JP4910987B2 - Vehicle that accelerates ABS operation start during snowfade elimination control - Google Patents

Description

  The present invention is intended to prevent moisture that has entered between the brake disc and the pad from icing there while the vehicle is parked in a cold climate, particularly under snow, or when the vehicle is driven on a snowy road. Phenomenon in which the ice and snow splashed into the brakes enter between the disc and the pad of the braking device, causing the friction coefficient between the disc and the pad to decrease, resulting in a decrease in braking force (hereinafter referred to as “snow fade”) (Referred to as control).

Because the outside air temperature is below the set value and the deceleration does not increase as the brake cylinder hydraulic pressure increases, it is determined that a snow fade has occurred. Patent Document 1 below discloses that snow fade is eliminated by repeating contact and separation between the brake pad and the brake pad.
JP2003-11800

  Ice droplets sandwiched between the brake disc and brake pad periodically repeat pressing the brake pad against the brake disc and pulling the brake pad away from the brake disc, or temporarily place the brake pad on the brake disc. Since the servo gain of the braking device is temporarily increased so as to push strongly, it is crushed, melted and becomes water, and is discharged from the clamping part between the brake disc and the brake pad, so the friction coefficient between the disc and the pad is In any case, the braking force suddenly increases at the moment when the coefficient of friction is recovered, and the slip ratio of the wheels rapidly increases, resulting in instability of driving, and sudden braking may cause the driver to feel uncomfortable. is there.

  The present invention addresses the above-mentioned problem relating to the elimination of snow fade, and provides a vehicle capable of eliminating snow fade so that the sudden increase in slip rate and sudden braking feeling of the wheels do not occur at the moment of elimination of snow fade. It is an issue.

  In order to solve the above-described problems, the present invention provides a vehicle in which snow fade elimination control is performed in response to the occurrence of snow fade in a braking device. The present invention proposes a vehicle characterized in that an ABS operation start early control is performed in which the ABS operation start condition is relaxed and the ABS operation start is advanced.

  The ABS operation start condition is that the wheel slip ratio exceeds a predetermined slip ratio threshold, and the ABS operation start early control is to lower the slip ratio threshold, or the ABS operation start condition is that the wheel slip ratio is predetermined. The ABS operation start early control may be to shorten the predetermined time, or to lower the slip ratio threshold and shorten the predetermined time. .

  The vehicle is used when the outside air temperature is not more than a predetermined temperature and the deceleration of rotation of the non-driving wheels is not more than a value obtained by multiplying a braking hydraulic pressure applied to the braking device by a predetermined first coefficient, or driving wheels. When the deceleration of the rotation of the vehicle is equal to or less than the sum of the deceleration due to engine braking and the braking hydraulic pressure applied to the braking device multiplied by a predetermined first coefficient, it is estimated that a snow fade has occurred on the wheel. The cancellation control may be performed, and the deceleration of the rotation of the non-driven wheel is not less than the value obtained by multiplying the braking hydraulic pressure applied to the braking device by a predetermined second coefficient larger than the first coefficient. Or when the deceleration of the rotation of the driving wheel for which the snow fade elimination control is being executed is reduced by the engine brake and the braking hydraulic pressure applied to the braking device by a predetermined second coefficient larger than the first coefficient. Multiplied value When it is no longer the sum below, it may be adapted to release the snow fade elimination control.

  Snowfade elimination control periodically repeats pressing the brake pad against the brake disc and pulling the brake pad away from the brake disc, or increases the ratio of the braking force applied to the wheel with respect to the depression depth of the brake pedal The servo gain of the braking device may be increased temporarily.

  The snowfade elimination control is performed on the left and right front wheels when it is estimated that snowfade has occurred on one of the left and right front wheels, and it is estimated that snowfade has occurred on either one of the left and right rear wheels. Sometimes it can be done for the left and right rear wheels.

  The recovery of the coefficient of friction between the brake disc and the brake pad due to the elimination of the snow fade occurs fairly rapidly, so if the force to press the brake pad against the brake disc is kept as it is, The braking force that suppresses the rotation of the wheels suddenly increases, and the vehicle body suddenly decelerates, and at the same time, the wheel slip rate increases. At this time, if the ABS operation start early control that loosens the conditions for starting the ABS operation is performed, the initial friction coefficient between the brake disc and the brake pad starts to increase rapidly with the cancellation of the snow fade. At this stage, the ABS is actuated to loosen the pressing force of the brake pad against the brake disc, the braking force recovery speed due to the elimination of snow fade is moderated, the sudden deceleration of the vehicle body is suppressed, and the slip rate generated on the wheels is reduced. While maintaining running stability, it is possible to prevent the driver from feeling uncomfortable.

  In order to speed up the ABS operation start, when the ABS operation start condition is that the wheel slip ratio exceeds a predetermined slip ratio threshold, the slip ratio threshold is lowered, and the wheel slip ratio sets a predetermined slip ratio threshold. If the predetermined time is exceeded, the predetermined time can be shortened, or the slip ratio threshold can be lowered and the predetermined time can be shortened.

  If the outside air temperature is a predetermined temperature or less and the wheel is a non-driven wheel, when the deceleration of rotation is equal to or less than a value obtained by multiplying the braking hydraulic pressure applied to the braking device by a predetermined first coefficient, Also, if the wheel is a driving wheel, when the deceleration of rotation is equal to or less than the sum of the deceleration by the engine brake and the braking hydraulic pressure applied to the braking device multiplied by a predetermined first coefficient, If it is assumed that snow fade has occurred and snow fade elimination control is performed, the occurrence of snow fade can be accurately estimated regardless of whether the wheel is a non-drive wheel or a drive wheel. Fade cancellation control can be performed. In addition, when the deceleration of rotation of the non-driving wheel for which the snow fade elimination control is being performed is no longer less than the value obtained by multiplying the braking hydraulic pressure applied to the braking device by a predetermined second coefficient larger than the first coefficient. Or, the deceleration of the rotation of the drive wheel for which the snow fade elimination control is being performed is obtained by multiplying the deceleration by the engine brake and the braking hydraulic pressure applied to the braking device by a predetermined second coefficient larger than the first coefficient. If the snowfade elimination control is to be canceled when the value is less than or equal to the sum of the values, the time when the snowfade elimination control should be canceled is accurate regardless of whether the wheel is a non-driven wheel or a driven wheel. Therefore, the snow fade elimination control can be canceled.

  If the ABS operation start early control is executed during the execution of the snow fade elimination control as described above, the snow fade elimination control includes pressing the brake pad against the brake disc and separating the brake pad from the brake disc. Snowfade elimination by periodically repeating or temporarily increasing the servo gain of the braking device can be executed so as to maintain the running stability of the vehicle and not give the driver a sense of incongruity.

  Snow fade usually does not occur at the same time on all the wheels at the same time, but starts from one of the front, rear, left and right wheels. The occurrence of snow fade can be estimated or detected only after the wheels are braked, so that snow fade has occurred on two or more wheels while the vehicle is operating without being braked for a while. From the point of view of eliminating the snow fade, the snow fade elimination control only needs to be performed for any one of the wheels where the snow fade has occurred. In some cases, running stability may be impaired. As described above, since the snow fade elimination control is to periodically press the brake pad against the brake disc and to separate the brake pad from the brake disc, or to temporarily increase the servo gain of the braking device, There is no problem even if snow fade elimination control is performed in a braking device in which no fade has occurred. Therefore, when it is estimated that a snow fade has occurred on one of the left and right front wheels, it is estimated that snow fade cancellation control is performed on the left and right front wheels, and that a snow fade has occurred on one of the left and right rear wheels. When this is done, if the snow fade elimination control is performed on the left and right rear wheels, it is possible to prevent the running stability from being impaired by the snow fade elimination control.

  FIG. 1 is a hydraulic circuit diagram showing an example in which the vehicle braking device according to the present invention is implemented as a hydraulic braking device. However, since the present invention has the gist of the software configuration relating to the operation of the braking device of the vehicle, the hardware configuration itself shown in FIG. 1 is known. The braking device generally indicated at 10 has a master cylinder 14 that pumps brake oil in response to a depression operation of the brake pedal 12 by the driver. A dry stroke simulator 16 is provided between the brake pedal 12 and the master cylinder 14.

  The master cylinder 14 has a first master cylinder chamber 14A and a second master cylinder chamber 14B. In these master cylinder chambers, one end of a hydraulic conduit 18A for the left front wheel and one end of a hydraulic conduit 18B for the right front wheel, respectively. It is connected. Wheel cylinders 20FL and 20FR for generating a braking force on the left front wheel and the right front wheel are connected to the other ends of the hydraulic conduits 18A and 18B, respectively.

  Normally open electromagnetic open / close valves (master cut valves) 22L and 22R are provided in the middle of the hydraulic conduits 18A and 18B, respectively. These electromagnetic on-off valves 22L and 22R function as shut-off valves that selectively block communication between the first master cylinder chamber 14A and the second master cylinder chamber 14B and the corresponding wheel cylinders 20FL and 20FR, respectively. A wet stroke simulator 26 is connected to a brake hydraulic pressure supply conduit 18A between the master cylinder 14 and the electromagnetic on-off valve 22FL via a normally-closed electromagnetic on-off valve 24.

  A reservoir 28 is connected to the master cylinder 14, and one end of an oil feeding conduit 30 is connected to the reservoir 28. An oil pump 34 driven by an electric motor 32 is connected to the oil feeding conduit 30, and an accumulator 38 for accumulating pressurized oil pressure is connected to a hydraulic pressure supply conduit 36 on the discharge side of the oil pump 34. One end of an oil return conduit 40 is connected to the oil supply conduit 30. The reservoir 28, the oil pump 34, the accumulator 38, etc. function as a hydraulic pressure source for increasing the pressure in the wheel cylinders 20FL, 20FR, 20RL, 20RR.

  Although not shown in FIG. 1, a conduit is provided to connect the oil supply conduit 30 on the suction side of the oil pump 34 and the hydraulic supply conduit 36 on the discharge side, and an accumulator 38 is provided in the middle of the conduit. When the pressure exceeds the reference value, there is provided a relief valve that opens and returns oil from the discharge-side hydraulic supply conduit 36 to the suction-side oil supply conduit 30.

  The hydraulic supply conduit 36 on the discharge side of the oil pump 34 is connected to the wheel cylinder 20FL via a normally closed electromagnetic on-off valve 42FL and a hydraulic conduit 44FL. Similarly, the hydraulic supply conduit 36 on the discharge side of the oil pump 34 is connected to the wheel cylinder 20FR via a normally closed electromagnetic on / off valve 42FR and a hydraulic conduit 44FR, and the normally closed electromagnetic on / off valve 42RL and the hydraulic conduit 44RL are connected. Then, it is connected to the wheel cylinder 20RL, and is connected to the wheel cylinder 20RR via a normally closed electromagnetic on-off valve 42RR and a hydraulic conduit 44RR.

  The wheel cylinders 20FL, 20FR, 20RL, and 20RR are also connected to the oil return conduit 40 through hydraulic conduits 44FL, 44FR, 44RL, and 44RR and normally closed solenoid valves 46FL, 46FR, 46RL, and 46RR, respectively.

  The electromagnetic on-off valves 42FL, 42FR, 42RL, and 42RR function as pressure-increasing valves (or hydraulic holding valves) for the wheel cylinders 20FL, 20FR, 20RL, and 20RR, respectively. The electromagnetic on-off valves 46FL, 46FR, 46RL, and 46RR are respectively wheel cylinders 20FL, It functions as a pressure reducing valve (or hydraulic pressure holding valve) for 20FR, 20RL, and 20RR. Therefore, these electromagnetic on-off valves cooperate with each other to individually supply the hydraulic pressure supplied to each wheel cylinder based on the hydraulic power source in the accumulator 38. Increase / decrease can be controlled.

  The normally open type electromagnetic open / close valves 22L and 22R are maintained in the open state in the non-control mode in which no drive current is supplied, and the normally closed type electromagnetic open / close valves 42FL, 42FR, 42RL, 42RR and 46FL, 46FR, 46RL, 46RR are maintained. Is kept in the closed state in the non-control mode in which no drive current is supplied. If any of the solenoid valves 42FL, 42FR, 42RL, 42RR and 46FL, 46FR, 46RL, 46RR breaks down and the pressure in the corresponding wheel cylinder cannot be controlled normally, these solenoid valves The non-control mode is set, whereby the pressure in the wheel cylinders of the left and right front wheels is directly controlled by the master cylinder 14.

  The hydraulic conduit 18A between the first master cylinder chamber 14A and the electromagnetic on-off valve 22L is provided with a first hydraulic sensor 48A that detects the pressure in the hydraulic conduit as the first master cylinder pressure. Similarly, a second hydraulic sensor 48B for detecting the pressure in the hydraulic conduit as a second master cylinder pressure is provided in the hydraulic conduit 18B between the second master cylinder chamber 14B and the electromagnetic on-off valve 22R. . The brake pedal 12 is provided with a stroke sensor 50 for detecting the depression stroke of the brake pedal by the driver. The hydraulic pressure supply conduit 36 on the discharge side of the oil pump 34 is provided with a hydraulic pressure sensor 52 that detects the pressure in the conduit as an accumulator pressure. Pressures in the wheel cylinders 20FL, 20FR, 20RL, and 20RR are detected as pressures Pbi (i = fl, fr, rl, rr) by hydraulic pressure sensors 54FL, 54FR, 54RL, and 54RR, respectively. The rotational speed of each wheel is detected as Vwi (i = fl, fr, rl, rr) by wheel speed sensors 56FL, 56FR, 56RL, 56RR, respectively.

  The electromagnetic on / off valves 22L and 22R, the electromagnetic on / off valve 24, the electric motor 32, the electromagnetic on / off valves 42FL to 42RR, and the electromagnetic on / off valves 46FL to 46RR are controlled by an electronic control unit 58. The electronic control unit 58 includes a microcomputer 60 and a drive circuit 62. The microcomputer 60 includes a signal indicating the outside air temperature from the outside air temperature sensor, a signal indicating the vehicle speed from the vehicle speed sensor, a signal indicating the first and second master cylinder pressures from the hydraulic pressure sensors 48A and 48B, and a brake pedal from the stroke sensor 50, respectively. 12, a signal indicating the depression stroke, a signal indicating the accumulator pressure from the hydraulic sensor 52, a signal indicating the pressure Pbi (i = fl, fr, rl, rr) in the wheel cylinders 20FL to 20RR from the hydraulic sensors 54FL to 54RR, and the wheels A signal indicating the rotational speed Vwi (i = fl, fr, rl, rr) of each wheel is input from the speed sensors 56FL, 56FR, 56RL, 56RR.

  The microcomputer 60 stores a braking control routine. When the brake pedal 12 is depressed, the microcomputer 60 opens the electromagnetic on-off valve 24 and closes the electromagnetic on-off valves 22L and 22R. In this state, the hydraulic sensor 48A, Calculate the required braking force based on the master cylinder pressures Pma and Pmb detected by 48B and the depression stroke detected by the stroke sensor 50, and calculate the distribution ratio to distribute it to the front, rear, left and right wheels, The target wheel cylinder pressure Pbti (i = fl, fr, rl, rr) for each of the cylinders 20FL to 20RR is calculated, and the pressure Pbi (i = fl, fr, rl, rr) of each wheel cylinder is calculated as the target wheel cylinder pressure Pti. The electromagnetic on-off valves 42FL to 42RR and 46FL to 46RR are controlled so as to become.

  The microcomputer 60 includes a signal indicating the yaw rate of the vehicle body from a yaw rate sensor (not shown), a signal indicating the longitudinal acceleration of the vehicle body from the longitudinal acceleration sensor, and a signal indicating the lateral acceleration of the vehicle body from the lateral acceleration sensor. The microcomputer 60 refers to these signals at the same time and performs vehicle driving support control in various control modes proposed in the field of vehicle driving control technology. Snow fade elimination control accompanied with ABS operation start early control according to the invention is performed.

  FIG. 2 is a flowchart showing the snow fade elimination control accompanied with the ABS operation start early control according to one embodiment of the present invention. The control according to the flowchart may be repeated at a cycle of several tens to several hundreds of milliseconds while the vehicle 60 is being driven by the microcomputer 60 between the execution of other vehicle travel support controls.

  When the control is started, first, in step (S) 10, the master cylinder pressure Pma (which may be the first master cylinder pressure or the second master cylinder pressure, or an average value thereof) is a predetermined pressure threshold value Pbo. It is determined whether or not this is the case. This is because the snow fade elimination control is executed only when the driver depresses the brake pedal to a certain depth or more and the braking device is substantially operated. Pbo is a threshold value for determining that the braking device is substantially operating. When the answer is yes (Y), control proceeds to step 20. If the answer is no (N), the control proceeds to step 270 described later, and if the snow fade elimination control and the ABS operation start early control are being executed, these are canceled and the flags Sf and Sr described later become 0. The control is reset and the control of this time is finished.

  In step 20, it is determined whether or not the outside air temperature Ta is a low temperature threshold at which a snow fade may occur in the braking device, for example, 0 degrees Celsius or less. When the answer is no, the snow fade elimination control is not necessary, and thus the control of this time is finished. Also at this time, the control proceeds to step 270.

  In step 30, it is determined whether or not the flag Sf is 1. The flag Sf is reset to 0 when the control is started due to the start of vehicle operation and when the control reaches Step 180 or 270 described later, and is set to 1 when the control reaches Step 60 described later. Until then, the answer is no. Therefore, control proceeds to step 40 first.

  In step 40, it is determined whether or not the deceleration δfl of the rotation of the left front wheel is smaller than a value Kfs · Pfl obtained by multiplying the braking hydraulic pressure Pfl of the left front wheel by a predetermined coefficient Kfs. Here, the deceleration is handled as a positive value, and when the friction coefficient between the brake disc and the brake pad decreases due to snow fade, the deceleration of the wheel becomes small (decreases). Now, assume that this vehicle is a rear-wheel drive vehicle, and the front wheels are non-drive wheels. This Kfs is a reduction in rotation to be generated on the left front wheel by the braking force by the braking hydraulic pressure Pfl if the friction coefficient between the brake disc and the brake pad for the left front wheel is a normal value when the braking hydraulic pressure of the left front wheel is Pfl. This is a coefficient for obtaining the lower limit value of the speed value. If the answer is yes, the coefficient of friction between the brake disc and the brake pad for the left front wheel is abnormally low, that is, an abnormality that occurs at low temperatures, and the braking device for the left front wheel It is estimated that a snow fade has occurred. When the answer is no, the control proceeds to step 50, but when the answer is yes, the control proceeds to step 60 and the flag Sf is set to 1.

Similarly, in step 50, it is determined whether or not the deceleration δfr of the rotation of the right front wheel, which is a non-driven wheel, is smaller than a value Kfs · Pfr obtained by multiplying the braking hydraulic pressure Pfr of the right front wheel by the coefficient Kfs. If the answer is yes, it is estimated that a snow fade has occurred in the braking device for the right front wheel. If the answer is no, control bypasses step 60, but if the answer is yes, control proceeds to step 60 and flag Sf is set to 1. Therefore, in this embodiment, the flag Sf is set to 1 if it is estimated that a snow fade has occurred in at least one of the left and right front wheels. Once control reaches step 60 and flag Sf is set to 1, steps 40 to 60 are bypassed thereafter.
Set to

  Control then proceeds to step 70 where it is determined whether the flag Sr is 1. The flag Sr is reset to 0 at the start of control by the start of vehicle operation and when the control reaches Step 260 or 270 described later, and is set to 1 when the control reaches Step 100 described later. Until then, the answer is no. Accordingly, control proceeds to step 80 first.

  In step 80, it is determined whether or not the deceleration δrl of the rotation of the left rear wheel is smaller than Kfs · Prl + Deb. As described above, it is assumed that this vehicle is a rear-wheel drive vehicle, and the engine brake acts on the rear wheel, which is the drive wheel, depending on the transmission switching state during braking of the vehicle. Deb is a value for taking into account the wheel deceleration due to engine braking estimated from the operating state of the engine and transmission, and the coefficient Krs is the deceleration ebrl of rotation of the left rear wheel and the deceleration Deb due to engine braking. This is a coefficient for estimating that a snow fade has occurred in the left rear wheel when it is equal to or less than the sum of the values obtained by multiplying the braking hydraulic pressure Prl applied to the device by the coefficient Krs. If the answer is no, the control proceeds to step 90. If the answer is yes, it is estimated that a snow fade has occurred in the braking device for the left rear wheel, and the control proceeds to step 100.

  In step 90, similarly, it is determined whether or not the deceleration δrr of the rotation of the right rear wheel is smaller than Krs · Prr + Deb. If the answer is no, the control bypasses step 100 and proceeds to the next step 110. If the answer is yes, it is estimated that a snow fade has occurred in the braking device for the left rear wheel, and the flag Sr is set to 1 in step 100. Once control reaches step 100 and flag Sr is set to 1, steps 80-100 are bypassed thereafter.

  In step 110, it is determined whether or not the flag Sf is 1. When control reaches step 60 after reaching step 60, the answer is yes, and control then proceeds to step 120.

  In step 120, it is determined whether or not the deceleration δfl of the rotation of the left front wheel is smaller than a value Kfe · Pfl obtained by multiplying the braking hydraulic pressure Pfl of the left front wheel by a predetermined coefficient Kfe. This coefficient Kfe is larger than the above coefficient Kfs, and the friction coefficient between the brake disc and the brake pad for the left front wheel, which is estimated to have snowfade, is eliminated by executing the snowfade elimination control. This is a coefficient for determining that the control has been recovered to a value that may be released. In step 130, it is determined whether or not the deceleration δfr of the rotation of the right front wheel is smaller than a value Kfe · Pfr obtained by multiplying the braking hydraulic pressure Pfr of the right front wheel by the coefficient Kfe.

  As described above, the control reaches step 120 because the flag Sf is set to 1. However, the flag Sf is set to 1 in step 60 because a snow fade has occurred on the left front wheel or the right Regardless of whether a snow fade has occurred on the front wheel, or even if a snow fade has occurred on both the left and right front wheels at that time, the flag Sf becomes 1, and control proceeds to step 120 for a while. If at least the answer to either step 120 or step 130 is yes, the control proceeds to step 140, during which snowfade elimination control is performed on the left and right front wheels, and during that time, control proceeds to step 150. The ABS operation start early control is executed for the left and right front wheels. As described above, the snow fade elimination control is performed by periodically repeating the pressing of the brake pad against the brake disk and the separation of the brake pad from the brake disk, or temporarily increasing the servo gain of the braking device. It may be done by combining both together in moderation. As described above, the ABS operation start early control is to lower the threshold of the slip ratio of the wheel that starts the operation of the ABS, or to shorten the threshold of the time during which the slip ratio of the wheel is below the predetermined threshold, Or you may carry out by combining these both moderately.

  Thus, when the snow fade elimination control is continued for a certain period of time, regardless of whether the snow fade has occurred on the left front wheel, the right front wheel, or both, the snow fade will eventually be canceled, and any of steps 120 and 130 will occur. The time comes when the answer is no. At this time, the control proceeds to step 160, where the snow fade elimination control for the left and right front wheel braking devices is released, and in the subsequent step 170, the ABS operation start early control for the left and right front wheel braking devices is also released. At this time, the flag Sf is reset to 0 in step 180.

  When it is estimated that a snow fade has occurred in at least one of the left rear wheel and the right rear wheel and the flag Sr is set to 1, the control proceeds to step 190. If the flags Sf and Sr are both set to 1 in steps 60 and 100 prior to this, the front wheel snow fade elimination control is executed and ended in steps 120 to 180, and then the control is performed. Proceed to step 190. If the answer to step 190 is yes, in step 200, the left rear wheel rotation deceleration δrl is obtained by multiplying the braking hydraulic pressure Prl of the left rear wheel by a predetermined coefficient Kre and the sum of Kre · Prl and Deb. It is determined whether or not it is small. The coefficient Kre is larger than the coefficient Krs, and the coefficient of friction between the brake disk and the brake pad for the left rear wheel, which is estimated to have snowfade, is determined by executing the snowfade elimination control. This is a coefficient for determining that the recovery control has been recovered to a value that may be canceled. In step 210, it is determined whether or not the deceleration δrr of the rotation of the right rear wheel is smaller than the sum of the value Kre · Prr obtained by multiplying the braking hydraulic pressure Prr of the right rear wheel by a coefficient Kre and Deb.

  As for the rear wheel, the flag Sr was set to 1 at step 100 so that the control could reach step 200 because the snow fade occurred on the left rear wheel or the snow fade occurred on the right rear wheel. In any case, or even if a snow fade has occurred on both the left and right rear wheels at that time, the flag Sr becomes 1, and the control proceeds to step 200. For a while, at least step 200 or step 210 If either answer is yes, control proceeds to step 220, during which snowfade elimination control is performed for both the left and right rear wheels, and during that time, control proceeds to step 230 for both left and right front wheels. The ABS operation start early control is executed.

  When the snow fade elimination control is continued for a certain time in this manner, even if the snow fade has occurred in either the left rear wheel, the right rear wheel, or both, the snow fade elimination will eventually cause the steps 200 and 210. When either answer is no, the control proceeds to step 240, where the snow fade elimination control for the left and right rear wheel braking devices is canceled, and in step 250, the left and right rear wheel braking devices are released. The ABS operation start early control for is also canceled. At this time, in step 260, the flag Sr is reset to zero.

  The driver does not depress the brake pedal at a depth greater than or equal to a predetermined threshold, or the driver releases the brake pedal even when the snow fade elimination control is being executed, or the outside air temperature is a braking device. The answer to step 10 or 20 is no when the temperature is not below the low temperature threshold that may cause snow fade or when the outside air temperature rises for some reason even during execution of the snow fade elimination control. When NO turns to NO, the control proceeds to step 270. If the snow fade elimination control and the ABS operation start early control are being executed, these controls are canceled and the flags Sf and Sr are set to 1. This is reset to zero.

  While the present invention has been described in detail with respect to one embodiment thereof, it will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention.

The hydraulic circuit diagram which shows an example at the time of implementing the brake device of the vehicle by this invention as a hydraulic brake device. The flowchart which shows the snow fade elimination control accompanying the ABS operation start early control by this invention about the one embodiment.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 10 ... Brake device, 12 ... Brake pedal, 14 ... Master cylinder, 16 ... Dry stroke simulator, 18A, 18B ... Hydraulic conduit, 20FL, 20FR, 20RL, 20RR ... Wheel cylinder, 22F, 22R ... Electromagnetic on-off valve (master cut valve) ), 24 ... Solenoid open / close valve, 26 ... Wet stroke simulator, 28 ... Reservoir, 30 ... Oil supply conduit, 32 ... Electric motor, 34 ... Oil pump, 36 ... Hydraulic supply conduit, 38 ... Accumulator, 40 ... Oil return conduit, 42FL , 42FR, 42RL, 42RR ... Electromagnetic on-off valve, 44FL, 44FR, 44RL, 44RR ... Hydraulic conduit, 46FL, 46FR, 46RL, 46RR ... Electromagnetic on-off valve, 48A, 48B ... Pressure sensors 48, 50 ... Stroke sensor, 52 ... Pressure Sensor, 54FL, 54FR, 54RL, 54RR ... Pressure sensor, 56FL, 56FR, 56RL, 5RR ... Wheel Sensor, 58 ... electronic control unit, 60 ... microcomputer, 62 ... drive circuit

Claims (11)

For vehicles that are designed to perform snowfade elimination control including cyclically repeating the pressing of the brake pad against the brake disc and the separation of the brake pad from the brake disc in response to the occurrence of snow fade in the braking device However, the vehicle is characterized in that during the execution of the snow fade elimination control, the ABS operation start early control is performed in which the condition for starting the ABS operation is relaxed to accelerate the start of the ABS operation. In a vehicle that performs snow fade elimination control including temporarily increasing the servo gain of the braking apparatus in response to occurrence of snow fade in the braking apparatus, during execution of the snow fade elimination control, A vehicle characterized by performing ABS operation start early control that loosens a condition for starting the operation of ABS and accelerates the start of operation of ABS.   3. The ABS operation start condition is that a wheel slip rate exceeds a predetermined slip rate threshold value, and the ABS operation start early control is to lower the slip rate threshold value. Vehicle.   The ABS operation start condition is that a wheel slip ratio exceeds a predetermined slip ratio threshold over a predetermined time, and the ABS operation start early control is to shorten the predetermined time. Or the vehicle according to 2.   The ABS operation start condition is that the wheel slip ratio exceeds a predetermined slip ratio threshold over a predetermined time, and the ABS operation start early control is to lower the slip ratio threshold and shorten the predetermined time. The vehicle according to claim 1, wherein:   When the outside air temperature is equal to or lower than a predetermined temperature and the deceleration of rotation of the non-driven wheel is equal to or lower than a value obtained by multiplying the braking hydraulic pressure applied to the braking device by a predetermined first coefficient, a snow fade has occurred on the wheel. The vehicle according to any one of claims 1 to 5, wherein the snow fade elimination control is performed by estimation.   When the outside air temperature is below a predetermined temperature and the rotation deceleration of the drive wheels is below the sum of the deceleration by the engine brake and the braking hydraulic pressure applied to the braking device multiplied by a predetermined first coefficient The vehicle according to any one of claims 1 to 5, wherein the snow fade elimination control is performed by estimating that a snow fade has occurred on a wheel.   When the deceleration of the rotation of the non-driving wheels for which the snow fade elimination control is being executed is not less than the value obtained by multiplying the braking hydraulic pressure applied to the braking device by a predetermined second coefficient larger than the first coefficient. The vehicle according to claim 6, wherein the snow fade elimination control is released.   A value obtained by multiplying the deceleration by the engine brake and the braking hydraulic pressure applied to the braking device by a predetermined second coefficient larger than the first coefficient for the deceleration of the rotation of the driving wheel for which the snow fade elimination control is executed The vehicle according to claim 7, wherein the snowfade elimination control is canceled when the sum is not less than or equal to.   The snowfade elimination control is performed on the left and right front wheels when it is estimated that snowfade has occurred on either one of the left and right front wheels. The listed vehicle.   10. The snow fade elimination control is performed on the left and right rear wheels when it is estimated that a snow fade has occurred on either one of the left and right rear wheels. The vehicle described in Crab.

Images