JP2007237909A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device for a vehicle capable of reducing the creep groan even if the vehicle has such a structure that a brake mechanism is operated through a hydraulic pipe having a large length. <P>SOLUTION: In controlling hydraulically the operation of brake devices to give braking forces to the wheels of the vehicle equipped with a torque converter in its drive system, the oil pressure is reduced on the spot basis so that the operation goes out of the vehicle speed region where creep groan is generated, and at the same time, the return speed when the oil pressure is to be returned to the prescribed oil pressure, is set in accordance with the resonance period of the hydraulic piping line of the brake system, or following the first reduction of the oil pressure, a second reduction is executed on the basis of the resonance period. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle brake control device, and more particularly to a brake control device used in a vehicle having a drive system with a torque converter.

  In a vehicle equipped with an automatic transmission using a torque converter, if the brake pedal is released from a state where it has been stopped by a brake operation and a start operation is performed, a stick slip occurs between the brake pad and the friction surface in a certain speed range. A phenomenon occurs, which causes a resonance sound. This resonance sound = abnormal noise is called creep creep. Such creep glones are not only uncomfortable for the driver / occupant, but also cause a decrease in the durability of the brake pads. A technique disclosed in Patent Document 1 is known as a technique for suppressing creep creep.

In Patent Document 1, as a countermeasure for creep creep, in the process of reducing the brake pressure, the brake pressure decreases from the first predetermined brake pressure until it reaches a second predetermined brake pressure lower than the first predetermined brake pressure. A technique for pulsatingly reducing the brake pressure is described.
Japanese Patent Laid-Open No. 2000-21493

  However, this technology does not always suffice for creep creep suppression. This is because the vehicle speed region where the stick-slip phenomenon occurs can vary depending on the brake configuration and its secular change. If the second predetermined brake pressure is set lower while increasing the first predetermined brake pressure in consideration of this, the time for pulsing the brake pressure becomes longer. When the pulsation becomes longer in this manner, the pulsation also occurs in the acceleration of the vehicle, and the pulsation becomes longer, so that the passenger feels uncomfortable.

  In view of such a problem, the inventor disclosed in Japanese Patent Application No. 2005-301933 that the hydraulic pressure is reduced in a single manner so as to deviate from the vehicle speed region where creep creep occurs (see FIG. 2), and the vehicle speed at which creep growth occurs. We proposed a technique to suppress the generation of abnormal noise by shortening the residence time of the area.

  However, according to the knowledge of the inventors, it has been found that the above technique may not be sufficient for braking control in an actual vehicle. In an actual vehicle, a brake mechanism arranged on wheels and a pressure actuator that applies hydraulic pressure to these are usually arranged at a distance and connected by hydraulic piping. For this reason, even if the hydraulic pressure applied in the pressurizing actuator is reduced once, the time waveform of the hydraulic pressure acting on the brake mechanism through the hydraulic piping is different from the time waveform in the pressurizing actuator (see FIG. 3).

  Therefore, an object of the present invention is to provide a braking control device that can reduce creep glones even in a vehicle that operates a brake mechanism through a long hydraulic pipe.

  In order to solve the above problems, a braking control device according to the present invention detects a vehicle speed in a braking control device that controls hydraulically the operation of a braking device that applies a braking force to each wheel of a vehicle including a torque converter in a drive system. Vehicle speed detecting means, and the first hydraulic pressure reduction is performed in a single manner so as to deviate from the vehicle speed region where creep glones are generated based on the vehicle speed, and then the first hydraulic pressure reduction amount and the hydraulic piping system of the braking system And a hydraulic pressure control means for performing a second single-time hydraulic pressure reduction according to the damping coefficient.

  When the piping system has a length that cannot be ignored, since the resonance point is provided, a resonance phenomenon occurs due to pressurization by the actuator, so that the hydraulic pressure acting on the brake mechanism changes. In the present invention, immediately after the first oil pressure reduction, the oil pressure acting on the brake mechanism is reduced by executing the second oil pressure reduction that cancels the oil pressure change due to the resonance generated in the piping system due to the oil pressure reduction. Adjust to the desired waveform to achieve one-time oil pressure reduction.

  Alternatively, the hydraulic pressure control means of the braking control device according to the present invention reduces the hydraulic pressure on a one-off basis so as to deviate from the vehicle speed region where creep glones are generated based on the vehicle speed detected by the vehicle speed detection means, and The return speed when returning to the hydraulic pressure may be set according to the resonance period of the hydraulic piping system of the braking system.

  If the cycle for returning the hydraulic pressure when changing the hydraulic pressure is too early with respect to the resonance cycle, the single hydraulic pressure increase on the brake mechanism side due to resonance after the single hydraulic pressure fluctuation on the pressurizing actuator side ends Will occur. By setting the return speed for returning the hydraulic pressure in accordance with the resonance period of the hydraulic piping system, the occurrence of resonance is suppressed, and a single reduction in hydraulic pressure on the brake mechanism side is realized.

  This hydraulic pressure control means sets the return time when returning the hydraulic pressure to a time exceeding a quarter of the resonance period, or decreases the return speed of the final stage when returning the hydraulic pressure according to the resonance period, It is good to lower. Thereby, generation | occurrence | production of resonance is suppressed and the hydraulic pressure reduction on the brake mechanism side is implement | achieved.

  According to the present invention, the resonance that can occur in the first hydraulic pressure reduction is canceled out by the second hydraulic pressure reduction by performing the single hydraulic pressure reduction twice continuously. For this reason, the hydraulic pressure acting on the brake mechanism side can be reduced once, and the braking force can be reduced once. By reducing the braking force in a single manner in this way, it is possible to instantaneously pass through the vehicle speed region where creep glones are generated when starting, and to reduce abnormal noise.

  Alternatively, by adjusting the return speed and time according to the resonance period, it is possible to suppress the occurrence of resonance after returning the hydraulic pressure, and to reduce the hydraulic pressure acting on the brake mechanism in a single shot. It is possible to instantaneously pass the vehicle speed region where the glones are generated, and to reduce abnormal noise.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

  FIG. 1 is a block diagram showing a configuration of a braking system / driving system of a vehicle including a braking control device according to the present invention. Here, the case of a vehicle having either two driving wheels 40 and two driven wheels 41 (either front wheel driving or rear wheel driving) will be described as an example, but the present invention is also applied to a four wheel driving vehicle. Applicable.

  The output of the engine 50 such as a gasoline engine or a diesel engine is transmitted to the automatic transmission 52 via the torque converter 51 to drive the drive wheels 40. Thus, a drive system is configured. In the braking system, the disc brake 20 is disposed on each of the driving wheel 40 and the driven wheel 41, and an electronic control type that adjusts the operation of the brake actuator 11 that adjusts the hydraulic pressure supplied to the wheel cylinder 21 by the brake ECU 10. It is a braking system. The brake ECU 10 receives the operation amount of the master cylinder 12 operated by the brake pedal 13 and the outputs of the wheel speed sensors 30 arranged on the drive wheels 40 and the driven wheels 41, respectively. Note that the output hydraulic pressure of the master cylinder 12 is inputted to the brake actuator 11 so that the hydraulic pressure can be directly applied to the wheel cylinder 21. When the electronic control system fails, the output pressure of the brake pedal 13 can be reduced. The braking force according to this can be applied to the driving wheel 40 and the driven wheel 41.

  In the present embodiment, as described above, the start control is performed with reduced creep glones. When the start control is not performed, as shown in FIG. 2A, the transmission 52 is set to the travel range, and the brake pedal 13 is set for the start operation from the state where the driver steps on the brake pedal 13. When the treading force is relaxed, the hydraulic pressure supplied from the brake actuator 11 to the wheel cylinder 21 of each disc brake 20 decreases. The hydraulic diagram shown in FIG. 2A is the hydraulic pressure in the wheel cylinder 21. As a result, the braking force applied to the driving wheel 40 and the driven wheel 41 also decreases with time. When the driving force applied to the driving wheels 40 exceeds the braking force and frictional force, the vehicle starts to move, the vehicle speed increases, and the vehicle starts. At this time, the above-described stick-slip phenomenon occurs in a certain vehicle speed range, and a creep glone due to this phenomenon occurs.

  If the hydraulic pressure acting on the wheel cylinder 21 is reduced for a short time as shown in FIG. 2 (b) when the vehicle speed reaches the vehicle speed range during this starting operation, the drive wheels 40, Since the braking force acting on the driven wheel 41 is also reduced, the acceleration of the vehicle is increased and the vehicle speed range is passed in a short time. Thereby, the continuation of the stick-slip phenomenon is suppressed, and the creep glon is reduced. This technology has been filed as Japanese Patent Application No. 2005-301933 described above.

  By the way, in an actual vehicle, the hydraulic pressure supplied to each wheel cylinder 21 is adjusted by a brake actuator 11 connected thereto by piping of several tens of centimeters to several meters. Since a certain amount of brake oil exists in these pipes, the hydraulic pressure output in the wheel cylinder 21 can be influenced by these pipes in addition to the input to the brake actuator 11. In normal brake control including vehicle behavior control, the hydraulic pressure is changed over the driver's brake operation or in the same time span, so the influence of piping is negligible.

  However, since the one-time decrease in hydraulic pressure changes in a pulsed manner in an extremely short time of 0.1 seconds or less, preferably about 0.05 seconds, it is possible that the influence of piping becomes obvious after the filing of the application. It became clear by examination of inventors. FIG. 3 is a diagram schematically showing time waveforms of the input to the actual brake actuator 11 and the pressure supplied to the wheel cylinder 21 thereby.

As shown in FIG. 3, when the brake actuator 11 is instructed to perform a single hydraulic pressure decrease of Δt ₁ (for example, about 0.05 seconds), the hydraulic pressure of the wheel cylinder 21 is temporarily changed in the same manner. Depressurized. After this, ideally, the pressure increases linearly, and once the original pressure is reached, it is desired to maintain that pressure as shown by the dashed line. However, due to the influence of the piping, the behavior when returning the pressure is different from this, and after reaching a pressure exceeding the original pressure (peak pressure), it starts to decrease. After that, it is stabilized at the original pressure after dropping to the vicinity of the original pressure. When the natural frequency of the pipe = resonance frequency is f, Δt ₁ is approximately 1 / 2f, more precisely, when the pressure return time Δt _R is 1 / 4f or less, the hydraulic pressure in the pipe resonates, It was found that a pressure increase pulse due to resonance was generated in the oil pressure change waveform.

  In the present embodiment, the brake actuator 11 is controlled so as to reduce the hydraulic pressure applied to the wheel cylinder 21 as shown in FIG. 2B. FIG. 4 shows a flowchart of the braking control process. This process is performed by the brake ECU 10.

  First, each sensor value is read (step S1). This sensor value includes the output of a hydraulic sensor installed in the brake actuator 11, the wheel cylinder 21, and the master cylinder 12 in addition to the wheel speed that is the output value of the wheel speed sensor 30. Next, the vehicle speed V is calculated from the output value of the wheel speed sensor 30 (step S3). For example, the vehicle speed may be calculated based on the average value of all the wheel speed sensors 30 or the average value of the wheel speed sensors 30 of the driven wheels 41.

  Next, the obtained vehicle speed V is compared with the first threshold value Vth1 (step S5). This Vth1 is set to a lower limit speed at which the stick-slip phenomenon occurs or a speed slightly lower than that. If V is equal to or lower than Vth1, the process proceeds to step S21, where 1 is set in FlagS and 0 is set in FlagD, and the process ends. If V exceeds Vth1, the vehicle speed V is further compared with the second threshold value Vth2 (step S7). This Vth2 is set to an upper limit speed at which a stick-slip phenomenon occurs or a speed slightly faster than that. If V is equal to or greater than Vth2, the process proceeds to step S23 where 0 is set in FlagS and the process is terminated.

  If V is less than Vth2 (and exceeds Vth1), the process proceeds to step S9, where the master cylinder pressure Pm is compared with the pressure threshold value Pth. When Pm is equal to or less than Pth, it is determined that the brake hydraulic pressure has already been sufficiently reduced, and the subsequent processing is skipped and the process ends. If Pm is smaller than Pth, the value of FlagS is further determined (step S11).

  FlagS is set to 1 in step S21 and 0 in step S23. That is, in step S11, the flag S is determined to be 1 when V has increased from a speed smaller than Vth1 and has not yet reached Vth2, and the hydraulic pressure reduction operation has not been completed as will be described later. Only if. If it is determined as 0, it is considered that the start control is not being performed but the stop control is being performed, and therefore it is considered that there is little possibility of the occurrence of creep glones, so the subsequent processing is skipped and the processing is terminated. .

  On the other hand, when FlagS is 1, since it is considered that the start control is being performed as described above, the process proceeds to step S13, and the value of FlagD is determined. FlagD is a flag for determining whether or not the hydraulic pressure reduction operation has started. Only when the flag D is 0, the process proceeds to step S15, the time t at that time is stored in the variable tstart, and FlagD is set to 1. .

  After Step S15 is completed, or when FlagD is determined to be 1 in Step S13, the process proceeds to Step S17. In step S17, the command hydraulic pressure to the brake actuator 11 is set. Here, the pressure Pt to Pt determined from the operation amount of the brake pedal 13 and the like and the function value f (Pt, t-tstart) set by the elapsed time (t-tstart) from the pressure reduction start time tstart are set. The pressure reduced by the pressure is set as an instruction hydraulic pressure Pt to the brake actuator 11.

  After the setting, the elapsed time (t-tstart) from the start of decompression is compared with the threshold value tth (step S19). The threshold tth is set to a time required for decompression. If (t-tstart) is shorter than tth, the process is terminated as it is, and if it is the same or longer, the process proceeds to step S23, where FlagS is set to 0, and the process is terminated.

With the above control, control is performed to reduce the hydraulic pressure for a short time when passing through a speed region where stick-slip phenomenon is likely to occur when starting. Here, a specific example of the pressure waveform set in step S17 described above will be described. In the example shown in FIG. 5, the time Δt _R2 required to return the pressure is set to be ¼f or more by slowing the return speed at the time of pressure return. Thus, the occurrence of resonance can be suppressed by setting the time required for returning the pressure after decompression to be long according to the resonance period. As a result, it is possible to obtain a hydraulic pressure waveform that substantially matches the input waveform to the brake actuator 11 in the wheel cylinder 21, and as a result, it is possible to surely reduce creep glones.

When the natural frequency of the piping system is small, that is, when the vibration period is long, Δt _R2 that satisfies the above condition becomes long. In this case, since the duration of the creep glon also becomes long, it is not preferable. Therefore, in the example illustrated in FIG. 6, the brake actuator 11 continuously performs the second single-time hydraulic pressure reduction (reduction) immediately after performing the _first single-time hydraulic pressure reduction (reduction amount ΔP ₁ ). The quantity ΔP ₂ ) is executed. Reduction amount [Delta] P ₂ at this time is multiplied by the attenuation coefficient of the pipeline to a first reduction amount Delta] P1. On the other hand, the reduction time Δt ₄ is determined by Δt ₃ and the natural frequency of the piping system. Note that Δt ₃ is preferably a short time shorter than ½f. In this case, the resonance that is to occur after the first single-time oil pressure reduction is canceled by the second oil pressure reduction. Therefore, in the wheel cylinder 21, only the first hydraulic pressure reduction is executed, the second hydraulic pressure reduction does not occur, and the original hydraulic pressure is maintained. For this reason, it is possible to reduce the oil pressure for an extremely short time, and to reduce the creep glone.

Furthermore, as shown in FIGS. 7 and 8, only the waveform near the end point of the pressure return operation may be changed. In the example shown in FIG. 7, the return speed ΔP ₄ / Δt ₆ in the later stage of the pressure return operation is made slower than the return speed (ΔP ₃ −ΔP ₄ ) / Δt ₅ in the previous period of the pressure return operation. Even if the late speed is slowed down and the pressure is slowly returned, a drop similar to that shown in FIG. 5 can be obtained. In this case, the latter pressure return speed may be the same pressure return speed as that shown in FIG. 5, and the time required for the one-time oil pressure reduction (including return) should be shorter than that shown in FIG. Can do. Further, since it is not necessary to change the pressure continuously in a short time, the load on the brake actuator 11 is reduced as compared with the case shown in FIG.

  Here, the pressure return speed is changed in two stages, but it may be changed in three stages or more stages. In that case, it is preferable that the return speed is slower in the later stage than in the previous stage (the speed is lowered with the elapsed time). If the pressure is further changed steplessly, the pressure changes as shown in FIG. Even in this case, the same effect as in the case of FIGS. 5 and 7 can be obtained.

  In the examples shown in FIGS. 5, 7, and 8, the case where the oil pressure before and after the single oil pressure reduction is the same is described as an example. That is, the pressure return operation here refers to an operation to return to the hydraulic pressure immediately before the single hydraulic pressure reduction. However, the pressure return operation is not limited to the operation to return to the hydraulic pressure immediately before the single hydraulic pressure reduction. For example, when a single oil pressure reduction is performed while the oil pressure is being changed (usually during the oil pressure reduction operation), the amount of change in the oil pressure is detected immediately before the change. The case where the oil pressure is restored to the estimated oil pressure when the oil pressure is not reduced properly corresponds to the pressure return operation. Alternatively, it may be a hydraulic pressure value determined by the brake ECU 10 based on a driver's brake pedal operation amount or the like. Thus, the hydraulic pressure after returning pressure is not necessarily limited to the hydraulic pressure immediately before the single hydraulic pressure reduction, and may be a predetermined hydraulic pressure value determined by various conditions.

  In addition, about the time of pressure reduction, it is good to carry out as fast as possible with the brake actuator 11. Here, after the pressure is reduced, the pressure is maintained for a certain period of time, but the length thereof is appropriately set so as to be out of the speed region where the creep grains are generated. The duration of the single pressure reduction actually generated by the wheel cylinder 21 is preferably about several milliseconds to several tens of milliseconds. This is because if the duration exceeds this, the driver / occupant may feel uncomfortable.

It is a block diagram which shows the structure of the braking system and drive system of a vehicle provided with the braking control apparatus concerning this invention. It is a figure which compares and shows the control result which a prior art and this invention aim. It is a figure which shows an actuator input and the wheel cylinder oil pressure implement | achieved by this. It is a flowchart of the braking control process in the apparatus of FIG. It is a figure which shows an example of the braking force control in this invention. It is a figure which shows another example of the braking force control in this invention. It is a figure which shows another example of the braking force control in this invention. It is a figure which shows another example of the braking force control in this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Brake ECU, 11 ... Brake actuator, 12 ... Master cylinder, 13 ... Brake pedal, 20 ... Disc brake, 21 ... Wheel cylinder, 30 ... Wheel speed sensor, 40 ... Drive wheel, 41 ... Drive wheel, 50 ... Engine, 51 ... Torque converter, 52 ... Transmission.

Claims (5)

In a braking control device that controls hydraulically the operation of a braking device that applies a braking force to each wheel of a vehicle including a torque converter in a drive system,
Vehicle speed detection means for detecting the vehicle speed;
Based on the vehicle speed, the first hydraulic pressure reduction is performed on a one-time basis so as to deviate from the vehicle speed range where creep glones are generated, and subsequently, according to the first hydraulic pressure reduction amount and the damping coefficient of the hydraulic piping system of the braking system Hydraulic control means for performing the second single-time hydraulic pressure reduction;
A braking control device comprising: In a braking control device that controls hydraulically the operation of a braking device that applies a braking force to each wheel of a vehicle including a torque converter in a drive system,
Vehicle speed detection means for detecting the vehicle speed;
Based on the vehicle speed, the hydraulic pressure is reduced in a single shot so as to deviate from the vehicle speed region where creep creep occurs, and the return speed when returning the hydraulic pressure to a predetermined hydraulic pressure depends on the resonance period of the hydraulic piping system of the braking system Hydraulic control means to set;
A braking control device comprising:   3. The braking control device according to claim 2, wherein the hydraulic pressure control means sets a return time for returning the hydraulic pressure to a time exceeding a quarter of the resonance period.   The braking control device according to claim 2, wherein the hydraulic control means reduces the return speed of the final stage when the hydraulic pressure is returned in accordance with the resonance period.   3. The braking control device according to claim 2, wherein the hydraulic control means reduces the return speed of the final stage when returning the hydraulic pressure with time.

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