JP2010215202A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device performing snow fade countermeasure before starting. <P>SOLUTION: The brake control device includes a clearance estimation means estimating the clearance between a rotor rotating with a wheel and a pad generating a braking force by being pressed against the rotor, and a snow fade detection means detecting the snow fade based on the clearance estimated by the clearance estimation means. By estimating the clearance and detecting the snow fade, accurate detection of the snow fade becomes possible, and the snow fade is eliminated securely. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a brake control device that controls a brake of a vehicle.

  In cold regions, when running on a snowy road, snow or water enters the tire house and freezes on the brake pad or rotor surface, causing a phenomenon called snow fade, where the friction coefficient of the pad is greatly reduced. Happens. Conventionally, as a brake control device for such a snow fade, a friction coefficient is estimated from the wheel cylinder hydraulic pressure and the wheel deceleration, a snow fade is detected based on the friction coefficient, and a pad by increasing the wheel cylinder hydraulic pressure is detected. There is known one that can be eliminated by dragging (see, for example, Patent Document 1).

JP 2007-191010 A

  However, in such a brake control device, it is possible to detect and eliminate a snow fade only when the brake is stepped on while traveling, so there is a problem that the response of the brake may be delayed. It was. Moreover, since it is necessary to attach a non-contact temperature sensor to each wheel, there existed a problem that cost became high. Furthermore, there is a possibility that a normal brake fade is detected as a snow fade, and there is a problem that it is difficult to take a measure specific to snow fade.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a brake control device capable of taking a snow fade countermeasure before starting.

  The brake control device according to the present invention includes a clearance estimation unit that estimates a clearance between a rotor that rotates together with a wheel and a pad that generates a braking force by pressing the rotor, and a clearance estimated by the clearance estimation unit. And a snow fade detecting means for detecting a snow fade based on the snow fade.

  By detecting the snow fade by estimating the clearance, it becomes possible to accurately detect the snow fade, and it is possible to take a snow fade countermeasure before starting.

  In the brake control device according to the present invention, it is preferable that the clearance estimating means estimates the clearance based on a brake fluid flow rate during braking. As a result, the clearance can be estimated without attaching additional components such as sensors, and the cost can be reduced.

  In the brake control device according to the present invention, the brake fluid flow rate is preferably determined based on the liquid level of the reservoir tank. As a result, the brake fluid flow rate can be determined without attaching additional components such as sensors, and the cost can be reduced.

  In the brake control device according to the present invention, it is preferable to perform automatic control in order to estimate the clearance. This makes it possible to automatically detect a snow fade without the driver's operation.

  In the brake control device according to the present invention, it is preferable that the clearance is estimated when the vehicle is stopped. It is possible to detect a snow fade before traveling, and it is possible to prevent traveling in a snow fade state.

  In the brake control device according to the present invention, it is preferable that the clearance is estimated when the engine is started. After parking for a long time, a snow fade is likely to occur when the engine is started, so that it is possible to prevent traveling in a snow fade state.

  In the brake control device according to the present invention, it is preferable to perform a snow fade elimination process for eliminating the snow fade when the snow fade detection unit determines that the snow fade has occurred. This eliminates the snow fade when the snow fade is determined, thereby preventing the vehicle from running in the snow fade state.

  In the brake control device according to the present invention, it is preferable that the snow fade elimination process is performed by striking a pad on the rotor by increasing or decreasing the braking pressure. Snowfade can be eliminated by hitting the rotor with a pad and breaking the ice.

  In the brake control device according to the present invention, it is preferable to perform the snow fade elimination process when the vehicle is stopped and the driver does not intend to start. When the snow fade elimination process is performed during traveling, the driver feels uncomfortable, and this discomfort can be prevented.

  In the brake control device according to the present invention, it is preferable that a warning is given to the driver when the snow fade detection means determines that the snow fade has occurred. As a result, the driver can recognize the snow fade.

  In the brake control device according to the present invention, the clearance is preferably estimated based on the previously estimated clearance value. Since the snow fade can be determined according to a change in clearance due to deterioration of the piston seal or the like, erroneous determination can be prevented.

  According to the present invention, it is possible to take measures against snow fade before starting.

It is a block block diagram which shows the structure of the brake control apparatus which concerns on embodiment of this invention. It is a flowchart which shows the control processing in the brake control apparatus which concerns on embodiment of this invention. It is a diagram used in order to estimate a brake fluid flow volume. It is a block block diagram which shows the structure of the brake control apparatus which concerns on the modification of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a brake control device according to the present invention will be described in detail with reference to the drawings.

  First, the configuration of the brake control device 1 according to the embodiment of the present invention will be described. FIG. 1 is a block configuration diagram showing a configuration of a brake control device 1 according to an embodiment of the present invention. The brake control device 1 has a function of detecting a snow fade before driving and taking a countermeasure in advance, and includes an ECU (Electronic Control Unit) 2, an M / C cut solenoid 11, a pressure-increasing pump motor 12, and a warning display. A portion 13 is provided.

  The M / C cut solenoid 11 is provided in the master cylinder, and has a function of blocking input from the driver based on a control signal from the ECU 2. The pressure-increasing pump motor 12 has a function of increasing the brake fluid pressure based on a control signal from the ECU 2 and pressing a brake pad against the rotor. The warning display unit 13 is configured by a warning lamp or the like attached in the vehicle, and has a function of giving a snow fade warning to the driver by lighting.

  The ECU 2 is an electronic control unit that controls the entire brake control device 1. The ECU 2 is mainly composed of a CPU, for example, and includes a ROM, a RAM, an input signal circuit, an output signal circuit, a power supply circuit, and the like. The ECU 2 includes a temperature acquisition unit 3, a shift acquisition unit 4, a hydraulic pressure acquisition unit 5, a fluid flow rate estimation unit 6, a clearance previous value storage unit 7, a clearance determination unit (clearance estimation unit, snow fade detection unit) 8, brake pressure increase A control unit 9 and a warning display control unit 10 are provided.

  The temperature acquisition unit 3 has a function of acquiring outside air temperature outside the vehicle from a temperature sensor or the like. The shift acquisition unit 4 has a function of acquiring a shift position. The temperature acquisition unit 3 and the shift acquisition unit 4 have a function of outputting the acquired information to the brake pressure increase control unit 9. Further, the hydraulic pressure acquisition unit 5 has a function of acquiring the brake hydraulic pressure. The hydraulic pressure acquisition unit 5 has a function of outputting to the fluid flow rate estimation unit 6.

  The fluid flow rate estimation unit 6 has a function of estimating the brake fluid flow rate based on the brake fluid pressure acquired by the fluid pressure acquisition unit 5. The fluid flow rate estimation unit 6 can estimate the brake fluid flow rate, for example, by drawing a map based on data acquired in advance. The fluid flow rate estimation unit 6 has a function of outputting the estimated brake fluid flow rate to the clearance determination unit 8.

  The previous clearance value storage unit 7 has a function of storing the previous measured value of the brake fluid flow rate for determining the clearance. Further, the previous clearance value storage unit 7 has a function of outputting the previous value stored in response to a request from the clearance determination unit 8.

  The clearance determination unit 8 has a function of estimating the brake pad clearance based on the brake fluid flow rate, and also has a function of detecting a snow fade based on the estimated clearance. Specifically, the clearance determination unit 8 has a function of determining whether or not a snow fade has occurred based on a decrease in clearance, and a function of determining whether or not the snow fade has been resolved. Yes. The clearance determination unit 8 performs the determination by comparing the brake fluid flow rate estimated by the fluid flow rate estimation unit 6 with the normal flow rate.

  The brake pressure increase control unit 9 increases the brake fluid pressure by outputting a control signal to the pressure increasing pump motor 12, and further has a function of measuring the time until the brake fluid pressure exceeds a predetermined constant. Have. Whether the brake pressure increase control unit 9 determines whether or not a snow fade occurs by comparing the outside air temperature acquired by the temperature acquisition unit 3 with a predetermined constant, and performs control according to the present embodiment. It has a function to determine whether or not. Further, the brake pressure increase control unit 9 acquires the shift position information from the shift acquisition unit 4 and determines whether or not the P range is maintained, thereby determining whether the driver has an intention to start. have.

  The warning display control unit 10 has a function of turning on a snow fade warning by outputting a control signal to the warning display unit 13. In addition, it has a function of transmitting the end of control to the driver by releasing the warning when the snow fade is resolved.

  Next, the operation of the brake control device 1 according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a flowchart showing a control process in the brake control device 1 according to the embodiment of the present invention. This process is a process executed in the ECU 2 when the vehicle engine is started.

  As shown in FIG. 2, the brake pressure increase control unit 9 of the brake control device 1 determines whether or not the outside air temperature acquired by the temperature acquisition unit 3 is below a predetermined constant K1. It is determined whether or not to perform control according to (Step S10). In the process of S10, it is determined that there is a possibility of snow fade when the outside air temperature is lower than K1, and it can be determined that there is no possibility of snow fade when the outside air temperature is K1 or higher. Further, the predetermined constant K1 can be set to 0 ° C., for example. If it is determined in S10 that the outside air temperature is equal to or higher than K1, the control process shown in FIG. 2 ends.

  On the other hand, when it is determined in S10 that the outside air temperature is lower than K1, the brake pressure increase control unit 9 increases the brake fluid pressure and until the brake fluid hydraulic pressure PBF exceeds a predetermined constant K2. Is measured (step S12). Specifically, the brake pressure increase control unit 9 outputs a control signal to the M / C cut solenoid 11 to block input from the driver, and then outputs a control signal to the pressure increase pump motor 12 to perform constant rotation. The brake fluid pressure is increased by exercising. Here, FIG. 3A is a diagram showing the relationship between the hydraulic pressure and time when the brake pad and the rotor are brought into contact with each other. The brake pressure increase control unit 9 is configured such that the brake pad contacts the rotor. Then, the time T1 until the brake fluid hydraulic pressure PBF acquired by the hydraulic pressure acquisition unit 5 rises as shown in FIG. 3A and exceeds a predetermined constant K2 is measured. The predetermined constant K2 is preferably set to a value that exceeds the fluid pressure until the pad and the rotor come into contact with each other and that the fluid pressure quickly exceeds after contact. At this time, it is preferable that the pressure-increasing pump motor 12 is slowly rotated within a range in which the operation by the driver does not enter, and the accuracy is improved by taking a long T1.

  Next, the fluid flow rate estimation unit 6 estimates the brake fluid flow rate FBF (step S14). Specifically, the fluid flow rate estimation unit 6 acquires data representing the relationship between the motor rotation speed and time as shown in FIG. 3B in advance, and based on this data and the time T1 measured in S12. By drawing the map, the brake fluid flow rate FBF that is proportional to the area A of the portion indicated by the hatched portion in FIG.

  Next, the clearance determination unit 8 determines whether or not the pad clearance has decreased due to snow fade (step S16). Specifically, by determining whether or not the brake fluid flow rate FBF estimated in S14 is smaller than a value obtained by subtracting a predetermined constant K3 from the normal brake fluid flow rate FBFO set in advance, it is determined by snowfade. It is determined whether the pad clearance has decreased. Here, the predetermined constant K3 is set as a detection margin so that snow fade can be sufficiently detected and variations can be absorbed in order to prevent erroneous detection. Further, when the value of the brake fluid flow rate FBF measured last time is stored in the clearance previous value storage unit 7, the characteristic change of the piston seal is also absorbed by changing the threshold value of K3 based on the previous value. It becomes possible to detect a snow fade with high accuracy. In S16, when it is determined that the brake fluid flow rate FBF is equal to or larger than a preset normal brake fluid flow rate FBFO minus a predetermined constant K3, the control process shown in FIG. 2 ends.

  On the other hand, if it is determined in S16 that the brake fluid flow rate FBF is less than the preset normal brake fluid flow rate FBFO minus a predetermined constant K3, the pad clearance is reduced by snow fade. The warning display control unit 10 outputs a control signal to the warning display unit 13 to light up the snow fade warning (step S18). This suppresses the driver from starting and reduces the uncomfortable feeling caused by the braking operation.

  Next, the brake pressure increase control unit 9 acquires shift position information from the shift acquisition unit 4 and determines whether or not the P range is maintained (step S20). In this process, it is determined whether or not the driver has the intention to start by determining whether or not the P range is released. If it is determined in S20 that the P range has been released, it is determined that the driver has an intention to start, control is stopped, and the process shown in FIG. 2 ends. At this time, the snow fade warning continues to be lit until it is confirmed that the snow fade has been canceled, thereby prompting the driver to pay attention. In cold regions where snow fade is likely to occur, the friction coefficient of the road surface often decreases, but if the driver performs an accelerator operation during brake operation by control, there is a possibility of slipping, which makes the driver feel uncomfortable. there is a possibility. Therefore, by stopping the control and giving only a warning as described above, it is possible to drive safely and without feeling uncomfortable for the driver.

  On the other hand, if it is determined in S20 that the P range is maintained, the brake pressure increase control unit 9 performs a snow fade elimination process by increasing the brake fluid pressure (step S22). In this process, de-icing is performed by striking the rotor and pads to eliminate snow fade. Next, the clearance determination unit 8 determines whether or not the snow fade has been eliminated (step S24). Specifically, it is determined whether or not the snow fade is eliminated by determining whether or not the brake fluid flow rate FBF exceeds a value obtained by subtracting a predetermined constant K4 from the normal brake fluid flow rate FBFO. At this time, by setting the detection margin constant K4 to be smaller than the constant K3, it is possible to reliably determine whether the snow fade is eliminated. If it is determined in S24 that the snow fade has not been eliminated, the process proceeds to S20, and the processes in S20 to S24 are repeated again. On the other hand, if it is determined in S24 that the snow fade has been eliminated, the warning display control unit 10 outputs a control signal to the warning display unit 13 to cancel the snow fade warning, and control is thereby performed. The end is transmitted to the driver (step S26).

  As described above, according to the brake control device 1 according to the present embodiment, by detecting the snow fade by estimating the clearance, it is possible to accurately detect the snow fade and reliably eliminate the snow fade. Can do.

  Further, in the brake control device 1 according to the present embodiment, the clearance determination unit 8 estimates the clearance based on the brake fluid flow rate at the time of braking, and therefore can estimate the clearance without attaching additional components such as a sensor. Thus, the cost can be reduced.

  Further, in the brake control device 1 according to the present embodiment, since the pressure is increased by performing automatic control in order to estimate the clearance, it is possible to automatically detect a snow fade without a driver's operation. .

  Further, in the brake control device 1 according to the present embodiment, since the clearance is estimated when the vehicle is stopped, it is possible to detect a snow fade before traveling and to prevent traveling in a snow fade state. Can do.

  Further, in the brake control device 1 according to the present embodiment, the clearance is estimated when the engine is started. After parking for a long time, a snow fade is likely to occur when the engine is started, so that it is possible to prevent traveling in a snow fade state.

  Further, in the brake control device 1 according to the present embodiment, when it is determined that the snow fade is determined by the clearance determination unit 8, since the snow fade elimination processing for eliminating the snow fade is performed, the vehicle travels in the snow fade state. Can be prevented.

  In the brake control device 1 according to the present embodiment, the snow fade elimination process is performed by striking a pad on the rotor by increasing or decreasing the braking pressure. Snowfade can be eliminated by hitting the rotor with a pad and breaking the ice.

  In the brake control device 1 according to the present embodiment, the snow fade elimination process is performed when the vehicle is stopped and the driver does not intend to start. When the snow fade elimination process is performed during traveling, the driver feels uncomfortable, and this discomfort can be prevented.

  Further, in the brake control device 1 according to the present embodiment, when the snow judgment is determined by the clearance determination unit 8, the driver can be made aware of the snow fade by giving a warning to the driver.

  Further, in the brake control device 1 according to the present embodiment, the clearance is estimated based on the previously estimated clearance value. Since the snow fade can be determined according to a change in clearance due to deterioration of the piston seal or the like, erroneous determination can be prevented.

  The present invention is not limited to the above-described embodiment.

  For example, even if there is no automatic brake mechanism, since it is required to step on the brake when starting the engine in a general vehicle, the brake control device 100 using this operation may be provided. FIG. 4 is a block configuration diagram showing the configuration of the brake control device 100 according to a modification of the present invention. The brake control device 1 has a function of estimating the pad clearance from the brake fluid flow rate when the driver depresses the brake and performing only a snow fade warning to the driver. As shown in FIG. A display unit 13 is provided. The ECU 102 includes a liquid level height acquisition unit 111, a fluid flow rate estimation unit 112, a clearance previous value storage unit 7, a clearance determination unit 8, and a warning display control unit 10. The warning display unit 13, the clearance previous value storage unit 7, the clearance determination unit 8, and the warning display control unit 10 have the same functions as those of the brake control device 1.

  The liquid level acquisition unit 111 of the brake control device 1 has a function of measuring the liquid level of the reservoir tank, and the fluid flow rate estimation unit 112 calculates the brake fluid flow rate FBF based on the measured value. It has a function. Specifically, when the liquid level of the reservoir tank when the brake is depressed by the driver is L1, and the liquid level when the brake is detected to be released is L2, (L1- L2) × Area A calculates the brake fluid flow rate FBF (area A is the area of the hatched portion in FIG. 3). Snow fade can be detected based on this value. As a result, the brake fluid flow rate can be determined without attaching additional components such as sensors, and the cost can be reduced.

  Also in a vehicle having an automatic brake mechanism, the brake fluid flow rate FBF calculated by this method may be used for the processing of S16 and S24 in the control processing shown in FIG. 2 or as the previous value of the brake fluid flow rate FBF. Good. Thus, since the previous value of FBF at the time of normal stop immediately after the engine start can be used, the effect of correction by using the previous value of the brake fluid flow rate FBF can be further enhanced.

  DESCRIPTION OF SYMBOLS 1 ... Brake control apparatus, 8 ... Clearance determination part (clearance estimation means, snow fade detection means).

Claims (11)

A clearance estimating means for estimating a clearance between a rotor that rotates together with the wheel and a pad that generates a braking force by pressing against the rotor;
A brake control device comprising: snow fade detection means for detecting a snow fade based on the clearance estimated by the clearance estimation means.   The brake control device according to claim 1, wherein the clearance estimation means estimates the clearance based on a brake fluid flow rate during braking.   The brake control device according to claim 2, wherein the brake fluid flow rate is determined based on a liquid level of a reservoir tank.   The brake control device according to any one of claims 1 to 3, wherein automatic control is performed to estimate the clearance.   The brake control device according to any one of claims 1 to 4, wherein the clearance is estimated when the vehicle is stopped.   The brake control device according to any one of claims 1 to 5, wherein the clearance is estimated when the engine is started.   The brake control device according to any one of claims 1 to 6, wherein when a snow fade is determined by the snow fade detection means, a snow fade elimination process for eliminating the snow fade is performed.   The brake control device according to claim 7, wherein the snow fade elimination process is performed by striking the pad against the rotor by increasing or decreasing a braking pressure.   The brake control device according to claim 7 or 8, wherein the snow fade elimination processing is performed when the vehicle is stopped and the driver does not intend to start.   The brake control device according to any one of claims 1 to 9, wherein a warning is given to a driver when the snow fade detection means determines that a snow fade has occurred.   The brake control device according to any one of claims 1 to 10, wherein the clearance is estimated based on a previously estimated clearance value.

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