JP2012171404A - Anti-skid control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform further optimal ABS control in response to a change in loading weight.SOLUTION: In a yaw control during ABS control performed to a front high μ wheel, a pressure threshold Phold is made variable in response to estimated loading weight, and holding control and pressure reducing-increasing control are selected based on the pressure threshold Phold set in response to the estimated loading weight. With such a constitution, the optimal ABS control in response to the estimated loading weight can be further finely performed.

Description

  The present invention relates to an ABS control device that performs anti-skid control (hereinafter referred to as ABS control) that prevents a wheel from locking during braking.

  Conventionally, in Patent Document 1, spin generation can be suppressed by performing select low control on a μ split road surface in which the friction coefficient of the road surface of the vehicle (hereinafter referred to as road surface μ or μ) differs between the left and right wheels. An ABS control apparatus configured as described above is disclosed. Select low control means that when ABS control is started for a wheel with a low road surface μ (hereinafter referred to as a low μ road), a wheel with a high road surface μ (hereinafter referred to as a high μ road) is subjected to ABS control. Regardless of whether or not the start condition is satisfied, the low μ side wheel and the high μ side wheel also start the pressure reduction control in the ABS control.

  In the ABS control device disclosed in Patent Document 1, when the slip difference between the left and right sides is large on the μ split road surface, the wheel on the high μ road side and the wheel on the low μ road side (hereinafter referred to as the front high μ wheel respectively). The hydraulic pressure difference of the wheel cylinder (hereinafter referred to as W / C) of the front low-μ wheel is also kept within a certain range to ensure stability and braking performance.

JP 2009-96211 A

  However, in the ABS control device of Patent Document 1, the W / C pressure difference between the front high μ wheel and the front low μ wheel is uniformly suppressed within a certain range. Sometimes there is a lack of braking performance. In other words, it is preferable to improve the vehicle stability when the load weight is small compared to the case where the load weight is large, so it is preferable to improve the vehicle stability. When the load weight is large, the load weight is small Since the vehicle stability is higher than that of the vehicle, it is preferable to increase the braking performance. However, in the case of uniform control content, if the control content is adjusted to the one with a smaller load weight, the braking performance is insufficient when the load weight is large, and if the control content is adjusted to the one with a larger load weight, the load weight is reduced. If it is small, there is a possibility of poor stability. For this reason, it is desired to perform more optimal ABS control.

  In view of the above points, an object of the present invention is to provide an ABS control device capable of performing more optimal ABS control corresponding to a change in load weight.

  In order to achieve the above object, according to the first aspect of the present invention, the estimated W / C pressure calculating means (115) for calculating the estimated W / C pressure of each of the left and right front wheels, and the road surface during travel of the vehicle are μ split road surfaces. And a μ split determination means (120) for determining whether the road surface on the left or right is a high μ road side or a low μ road side, and a load weight estimation means (130) for estimating the load weight on the vehicle. ), Pressure threshold value setting means (510, 620) for setting the pressure threshold value (Phold, Hold1, Hold2) corresponding to the load weight so as to increase as the load weight increases, and the μ split by the μ split determination means It is determined that the road surface is a high μ road side and a low μ road side, and anti-skid control is started on the μ split road surface. When the mode is set and the pressure is increased, the anti-skid control pressure reduction mode is not set for the wheels on the low μ road side of the left and right front wheels, and the difference in estimated W / C pressure between the left and right front wheels is If the pressure threshold value is less than the pressure threshold value set by the pressure threshold value setting means, the energization amount to the solenoid of the pressure increase control linear valve (17, 37) for controlling the increase in the W / C pressure on the high μ road side is controlled. Therefore, it is characterized by having energization amount control means (540 to 560, 640 to 660) for making the pressure increasing gradient lower than the pressure increasing gradient when the pressure increasing control linear valve is in the communication state. .

  Thus, the pressure threshold is set according to the vehicle weight. Then, anti-skid control is started on the μ split road surface, and after the wheels on the high μ road side of the left and right front wheels are depressurized by setting the pressure reducing mode, the pressure increasing mode is set and the pressure is increased. If the anti-skid control pressure reduction mode is not set for the wheel on the low μ road side and the difference in estimated W / C pressure between the left and right front wheels is less than the pressure threshold, the W / C pressure on the high μ road side The pressure is gradually increased. As a result, W / W generated on the wheel on the high μ road side according to the loaded weight, while performing the control during the control so that the braking force of the wheel on the high μ road side is not increased excessively and the stability of the vehicle is not deteriorated. It is also possible to improve the braking performance by changing the C pressure. This makes it possible to achieve both vehicle stability and braking performance in accordance with the loaded weight, and to perform more optimal ABS control corresponding to changes in the loaded weight.

  In this case, as described in claim 2, the energization amount control means increases the pressure by setting the pressure increasing mode after the wheels on the high μ road side of the left and right front wheels are depressurized by setting the pressure reducing mode. Sometimes, when the anti-skid control pressure reduction mode is not set to the low μ road side wheel of the left and right front wheels, and the difference between the estimated W / C pressures of the left and right front wheels exceeds the pressure threshold, the high μ road side wheel The W / C pressure of the wheel on the high μ road side can be maintained by controlling the energization amount to the solenoid of the pressure increase control linear valve that controls the pressure increase of the W / C pressure. Thus, by maintaining the W / C pressure of the wheels on the high μ road side, the difference in the W / C pressure between the left and right front wheels can be prevented from becoming too large. This can prevent the vehicle from becoming unstable.

  In the invention according to claim 3, when the load weight estimated by the load weight estimating means is less than the first weight threshold (Load1), the pressure threshold setting means sets the pressure threshold to the first pressure threshold (Pold1). When the load weight estimated by the load weight estimation means is not less than the first weight threshold value and less than the second weight threshold value (Load2) larger than the first weight threshold value, the pressure threshold value setting means sets the pressure threshold value to the first pressure threshold value. The second pressure threshold value (Pold2) is set to be larger than the second pressure threshold value (Pold2).

  Thus, according to the load weight, when the load weight is less than the first weight threshold, the pressure threshold is set to the first pressure threshold, and when the load weight is not less than the first weight threshold and less than the second weight threshold, the pressure threshold is set. The second pressure threshold can be set.

  Of course, the pressure threshold corresponding to the load weight is calculated based on a map or function formula showing the relationship between the load weight and the pressure threshold so that the pressure threshold (Pold) gradually increases as the load weight increases. You may make it do.

  In the invention according to claim 4, when the load weight estimated by the load weight estimation means is equal to or greater than the second weight threshold (Load 2), the energization amount control means lowers the wheel on the high μ road side among the left and right front wheels. The ABS control is performed independently of the wheel on the μ road side.

  As described above, when the loaded weight is equal to or greater than the second weight threshold, independent control is performed on the wheels on the high μ road side among the left and right front wheels. For this reason, when the loaded weight is large, it is possible to obtain a larger braking force by further increasing the W / C pressure of the wheels on the high μ road side among the left and right front wheels. Therefore, the braking performance can be further improved.

  Similarly, as described in claim 5, when the load weight estimated by the load weight estimation means is equal to or greater than a predetermined weight threshold (Load), the energization amount control means includes the left and right front wheels on the high μ road side. For the wheels, ABS control may be performed independently of the wheels on the low μ road side. Thereby, the same effect as that of claim 4 can be obtained.

  The invention according to claim 6 is characterized in that the energization amount control means makes the pressure increase gradient at the time of slow pressure increase variable according to the load weight estimated by the load weight estimation means. If it does in this way, it can be set as the pressure increase gradient according to loading weight, and can balance the stability and braking nature of vehicles according to loading weight more.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

1 shows a block configuration of each function of a brake control device 1 that realizes an ABS control device according to a first embodiment of the present invention. It is the figure which showed the detailed structure of each part which comprises the brake control apparatus 1 shown in FIG. 6 is a flowchart showing details of ABS control processing including control on a μ-split road surface. It is the flowchart which showed the detail of the estimation W / C calculation. 5 is a flowchart showing details of μ split determination. It is the flowchart which showed the detail of the loading weight estimation process. It is the flowchart which showed the detail of the yacon control during control. The relationship between the loaded weight W on the vehicle and the center of gravity position X is examined. (A) is a schematic diagram showing the relationship between the on-vehicle state of the cargo vehicle such as a truck and the center of gravity position X, (b). Is a graph showing the relationship. 6 is a timing chart when ABS control is executed on a μ-split road surface. 6 is a timing chart when ABS control is executed on a μ-split road surface. 6 is a timing chart when ABS control is executed on a μ-split road surface. It is the flowchart which showed the detail of the in-control yaw control performed by brake ECU70 demonstrated in 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 shows a block configuration of each function of a brake control device 1 that realizes an ABS control device to which the first embodiment of the present invention is applied. The part which implement | achieves ABS control among this brake control apparatuses 1 is equivalent to an ABS control apparatus.

  First, the brake control device 1 of the present embodiment will be described. As shown in FIG. 1, the brake control device 1 includes a brake pedal 11, a booster device 12, a master cylinder (hereinafter referred to as M / C) 13, W / C 14, 15, 34, 35, and brake hydraulic pressure control. Actuator 50 is provided. The brake control device 1 is provided with a brake ECU 70. The brake ECU 70 functions as a part of various control means to control the braking force generated by the brake control device 1. . Specifically, the brake control device 1 includes wheel speed sensors 81 to 84 that output pulse signals corresponding to the wheel speeds of the wheels FL, FR, RL, and RR as detection signals. The detection signals of .about.84 and the detection signals of other sensors described later are input to the brake ECU 70, and the brake ECU 70 performs various calculations based on the input detection signals to control the braking force.

  FIG. 2 is a diagram showing a detailed structure of each part constituting the brake control device 1. As shown in this figure, when the driver depresses the brake pedal 11, the pedaling force is boosted by the booster 12, and the master pistons 13a and 13b disposed in the M / C 13 are pressed. As a result, the same M / C pressure is generated in the primary chamber 13c and the secondary chamber 13d defined by the master pistons 13a and 13b. The M / C pressure is transmitted to each of the W / Cs 14, 15, 34, and 35 through the brake fluid pressure control actuator 50.

  Here, the M / C 13 includes a master reservoir 13e having a passage communicating with each of the primary chamber 13c and the secondary chamber 13d.

  The brake fluid pressure control actuator 50 has a first piping system 50a and a second piping system 50b. The first piping system 50a controls the brake fluid pressure applied to the left front wheel FL and the right rear wheel RR, and the second piping system 50b controls the brake fluid pressure applied to the right front wheel FR and the left rear wheel RL.

  Since the 1st piping system 50a and the 2nd piping system 50b are the same structures, below, the 1st piping system 50a is explained and explanation is omitted about the 2nd piping system 50b.

  The first piping system 50a transmits the M / C pressure described above to the W / C 14 provided on the left front wheel FL and the W / C 15 provided on the right rear wheel RR, and generates a W / C pressure. A pipe A is provided.

  The pipe A is branched into two pipes A1 and A2. The pipeline A1 is provided with a first pressure increase control valve 17 that controls the increase of the brake fluid pressure to the W / C 14, and the pipeline A2 is a first pressure that controls the increase of the brake fluid pressure to the W / C 15. A two pressure increase control valve 18 is provided.

  The first and second pressure increase control valves 17 and 18 function as linear valves that linearly control the differential pressure generated between the upstream and downstream sides. The first and second pressure-increasing control valves 17 and 18 are also basically composed of normally open type electromagnetic valves that can control the communication / shut-off state. The second pressure increase control valves 17 and 18 can function as linear valves.

  The first and second pressure-increasing control valves 17 and 18 in the pipeline A and the pipeline B serving as a pressure-reducing pipeline connecting the reservoirs 20 to the W / Cs 14 and 15 can be controlled to be in communication / blocked state 2. A first pressure-reducing control valve 21 and a second pressure-reducing control valve 22 constituted by position electromagnetic valves are respectively provided. The first and second pressure reducing control valves 21 and 22 are normally closed.

  A conduit C serving as a reflux conduit is disposed between the reservoir 20 and the conduit A serving as a main conduit. The pipe C is provided with a self-priming pump 19 driven by a motor 60 that sucks and discharges brake fluid from the reservoir 20 toward the M / C 13 side or the W / C 14, 15 side.

  The brake ECU 70 corresponds to the ABS control device of the present invention that controls the control system of the brake control device 1, and is constituted by a known microcomputer including a CPU, ROM, RAM, I / O, and the like. In accordance with the program stored in, various operations relating to the ABS control are executed. For example, the brake ECU 70 receives the detection signals of the wheel speed sensors 81 to 84 shown in FIGS. 1 and 2 to obtain the wheel speed, obtains the vehicle speed from the wheel speed, or differentiates the vehicle by time-differentiating the vehicle speed. I'm seeking speed. Further, a detection signal from a stop lamp switch (STP) 85 is also input to the brake ECU 70, so that it can be determined whether or not braking is being performed. Further, detection signals from the steering angle sensor 86, the yaw rate (yaw angular velocity) sensor 87, and the lateral acceleration sensor 88 are input to the brake ECU 70, and these detection signals are used and stored in a ROM or the like. The weight on the vehicle is also estimated by performing various calculations according to the program.

  Based on the electrical signal from the brake ECU 70, current supply control to the control valves 17, 18, 21, 22, 37, 38, 41, 42 in the brake hydraulic pressure control actuator 50 configured as described above, and Voltage application control to the motor 60 for driving the pumps 19 and 39 is executed. Thereby, the W / C pressure generated in each W / C 14, 15, 34, 35 is controlled, and the braking force of each wheel FL-RR is controlled.

  Specifically, in the brake fluid pressure control actuator 50, a drive voltage is applied from the brake ECU 70 to the motor 60 and the control valves 17, 18, 21, 22, 37, 38, 41, 42 are provided. When a control current is supplied to the solenoid, the control valves 17, 18, 21, 22, 37, 38, 41, 42 in the brake fluid pressure control actuator 50 are driven according to the control current, The brake piping route is set. And the brake fluid pressure according to the set route of the brake piping is generated in the W / C 14, 15, 34, 35 so that the braking force generated in each of the wheels FL to RR can be controlled.

  Next, details of the ABS control of the brake control device 1 configured as described above will be described. FIG. 3 is a flowchart showing details of the ABS control process including the control on the μ split road surface. 4 to 7 are flowcharts showing details of individual processes executed in the ABS control process. Hereinafter, the ABS control process will be described with reference to FIGS. The ABS control process shown in FIG. 3 is executed for each wheel for each control cycle when an ignition switch (not shown) is turned on.

  First, in step 100 shown in FIG. 3, input processing is performed. Specifically, detection signals from the wheel speed sensors 81 to 84 are input. In step 105, the wheel acceleration of each wheel is calculated or the wheel acceleration is calculated by differentiating each wheel speed. Subsequently, in step 110, an estimated vehicle body speed is calculated from a wheel speed of each wheel by a known method, and an estimated wheel acceleration of each wheel is calculated by differentiating the calculated estimated vehicle body speed.

  Next, in step 115, an estimated W / C pressure calculation is performed. FIG. 4 is a flowchart showing details of this estimated W / C calculation.

  First, in step 200, it is determined whether or not ABS control is being performed. Since the ABS control start determination is performed in the control mode setting of step 125 in FIG. 3 described later, a flag indicating that the ABS control is being performed when the ABS control start condition is satisfied is set. Whether or not ABS control is in progress can be determined based on whether or not is set. If it is determined that the ABS control is not being performed but the ABS control is not being performed, the process proceeds to step 205.

  In step 205, it is determined whether or not the stop lamp switch 85 is pressed. If the stop lamp switch 85 is not pressed, braking is not in progress, and therefore the routine proceeds to step 210, where the estimated W / C pressure PWC is obtained from the estimated vehicle deceleration (negative value of the estimated vehicle acceleration). Since the relationship between the estimated vehicle body deceleration and the estimated W / C pressure PWC can be expressed by a well-known map or arithmetic expression, the estimated W / C pressure PWC can be obtained from the estimated vehicle body deceleration using this. . However, although the estimated W / C pressure PWC is obtained, in this case, since the braking is not being performed, the estimated W / C pressure PWC is basically zero.

  On the other hand, if the stop lamp switch 85 is pressed in step 205, braking is in progress, so the process proceeds to step 215, and either the value estimated from the braking start time or the value calculated from the estimated vehicle deceleration is smaller. This is the estimated W / C pressure PWC. In addition, since it is well known also about estimating a W / C pressure from braking start time, description is abbreviate | omitted for details.

  On the other hand, if it is determined in step 200 that the ABS control is being performed, the process proceeds to step 220, and it is determined whether the control mode is the pressure reduction mode or the pressure increase mode. The control mode is set in the control mode setting in step 125 of FIG. 3 described later, and the determination of this step is performed by reading the set mode. If the pressure reduction mode is selected, the process proceeds to step 225, where the estimated W / C pressure PWC obtained in step 215 before the ABS control is used as a reference value, and the pressure is reduced from the reference value for the pressure reduction time of the ABS control. The estimated W / C pressure PWC is obtained by subtracting the wax value. If the pressure increasing mode is selected, the process proceeds to step 230, where the estimated W / C pressure PWC determined in step 225 is used as a reference value, and the reference value is increased from the pressure increasing gradient of the ABS control. The estimated W / C pressure PWC is obtained by adding the wax value. As described above, the estimated W / C pressure calculation shown in FIG. 4 is performed.

  Then, the process proceeds to step 120 in FIG. 3 to determine μ split, that is, whether or not the road surface being traveled is a μ split road surface, and which of the left and right wheels is a high μ road. FIG. 5 is a flowchart showing the details of the μ split determination.

  First, in step 300, it is determined whether or not ABS control is being performed. The determination is made by the same method as in step 200 described above. If a negative determination is made here, the process proceeds to step 305 to determine that the μ split state is not established. In this case, even if the vehicle is traveling on the μ-split road surface, it is not in the μ-split state because the spin is not generated due to the difference in the road surface μ between the left and right wheels. If an affirmative determination is made in step 300, the process proceeds to step 310.

  In step 310, the estimated W / C pressure of the right front wheel FR is obtained. The estimated W / C pressure of the right front wheel FR is a value proportional to the difference between the pressure increase time of the right front wheel FR and the pressure reduction time of the right front wheel FR, and this difference is simply calculated as the estimated W / C pressure of the right front wheel FR. And Note that the pressure increase time of the right front wheel FR and the pressure decrease time of the right front wheel FR mean a pressure increase time and a pressure decrease time set in the pressure increase mode and the pressure decrease mode of the ABS control for the right front wheel FR. is doing.

  Similarly, in step 315, the estimated W / C pressure of the left front wheel FL is obtained. Since the estimated W / C pressure of the left front wheel FL is a value proportional to the difference between the pressure increase time of the left front wheel FL and the pressure reduction time of the left front wheel FL, this difference is simply calculated as the estimated W / C pressure of the left front wheel FL. And Note that the pressure increase time of the left front wheel FL and the pressure decrease time of the left front wheel FL mean the pressure increase time and the pressure decrease time set in the ABS control pressure increase mode and pressure reduction mode for the left front wheel FL. is doing.

  Subsequently, the process proceeds to step 320, and whether or not the difference obtained by subtracting the estimated W / C pressure of the left front wheel FL from the estimated W / C pressure of the right front wheel FR obtained in steps 310 and 315 is equal to or greater than a threshold value (predetermined value). Determine whether. If an affirmative determination is made here, it means that the estimated W / C pressure of the right front wheel FR is larger than the estimated W / C pressure of the left front wheel FL, so the routine proceeds to step 325 and in the μ split state. Yes, and the process is terminated assuming that the right wheel FR side is a high μ road.

  If a negative determination is made in step 320, conversely, in step 330, the estimated W / C pressure of the right front wheel FR is subtracted from the estimated W / C pressure of the left front wheel FL obtained in steps 315 and 310. It is determined whether or not the difference is greater than or equal to a threshold value (predetermined value). This threshold value is the same as the threshold value used in step 320. If an affirmative determination is made here, it means that the estimated W / C pressure of the left front wheel FL is larger than the estimated W / C pressure of the right front wheel FR, so the routine proceeds to step 335 and in the μ split state. The process is terminated assuming that there is a high μ road on the left wheel FL side.

  If a negative determination is made in either step 320 or step 330, there is no difference in the estimated W / C pressure between the left and right wheels FR and RL to the extent that it can be called a μ split road surface. . In this way, μ split determination is performed.

  Subsequently, the process proceeds to step 125 in FIG. 3 to set the control mode. In the control mode setting, it is determined whether or not the ABS control start condition is satisfied, the pressure reduction mode, the holding mode and the pressure increasing mode are set when the ABS control is started, and the ABS control end condition is determined or not. Etc. are performed. Since these are already known, the details are omitted, but in this embodiment, when the slip ratio of the wheel on the low μ road side exceeds the ABS control start threshold, the wheel on the high μ road side is Regardless of the slip ratio, both the low μ wheel and the high μ wheel perform the select low control for starting the pressure reduction control in the ABS control. When the ABS control start condition is satisfied, a flag to that effect is set, and the flag remains set until the ABS control end condition is satisfied. In addition, when each mode is set, control corresponding to each mode is executed based on an output process in step 170 described later. When the decompression mode is set, the decompression control is performed. When the retention mode is set, the holding control and the increase are performed. When the pressure mode is set, the pressure increase control is executed.

  At the time of pressure reduction control, the first to fourth pressure increase control valves 17, 18, 37, and 38 are shut off, and the first to fourth pressure increase control valves 21, 22, 41, and 42 are set to a communication state. The pumps 19 and 39 are operated by driving the motor 60. As a result, the brake fluid in the pipelines A and E flows between the first and second reservoirs 20 between the first to fourth pressure increase control valves 17, 18, 37 and 38 and the W / C 14, 15, 34 and 35. , 40 escaped. Then, the brake fluid is sucked and discharged by the pumps 19 and 39 and returned between the M / C 13 of the pipes A and E and the pressure increase control valves 17, 18, 37 and 38. Thereby, the W / C pressure of each W / C 14, 15, 34, 35 is reduced.

  In the holding control, the first to fourth pressure increase control valves 17, 18, 37, 38 are shut off, and the first to fourth pressure reduction control valves 21, 22, 41, 42 are also shut off. Thereby, W / C pressure of each W / C14, 15, 34, and 35 is held.

  At the time of the pressure increase control, the control for reducing the energization to the first to fourth pressure increase control valves 17, 18, 37, 38 is started and opened, and the first to fourth pressure decrease control valves 21, 22, 41, 42 is set to the cutoff state. Regarding the first to fourth pressure increase control valves 17, 18, 37, and 38, first, between the upstream and downstream of the first to fourth pressure increase control valves 17, 18, 37, and 38 immediately before the pressure increase control is executed. The amount of current supplied to the solenoid is controlled so that the pressure difference is gradually reduced and then the pressure difference gradually decreases. As a result, the W / C pressure generated in the W / C 14, 15, 34, 35 located downstream of the first to fourth pressure increase control valves 17, 18, 37, 38 and the high pressure first to fourth pressure increase. The differential pressure between the brake fluid pressures upstream of the control valves 17, 18, 37, 38 is reduced, and the W / C pressures of the W / Cs 14, 15, 34, 35 are increased.

  Then, it progresses to step 130 and performs a load weight estimation process. This load weight estimation process is performed based on the concept of load weight estimation described below.

  First, considering the behavior when the vehicle makes a turning motion, when steering is performed by the driver operating the steering, the tire angle with respect to the vehicle longitudinal direction via the rack and pinion is accordingly accompanied. The rudder angle which is the angle of is adjusted. Since yaw is generated along with the adjustment of the tire angle, a yaw rate is generated. That is, the behavior occurs in the order of steering → steering angle adjustment → yaw rate generation.

  Then, when the yaw rate is generated after the rudder angle is generated, the yaw rate is generated immediately following the adjustment of the rudder angle when the steering is performed slowly, but when the steering is performed quickly, the yaw rate is generated. The yaw rate will be delayed after the adjustment. For this reason, there is a correlation between the steering angular speed representing the steering speed and the time from the adjustment of the steering angle to the generation of the yaw rate. Since the time from the adjustment of the steering angle to the generation of the yaw rate is expressed by the phase difference between the steering angle and the yaw rate, the relationship between the steering angle and the phase difference between the yaw rate with respect to the steering angular speed is set using a map or a function expression can do.

  Further, assuming that the steering speed and the road surface condition are the same, the phase of the vehicle behavior increases as the total vehicle weight increases. Since the total vehicle weight is a value obtained by adding the load weight that is the variable weight to the vehicle weight when the vehicle is empty, which is a constant weight, it can be said that the phase delay of the vehicle behavior depends on the load weight. Therefore, the phase difference between the rudder angle and the yaw rate also changes in accordance with the load weight, and the phase difference between the rudder angle and the yaw rate increases as the load weight increases. Therefore, if the relationship between the rudder angle and the yaw rate relative to the rudder angular velocity is obtained in advance by experiment or the like for each load weight, the relationship and the rudder angular velocity or rudder angle obtained from the detection signals of the rudder angle sensor 86 and the yaw rate sensor 87 are obtained. The load weight can be estimated based on the phase difference between the yaw rate and the behavior when the vehicle turns.

  Next, consider the center of gravity of the vehicle. FIG. 8 shows the relationship between the loaded weight W on the vehicle and the center of gravity position X. FIG. 8A shows the relationship between the loaded weight W on the cargo vehicle such as a truck and the center of gravity position X. FIG. 8B is a graph showing the relationship.

As shown in FIG. 8 (a), when a load is placed on a freight vehicle, it is placed on the loading platform located at the rear of the passenger compartment, and further placed on the upper position of the load placed in the past. The more you load, the more the center of gravity moves backward. For this reason, for example, when the center of gravity position X ₀ when an empty vehicle without a load is loaded is the initial center of gravity position X ₀ , the center of gravity position X ₁ when the load is loaded by the loaded weight W ₁ is behind the center of gravity position X _0. Moving. Further, the center of gravity position X ₂ when the load is loaded by the loading weight W ₂ larger than the loading weight W ₁ further moves rearward from the center of gravity position X ₁ . For this reason, as shown in FIG. 8B, a relationship is established between the center of gravity position X and the loaded weight W that the amount of movement of the center of gravity position X toward the rear of the vehicle increases as the loaded weight W increases. For this reason, the loading weight X can be estimated by detecting the gravity center position X.

The center-of-gravity position X can be detected by a load sensor provided in the suspension or the like, but can also be detected based on the relationship between the yaw rate and the lateral acceleration, for example. That is, when the center-of-gravity position X moves, the yaw moment generated in the vehicle is not significantly affected, and the yaw rate does not change. However, the lateral acceleration is affected by the movement of the gravity center position X. Generally, since the lateral acceleration sensor is installed in the vicinity of the center of gravity position X ₀ when the vehicle is empty, it is not affected by the yaw moment and does not include the yaw component in the detection signal. Since the lateral acceleration sensor is placed away from the gravity center position X, it is affected by the yaw moment, and the yaw component is superimposed on the detection signal.

  For this reason, the relationship between the phase difference between the yaw rate and the lateral acceleration with respect to the yaw angular acceleration changes with the movement of the gravity center position X, that is, the fluctuation of the loaded weight W. Therefore, if the relationship between the phase difference between the yaw rate and the lateral acceleration with respect to the yaw angular acceleration is obtained in advance by experiment or the like for each load weight, the relationship, the yaw rate obtained from the detection signals of the yaw rate sensor 87 and the lateral acceleration sensor 88, and the derivative thereof. The loaded weight W can be estimated based on the yaw angular acceleration and the lateral acceleration Gy obtained from the values, that is, based on the gravity center position X.

  Based on the above knowledge, the load weight can be estimated. FIG. 6 is a flowchart showing details of the load weight estimation process based on the above-described concept.

  First, in step 400, the steering angle, yaw rate, and lateral acceleration Gy are calculated based on detection signals from the steering angle sensor 86, the yaw rate sensor 87, and the lateral acceleration sensor 88. Specifically, the rudder angular velocity represented by the derivative value of the rudder angle is calculated by differentiating the rudder angle with respect to time. Further, the yaw angular acceleration represented by the differential value of the yaw rate is calculated by differentiating the yaw rate with time. Further, the phase difference between the steering angle and the yaw rate and the phase difference between the yaw rate and the lateral acceleration Gy are calculated. The phase difference between the steering angle and the yaw rate is obtained, for example, by comparing the detected waveform of the steering angle and the detected waveform of the yaw rate, for example, peak values, and calculating the delay time. Similarly, the phase difference between the yaw rate and the lateral acceleration Gy is obtained, for example, by comparing the detected waveform of the yaw rate and the detected waveform of the lateral acceleration Gy, for example, peak values, and calculating the delay time.

  Next, the routine proceeds to step 410, and the loaded weight is estimated based on the behavior when the vehicle turns. Specifically, based on the relationship between the rudder angular velocity calculated in step 400, the phase difference between the rudder angle and the yaw rate, and the phase difference between the rudder angle and the yaw rate with respect to the rudder angular velocity that has been obtained and stored in advance through experiments or the like. Estimate the loading weight. Here, as shown in FIG. 6, a map (MAP1) indicating the relationship between the steering angle and the phase difference between the steering angle and the yaw rate is obtained and stored in advance by experiments or the like. Therefore, the rudder angular velocity calculated in step 400 and the phase difference between the rudder angle and the yaw rate are assumed to be any position on the map (the rudder angular velocity is the X axis, and the phase difference between the rudder angle and the yaw rate is the Y axis). The load weight is estimated by determining whether it corresponds to the XY coordinates of the calculated value at that time.

  In other words, as shown in the figure, the relationship between the steering angle and yaw rate relative to the steering angular speed is indicated by three lines according to the loading weight, so there is no loading weight (when empty), small, medium, large Are divided into four areas. Therefore, depending on the rudder angular velocity calculated in step 400 and the phase difference between the rudder angle and the yaw rate, it is discriminated whether there is no load or the load weight is small to large. . The loaded weight determined at this time is stored as the loaded weight of MAP1.

  Although only three lines are shown here, a more specific absolute value of the loaded weight can be obtained by indicating a plurality of lines. Of course, by substituting the rudder angular velocity and the phase difference between the rudder angle and the yaw rate into the function formula showing the relationship between the rudder angle and the yaw rate relative to the rudder angular velocity, there is no load or the load weight is small. It is also possible to determine whether the value is large or to obtain the absolute value of the loaded weight.

  Subsequently, the process proceeds to step 420, and the loaded weight is estimated based on the position of the center of gravity. Specifically, the yaw angular acceleration calculated in step 400, the phase difference between the yaw rate and the lateral acceleration, and the yaw rate and the lateral acceleration with respect to the yaw angular acceleration previously determined by experiment or the like and stored for each vehicle gravity center position are calculated. The load weight is estimated based on the phase difference relationship. Here, as shown in FIG. 6, a map showing the relationship between the phase difference between the yaw rate and the lateral acceleration with respect to the yaw angular acceleration according to the position of the center of gravity of the vehicle is created in advance by experiments or the like. Since it is regarded as a map shown for each vehicle loading weight, a map (MAP2) showing the relationship between the phase difference between the yaw rate and the lateral acceleration with respect to the yaw angular acceleration for each vehicle weight is obtained and stored. For this reason, the yaw angular acceleration calculated in step 400 and the phase difference between the yaw rate and the lateral acceleration are in any position on the map shown in the figure (the yaw angular acceleration is the X axis, and the phase difference between the yaw rate and the lateral acceleration is the Y axis. The load weight is estimated by discriminating to which range the XY coordinates of the calculated value at the time of comparison correspond to the range divided by the load weight.

  That is, as shown in the figure, the relationship between the phase difference between the yaw rate and the lateral acceleration with respect to the yaw angular acceleration is indicated by three lines according to the loading weight, so that the loading weight is zero (when empty), small, medium, It is divided into four large areas. Therefore, it is determined whether there is no loading or whether the loading weight is small to large depending on which region of the map the yaw angular acceleration calculated in step 400 and the phase difference between the yaw rate and the lateral acceleration are located. To do. The loading weight determined at this time is stored as the loading weight of MAP2.

  Although only three lines are shown here, a more specific absolute value of the loaded weight can be obtained by indicating a plurality of lines. Of course, there is no stacking by substituting the yaw angular acceleration calculated in step 400 and the phase difference between the yaw rate and the lateral acceleration into the function equation indicating the relationship between the yaw rate and the phase difference with respect to the yaw angular acceleration. It is also possible to determine whether the state or the loaded weight is small to large, or it is possible to determine the absolute value of the loaded weight.

  Then, the process proceeds to step 430, where the MAP1 loading weight stored in step 410 and the MAP2 loading weight stored in step 420 are compared, and the smaller one is determined as the final loading weight (loading weight = MIN ( MAP1, MAP2)). At this time, the final loading is performed by another method based on the loading weights of MAP1 and MAP2, such as adopting the average value or the larger one of the loading weights of MAP1 and MAP2 instead of the smaller one of the loading weights of MAP1 and MAP2. The weight can also be determined. However, each time the load weight is estimated, the load weight is updated and finally updated to a value close to the actual load weight, so the larger one of the load weights of MAP1 and MAP2 from the beginning. By selecting the smaller one instead of selecting the load weight, it is possible to exclude the case where the load weight changes greatly due to noise.

  Thus, the loaded weight is estimated based on the behavior when the vehicle turns. That is, based on the relationship between the phase difference between the rudder angle and the yaw rate obtained in advance and the phase difference between the rudder angular velocity calculated from the detection signals of the sensors 86 to 88 and the rudder angle and yaw rate, Is estimated. The rudder angular velocity and the phase difference between the rudder angle and the yaw rate calculated from the detection signals of these sensors 86 to 88 are applied to the road surface when braking torque is applied, when four wheels slip, or when vibrations occur or in a very short time. Even when a disturbance factor such as a change occurs, the value takes into account the disturbance factor. For this reason, even if a disturbance factor occurs, an accurate load weight can be estimated.

  Here, the loaded weight is estimated based on the position of the center of gravity. That is, based on the relationship between the phase difference between the yaw rate and lateral acceleration with respect to the yaw angular acceleration obtained in advance and the steering angular velocity calculated from the detection signals of the sensors 86 to 88 and the phase difference between the steering angle and the yaw rate, Estimate the weight. Also in this case, the yaw angular acceleration calculated from the detection signals of the sensors 86 to 88 and the phase difference between the yaw rate and the lateral acceleration are applied when braking torque is applied, when slip occurs on the four wheels, or when vibration occurs. Even when a disturbance factor occurs such as when the road surface changes during a very short time, the value takes the disturbance factor into consideration. For this reason, even if a disturbance factor occurs, an accurate load weight can be estimated. Furthermore, since both the estimation of the loaded weight based on the behavior during the turning motion and the estimation of the loaded weight based on the position of the center of gravity are performed, it is possible to estimate the loaded weight more accurately.

  When the load weight estimation is completed in this way, the process proceeds to step 135. In step 135, it is determined whether or not the μ split state is set. This determination is performed based on the result of the μ split determination performed in step 120. That is, when it is determined that the μ split state is set in step 325 or step 335, an affirmative determination is made in this step, and when it is determined that the μ split state is not set in step 305, a negative determination is made in this step.

  Here, if not in the μ split state, the process proceeds to step 140, and independent control is performed in which ABS control is performed independently for each wheel FL to RR when the road surface is not a general split road surface. On the other hand, if it is in the μ split state, the routine proceeds to step 145, where it is determined whether or not the current ABS control processing is being executed for the front wheels FL and FR. If the front wheels are FL and FR, the process proceeds to step 150. If the front wheels are not FL and FR, the process proceeds to step 140 and independent control is performed.

  In step 150, it is determined whether or not the current ABS control process is being performed on the right front wheel FR. If the right front wheel FR is determined, the process proceeds to step 155 to determine whether the right wheel FR side is a high μ road. If it is the left front wheel FL, the routine proceeds to step 160, where it is determined whether or not the left wheel FL side is a high μ road. For the wheels determined to be high μ road, the process proceeds to step 165 to execute yaw control during ABS control (hereinafter referred to as in-control yaw control), and for wheels that are not determined to be high μ roads. Proceeding to step 140, independent control is executed.

  FIG. 7 is a flowchart showing details of the control yaw control. First, in step 500, a process to be performed next is selected based on how much the estimated load weight is. As the estimated load weight, the value obtained in the load weight estimation process in step 130 is used. Specifically, it is determined whether or not it is greater than or equal to the second weight threshold Load2. Here, the second weight threshold Load2 is larger than a first weight threshold Load1 described later. If the estimated load weight is equal to or greater than the second weight threshold Load2, the process proceeds to step 560.

  Next, if a negative determination is made in step 500, it is determined in step 501 whether or not the pressure reduction mode is set as the control mode for the front low μ wheel. That is, it is determined whether or not the control mode set for the front low-μ wheel in the control mode setting of step 125 in FIG. 3 is the pressure reduction mode. If the W / C pressure of the front high μ wheel is increased when the front low μ wheel is in the decompression mode, the hydraulic pressure difference between the W / C pressures of the left and right front wheels may suddenly increase. Therefore, the process proceeds to step 510 only when a negative determination is made here, and proceeds to step 540 when a positive determination is made.

  In the following step 510, it is determined whether the estimated load weight is less than the first weight threshold Load1 or less than the second weight threshold Load2 that is greater than or equal to the first weight threshold Load1 and larger. If the estimated load weight is less than the first weight threshold Load1, the process proceeds to Step 520. If the estimated load weight is less than the second weight threshold Load2 greater than or equal to the first weight threshold Load1, the process proceeds to Step 530.

  It is better to improve the vehicle stability when the load weight is small compared to the case when the load weight is large, so it is preferable to improve the vehicle stability. Since vehicle stability is high, it is preferable to increase braking performance. For this reason, in order to place importance on stability when the loaded weight is small, the hydraulic pressure difference between the W / C pressures of the left and right front wheels FL and FR should not be increased so much, and braking performance should be emphasized when the loaded weight is large. Then, control is performed to allow the hydraulic pressure difference between the left and right front wheels to increase to a certain extent.

  That is, when the hydraulic pressure difference between the left and right front wheels is not increased, the W / C pressure of the front high μ wheel cannot be increased so much that the braking performance cannot be improved. Since it is small, the yaw moment generated in the vehicle can be suppressed. For this reason, it becomes possible to prevent the occurrence of spin due to the difference between the left and right braking forces on the split road surface. On the contrary, when the hydraulic pressure difference between the W / C pressures of the left and right front wheels is allowed to increase to some extent, the braking performance can be improved because the W / C pressure of the front high μ wheel can be increased. In this case, there is a possibility that the yaw moment generated in the vehicle will increase because the hydraulic pressure difference between the left and right front wheels is large. However, if the loaded weight is large, the risk of spin is small, so the W / C pressure of the front high μ wheel is low. You can make it bigger.

  Therefore, in Step 520 and Step 530, the hydraulic pressure difference between the estimated W / C pressures of the left and right front wheels FL, FR, that is, the absolute difference between the estimated W / C pressure of the right front wheel FR and the estimated W / C pressure of the left front wheel FL. The value is compared with pressure thresholds Pold1, Pold2 (Pold1 <Pold2) of different magnitudes, and it is determined whether or not the hydraulic pressure difference is greater than the pressure thresholds Pold1, Pold2. Then, if the hydraulic pressure difference between the estimated W / C pressures of the left and right front wheels FL, FR is larger than the pressure thresholds Phold1, Hold2, the process proceeds to step 540, and if it is equal to or less than the pressure thresholds Phold1, Hold2, the process proceeds to step 550.

  In step 540, holding control is executed. Here, the amount of control current applied to the solenoids of the first to fourth pressure increase control valves 17, 18, 37, 38 and the first to fourth pressure decrease control valves 21, 22, 41, 42 in order to execute the holding control. Seeking. That is, if the pressure increase control is performed when the front low μ wheel is in the decompression mode or when the difference between the W / C pressures of the left and right front wheels FR and FL is increased to some extent, the left and right front wheels FR and FL are further controlled. The difference in the W / C pressure of the vehicle may become large, and the vehicle may become unstable. For this reason, the difference in the W / C pressure between the left and right front wheels FR and FL is prevented from becoming too large by holding control to hold the W / C pressure of the front high μ wheel.

  In step 550, the slow pressure increase control is executed. Specifically, in order to execute this slow pressure increase control, the solenoids of the first to fourth pressure increase control valves 17, 18, 37, 38 and the first to fourth pressure decrease control valves 21, 22, 41, 42 are provided. The energization amount of the control current to flow is obtained. The slow pressure increase control here means increasing the W / C pressure of the front high μ wheel by a relatively gentle pressure increase gradient. Although the form of pressure increase by the slow pressure increase control is not different from the normal pressure increase control described above, the mode of increase in the amount of energization to the solenoids of the pressure increase control valves 17, 18, 37, 38 is moderated to make it slow. It is possible to increase the pressure.

  Further, when it is determined in step 510 that the loaded weight is equal to or greater than the second weight threshold Load2, independent control is executed in step 560. That is, the ABS control similar to the case where the front high μ wheel is not a general split road surface is performed independently of the control state of the front low μ wheel. For this reason, when the loaded weight is large, it is possible to obtain a larger braking force by further increasing the W / C pressure of the front high-μ wheel. Therefore, the braking performance can be further improved.

  When the in-control yaw control is performed in this way, the process proceeds to step 170 in FIG. 3 and an output process is executed. Accordingly, the first to fourth pressure increase control valves 17, 18, 37, in order to perform the holding control, the slow pressure increase control, and the independent control set in the independent control executed in step 140 or the control during control. A control current is supplied to the solenoids 38 and the first to fourth pressure reduction control valves 21, 22, 41, 42. Thereby, various controls are executed.

  The effect when the ABS control as described above is executed will be described with reference to the timing chart when the ABS control is executed on the μ split road surface shown in FIGS. 9 to 11 show the ABS control according to the estimated load weight. FIG. 9 shows that when the estimated load weight is less than the first weight threshold Load1, FIG. 10 shows that the estimated load weight is not less than the first weight threshold Load1 and When the weight is less than the second weight threshold Load2, FIG. 11 shows the case where the estimated load weight is equal to or more than the second weight threshold Load1.

  First, in the case where the estimated load weight shown in FIG. 9 is less than the first weight threshold Load1, when the braking is started and the front low μ wheel satisfies the ABS control start condition at the time T1, the ABS control is started. By the low control, the pressure reduction mode is set for both the front low μ wheel and the front high μ wheel, and the pressure reduction control is started to decrease the W / C pressure. Then, since there is almost no deviation between the estimated vehicle body speed and the wheel speed in the front high μ wheel, the pressure reduction mode is immediately released at time T2, the pressure increase mode is set, and the pressure increase control is started. For this reason, the difference between the estimated W / C pressure of the front high μ wheel and the estimated W / C pressure of the front low μ wheel increases, and this difference exceeds the pressure threshold Phold1. Therefore, in the μ split determination (step 120), it is determined that the road surface is the μ split road surface, and it is also determined which of the left and right front wheels FR and FL is the wheel on the high μ road side (steps 325 and 335).

  When it is determined that the road surface is μ-split, the control yaw control (step 165) is executed for the front high μ wheel. Thus, when the front low μ wheel is in the pressure reduction mode (step 500), if the absolute value of the difference between the estimated W / C pressures of the left and right front wheels FR, FL exceeds the pressure threshold Phold1 (step 520), the time point At T3, the W / C pressure of the front high μ wheel is maintained (step 540). For this reason, while maintaining the W / C pressure of the front high μ wheel to increase the braking force, the difference between the left and right braking force due to the increase in the W / C pressure difference between the front high μ wheel and the front low μ wheel Generation can be suppressed.

  Next, when the wheel speed of the front low μ wheel is restored and the pressure increasing mode is set at the time point T4 after the holding mode, the absolute value of the difference between the estimated W / C pressures of the left and right front wheels FR and FL again becomes the pressure. It becomes below threshold value Hold1. For this reason, the W / C pressure of the front high μ wheel is slowly increased at time T5. Then, when the front low μ wheel is switched again to the pressure reduction mode at time T6, the W / C pressure of the front high μ wheel is maintained, and the above operation is repeated from time T7 to T8.

  Further, after the time points T8-T9 and T10, the W / C pressure of the front high μ wheel is controlled to be a value obtained by adding the pressure threshold Phold1 to the estimated W / C pressure of the front low μ wheel. In this way, by controlling the W / C pressure of the front high μ wheel in relation to the W / C pressure of the front low μ wheel, it is possible to reliably prevent the occurrence of spin due to the difference between the left and right braking forces.

  As described above, when the pressure increase control valves 17, 18, 37, 38 can generate a differential pressure linearly, and the front low μ wheel is in the pressure reduction mode, the left and right front wheels FR, FL are estimated. When the absolute value of the difference between the W / C pressures exceeds the pressure threshold Phold1, the W / C pressure of the front high μ wheel is maintained without being increased. Thereafter, when the W / C pressure of the front high μ wheel is increased, the pressure is increased slowly.

  By such an operation, it is possible to suppress an excessive increase in the braking force of the front high-μ wheel and thereby deteriorate the stability of the vehicle, and it is possible to prevent the vehicle from spinning due to a difference between the left and right braking force.

  Further, when the estimated load weight shown in FIG. 10 is equal to or more than the first weight threshold Load1 and less than the second weight threshold Load2, the same operation as that when the estimated load weight is less than the first weight threshold Load1 is basically performed. For this reason, from time T1 to time T10 in FIG. 10, the same operation as in FIG. 9 is performed, but the W / C difference between the front high μ wheel and the front low μ wheel is controlled for the front high μ wheel. Since the pressure threshold value Phold2 larger than the pressure threshold value Phold1 is exceeded, the W / C pressure of the front high μ wheel can be increased as compared with the case of FIG. That is, even if the front low μ wheel is set to the pressure reduction mode, the W / C pressure is maintained until the W / C difference between the front high μ wheel and the front low μ wheel exceeds the pressure threshold Phold2 larger than the pressure threshold Phold1. Therefore, it is possible to generate a higher W / C pressure in the front high μ wheel.

  Therefore, when the loaded weight is large to some extent, the W / C pressure of the front high μ wheel can be increased as much as possible while suppressing the deterioration of the vehicle stability by excessively increasing the braking force of the front high μ wheel. By doing so, it becomes possible to obtain a larger braking force. As a result, it is possible to improve the braking performance while ensuring the vehicle stability according to the vehicle weight, and to achieve both the vehicle stability and the braking performance.

  Further, in the case where the estimated load weight shown in FIG. 11 is equal to or greater than the second weight threshold Load2, it is assumed that the load weight is large and the vehicle stability is hardly impaired even if the W / C pressure is increased. Independent control is performed on the wheel side. For this reason, the same ABS control as in the case where the road surface is not a general split road surface is performed independently of the control mode set for the front low μ wheel and the W / C pressure of the front low μ wheel. For this reason, when the loaded weight is large, it is possible to obtain a larger braking force by further increasing the W / C pressure of the front high-μ wheel. Therefore, the braking performance can be further improved.

  As described above, while the yaw control during the control is performed, the braking force of the front high μ wheel is not increased excessively so that the stability of the vehicle is not deteriorated. It is also possible to improve the braking performance by changing the / C pressure. This makes it possible to achieve both vehicle stability and braking performance in accordance with the loaded weight, and to perform more optimal ABS control corresponding to changes in the loaded weight.

(Second Embodiment)
A second embodiment of the present invention will be described. The present embodiment is obtained by changing the processing content of the control yaw control performed by the brake ECU 70 with respect to the first embodiment, and is otherwise the same as the first embodiment. Only the different parts will be described.

  FIG. 12 is a flowchart showing details of the in-control yaw control that is executed by the brake ECU 70. Note that the ABS control process executed by the brake ECU 70 is the same as that in the first embodiment except for the in-control yaw rate control. In this embodiment, instead of the process shown in FIG. The in-control yaw control shown in FIG.

  First, in step 600, similarly to step 500 in FIG. 7, the next process to be performed is selected based on the estimated load weight. Specifically, it is determined whether or not the estimated load weight is equal to or greater than the weight threshold Load. The weight threshold Load here is set to a value that is assumed to be difficult for the vehicle to spin because the loaded weight is large and the vehicle stability is high. If the estimated load weight is equal to or greater than the weight threshold value Load, the process proceeds to step 660 to perform independent control. If the estimated load weight is less than the weight threshold value Load, the process proceeds to step 610.

  In the subsequent step 610, it is determined whether or not the pressure reduction mode is set as the control mode for the front low-μ wheel. If a negative determination is made here, the process proceeds to step 620, and if a positive determination is made, the process proceeds to step 640. In step 620, a pressure threshold Phold is set based on the estimated load weight. That is, the greater the loaded weight, the less likely the vehicle is to become unstable even if the hydraulic pressure difference between the left and right front wheels increases. Therefore, the pressure threshold value Phold corresponding to the estimated load weight is obtained so that the pressure threshold value Phold becomes higher as the estimated load weight increases. Here, as shown in step 620, the pressure threshold Phold corresponding to the estimated load weight is obtained using a map in which the pressure threshold Phold increases as the estimated load weight increases. It is also possible to set using a functional expression that represents the relationship between the pressure threshold Phold and the pressure threshold Phold.

  Then, the process proceeds to step 630, where it is determined whether or not the hydraulic pressure difference between the estimated W / C pressures of the left and right front wheels FL, FR is greater than the pressure threshold value Phold determined in step 620. If determined, the process proceeds to step 650. At this time, since the pressure threshold value Phold obtained in step 620 is a value corresponding to the estimated load weight, the holding control in step 640 is executed according to the estimated load weight, or the slow pressure increase control in step 650 is performed. It will be decided whether to execute.

  As described above, the control yaw control is performed in the present embodiment. As described above, the pressure threshold Phold can be made variable according to the estimated load weight, and the holding control and the slow pressure increase control can be selected based on the pressure threshold Phold set according to the estimated load weight. . In this way, it is possible to perform the optimum ABS control according to the estimated load weight more finely.

(Other embodiments)
In each of the above-described embodiments, when the hydraulic pressure difference between the W / C pressures of the left and right front wheels FL and FR exceeds the pressure thresholds Phold, Hold1, and Hold2, in the in-control yaw control, the slow pressure increase control is executed. In the slow pressure increase control, the W / C pressure of the front high-μ wheel is increased by a relatively gentle pressure increase gradient, but the pressure increase gradient at this time may be set according to the estimated load weight. . For example, the pressure increase gradient in the slow pressure increase control can be increased as the loaded weight increases. If it does in this way, it can be set as the pressure increase gradient according to loading weight, and can balance the stability and braking nature of vehicles according to loading weight more.

  In addition, the weight thresholds Load, Load1, and Load2, and the pressure thresholds Hold, Hold1, and Hold2 described in the above embodiments may be variable according to the road surface condition and the vehicle. For example, it can be made variable according to the difference between the right and left road surface μ of the μ split road surface. For example, as the difference between the road surface μ between the high μ road and the low μ road is larger, the weight thresholds Load, Load1, Load2, and the pressure thresholds Phold, Hold1, Hold2 are adjusted to be more difficult to spin, and conversely If this difference is small, it is relatively difficult to spin, so these values may be increased to increase the braking force of the wheels on the high μ road side. The difference between the road surface μ between the high μ road and the low μ road is obtained by calculating the difference between the estimated W / C pressures of the left and right front wheels FR and FL in steps 320 and 330. The magnitude of the difference at this time is high. Since this corresponds to the difference in the road surface μ between the μ road and the low μ road, the weight thresholds Load, Load1, and Load2, and the pressure thresholds Hold, Hold1, and Hold2 may be changed based on this difference.

  DESCRIPTION OF SYMBOLS 1 ... Brake control apparatus, 11 ... Brake pedal, 13 ... M / C, 14, 15, 34, 35 ... W / C, 17, 18, 37, 38 ... 1st-4th pressure increase control valve, 19, 39 ... Pump, 20, 40 ... Reservoir, 21, 22, 41, 42 ... First to fourth pressure reducing control valves, 50 ... Brake hydraulic pressure control actuator, 50a, 50b ... First, second piping system, 60 ... Motor , 70 ... Brake ECU, 81-84 ... Wheel speed sensors, 85 ... Stop switch, 86 ... Rudder angle sensor, 87 ... Yaw rate sensor, 88 ... Lateral acceleration sensor, A-C, E-G ... Pipe line, FL- RR ... each wheel

Claims (6)

When driving on split road surfaces with different road surface friction coefficients μ on the left and right sides of the vehicle, the road surface friction coefficient μ is low.The road surface friction coefficient μ is high. Regardless of whether or not the road-side wheels satisfy the anti-skid control start condition, the anti-skid control performs anti-skid control and the low-side wheels also perform select-low control that starts the pressure reduction control in the anti-skid control. In the skid control device,
Estimated wheel cylinder pressure calculating means (115) for calculating the estimated wheel cylinder pressure of each of the left and right front wheels;
Μ split determination means (120) for determining whether the road surface during travel of the vehicle is the μ split road surface, and which of right and left of the road surface during travel is a high μ road side or a low μ road side;
Load weight estimating means (130) for estimating the load weight on the vehicle;
Pressure threshold value setting means (510, 620) for setting a pressure threshold value (Pold, Hold1, Hold2) corresponding to the loaded weight so as to increase as the loaded weight increases;
The μ split determination means determines that the road is a μ split road surface and a high μ road side and a low μ road side, and anti-skid control is started on the μ split road surface. When the wheel is in pressure-increasing mode, the anti-skid control pressure-reducing mode is not set on the low-μ road side wheel among the left and right front wheels, and the estimated wheels of the left and right front wheels respectively. If the difference in cylinder pressure is less than the pressure threshold set by the pressure threshold setting means, the solenoid of the pressure-increasing control linear valve (17, 37) for controlling the increase in the wheel cylinder pressure on the high μ road side By controlling the energization amount, the energization amount control means (540 to 560, 640 to 66) which makes the pressure increase gradient lower than the pressure increase gradient when the pressure increase control linear valve is in the communication state. 0). An anti-skid control device characterized by comprising:   The energization amount control means reduces the anti-skid control to the wheel on the low μ road side among the left and right front wheels when the wheel on the high μ road side of the left and right front wheels is increased in pressure increasing mode. When the mode is not set and the difference between the estimated wheel cylinder pressures of the left and right front wheels is equal to or greater than the pressure threshold, the pressure increase control linear valve of the high μ road side controls the pressure increase of the wheel cylinder pressure. 2. The anti-skid control device according to claim 1, wherein the wheel cylinder pressure of the wheel on the high μ road side is maintained by controlling an energization amount to the solenoid.   When the load weight estimated by the load weight estimation means is less than a first weight threshold (Load1), the pressure threshold setting means sets the pressure threshold to a first pressure threshold (Pold1), and the load weight estimation When the load weight estimated by the means is equal to or greater than the first weight threshold and less than a second weight threshold (Load2) greater than the first weight threshold, the pressure threshold setting means sets the pressure threshold to the first pressure. The anti-skid control device according to claim 1, wherein the anti-skid control device is set to a second pressure threshold (Pold2) larger than the threshold.   When the load weight estimated by the load weight estimation means is equal to or greater than the second weight threshold (Load2), the energization amount control means is configured to control the low μ road side of the left and right front wheels on the high μ road side. The anti-skid control apparatus according to claim 3, wherein the anti-skid control is performed independently of a wheel.   When the load weight estimated by the load weight estimation means is equal to or greater than a predetermined weight threshold (Load), the energization amount control means is configured to select the wheel on the low μ road side for the wheel on the high μ road side among the left and right front wheels. The anti-skid control device according to claim 1, wherein the anti-skid control is performed independently of the anti-skid control.   6. The energization amount control means makes the pressure increase gradient at the time of the slow pressure increase variable according to the load weight estimated by the load weight estimation means. The anti-skid control apparatus as described in one.

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