Vehicle brake control device

Abstract

A vehicle brake control device (10) capable of early determining whether or not an unstable behavior accompanying rotation has occurred in a vehicle is provided with: a control unit (12) that performs, in a switchable manner, a braking force generation control (T1) for generating a braking force by a braking device (5) mounted in the vehicle (1), or a braking force release control (T2) for releasing the braking force generated by the braking device; and a determination unit (14) that, on the basis of a determination value (D) determined using a lateral acceleration (Gy) indicating a state occurring in the vehicle and a friction coefficient (mu) indicating a state of a road surface in which wheels (3) of the vehicle contact, determines that an unstable behavior accompanying rotation about a rotation axis along the vertical direction has occurred in the vehicle, if the determination value is equal to or greater than a predetermined value (D0), and determines that the unstable behavior has occurred in the vehicle if the determination value is not less than the predetermined value (D0). The control unit causes the brake device to generate a brake force by executing a brake force generation control (T1) on the basis of determining that the unstable behavior has occurred.

Description

Technical Field

[0001] The present disclosure relates to a brake control device for a vehicle. Background Art

[0002] Conventionally, for example, there is known an anti-skid control device (hereinafter referred to as "conventional control device") disclosed in Patent Document 1. The conventional control device determines whether unstable behavior accompanied by rotation occurs in the vehicle based on the reduction gradients of the wheel speed and the vehicle body speed as the decompression mode is continued according to the anti-skid control.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 10-35464

[0004] In the conventional control device, whether an unstable behavior accompanied by rotation has occurred in the vehicle is determined based on the decompression mode according to the anti-skid control. In addition, for example, in order to eliminate the unstable behavior in the vehicle midway and to distinguish a turn that does not lead to unstable behavior, the determination of unstable behavior takes time. In this regard, in the conventional control device, for example, if the braking performed by the driver is delayed, the time taken until the decompression mode is started is also delayed, and there is a case where the time required for determination cannot be ensured. As a result, in the conventional control device, it may be impossible to determine the unstable behavior. Summary of the invention

[0005] An object of the present disclosure is to provide a vehicle brake control device that can quickly determine whether unstable behavior accompanied by rotation has occurred in the vehicle.

[0006] The vehicle braking control device disclosed in the present invention comprises: a control unit, which can switchably execute braking force generation control for causing a braking device mounted on the vehicle to generate braking force, or braking force release control for releasing the braking force generated by the braking device; and a determination unit, which determines whether unstable behavior accompanied by rotation around a rotation axis along a vertical direction has occurred in the vehicle based on a determination value determined by a state generated in the vehicle and a state of a road surface contacted by the vehicle's wheels, and the control unit executes braking force generation control based on the determination that unstable behavior has occurred, thereby causing the braking device to generate braking force.

[0007] According to the vehicle brake control device disclosed in the present invention, the determination unit can determine whether an unstable behavior accompanied by rotation has occurred in the vehicle based on the determination value. That is, in the vehicle brake control device, even before braking, it is possible to determine whether an unstable behavior accompanied by rotation has occurred in the vehicle as early as possible. As a result, the vehicle brake control device can cause the control unit to quickly perform braking force generation control, and as a result, the vehicle that has caused unstable behavior accompanied by rotation can be stopped quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a simplified structural diagram of a vehicle and a brake control device for the vehicle.

[0009] Figure 2 It is a graph showing the relationship between the slip ratio and the friction coefficient.

[0010] Figure 3 This is a diagram for explaining unstable behavior associated with rotation.

[0011] Figure 4 It is a flow chart of the brake control program.

[0012] Figure 5 This is a flowchart of a brake control program according to a modification.

[0013] Description of Reference Numerals

[0014] 1…vehicle; 2…body; 3…wheel; 4…steering device; 5…brake device; 10…vehicle brake control device; 11…sensor group; 115…lateral acceleration sensor (state quantity detection unit); 116…yaw rate sensor (state quantity detection unit); 12…control unit; 13…road surface state detection unit (physical quantity detection unit); 14…judgment unit; 15…instruction unit; Vw…wheel speed; Vb…body speed; Gy…lateral acceleration (state quantity); YR…yaw rate (state quantity); μ…friction coefficient (physical quantity); D…judgment value; D0…specified value; α…reduction gradient; T1…braking force generation control; T2…braking force release control. DETAILED DESCRIPTION

[0015] Hereinafter, a vehicle brake control device 10 as one embodiment of the present disclosure will be described in detail with reference to the drawings. In addition to the embodiment described below, the vehicle brake control device can be implemented in various forms after various changes and improvements based on the knowledge of those skilled in the art.

[0016] The vehicle brake control device 10 is applied to Figure 1 The vehicle 1 is shown. The vehicle 1 may be driven manually by a driver or may be driven automatically. In the embodiment described below, the case where the vehicle 1 is driven manually by the driver is described as an example.

[0017] The vehicle 1 includes a vehicle body 2 and wheels 3. The vehicle body 2 is supported by the wheels 3 via a suspension mechanism (not shown). The wheels 3 include a right front wheel 31, a left front wheel 32, a right rear wheel 33, and a left rear wheel 34.

[0018] The vehicle 1 is also provided with a steering device 4. In the present embodiment, the steering device 4 is configured to steer the right front wheel 31 and the left front wheel 32. The vehicle 1 is also configured to drive the right front wheel 31 and the left front wheel 32, the right rear wheel 33 and the left rear wheel 34, or the right front wheel 31, the left front wheel 32, the right rear wheel 33 and the left rear wheel 34 by a driving force from a driving force source (an engine or an electric motor, etc.) not shown.

[0019] The vehicle 1 is provided with a brake device 5 for generating braking force on each wheel 3. The brake device 5 is provided with a right front wheel brake 51, a left front wheel brake 52, a right rear wheel brake 53, and a left rear wheel brake 54. In addition, in the present embodiment, the brake device 5 is provided with a brake pedal 55, a master cylinder 56, a hydraulic circuit 57, and a brake pipe 58. The right front wheel brake 51, the left front wheel brake 52, the right rear wheel brake 53, and the left rear wheel brake 54 can be exemplified by a disc brake or a drum brake, and can also be configured to be capable of regenerative braking.

[0020] The master cylinder 56 delivers the working oil under pressure in response to the braking operation performed by the driver by stepping on the brake pedal 55. Although the detailed illustration is omitted for the hydraulic circuit 57, it includes a reservoir, a pump, and various valve devices, and functions as a brake actuator. The hydraulic circuit 57 adjusts the working oil pressure of the working oil added to the brake pipe 58, for example, according to the instruction from the control unit 12 of the vehicle brake control device 10 described later.

[0021] That is, the hydraulic circuit 57 can generate braking forces on the right front wheel brake 51, the left front wheel brake 52, the right rear wheel brake 53, and the left rear wheel brake 54 respectively by the pressure increase mode for increasing the working oil pressure. In addition, the hydraulic circuit 57 can release the braking forces on the right front wheel brake 51, the left front wheel brake 52, the right rear wheel brake 53, and the left rear wheel brake 54 respectively by the pressure reduction mode for reducing the working oil pressure.

[0022] like Figure 1 As shown, the vehicle brake control device 10 is mounted on the vehicle 1. The vehicle brake control device 10 is configured to include a sensor group 11, a control unit 12, a road surface state detection unit 13, a determination unit 14, and an instruction unit 15. Here, the vehicle brake control device 10 is configured with a computer device having a CPU, a ROM, a RAM, and various interfaces as main components. The CPU sequentially executes a prescribed program including a brake control program described later, and performs data reading, numerical calculations, and output of calculation results. The ROM stores programs and mappings executed by the CPU. The RAM temporarily stores data, etc. Various interfaces are connected to the sensor group 11, respectively.

[0023] like Figure 1As shown in FIG. 1 , the sensor group 11 includes a wheel speed sensor 111, a wheel speed sensor 112, a wheel speed sensor 113, and a wheel speed sensor 114. In addition, the sensor group 11 includes a lateral acceleration sensor 115 and a yaw rate sensor 116 as a state quantity detection unit for detecting a state quantity of the vehicle 1 having a component in the left-right direction of the vehicle 1. Furthermore, the sensor group 11 includes a steering angle sensor 117 and a brake sensor 118.

[0024] The wheel speed sensor 111 detects a wheel speed Vwfr which is the rotation speed of the right front wheel 31. The wheel speed sensor 112 detects a wheel speed Vwfl which is the rotation speed of the left front wheel 32. The wheel speed sensor 113 detects a wheel speed Vwrr which is the rotation speed of the right rear wheel 33. The wheel speed sensor 114 detects a wheel speed Vwrl which is the rotation speed of the left rear wheel 34. In the following description, when the wheel speeds Vwfr, Vwfl, Vwrr, and Vwrl are not distinguished, they may be simply referred to as "wheel speed Vw".

[0025] The lateral acceleration sensor 115 detects a lateral acceleration Gy, which is a state quantity of the vehicle 1 and which indicates a state occurring in the vehicle 1 and has a component in the left-right direction of the vehicle 1. The lateral acceleration Gy is a state quantity occurring in the left-right direction of the vehicle 1. The yaw rate sensor 116 detects a yaw rate YR, which is a state quantity of the vehicle 1 and which indicates a state occurring in the vehicle 1 and has a component in the left-right direction of the vehicle 1. The yaw rate YR is a state quantity occurring around the center of gravity CG of the vehicle 1.

[0026] The steering angle sensor 117 detects the steering angle TA of the right front wheel 31 and the left front wheel 32 steered by the steering device 4. Here, for example, a predetermined relationship is established between the steering angle TA and the amount of operation of the steering wheel (steering angle) by the driver. Therefore, the steering angle sensor 117 can also detect the steering angle TA based on the amount of operation of the steering wheel (steering angle), for example.

[0027] When the driver performs a braking operation on the brake pedal 55, the brake sensor 118 outputs an operation signal BO indicating the operation state of the brake request. That is, the brake sensor 118 detects the operating oil pressure of the master cylinder 56 and the respective operating oil pressures of the brake pipe 58 corresponding to the braking operation on the brake pedal 55 and outputs the operation signal BO.

[0028] The control unit 12 performs a braking force generation control T1 for generating a braking force in the above-mentioned pressure-increasing mode on the braking device 5 mounted on the vehicle 1. In addition, the control unit 12 performs a braking force release control T2 for releasing the braking force in the pressure-reducing mode on the braking device 5. Moreover, the control unit 12 can switch between the braking force generation control T1 and the braking force release control T2.

[0029] Here, in the present embodiment, the control unit 12 switches between the braking force generation control T1 and the braking force release control T2 according to the well-known anti-skid control (also referred to as "ABS control") for preventing the rotation stop state, i.e., the locking state, of the wheel 3. In addition, the control unit 12 outputs information indicating the braking force generation control T1 or the braking force release control T2 being executed to the determination unit 14.

[0030] The control unit 12 normally determines the required deceleration based on the amount of operation of the brake pedal 55 by the driver, the wheel speed Vw of the wheel 3, the body speed Vb of the vehicle 1 which can be estimated using the wheel speed Vw, and the like. Furthermore, the control unit 12 controls the hydraulic circuit 57 so that the actual deceleration matches the required deceleration in order to generate braking forces at the wheels 3 respectively. On the other hand, when the wheels 3 are in a locked state based on the wheel speed Vw and the body speed Vb, the control unit 12 controls the hydraulic circuit 57 by switching, for example, from the braking force generation control T1 to the braking force release control T2 according to the ABS control.

[0031] The road surface state detection unit 13 uses the wheel speed Vw detected by the wheel speed sensors 141-144 to detect a physical quantity indicating the state of the road surface that the wheels 3 are in contact with, or more specifically, the state between the wheels and the road surface. That is, the road surface state detection unit 13 functions as a physical quantity detection unit, and detects the friction coefficient μ indicating the magnitude of friction of the road surface that the wheels 3 are in contact with as a physical quantity.

[0032] Here, for the inference calculation of the friction coefficient μ, a well-known calculation method widely used in the past can be used. Therefore, an example of the inference calculation of the friction coefficient μ by the road surface state detection unit 13 is simply shown below. The road surface state detection unit 13 estimates the vehicle body speed Vb based on the wheel speed Vw. Moreover, the road surface state detection unit 13 estimates and calculates the respective slip rates S of the wheels 3 by dividing the deviation between the wheel speed Vw and the vehicle body speed Vb by the vehicle body speed Vb. In addition, the slip rate S can also be inferred and calculated based on the acceleration of the wheel speed Vw, the front-rear acceleration of the vehicle 1, or the lateral acceleration Gy, etc.

[0033] The road surface state detection unit 13 detects the relationship between the friction coefficient μ of the road surface and the slip ratio S of the wheel 3. Figure 2 The road surface friction coefficient μ corresponding to the calculated slip ratio S of the wheel 3 is estimated and calculated based on the determined S-μ characteristic. Then, the road surface state detection unit 13 outputs the estimated and detected road surface friction coefficient μ to the determination unit 14.

[0034] like Figure 1As shown, the determination unit 14 determines whether an unstable behavior, such as a spinning behavior or a drifting behavior, that is accompanied by rotation about a rotation axis that is a rotation axis along the vertical direction and passes through the center of gravity CG of the vehicle 1 occurs in the vehicle 1. When a determination value D determined using a lateral acceleration Gy (state quantity) that indicates a state that occurs in the vehicle 1 and a friction coefficient μ (physical quantity) that indicates a state of a road surface that the wheels 3 contact is greater than or equal to a predetermined value D0, the determination unit 14 determines that an unstable behavior that is accompanied by rotation occurs in the vehicle 1.

[0035] Here, the determination value D of the present embodiment is the ratio of the state quantity to the physical quantity, that is, the ratio of the lateral acceleration Gy to the friction coefficient μ (Gy / μ). Moreover, the determination value D has a tendency to become a larger value as the friction coefficient μ is smaller or the lateral acceleration Gy is larger. Therefore, when the determination value D becomes larger, unstable behavior accompanied by rotation is likely to occur in the vehicle 1. On the other hand, the determination value D has a tendency to become a smaller value as the friction coefficient μ is larger or the lateral acceleration Gy is smaller. Therefore, when the determination value D becomes smaller, it is easy to recover from unstable behavior to stable behavior.

[0036] As described later, the determination unit 14 of the present embodiment determines whether a first condition has occurred in which the decrease gradient α of the vehicle body speed Vb of the vehicle 1 (vehicle body 2) becomes smaller relative to the decrease gradient of the wheel speed Vw of the wheel 3 of the vehicle 1, and the difference between the wheel speed Vw and the vehicle body speed Vb becomes larger (see Figure 3 ). In addition, as described later, when the first condition occurs, the determination unit 14 of the present embodiment determines whether a second condition occurs. In the second condition, the braking device 5 performs the braking force release control T2 (see FIG. 1 ) according to the wheel speed Vw, more specifically, according to the locked state of the wheel 3. Figure 3 ). When the first condition and the second condition occur and the determination value D is greater than or equal to the predetermined value D0 for a certain period of time, the determination unit 14 of the present embodiment determines that an unstable behavior accompanied by rotation occurs in the vehicle 1 and outputs determination information J to the instruction unit 15.

[0037] The command unit 15 inputs the determination information J from the determination unit 14. When the vehicle 1 has unstable behavior according to the determination information J, the command unit 15 outputs a braking command C to the control unit 12 to instruct the brake device 5 to generate a braking force. Thus, the control unit 12 executes the braking force generation control T1 to cause the brake device 5 to generate a braking force.

[0038] In addition, in the present embodiment, the control unit 12 terminates the braking force release control T2 being executed (continuing) in the second condition, that is, terminates the anti-skid control, and quickly executes the braking force generation control T1 according to the braking command C. As a result, the right front wheel brake 51, the left front wheel brake 52, the right rear wheel brake 53, and the left rear wheel brake 54 of the braking device 5 generate braking forces on all wheels 3.

[0039] Next, the unstable behavior accompanying the rotation generated in the vehicle 1 will be described. Figure 3 As shown, when the vehicle 1 is moving forward, if the friction coefficient μ of the road surface decreases, the lateral acceleration Gy is generated in the vehicle 1, or the steering angle TA becomes larger, the vehicle 1 sometimes produces unstable behavior accompanied by rotation around the rotation axis passing through the center of gravity CG, such as spinning behavior.

[0040] In this case, Figure 3 In the "state A" shown, the vehicle 1 starts to rotate (or turn), and as it gradually approaches a right angle relative to the traveling direction, the reaction force input from the road surface to the wheel 3 becomes smaller. Therefore, in "state A", as shown by the long dashed line, the wheel speed Vw of the wheel 3 decreases rapidly. And, if the vehicle 1 moves toward the right angle, the reaction force from the road surface disappears, and as a result, the wheel speed Vw becomes "0", that is, the wheel 3 stops rotating.

[0041] Here, in "state A", if the driver performs a braking operation on the brake pedal 55, the control unit 12 attempts to perform the braking force generation control T1 in the initial stage in the pressure increase mode based on the operation signal BO. However, the wheel speed Vw is "0", in other words, a locked state in which the slip ratio S increases occurs, and thus the control unit 12 performs the braking force release control T2 in the pressure reduction mode according to the anti-skid control.

[0042] If the vehicle 1 generates unstable behavior accompanied by rotation, as in Figure 3 As shown by the thick solid line in FIG. 1 , the vehicle body speed Vb is reduced at a reduction gradient α determined based on the friction coefficient μ of the road surface in order to avoid a sudden reduction. On the other hand, if the vehicle 1 generates an unstable behavior accompanied by rotation, the reaction force from the road surface to the wheel 3 is reduced as described above, so the wheel speed Vw is reduced at a reduction gradient greater than the reduction gradient α. Therefore, if the vehicle 1 generates an unstable behavior accompanied by rotation, the vehicle body speed Vb cannot catch up with the reduced wheel speed Vw and deviates upward.

[0043] Furthermore, if the vehicle body speed Vb deviates upward relative to the wheel speed Vw, and a deviation occurs between the wheel speed Vw and the vehicle body speed Vb, the wheel speed Vw will not return to the vehicle body speed Vb. As a result, the locked state of the wheel 3 continues, so the control unit 12 continues to perform the braking force release control T2 in the decompression mode according to the anti-skid control. Therefore, in "state A", the driver feels a sense of discomfort, a so-called plate brake feeling, with respect to the decrease in the vehicle body speed Vb relative to the braking operation of the brake pedal 55.

[0044] In addition, Figure 3 In the "state B" of FIG. 1 , as indicated by the long dashed line, for example, since the reaction force from the road surface restores the input to part of the wheel 3, the wheel speed Vw increases and the locked state is eliminated. However, even if the locked state is eliminated, the unstable behavior may unexpectedly continue further. Moreover, in Figure 3 In "state C", for example, even if the braking force generation control T1 is executed corresponding to the wheel 3 that has eliminated a part of the locked state, the braking force for stopping the reverse vehicle 1, in other words, the deceleration is insufficient, resulting in the driver feeling a sense of idling and acceleration.

[0045] That is, in sequence Figure 3 In the cases of "state A", "state B" and "state C" shown in the figure, in "state A", a "first condition" occurs, in which the reduction gradient α of the body speed Vb of the body 2 of the vehicle 1 becomes smaller relative to the reduction gradient of the wheel speed Vw of the wheel 3 of the vehicle 1, and the difference between the wheel speed Vw and the body speed Vb becomes larger. In addition, in "state A", a "second condition" occurs in which the braking force release control T2 corresponding to the rotation stop state of the wheel 3 is executed in the braking device 5.

[0046] Moreover, for example, in the above-mentioned conventional control device, if the occurrence of the "first condition" is set as the first condition and the occurrence of the "second condition" is set as the second condition, then when the first condition and the second condition are satisfied, it is determined that there is an unstable behavior accompanied by rotation around the rotation axis passing through the center of gravity point CG. However, for the second condition to be satisfied, for example, since the driver performs a braking operation on the brake pedal 55, it is necessary to continue the braking force release control T2 for a relatively long time in the decompression mode. Therefore, in the case where the driver's braking operation on the brake pedal 55 is delayed, for example, there is a delay in the determination of the unstable behavior accompanied by rotation in "state A", and after the unstable behavior accompanied by rotation is determined, for example, the switching to the braking force generation control T1 in "state B" and "state C" is also delayed.

[0047] Therefore, the vehicle brake control device 10 of the present embodiment executes Figure 4The braking control program is illustrated by the flow chart of the flow chart, so that the unstable behavior accompanied by rotation can be determined as early as possible before the driver performs a braking operation on the brake pedal 55. The vehicle braking control device 10 (more specifically, the CPU of the computer device constituting the vehicle braking control device 10) starts the execution of the braking control program in step S10.

[0048] In the next step S11, the determination unit 14 of the vehicle brake control device 10 determines whether the vehicle body speed Vb is decreasing at a decreasing gradient α. In other words, the determination unit 14 determines whether the "first situation" has occurred in the vehicle 1. If the determination unit 14 determines "yes" that the vehicle body speed Vb is decreasing at a decreasing gradient α, the vehicle brake control device 10 executes the process of step S12.

[0049] In step S12, the control unit 12 of the vehicle brake control device 10 determines whether the driver has not braked the brake pedal 55 based on the operation signal BO from the brake sensor 118. If the driver has not braked the brake pedal 55 and the control unit 12 determines "yes", the vehicle brake control device 10 executes the process of step S13.

[0050] In step S13, the determination unit 14 determines whether the determination value D (=Gy / μ) is greater than or equal to the prescribed value D0. Therefore, the determination unit 14 obtains the lateral acceleration Gy from the lateral acceleration sensor 115, and obtains the friction coefficient μ of the road surface from the road surface state detection unit 13. Moreover, if the determination value D is greater than the prescribed value D0 and the determination unit 14 determines as "yes", the vehicle brake control device 10 adds 1 to the value of the pre-braking count value Kb in step S14. In addition, if the determination value D is less than the prescribed value D0 and the determination unit 14 determines as "no", the vehicle brake control device 10 sets the value of the pre-braking count value Kb to "0" in step S15. Moreover, the vehicle brake control device 10 performs the processing of step S19 after the processing of the above-mentioned step S14 or the above-mentioned step S15.

[0051] On the other hand, in the above-mentioned step S12, if the driver is performing a braking operation on the brake pedal 55 and the control unit 12 determines "No", the vehicle brake control device 10 performs the process of step S16. In step S16, the determination unit 14 determines whether the braking force release control T2 is being executed by the control unit 12. In other words, the determination unit 14 determines whether the "second situation" has occurred in the vehicle 1.

[0052] If the braking force release control T2 is executed and the determination unit 14 determines "yes", the vehicle brake control device 10 increments the value of the post-braking count value Ka by 1 in step S17. If the braking force release control T2 is not executed and the determination unit 14 determines "no", the vehicle brake control device 10 sets the value of the post-braking count value Ka to "0" in step S18. Moreover, the vehicle brake control device 10 executes the process of step S19 after the process of the above step S17 or the above step S18.

[0053] In step S19 , the vehicle brake control device 10 calculates a total value Kt obtained by adding the post-braking count value Ka to the pre-braking count value Kb. Then, the vehicle brake control device 10 executes the process of step S20 .

[0054] In step S20, the determination unit 14 determines whether the control unit 12 continues the braking force release control T2 and whether the total value Kt is greater than the prescribed value Kt0. That is, in the determination unit 14 of the present embodiment, when the total value Kt after adding the pre-braking count value Kb of the determination value D being greater than the prescribed value D0 in the above step S19 is greater than the prescribed value Kt0, and further, when the "first condition" is generated according to the determination process of the above step S11 and the "second condition" is generated according to the determination process of the above step S16, the unstable behavior accompanied by rotation has occurred in the vehicle 1, and therefore the determination unit 14 determines "yes". Furthermore, when the determination unit 14 outputs the determination information J indicating that the unstable behavior accompanied by rotation has occurred to the instruction unit 15, the vehicle brake control device 10 executes the process of step S21.

[0055] In step S21, the command unit 15 of the vehicle brake control device 10 outputs a brake command C to the control unit 12 based on the determination information J obtained in the above step S20. As a result, the control unit 12 terminates the braking force release control T2, in other words, terminates the anti-skid control, based on the brake command C, and quickly executes the braking force generation control T1, thereby causing the brake device 5 to generate a braking force. In addition, the vehicle brake control device 10 temporarily terminates the execution of the brake control program in step S23, and starts the execution of the program again in step S10 after a predetermined short time has passed.

[0056] If the determination unit 14 determines in step S20 that the vehicle 1 does not have unstable behavior with rotation, the vehicle brake control device 10 temporarily terminates the program execution in step S23 and restarts the program execution in step S10 after a predetermined short time has passed.

[0057] On the other hand, if the vehicle body speed Vb does not decrease at the decreasing gradient α in the above step S11, that is, the "first condition" does not occur and the determination unit 14 determines "No", the vehicle brake control device 10 performs the processing of step S22. In step S22, the vehicle brake control device 10 sets the post-braking count value Ka to "0" and sets the pre-braking count value Kb to "0" in response to the "first condition" not occurring.

[0058] In this case, the total value Kt calculated in the above step S19 is also "0", and in the determination process of the next step S20, the total value Kt becomes less than the prescribed value Kt0, so it is determined to be "No". Therefore, the vehicle brake control device 10 temporarily ends the execution of the program in step S23, and starts the execution of the program again in step S10 after a prescribed short time has passed.

[0059] As can be seen from the above description, the vehicle braking control device 10 comprises: a control unit 12, which can switchably execute a braking force generation control T1 for causing a braking device 5 mounted on the vehicle 1 to generate a braking force, or a braking force release control T2 for releasing the braking force generated by the braking device 5; and a determination unit 14, which determines whether an unstable behavior accompanied by rotation around a rotation axis along a vertical direction (a rotation axis passing through the center of gravity CG of the vehicle 1) has occurred in the vehicle 1 based on a determination value D determined using a lateral acceleration Gy representing a state generated in the vehicle 1 and a friction coefficient μ representing a state of a road surface contacted by the wheels 3 of the vehicle 1, and the control unit 12 executes the braking force generation control T1 based on the determination that an unstable behavior has occurred, thereby causing the braking device 5 to generate a braking force.

[0060] In this case, when, on the basis of the situation where the judgment value D is greater than the prescribed value D0, there is a first situation in which the reduction gradient α of the body speed Vb of the vehicle 1 becomes smaller than the reduction gradient of the wheel speed Vw of the wheel 3 and the body speed Vb is greater than the wheel speed Vw, and a second situation in which the braking device 5 is performing the braking force release control T2 according to the wheel speed Vw, the judgment unit 14 of the vehicle braking control device 10 determines that unstable behavior has occurred.

[0061] In these cases, the vehicle brake control device 10 includes: a sensor group 11 as a state quantity detection unit, which detects a state quantity having a component in the left-right direction of the vehicle 1 and indicating a state occurring in the vehicle 1; and a road surface state detection unit 13 as a physical quantity detection unit, which detects a physical quantity indicating a state between the wheel 3 and the road surface, and a determination unit 14 uses a ratio of the state quantity to the physical quantity as a determination value D. In this case, the state quantity is the lateral acceleration Gy, which is one of the lateral acceleration Gy and the yaw rate YR occurring in the vehicle 1, and the physical quantity is the friction coefficient μ indicating the magnitude of friction of the road surface with which the wheel 3 contacts.

[0062] Furthermore, in these cases, the control unit 12 of the vehicle braking control device 10 executes the braking force generation control T1 and the braking force release control T2 based on the anti-skid control to prevent the wheel 3 from generating a locked state as a rotational stop state. When the determination unit 14 determines that unstable behavior has occurred during the execution of the braking force release control T2 based on the anti-skid control, the anti-skid control is terminated and the braking force generation control T1 is executed.

[0063] According to the above, the determination unit 14 of the vehicle brake control device 10 can determine whether an unstable behavior accompanied by rotation has occurred in the vehicle 1 based on the determination value D. That is, in the vehicle brake control device 10, before braking, that is, before the driver performs a braking operation on the brake pedal 55, the determination unit 14 can determine the occurrence of an unstable behavior accompanied by rotation in the vehicle 1 as early as possible. As a result, the vehicle brake control device 10 can cause the control unit 12 to end the braking force release control T2 when the braking force release control T2 is executed. In other words, the anti-skid control can be ended and the braking force generation control T1 can be quickly executed. As a result, the vehicle brake control device 10 can quickly stop the vehicle 1 that has generated an unstable behavior accompanied by rotation.

[0064] In addition, the determination unit 14 can use the determination value D (=Gy / μ) indicating the ratio of the lateral acceleration Gy to the friction coefficient μ to determine whether an unstable behavior accompanied by rotation has occurred in the vehicle 1. Therefore, the determination unit 14 can ensure robustness, for example, even in the case where the friction coefficient μ is small, it can make a determination. In addition, the determination unit 14 can also determine, for example, whether the vehicle 1 has recovered from the unstable behavior accompanied by rotation to the stable behavior as the determination value D decreases. That is, the vehicle brake control device 10 can ensure room for behavior recovery in the determination of the unstable behavior accompanied by rotation.

[0065] In the modified example, the vehicle brake control device 10 determines whether unstable behavior accompanied by rotation occurs in the vehicle 1 based on the determination value D, regardless of whether the "first condition" and the "second condition" occur in the vehicle 1, in other words, regardless of whether braking is performed.

[0066] In a modified example, the vehicle brake control device 10 executes Figure 5 That is, the vehicle brake control device 10 starts the execution of the program in step S100, and in the next step S101, the determination unit 14 determines whether the determination value D is greater than or equal to the predetermined value D0.

[0067] Furthermore, when the determination value D is greater than or equal to the predetermined value D0 and the determination unit 14 determines "yes", the vehicle brake control device 10 increments the value of the count value K by 1 in step S102. In addition, when the determination value D is less than the predetermined value D0 and the determination unit 14 determines "no", the vehicle brake control device 10 changes the value of the count value K to "0" in step S102. Furthermore, the vehicle brake control device 10 performs the process of step S104 after the process of the above-mentioned step S102 or the above-mentioned step S103.

[0068] In step S104, the determination unit 14 determines whether the count value K is greater than the predetermined value K0. That is, when the count value K is greater than the predetermined value K0, in other words, when the state in which the ratio of the lateral acceleration Gy to the friction coefficient μ is large continues for a certain period of time or more, an unstable behavior accompanied by rotation occurs in the vehicle 1, and therefore the determination unit 14 determines "yes". Furthermore, when the determination unit 14 outputs the determination information J to the instruction unit 15, the vehicle brake control device 10 executes the process of step S105.

[0069] In step S105, the command unit 15 outputs a braking command C to the control unit 12 based on the determination information J. As a result, the control unit 12 executes the braking force generation control T1 based on the braking command C, thereby causing the braking device 5 to generate a braking force. Furthermore, the vehicle brake control device 10 temporarily terminates the execution of the brake control program in step S106, and starts the execution of the program again in step S100 after a prescribed short time has passed. In addition, in the above-mentioned step S104, if the determination unit 14 determines that an unstable behavior accompanied by rotation has not occurred, the vehicle brake control device 10 temporarily terminates the execution of the program in step S106, and starts the execution of the program again in step S100 after a prescribed short time has passed.

[0070] Therefore, in the modified example, regardless of whether braking is performed, for example, even if the driver does not perform a braking operation, the vehicle brake control device 10 can determine whether unstable behavior accompanied by rotation occurs in the vehicle 1. Therefore, in the modified example, the same effects as those of the above-mentioned embodiment can be expected.

[0071] In addition, in the above-described embodiment and modification, the determination unit 14 determines whether the unstable behavior associated with the rotation of the vehicle 1 has occurred based on the determination value D using the friction coefficient μ and the lateral acceleration Gy. However, the yaw rate YR detected by the yaw rate sensor 116 may be used instead of the lateral acceleration Gy. In this case, the determination unit 14 can determine whether the unstable behavior associated with the rotation of the vehicle 1 has occurred using the determination value indicating the ratio of the yaw rate YR to the friction coefficient μ, similarly to the above-described embodiment and modification.

[0072] In addition, the lateral acceleration Gy and the yaw rate YR are state quantities detected along with the rotation (spin) of the vehicle 1. Therefore, it can also be said that the lateral acceleration Gy and the yaw rate YR have a predetermined relationship with the steering angle TA, which is a state quantity that makes the vehicle 1 turn (spin). Therefore, the determination unit 14 can also determine whether an unstable behavior accompanied by a spin has occurred in the vehicle 1 based on the determination value of the lateral acceleration Gy or the yaw rate YR expressed by the relationship between the steering angle TA and the steering angle TA. In this case, the same effects as those of the above-mentioned embodiment and the modified example can be expected.

[0073] Furthermore, in the above-mentioned embodiment, the control unit 12 executes the braking force generation control T1 or the braking force release control T2 according to the ABS control. Alternatively or in addition thereto, the control unit 12 may execute the braking force generation control T1 or the braking force release control T2 according to a well-known vehicle stability control (also referred to as "VSC") for stabilizing the driving behavior of the vehicle 1. In particular, in the above-mentioned modified example, when the determination unit 14 determines that an unstable behavior accompanied by rotation has occurred in the vehicle 1, the control unit 12 can execute the braking force generation control T1 according to the VSC.

[0074] The vehicle brake control device 10 can be said to include the sensor group 11 and the computer. The computer can also be said to be configured to execute the functions (or processes) of the control unit 12 , the road surface state detection unit 13 , the determination unit 14 , and the instruction unit 15 .

Claims

1. A vehicle brake control device, wherein: The vehicle brake control device comprises: a control unit capable of switchably executing a braking force generation control for causing a braking device mounted on the vehicle to generate a braking force, or a braking force release control for releasing the braking force generated by the braking device; and a determination unit that determines whether unstable behavior accompanied by rotation about a rotation axis along a vertical direction occurs in the vehicle based on a determination value determined using a state occurring in the vehicle and a state of a road surface with which wheels of the vehicle are in contact, The control unit causes the brake device to generate the braking force by executing the braking force generation control in response to determining that the unstable behavior has occurred.

2. The vehicle brake control device according to claim 1, wherein: The determination unit determines that the unstable behavior has occurred when, in addition to the case where the determination value is greater than a prescribed value, a first condition and a second condition occur, wherein the first condition is a condition in which a gradient of decrease in the vehicle body speed becomes smaller than a gradient of decrease in the wheel speed of the wheel and the vehicle body speed is greater than the wheel speed, and the second condition is a condition in which the braking device performs braking force release control according to the wheel speed.

3. The vehicle brake control device according to claim 1 or 2, wherein: The vehicle brake control device comprises: a state quantity detecting unit that detects a state quantity having a component in a left-right direction of the vehicle and indicating a state occurring in the vehicle; and a physical quantity detection unit for detecting a physical quantity indicating a state between the wheel and the road surface, The determination unit uses a ratio of the state quantity to the physical quantity as the determination value.

4. The vehicle brake control device according to claim 3, wherein: The state quantity is one of a lateral acceleration and a yaw rate generated by the vehicle, The physical quantity is a friction coefficient indicating the magnitude of friction of the road surface with which the wheel contacts.

5. The vehicle brake control device according to claim 1, wherein: The control unit is composed of: The braking force generation control and the braking force release control are executed according to the anti-skid control for preventing the wheel from stopping rotation. When the determination unit determines that the unstable behavior has occurred during the execution of the braking force release control according to the anti-skid control, the anti-skid control is terminated and the braking force generation control is executed.

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