JP2007182180A - Vehicle in which brake pad temperature is known individually - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly know temperature of a brake pad of each wheel and to eliminate excessive rising of brake pad temperature in any wheel in a vehicle provided with an anti-lock brake system (ABS) and a traveling stabilization control device (VSC), in which a plurality of wheels are individually slip-controlled. <P>SOLUTION: In the vehicle provided with a plurality of wheels friction-braked by brake pads, the temperature of the brake pad of each wheel is individually known based on the traveling state including stepping-on the brake pedal of the vehicle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle such as an automobile having a plurality of wheels that are frictionally braked by a brake pad, and more particularly to grasping the temperature of a brake pad.

Patent Document 1 listed below estimates the brake pad temperature of a hydraulic brake device in a vehicle adapted to be braked by regenerative braking by a traveling motor and friction braking by a hydraulic brake device. It is described that the target braking force set based on the pedal depression amount is distributed to regenerative braking and friction braking based on the estimated brake pad temperature. In this case, the temperature of the brake pad is calculated as the time integral value assuming that the heat generation at the brake pad is proportional to the product of the vehicle deceleration and the vehicle speed, and heat dissipation is generated in proportion to the temperature rise based on it. Is estimated.
JP 2005-14692 A

  However, at present, many vehicles are equipped with an anti-lock brake system (ABS) and a travel stabilization control device (VSC), and each wheel is individually slip-controlled by these control devices. It is conceivable that the degree of braking is not the same, and the temperature of the brake pad is also different accordingly. Therefore, in order to properly control the brake pad temperature of all the wheels within a predetermined preferable limit value in order to ensure the proper operation of the ABS and VSC, the brake pad temperature of each wheel is adjusted to the slip of each wheel. While paying attention individually, braking by ABS or VSC is shorter in duration of one braking than braking by the driver depressing the brake pedal. Therefore, braking by ABS or VSC The heat generated in the pad is relatively easy to dissipate compared to the heat generated by the driver's depression of the brake pedal. Therefore, even when the amount of heat generated is the same, in the case of braking by ABS or VSC, the driver Compared to braking by depressing the brake pedal, the temperature rise of the brake pad may be estimated to be low. Temperature rise of the brake pad when the braking by the heat generation amount is the same, but rather should be overestimated in comparison with the case of braking by ABS and VSC. In any case, in order to control the distribution between the friction braking and the regenerative braking in response to the temperature increase of the brake pad, the control is performed based on the highest temperature among the brake pad temperatures of each wheel. It is considered important to do.

  Based on the above recognition, an object of the present invention is to provide a vehicle in which the temperature of the brake pad of each wheel can be grasped more accurately.

  In order to solve the above problems, the present invention provides a vehicle having a plurality of wheels that are frictionally braked by a brake pad, and the temperature of the brake pad of each wheel based on the running state including the brake pedal depression state of the vehicle. The vehicle is characterized by being individually grasped.

  The vehicle traveling state may include a control result by ABS or traveling stabilization control.

  In addition, the grasping of the brake pad temperature of each wheel based on the vehicle running state may be performed based on correcting the basic heat generation amount based on the brake hydraulic pressure and the vehicle speed with the slip rate of each wheel based on the vehicle running state control. .

  The vehicle may further include regenerative braking means for performing regenerative braking, and control distribution of friction braking and regenerative braking based on a temperature of a brake pad for at least one of the wheels. In this case, the control of the distribution of friction braking and regenerative braking may be performed based on the highest temperature among the brake pad temperatures of each wheel.

  As described above, in a vehicle having a plurality of wheels frictionally braked by the brake pad, if the temperature of the brake pad of each wheel is individually grasped based on the running state including the brake pedal depression state of the vehicle, Even if there is a difference in the braking degree of each wheel by controlling the running state of the vehicle, and thus a difference in the temperature of the brake pad of each wheel, the temperature of the brake pad is accurately grasped for each wheel individually. Moreover, at that time, whether the braking is caused by depression of the brake pedal by the driver, or braking by ABS or VSC, and the duration is relatively short compared to that caused by depression of the brake pedal, Taking into account the difference in whether heat dissipation occurs more easily, the temperature of the brake pad can be grasped more accurately.

  When the vehicle running state includes the control result by ABS or VSC, the ABS control or VSC control controls the slip of each wheel. Therefore, the amount of heat generated in the brake pad is affected by the slip of the wheel. Calculation is based on slip control of each wheel by ABS control or VSC control, and the temperature of each brake pad can be grasped individually and accurately.

  In particular, if grasping the brake pad temperature of each wheel based on the vehicle running state is performed based on correcting the basic calorific value based on the brake hydraulic pressure and the vehicle speed with the slip rate of each wheel based on the vehicle running state control, It is possible to accurately grasp the effect of slip on the temperature of the brake pad.

  If the vehicle further has regenerative braking means for performing regenerative braking, by controlling the distribution of friction braking and regenerative braking based on the temperature of the brake pad for at least one of the wheels, the temperature of the brake pad is set to a predetermined value. Necessary braking force can be ensured by keeping below a preferable limit value. In this case, in particular, if the control of friction braking and regenerative braking distribution is performed based on the highest temperature of the brake pads of each wheel, it is ensured that the temperature of all brake pads is below a predetermined preferable limit value. Can be maintained.

  FIG. 1 is a diagram schematically showing the configuration of a vehicle having functions of ABS and VSC as one embodiment of the present invention. However, in the vehicle according to the present invention, the temperature of the brake pad is individually grasped based on the running state of the vehicle, and the distribution control of friction braking and regenerative braking is performed based on the information. 1 is a known hardware configuration.

  The vehicle shown in FIG. 1 is a four-wheel drive vehicle in which left and right front wheels and left and right rear wheels are driven, and the distribution of driving force between front and rear wheels can be changed by a central driving force distribution device. The left and right front wheels are steering wheels. A vehicle body not shown in the drawing suspended by these four wheels incorporates a known steering device, driving device, braking device, and electronic control unit (ECU) in various modes.

  The steering device includes a steering wheel, a power actuator, and a steering angle correction device, and the left and right front wheels, which are steered wheels, are steered through the power actuator in accordance with the turning operation of the steering wheel by the driver. At this time, the left and right front wheels are steered at a steering angle obtained by automatically correcting the steering angle based on the steering operation by the steering wheel by the steering angle correction device.

  The drive device includes a power source such as an internal combustion engine, a transmission, and an accelerator pedal, and the output of the power source is controlled according to the depression of the accelerator pedal by the driver and a control command from the electronic control device. It has become so.

  The braking device includes a master cylinder, a hydraulic circuit having a hydraulic control valve, and a brake pedal. In addition to simultaneously braking the four wheels in response to depression of the brake pedal by the driver, electronic control The left and right front wheels and the left and right rear wheels can be individually and selectively braked in accordance with a control command from the apparatus.

  The electronic control device has a main part constituted by a microcomputer, and as a part of the control calculation function by the microcomputer, the turning behavior for calculating the turning behavior for vehicle running state control related to the present invention. A calculation unit, a driving force distribution control unit that distributes the driving force in the front-rear direction, a steering angle correction control unit that corrects a steering angle by a driver's steering operation, and a braking control unit that selectively brakes a selected wheel are included. Yes. The electronic control device is supplied with a signal indicating the vehicle speed from the vehicle speed sensor, a signal indicating the yaw rate of the vehicle body from the yaw rate sensor, a signal indicating the lateral acceleration of the vehicle body from the lateral acceleration sensor, and a signal indicating the steering angle by the steering wheel from the steering angle sensor. In addition, signals indicating various other information are supplied as necessary. The electronic control unit performs various control calculations according to these input signals and a control program preloaded in the microcomputer, and controls the driving force distribution device through the driving force distribution control unit to change the distribution of the driving force between the front and rear wheels. In addition to controlling the steering angle correction device through the steering correction control unit to correct the steering angle, the hydraulic circuit is controlled through the braking control unit to selectively brake the selected wheels individually and output the power source The output of the power source is controlled including regenerative braking with negative.

  FIG. 2 is a flowchart showing an embodiment of the brake pad temperature estimation and friction brake and regenerative braking distribution control based on the brake pad temperature estimation performed by the present invention in the vehicle having the above-described configuration. Control along such a flowchart may be repeated at a cycle of several tens to several hundreds of milliseconds during operation of the vehicle.

  When the control is started, in step 10, the index i for specifying the wheel is incremented by 1 from the state where the index i is reset to 0 at the start of each control. This is for specifying each of the four wheels. For example, i = 1, 2, 3, and 4 indicate the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, respectively. Therefore, first, i is set to 1, and in the above setting, the process is started from the left front wheel.

  Control then proceeds to step 20 where it is determined whether i is 4 or greater. While the answer is no (N), the control proceeds to step 30, and the basic heat generation amount at the brake pad of each wheel (here, the wheel specified at step 10, the same applies hereinafter) based on the vehicle speed and the brake hydraulic pressure. Qgi is calculated as a product Qgi = QgoixKgv of a basic value Qgoi = fqpi (Pi) based on the brake hydraulic pressure and a coefficient Kgv = fqv (V) based on the vehicle speed. The function values fqpi (Pi) and fqv (V) may be obtained with reference to maps as illustrated in FIGS. 3 and 4, respectively.

  Next, the control advances to step 40, and the slip ratio Ri of each wheel is obtained from the operation information of the control device that performs the slip control of the wheel such as ABS or VSC. The slip ratio Ri is a value that is set to 0.95 when the wheel rotation speed compared with the vehicle speed becomes 95% due to slippage caused by braking of the wheels, for example. The basic operation of ABS and VSC is well known in the field of this technology, and can be performed by the configuration of the control device as shown in FIG.

  Next, the control proceeds to step 50, where the cooling coefficient Krc is obtained as the value of the function fw (Wr) based on the rainfall degree Wr determined from the operation of the wiper and a signal from a separately provided rain sensor or the like. Such a function value may also be obtained with reference to a map as illustrated in FIG.

  Next, the control proceeds to step 60, and the heat dissipation coefficient Kv based on the vehicle speed V is obtained as the value of the function fv (V). Such a function value may also be obtained with reference to a map as illustrated in FIG.

  Control then proceeds to step 70 where it is determined whether the brake pedal is depressed. If the answer is yes, control proceeds to step 80 where the heat dissipation coefficient Kc is a predetermined value Kc1, and if the answer is no, control proceeds to step 90 where the heat dissipation coefficient Kc is a predetermined value. Kc2. Kc1 and Kc2 have a longer duration when braking is performed by the driver depressing the brake pedal as described above, and the heat generated in the brake pads is dissipated from the brake pads compared to the case where braking is performed by ABS or VSC. Considering that the degree is low, it is appropriately set so that Kc1 <Kc2.

  Next, the control proceeds to step 100, where the heat dissipation amount Qdi from the brake pad is determined as the brake pad temperature Tpi based on the vehicle speed V, the temperature Ta, the cooling coefficient Krc obtained above, and the heat dissipation coefficients Kv and Kc. The basic value Qdoi = αx (Tpi−Ta), which is obtained by multiplying the difference between the temperature Ta by the heat transfer coefficient α of heat dissipation, is calculated as the value Qdi = QdoixKrcxKvxKc, which is corrected by the cooling coefficient Krc and the heat dissipation coefficients Kv and Kc. When the first step reaches here, the value of Tpi has not been obtained yet, so an appropriate initial value is used. From the next flow, it is calculated in the following step 70 in the previous flow. Values are used.

  Next, the control proceeds to step 110, where the temporary estimated value Tqi of the brake pad temperature of each wheel is calculated based on the calorific value Qgi, the slip rate Rsi, the heat dissipation amount Qdi, the brake pad mass M and the specific heat γ. Based on the above, Tqi = (QgixRsi−Qdi) / (γxM).

  Control then proceeds to step 120 where it is determined whether the difference between the Tqi value calculated in step 110 above and the Tpi used in step 100 is less than or equal to a predetermined deviation ΔT. . While the answer is no, control proceeds to step 130 where the value of Tpi is replaced by the value of Tqi and control then returns to step 100. If steps 100 and 110 are repeated in this manner, the answer to step 120 will eventually turn to yes (Y), and control will then proceed to step 140.

  In step 140, it is determined whether or not the brake pad temperature Tpi for the wheel i calculated this time is higher than the maximum value Tpmax of the brake pad temperature Tpi calculated for the four wheels i = 1 to 4. In step 110 for the first time after the start of control, the answer is yes because the temperature of Tpmax has not yet been calculated and remains reset to 0 at the start of control. After that, the answer will be either yes or no. If the answer is yes, control proceeds to step 150 where the value of Tpi is Tpmax, which indicates the maximum brake pad temperature, and if the answer is no, step 150 is bypassed.

  In any case, the control returns to step 10 and the value of i is incremented by 1 and the same processing is performed for the next wheel. Thus, the process of estimating the brake pad temperature Tpi is performed for all four wheels, and when the highest one of them is obtained as Tpmax, the answer to step 20 changes from no to yes. Proceed to step 160.

  In step 160, Tpmax is compared with Tt set as the upper limit value of the brake pad temperature, and a deviation ΔT is calculated.

  Control then proceeds to step 170, where the temperature Tpmax of the four-wheel brake pad that has risen the most has exceeded Tt, and a portion of the friction braking by the brake pad is reduced and regenerated. In order to replace it with braking, a reduction width ΔP for reducing the brake hydraulic pressure is calculated as a function value fp (ΔT) of ΔT. This function value may be obtained with reference to a map as illustrated in FIG.

  Next, the control advances to step 180, and the value of the increment ΔFrb is obtained as the value of the function frb (ΔP), assuming that the braking force is reduced by the regenerative braking by reducing the brake hydraulic pressure by ΔP. This function value may also be obtained with reference to a map as illustrated in FIG.

  Next, the control proceeds to step 190, where the throttle opening reduction amount Δθth required to generate the regenerative braking force increment ΔFrb is calculated as the value of the function fth (ΔFrb). This may also be obtained according to the gear position at that time with reference to a map as illustrated in FIG.

  Next, the control proceeds to step 200 where it is determined whether or not the value obtained by subtracting Δθth from the current throttle opening θth is positive, that is, whether or not the throttle opening can be reduced by Δθth. . If the answer is yes, the control proceeds to step 210, and the throttle opening is reduced by Δθth. On the other hand, if the answer is no, that is, if the throttle opening can no longer be reduced by Δθth, the control proceeds to step 220 and a downshift is performed to lower the gear position.

  In either case, control then proceeds to step 230 where the brake hydraulic pressure Pi is reduced by ΔP.

  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 figure which shows in figure the structure of the vehicle provided with the function of ABS or VSC as one embodiment of this invention. 6 is a flowchart showing one embodiment of the estimation of the temperature of the brake pad and the distribution control of friction braking and regenerative braking based on the estimation of the temperature of the brake pad performed in the vehicle of the present invention. The figure which shows an example of the map referred by step 30 of the flowchart of FIG. The figure which shows an example of the map referred by step 30 of the flowchart of FIG. The figure which shows an example of the map referred by step 50 of the flowchart of FIG. The figure which shows an example of the map referred by step 60 of the flowchart of FIG. FIG. 3 is a diagram showing an example of a map that is referred to in step 170 of the flowchart of FIG. 2. The figure which shows an example of the map referred by step 180 of the flowchart of FIG. FIG. 3 is a diagram illustrating an example of a map that is referred to in step 190 of the flowchart of FIG. 2.

Claims (6)

  The vehicle is equipped with a plurality of wheels that are frictionally braked by the brake pads, and the temperature of the brake pads of each wheel is individually grasped based on the running state including the brake pedal depression state of the vehicle. Characteristic vehicle.   The vehicle according to claim 1, wherein the vehicle running state includes a control result by ABS.   The vehicle according to claim 1, wherein the vehicle running state includes a control result by running stabilization control.   The brake pad temperature of each wheel based on the vehicle running state is grasped based on correcting the basic heat generation amount based on the brake hydraulic pressure and the vehicle speed with the slip rate of each wheel based on the vehicle running state control. The vehicle according to claim 2 or 3.   The vehicle further includes regenerative braking means for performing regenerative braking, and controls distribution of friction braking and regenerative braking based on a temperature of a brake pad for at least one of the wheels. The vehicle according to any one of 1 to 4. 6. The vehicle according to claim 5, wherein the control of the distribution of the friction braking and the regenerative braking is performed based on the highest temperature among the brake pad temperatures of each wheel.

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