JP2004132895A - Rotor tooth missing detection device for wheel speed sensor - Google Patents

Abstract

An object of the present invention is to detect a missing tooth of a signal rotor with high accuracy.
An electromagnetic pickup generates one pulse period t based on a pulse signal output each time a tooth formed on a signal rotor that rotates integrally with a wheel is detected, and two one-pulse periods that are successive to each other are generated. The one-pulse time ratio FRPLS is calculated from the ratio of t (-1) and t (S3), and it is first determined that the one-pulse time ratio FRPLS is in an abnormal region (about 0.4 ≦ FRPLS ≦ about 0.6). (S7, S11), the 1-pulse time ratio normal counter FRCNT is cleared (S13), and then the 1-pulse time ratio FRPLS calculated again based on the pulse signal when passing through the same part of the signal rotor is obtained again. If it is determined that it is in the abnormal region, the tooth missing counter FRGCNT is incremented (S8), and the tooth missing counter FRGCNT is set to the set value GCNTo. When determines that missing teeth occurs in signal rotor (S9, S10).
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to detection of tooth missing of a signal rotor that rotates integrally with a wheel, and more particularly to a rotor tooth missing detecting device of a wheel speed sensor that detects tooth missing based on an output signal from a wheel speed sensor.
[0002]
[Prior art]
Generally, in the driving force distribution control of a four-wheel drive vehicle, the distribution of the driving force to the front and rear wheels is controlled based on the wheel speed of each wheel. In an ABS (antilock brake system) device, the wheel speed at the time of a brake operation is controlled. The anti-skid control is performed based on the detected skid state of the brake wheels based on the detected skid state.
[0003]
In this case, the wheel speed of each wheel is calculated based on the output signal from the wheel speed sensor. The wheel speed sensor includes a signal rotor that rotates integrally with the wheel, and an electromagnetic pickup provided on the outer periphery of the signal rotor. Around the signal rotor, a number of teeth having a magnetic material are formed at equal intervals, and when the signal rotor rotates integrally with the wheels, from the electromagnetic pickup, as the teeth formed on the signal rotor pass, A pulse signal for detecting the teeth is output, and the wheel speed is calculated from the cycle of the pulse signal.
[0004]
At this time, for example, if the signal rotor has chipped teeth, the pulse signal is not output even if the part where the chipped teeth pass on the electromagnetic pickup, so the calculated wheel speed is calculated before and after that. As a result, the value suddenly drops compared to the wheel speed, and erroneous control is performed.
[0005]
Therefore, various techniques have been proposed for detecting missing teeth of the signal rotor and preventing erroneous control. For example, in Japanese Patent Application Laid-Open No. 2001-165948, a pulse cycle of a pulse signal output from a wheel speed sensor is set as an intermediate pulse cycle, and a pulse cycle before and after the intermediate pulse cycle (front and rear pulse cycle) is measured. A technique is disclosed in which the ratio between the average value of the preceding and following pulse periods and the intermediate pulse period is obtained, and when the ratio is equal to or more than a predetermined value, it is determined that the signal rotor has missing teeth.
[0006]
That is, in this prior art, as shown in FIG. 5 (a), when there is no tooth missing in the signal rotor, the pulse signals are output at substantially equal intervals. When measuring the period between them, the intermediate pulse period T1 and the preceding and following pulse periods T0 and T2 have substantially the same value. On the other hand, as shown by a broken line in FIG. 3B, when tooth missing occurs, the intermediate pulse period T1 is approximately three times as long as the preceding and following pulse periods T0 and T2. Therefore, the presence or absence of tooth chipping is detected by sequentially measuring the pulse period based on the pulse signal at the time of traveling at a constant speed.
[0007]
[Patent Document 1]
JP 2001-165948 A
[0008]
[Problems to be solved by the invention]
However, according to the technique disclosed in the above-mentioned publication, the presence or absence of tooth missing is determined by the ratio of the intermediate pulse period T1 and the average value of the preceding and following pulse periods T0 and T2, and therefore, the pulse signal is caused by disturbance or the like. However, even if there is a temporary change in the data, it is easy to mistakenly determine that the tooth is missing, and there is a problem in diagnostic accuracy.
[0009]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rotor tooth chipping detecting device of a wheel speed sensor that can accurately detect tooth chipping of a signal rotor.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a signal rotor which rotates integrally with a wheel, and detects a plurality of teeth formed at regular intervals on the signal rotor and provided on the outer periphery of the signal rotor to generate a pulse signal. A wheel speed sensor having a pulse signal generating means for generating a wheel speed sensor, and an arithmetic unit for detecting chipping of the signal rotor based on a pulse signal output from the pulse signal generating means, and a rotor tooth chipping detecting device for a wheel speed sensor. In the above, the arithmetic unit includes a pulse cycle calculating means for calculating a pulse cycle based on a pulse signal from the pulse signal generating means, and a one pulse time ratio is calculated from a ratio of the two pulse cycles calculated before and after the pulse cycle. A one-pulse time ratio calculating means, an abnormal area determining means for determining whether or not the one-pulse time ratio is in an abnormal area; A normal range determining means for determining whether or not the ratio is within a normal range; and a one-pulse time ratio normal time counter is cleared when the one-pulse time ratio is initially determined to be in an abnormal range. 1 pulse time ratio normal counter means for incrementing the 1 pulse time ratio normal counter every time the pulse signal is detected until it is determined that the 1 pulse time ratio is normal again; A tooth missing determining means for determining that there is tooth missing when the one-pulse time ratio when a value obtained by subtracting a subtraction constant of 3 from the number of teeth of the rotor is in an abnormal range is provided.
[0011]
In such a configuration, based on a pulse period calculated based on a pulse signal output each time a tooth formed on the signal rotor is detected from the pulse signal generation unit, the ratio of two successive pulse periods is set to 1 The pulse time ratio is calculated, and it is determined whether or not this one pulse time ratio is in an abnormal region. When the one pulse time ratio is first determined to be in an abnormal region, the one pulse time ratio normal counter is cleared. Thereafter, the 1-pulse time ratio normal counter is incremented each time a pulse signal is detected until the 1-pulse time ratio is in the abnormal range again, and the value of the 1-pulse time ratio normal counter is set to the value of the signal rotor. If a value obtained by subtracting 3 as a subtraction constant from the number of teeth has been reached and the one-pulse time ratio at that time is in an abnormal region, it is determined that there is tooth missing.
[0012]
In this case, preferably, 1) in the tooth missing determining means, the one-pulse time ratio is abnormal when the one-pulse time ratio normal counter reaches a value obtained by subtracting the subtraction constant from the number of teeth of the signal rotor. And when the state reaches a set value, it is determined that there is a missing tooth.
[0013]
2) The missing tooth determining means checks the missing tooth determining condition based on the driving state of the vehicle to determine whether the missing tooth can be normally detected. If the missing tooth determining condition is not satisfied, the missing tooth detecting process is performed. It is characterized by stopping.
[0014]
3) If the wheel speed detected based on the pulse signal from the wheel speed sensor provided on any of the other wheels is equal to or lower than the set low vehicle speed, the missing tooth determining means stops the missing tooth detection process. It is characterized by.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a power transmission system of a four-wheel drive vehicle. In the following, a process for detecting missing teeth will be described by taking a wheel speed sensor provided along with transfer control for controlling distribution of driving force to front and rear wheels as an example.
[0016]
Reference numeral 1 in FIG. 1 denotes an engine, and a transfer 3 is integrally connected to a rear portion of a transmission 2 connected to an output shaft of the engine 1. The transfer 3 has a planetary gear mechanism 4 to which the driving force from the transmission 2 is input, and a plurality of transfer mechanisms which are connected to the planetary gear mechanism 4 and whose fastening torque is electronically controlled by a transfer control unit (TCU) 20 as an arithmetic unit described later. A center differential is constituted by the transfer clutch 5 composed of a plate clutch. After the driving force of the engine 1 is shifted by the transmission 2 to a predetermined speed, the driving force is distributed to the front wheel side and the rear wheel side via the transfer 3.
[0017]
In this embodiment, the output side of the transmission 2 is connected to a ring gear of the planetary gear mechanism 4, and a carrier that rotatably supports a pinion that meshes with the ring gear and the sun gear is connected to a rear differential 7 via a propeller shaft 6. ing.
[0018]
The carrier of the planetary gear mechanism 4 is connected to the clutch drum of the transfer clutch 5, the sun gear is connected to the clutch hub of the transfer clutch 5, and is connected to the front differential 9 via the front drive shaft 8.
[0019]
The transfer clutch 5 includes a drive mechanism that presses, via a carrier, a clutch plate that continuously connects and disconnects the clutch drum and the clutch hub through a carrier, for example, an electromagnetic drive mechanism including an electromagnetic clutch and a torque amplifying cam. By controlling the exciting current of the electromagnetic drive mechanism, the fastening torque is controlled.
[0020]
Then, the driving force input from the transmission 2 to the planetary gear mechanism 4 is transmitted from the carrier to the rear left and right wheels 11L and 11R via the rear differential 7, and the difference between the carrier and the sun gear according to the engagement force of the transfer clutch 5. The dynamic output is transmitted via the front differential 9 to the front left and right wheels 10L, 10R. That is, when the transfer clutch 5 is completely engaged, the carrier and the sun gear are integrally fixed and torque is uniformly distributed to the front wheel side and the rear wheel side, and when the transfer clutch 5 is disengaged, the rear wheel biased torque distribution is performed. It becomes.
[0021]
The engagement torque of the transfer clutch 5 is electronically controlled by a transfer control unit (TCU) 20 composed mainly of a microcomputer. The transfer control unit 20 receives signals from various sensors and switches for detecting an engine operating state and a vehicle running state, control signals in other control units, and the like, and instructs a fastening torque based on these signals. Calculate the value.
[0022]
As shown in FIG. 1, the signals input to the TCU 20 include a throttle opening sensor 22 for detecting the opening of the throttle valve, a brake switch 23 which is turned on by depressing a brake pedal, and an ON signal when the handbrake lever is pulled. Signals from an operating handbrake switch 24, a lateral acceleration sensor 25 for detecting a lateral acceleration of the vehicle, and the like, an ABS operation signal from an ABS control unit (ABS_ECU) 30, and the like are input.
[0023]
Reference numeral 26 denotes a signal rotor which rotates integrally with the wheels 10R, 10L, 11R, 11L. Electromagnetic pickups 27R, 27L, 28R, 28L as an example of pulse signal generating means are provided on the outer periphery of each signal rotor 26. Each of the electromagnetic pickups 27R, 27L, 28R, and 28L and the signal rotor 26 constitute a wheel speed sensor, and a pulse signal from the electromagnetic pickups 27R, 27L, 28R, and 28L is provided. It is input to the TCU 20.
[0024]
As shown in FIG. 2, a plurality of teeth made of a magnetic material are formed at equal intervals on the outer periphery of each signal rotor 26. In each of the electromagnetic pickups 27R, 27L, 28R, and 28L, a magnetic field generated when the teeth pass. , And outputs a sinusoidal pulse signal to the TCU 20. The TCU 20 shapes the input pulse signal into a predetermined waveform, and calculates the wheel speed of each wheel 10R, 10L, 11R, 11L based on the cycle of the pulse signal.
[0025]
The TCU 20 controls the engagement force of the transfer clutch 5 based on each input signal. When the fastening force of the transfer clutch 5 is increased, a differential lock state is established. When the fastening force of the transfer clutch 5 is released, the driving force is distributed to the front and rear wheels in accordance with the distribution ratio set by the planetary gear mechanism 4.
[0026]
In addition, the TCU 20 detects the presence or absence of tooth missing in each signal rotor 26 based on the pulse signals output from each of the electromagnetic pickups 27R, 27L, 28R, and 28L.
[0027]
The detection processing of the missing tooth is performed according to a missing tooth detection routine shown in FIG. In the following, for convenience, the number of teeth formed on the outer periphery of the signal rotor 26 is assumed to be 6, and the target for detecting missing teeth is represented by the signal rotor 26 that rotates integrally with the front right (FR) wheel 10R. A description will be given of a case where the missing tooth is detected based on a pulse signal from an electromagnetic pickup 27R provided in addition to the signal rotor 26. The detection of the missing tooth is performed by using pulses from the other electromagnetic pickups 27L, 28R and 28L. The same operation is performed based on a signal.
[0028]
This routine is started by interruption using a pulse signal input from the electromagnetic pickup 27R as a trigger signal. First, in step S1, is it detected whether the tooth loss of the signal rotor 26 that rotates integrally with the other wheels 10L, 11R, and 11L is detected. It is determined whether or not a missing tooth has been detected. If a missing tooth has been detected, the process branches to step S2 to terminate the missing tooth detection processing and exit the routine. In this case, when the calculation load of the TCU 20 is light, even if the signal rotor 26 that rotates integrally with the other wheels 10L, 11R, and 11L detects missing teeth, the signal rotor 26 that rotates integrally with the front right wheel 10R. May be continued.
[0029]
If no missing tooth is detected in the signal rotor 26 that rotates integrally with the other wheels 10L, 11R, 11L, the process proceeds to step S3, and one pulse period t is calculated. In this embodiment, as shown in FIG. 4, one pulse period t is calculated from the difference between the fall time of the current pulse signal and the fall time of the previous pulse signal. Further, a one-pulse time ratio FRPLS is calculated based on two one-pulse periods t (-1), t which are immediately before and after the one-pulse period t (-1) calculated last time and the one-pulse period t calculated this time (FRPLS). = T (-1) / t).
[0030]
As shown in FIG. 4A, when the signal rotor 26 has no tooth missing, the one pulse periods t are almost equal, and therefore the one pulse time ratio FRPLS is:
FPLLS = t (−1) /t≒1.0
It becomes. On the other hand, as shown in FIG. 4B, when tooth missing occurs, the one-pulse time ratio FRPLS becomes
FRPLS = t2 / t3 ≒ 0.5
It becomes.
[0031]
Next, the process proceeds to step S4, in which a missing tooth determination condition is detected. In a succeeding step S5, it is checked whether the missing tooth determination condition is satisfied. As described above, in the present embodiment, when the one-pulse time ratio FRPLS is FRPLS ≒ 0.5, it is determined that tooth missing occurs. In some cases, the ratio of two one-pulse periods t (-1), t before and after the one-pulse period t (-1) and the current one-pulse period t (one-pulse time ratio FRPLS) reaches about 0.5. For this reason, the driving region in which such an erroneous determination is liable to be made is excluded, and the detection accuracy of missing teeth is improved.
[0032]
The condition for determining missing teeth in the present embodiment is set as follows.
1) You are not accelerating
2) Not decelerating or stopping
3) No slip at start
4) ABS and other traction control systems are inactive
5) No turning
6) Sensors and switches that detect these are operating normally.
[0033]
1) Whether or not the vehicle is accelerating is determined based on the throttle opening detected by the throttle opening sensor 22. If the throttle opening is equal to or less than the set opening, it is determined that the vehicle is not accelerating.
[0034]
2) Whether or not the vehicle is decelerating is determined based on the state of the brake switch 23. When the brake switch 23 is in the OFF brake release state, it is determined that the vehicle is not decelerating. Whether or not the vehicle is stopped is determined based on the state of the handbrake switch 24. If the handbrake switch 24 is in the OFF state of the handbrake, it is determined that the vehicle is not stopped.
[0035]
3) It is determined whether or not the slip at the start has occurred based on the wheel speed calculated based on the pulse signals from the electromagnetic pickups 27L, 28R, 28L provided on the other wheels 10L, 11R, 11L. When each wheel speed is equal to or higher than the set vehicle speed (for example, 10 [Km / h]), it is determined that the slip at the time of starting has not occurred.
[0036]
4) Whether or not the ABS and other traction control systems are inactive is determined based on the operation signals of each control system.
[0037]
5) It is determined that the vehicle is turning when the inner wheel is likely to slip based on the lateral acceleration detected by the lateral acceleration sensor 25 or the yaw rate detected by the yaw rate sensor (not shown), for example. .
[0038]
6) Whether or not the operation of the sensors and switches is normal is determined based on a signal from another failure diagnosis control unit.
[0039]
Then, the process proceeds to step S5, where it is checked whether or not all of these tooth missing determination conditions are satisfied. If not, it is determined that the tooth missing determination condition is not satisfied, and the process branches to step S6 to determine whether the front right wheel 10R has been satisfied. The toothless counter FRGCNT of the integrally rotating signal rotor 26 is cleared (FRGCNT ← 0), and the process jumps to step S9.
[0040]
On the other hand, when all of the missing tooth determination conditions are satisfied, it is determined that the missing tooth condition is satisfied, and when the process proceeds to step S7, the following abnormal region determination condition, that is, the vehicle has passed the part where the missing tooth has occurred. It is checked whether the immediately succeeding pulse signal is detected and whether the one-pulse time ratio FRPLS calculated based on the pulse signal and the previous pulse signal is around 0.5 set as an abnormal value. FRCNT is a 1-pulse time ratio normal counter which starts counting when the 1-pulse time ratio FRPLS switches from the abnormal region to the normal region, and is incremented in step S12 described later and cleared in step S13.
[0041]
Abnormal area judgment condition
1) FRCNT = N (number of teeth) -3
2) About 0.4 ≦ FRPLS ≦ about 0.6
[0042]
Then, if all of these conditions are satisfied, the flow branches to step S8, and if not, the flow proceeds to step S9.
[0043]
In step S8, the toothless counter FRGCNT is incremented, and the process proceeds to step S9 (FRGCNT ← FRGCNT + 1).
[0044]
In step S9, the value of the missing tooth counter FRGCNT is compared with the set value GCNTTo. If FRGCNT ≧ GCNTTo, the process proceeds to step S10, where it is determined that the signal rotor 26 has missing teeth, and the routine ends.
[0045]
In the present embodiment, the set value GCNTo is set to a value corresponding to approximately constant vehicle speed (for example, 50 [Km / h]) and running for 30 [sec].
[0046]
As described above, in the present embodiment, when it is determined that the tooth missing condition is satisfied in step S7, it is not immediately determined that the signal rotor 26 has the tooth missing, and the satisfaction of the tooth missing condition is satisfied during the set value GCNTTo. Only when there is, it is determined that there is a missing tooth, so that a higher accuracy of detecting missing teeth can be obtained.
[0047]
On the other hand, when FRGCNT <GCNTo, the process proceeds to step S11, in which the normal region determination condition described below, that is, the tooth missing determination condition executed in step S5 and the one pulse time ratio FRPLS set as a normal value, are set to 1 Check if it is nearby.
[0048]
Normal range judgment condition
1) Tooth missing condition is satisfied
2) About 0.9 ≦ FRPLS ≦ about 1.1
[0049]
Then, if all of these conditions are satisfied, the flow branches to step S12, and if not, the flow proceeds to step S13.
[0050]
In step S12, the 1-pulse time ratio normal counter FRCNT is incremented (FRCNT ← FRCNT + 1), and the routine exits. On the other hand, when the process proceeds to step S13, the 1-pulse time ratio normal time counter FRCNT is cleared (FRCNT ← 0), and the routine exits.
[0051]
Next, an example will be described in which a missing tooth of the signal rotor 26 that rotates integrally with the front right wheel 10R is detected based on a pulse signal detected by the electromagnetic pickup 27R shown in FIG. 4 in accordance with the above-described missing tooth detecting routine. I do. In the following, it is assumed that the condition for determining missing teeth performed in steps S4 and S11 is satisfied.
[0052]
As shown in FIG. 11A, in the state where the tooth missing does not occur in the signal rotor 26, the one pulse cycle t calculated in step S3 becomes substantially the same value for each calculation cycle, and therefore, the one pulse time ratio is calculated. FRPLS becomes FLPLS ≒ 1, and in step S7, the determination condition 2) is not satisfied, and the process proceeds to step S11. In step S11, since the determination condition 2) is satisfied, the process proceeds to step S12, where the 1-pulse time ratio normal counter FRCNT is incremented (FRCNT ← FRCNT + 1).
[0053]
The 1-pulse time ratio normal counter FRCNT is incremented until it is cleared in step S13, that is, until the determination condition 2) in step S11 is no longer satisfied.
[0054]
On the other hand, as shown in FIG. 4 (b), when the tooth loss occurs in the signal rotor 26, the one pulse period t1, t2 shows almost the same value in the immediately preceding routine. After incrementing the normal ratio counter FRCNT, the routine exits.
[0055]
On the other hand, when the one-pulse period t3 is calculated in step S3, the one-pulse time ratio FRPLS becomes
FRPLS = t2 / t3 ≒ 0.5
It becomes.
[0056]
Accordingly, in step S7, the determination condition 2) is satisfied, but since the determination condition 1) is not satisfied, the process proceeds to step S11. Then, in step S11, the determination condition 2) is not satisfied. Therefore, the process proceeds to step S13, where the 1-pulse time ratio normal time counter FRCNT is cleared, and the routine exits.
[0057]
In step S3 of the second cycle, one pulse period t4 is calculated, and one pulse time ratio FRPLS is calculated as follows.
FRPLS = t3 / t4 ≒ 2
It becomes.
[0058]
Therefore, in step S7, since both of the determination conditions 1) and 2) are not satisfied, the process directly proceeds to step S11, and since the determination condition 2) of step S11 is not satisfied, the pulse is determined in step S13. The state where the normal time ratio counter FRCNT is cleared is maintained, and the routine exits.
[0059]
Thereafter, in step S3 of the third cycle, one pulse period t5 is calculated, and one pulse time ratio FRPLS is calculated as follows.
FRPLS = t4 / t5 ≒ 1
It becomes.
[0060]
Therefore, when the process proceeds to step S11, the condition 2) of the determination condition is satisfied, so that the process branches to step S12, where the one-pulse time ratio normal time counter FRCNT is incremented, and FRCNT = 1.
[0061]
In the fourth and fifth routines, one pulse periods t6 and t7 are calculated in step S3, and each one pulse time ratio FRPLS is calculated as follows.
FRPLS = t5 / t6 ≒ 1
FRPLS = t6 / t7 ≒ 1
In step S12, the one-pulse time ratio normal time counter FRCNT is incremented, so that in the fifth cycle, FRCNT = 3.
[0062]
In the subsequent sixth routine, a pulse signal after passing through the portion of the signal rotor 26 where the tooth is missing is detected, and in step S3,
FRPLS = t7 / t8 ≒ 0.5
It becomes.
[0063]
Thereafter, the 1-pulse time ratio normal counter FRCNT referred to in step S7 is FRCNT = 3 set at the time of the previous execution of the routine.
1) FRCNT = N-3
2) About 0.4 ≦ FRPLS ≦ about 0.6
Are satisfied, the flow branches to step S8, and the missing tooth counter FRGCNT is incremented. The determination condition 1) is for specifying a pulse signal detected immediately after passing through the toothless portion, and by satisfying the determination condition, it is determined that the pulse signal is of the same portion.
[0064]
As described above, in the present embodiment, in the first time that the determination condition 2) is satisfied, the 1-pulse time ratio FRPLS immediately after adding the next same part without immediately determining that there is tooth missing is detected, When the one-pulse time ratio FRPLS again shows a value close to 0.5, the tooth missing counter FRGCNT is incremented, so that a detection error due to the influence of noise or the like can be eliminated.
[0065]
As described above, in the present embodiment, the 1-pulse time ratio normal counter FRCNT is incremented for the first time in the third cycle, so the subtraction constant is set to 3. In this case, it is possible to increment the normal counter FRCNT for one pulse time ratio for the first time after the fourth round. In this case, the subtraction constant is set to a value (4, 5,...) Corresponding thereto.
[0066]
Since the missing tooth counter FRGCNT is not cleared while the missing tooth determination condition is satisfied, it is incremented every time the determination condition executed in step S7 is satisfied at the next and subsequent routine executions, and eventually the FRGCNT is completed. When ≧ GCNTo is reached, after continuing by the set value GCNTo, the process proceeds to step S10, where it is determined that the signal rotor 26 has missing teeth, and the routine is terminated.
[0067]
If it is determined in the tooth missing detection routine that there is tooth missing, the wheel speed of each wheel 10R, 10L, 11R, 11L is set to 0 {Km / h}. The transfer clutch 5 provided is disengaged to prevent excessive torque transmission to the front wheels or the rear wheels.
[0068]
As described above, in the present embodiment, the presence / absence of tooth missing of the signal rotor 26 that rotates integrally with the front and rear left and right wheels 10L, 10R, 11L, 11R is determined by comparing the previous one pulse cycle t (-1) with the current one pulse. The one-pulse time ratio FRPLS (= t (−1) / t) calculated based on two one-pulse periods t (−1), t before and after the period t is in an abnormal region (about 0.4 ≦ FRPLS). ≦ approximately 0.6), and the one-pulse time ratio FRPLS calculated based on the pulse signal detected immediately after passing through the same toothless portion is also in the abnormal region (approximately 0.4 ≦ FRPLS ≦ approximately 0). .6), it is not immediately determined that the signal rotor 26 has a missing tooth, and it is determined that there is a missing tooth after the state continues for the set value GCNTo. It is possible to obtain detection accuracy Kill.
[0069]
In this case, after the 1-pulse time ratio FRPLS is initially determined to be in the abnormal region, and when the 1-pulse time ratio FRPLS of the same portion is again determined to be in the abnormal region, it is immediately determined that there is tooth missing. Needless to say, it may be.
[0070]
【The invention's effect】
As described above, according to the embodiments of the present invention, excellent effects such as detection of missing teeth of the signal rotor with high accuracy can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a power transmission system of a four-wheel drive vehicle.
FIG. 2 is a schematic configuration diagram of a wheel speed sensor.
FIG. 3 is a flowchart showing a missing tooth detection routine.
FIG. 4A is a waveform diagram of a pulse signal output from the electromagnetic pickup in a normal state, and FIG. 4B is a waveform diagram of a pulse signal output from the electromagnetic pickup when tooth missing has occurred.
5A and 5B show a conventional example, and FIG. 5A is a waveform diagram of a pulse signal output from an electromagnetic pickup in a normal state, and FIG. 5B is a waveform diagram of a pulse signal output from the electromagnetic pickup when tooth missing occurs.
[Explanation of symbols]
10R, 10L, 11R, 11L wheels
20 Transfer control unit (arithmetic unit)
26 signal rotor
27R, 27L, 28R, 28L Electromagnetic pickup (pulse signal generating means)
FRCNT 1 pulse time ratio normal time counter
FRGCNT tooth missing counter
FRPLS 1 pulse time ratio
GCNTo set value
t pulse period

Claims (4)

A wheel having a signal rotor that rotates integrally with a wheel, and a pulse signal generating means for generating a pulse signal by detecting a plurality of teeth formed at regular intervals on the signal rotor and provided on an outer periphery of the signal rotor. A speed sensor,
An arithmetic unit that detects missing teeth of the signal rotor based on a pulse signal output from the pulse signal generating unit;
In the rotor tooth chipping detection device of the wheel speed sensor comprising:
In the above operation unit,
A pulse period calculating unit that calculates a pulse period based on a pulse signal from the pulse signal generating unit;
One-pulse time ratio calculating means for calculating a one-pulse time ratio from a ratio of the two pulse periods calculated before and after;
Abnormal region determining means for determining whether or not the one pulse time ratio is in an abnormal region;
Normal range determining means for determining whether or not the one pulse time ratio is in a normal range;
When the one-pulse time ratio is initially determined to be in the abnormal region, the one-pulse time ratio normal counter is cleared, and until the one-pulse time ratio is again determined to be in the abnormal region, the one-pulse time ratio normal counter is cleared. 1 pulse time ratio normal time counter means for incrementing each time the pulse signal is detected,
When the value of the 1-pulse time ratio normal counter reaches a value obtained by subtracting 3 as a subtraction constant from the number of teeth of the signal rotor, the 1-pulse time ratio is in an abnormal range. Chipping determination means;
A device for detecting a missing tooth of a rotor of a wheel speed sensor, comprising: In the tooth missing determination means, the one-pulse time ratio indicates an abnormal value when the one-pulse time ratio normal counter reaches a value obtained by subtracting the subtraction constant from the number of teeth of the signal rotor. 2. The apparatus according to claim 1, wherein when the predetermined value reaches a set value, it is determined that there is a missing tooth. The missing tooth determining means checks the missing tooth determining condition as to whether the missing tooth can be normally detected based on the driving state of the vehicle, and stops the missing tooth detecting process if the missing tooth determination condition is not satisfied. 3. The device for detecting missing teeth of a rotor of a wheel speed sensor according to claim 1, wherein: The missing tooth determining means stops the missing tooth detection process when the wheel speed detected based on the pulse signal from the wheel speed sensor provided on any of the other wheels is equal to or less than a set low vehicle speed. The device for detecting missing teeth of a rotor of a wheel speed sensor according to any one of claims 1 to 3.

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