normally-open linear solenoid valve PC1 is provided between one port of the master cylinder MC and the upstream parts of the brake fluid pressure adjusting parts 33 and 34, and the other port of the master cylinder MC and the brake fluid pressure adjusting part. A normally open linear solenoid valve PC2 is interposed between the upstream parts of the parts 35 and 36. Details of the linear solenoid valves PC1 and PC2 will be described later.

  The brake fluid pressure adjusting units 33 to 36 are a pressure increasing valve PU** which is a 2-port 2-position switching type normally open electromagnetic on-off valve and a pressure reducing valve PD** which is a 2-port 2-position switching normally closing electromagnetic on-off valve. It consists of and. The pressure increasing valve PU** can connect/disconnect the upstream side of the corresponding adjusting portion of the brake fluid pressure adjusting portions 33 to 36 and the wheel cylinder W**. The pressure reducing valve PD** can connect and disconnect the wheel cylinder W** and the corresponding reservoir among the reservoirs RS1 and RS2. As a result, by controlling the pressure increasing valve PU** and the pressure reducing valve PD**, the hydraulic pressure of the wheel cylinder W** (wheel cylinder hydraulic pressure Pw**) can be increased, maintained, and reduced. There is.

  The return brake fluid supply unit 37 includes a DC motor MT and two hydraulic pumps (gear pumps) HP1 and HP2 that are simultaneously driven by the motor MT. The hydraulic pumps HP1 and HP2 respectively pump up the brake fluid in the reservoirs RS1 and RS2 that has been returned from the pressure reducing valve PD**, and supply the pumped brake fluid to the upstream portions of the brake hydraulic pressure adjusting units 33 to 36, respectively. It is like this.

  Next, the normally open linear solenoid valves PC1 and PC2 will be described. A force in the opening direction based on the urging force from a coil spring (not shown) is constantly acting on the valve elements of the normally-open linear solenoid valves PC1 and PC2, and the corresponding adjusting units of the brake fluid pressure adjusting units 33 to 36 are provided. In the opening direction based on the differential pressure (linear valve differential pressure ΔP) obtained by subtracting the master cylinder hydraulic pressure Pm from the pressure in the upstream portion of the current, and the current supplied to the normally open linear solenoid valves PC1 and PC2 (command current The force in the closing direction based on the suction force that increases proportionally with Id) acts.

  As a result, it is determined that the command differential pressure ΔPd, which is the command value of the linear valve differential pressure ΔP, increases proportionally according to the command current Id. The normally open linear solenoid valves PC1 and PC2 are closed when ΔPd is larger than ΔP, while they are opened when ΔPd is smaller than ΔP. As a result, when the hydraulic pumps HP1 and HP2 are driven, the brake fluid upstream of the corresponding one of the brake fluid pressure adjusting units 33 to 36 is the corresponding electromagnetic solenoid of the normally open linear solenoid valves PC1 and PC2. By flowing through the valve to the corresponding port side of the master cylinder MC, the linear valve differential pressure ΔP can be adjusted so as to match the command differential pressure ΔPd. The brake fluid that has flowed into the corresponding port side of the master cylinder MC is returned to the corresponding reservoir of the reservoirs RS1 and RS2.

  In other words, when the motor MT (hence, the hydraulic pumps HP1 and HP2) is driven, the linear valve differential pressure ΔP can be controlled according to the command current Id of the normally open linear solenoid valves PC1 and PC2. ing. The pressure at the upstream portion of the brake fluid pressure adjustment units 33 to 36 is a value (Pm+ΔP) obtained by adding the linear valve differential pressure ΔP to the master cylinder fluid pressure Pm. In addition, after the driving of the hydraulic pumps HP1 and HP2 is stopped in the state where the linear valve differential pressure ΔP is adjusted to a value larger than zero, the linear valve differential pressure is adjusted by adjusting the command current Id in the decreasing direction. ΔP can be continuously adjusted only in the decreasing direction.

  When the normally open linear solenoid valves PC1 and PC2 are in the non-excited state (that is, when the command current Id is set to "0"), the PC1 and PC2 are kept open by the biasing force of the coil spring. At this time, the linear valve differential pressure ΔP becomes “0”, and the pressure at the upstream portion of the brake fluid pressure adjusting units 33 to 36 becomes equal to that of the master cylinder Pm.

  With the configuration described above, the braking device 30 is composed of two systems of hydraulic circuits, a system relating to the left and right front wheels FR and FL and a system relating to the left and right rear wheels RR and RL. In the braking device 30, the wheel cylinder hydraulic pressure Pw** is adjusted to a value equal to the master cylinder hydraulic pressure Pm when all the solenoid valves are in the non-excited state.

  On the other hand, in this state, by driving the motor MT (hence, the hydraulic pressure pumps HP1 and HP2) and controlling the normally open linear solenoid valves PC1 and PC2, the wheel cylinder hydraulic pressure Pw** becomes the hydraulic pressure (Pm+ΔP). Adjusted to. Further, by controlling the pressure increasing valve PU** and the pressure reducing valve PD**, the wheel cylinder hydraulic pressure Pw** can be adjusted independently for each wheel. That is, the braking force applied to the wheels** can be adjusted independently for each wheel regardless of the operation of the brake pedal BP by the driver.

  Referring again to FIG. 1, the braking control device 10 includes a wheel speed sensor 41** that detects the rotational speed of a wheel and a brake switch 42 that selectively outputs a signal according to whether or not the brake pedal BP is operated. , A master cylinder hydraulic pressure sensor 44 (see FIG. 2) that detects the master cylinder hydraulic pressure Pm, and another sensor group 43. The other sensor group 43 includes a longitudinal acceleration sensor, a lateral acceleration sensor, an accelerator pedal sensor, a road surface gradient sensor, and the like.

  The braking control device 10 further includes a control device 50. The control device 50 is a microcomputer including a CPU 51, a ROM 52, a RAM 53, an interface 55 and the like.

  The interface 55 is connected to the sensors/switches 41 to 44, supplies signals from the sensors/switches 41 to 44 to the CPU 51, and in response to an instruction from the CPU 51, an electromagnetic valve (normally open linear valve) of the braking device 30. Driving signals are sent to the solenoid valves PC1 and PC2, the pressure increasing valve PU**, the pressure reducing valve PD**), and the motor MT. With the above configuration, the control device 50 can acquire the driver's accelerator pedal operation amount and the road surface gradient. In addition to the road surface gradient obtained based on the signal from the road surface gradient sensor, the vehicle acceleration calculated based on the signal from the wheel speed sensor 41** and the acceleration based on the signal from the longitudinal acceleration sensor are used. It may be acquired based on the difference of.

  Next, the speed maintenance control executed by the control device 50 will be described. When a predetermined condition is satisfied, the control device 50 executes speed maintenance control that adjusts the braking force so that the vehicle speed does not exceed the target speed. Hereinafter, an operation in the case where the driver operates the accelerator pedal while the speed maintaining control is being executed by the control device 50 of the present embodiment will be described.

  As shown in FIG. 3, during execution of the speed maintaining control, the control device 50 determines whether the accelerator is ON, that is, whether or not the driver operates the accelerator pedal (step S10). When the driver operates the accelerator pedal (step S10: YES), the control device 50 determines whether the accelerator pedal is released, that is, whether the accelerator pedal operation amount changes in the pedal returning direction (step S20). When the control device 50 determines that the accelerator pedal is in the releasing tendency (step S20: YES), the control device 50 acquires the accelerator pedal return amount, which is the magnitude of the change in the accelerator pedal operation amount in the pedal return direction (step S30).

  The control device 50 determines whether or not there is an intention to release the accelerator pedal, that is, an intention to release the accelerator pedal operation of the driver, based on the acquired accelerator pedal return amount (step S40). When the control device 50 determines that there is an intention to release the accelerator pedal (step S40: YES), the control device 50 acquires the precharge braking force (step S50).

  The processes of steps S40 and S50 will be described in detail with reference to FIG. The ROM 52 stores a map associating the accelerator pedal return amount with the precharge braking force as shown in FIG. The precharge braking force is set in accordance with the road surface slope of the downhill road on which the vehicle is located so that the larger the road surface slope, the smaller the accelerator pedal return amount becomes. Specifically, when the slope gradient is 30%, the precharge braking force rises when the accelerator pedal return amount becomes a, and when the slope gradient is 20%, the precharge braking force rises when the accelerator pedal return amount becomes b (>a). When the slope gradient is 10%, the precharge braking force rises when the accelerator pedal return amount becomes c (>b). Further, the value of the precharge braking force with respect to the same accelerator pedal return amount is set to be larger as the road slope on the downhill road is larger (for example, refer to the accelerator pedal return amount d).

  The control device 50 refers to such a map in steps S40 and S50 described above, and when the accelerator pedal return amount reaches a value at which the precharge braking force set according to the road surface slope rises, the release intention of the accelerator pedal is determined. It is determined that there is a precharge braking force corresponding to the accelerator pedal return amount. For example, in the case of a slope gradient of 20%, when the accelerator pedal return amount becomes b, the control device 50 proceeds from step S40 to step S50 and starts acquiring precharge braking force.

  FIG. 5 is a time chart showing the operation of the braking control device 10 of the present embodiment. Here, it is assumed that the road surface slope of the downhill road on which the vehicle is located is constant. Before the accelerator pedal operation is started by the driver at time t1, the wheel cylinder hydraulic pressure corresponding to the braking force required to maintain the vehicle speed at the target speed is generated. As the slope gradient increases, the component of the gravitational acceleration acting in the vehicle downhill direction increases, so the wheel cylinder hydraulic pressure for maintaining the vehicle speed at the target speed also increases.

  At time t1, when the driver operates the accelerator pedal, the wheel cylinder hydraulic pressure is decreased to increase the vehicle speed. This accelerates the vehicle. At time t2, the operation of the accelerator pedal in the pedal returning direction is started. Based on the above-mentioned map, when the accelerator pedal return amount reaches a value at which the precharge braking force set according to the road surface gradient rises, the precharge braking force corresponding to the accelerator pedal return amount is acquired. Then, the wheel cylinder hydraulic pressure is generated according to the acquired precharge braking force. When the precharge braking force reaches the braking force when the accelerator is ON (time t1) (see FIG. 4), the wheel cylinder hydraulic pressure is maintained at the magnitude at that time.

  As described above, according to the present embodiment, the pre-charge braking force is applied in accordance with the road surface gradient before the time t3 when the accelerator pedal operation is released. Therefore, depending on the road slope, when the road slope on the downhill road is large and the vehicle is easy to accelerate, it is possible to prevent the speed of the vehicle from exceeding the speed desired by the driver, and it is also possible to prevent the braking force from being excessive or insufficient. The problem of giving an occupant a feeling of strangeness is less likely to occur.

  The present invention is not limited to the above embodiment. One modification will be described with reference to FIG.

  Before the accelerator pedal operation is started by the driver at time t1, the target speed is set to a predetermined speed (for example, 10 km/h). At time t1, when the driver operates the accelerator pedal, the target speed is changed to increase as the vehicle speed increases. As the slope gradient increases, the component of the gravitational acceleration acting in the vehicle downhill direction increases, so that the increase in the target speed with the increase in the vehicle speed also increases.

  At time t2, the operation of the accelerator pedal in the pedal returning direction is started. As shown in FIG. 6, according to the modified example, the vehicle speed at the time when the change in the accelerator pedal operation amount in the pedal return direction is smaller according to the road surface gradient is smaller after the accelerator pedal operation is released. Is set to a new target speed of. Specifically, in the modified example, according to the road surface gradient, the larger the road surface gradient, the earlier the vehicle speed is latched before the time t3 when the accelerator pedal operation is released, and the new target speed after that is latched. Become. Accordingly, also in the modified example, the same operational effect as that of the above-described embodiment can be obtained.

  Further, the above embodiment and the modified examples may be combined. According to the present invention, it is possible to improve the speed maintaining performance in the speed maintaining control of the vehicle while going down a slope.

  10... Braking control device, 30... Braking device, 50... Control device

Claims (2)

A braking control device for a vehicle, comprising: a braking device that applies a braking force to the vehicle;
The control device is
Acquiring the accelerator pedal operation amount of the driver and the road surface slope of the downhill road where the vehicle is located,
Based on the accelerator pedal operation amount and the road surface gradient, the braking force is applied to the vehicle from a time point when the change in the accelerator pedal operation amount in the pedal return direction is smaller as the road surface gradient is larger. A braking control device for a vehicle, which is configured to control the braking device. The braking control device for a vehicle according to claim 1,
The control device is
Change the target speed according to the driver's accelerator pedal operation,
The larger the road surface gradient, the smaller the magnitude of the change in the pedal return direction of the accelerator pedal operation amount, the speed of the vehicle is configured to be the new target speed after the accelerator pedal operation is released, Vehicle braking control device.