JPH06174576A - Torque detector - Google Patents

Abstract

PURPOSE:To maintain a torque detecting function continuously without detecting an erroneous torque value even when trouble is generated in a torque sensor regarding the torque detector of a driving shaft. CONSTITUTION:A torque detector has a plurality of torque sensors 1, an analog- signal processing circuit 4 adding each output from each torque sensor and arithmetically operating the torque value of a driving shaft, a discriminating circuit J comparing signals from each torque sensor with a reference signal and sensing the presence of the generation of the trouble of each torque sensor while specifying fault torque sensors, a relay 15 interrupting the connection of the fault torque sensors and the analog-signal processing circuit when trouble is generated in response to a signal from the discriminating circuit, and a gain control circuit 16 changing the amplification factor of a torque-value corresponding analog signal in response to the number of the fault torque sensors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque detecting device provided with a torque sensor for detecting a torque applied to a drive shaft as magnetostriction in a non-contact manner.

[0002]

2. Description of the Related Art Generally, a shaft torque is the most basic characteristic for controlling a rotary drive system, and in order to accurately detect it, a so-called magnetostrictive torque sensor that detects drive torque as magnetostriction is known. A torque detection device including the above is already known (for example, JP-A-60-140133).

This magnetostrictive torque sensor has, for example, as schematically shown in FIG. 6, an exciting coil 1a and a detecting coil 1b arranged in a non-contact manner around a drive shaft D to be detected.
The high frequency power supply P is supplied to the exciting coil 1a to generate a magnetic field on the surface of the drive shaft D. Then, the change in the magnetic flux density due to the axial torque is measured as the change in the voltage generated on the detection coil 1b side, and the torque T applied to the drive shaft D is detected from this value.

[0004]

By the way, in the torque detecting device provided with the torque sensor as described above,
In order to reduce the generated voltage variations due to eccentricity during rotation of the drive shaft as much as possible and improve the reliability of the measured torque value, multiple torque sensors are usually arranged around the drive shaft. Therefore, an accurate torque value is calculated from the added value (or average) of the output voltage from each torque sensor.

However, in the detection device having such a plurality of torque sensors, if a failure such as disconnection occurs in a specific torque sensor, in the conventional addition processing system, an error from the failed torque sensor is detected. There is a problem that the normal torque value detection function cannot be maintained because the output voltage value is directly incorporated in the torque calculation, or the system stops the torque value detection process at all.

In view of the above problems, the present invention provides a torque detecting device that can maintain the torque detecting function as a device without calculating an incorrect torque value even if a failure occurs in the torque sensor. It is provided.

[0007]

In order to solve the above problems, a torque detection device according to the present invention is provided with a plurality (three in the figure) around a drive shaft as shown in FIG. 1, and a predetermined voltage is applied. A torque sensor that outputs an output voltage corresponding to the torque of the predetermined shaft, a torque value calculation unit that adds the outputs from the torque sensor to calculate the torque value of the drive shaft, and the torque sensor. From the failure sensor determination unit that detects the presence or absence of a failure in each torque sensor and identifies the failure torque sensor, and a failure occurs in accordance with the signal from the failure sensor determination unit. At this time, the sensor output cutoff means for cutting off the connection between the faulty torque sensor and the torque value calculation means, and the torque value for correcting the torque value in the torque value calculation means according to the number of the faulty torque sensors It includes a positive means.

[0008]

The signal from each torque sensor is constantly compared with the reference signal to detect the occurrence of a failure, and when the failure occurs, the signal output from the corresponding torque sensor to the torque value calculation means is stopped, and the normal torque sensor is detected. The torque value is detected from the output voltage from. In this case, the amount of torque information is reduced, but the reliability is higher than the torque value obtained by incorporating erroneous data into the calculation, and the torque detection function of the device itself is maintained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of a torque detection device having a magnetostriction detection type torque sensor. In the drawing, each torque sensor indicated by reference numeral 1 has an exciting coil 1a (driving section) for generating a predetermined magnetic field on the surface of a drive shaft (not shown) and a magnetic change amount corresponding to the axial torque of the drive shaft. It is composed of a detection coil 1b (detection unit) that produces a voltage corresponding to this.

According to this embodiment, the torque detecting device is provided with a total of three torque sensors 1 for one drive shaft, and the exciting coil 1a of each torque sensor 1 is orthogonal to the corresponding detecting coil 1b. The respective torque sensors 1 are arranged at equal intervals of 120 degrees in the circumferential direction of the drive shaft.
Since a predetermined magnetic field is generated on the surface of the drive shaft, the exciting coil 1a of each torque sensor 1 has a high frequency power source P as shown in the drawing.
Are connected in parallel with each other, and a predetermined exciting current flows through each exciting coil 1a.

On the other hand, the output voltage generated in each detection coil 1b is amplified by the amplifier 2 provided corresponding to each, and then input to the adder 3 which collects these voltages, and finally the analog voltage. The signal processing circuit 4 outputs the average voltage (DC) proportional to the shaft torque as a torque signal to the outside. The constituent elements described above are the same as those of the conventional torque detection device, and their operations are exactly the same.

Hereinafter, a method of discriminating a faulty torque sensor according to the present embodiment and a fault occurrence process will be described. First, regarding the failure detection of the exciting coil 1a as the sensor driving unit, the resistor 5 is inserted in series between each exciting coil 1a and the high frequency power source P, and the voltage across these resistors is measured. Since the voltage across the resistors 5 is an AC signal, both ends of each resistor 5 are connected to the detection circuit 6 provided one by one corresponding to each resistor 5, where the DC voltage Vr
Is converted to.

Next, the DC voltage Vr thus obtained from each detection circuit 6 is input to a comparator (window comparator) 7. Each comparator 7 has a reference value other than this. A reference voltage V preset from the generator 8 assuming a state where no failure has occurred in the exciting coil 1a.
base (maximum voltage Vbasemax value, minimum voltage Vbasemin value)
Is input, and the voltage Vr and the reference voltage Vbase are compared here.

In this way, the reference voltage Vbase and the voltage Vr
If the voltage Vr greatly deviates from the reference voltage V by comparison with the above, it means that a failure has occurred in the corresponding exciting coil 1a. Therefore, this information is transmitted via the logical sum circuit (OR type circuit) 9. Are stored in the memory circuit 10.
Here, the memory circuit 10 is a circuit that is configured by, for example, a flip-flop circuit and holds the input state from the OR circuit 9, and in the comparator 7 described above, the DC voltage Vr across the resistor 5 is assumed. Is determined to be out of the reference voltage Vbase, for example, it is held with the failure occurrence flag set to 1 in the memory circuit 10.

The voltage state across the resistor 5 at the time of failure will be described. If the exciting coil 1a of the specific torque sensor 1 is short-circuited, the voltage V across the resistor 5 (after DC voltage conversion). Is the maximum reference voltage Vbasema
If x is exceeded, and if the exciting coil 1a is disconnected, no current flows, so the potential difference V across the resistor becomes the reference voltage minimum value Vbasemin or less.

According to this embodiment, in addition to the resistor 5 described above, a relay 11 is inserted in series between each exciting coil 1a and the power source P. The relay 11 may be configured as, for example, a mechanical relay switch, or may be configured as a changeover switch including an electronic relay (FET). On the other hand, ON / OF of this relay 11
F is controlled by the output from the memory circuit 10 described above,
For example, when the above-mentioned failure occurs in the exciting coil 1a, the relay 11 is turned off by the signal from the memory circuit 10.
It becomes F, and the power supply to the faulty exciting coil 1a is stopped.

Next, the structure and operation of the device for detecting the failure of the detection coil 1b will be described. The fault identification of the detection coil 1b is basically the same as that of the excitation coil 1a, and the output voltage Vd from each detection coil 1b amplified by the amplifier 2 is sent to the comparator 13 via the detection circuit 12.
Entered in. Then, in each comparator 13, a predetermined reference voltage Vstd (maximum voltage value Vst input from the reference value generator 14 is input.
dmax, minimum voltage value Vstdmin) and the output voltage Vd from the detection circuit 12 are compared, and when the output voltage Vd deviates from the reference voltage Vstd, it is determined that a failure has occurred in the detection coil 1b. The diagnosis result is input to the logical sum circuit 9 provided corresponding to the pair of exciting coils 1a.

In this way, in each OR circuit 9, the output from the comparator 7 corresponding to the exciting coil 1a and the output from the comparator 13 of the detection coil 1b are ORed, and which coil Even if 1a or 1b fails, the result is held in the corresponding memory circuit 10. The excitation coil 1a and the detection coil 1 described above
The failure judgment of b is achieved by the judgment circuit J as a failure sensor judgment means surrounded by a dotted line in FIG.

When a failure occurs in the detection coil 1b, a relay 15 is inserted between each detection coil 1b and the adder 3 in series like the exciting coil 1a. This relay 15
The ON / OFF control is performed by the output from the memory circuit 10 like the relay 11, and if a failure occurs in the corresponding detection coil 1b or the excitation coil 1a, the ON / OFF control is performed together with the corresponding relay 11. It is turned off, and the connection between the detection coil 1b and the adder 3 is cut off.

The output signal from each storage circuit 10 is input to the above-mentioned relays 11 and 15 as well as to the gain adjusting circuit 16 for determining the amplification degree of the torque-corresponding DC voltage Vt in the analog signal processing circuit 4 described above. The circuit 16 determines the amplification degree corresponding to the number of the failed torque sensors 1. That is, for example, if there is an output from the memory circuit 10 indicating that one of the three torque sensors 1 shown in the figure has a failure, the remaining two torque sensors 1 are normal. The final output voltage obtained by the adder 3 is two thirds of that when all the torque sensors 1 are normal.

Therefore, in the gain adjusting circuit 16 by the input from each memory circuit 10, the gain is determined to be the reciprocal of the number of memory circuits storing normal / total number of memory circuits, that is, 3/2 in the above example, Output to the analog signal processing circuit 4. As a result, in the circuit 4, even though one torque sensor 1 is out of order, the added voltage Vt is multiplied by 3/2 as if all the torque sensors 1 are normal. The torque detection continues in the same condition as above. Two torque sensors 1
If the failure occurs, the amplification degree of the output voltage from the remaining torque sensor 1 is tripled, and the reliability of the torque detection value is slightly reduced from that in the normal state, but the torque detection itself is continued.

As described above, the memory circuit 10 according to the present embodiment.
Is the excitation coil 1 for the torque sensor 1 that has failed.
It functions to cut off the connection between a and the power source P and the connection between the detection coil 1b and the adder 3 to prevent an incorrect voltage from being incorporated in the adder 3. The output voltage thus obtained is corrected according to the number of faulty sensors. In addition to this, by outputting it to the alarm display circuit 17, for example, the torque sensor 1 may be notified to the outside of which one is out of order. good.

The system shown in FIG. 2 described above performs a failure diagnosis on both the exciting coil 1a and the detection coil 1b constituting the torque sensor 1, and adjusts the torque calculation value in accordance with the number of failure sensors that have occurred. Is. On the other hand, the block diagram shown in FIG. 3 is a simplified version of the system configuration shown in FIG. In the embodiment described below, the same components as those in the previous embodiment are designated by the same reference numerals.

However, according to the second embodiment, unlike the previous embodiment, the elements related to the failure diagnosis of the exciting coil 1a of the torque sensor 1, that is, the resistor 5, the detection circuit 6, the comparator 7 in FIG. The system in which the OR circuit 9 is removed and the failure diagnosis of only the detection coil 1b is executed. This is because if a failure occurs in a specific exciting coil 1a, naturally the corresponding detecting coil 1b is also affected, and the output voltage becomes an abnormal value, so the output voltage comparison of only the detecting coil 1b is performed. This is because the failure diagnosis of the torque sensor 1 can be easily performed only by itself.

Therefore, unlike the previous embodiment, the device according to the present embodiment has the advantage that the signal from the comparator 13 can be directly input to the storage circuit 10 without going through the OR circuit, and the cost can be reduced. Since the other constituent elements are the same as those in the first embodiment, the description thereof will be omitted. Next, a third embodiment of the present invention will be described with reference to FIGS.
First, regarding the failure determination of the detection coil 1b, the output from each detection coil 1b is input to the switch 18 through the amplifier 2.

The switch 18 has a function of sequentially switching the connection between each of the three sensors 1b and the analog signal processing circuit 4. The switch 18 is composed of a relay or an element (FET) having an electronic switching function. The time when each sensor 1b and the analog signal processing circuit 4 are connected is the same, and the switching timing is controlled by the microcomputer 19.

Here, the output from each sensor 1b is sequentially switched by the switch 18 and input to the analog signal processing circuit 4, and a DC voltage corresponding to the applied torque is output. On the other hand, the output of the switch 18 is input to the detection circuit 12, and the output of the detection coil is converted into a DC voltage. This DC voltage is further converted into a digital signal by the A / D converter 20 and input to the microcomputer 19.

The microcomputer 19 includes the sensors 1
In order to determine the failure of b, the signal converted by the AD converter 20 is compared with the reference value stored in the memory in advance for each sensor. When it is determined that the sensor value is different from the reference value, it is determined that this sensor is out of order, and the microcomputer 19 switches the switch 18
Then, a signal for prohibiting the connection of the faulty sensor is sent, and thereafter, the connection of only the remaining normal sensors is performed by the switch 18.

As a method for determining a failure different from the above-mentioned method, instead of using the reference value stored in the memory in advance, the initial value is first stored in the memory and the initial value is stored. There is also a method of determining a failure when different values are input as compared with. Next, the failure determination of the exciting coil 1a of the apparatus of this embodiment will be described. In this embodiment, as in the first embodiment, three resistors 5 for detecting the current of the exciting coil 1a and a switch 21 for sequentially switching the current supply of each sensor are connected to the exciting coil 1a and the high frequency. It is inserted between the power supplies P.

The voltage across each resistor 5 is input to the detection circuit 6 via the switch 22 and converted into a DC voltage. Here, since the switching device 21 and the switching device 23 are sequentially switched in synchronization, only the current of the coil 1a which is always excited is input to the detection circuit. The voltage generated at both ends of each resistor 5 is passed through the detection circuit 6 to the A / D converter 2
Converted to digital signal at 3 and microcomputer 19
Entered in.

The microcomputer 19 compares it with a reference value stored in the memory in advance, and if it is different from the reference value, it determines that the exciting coil 1a is out of order. The exciting coil 1a may store an initial value in the memory similarly to the detecting coil 1b and compare it with the initial value to determine a failure. When it is determined that there is a failure in this way, the microcomputer 19 issues a command to the switch 21 to stop the current supply to the failed exciting coil 1a, and as a result, the defective exciting coil 1a is completely separated. In this embodiment as well, the microcomputer 19 is used for the alarm display circuit 1.
It is connected to 7 and displays a warning to the outside of the sensor in which an abnormality has occurred.

FIG. 5 shows the above-described switching devices 18, 2 of this embodiment.
The timing of connecting 1 and 22 to each sensor 1 is shown. It should be noted that all the switches 18, 21, 22 are sequentially switched in synchronization. When a current is flowing in the exciting coil 1a of a certain sensor 1, the sensors are sequentially switched so that the signal from the detecting coil 1b of the same sensor is output. When all the sensors are operating normally as shown in FIG. 1-NO. Up to 3 are connected in order. However if sensor N
O. 3 is abnormal, as shown in FIG. 1, NO. Only the sensor NO. 3 is separated.

Although the respective embodiments of the present invention have been described above, the number of torque sensors 1 is not limited to the number shown in the figure.

[0034]

As described above, according to the present invention, even if a failure occurs in any of the plurality of torque sensors constituting the torque detecting device, the operation of the detecting device can be continued. In detecting the torque value, the influence from the faulty torque sensor can be cut off, and thus the reliability of the obtained torque value can be maintained.

[Brief description of drawings]

FIG. 1 is a block diagram corresponding to the claims of the present invention.

FIG. 2 is a schematic device configuration diagram as a first embodiment of the present invention.

FIG. 3 is a schematic device configuration diagram as a second embodiment of the present invention.

FIG. 4 is a schematic device configuration diagram as a third embodiment of the present invention.

5A and 5B are diagrams showing a sensor connection switching timing of the device of the third embodiment, wherein FIG. 5A is a diagram showing a normal state and FIG. 5B is a diagram showing a state when an abnormality occurs.

FIG. 6 is a schematic diagram illustrating the principle of a torque sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Torque sensor 3 ... Adder (torque value calculation means) 4 ... Analog signal processing circuit (torque value calculation means) 11, 15 ... Relay (sensor output interruption means) 16 ... Gain adjustment circuit (calculation correction means) J ... Judgment Circuit (fault sensor discrimination means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shoji Takeuchi, Shoji Takeuchi, Aichi-gun, Nagakute-cho, Aichi Prefecture 1 No. 41 Yokomichi, Toyota Central Research Institute Co., Ltd. (72) Inventor, Yuji Nishibe, Aichi-gun, Nagakute-machi 1 in 41 Chuo-dori, Toyota Central Research Institute Co., Ltd. (72) Inventor Yu Nonomura, Nagakute-cho, Aichi-gun, Aichi Pref. 1-41 in Yokochi Chuo Research Laboratory (72) Inventor Atsushi Tsukada Aichi 1 in 41 Central Road, Nagakute, Nagakute-cho, Aichi Toyota Central Research Institute, Inc. (72) Inventor, Masanori Miyashita 1 in 41 Central Road, Nagakute, Aichi-gun, Toyota Central Research Center, Ltd.

Claims (1)

[Claims] 1. A torque sensor, which is provided in a plurality around a drive shaft, applies a predetermined voltage and outputs an output voltage according to the torque of the drive shaft, and adds each output from the torque sensor. Comparing the torque value calculating means for calculating the torque value of the predetermined axis and the signal from each torque sensor with a reference signal,
A failure sensor determination unit that detects whether or not a failure has occurred in each torque sensor and that specifies the failure torque sensor, and a failure torque sensor and a torque value calculation unit when a failure occurs according to a signal from the failure sensor determination unit. A torque detection device comprising: a sensor output cutoff unit that cuts off the connection; and a torque value correction unit that corrects the torque value in the torque value calculation unit according to the number of faulty torque sensors.