JPH10300766A - Anomaly detecting method of wheel speed sensor, wheel speed detecting device, and wheel skid control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect sensor anomalies in which abnormal pulses occur in the vicinities of the rising edges and falling edges of normal pulses. SOLUTION: A wheel speed sensor includes a sensor rotor rotating together with a magnetic pickup and a wheel. When an iron piece adheres to a downstream edge of the head of the magnetic pickup with respect to the direction of rotation of the sensor rotor, the iron piece is sucked by suction to the teeth of the sensor rotor to cause sudden changes in the density of magnetic flux and abnormal pulses regularly occur in the vicinities of the rising edges of pulses. By this, as the fluctuation of rising periods becomes larger than the fluctuation of falling periods and the ratio of the integrated value of the ratio of two successive rising periods to the integrated value of the ratio of two successive falling periods becomes larger than a set value, it is possible to detect sensor anomalies. That the signs of the successive differences between successive rising periods are opposite and that the absolute value of the difference between the successive totals of the rising periods of successive pulses is or less than a set value indicate sensor anomalies.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel speed sensor abnormality detecting method, a wheel speed detecting device, and a wheel slip control device.

[0002]

2. Description of the Related Art A wheel speed detecting device generally includes a wheel speed sensor and wheel speed calculating means. The wheel speed sensor generates a pulse signal whose cycle changes according to the rotation speed of the wheel, and the wheel speed calculation means calculates the wheel speed based on the cycle of the pulse signal. JP-A-62-2
The wheel speed detecting device described in Japanese Patent No. 55871 is an example thereof. In this wheel speed detecting device, noise is detected while detecting the wheel speed. The absolute value of the value obtained by subtracting the wheel speed calculated one time ago from the latest wheel speed calculated is obtained. If the value exceeds the set value, it is determined that noise has occurred. However, in this wheel speed detection device, for example, an abnormal pulse is generated near the rising or falling of a normal pulse due to the attachment of an iron piece to the sensor pickup or the like, and a bad road (for example, an uneven road surface) Due to the frequent fluctuation of the wheel speed as in the case of traveling, it is not possible to distinguish the noise from the frequent fluctuation of the pulse period, and it is not possible to take appropriate measures.
In the former case, the rotation of the wheels is normal, but this is caused by an abnormality of the wheel speed sensor, and an abnormal pulse is generated in addition to the normal pulse. Each pulse of the pulse signal is divided into two, and the absolute value of the difference between the two wheel speeds calculated in succession exceeds the set value. In the latter case, the rotation of the wheels becomes irregular, and the pulse period becomes longer or shorter, so that the absolute value of the difference between the two wheel speeds calculated in succession exceeds the set value. .

[0003]

SUMMARY OF THE INVENTION The present invention provides a method for detecting an abnormality in a wheel speed sensor in which an abnormal pulse is generated near a rising or falling edge of a normal pulse. Make it an issue. This challenge
The problem can be solved by the sensor abnormality detection methods (1) to (17). (1) A method for detecting an abnormality of a wheel speed sensor that generates a pulse signal whose cycle changes in accordance with the rotation speed of a wheel, the method comprising: changing a rising cycle and a falling cycle of a pulse signal; A wheel speed sensor abnormality detection method for detecting a sensor abnormality based on a difference between the wheel speed sensors. (Claim 1) The fluctuation between the rising period and the falling period of the pulse signal becomes large based on the unevenness of the road surface and the like, but the fluctuation state of both periods is almost the same. On the other hand, if an abnormal pulse occurs near the rising or falling edge of the normal pulse due to the attachment of iron pieces to the pickup of the wheel speed sensor, the rising period of the pulse signal and the rising period Not only does the fluctuation with the falling cycle increase,
There is a difference between how the rising cycle varies and how the falling cycle varies. Therefore, the abnormality of the wheel speed sensor can be detected based on the difference in the manner of the change. The sensor abnormality is detected based on the fact that the difference between the rising state and the falling period of the pulse differs from the allowable state. In the wheel speed detection device described in the above publication, immediately after the occurrence of the sensor abnormality, although the wheel speed fluctuates, it cannot be distinguished from running on a rough road, and further the sensor abnormality continues, When the pulse is generated continuously, the wheel speed does not fluctuate and the sensor abnormality cannot be recognized. On the other hand, as long as a sensor abnormality occurs, a difference occurs between a method of changing the rising cycle of the pulse and a method of changing the falling cycle. Therefore, according to the wheel speed sensor abnormality detecting method according to the present invention, the abnormal pulse The effect that the sensor abnormality can be detected even if the error occurs continuously is also obtained. (2) The manner in which the rising cycle varies is defined based on at least one of a ratio and a difference between two successive rising cycles, and the manner in which the falling cycle varies between two successive falling cycles. The difference between the two rising periods is defined based on at least one of the ratio and the difference, and the difference in the manner of the fluctuation is the ratio between at least one of the two rising periods and the difference between the two falling periods. The wheel speed sensor abnormality detection method according to the above mode (1), which is defined based on at least one of a ratio and a difference between at least one of the wheel speed and the difference. (3) At least one of the ratio and the difference between the two successive rising periods is obtained based on a plurality of pairs of the successive rising periods, and at least one of the ratio and the difference between the two consecutive falling periods is obtained. The wheel speed sensor abnormality detection method according to the above mode (2), wherein one is obtained based on a plurality of pairs of successive falling periods. (4) The difference between the way of changing the rising cycle and the way of changing the falling cycle is related to the difference between the ratio of two successive rising cycles and the ratio of two successive falling cycles. The wheel speed sensor abnormality detection method according to the above mode (1), which is defined by the ratio difference related amount. (Claim 2) The higher the wheel speed is, the shorter the rising cycle and the falling cycle are, and even if the two successive cycles have large fluctuations, the difference between the two cycles is small. If the wheel speeds are different, it is not possible to judge whether the period variation is large or small only by the magnitude of the period difference. According to the period ratio, this inconvenience can be avoided. Even if the wheel speed is high and the rising cycle and the falling cycle are short, or if the wheel speed is low and the rising cycle and the falling cycle are long, the cycle ratio increases if the manner of changing the cycle is large. Therefore, if the difference between the way of changing the rising cycle and the way of changing the falling cycle is defined by the period ratio difference related amount, the common abnormality detection set period ratio related amount and the common abnormality detection related amount regardless of the wheel speed. Can detect the abnormality of the wheel speed sensor. (5) The wheel speed sensor abnormality detection method according to the above mode (4), wherein the period ratio difference related quantities are obtained for a plurality of pairs of successive rising and falling periods. Even if the period ratio difference related amount is acquired for each pair of successive rising and falling periods, the sensor abnormality can be detected, but each of the plural pairs of successive rising and falling periods and the falling period can be detected. Acquiring the average period ratio difference related amount of the above increases the reliability of sensor abnormality detection. This is especially true when abnormal pulses occur continuously, such as when abnormal pulses are generated due to iron piece adhesion. For example, the rising period ratio is obtained for each of a plurality of pairs of successive rising periods, the falling period ratio is obtained for each of a plurality of pairs of successive falling periods, and the obtained plurality of rising period ratios and Even if one period ratio difference related amount is obtained from an average value such as the average value and the median value of the falling period ratio, one pair of the rising period and one falling period is obtained. The acquisition of the period ratio difference related amount may be repeated a plurality of times, and one average period ratio difference related amount may be acquired from the acquired period ratio difference related amounts. In the latter case, a smoothing means can be used. The values of a number of period ratio difference related quantities that are sequentially acquired are smoothed by a digital filter, or the difference between successive cycle ratio difference related quantities is smoothed by setting an upper limit and a lower limit. In addition, the ratio of the sum of two rising periods obtained by calculating the sum of every other rising period among the plurality of rising periods is obtained, and the sum of every other falling period among the plurality of falling periods is obtained. May be determined to obtain the ratio of the two sums of the falling periods, and the period ratio difference related amount may be obtained based on the ratio. (6) The period ratio difference related amount is a rising period ratio obtained by dividing a larger one of two successive rising periods by a smaller one and a larger one of two succeeding falling periods being a smaller one. It is the period ratio ratio of the larger period ratio divided by the smaller period ratio among the falling period ratios divided by, and if the period ratio ratio is larger than the set period ratio ratio, it is determined that the sensor is abnormal (4) or The method for detecting a wheel speed sensor abnormality according to the item (5). (7) The period ratio difference related amount is a rising period ratio obtained by dividing a smaller one of two successive rising periods by a larger one, and a smaller one of two succeeding falling periods being a larger one. Of the falling period ratio divided by the period ratio of the smaller period ratio divided by the larger period ratio.If the period ratio ratio is smaller than the set period ratio ratio, it is determined that the sensor is abnormal (4) or The method for detecting a wheel speed sensor abnormality according to the item (5). (8) The period ratio difference related quantity is a rising period ratio obtained by dividing a larger one of two successive rising periods by a smaller one, and a larger one of two succeeding falling periods being a smaller one. This is the absolute value of the difference from the fall period ratio divided by, and if the period ratio difference absolute value is larger than the set period ratio difference absolute value, it is determined that the sensor is abnormal.The wheel described in (4) or (5) Speed sensor abnormality detection method. (9) The difference between the manner in which the rising cycle varies and the manner in which the falling cycle varies depends on the absolute value of the difference between two successive rising cycles and the absolute value of the difference between two successive falling cycles. The wheel speed sensor abnormality detection method according to the above mode (1), wherein the method is defined by a period difference absolute value difference related amount related to the difference between the two. (10) The wheel speed sensor abnormality detection method according to the above mode (9), wherein the period difference absolute value difference related quantities are acquired for a plurality of pairs of successive rising and falling periods. The same applies to the period difference absolute value difference related amount as described above for the period ratio difference related amount. (11) The period difference absolute value difference related amount is the absolute value of the difference between the absolute value of the difference between the two successive rising periods and the absolute value of the difference between the two successive falling periods. The wheel speed sensor abnormality detection method according to the above mode (9) or (10), wherein the sensor abnormality is determined when the difference absolute value difference is larger than the set cycle difference absolute value difference. When the period difference absolute value difference related amount is used as the period difference absolute value, for example, by providing a set period difference absolute value difference related amount for abnormality detection in accordance with the wheel speed, even if the wheel speed is different, the wheel speed sensor can be used. Can be accurately detected. The set cycle difference absolute value difference related amount may be set stepwise according to the wheel speed, or may be set steplessly. (12) The larger one of the absolute value of the difference between the two successive rising periods and the absolute value of the difference between the two succeeding falling periods, in which the period difference absolute value difference related amount is smaller, (9) or (10) if the period difference absolute value ratio divided by
Item 14. A method for detecting an abnormality of a wheel speed sensor according to the above section. 2 before and after
Even when the abnormality of the wheel speed sensor is determined based on the difference between the two rising periods, the influence of the wheel speed can be eliminated by calculating the ratio of the absolute value of the difference between the rising period and the falling period. The same applies to the case of (13). (13) The smaller one of the absolute value of the difference between the two consecutive rising periods and the absolute value of the difference between the two consecutive falling periods, in which the period difference absolute value difference related amount is larger, (9) or (10) if the period difference absolute value ratio divided by the value is smaller than the set period difference absolute value ratio
Item 14. A method for detecting an abnormality of a wheel speed sensor according to the above section. (14) The wheel speed according to any one of (1) to (13), wherein the sensor abnormality is detected based on the fact that the sign of the difference between the rising periods of the successive pulses is opposite to that of the preceding pulse. Sensor abnormality detection method. If a sensor abnormality occurs and an abnormal pulse is generated near the rising edge of a normal pulse, the lengths of the two rising cycles that alternate with each other alternately change, and the sign of the difference between the rising cycles of the preceding and following pulses changes. Is reversed. According to this method, the sensor abnormality can be detected more accurately. As described in (15), the same applies to a case where a sensor abnormality occurs and an abnormal pulse occurs near the fall of a normal pulse. (15) The wheel according to any one of (1) to (14), wherein a sensor abnormality is detected based on the fact that the sign of the difference between the falling periods of the preceding and following pulses is opposite to that of the preceding pulse. Speed sensor abnormality detection method. (16) A sensor abnormality is detected based on the fact that the absolute value of the difference between the preceding and following sums of the rising periods of the preceding and following pulses is equal to or smaller than a set value. One of the items (1) to (15) 4. A method for detecting an abnormality of a wheel speed sensor according to the item 1. If a sensor abnormality occurs and an abnormal pulse occurs near the rising edge of a normal pulse, the absolute value of the difference between the preceding and following sums of the rising periods of the consecutive pulses becomes equal to or less than the set value. In addition, the sensor abnormality can be detected more accurately. As described in (17), the same applies when a sensor abnormality occurs and an abnormal pulse occurs near the falling edge of a normal pulse. (17) A sensor abnormality is detected based on the fact that the absolute value of the difference between the preceding and following sums of the falling periods of the preceding and following pulses is equal to or less than a set value. 4. A method for detecting an abnormality of a wheel speed sensor according to any one of the above. By utilizing the wheel speed sensor abnormality detection method described in the above item (1), a wheel speed detection method described in the following item (18) and a wheel slip control method described in the item (19) can be obtained. (18) A wheel speed detecting step of detecting a wheel speed based on a cycle of a pulse signal generated by a wheel speed sensor with rotation of the wheel, and a fluctuation state of a rising period and a falling period of the pulse signal A wheel speed detection prohibiting step of prohibiting the execution of the wheel speed detecting step when the difference situation from the permissible situation deviates from the allowable situation. Any of the wheel speed sensor abnormality detection methods described in (2) to (17) can be applied to the present wheel speed detection method. (19) a wheel speed detecting step of detecting a wheel speed based on a cycle of a pulse signal generated by a wheel speed sensor in accordance with a rotation speed of the wheel, and the step of detecting a wheel speed based on the wheel speed detected in the wheel speed detecting step. A slip control step for controlling wheel slip; and a slip control for changing an operation state of the slip control step when a difference between a rising situation and a falling cycle of the pulse signal deviates from an allowable situation. A wheel slip control method including a changing step. Any of the wheel speed sensor abnormality detection methods described in (2) to (17) can be applied to the wheel slip control method.

Another object of the present invention is to provide a wheel speed detecting device capable of detecting a wheel speed sensor abnormality in which an abnormal pulse is generated near a rising or falling edge of a normal pulse. ) And (21). (20) A wheel speed sensor for generating a pulse signal whose cycle changes in accordance with the rotation speed of the wheel, a wheel speed calculating means for calculating a wheel speed based on the cycle of the pulse signal, and a rising cycle of the pulse signal A wheel speed detection device including: a sensor abnormality detecting unit that detects a sensor abnormality based on a difference between the fluctuation state and the fluctuation state of the fall period deviating from an allowable state. (Claim 3) In the device according to the present invention, the sensor abnormality is detected in the same manner as the sensor abnormality detection by the sensor abnormality detection method described in (1). In addition, any of the features of the wheel speed sensor abnormality detection method described in (2) to (17) can be applied to the present wheel speed detection device. (21) Including a sensor abnormality notification device that reports a sensor abnormality in response to the sensor abnormality detection of the sensor abnormality detection means (2
The wheel speed detecting device according to the item (0).

Still another object of the present invention is to change the operation state of the wheel slip control when the sensor is abnormal.
This problem is solved by the wheel slip control device described in (22). (22) a wheel speed sensor that generates a pulse signal whose cycle changes in accordance with the rotation speed of the wheel, and wheel speed calculation means that calculates the wheel speed based on the cycle of the pulse signal generated by the wheel speed sensor; A slip control unit for controlling the slip of the wheel based on the wheel speed calculated by the wheel speed calculation unit, and a difference between a rising condition and a falling condition of the pulse signal in an allowable condition. A slip control changing means for changing an operation state of the slip control means when the vehicle slips off. (Claim 4) "Changing the operating state" means, for example, that the wheel speed calculated based on the output signal of the sensor in which the abnormality is detected is not used for estimating the vehicle body speed. For the detected wheel, the same control as that of the wheel whose sensor is normal is performed, and control is not performed for the wheel or all the wheels where the sensor abnormality is detected. The slip control includes, for example, anti-lock control that suppresses excessive slip of the wheels during braking and prevents the wheels from locking, suppresses excessive slip of the drive wheels during vehicle driving, and secures the driving force. There are traction control, vehicle stability control performed to secure the steering stability of the vehicle, and the like. In any control, the slip state of the wheel or the like is obtained based on the wheel speed calculated by the wheel speed calculating means,
Since the control is performed, if the wheel speed of any of the wheels becomes abnormal, it cannot be expected that appropriate control will be performed on that wheel. Further, when the vehicle speed used for detecting the slip state is obtained based on the wheel speeds of a plurality of wheels, if the wheel speed of one wheel becomes abnormal, the vehicle speed becomes abnormal, In some cases, the detection of the slip state may become abnormal and control may not be performed properly. On the other hand, if the wheel speed sensor becomes abnormal,
By changing the operation state of the slip control means, it is possible to avoid execution of control based on abnormal wheel speed, and to prevent a reduction in control accuracy. In addition,
Any of the features of the wheel speed sensor abnormality detection method described in (2) to (17) can be applied to the wheel slip control device.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a vehicle brake system provided with a wheel speed detecting device and a wheel slip control device according to an embodiment of the present invention, in which a wheel speed sensor abnormality detecting method according to the present invention is implemented, will be described. It will be described based on. In FIG. 1, reference numeral 10 indicates a master cylinder.
The master cylinder 10 is a tandem type in which two independent pressure chambers are arranged in series. The master cylinder 10 is linked to a brake pedal 14 as a brake operating member via a booster (not shown).
Hydraulic pressure of the same height is mechanically generated in each pressurizing chamber by the depression force of the brake pedal 14. The depression of the brake pedal 14 is detected by a brake switch 15.

In one of the pressurizing chambers of the master cylinder 10, the brake cylinders 2 of the left and right front wheels 16, which are non-driven wheels, are provided.
0, the left and right rear wheels 18 which are drive wheels are provided in the other pressurizing chamber.
Are connected respectively. In other words, this brake system is of a two-system system of front and rear. The left and right front wheels 16 are subject to antilock control, and the left and right rear wheels 18 are subject to both antilock control and traction control.

First, the configuration of the front wheel brake system will be described. In the front wheel brake system, the master cylinder 10
Are connected to the brake cylinder 20 by a main fluid passage 22 which extends from the master cylinder 10 and branches off in a forked manner. Each of the branch portions of the main fluid passage 22 is provided with a pressure-intensifying valve 24, which is a normally-open electromagnetic on-off valve. The pressure-increasing condition allows the flow of brake fluid from the master cylinder 10 toward the brake cylinder 20 in the open state. Realize.
Each of the pressure increasing valves 24 is connected to a bypass fluid passage 26, and each of the bypass fluid passages 26 is provided with a check valve 28 for returning brake fluid. Reservoir liquid passages 30 extend from the portions between the pressure boosting valves 24 and the brake cylinders 20 of the branch portions of the main liquid passage 22 to reach the reservoirs 32. Each reservoir liquid passage 30 is provided with a pressure reducing valve 34 which is a normally-closed electromagnetic on-off valve, and realizes a reduced pressure state in which the flow of the brake liquid from the brake cylinder 20 toward the reservoir 32 in the open state is permitted. That is, the brake cylinder pressures of the left and right front wheels 16 can be controlled independently of each other. The brake fluid discharged from the brake cylinder 20 to the reservoir 32 is pumped up by a pump 38 provided in a pump fluid passage 36, and the main fluid passage 2
The pressure is returned between the second master cylinder 10 and each pressure increase valve 24.

A wheel speed sensor 40 is provided for each of the left and right front wheels 16. Wheel speed sensor 40
As shown in FIG. 2, the sensor rotor 42 made of a magnetic material,
An electromagnetic pickup 44, which is a kind of magnetic pickup serving as a sensor pickup, and a waveform shaping circuit 46 are provided. The sensor rotor 42 is fixed to an axle hub together with a disc rotor (not shown), rotates with the front wheel 16, and has a number of teeth 48 on one circumference centered on the wheel rotation axis.

The electromagnetic pickup 44 is attached to a non-rotating member (not shown) (for example, a bearing box that rotatably supports an axle integrated with an axle hub via a bearing) and is disposed near the sensor rotor 42. . The electromagnetic pickup 44 includes a coil 50 and a permanent magnet 52. A head 53 protrudes from the tip of the permanent magnet 52 and faces the portion of the sensor rotor 42 where the teeth 48 are provided. When the sensor rotor 42 rotates with the rotation of the front wheel 16, the teeth 48 Coil 50 according to the passage
The density of the magnetic flux passing through the inside changes, as shown in FIG.
An AC voltage is generated in the coil 50. Since the frequency of the AC voltage is proportional to the rotation speed of the front wheels 16, the wheel speed can be detected based on the cycle of the AC voltage.

The AC voltage is supplied to a waveform shaping circuit 4 shown in FIG.
The computer 5 is converted into a pulse signal by the controller 6 and forms a main component of a controller 54 for calculating the wheel speed and the like (see FIG. 1).
6 (see FIG. 1). In the waveform shaping circuit 46, the AC voltage is compared with a threshold, and a rectangular pulse signal having a high level in a region where the AC voltage is larger than the threshold is generated. The cycle of this pulse signal is inversely proportional to the rotation speed of the sensor rotor 42. The computer 56 has a PU (processing unit) 60, a ROM 62, a RAM 64, and a bus 66 connecting them. An I / O port 58 is connected to the bus 66, and a pulse signal input to the I / O port 58 is P
Processed by U60.

Next, the configuration of the rear wheel brake system will be described.
In the rear wheel brake system, as in the case of the front wheel brake system, the master cylinder 10
Are connected by a main liquid passage 70 branched into two branches. Each of the branch portions of the main liquid passage 70 is provided with a pressure increasing valve 72 and a reservoir liquid passage 74. Each of the pressure increasing valves 72 is provided with a bypass liquid passage 78 having a check valve 76, and each of the reservoir liquid passages 74 is provided with a corresponding one of them. A pressure reducing valve 80 is provided. That is, the brake cylinder pressures of the left and right rear wheels 18 can be controlled independently of each other. A reservoir 82 is provided at the tip of each reservoir liquid passage 74. The brake fluid in the reservoir 82 is pumped up by a pump 86 provided in a pump fluid passage 84 and returned between the master cylinder 10 in the main fluid passage 70 and each of the pressure increasing valves 72. Reference numeral 88 denotes an orifice for reducing pulsation of the pump 86.

The left and right rear wheels 18 are subjected to traction control. The traction control is performed by operating the pump 86 and making the pump 86 function as a pressure source. Therefore, unlike the front wheel brake system, the master cylinder 10 and the pump
Master cylinder cut valve 90
And a bypass fluid passage 94 that bypasses the master cylinder cut valve 90 and has a check valve 92 is provided.

An auxiliary liquid passage 96 for connecting a portion of the main liquid passage 70 between the master cylinder 10 and the master cylinder cut valve 90 with the reservoir 82 is provided. Control valve 98
Is provided. Further, a relief fluid passage 100 extends from a portion of the pump fluid passage 84 on the discharge side of the pump 86, and extends from a portion of the auxiliary fluid passage 96 between a connection position of the main fluid passage 70 and a pilot-type inflow control valve 98. Has reached. This relief liquid passage 100 has a relief valve 102
Is provided. Further, an orifice 104 is provided in a portion of the auxiliary liquid passage 96 between the connection position of the main liquid passage 70 and the connection position of the relief liquid passage 100.

When the master cylinder cut valve 90 is closed, the brake cylinder 21 and the pump 86 are closed.
From the master cylinder 10, and the pump 86 can increase the pressure of the brake cylinder 21. The pilot type inflow control valve 98 is connected to the reservoir 82
And is kept open during the traction control to allow the brake fluid to flow from the master cylinder 10 to the reservoir 82. The auxiliary fluid passage 96 is a passage for returning the surplus brake fluid discharged into the relief fluid passage 100 to the reservoir 82, and
This is a passage through which the brake fluid from the tank flows into the reservoir 82. The orifice 104 provides a flow path resistance to the brake fluid flowing from the master cylinder 10 into the auxiliary fluid passage 96, so that replenishment of the brake fluid from the master cylinder 10 to the reservoir 82 is prevented from being performed more than necessary. A brake system including the master cylinder cut valve 90, the pilot type inflow control valve 98 and the like is disclosed in Japanese Patent Application Laid-Open No. 8-104214.
Since this is the same as the brake system described in Japanese Patent Application Laid-Open Publication No. H10-207, and is not directly related to the present invention, detailed description is omitted.

A wheel speed sensor 110 is provided for each of the left and right rear wheels 18. The wheel speed sensors 110 are configured in the same manner as the wheel speed sensors 40. The sensor rotor is fixed to the axle hub together with the disk rotor and rotates together with the rear wheel 18, and the electromagnetic pickup is mounted on a non-rotating member, for example, an axle tube. Installed.

The pulse signal generated by the wheel speed sensor 110 is, like the pulse signal generated by the wheel speed sensor 40, the I / O signal of the controller 54 for calculating the wheel speed and the like.
Input to the O port 58. The ROM 62 of the computer 56 of the controller 54 for calculating the wheel speed etc.
Calculation of wheel speeds and the like, and abnormality detection of wheel speed sensors 40 and 110, such as wheel speed etc. calculation processing, rise cycle ratio integration value calculation processing, fall cycle ratio integration value calculation processing etc. shown in the flowcharts in FIGS. And the like are stored.

As shown in FIG. 6, the RAM 64 of the computer 56 has a rise time memory 111, a last rise cycle memory 112, a last rise cycle memory 114, a current rise cycle memory 116, a rise cycle ratio integration memory 117, Rise period ratio integral value memory 118, fall time memory 119, last-before-last fall period memory 120, last fall period memory 122, current fall period memory 124, fall period ratio integral memory 126, fall period ratio integral value A memory 128, a wheel speed memory 130, a wheel acceleration memory 132, a vehicle speed memory 134, and a sensor abnormality flag 136 are provided together with a working memory. These memories 112 to 134
The sensor abnormality flag 136 is shown one by one in FIG. 6, but actually four wheel speed sensors 40,
110, four wheels 16, 18 are provided for each. The sensor abnormality flag 136 indicates abnormality of the wheel speed sensors 40 and 110 when set, and indicates normal when reset. By setting and resetting the sensor abnormality flag 136, it is possible to determine which wheel provided with the wheel speed sensor is abnormal. Further, as shown in FIG. 1, a warning lamp 138 for notifying abnormality of the wheel speed sensors 40 and 110 is connected to the wheel speed etc. calculation controller 54, and the control of the wheel speed etc. calculation controller 54 is performed. To turn on and off.

The pressure increasing valves 24, 72 and the pressure reducing valves 34, 8
0, the pump driving motor is connected to the anti-lock control controller 140. This controller 14
Although 0 is not shown, the computer 0 is mainly composed of a computer similarly to the controller 54 for calculating the wheel speed and the like, and various processes for executing the antilock control are stored in its ROM, and PU is stored in the ROM. The antilock control is executed by executing various processes while using the RAM.

Pressure increasing valve 72, pressure reducing valve 8 of rear wheel brake system
0, the master cylinder cut valve 90, and the pump driving motor are connected to a traction control controller 142. Although not shown, the controller 142 is mainly composed of a computer similarly to the controller 54 for calculating the wheel speed and the like, and its ROM stores various processes for executing traction control. The PU executes traction control by executing various processes while using the RAM.

The pressure increasing valves 24, 72, the pressure reducing valves 34, 80, the master cylinder cut valve 90, and the pump driving motor are connected to a vehicle stability control controller 144. The controller 144 is also constituted mainly by a computer, and its ROM stores various processes for executing vehicle stability control, that is, control for obtaining the steering stability of the vehicle.
Executes vehicle stability control by executing various processes while utilizing the RAM.

These antilock control controllers 1
40, a traction control controller 142 and a vehicle stability control controller 144 are connected to the controller 54 for calculating the wheel speed and the like.
Transmission and reception of data and the like necessary for control are performed.

During normal braking, if the driver depresses the brake pedal 14, hydraulic pressure is generated in the master cylinder 10, and in the front wheel brake system, the hydraulic pressure is transmitted to the brake cylinders 20 of the left and right front wheels 16 via the pressure increasing valve 24. The brake is actuated. In the rear wheel brake system, the master cylinder cut valve 90 is open,
The pilot type inflow control valve 98 is closed, and the hydraulic pressure generated in the master cylinder 10 is applied to the master cylinder cut valve 9.
The pressure is transmitted to the brake cylinders 21 of the left and right rear wheels 18 via the pressure-increasing valve 72 and the pressure increase valve 72 to operate the brake.

The anti-lock control is a control for preventing each wheel from locking during braking of the vehicle.
While monitoring the rotation speed of the vehicle and the running speed of the vehicle body, the pressure increasing valves 24 and 72 are in the open state, and the pressure reducing valves 34 and 80 are in the closed state. The pressure increasing valves 24 and 72 and the pressure reducing valves 34 and 80 are also in the closed state. And the pressure increasing valves 24 and 72 are closed, and the pressure reducing valves 34 and 80 are selectively opened. During the antilock control, the master cylinder cut valve 90 is open and the pump 3
8, 86 are operated, and the brake fluid in the reservoirs 32, 82 is pumped up and returned to the main fluid passages 22, 70.

The traction control is a control for suppressing an excessive slip of each of the right and left rear wheels 18 when the vehicle is driven. During the traction control, the master cylinder cut valve 90 is closed and the pump 86 is started.
The brake fluid is pumped from the reservoir 82 and supplied to the brake cylinder 21. When the pump 86 is started, the pilot-type inflow control valve 98 opens, and the master cylinder 10
From the brake fluid into the reservoir 82,
Pump 86 pumps up brake fluid from master cylinder 10. As a result, the hydraulic pressure of the brake cylinder 21 is increased, and the brake is operated to reduce excessive driving torque. Also at the time of traction control, each of the left and right rear wheels 1 as driving wheels via the wheel speed sensors 40 and 110.
The rotation speed of 8 and the running speed of the vehicle body are monitored, and the pressure increasing state, the holding state and the pressure reducing state are selectively realized by the pressure increasing valve 72 and the pressure reducing valve 80.

The vehicle stability control is performed both when driving the vehicle and when braking.
4, 72, and the pressure reducing valves 34, 80 are selectively realized in a pressure-increasing state, a holding state, and a pressure-reducing state, so that the steering stability of the vehicle is ensured. Master cylinder cut valve 9
When the vehicle is driven, the pump 86 is closed and the pump 86 is caused to function as a pressure source. When the brake is applied, the pump 86 is opened and control is performed using the master cylinder 10 as a pressure source.

The wheel speed is used for these controls.
If the iron piece 150 adheres to the head 53 of No. 4, the wheel speed becomes an abnormal value. Based on the flowcharts shown in FIGS. 7, 8, and 9, respectively, the wheel speed sensors 40, 11
An abnormality detection of 0 will be described. When the sensor rotor 42 rotates in the direction indicated by the arrow in FIG. 4, if the iron piece 150 is attached to the downstream edge of the head 53 of the electromagnetic pickup 44 in the sensor rotor rotation direction, when the tooth 48 approaches, the iron piece 150 Is adsorbed to the teeth 48. At this time, an abrupt change in the magnetic flux density occurs, and the AC voltage changes abruptly, causing a large disturbance in the waveform. The sensor rotor 42 rotates while the iron piece 150 is attracted to the tooth 48, and when the tooth 48 separates from the electromagnetic pickup 44, the iron piece 150 is slightly
Move away from Also at this time, a sudden change in magnetic flux density occurs,
The waveform of the AC voltage is disturbed.

If the AC voltage including the disturbance is converted into a pulse signal by the waveform shaping circuit 46, as shown in FIG. 5, the AC voltage generated when the iron piece 150 is attracted by the teeth 48 becomes a threshold value. , And a narrow pulse which is not generated unless the iron piece 150 is attached to the electromagnetic pickup 44 is generated. This narrow pulse occurs every time immediately before the rise of the wide pulse. A normal pulse is divided into two pulses having different periods. However, for convenience,
A narrow pulse is called an abnormal pulse, and a wide pulse is called a normal pulse. An abnormal pulse occurs near the rise of the normal pulse. If the number of pulses increases due to the generation of an abnormal pulse, the value of the wheel speed calculated based on the pulse increases abnormally, causing a decrease in the accuracy of slip control such as antilock control. Iron piece 150
Is attached to the upstream edge of the head 53 in the direction of rotation of the sensor rotor, and an abnormal pulse may be generated near the fall of the normal pulse. In any case, the detected wheel speed is an abnormally large value. become. The disturbance of the waveform of the AC voltage when the tooth 48 separates from the iron piece 150 is often not as large as that at the time of suction, but the disturbance may still cause an abnormal pulse.

The wheel speed is calculated for each of the four wheels 16 and 18 for each set time by executing a calculation process for the wheel speed and the like. If the pulse signal rises and falls during this time, , A rising period ratio integral value calculation process and a falling period ratio integral value calculation process are executed. Hereinafter, these processes will be described.

In the rising period ratio integral value calculation processing
First, in step 21 (hereinafter abbreviated as S21)
Rise cycle T_unThat is, two consecutive
The time interval of the rise of the luz is calculated. Rise of the pulse
The rasp time is provided in the PU 60 of the computer 56.
Determined by timer and stored in rise time memory 111
From the rise time of this pulse to the previous pulse
The rise time of Lus is reduced. Note that the operation
Later, the rise time of this pulse is the rise time of the previous pulse
The rise time is stored in the rise time memory 111 instead of the set time.
It is. Rise cycle T_unIs calculated,
Last rising cycle T stored in cycle memory 114_un-1
Is stored in the rise cycle memory 112 two times before
Rise cycle T_un-2This time, the rising cycle memory 1
This rising cycle T stored in 16 _unRises last time
Last rise cycle T stored in cycle memory 114_un-1
And the rising cycle T calculated this time_unBut this time
Is stored in the cycle memory 116.

Next, S22 is executed, and the rising cycle T _un calculated this time is compared with the rising cycle T calculated last time.
A determination is made whether it is greater than _un-1 . The value stored in the rising cycle memory 114 last time is subtracted from the value stored in the rising cycle memory 116 this time. If the current rising cycle T _un is longer than the previous rising cycle T _un-1 , the determination result of S22 is YES and S23 is executed, and the current rising cycle T _un is changed to the previous rising cycle T _un.
The rising period ratio RT _un is calculated by dividing by _un-1 . If the current rise cycle T _un is less than the previous rise cycle T _un-1 , S24 is executed, and the last rise cycle T _un-1 is executed.
There is divided by this rising period T _un, rising period ratio RT _un is calculated.

[0032] Then S25 is the integral value IRT _u period ratio RT _un rises and the operation is executed, it is stored in the rising period ratio integration-value memory 118. This integral value IRT
_u is a predetermined number (A) of rising cycle ratios RT
It is the sum of _un . The integration is performed using the rising period ratio integration memory 1
This is performed by obtaining the sum of all the rising period ratios stored in the memory 17. Rise period ratio integration memory 117
In the state in which A period ratios are stored, each time the period ratio is newly calculated, the latest period ratio becomes the rising period ratio integral instead of the oldest period ratio among the A period ratios. Is stored in the storage memory 117. The oldest period ratio is replaced with the latest period ratio, and the rising period ratio integration memory 117 stores the latest A rising period ratios. Therefore, the integration value calculated in S25 is always the sum of the latest A period ratios, and is a value well corresponding to the current situation.

The fall period ratio integral value calculation process is executed similarly to the rise period ratio integral value calculation process, and the fall period T _dn , fall period ratio _RTdn, and fall period ratio integral value IRT _d are calculated. You. Note that the rising period ratio integral value calculation process and the falling period ratio integral value calculation process are performed in four steps.
This is performed based on the pulse signals of the respective wheel speed sensors 40 and 110.

In the processing for calculating the wheel speed and the like, after the initial setting in S1, that is, the resetting of the flag provided in the RAM 64, the clearing of the memory, and the like are performed, S2 is executed, and the wheel speed sensors 40 and 110 generate signals. Calculation of wheel speed and wheel acceleration is performed based on the pulse signal. These calculations are performed at set time intervals (for example, 6 ms).
It is performed every time. The wheel speed is calculated based on a pulse signal obtained within a set time, and is represented by an hourly speed (km / h).

After calculating the wheel speed, the wheel speed sensor 40,
An abnormality detection of 110 is performed. Of the electromagnetic pickup 44
A normal pulse rises due to the attachment of the iron piece to the head 53.
Sensors that generate abnormal pulses near the edge or near the falling edge
If an abnormality occurs, the following three situations occur. Sensor rotor of head 53 of electromagnetic pickup 44
The iron piece 150 adheres to the downstream edge in the rotation direction.
The abnormal pulse generated as shown in FIG.
As with normal pulses, the pulse rises regularly and normally.
It occurs near the rise. Therefore, two consecutive startups
The variation of the rolling cycle is the variation of the two consecutive falling cycles.
Larger than the dynamic, the integral of the rise period ratio is the fall period
If the former is divided by the latter, the integral
The value ratio becomes larger than the set value. Conversely, electromagnetic pickup
The upstream edge of the head 53 in the sensor rotor rotation direction of the head 53
Abnormal pulse caused by iron piece 150 adhering to
Is similar to a normal pulse, as shown in FIG.
It occurs regularly and near the falling edge of a normal pulse.
Therefore, the fluctuations of the two falling periods before and after are different from each other.
The rise and fall are larger than the fluctuations of the two rising cycles before and after
The integral value of the period ratio is larger than the integral value of the rise period ratio.
If the former is divided by the latter, the integral value ratio is greater than the set value.
It will be good. Also, the abnormal pulse is near the rising edge of the normal pulse.
, The rise cycle alternates in length, this time
Rise cycle T_unFrom the previous rise cycle T_un-1Subtracted
Value and last rise cycle T_un-1Rise cycle two times before
T_un-2The sign is opposite to the value obtained by subtracting. Abnormal pulse
If it occurs near the falling edge of a normal pulse, the falling period
Indicates that the length changes alternately and the falling period T_dnFrom last time
Fall period T_dn-1Subtracted value and previous fall period T
_dn-1Falling cycle T before_dn-2Positive and negative with the value minus
Is reversed. In addition, the abnormal pulse is near the rise of the normal pulse.
If you grow up next to you, this time the rising cycle T_unAnd the last rise
Period T_un-1And the previous rise cycle T_un-1And reverted before
Rise cycle T_un-2The absolute value of the difference with the sum is smaller than the set value
It will be cheap. An abnormal pulse is near the falling edge of a normal pulse
, This fall period T_dnAnd last fall cycle
T_dn-1And the previous fall period T_dn-1And fall back before
Rolling cycle T _dn-2The absolute value of the difference from the sum with
It becomes.

The calculation processing of the wheel speed and the like is configured such that when any of the above three situations occurs, the wheel speed sensor is determined to be abnormal. Therefore, first, S3
There is executed, the rising period ratio integrated value IRT _u is of whether the falling period ratio integrated value IRT or _d is greater than a determination is made. Here, assuming that the iron piece 150 is attached to the downstream edge of the head 53 of the electromagnetic pickup 44 in the sensor rotor rotation direction and an abnormal pulse occurs near the rising edge of a normal pulse, the rising cycle ratio is greater. Since it is larger than the falling period ratio, the determination result in S3 is YES.

Subsequently, S4 is executed, and the sensor abnormality flag is set.
It is determined whether or not 136 is set.
The sensor abnormality flag 136 is reset by default.
The determination result of S4 is NO, and S5 is executed.
It is. In S5, the current rising cycle T_unFrom last time
Rise cycle T_un-1Subtracted value and last rise cycle T
_un-1Rise cycle T before_un-2Positive and negative with the value minus
It is determined whether or not is reversed.

If the sign is reversed, the decision result in S5 is YES
S6 is executed, and the absolute value of the value obtained by subtracting the sum of the current rising cycle T _un and the previous rising cycle T _un-1 from the sum of the previous rising cycle T _un-1 and the last rising cycle T _un-2 is obtained. It is determined whether the value is smaller than the set value. S5
If any of the determination results in S6 are NO, the wheel speed sensor is not determined to be abnormal.

If the determination results in S5 and S6 are both YES, S7 is executed, and the rising cycle ratio integrated value IRT _{u is obtained.}
Is divided by the falling period ratio integral value IRT _d to obtain the period ratio R
_IR is required. Next, S12 is executed, and the period ratio R
_It is determined whether the _IR is greater than the first set period ratio ratio S _R1 . If the cycle ratio R _IR between the rising cycle ratio integration value and the falling cycle ratio integration value is equal to or _smaller than the first set cycle ratio S _R1 , it is not a sensor abnormality and the determination result in S12 is NO and S15 is executed. It is determined whether or not the sensor abnormality flag 136 has been set. If the abnormality of the wheel speed sensor has not been detected and the sensor abnormality flag 136 has not been set, the determination result of S15 is NO.

The calculation of the wheel speed and the wheel acceleration and the detection of the abnormality of the wheel speed sensor (S2 to S13, S15 to S1)
7) is not shown in the flowchart of FIG.
This is performed for each of the four wheels and the four wheel speed sensors, and thereafter, S14 is executed and the four
The vehicle speed is estimated based on the two wheel speeds.

If the cycle ratio R _IR is larger than the first set cycle ratio S _R1 , the wheel speed sensor is abnormal, the result of determination in S12 is YES, S13 is executed, the warning lamp 138 is turned on, and the driver And the sensor abnormality flag 136 is set. Among the four sensor abnormality flags 136, the sensor abnormality flag 136 provided for the wheel speed sensor in which the abnormality is detected is set. If an abnormality is detected for a plurality of wheel speed sensors, a corresponding sensor abnormality flag 136 is set each time an abnormality is detected for each wheel speed sensor.

If an abnormality is detected in any of the four wheel speed sensors 40 and 110, when the vehicle speed is estimated in S14, the calculation is performed based on the output signal of the wheel speed sensor in which the abnormality is detected. Wheel speed is not used to estimate vehicle speed. When an abnormality of the wheel speed sensor is detected, the anti-lock control controller 140
When performing antilock control, the abnormal wheel speed sensor is checked by referring to the sensor abnormality flag 136, and the wheel speed calculated based on the output signal of the abnormal wheel speed sensor is not used. For a wheel in which a sensor abnormality has been detected, control different from that performed when the wheel speed sensor is normal is performed. For example, if the wheel where the sensor abnormality is detected is one of the front wheels, the same antilock control is performed on the front wheel as on the other front wheel, and similarly, if on one of the rear wheels, the other wheel is on the other side. The same anti-lock control as for the rear wheels is performed. If two or more wheel speed sensors 40 and 110 are attached with iron pieces, the antilock control for all wheels is prohibited.

In the traction control controller 142, if the wheel in which the sensor abnormality is detected is one of the left and right rear wheels 18 that are the driving wheels, when the traction control is performed for the other rear wheel 18, Rear wheel 1
8, the same traction control is performed. If iron pieces adhere to both of the two wheel speed sensors 110, traction control is prohibited. In the vehicle stability control controller 144, if a sensor abnormality is detected even for one wheel, control for all wheels is prohibited.

Once a wheel speed sensor abnormality is detected,
If the sensor abnormality flag 136 is set, the next time S4 is executed, the determination result is YES and S7,
S12 is executed. If the iron piece 150 is still attached to the head 53 and the abnormal pulse continues to be generated, S12
Is YES. On the other hand, for example, if the iron piece 150 is removed from the head 53 and no abnormal pulse is generated, the rising period ratio decreases, and the period ratio ratio R _IR between the rising period ratio integration value and the falling period ratio integration value decreases. As a result, the period ratio R _IR becomes equal to or less than the first set period ratio S _R1 , and S1
The determination result of 2 is NO. Then, step S15 is executed to determine whether or not the sensor abnormality flag 136 has been set.
Step 16 is executed to determine whether or not the cycle ratio R _IR is smaller than the second set cycle ratio S _R2 . Period ratio _RIR is 2nd
If it becomes smaller than the set cycle ratio S _R2, it is determined that the iron pieces have been adhered. The second set period ratio S _R2 is smaller than the first set period ratio S _R1 , and the elimination of the abnormality is reliably detected. If the determination result in S16 becomes YES, S17 is executed, the warning lamp 138 is turned off, and the sensor abnormality flag 136 is reset. However,
Abnormalities are detected for a plurality of wheel speed sensors,
When the abnormality is eliminated for a part of them, the warning lamp 138 is turned on by the abnormality detection for the wheel speed sensor that does not eliminate the abnormality, and is substantially kept on.

The head 53 of the electromagnetic pickup 44
Iron piece 15 on the upstream edge in the sensor rotor rotation direction.
When 0 is attached and an abnormal pulse occurs near the falling edge of the normal pulse, the determination result of S3 becomes NO because the falling period ratio is larger than the rising period ratio.
Steps 8 to S12 are executed to detect a sensor abnormality. After detecting the sensor abnormality, S2, S3, S8, S11
Steps S14 to S14 are executed, and if the iron piece 150 is removed from the head 53, S15 and S16 are executed, and the detection of the abnormality is detected.

As is clear from the above description, in the present embodiment, the S of the controller 54 for calculating the wheel speed etc.
The part executing the part represented by 2 constitutes the wheel speed calculating means, and the part executing the parts represented by S3 to S12 using various memories provided in the RAM 64 constitutes the sensor abnormality detecting means. , S16 constitute a sensor abnormality elimination detecting means. Also,
Each of the anti-lock control controller 140, the traction control controller 142, and the vehicle stability control controller 144 executes a flowchart of processing stored in the ROM, and a part that controls wheel slip based on the wheel speed is a slip control. The part that changes the operation state of the slip control means when an abnormality of the wheel speed sensor is detected constitutes the slip control change means.

In the above embodiment, the abnormality of the wheel speed sensor is detected based on the period ratio. However, the abnormality may be detected based on the period difference. In this case, as shown in FIG. 11, the rise time memory 158 and the last rise cycle memory 16 are stored in the RAM 64 of the computer of the arithmetic controller for the wheel speed and the like.
0, current rise cycle memory 162, rise cycle difference absolute value integration memory 164, rise cycle difference absolute value integrated value memory 166, fall time memory 167, previous fall cycle memory 168, current fall cycle memory 170,
Fall period difference absolute value integration memory 172, Fall period difference absolute value integration value memory 174, Wheel speed memory 17
6, wheel acceleration memory 178, vehicle speed memory 180,
A sensor abnormality flag 182 is provided. The memories 158 to 182 and the sensor abnormality flag 182 are provided for each of the four wheel speed sensors 40, 110 and the four wheels 16, 18. The ROM stores wheel speed etc. calculation processing, rise cycle difference absolute value integration value calculation processing, and fall cycle difference absolute value integration value calculation processing shown in the flowcharts of FIGS. 12, 13 and 14, respectively. as shown in 15 and 16, the setting table, the threshold S _n of sensor normal detection in accordance with the wheel speed V _W to set the threshold S _a for the sensor abnormality detection in accordance with the wheel speed V _W Table is stored.

In the rising period difference absolute value integral value calculation processing, the rising period T _un is calculated in S51, and then the absolute value | DT _un | of the difference between two successive rising periods is calculated in S52. This time rise cycle T
the absolute value of the value obtained by subtracting the period T _{un -1} rising last from _un is being computed. Then, S53 is executed, the absolute value of the rising period difference | DT _un | integrated value IDT _u is calculated. In this integration, similarly to the integration of the period ratio in the above embodiment, the number of period difference absolute values | DT _un | to be integrated is determined to be A. The fall period difference absolute value integral value calculation processing is executed in the same manner, and the absolute value | DT _un | of the difference between two successive fall periods and the fall period difference absolute value integrated value ID
_Td is calculated.

In the processing for calculating the wheel speed, etc., S41,
S42 is executed in the same manner as S1 and S2 of the embodiment,
Wheel speed and wheel acceleration are calculated, and the wheel speed memory 17
6, stored in the wheel speed memory 178. Then S43
There is executed, the absolute value of the difference between the rising period difference absolute value integration value IDT _u and falling period difference absolute value integration value IDT _d (period difference referred to an absolute value integration value difference absolute value) is calculated. Subsequently, S44 is executed to determine whether or not the sensor abnormality flag 182 is set. Sensor abnormality flag 1
82 is reset in the initial setting, and when S44 is performed for the first time, the determination result is NO and S
At 45, a determination is made as to whether the wheel speed sensor is abnormal. This determination is the period difference absolute value integration value difference absolute value is made by determining whether greater than a threshold value, at the time of judgment, read threshold S _a which corresponds to the wheel speed V _w from the table shown in FIG. 15 It is.

This threshold value is set smaller as the wheel speed increases. As shown in FIG. 17, taking an example in which an iron piece adheres to the downstream edge in the sensor rotor rotation direction of the head of the electromagnetic pickup, as shown in FIG. This is because the absolute value of the difference between the integrated value of the absolute value of the difference between the two rising periods and the integrated value of the absolute value of the difference between the successive falling periods becomes smaller. If the cycle difference absolute value integral value difference absolute value is larger than the threshold value, it indicates that the wheel speed sensor is abnormal, and the determination result in S45 becomes YES, and
46 is executed in the same manner as in S13 of the above embodiment. If the cycle difference absolute value integrated value difference absolute value is equal to or smaller than the threshold value, the wheel speed sensor is not abnormal, and the determination result in S45 is NO. After the calculation of the wheel speed and the wheel acceleration for all four wheels and the determination of the sensor abnormality are performed, S47 is executed to estimate the vehicle speed.

Once the abnormality of the wheel speed sensor is detected, the next time S44 is executed, the determination result is YES and S48 is executed to determine whether or not the wheel speed sensor is normal. Is determined. This determination period difference absolute value integration value difference absolute value is made by whether the threshold S or less than _n for detecting normal sensor. This threshold value is set smaller as the wheel speed is higher, and is set smaller than the sensor abnormality detection threshold value for the same wheel speed, similarly to the sensor abnormality detection threshold value. I have. At the time of determination, a threshold value corresponding to the wheel speed is read from a table stored in the ROM. The pulse signal can be normally obtained due to the separation of the iron pieces, etc. If the difference is small, the determination result in S48 becomes YES and S49 is executed, the warning lamp 138 is turned off, and the sensor abnormality flag 182 is reset. Is done.

In the above-described embodiment, the sensor rotor and the electromagnetic pickup are provided to be exposed to the outside. In particular, the present invention is particularly effective because iron pieces are easily adhered. In some cases, the sensor rotor and the electromagnetic pickup are provided in a space shielded from the outside inside the cylindrical member arranged to be relatively rotatable. In this case, the inside of the tubular member, the sensor rotor, and the electromagnetic pickup are sufficiently cleaned at the time of assembly to remove foreign matters such as iron pieces, but still rarely remain, and the iron pieces adhere to the electromagnetic pickup during traveling. It is possible. Therefore, even in a vehicle in which the sensor rotor and the electromagnetic pickup are provided in the internal space as described above,
It is effective to detect the adhesion of the iron piece as in the above embodiment.

Further, in each of the above-described embodiments, the cycle period is calculated by integrating the rising period ratio and the falling period ratio of a plurality of pairs, or by integrating the rising period difference and the falling period difference of a plurality of pairs. Although the ratio and the period difference are averaged, they may be averaged by other means. For example, in acquiring the latest cycle ratio average value, a coefficient is applied to each of the past cycle ratio average value and the latest cycle ratio. This coefficient is, for example, 3
/ 4, and 1/4 for the latest period ratio. The latest period ratio average value obtained in this manner is used as the past period ratio average value with respect to the next calculated latest period ratio, and the latest period ratio average value is similarly obtained. In this way, a period ratio suitable for the current state is obtained while considering the past period ratio, and the influence of the past can be increased or decreased by setting the coefficient. this is,
It is a kind of digital filter, and stores a plurality of past cycle ratios, such as a rising period ratio integrating memory 117 and a falling period ratio integrating memory 126, as in the above embodiment.
Is unnecessary, and the operation time of the average value of the period ratio can be shortened.

In each of the above-described embodiments, even if the set number (A) of the rising cycle ratio, the falling cycle ratio, the absolute value of the rising cycle difference, and the absolute value of the falling cycle difference are not integrated, the sensor abnormality is not detected. Although the detection is performed, the detection of the sensor abnormality may be performed after the value of the set number is integrated.

Further, in the embodiment shown in FIGS. 11 to 17, similarly to the embodiment shown in FIGS. 1 to 10, the sign of the difference between the rising periods (falling periods) of the successive pulses is the same. Is the opposite,
At least one of the fact that the absolute value of the difference of the sum of the rising periods (falling periods) of the preceding and succeeding pulses is equal to or smaller than a set value may be used as the condition for sensor abnormality detection. In the embodiments shown in FIGS. 1 to 10, it is not essential that the above conditions are set as conditions for detecting a sensor abnormality, and at least one of them may be omitted.

Further, once an abnormality of the wheel speed sensor occurs, the detection of the elimination of the abnormality is performed based on whether or not the period ratio integral value ratio and the period difference absolute value integral value difference have become smaller than threshold values. However, in addition to the above, the condition that the difference between the rising and falling periods (falling periods) of the preceding and succeeding pulses is the same but the sign is the same may be used as the condition for detecting the abnormality of the sensor.

In the above-described embodiment, dedicated controllers are provided for calculation of wheel speed and the like, antilock control, traction control, and vehicle stability control. However, a common controller may be used.

Further, in the above-described embodiment, the ratio of the ratio of two successive rising periods to the ratio of two successive falling periods (period ratio ratio), the difference between the two successive rising periods and the phase The sensor abnormality is detected based on the difference between the two successive falling periods (period difference), but the sensor abnormality is detected based on the period ratio difference or the period difference ratio. You may do so.

In the above embodiment, the wheel speed is represented by the hourly speed.
It may be represented by a rotation speed or a rotation speed.

Further, in the above embodiment, the ROM 62 of the computer 56 is not removable from the main body of the computer 56, but the processing shown in FIGS. 7 to 9 and the processing shown in FIGS. May be recorded on a removable recording medium. The removable recording medium is, for example, a magnetic disk, an optical disk, or the like.

Further, the present invention can be applied to a wheel speed detecting device and a wheel slip control device provided in a vehicle in which all of a plurality of wheels are driving wheels, and the method according to the present invention is implemented in these devices. can do. Furthermore, the present invention can be implemented in a mode in which the combination of the components of each of the above embodiments is changed. In addition, without departing from the scope of the claims, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a vehicle brake system that includes a wheel speed detection device and a wheel slip control device according to an embodiment of the present invention and executes a wheel speed sensor abnormality detection method according to the present invention.

FIG. 2 is a diagram showing a wheel speed sensor, which is a component of the wheel speed detection device, together with a computer of a controller for calculating wheel speed and the like.

FIG. 3 is a diagram showing an AC voltage and a pulse signal when teeth of a sensor rotor pass through an electromagnetic pickup in the wheel speed sensor.

FIG. 4 is a diagram for explaining a disturbance of an AC voltage when an iron piece adheres to an electromagnetic pickup in the wheel speed sensor.

FIG. 5 is a diagram illustrating conversion of the AC voltage shown in FIG. 4 into a pulse signal.

FIG. 6 is a diagram schematically showing a portion of the RAM of the computer that is relevant to the present invention.

FIG. 7 is a flowchart illustrating a calculation process of a wheel speed and the like stored in a ROM of the computer.

FIG. 8 is a flowchart showing a rising period ratio integral value calculation process stored in a ROM of the computer.

FIG. 9 is a flowchart showing a fall period ratio integral value calculation process stored in a ROM of the computer.

FIG. 10 is a diagram showing pulses generated when an iron piece adheres to the head of the electromagnetic pickup of the wheel speed sensor.

FIG. 11 shows another embodiment of the present invention, in which the wheel speed detecting device and the wheel speed etc. calculation controller of the wheel slip control device, in which the wheel speed sensor abnormality detecting method according to the present invention is implemented, are included in the computer RAM. FIG. 3 schematically illustrates a portion that is relevant to the present invention.

FIG. 12 is a flowchart showing calculation processing of wheel speed and the like stored in a ROM of the computer.

FIG. 13 is a flowchart showing a rising cycle difference absolute value integral value calculation processing stored in a ROM of the computer.

FIG. 14 is a flowchart showing a fall period difference absolute value integral value calculation process stored in a ROM of the computer.

FIG. 15 is a diagram showing a table for setting a wheel speed sensor abnormality detection threshold value stored in a ROM of the computer in accordance with a wheel speed;

FIG. 16 is a diagram showing a table for setting a threshold value for normal detection of a wheel speed sensor stored in a ROM of the computer in accordance with a wheel speed;

FIG. 17 is a diagram illustrating a difference in the length of the rising cycle and the falling cycle of the pulse signal of the wheel speed sensor depending on the level of the wheel speed.

[Explanation of symbols]

16: Front wheel 18: Rear wheel 40: Wheel speed sensor
42: Sensor rotor 44: Electromagnetic pickup 46: Waveform shaping circuit 5
3: Head 54: Controller for calculating wheel speed etc.
110: Wheel speed sensor 140: Antilock control controller 142: Traction control controller 144: Vehicle stability control controller

Claims (4)

[Claims] 1. A method for detecting an abnormality of a wheel speed sensor that generates a pulse signal whose cycle changes in accordance with a rotation speed of a wheel, comprising: a method of changing a rising period of the pulse signal and a change of a falling period of the pulse signal. A wheel speed sensor abnormality detection method, wherein a sensor abnormality is detected based on a difference from the above method. 2. The difference between the manner in which the rising period varies and the manner in which the falling period varies relates to the difference between the ratio of two successive rising periods and the ratio of two successive falling periods. 2. The method according to claim 1, wherein the period ratio difference related quantity is defined by
4. A method for detecting an abnormality of a wheel speed sensor according to the item 1. 3. A wheel speed sensor for generating a pulse signal whose cycle changes according to the rotation speed of the wheel; a wheel speed calculating means for calculating a wheel speed based on the cycle of the pulse signal; A wheel speed detection device, comprising: sensor abnormality detection means for detecting a sensor abnormality based on a difference between the period fluctuation state and the fall period fluctuation state deviating from an allowable state. 4. A wheel speed sensor for generating a pulse signal whose cycle changes in accordance with the rotation speed of a wheel, and a wheel speed calculating means for calculating a wheel speed based on a cycle of the pulse signal generated by the wheel speed sensor. A slip control means for controlling the slip of the wheel based on the wheel speed calculated by the wheel speed calculation means; and a difference between a rising cycle and a falling cycle of the pulse signal is allowable. A slip control changing means for changing an operation state of the slip control means when the situation deviates.