JPH0541411Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for detecting an abnormality in a rotation sensor from a change in the duty cycle of output pulses of the rotation sensor.

[Conventional technology]

For example, a rotation sensor having a structure as illustrated in FIG. 6 is used in a speedometer of an automobile or the like to measure the vehicle speed. This rotation sensor 1 is
A predetermined number of NS magnetic poles are magnetized around the circumference of a rotor 102 made of a disk-shaped magnetic material, and a voltage is induced in a coil 103 by connecting this rotor 102 to, for example, an engine transmission and rotating it. death,
This induced voltage is shaped into a square wave by a waveform shaping circuit 104 and outputted as an output pulse P having a repetition frequency proportional to the rotational speed.

As is clear from the above, this type of rotation sensor generates pulses based on the magnetism of the magnetic poles magnetized to the rotor.
If damage or the like occurs on the circumferential surface of the rotor 102, as indicated by the symbol S in the figure, an abnormality will occur in the output pulse of the rotation sensor, making accurate speed detection impossible.

To prevent this, conventionally, the occurrence of an abnormality in the rotation sensor has been detected using a method as shown in FIG. 7 or 8.

In other words, the method shown in FIG.
T ₁ /T is measured, and when the duty cycle deviates from the allowable range (for example, 40 to 60%), it is detected as an _abnormality in the rotation sensor. The duty cycle T ₁ /T of the output pulse P of the rotation sensor is measured, and when the duty cycle exceeds a permissible range, it is detected as an abnormality in the rotation sensor.

[The problem that the idea attempts to solve]

However, when the method of FIG. 7 is used, the duty cycle must be measured for each output pulse of the rotation sensor, which makes the measurement process complicated and unsuitable for the case where the signal is centrally processed together with various other sensor signals by a microcomputer, as in recent electronic automobiles. Also, when the method of FIG. 8 is used, the output pulse, the period of which varies according to the rotation speed, is measured for a predetermined fixed time _T0 , which causes the problem that it is difficult to quickly detect an abnormal pulse when an abnormality occurs in a specific output pulse.

The present invention was devised in view of the above circumstances, and while measuring the duty cycle of the output pulse of the rotation sensor at regular pulse intervals, the duty cycle of all individual output pulses of the rotation sensor is measured at a constant pulse interval. An object of the present invention is to provide an abnormality detection device for a rotation sensor that can always perform measurement at each repetition period.

[Means to solve the problem]

As the principle of the present invention is shown in FIG. 1, when the number of output pulses P generated per rotation of the rotation sensor 1 is N,
Or measurement start command means 2 that issues a duty cycle measurement start command at every (N+1) pulse interval.
Each time a measurement start command is received from the measurement start command means 2, the output pulse P of the rotation sensor 1 at that time is
The duty cycle T ₁ /T is calculated from the duty time measuring means 3 that measures the period T and the time T 1 during which the output is "1", and the period T and time T ₁ output by the duty time measuring means ₃ . The duty cycle calculation means 4 calculates the rotation sensor 1 by comparing the duty cycle T ₁ /T calculated by the duty cycle calculation means 4 with a reference duty cycle 6 prepared in advance. The apparatus is characterized in that it includes an abnormality determining means 5 for determining an abnormality.

[Effect]

When the rotation sensor 1 outputs an output pulse P having a repetition frequency proportional to the rotation speed, the measurement start command means 2 counts this pulse P and sets it to a predetermined number (N) as shown in FIG. 2a and b. -1)
Alternatively, a measurement start command signal is sent to the duty time measuring means 3 at every (N+1) pulse interval.

When the measurement start command signal is given from the measurement start command means 2, the duty time measuring means 3 measures the pulse period T of the output pulse P of the rotation sensor 1 at that time and the time T1 during which the output is " ₁ ". , and sent to the duty cycle calculating means 4.

The duty cycle calculating means 4 uses the output pulse P sent from the duty time measuring means 3.
The duty cycle T ₁ /T at that time is calculated based on the period T and the time T ₁ during which the output is "1", and is sent to the abnormality determining means 5.

Then, the abnormality determination means 5 determines the duty cycle sent from the duty time measuring means 2.
Compare T ₁ /T with 6, which is a reference duty cycle for abnormality determination prepared in advance, and if the calculated value is within the allowable range of the reference duty cycle 6, it is determined that the rotation sensor 1 is normal. If the reference duty cycle 6 is outside the allowable range, it is determined that an abnormality has occurred in the rotation sensor 1, and the detection result is output.

Therefore, according to the present invention, the duty cycle of the output pulse P of the rotation sensor 1 can be confirmed by (N-1) or (N-1) of the output pulse P of the rotation sensor 1.
+1) It is performed intermittently at every pulse interval, and N
The duty cycles of all individual pulses of the output pulse P are measured with a repetition period of *(N-1) pulses or N*(N+1) pulse intervals.

〔Example〕

FIG. 3 shows an embodiment of the device of the present invention, which is constructed using a microcomputer. Reference numeral 1 denotes a rotation sensor for detecting speed, which has a structure similar to that shown in FIG. 6. Reference numeral 21 denotes a fuel sensor for detecting the amount of remaining fuel, for example.
Reference numeral 22 denotes a microcomputer, 23 denotes a display device such as an electronic meter that displays various information such as vehicle speed and remaining fuel, and 24 denotes an abnormality alarm that notifies the driver of the occurrence of an abnormality.
The ROM stores a program for detecting abnormalities in the rotation sensor according to the present invention, as shown in the flow chart of FIG.
It stores main routine programs for performing various signal processing such as vehicle speed detection, fuel detection, etc.

Hereinafter, the operation of the above embodiment will be explained with reference to the waveform diagram of FIG. 4 and the flowchart of FIG. 5.
Note that the rotation sensor 1 for detecting the vehicle speed has a rotation rate of N per rotation as shown in FIG.
An example will be described in which a sensor that generates =4 pulses _PA , P _B , P _C , and _PD is used. Also, the duty cycle is measured by (N-) of the output pulse P.
1) It is assumed that it is performed every three pulse intervals.

Normally, the microcomputer 22 is in the state of executing a main routine program, and measures the vehicle speed from the output pulses of various sensors, for example, the rotation sensor 1 shown, or measures the vehicle speed from the output pulses of the fuel sensor 21 according to the main routine program stored in the ROM. The remaining amount of fuel is calculated from the output signal, and the information is displayed on a display device 23 on the instrument panel in the driver's seat.

When the microcomputer 22 detects the pulse edge of the output pulse P of the rotation sensor 1, the microcomputer 22 interrupts the main routine program and shifts its operation to the process of the present invention shown in the flowchart of FIG. (Step S ₁ ).

First of all, microcomputer 2
2, it is determined whether the detected pulse edge is a rising edge or a falling edge of the output pulse P of the rotation sensor 1 (step S ₂ ), and if the detected pulse edge is a rising edge, the process proceeds to step S ₃ ; In the case of a falling edge, the process moves to step _S4 .

Now _, assuming that the detected pulse edge is the rising edge of pulse P _A in _FIG . From the measurement, it is determined whether it corresponds to the (N-1)=3rd pulse. Here, assuming that the above pulse P _A corresponds to the third pulse from the previous duty cycle measurement,
The process moves to step _S5 , where the microcomputer 22 clears the internally prepared time counter, sets the measuring flag to "1" indicating that duty cycle measurement has started, and at the same time , the time counting operation of the counter is started (steps S ₆ and S ₇ ).

As a result, the period T of the pulse P _A and the time T _A1 during which the output is "1" at that time are determined based on the position of the rising edge of the pulse P _A in Fig. 4.
The timing operation starts. After completing step _S7 , the microcomputer 22 returns to the main routine program and executes the main routine processing until the next pulse edge of the output pulse P is detected.

Next, when the microcomputer 22 detects the next pulse edge of the output pulse P, that is, the falling edge of the pulse P _A in FIG. 4, the microcomputer 22 interrupts the main routine program, and the process returns to FIG. 5. (Step _S1 ).

Then, when it is determined in step _S2 that the pulse edge of the detected pulse P _A is a falling edge, the process moves to step _S4 , and it is determined whether the measurement flag is set to "1" or not. It is determined whether In this case, since the measuring flag was set to "1" in step _S6 mentioned above, the process moves to step _S8 , and the count time of the counter at that time, that is, the output of pulse P _A in FIG. 1'_' is read into the _T1 register in the microcomputer 22 and stored.

After the above processing is completed, the processing returns to the main routine program again.

When the microcomputer 22 detects the next pulse edge, that is, the rising edge of the pulse P _B in FIG.
2 interrupts the main routine program, and the process returns to FIG. 5 (step S ₁ ).

When it is determined in step _S2 that the pulse edge of the detected pulse P _B is a rising edge, the process moves to step _S3 , and the pulse P _B is determined to be a rising edge from the previous duty cycle measurement. It is determined whether (N-1) corresponds to the third pulse. Here, the above pulse
Since P _B is a pulse corresponding to the fourth pulse from the previous duty cycle measurement, the process moves to step _S9 .

Next, in step _S9 , it is determined whether the measurement flag is set to "1".
In this case, since the measuring flag remains set to "1" indicating that the duty cycle is being measured in step _S6 described above, the process continues at step S6.
Transition to S ₁₀ , the count time of the counter at that time,
That is, the period T of the pulse P _A in FIG. 4 is read into the T register in the microcomputer 22 and stored.

The microcomputer 22 operates as described above.
The time T _A1 during which the output of pulse P _A is “1” is stored in the T1 register, and the pulse P _A1 is stored in the T register.
When the period T of P _A is stored, these two stored values
Based on T _A1 and T, the duty cycle T _A1 /T of the pulse P _A at that time is calculated (step S ₁₁ ).
When the calculation of the duty cycle T _A1 /T is completed, the measurement flag is reset to "0" (step S ₁₂ ), and the measurement of the duty cycle of the pulse P _A is ended.

The duty cycle T _A1 /T of the pulse P _A calculated as above is calculated by the computer 22.
It is compared with a reference duty cycle stored in advance in the ROM, and if the duty cycle T _A1 /T is within the allowable range of the reference duty cycle, the rotation sensor 1 is normal, and if it is outside the allowable range. In this case, it is determined that an abnormality has occurred in the rotation sensor 1, and in the case of an abnormality, the determination result is displayed in a predetermined manner on an alarm device 24 installed on an instrument panel of the driver's seat.

The microcomputer 22 repeatedly executes the above processing. Therefore, the pulse edge of the pulse P _D corresponding to the next third pulse in FIG. 4 and the pulse edge of the subsequent pulse P _A operate in the same manner as above, and the duty cycle T _D1 /
Measure T. In this case, since the pulse width of the pulse P _D is small, its duty cycle T _D1 /T exceeds the allowable range, and the microcomputer 22 determines that an abnormality has occurred in the rotation sensor 1 and sends an alarm to the alarm 24. Output.

As is clear from the above operation description, in the case of the above embodiment, the duty cycle is checked repeatedly in the order of P _A , P _D , P _C , and P _B every three pulses, and the output of the rotation sensor 1 is N×(N-1) of pulse P
= All pulses P _A , P _D , P _C , P _B every 12 pulses
The duty cycle is measured.

In addition, although the above embodiment has been explained using an example in which the duty cycle is measured every (N-1)=3 pulse intervals, instead of this, the duty cycle is measured every (N+1)=5 pulse intervals. The same procedure can be performed by measuring cycles. In this case, the determination formula (N-1)=3 in step _S3 in FIG. 5 may be replaced with (N+1)=5. As a result, the duty cycle is checked every 5 pulses, and every N×(N+1)=20 pulses of the output pulse P of the rotation sensor 1, all pulses P _A , P _D , P _C , P _B The duty cycle is measured.

[Effect of idea]

Since the present invention has the structure and operation described above, while measuring the duty cycle of the output pulse of the rotation sensor at regular pulse intervals, the duty cycle of all the individual output pulses of the rotation sensor is measured. can be measured at regular repetition intervals, making it suitable for centralized processing by microcomputers used in modern electronic automobiles, etc., as well as detecting abnormalities in specific output pulses within one rotation of the rotation sensor. This provides an excellent effect in that even when a problem occurs, an abnormality in the specific pulse can be quickly detected.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a waveform diagram for explaining the invention, Fig. 3 is a block circuit diagram of an embodiment of the invention, and Fig. 4 is for explaining the operation of the above embodiment. FIG. 5 is a flowchart of the operation of the above embodiment, FIG. 6 is a structural principle diagram of an example of a rotation sensor, and FIGS. 7 and 8 are explanatory diagrams of the conventional duty cycle measurement principle. It is. 1... Rotation sensor, 2... Measurement start command means,
3... Duty time measuring means, 4... Duty cycle calculating means, 5... Abnormality determining means, 6...
...Reference duty cycle, P...Output pulse of rotation sensor, T...Period of output pulse P, T ₁ ...
...Time of output “1” of output pulse P.

Claims (1)

[Claims for Utility Model Registration] When the number of output pulses generated per rotation of the rotation sensor is N, the duty cycle is measured every (N-1) or (N+1) pulse interval of the output pulses. Measurement start command means for issuing a start command, and each time a measurement start command is received from the measurement start command means, the period T of the output pulse of the rotation sensor at that time is determined.
and a duty time measuring means for measuring the time T1 during which the output is " ₁ "; and a duty time measuring means for calculating the duty cycle _{T1 /} T from the period T and time T1 output by the duty time measuring means. and an abnormality determining means for determining an abnormality in the rotation sensor by comparing the duty cycle calculated by the duty cycle calculating means with a reference duty cycle prepared in advance. Characteristic rotation sensor abnormality detection device.