JP2007223527A - Brake controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake controller capable of certainly relaxing deterioration of feeling in braking generated accompanying with deterioration of performance of a tire and increase of an abrasion amount of the tire more than ever. <P>SOLUTION: In the present invention relating to the present application, the maximum value of friction force generated on a brake upon reduction of performance is made smaller than the maximum value of the friction force generated on the brake in usual performance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brake control device provided in a vehicle.

  For example, the performance of a tire is determined by rotating a wheel at a constant speed with a wheel composed of a tire and a disc wheel standing on the predetermined surface so that the tread portion of the tire is in contact with the predetermined surface. In addition, it is indicated by the magnitude of the longitudinal force generated in the tire when a constant load is applied to the wheel (that is, the frictional force generated by the friction between the tire and a predetermined surface). It can be said that the greater the longitudinal force at this time, the better the performance of the tire. The quality of the tire depends on, for example, the tire pressure.

  The performance of the tire is an important factor for the user who uses the vehicle. For example, as the tire performance deteriorates, the feeling during braking deteriorates and the amount of tire wear during braking increases. When the amount of wear of the tire increases, the tire replacement time is advanced correspondingly, and the convenience of the user who uses the vehicle is impaired. Note that “feeling” in the present application is what a vehicle occupant feels, and means, for example, ride comfort.

Therefore, the invention described in Patent Document 1 sets an appropriate range for the tire air pressure, calculates an excess / deficiency amount for the appropriate tire air pressure range, and the calculated excess / deficiency amount exceeds a predetermined value. , Alarm to that effect. When the driver notices this warning, the brake pedal feeling is improved by adjusting the amount of depression of the brake pedal, compared to when the brake pedal is not operated. Can be reduced.
JP 2003-267010 A

  However, in the invention described in Patent Document 1, such a brake pedal operation may not be performed unless the driver notices the alarm. If such a brake pedal operation is not performed, the feeling at the time of braking deteriorates and the amount of wear of the tire at the time of braking becomes larger than when the tire air pressure is within an appropriate range. That is, in the invention described in Patent Document 1, it is possible to mitigate the deterioration of the feeling during braking and the increase in the amount of wear of the tire caused by the decrease in the tire air pressure (that is, the deterioration of the tire performance). There is no possibility.

  In view of the above circumstances, the present invention provides a brake control device that can more reliably alleviate the deterioration in feeling during braking and the increase in the amount of tire wear that occur with the deterioration in tire performance. It is to provide.

  In order to achieve the above object, the invention according to the present application includes a tire performance decrease calculation unit that calculates a performance value of a tire included in a vehicle, and the performance value calculated by the tire performance decrease calculation unit is less than a predetermined performance decrease determination value. Brake control means for controlling the brake corresponding to the tire at the time of the performance deterioration and the normal performance when the performance value calculated by the tire performance reduction calculation means is equal to or higher than the performance deterioration judgment value. The maximum value of the frictional force generated in the brake when the performance is reduced is made smaller than the maximum value of the frictional force generated in the brake during the normal performance.

  The invention according to the present application makes the maximum value of the frictional force generated in the brake at the time of performance degradation smaller than the maximum value of the frictional force generated at the brake during the normal performance. Even if the driver does not adjust the depression amount of the brake pedal, the feeling during braking can be improved as compared with the conventional one, and the tire wear amount can be reduced as compared with the conventional one. In other words, the invention according to the present application can more reliably alleviate the deterioration of the feeling at the time of braking and the increase in the amount of wear of the tire that occur with the deterioration of the tire performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a brake control device 1 according to the present invention. The brake control device 1 includes an air pressure sensor 2, a storage unit 3, a tire performance deterioration calculation unit 4, a brake switch 5, a wheel speed sensor 6, and a brake control unit 7. The brake control device 1 is mounted on a vehicle including a front left brake 8, a front right brake 9, a rear left brake 10, and a rear right brake 11. The front left brake 8 corresponds to the front left wheel, the front right brake 9 corresponds to the front right wheel, the rear left brake 10 corresponds to the rear left wheel, and the rear right brake 11 corresponds to the rear right wheel. To do.

  When the brake pedal is depressed, the hydraulic pressure corresponding to the amount of depression (for example, the amount of depression is represented by the amount of movement of the surface of the brake pedal that the driver's foot contacts) The brake is supplied to the front right brake 9, the rear left brake 10, and the rear right brake 11, and these brakes operate based on the supplied hydraulic pressure. For example, the front left brake 8 includes a disc rotor that rotates integrally with the front left wheel, and a brake pad. When hydraulic pressure is applied to the front left brake 8, a force corresponding to the hydraulic pressure is applied. By pressing the brake pad against the disc rotor, a frictional force corresponding to the hydraulic pressure is generated in the disc rotor. That is, this friction force causes the rotation speed of the front left wheel to be slower than the vehicle speed, so that friction occurs between the front left wheel and the road surface, and this friction generates braking force on the front left wheel. . Therefore, the braking force generated on the front left wheel depends on the hydraulic pressure applied to the front left brake 8, that is, the friction force generated on the disc rotor. Other brakes have the same configuration and generate braking force on the corresponding wheels.

  The air pressure sensor 2 is provided for each tire included in the vehicle. The air pressure sensor 2 measures the air pressure of the tire corresponding to the air pressure sensor 2 and outputs a tire air pressure signal related to the measured tire air pressure value and tire identification information indicating the tire for which the air pressure has been measured to a tire performance deterioration calculation unit. 4 is output. The tire identification information is information for identifying a tire included in the vehicle, and is set in advance.

  The memory | storage part 3 memorize | stores the performance value map corresponding | compatible relation table comprised with a performance value map and the tire identification information corresponding to a performance value map for every tire with which a vehicle is equipped. The performance value map is composed of mathematical expressions indicating the correspondence between the tire performance value and the tire air pressure. An example in which the performance value map is shown in a graph is shown in FIG. When the performance value map is graphed, polygonal lines such as polygonal lines L1 and L2 are obtained. A polygonal line L1 indicates a performance value map corresponding to a general tire (that is, a tire other than a run-flat tire), and a polygonal line L2 indicates a performance value map corresponding to the run-flat tire. A run-flat tire can maintain a higher performance value than a general tire.

  The performance value of a tire is determined by rotating the wheel at a constant speed and applying a constant load to the wheel while standing on the predetermined surface so that the tread portion of the tire is in contact with the predetermined surface. It is indicated by the magnitude of the longitudinal force generated in the tire when hit. The method for measuring the longitudinal force of the tire is, for example, as follows. That is, the wheel is fixed to the upper surface of the drum whose rotation axis is horizontal so that the rotation axis is parallel to the rotation axis of the drum and can be rotated. Therefore, in this measurement method, the upper surface of the drum is a predetermined surface. Then, the drum is rotated on the spot with a certain load applied to the wheels. As a result, the wheel rotates, friction is generated between the wheel and the peripheral surface of the drum, and a longitudinal force is generated on the tire. Therefore, the longitudinal force is measured.

  The performance value map is generated as follows, for example. That is, several values are selected within a range of 50 (kPa) to 230 (kPa), and the longitudinal force generated in the tire is measured by the measurement method described above in a state where the selected air pressure is applied to the tire. taking measurement. Thus, data indicating the correspondence between the longitudinal force generated in the tire and the tire air pressure is obtained. Of the data in the range above the tire air pressure value (this value is P1 in FIG. 2), the longitudinal force value indicated by any one of the data is the other value in the range. It substantially matches the value of the longitudinal force indicated by all the data (for example, the difference between these values is always within ± 10 (N)). Therefore, the performance value within this range is set to “1”, the arithmetic mean of the longitudinal force within this range is calculated, and the longitudinal force within the other range is divided by the calculated arithmetic mean. The performance value within the range is calculated. Then, a performance value map is generated based on the obtained tire performance value and tire air pressure.

  The memory | storage part 3 memorize | stores the mounting tire corresponding | compatible table comprised with tire identification information and the installation position information corresponding to tire identification information for every tire with which a vehicle is equipped. Here, the installation position information indicates the installation position of the wheel, and the installation position information corresponding to the tire identification information indicates the installation position of the tire indicated by the tire identification information. The data stored in the storage unit 3 can be rewritten according to the fact that the user has replaced the tire.

  The tire performance deterioration calculation unit 4 calculates the tire performance value for each tire included in the vehicle based on the tire air pressure signal given from the air pressure sensor 2 and the performance value map correspondence table stored in the storage unit 3. calculate. The tire performance deterioration calculation unit 4 determines, for each tire included in the vehicle, a condition that the calculated performance value is less than a predetermined performance deterioration determination value (for example, 0.7). If it exists, a performance deterioration tire determination signal related to the performance value of the tire and the tire identification information indicating the tire is generated and output to the brake control unit 7.

  The brake switch 5 generates a brake pedal operation signal and outputs it to the brake control unit 7 when the brake pedal is operated.

  The wheel speed sensor 6 is provided for each wheel provided in the vehicle. The wheel speed sensor 6 measures the wheel speed corresponding to the wheel speed sensor 6, that is, the wheel speed, and the wheel related to the measured wheel speed and the installation position information indicating the installation position of the wheel corresponding to the wheel speed sensor 6. A speed signal is output to the brake control unit 7.

  The brake control unit 7 is based on the performance degradation tire determination signal given from the tire performance decline calculation unit 4, the brake pedal operation signal given from the brake switch 5, and the wheel speed signal given from the wheel speed sensor 6. The front left brake 8, the front right brake 9, the rear left brake 10, and the rear right brake 11 are controlled.

  Next, the content of the process performed by the brake control device 1 will be described along the flowcharts shown in FIGS. 3 and 4. The process performed by the brake control device 1 is roughly divided into a performance value calculation process and a brake control process. FIG. 3 is a flowchart showing the procedure of the performance value calculation process, and FIG. 4 is a flowchart showing the procedure of the brake control process. While the performance value calculation process and the brake control process are being performed, the air pressure sensor 2 outputs a tire air pressure signal to the tire performance deterioration calculation unit 4 periodically (for example, every 5 (min)), and the brake switch 5 When the brake pedal is operated, a brake pedal operation signal is generated and output to the brake control unit 7, and the wheel speed sensor 6 periodically outputs the wheel speed signal (for example, every 1 (ms)). Output to the brake control unit 7. While the brake control device 1 repeatedly performs the brake control processing, the brake control device 1 performs performance value calculation processing each time the air pressure sensor 2 outputs a tire air pressure signal. First, the performance value calculation process will be described as an example of the performance value calculation process performed for the front left tire. The brake control device 1 performs the same performance value calculation process for all tires provided in the vehicle.

  That is, in step ST <b> 1, the tire performance deterioration calculation unit 4 takes in the tire air pressure signal output from the air pressure sensor 2.

  In step ST <b> 2, the tire performance deterioration calculation unit 4 calculates the front based on the tire air pressure signal given from the air pressure sensor 2, the performance value map correspondence table stored in the storage unit 3, and the attached tire correspondence table. The performance value of the left tire is calculated. Specifically, the tire performance deterioration calculation unit 4 is based on the tire identification information indicated by the tire pressure signal, the tire identification information constituting the attached tire correspondence table, and the tire identification information constituting the performance value map correspondence table. The front left tire pressure value and the performance value map corresponding to the front left tire are extracted, and the front left tire pressure value is applied to the performance value map corresponding to the front left tire. The tire performance value is calculated.

  In step ST3, the tire performance deterioration calculation unit 4 determines a condition that the performance value of the front left tire is less than the performance deterioration determination value. If this condition is satisfied, the process proceeds to step ST4, and this condition is satisfied. If not, the performance value calculation process for the front left tire is terminated.

  In step ST <b> 4, the tire performance decrease calculation unit 4 generates a performance decrease tire determination signal related to the performance value of the front left tire and the tire identification information indicating the front left tire, and outputs it to the brake control unit 7. Thereafter, the tire performance decrease calculation unit 4 ends the performance value calculation process for the front left tire.

  Next, the brake control process will be described as an example of the brake control process performed on the front left tire. The brake control device 1 performs the same brake control process for all tires provided in the vehicle.

  That is, in step ST5 shown in FIG. 4, the brake control unit 7 determines a condition that a brake pedal operation signal is given from the brake switch 5, and if this condition is satisfied, the process proceeds to step ST6. If is not satisfied, the brake control process is terminated.

  In step ST6, the brake control unit 7 determines the condition that the performance-reduced tire determination signal is given. If this condition is satisfied (“YES” in step ST6), the process proceeds to step ST7, where the condition is set. If not satisfied (“NO” in step ST6), the process proceeds to step ST10. In the following description, the case of “YES” in step ST6 is referred to as “during performance degradation”, and the case of “NO” in step ST6 is referred to as “in normal performance”.

  In step ST7, the brake control unit 7 determines that the performance value of the front left tire is a predetermined friction force change value (for example, 0.5. The friction force change value is the above-described performance deterioration determination) based on the performance deterioration tire determination signal. If this condition is satisfied ("YES" in step ST7), the process proceeds to step ST8, and if this condition is not satisfied ("NO" in step ST7). ) Go to step ST9. In the following description, the case of “YES” in step ST7 is “when the friction force is changed”, and the case of “NO” in step ST7 is “when the anti-skid control is changed”.

  In step ST8, the brake control unit 7 sets the maximum value of the friction force generated in the front left brake 8 to a value smaller than the maximum value of the friction force generated in the front left brake 8 during normal performance. Specifically, the brake control unit 7 sets the maximum value of the frictional force generated in the front left brake 8 based on the following formula (1). Thereafter, the brake control unit 7 proceeds to step ST10.

F = F0 * b (1)
F: Maximum value of the friction force generated in the front left brake 8 when the friction force is changed, F0: Maximum value of the friction force generated in the front left brake 8 during normal performance, b: Performance value of the front left tire In step ST9, the brake The control unit 7 sets the target slip ratio to a value lower than the target slip ratio corresponding to the normal performance. Specifically, the brake control unit 7 sets a target slip ratio based on the following equation (2). Thereafter, the brake control unit 7 proceeds to step ST10. Note that the target slip ratio is used for anti-skid control, and the target slip ratio corresponding to the normal performance is set in advance, and its value is, for example, 0.9.

A = A0 * b (2)
A: Target slip ratio corresponding to anti-skid control change, A0: Target slip ratio corresponding to normal performance In step ST10, the brake control unit 7 takes in the wheel speed signal given from the wheel speed sensor 6 and takes it in Based on the wheel speed signal and the following expression (3), the slip ratio of the front left wheel is calculated. The pseudo vehicle speed is the speed of the wheel that rotates at the fastest speed among the wheels provided in the vehicle.

B = (V0−V1) / V0 (3)
B: Slip rate of front left wheel, V0: Pseudo vehicle speed, V1: Wheel speed of front left wheel The brake control unit 7 determines that the slip rate of the front left wheel is a predetermined anti-skid control execution value (for example, 0.4). If it is less than the normal brake control for the front left brake 8, the anti-skid control is performed for the front left brake 8 if the slip ratio of the front left wheel is equal to or greater than the anti-skid control execution value.

  The brake control unit 7 performs the following processing in the normal brake control. That is, the brake control unit 7 applies the hydraulic pressure generated according to the operation of the brake pedal to the front left brake 8 as it is during normal performance and when changing anti-skid control. On the other hand, when changing the frictional force, the brake control unit 7 calculates the hydraulic pressure necessary for the maximum frictional force set in step ST8 to be generated in the front left brake 8, and the fluid given to the front left brake 8 is calculated. The pressure is adjusted so as not to exceed the calculated hydraulic pressure. That is, a frictional force not more than the maximum value set in step ST8 is generated in the front left brake 8.

  The brake control unit 7 performs the following processing in the anti-skid control. That is, the brake control unit 7 performs the anti-skid control based on the target slip ratio corresponding to the normal performance at the normal performance. That is, the brake control unit 7 determines that the slip ratio of the front left wheel corresponds to the target slip ratio during normal performance and the hydraulic pressure recovery slip ratio (for example, 0.01. The hydraulic pressure applied to the front left brake 8 is alternately increased and decreased so as to be displaced between the front left wheel and the front left wheel when the wheel speeds substantially coincide with each other. repeat. When the anti-skid control is changed, the brake control unit 7 performs the same anti-skid control based on the target slip ratio corresponding to the anti-skid control change (that is, the target slip ratio set in step ST9).

  The brake control unit 7 performs anti-skid control based on the maximum value set in step ST8 when the frictional force is changed. That is, the brake control unit 7 calculates the hydraulic pressure necessary for the maximum frictional force set in step ST8 to be generated in the front left brake 8. The brake control unit 7 determines whether the slip ratio of the front left wheel is between the slip ratio when the hydraulic pressure applied to the front left brake 8 matches the calculated hydraulic pressure and the hydraulic pressure recovery slip ratio. The fluid pressure applied to the front left brake 8 is alternately increased and decreased so as to be displaced.

  Here, the target slip ratio depends on the maximum value of the frictional force generated in the front left brake 8. That is, the larger the maximum frictional force, the higher the target slip ratio. Therefore, the maximum value of the friction force generated in the front left brake 8 when the anti-skid control is changed is smaller than the maximum value of the friction force generated in the front left brake 8 during normal performance only when the anti-skid control is performed. .

  On the other hand, the maximum value of the frictional force generated in the front left brake 8 when the frictional force is changed is greater than the maximum value of the frictional force generated in the front left brake 8 during normal performance, regardless of whether anti-skid control is performed. Get smaller.

  As described above, the brake control device 1 makes the maximum value of the frictional force generated in the brake when the performance is reduced smaller than the maximum value of the frictional force generated in the brake during the normal performance. Even if the driver of the vehicle does not adjust the depression amount of the brake pedal, the feeling during braking can be improved as compared with the conventional case, and the wear amount of the tire can be reduced as compared with the conventional case. In other words, the brake control device 1 can more reliably alleviate the deterioration of the feeling during braking and the increase in the amount of wear of the tire that occur with the deterioration of the tire performance.

  Further, the brake control device 1 sets the target slip ratio corresponding to the anti-skid control change and the target slip ratio corresponding to the normal performance. The target slip ratio corresponding to the anti-skid control change corresponds to the target slip ratio corresponding to the normal performance. Anti-skid control is performed based on the set target slip ratio. Therefore, even in the case of performing anti-skid control, the brake control device 1 more reliably improves the feeling of braking at the time of braking and the increase in the amount of wear of the tire caused by the deterioration of the tire performance. Can be relaxed.

  Furthermore, since the brake control device 1 performs normal brake control with the same content during normal performance and during anti-skid control change, even during anti-skid control change, during normal brake control, the same as during normal performance. A certain degree of feeling can be secured.

  Further, the brake control device 1 can calculate the tire performance value based on the tire air pressure signal output from the air pressure sensor 2 and the performance value map, so that the tire performance value every time brake control is performed. The tire performance value can be calculated more easily and more quickly than when measuring.

  Note that the present embodiment can be changed without departing from the spirit of the present invention.

1 is a schematic plan view showing a brake control device according to an embodiment of the present invention. It is a flowchart which shows an example of a performance value map. It is a flowchart which shows an example of the process by a brake control apparatus. It is a flowchart which shows an example of the process by a brake control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Brake control device 2 ... Air pressure sensor 3 ... Memory | storage part 4 ... Tire performance fall calculation part 5 ... Brake switch 6 ... Wheel speed sensor 7 ... Brake control part 8 ... Front left brake 9 ... Front right brake 10 ... Rear left brake 11 ... Rear right brake

Claims (3)

Tire performance deterioration calculating means for calculating the performance value of the tire provided in the vehicle;
When the performance value calculated by the tire performance deterioration calculating means is less than a predetermined performance deterioration determination value, and when the performance value calculated by the tire performance deterioration calculating means is equal to or higher than the performance deterioration determination value And a brake control means for controlling a brake corresponding to the tire,
The brake control device, wherein the brake control means makes the maximum value of the frictional force generated in the brake when the performance is reduced smaller than the maximum value of the frictional force generated in the brake during the normal performance.   The brake control means has a target slip ratio corresponding to the normal performance and a target slip ratio corresponding to the normal performance. The target slip ratio corresponding to the normal performance is more than the target slip ratio corresponding to the normal performance. The brake control device according to claim 1, wherein the anti-skid control is performed based on the set target slip ratio. Air pressure measuring means for measuring the air pressure of the tire;
Storage means for storing a performance value map indicating a correspondence relationship between the tire performance value and the tire air pressure;
The tire performance deterioration calculating unit calculates the tire performance value based on the tire air pressure measured by the air pressure measuring unit and a performance value map stored in the storage unit. The brake control device described.

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