JP4870725B2 - Brake control device - Google Patents

Description

  The present invention relates to a brake control apparatus that executes control generally referred to as anti-lock brake control (hereinafter referred to as ABS control) that controls brake fluid pressure during braking to prevent wheel lock.

  2. Description of the Related Art Conventionally, a brake control device that executes ABS control calculates a pseudo vehicle speed Vi and calculates and detects a pressure reduction threshold (wheel speed) λ1 that is an optimal slip ratio during braking based on the pseudo vehicle speed Vi. When the wheel speed Vw falls below the depressurization threshold λ1, it is determined that the wheel is in a locked state, and the wheel cylinder pressure is reduced. Thereafter, the wheel speed Vw is restored from the wheel locked state by this reduction, and the wheel speed Vw becomes the pseudo vehicle speed Vi. When the vehicle returns to the vicinity, the pressure is increased again to restore the braking force. Further, at the time of this re-pressure increase, a slow pressure increase control is performed in which a pressure increase pulse is generated at a predetermined time to execute step-by-step pressure increase. It was configured to prevent immediate re-locking.

Further, in obtaining the pseudo vehicle body speed Vi, one formed only by a signal from a wheel speed sensor or one formed based on a signal from a longitudinal acceleration sensor in addition to the wheel speed sensor is known. In terms of cost, it is advantageous to form only by signals from the wheel speed sensor. In the configuration in which the pseudo vehicle speed Vi is formed only by the signal from the wheel speed sensor, it can be considered that the highest speed of the four wheels is close to the vehicle speed at the time of braking. The pseudo vehicle speed Vi is formed by the high value. Therefore, when each wheel tends to lock, it is necessary to reduce the pressure until the wheel speed once returns to the vehicle body speed, and this is performed for all four wheels.
"Automotive Engineering" November 1990, pages 40-41 (Issued Railway Japan)

  However, in the above-described prior art, since the re-pressure increase after the pressure reduction is executed by the slow pressure increase control by the pressure increase pulse of a predetermined time and amount, the wheel speed Vw is equal to the pseudo vehicle speed Vi. There is a problem that it takes time until the wheel speed Vw reaches the vicinity of the pressure-reducing threshold λ1 at which the braking force can be obtained most, resulting in an increase in the braking distance.

  The present invention has been made paying attention to the above-mentioned conventional problems, and in the ABS control, while executing the control to return the wheel speed to the vehicle body speed so that the pseudo vehicle body speed can be formed only by the wheel speed. Another object of the present invention is to shorten the braking distance by shortening the time during which the wheel speed stays at the vehicle speed.

In order to achieve the above-mentioned object, as shown in the claim correspondence diagram of FIG. 1, the present invention provides a brake unit a capable of independently controlling the brake fluid pressure for braking each wheel of the vehicle, and each wheel. A wheel speed sensor b for detecting the wheel speed, a pseudo vehicle speed calculation means c for obtaining a pseudo vehicle speed which is an estimated vehicle speed based on an input from each wheel speed sensor b, and based on the pseudo vehicle speed and the wheel speed. And a control means d for executing ABS control for operating the brake unit a to prevent wheel lock. The control means d is slightly less than the pseudo vehicle speed based on the pseudo vehicle speed. The target wheel speed calculation means e for obtaining a predetermined first target wheel speed that is low or the same as the pseudo vehicle speed and a predetermined second target wheel speed at which the braking force can be exerted, and the wheel speed is the first during ABS control. Target wheel If a higher, switches the target wheel speed to the second target wheel speed, whereas, the target wheel speed switching means f for switching the target wheel speed to the first target wheel speed When the wheel speed is equal to or less than the second target wheel speed, and an abrupt turning state determination means for determining whether or not the abrupt turning state on the basis of the input detecting means for detecting a vehicle behavior, during sharp turns determination, the target wheel speed switching means to the wheel speed of the rear wheel The switching convergence control for converging to the two target wheel speeds to be switched and the single convergence control for converging the wheel speed of the front wheels to the second target wheel speed are performed. Switch convergence control for converging the speed to two target wheel speeds switched by the target wheel speed switching means, and single convergence control for converging the wheel speeds of the three wheels excluding the rear turning inner wheel to the second target wheel speed. , It will converge to each target wheel speed Characterized in that it gives a braking force to each wheel.

  A high braking force can be obtained by executing the single convergence control toward the target wheel speed with the lowest value for the front turning outer wheel with the heaviest wheel load during braking during turning. Further, for the front turning inner wheel and the rear wheel, since the switching convergence control is executed, the wheel speed returns to the vehicle body speed, and the pseudo vehicle body speed can be obtained from these values. By the way, at the time of sudden turning braking, the wheel load of the rear turning inner wheel becomes a very low value, or, in the case of a rear wheel drive vehicle, the engine brake acts on the rear wheel. Although there is a possibility that the speed does not return to the vehicle body speed, the execution target wheel of the switching convergence control includes the front turning inner wheel, so that the vehicle speed can be surely returned to the vehicle speed, and thus the high pseudo vehicle speed is detected. Accuracy can be ensured.

Further, as described in claim 2, before Symbol control unit d has a turning state determining means for determining whether the abrupt turning state during turning in accordance with an input of a detection means for detecting a vehicle behavior, At the time of turning, when the sudden turn is judged, the single convergence control is executed for the front two wheels, while the switching convergence control is executed for the rear two wheels. While the single convergence control is performed on the rear turning inner wheel, the switching convergence control may be performed on the rear turning inner wheel.

  During turning, during non-rapid turning, only the rear turning inner wheel is switched and convergence control is performed to form a wheel speed that can be used to determine the pseudo vehicle speed, and for the other three wheels, toward a lower target wheel speed. A high braking force can be obtained by executing the single convergence control. Further, during a sudden turn, the wheel load of the rear turning inner wheel may become extremely small and may not return to the vehicle speed, so that it can be used to obtain the pseudo vehicle speed by executing the switching convergence control for the two rear wheels. A wheel speed is formed, and a single braking control is executed on the front two wheels to obtain a high braking force.

As described above, the invention according to claim 1 is configured to execute the single convergence control on the outer front turning wheel while turning, and execute the switching convergence control on the other wheels. For the front turning outer wheel with the heaviest wheel load, high braking force can be obtained by executing the single convergence control toward the lowest target wheel speed, and the front turning inner wheel and rear wheel By executing the switching convergence control, even if the rear wheel does not return to the vehicle speed due to sudden braking, the pseudo vehicle speed can be obtained from the wheel speed of the front turning inner wheel. The effect that accuracy can be secured is obtained.

According to the second aspect of the present invention, when turning, when determining a sudden turn, the single convergence control is executed for the front two wheels, while the switching convergence control is executed for the rear two wheels, At the time of turning determination, the single convergence control is executed for the three wheels excluding the rear turning inner wheel, while the switching convergence control is executed for the rear turning inner wheel. While it is possible to obtain the vehicle speed, high braking force can be obtained by executing single convergence control for the other three wheels, and the wheel load of the rear turning inner wheel becomes extremely small during a sudden turn. Since there is a possibility that the vehicle speed will not return to the vehicle speed, the switching convergence control is executed for the rear two wheels to form a wheel speed that can be used to obtain the pseudo vehicle speed, and for the front two wheels. Effect that it is possible to obtain a high braking force by executing the convergence control is obtained.

  Hereinafter, the best mode for realizing a brake control device of the present invention will be described based on an embodiment shown in the drawings.

First, the configuration will be described.
Example 1
FIG. 2 is a configuration diagram showing a main part of the brake device of the embodiment, in which 1 is a master cylinder. The master cylinder 1 is configured to generate hydraulic pressure when the driver operates a brake pedal (not shown).

  The master cylinder 1 is connected to a wheel cylinder 3 via a brake circuit 2. Further, in the middle of the brake circuit 2, an increased pressure state in which the brake fluid pressure of the wheel cylinder 3 can be increased by communicating the upstream (master cylinder 1 side) and the downstream (wheel cylinder 3 side) of the brake circuit 2 ( Actually, not only the pressure is increased but also the pressure is reduced when the master cylinder pressure is lowered), the brake fluid in the wheel cylinder 3 is released to the drain circuit 4 to reduce the wheel cylinder pressure, and the brake circuit A switching valve 5 is provided that can be switched to a holding state in which 2 is cut off and the brake fluid pressure of the wheel cylinder 3 is held. Therefore, the hydraulic pressure of the wheel cylinder 2 can be arbitrarily increased or decreased based on the switching of the switching valve 5.

  The drain circuit 4 is provided with a reservoir 6 capable of storing brake fluid. A pump 7 is provided for returning the brake fluid stored in the reservoir 6 to a position upstream of the switching valve 5 of the brake circuit 2.

  The configuration in the range surrounded by the one-dot chain line in FIG. 2 described above is combined into one as the brake unit 11. 2 illustrates the configuration of one wheel, the overall configuration is as shown in FIG. 3, and the brake unit 11 includes four wheel cylinders 3 (FIG. 3) of four wheels FR, FL, RR, RL. The brake fluid pressure of (not shown in FIG. 1) can be arbitrarily controlled.

  The operation of the switching valve 5 and the pump 7 in the brake unit 11 is controlled by the control unit 12. The control unit 12 includes wheel speed sensors 13, 13, 13, and 13 that detect the rotational speeds of the wheels FR, FL, RR, and RL as input means, and execute ABS control for preventing wheel lock during braking. .

Next, ABS control according to the first embodiment will be described.
4 to 6 are flowcharts showing the flow of ABS control according to the first embodiment. First, predetermined initialization is executed in step 101 of FIG. 4, and then signals are read from the respective wheel speed sensors 13 in step 102. The wheel speed Vw is calculated for each wheel.

  In step 103, the pseudo vehicle speed Vi is calculated from the wheel speed Vw of the two rear wheels. Details of this will be described later with reference to FIG. Subsequently, in step 104, two target wheel speeds MVw, that is, a first target wheel speed MVw1 and a second target wheel speed MVw2, are calculated. The first target wheel speed MVw1 is a value close to the pseudo vehicle speed Vi (this is referred to as a shallow value), while the second target wheel speed MVw2 is a value corresponding to the conventional pressure reduction threshold λ1 (this is referred to as a deep value). The details will be described later with reference to FIG.

In step 105, based on the target wheel speeds MVw1 and MVw2, the pressure increase / decrease pulse T corresponding to the target wheel speeds MVw1 and MVw2 is calculated and output. In the first embodiment, the increasing / decreasing pulse T is obtained based on so-called PID (convergence) control. First, a difference dVw between the wheel speed Vw and the target wheel speed MVw is obtained, and based on the difference dVw, T = K11 × dVw + K12 × integral (dVw) + K13 × differentiation (dVw). K11, K12, and K13 are gains.
In step 106, it is determined whether or not 10 ms has elapsed. That is, in the present embodiment, the above flow is executed every time 10 ms elapses.

Next, how to obtain the pseudo vehicle speed Vi in step 103 will be described based on the flowchart of FIG.
In step 1001, it is determined whether or not ABS control is being executed based on whether or not the ABS flag AS has been set (= 1) in the previous time (10 ms before). The highest wheel speed Vw is selected from the two wheel speeds Vw (select high). The selected wheel speed Vfs is set as the pseudo vehicle speed Vi. Note that the selected wheel speed Vfs may be other values such as the second value from the higher one instead of the select high (the highest value).

  On the other hand, if the ABS control is being performed in step 1001, the process proceeds to step 1003 to determine whether or not the non-ABS control is performed two times before (20 ms before), and proceeds to step 1004 when YES, that is, when ABS control is started, The pseudo vehicle speed Vi is set to the reference speed V0, and the timer is reset.

  In step 1005, a timer is counted for each control cycle, and in the subsequent step 1006, branch determination between the pseudo vehicle speed Vi and the selected wheel speed Vfs is performed based on whether FVP = 1 or not. Proceeding to step 1007, the pseudo vehicle speed Vi at that time is set as the branching speed Vp.

  Next, in steps 1008 to 1010, a pseudo vehicle body acceleration / deceleration Vid is formed. First, in step 1008, whether or not FCYCLE = 0 is set in the first or second cycle of the ABS control. Since the deceleration is not understood in the first cycle, the process proceeds to step 1010 and the pseudo vehicle acceleration / deceleration Vid is set based on the value Vidp assuming the maximum acceleration / deceleration of the vehicle when the road surface μ is large. . On the other hand, in the second and subsequent cycles, the process proceeds to step 1009, and the deceleration Vid per control cycle is determined using the values of the reference speed V0, branch speed Vp, and count timer T0 obtained in steps 1004, 1005, and 1007. Set.

In the subsequent step 1011, the pseudo vehicle speed Vi is determined based on the pseudo vehicle speed Vi (10 ms before) and the pseudo vehicle acceleration / deceleration Vid.
Further, in step 1012, the magnitude relation between the pseudo vehicle speed Vi and the selected wheel speed Vfs is determined. If the selected wheel speed Vfs is larger, the process proceeds to step 1013 to select the selected wheel speed Vfs as the pseudo vehicle body speed. Speed Vi.

  As described above, the pseudo vehicle body speed Vi is formed from the selected wheel speed Vfs when the ABS control is not executed, and the first cycle is estimated based on the preset deceleration Vidp during sudden deceleration during the ABS control. In the second and subsequent cycles, the estimation is based on the actual deceleration state based on the count value T0 of the timer. If the selected wheel speed Vfs is larger than this estimated value, the selected wheel speed Vfs is used. Form.

Next, how to obtain the target wheel speeds MVw1 and MVw2 in step 104 will be described based on the flowchart of FIG.
In step 201, the first target wheel speed MVw1 and the second target wheel speed MVw2 are calculated by multiplying the pseudo vehicle body speed Vi by the coefficients K1 and K2, respectively.
That is, MVw1 = K1 × Vi and MVw2 = K2 × Vi.

  In step 202, it is determined whether or not the control wheel is a front wheel. If the control wheel is a front wheel, the process proceeds to step 203 to set the target wheel (front wheel) target wheel speed MVw as the second target wheel speed MVw2.

  On the other hand, in the case of the rear wheel, the routine proceeds from step 202 to step 204, where the wheel speed Vw (10 ms before) in the previous control cycle is greater than the previous second target wheel speed MVw2 (10 ms before) and this time Whether or not the vehicle wheel speed Vw is equal to or lower than the second target wheel speed MVw2 of this time, that is, whether or not there is a strong tendency to lock across the second target wheel speed MVw2 where the wheel speed Vw is a deep value. If YES, the routine proceeds to step 205, where the target wheel speed MVw of the target wheel (rear wheel) is set as the first target wheel speed MVw1.

  In step 206, the wheel speed Vw (10 ms before) in the previous control cycle is less than the previous first target wheel speed MVw1 (10 ms before), and the current wheel speed Vw is the current first target wheel speed. It is determined whether or not it is equal to or higher than MVw1, that is, whether or not the wheel speed Vw is approaching the pseudo vehicle speed Vi across the first target wheel speed MVw1 having a shallow value. Then, the target wheel speed MVw of the target wheel (rear wheel) is set as the second target wheel speed MVw2, and in the case of NO, the process proceeds to step 208 to set the target wheel speed MVw as the previous value MVw (10 ms before).

Next, the operation of the first embodiment will be described with reference to FIGS.
As shown in FIG. 7, in the first embodiment, the pseudo vehicle body speed Vi is obtained based on the wheel speed Vw of the rear wheel, and further, the first target that is slightly lower (shallow) than the pseudo vehicle body speed Vi. A wheel speed MVw1 and a first target wheel speed NVw2 that is a lower (deeper) value than the first target wheel speed MVw1 are obtained.

For the front wheels, as shown in FIG. 7A, based on PID control, control is performed to converge the wheel speed Vw toward the second target wheel speed MVw2, which is the most preferable slip ratio during braking. .
On the other hand, for the rear wheels, as shown in FIG. 7 (b), if the wheel speed Vw crosses lower than the second target wheel speed MVw2, the first target wheel speed MVw is a shallow value. Convergence control is performed toward this value as the wheel speed MVw1, and if the wheel speed Vw crosses higher than the first target wheel speed MVw1, the second target wheel speed MVw2 is a deep value of the target wheel speed MVw. Then, the control of performing the convergence control toward this value is repeated.

  Therefore, in the past, as shown in FIG. 8A, all four wheels once returned to the pseudo vehicle speed Vi, and the pseudo vehicle speed Vi was created based on these maximum values. In Example 1, as shown in FIG. 4B, only the wheel speed Vw of the two rear wheels returns to the pseudo vehicle speed Vi, and the pseudo vehicle speed Vi is set based on the maximum value of the wheel speed Vw of these rear wheels. For the front wheel, control is performed to converge the front wheel to the second target wheel speed MVw2, which is a deep target value. Thus, the wheel speed Vw of the front wheel with a heavy wheel load does not return to the pseudo vehicle body speed Vi, and is maintained in the vicinity of the slip ratio at which the braking force can be obtained efficiently, so that a high braking force is exhibited. The braking distance can be shortened.

  As described above, in the first embodiment, when the pseudo vehicle body speed Vi is formed, the front wheel is converged to the deep second target wheel speed MVw while being an inexpensive configuration that does not use the longitudinal acceleration sensor. There is an effect that the power can be obtained and the braking distance can be shortened.

  For the rear wheels, when pressure is reduced, convergence control (PID control) is performed toward the second target wheel speed MVw2, and when pressure is increased, convergence control (PID control) is performed toward the first target wheel speed MVw1. As a result, the pressure can be increased in a short time compared to the conventional method in which the pressure is slowly increased with a pulse determined at the time of pressure increase. In this respect, the braking distance can be shortened. The effect of being able to be obtained.

  In the first embodiment, the convergence control is also performed for the rear wheels. However, even if the conventional slow pressure increase is performed for the rear wheels, the effect of shortening the intended braking distance is not achieved. Obtainable.

(Example 2)
Next, a brake control device of Embodiment 2 will be described. The second embodiment is a modification of the first embodiment, and the basic configuration is the same as that of the first embodiment. Therefore, the description thereof is omitted, and the control flow is only different from the first embodiment. Will be explained.

  In the second embodiment, details of calculating the target wheel speed MVw in step 104 of the first embodiment are different from those in the first embodiment. This will be described with reference to the flowchart of FIG. 9. In step 301, the pseudo vehicle body speed Vi is multiplied by the gains K21, K22, and K23, respectively, and the first target wheel speed MVw1, the second target wheel speed MVw2, and the third target wheel speed MVw3. Is calculated. Incidentally, as shown in FIG. 10, the target wheel speeds MVw1 to MVw1 to MVw1 to MVw3 are set in order of MVw1, MVw3, MVw2, and the gains K21 <K23 <K22 are set so as to gradually become deep values with respect to the pseudo vehicle speed Vi. In the case of the second embodiment, the second target wheel speed Mvw2 is a wheel speed (slip rate) at which the highest braking force can be exhibited during braking.

In step 302, it is determined whether or not the target wheel is a front wheel. If the target wheel is a front wheel (YES), the process proceeds to step 303 to set the target wheel speed MVw as the second target wheel speed Mvw2.
On the other hand, if NO in step 302, that is, if the target wheel is a rear wheel, the process proceeds to step 304, and the wheel speed Vw is higher than the third target wheel speed Mvw3 as in step 204 of the first embodiment. It is determined whether or not the vehicle has crossed from the high side to the low side. If the vehicle has crossed in this way, the process proceeds to step 305 to set the target wheel speed MVw as the first target wheel speed MVw1, while in step 304, the third target wheel speed. If it does not cross Mvw3, the routine proceeds to step 306, where it is determined whether or not the wheel speed Vw has crossed from the higher side to the lower side with respect to the first target wheel speed MVw1, and if so, the step Proceeding to 307, the target wheel speed MVw is switched to the third target wheel speed Mvw3. If the target wheel speed MVw is not crossed, the previous target wheel speed MVw is held as the target wheel speed MVw. That.

Next, the operation of the second embodiment will be described with reference to the time chart of FIG.
In the second embodiment, first to third target wheel speeds MVw are created as shown in the figure, and the front wheels are controlled to converge to the second target wheel speed Mvw2 that is set most deeply.
On the other hand, the rear wheel performs convergence control toward each target wheel speed MVw while switching between the first target wheel speed MVw1 and the third target wheel speed Mvw3.

Therefore, the rear wheel can periodically approach the vehicle body speed to obtain the pseudo vehicle speed Vi with high accuracy based on the wheel speed Vw of the rear wheel, and the target wheel speed MVw is reduced for the rear wheel. Therefore, the detection accuracy of the pseudo vehicle speed Vi is higher.
Since the front wheels are converged to the second target wheel speed Mvw2 that is set deeply as in the first embodiment, a high braking force can be obtained and the braking distance can be shortened.

(Example 3)
Next, a brake control device of Embodiment 3 will be described. The third embodiment is a modification of the first embodiment, and as a difference, the control unit 12 includes a steering angle sensor, a yaw rate sensor, and a lateral acceleration sensor as input means, although illustration is omitted. ing.

Next, the control flow of the third embodiment will be described with reference to FIG.
Steps 101 to 105 are the same as those in the first embodiment.
In step 402 following step 104, output values of a steering angle sensor, a yaw rate sensor, and a lateral acceleration sensor (not shown) are taken in, and in subsequent step 402, it is determined whether the vehicle is turning or going straight. That is, it is determined that the vehicle is turning when the steering angle is greater than a preset steering angle threshold and the lateral acceleration is greater than a preset lateral acceleration threshold. When the lateral acceleration is smaller than a preset negative lateral acceleration threshold value and the lateral acceleration is smaller than a preset negative lateral acceleration threshold value, it is determined that the vehicle is turning. .

When it is determined in step 402 that the vehicle is traveling straight, a second control target determination process described later is executed in step 403. On the other hand, when it is determined in step 402 that the vehicle is turning, the process proceeds to step 404 where calculation for estimating each wheel load is performed, and the process further proceeds to step 405 to execute a turning state determination. This turning state determination is based on the wheel load obtained in step 404 to determine whether the turning state is a gentle turning state in which the wheel load of the rear inner ring is sufficiently obtained, or whether the turning state is a sudden turning state in which the wheel load of the rear inner ring is very small. When the vehicle is turning slowly, the process proceeds to step 406 to perform a first control target determination process, and to step 403 during a sudden turn.
Based on each target wheel speed MVw determined in step 403 or 406, in step 105, the pressure increase / decrease pulse T is determined.

Next, the first control target determination process executed in step 406 will be described first.
FIG. 12 is a flowchart showing a first control target determination process executed during a gentle turn. In step 4061, it is determined whether or not the target wheel is a rear inner wheel. The wheel speed MVw is set to a second target wheel speed MVw2, which is a deep value.
In the case of the rear inner wheel, the routine proceeds to step 4062, where it is determined whether or not the wheel speed Vw has crossed from the top to the bottom with respect to the second target wheel speed MVw2. If YES, the target wheel speed MVw is shallow. The value is set to the first target wheel speed MVw1.

  On the other hand, if NO is determined in step 4062, the process proceeds to step 4064 to determine whether or not the wheel speed Vw has crossed from the bottom to the first target wheel speed MVw1, and in the case of YES, Proceeding to step 4065, the target wheel speed MVw is set to the second target wheel speed MVw2 which is a deep value. If NO is determined in step 4064, the process proceeds to step 4066, and the previous value MVw (10 ms before) is held as the target wheel speed MVw.

  That is, at the time of slow turning, as shown in FIG. 13 (a), the target wheel speed MVw is set to the second target wheel speed MVw2 which is a deep value for the three wheels other than the rear inner wheel indicated by the oblique lines, Each time the wheel speed Vw crosses each target wheel speed MVw1, MVw2, the target wheel speed is switched to the far side.

Next, the second control target determination process in step 403 performed during a sudden turn will be described based on the flowchart of FIG.
In Step 4031, it is determined whether or not the target wheel is a front wheel. If the target wheel is a front wheel, the process proceeds to Step 4032 to set the target wheel speed MVw to the second target wheel speed MVw2.
On the other hand, if the target wheel is a rear wheel, the routine proceeds to step 4033, where it is determined whether or not the wheel speed Vw has crossed from the top to the bottom with respect to the second target wheel speed MVw2. Advances to step 4034 to set the target wheel speed MVw to the first target wheel speed MVw1. If NO in step 4033, the process proceeds to step 4035, where it is determined whether or not the wheel speed Vw has crossed from the bottom to the first target wheel speed MVw1. In this case, the routine proceeds to step 4036, where the target wheel speed MVw is set to the second target wheel speed MVw2, and if it does not cross, the routine proceeds to step 4037, where the target wheel speed MVw is held at the previous value.

  That is, at the time of a sudden turn, as shown in FIG. 13 (b), the target wheel speed MVw is set to a deep value of the second target wheel speed MVw2 for the front wheels indicated by diagonal lines, and the wheel speed Vw is set for the rear wheels. Each time the target wheel speeds MVw1 and MVw2 are crossed, the target wheel speed is switched alternately to the far side target wheel speed.

In the third embodiment described above, during straight traveling and sudden turning, the front wheel is set to the second target wheel speed MVw2, which is a deep value, and converged by PID control toward this value. On the other hand, for the rear wheels, as in the first and second embodiments, the target wheel speed MVw is switched between the shallow first target wheel speed MVw1 and the deep second target wheel speed MVw2 while switching the PID. It is possible to obtain a high braking force while reducing the wheel speed Vw until the pseudo vehicle speed Vi can be accurately obtained by performing the control F.
Further, at the time of slow turning, only the rear wheels in the turn correspond to the pseudo vehicle speed Vi, and the remaining three wheels are converged by the PID control toward the deep second target wheel speed MVw2, so that a higher braking force is obtained. Can do. In addition, since the vehicle is turning slowly, the rear wheel in the turn has a sufficient wheel load and a value corresponding to the vehicle speed.

Example 4
The fourth embodiment is a modification of the third embodiment, and the processing after determining that the vehicle is turning in step 402 of the third embodiment is different. That is, the fourth embodiment is an example in which the target wheel speed MVw of the outer front turning wheel is deeply formed during turning.

This will be described with reference to the flowchart of FIG. 15. In step 501, it is determined whether or not the target wheel is a front turning outer wheel. If the target wheel is a front turning outer wheel, the process proceeds to step 502 and the target wheel speed MVw is set to the second target wheel speed MVw. Set to wheel speed MVw2.
On the other hand, if the target wheel is a front turning outer wheel, the process proceeds to step 503, where it is determined whether or not the wheel speed Vw has crossed from the top to the bottom with respect to the second target wheel speed MVw2. In step 504, the target wheel speed MVw is set to the first target wheel speed MVw1. If NO is determined in step 503, the process proceeds to step 505, in which it is determined whether or not the wheel speed Vw has crossed from the bottom to the first target wheel speed MVw1, and thus crossed in this way. In this case, the process proceeds to step 506, where the target wheel speed MVw is set to the second target wheel speed MVw2, and if not crossed, the process proceeds to step 507 to hold the target wheel speed MVw at the previous value. .

  That is, at the time of a sudden turn, as shown in FIG. 16, the target wheel speed MVw is set to a deep value of the second target wheel speed MVw2 for the front turning outer wheel indicated by the oblique lines, and toward the second target wheel speed MVw2. Converge by PID control. FIG. 17A shows the change in wheel speed Vw and the change in wheel cylinder pressure at this time. On the other hand, for the other three wheels, each time the wheel speed Vw crosses each target wheel speed MVw1, MVw2, the target wheel speed is switched alternately to the far side, and alternately toward the two target wheel speeds MVw1, MVw2. Converge. FIG. 17B shows the change in wheel speed Vw and the change in wheel cylinder pressure at this time.

  As described above, in the fourth embodiment, a high braking force can be obtained by setting the target wheel speed MVw of the front turning outer wheel with the largest wheel load deeply. Also, during a sudden turn, the wheel speed of the rear turning inner wheel may not return to the vehicle body speed even if the pressure is reduced due to the movement of the wheel load. Accordingly, the wheel speed may not return to the vehicle body speed, but the pseudo vehicle body speed Vi is calculated by the three wheels including the front turning inner wheel that is not affected by these. Accuracy can be improved.

  When the vehicle is traveling straight and slowly turning, the target wheel speed MVw of the two front wheels is set deep, while the target wheel speed MVw of the two rear wheels is alternately switched to the target wheel speeds MVw1 and MVw2.

It is a claim corresponding figure which shows the brake control apparatus of this invention. 1 is a configuration diagram illustrating a main part of Example 1. FIG. 1 is an overall view showing a brake control device of Embodiment 1. FIG. 3 is a flowchart of ABS control according to the first embodiment. 6 is a flowchart for obtaining a pseudo vehicle body speed according to the first embodiment. 3 is a flowchart for obtaining a target wheel speed according to the first embodiment. 3 is a time chart showing an operation example of the first embodiment. It is comparison explanatory drawing of a prior art and Example 1. FIG. It is a flowchart which calculates | requires the target wheel speed of Example 2. FIG. 6 is a time chart illustrating an operation example of the second embodiment. 10 is a flowchart of ABS control according to the third embodiment. 6 is a flowchart for obtaining a target wheel speed during a gentle turn according to a third embodiment. FIG. 10 is an operation explanatory diagram of Embodiment 3. It is a flowchart which calculates | requires the target wheel speed at the time of the sudden turn of Example 3. FIG. It is a flowchart which calculates | requires the target wheel speed at the time of turning of Example 4. FIG. FIG. 10 is an operation explanatory diagram of Embodiment 4. 6 is a time chart showing an operation example of Example 4.

Explanation of symbols

1 Master cylinder 2 Brake circuit 3 Wheel cylinder 4 Drain circuit 5 Switching valve 6 Reservoir 7 Pump 11 Brake unit 12 Control unit 13 Wheel speed sensor

Claims (2)

A brake unit capable of independently controlling the brake fluid pressure for braking each wheel of the vehicle;
A wheel speed sensor for detecting the wheel speed of each wheel;
A pseudo vehicle speed calculation means for obtaining a pseudo vehicle speed that is an estimated vehicle speed based on an input from each wheel speed sensor;
Control means for executing ABS control for operating a brake unit to prevent wheel lock based on the pseudo vehicle body speed and the wheel speed;
In a brake control device comprising:
The control means includes
Based on the pseudo vehicle speed, a predetermined first target wheel speed that is slightly lower than or equal to the pseudo vehicle speed, and a second target wheel speed that is set lower than the first target wheel speed; Target wheel speed calculating means for obtaining
During the ABS control, when the wheel speed becomes equal to or higher than the first target wheel speed, the target wheel speed is switched to the second target wheel speed. On the other hand, when the wheel speed becomes equal to or lower than the second target wheel speed, the target wheel speed is changed to the first target wheel speed. Target wheel speed switching means for switching to wheel speed;
A sudden turn state determination unit that determines whether or not the vehicle is in a sudden turn state based on an input of a detection unit that detects a vehicle behavior ;
A switching convergence control for converging the wheel speed of the rear wheel to two target wheel speeds to be switched by the target wheel speed switching means, and a single convergence control for converging the wheel speed of the front wheel to the second target wheel speed when making a sudden turn determination; In addition, when it is determined that the vehicle is not turning suddenly, the switching convergence control for converging the wheel speed of the rear turning inner wheel to two target wheel speeds switched by the target wheel speed switching means, and the wheel speeds of the three wheels excluding the rear turning inner wheel are determined. And a single convergence control for converging to a second target wheel speed, and applying a braking force to each wheel so as to converge to each target wheel speed. A brake unit capable of independently controlling the brake fluid pressure for braking each wheel of the vehicle;
A wheel speed sensor for detecting the wheel speed of each wheel;
A pseudo vehicle speed calculation means for obtaining a pseudo vehicle speed that is an estimated vehicle speed based on an input from each wheel speed sensor;
Control means for executing ABS control for operating a brake unit to prevent wheel lock based on the pseudo vehicle body speed and the wheel speed;
In a brake control device comprising:
The control means includes
Based on the pseudo vehicle speed, a predetermined first target wheel speed that is slightly lower than or equal to the pseudo vehicle speed, and a second target wheel speed that is set lower than the first target wheel speed; A target wheel speed calculating means for obtaining a third target wheel speed which is a value between the first target wheel speed and the second target wheel speed;
During the ABS control, when the wheel speed becomes equal to or higher than the first target wheel speed, the target wheel speed is switched to the third target wheel speed. On the other hand, when the wheel speed becomes equal to or lower than the third target wheel speed, the target wheel speed is changed to the first target wheel speed. Target wheel speed switching means for switching to wheel speed;
A sudden turn state determination unit that determines whether or not the vehicle is in a sudden turn state based on an input of a detection unit that detects a vehicle behavior ;
At the time of turning, when turning suddenly, switching convergence control for converging the wheel speed of the rear wheel to two target wheel speeds switched by the target wheel speed switching means, and single for converging the wheel speed of the front wheel to the second target wheel speed. Convergence control is performed, and when determining non-rapid turning, switching convergence control for converging the wheel speed of the rear turning inner wheel to two target wheel speeds switched by the target wheel speed switching means, and three wheels excluding the rear turning inner wheel And a single convergence control for converging the wheel speed to the second target wheel speed, and applying a braking force to each wheel so as to converge to each target wheel speed.

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