JP3407467B2 - Torque sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor for detecting a torque applied from an input shaft or an output shaft based on a change in magnetic resistance, and more particularly to a torque sensor used in a steering device for an automobile.

[0002]

2. Description of the Related Art Conventionally, there is a vehicle power steering apparatus in which a torque input from a steering wheel or a wheel is detected by a torque sensor and the steering force is controlled based on the torque. As such a torque sensor, for example, as described in Japanese Utility Model Laid-Open No. 1-158936, there is a torque sensor that detects torque by a change in magnetic resistance due to relative rotation of an input shaft and an output shaft.

As shown in FIG. 9, this one has an output shaft 1 connected to a steering wheel and an input shaft 2 connected to a wheel mechanism. The output shaft 1 and the input shaft 2 are connected by a torsion bar 3. ing. A cylindrical member 4 made of a cylindrical magnetic material is fitted to the tip of the output shaft 1, and a tooth profile 4a is formed on the end surface of the cylindrical member 4.

A cylindrical member 5 and a cylindrical member 6 made of a cylindrical magnetic material are fitted to the tip of the input shaft 2 with a gap. The tooth profile 5a is provided on both end surfaces of the cylindrical member 5.
A tooth profile 5b is formed, and a tooth profile 9 is formed on the end surface of the cylindrical member 6 on the side of the cylindrical member 5 like the cylindrical members 4 and 5.

On the other hand, the output shaft 1 is supported by a housing 7 through a bearing, and the housing 7 is formed with an outer shape portion 7a for covering the cylindrical members 4, 5, and 6. A temperature detecting coil 8 and a torque detecting coil 9 are mounted on the inner peripheral surface of the outer shape portion 7a, and the temperature detecting coil 8 is located substantially at the center of the cylindrical members 5 and 6. Further, the torque detection coil 9 is located substantially at the center of the cylindrical members 4 and 5.

In the operation of the torque sensor having the above-described structure, when an exciting current is applied to each of the temperature detecting coil 8 and the torque detecting coil 9, a magnetic flux for torque detection is generated between the cylindrical member 4 and the cylindrical member 5. The passage Z is formed and the magnetic flux passage Y for temperature detection is formed between the cylindrical member 5 and the cylindrical member 6. Here, the magnetic flux passage Z is formed by the relative rotation of the output shaft 1 and the input shaft 2 and thus the cylindrical member 4
And tooth profile 5a and tooth profile 4a formed on the cylindrical member 5
Since the area of the convex portions facing each other changes, the magnetic resistance for passing therethrough changes, so the voltage of the torque detection coil 9 changes. Torque detection is performed using this change.

The magnetic resistance of the magnetic flux passage Y is the cylindrical member 5
Since the cylindrical member 6 does not rotate relative to each other, the areas of the convex portions of the tooth profile 5a and the tooth profile 6a that face each other do not change. Therefore, the voltage across the temperature detecting coil 8 is not affected by the relative rotation of the output shaft 1 and the input shaft 2, but only changes in voltage due to changes in magnetic resistance due to changes in temperature. Therefore, if the voltage of the temperature detecting coil 8 is subtracted from the voltage of the torque detecting coil 9, a voltage according to the torque that is not affected by the temperature characteristic can be obtained.

[0008]

As described above, since the conventional torque sensor has the coil 9 for detecting the torque and the coil 8 for detecting the temperature separately, the structure of the torque sensor is as follows. Was complicated, the torque sensor was increased in size, and the cost was increased. Further, in the conventional torque sensor, the torque detecting coil 9 and the temperature detecting coil 8 are composed of different parts, so that even if the temperature is the same, the magnetic resistance varies among the individual parts. The influence of temperature characteristics had occurred on the obtained torque value.

Therefore, the object of claims 1 and 2 is to simplify the structure of a torque sensor capable of detecting torque and temperature. The object of claim 3 is to eliminate the influence of the temperature characteristics exerted by the component parts and to obtain an accurate numerical value of the torque. Further, an object of claim 4 is to enable temperature detection so as not to affect torque detection.

[0010]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and in the invention of claim 1, a reference DC power source for generating a DC reference current and a reference AC for generating an AC reference current. A power supply, a coil that is selectively connected to the reference DC power supply and the reference AC power supply to generate a magnetic flux in the magnetic path, and a connecting means that selectively connects the reference DC power supply and the reference AC power supply to the coil. Torque detecting means for detecting the torque by detecting the voltage across the coil when the reference AC power source is connected to the coil, and detecting the voltage across the coil when the reference DC power source is connected to the coil And a temperature detecting means for obtaining the temperature of the coil.

Further, in the invention of claim 2, a reference DC power supply for generating a DC reference voltage, a reference AC power supply for generating an AC reference voltage, and the reference DC power supply and the reference AC power supply are selectively connected. A coil for generating a magnetic flux in the magnetic path, connecting means for selectively connecting the reference DC power supply and the reference AC power supply to the coil, and both ends of the coil when the reference AC power supply is connected to the coil. It is provided with a torque detecting means for detecting a current to obtain a torque, and a temperature detecting means for detecting a current at both ends of the coil when the reference DC power source is connected to the coil to obtain a temperature of the coil. is there.

Further, according to the invention of claim 3, there is provided a torque correcting means for correcting the torque obtained by the torque detecting means on the basis of the temperature obtained by the temperature detecting means. Further, in the invention of claim 4, the connecting means monitors the change in the torque obtained by the torque detecting means, and when there is no change in the torque, connects the reference DC power supply and the coil to change the torque. In some cases, a connection control means for connecting the AC / DC power supply and the coil is provided.

[0013]

According to the operation of the invention of claim 1, when the connecting means connects the reference AC power source and the coil, an AC current is supplied to the coil. As a result, magnetic flux is generated in the coil and a magnetic path is formed between the input shaft and the output shaft. At this time, when relative rotation occurs between the input shaft and the output shaft, the magnetic resistance of the magnetic path changes. Since the voltage across the coil changes due to the change in the magnetic resistance, the torque detecting means detects the torque due to the relative rotation between the input shaft and the output shaft.

When the connecting means connects the reference DC power source and the coil, a DC current is supplied to the coil. At this time, the voltage VL across the coil is

[0015]

## EQU1 ## VL = Ri + Ldi / dt. (Here, R is a resistance value and L is a reactance.) According to the equation (1), there is no change in the current supplied by the reference DC power supply, di / dt becomes 0, and the voltage VL is the resistance value R only. Determined by.

Therefore, the voltage across the coil does not change even if there is relative rotation between the input shaft and the output shaft, and the voltage VL across the coil at this time is because the resistance value R depends on the temperature. The temperature detecting means can obtain the temperature from the voltage VL across the coil. In the second aspect, the torque and the temperature are detected by the torque detecting means and the temperature detecting means respectively detecting the alternating current flowing through the coil using the reference direct current voltage source and the reference alternating current voltage source as the power source. To be detected.

According to the third aspect of the invention, the torque correction means corrects the torque obtained by the torque detection means with the temperature obtained by the temperature detection means, so that the torque which is not affected by the temperature change can be obtained. According to the operation of claim 4, the connection control means monitors the change in the torque obtained by the torque detection means, and when there is no change in the torque, the reference DC power supply and the coil are connected to detect the temperature. When there is a change in torque, the AC / DC power supply is connected to the coil.

[0018]

Embodiments of the present invention will now be described with reference to the drawings. In FIG. 1, 10 is an input shaft and 11 is an output shaft. The input shaft 10 is connected to a steering wheel of an automobile (not shown), and the output shaft 11 is connected to a wheel mechanism (not shown) of the automobile.

The input shaft 10 is formed in a cylindrical shape, is rotatably supported by the housing G via a bearing 12, and a torsion bar 13 is arranged on the inner circumference of the input shaft 10. The torsion bar 13 has one end coupled to the input shaft 10 and the other end coupled to the output shaft 11. The torsion bar 13 is twisted to allow relative rotation between the input shaft 10 and the output shaft 11.

As shown in FIG. 1, a gear portion 17 extending in the radial direction is formed on the outer periphery of the tip of the input shaft 10. on the other hand,
A cylindrical hollow portion 18 is formed at the tip of the output shaft 11, and a projection 19 is formed at the tip of the hollow portion 18. The projection 19 meshes with the gear portion 17 formed on the outer periphery of the input shaft 10 with a predetermined gap when the input shaft 10 and the output shaft 11 do not rotate relative to each other,
The rotation amount of the input shaft 10 and the output shaft 11 is regulated to prevent the torsion bar 13 from being damaged.

Further, in the substantially center of the outer periphery of the input shaft 10,
As shown in FIG. 2, a first cylindrical body 15 made of a magnetic material is fixed via a fitting member 14 made of a non-magnetic material,
A tooth portion 16 extending in the axial direction is formed at one end of the first cylindrical body 15. A second cylindrical body 20 made of a magnetic material is pin-coupled to the tip of the protrusion 19, and a tooth portion 21 extending in the axial direction is provided at the free end of the cylindrical body 20 as shown in FIG. It is formed so as to overlap with the tooth portion 16 of the cylindrical body 15 in the axial direction.

A coil 22 is attached to the outside of the tooth portion 16 and the tooth portion 21 in a housing G via a frame body 23 made of a magnetic material. The frame 23 has a U-shaped cross section, and a magnetic path N is formed by the frame 23 surrounding the coil 22, the second cylindrical body 20, and the first cylindrical body 15. In such a configuration, when relative rotation occurs between the input shaft 10 and the output shaft 11, the tooth portion 21 and the tooth portion 1
The overlapping area of 6 changes and the magnetic flux flowing in the magnetic path N changes.

The coil 22 is connected to the electric circuit shown in FIG. In FIG. 3, reference numeral 24 is a reference AC voltage generator, 25 is a reference DC voltage generator, and this reference AC voltage generator 24 generates a sine wave of a predetermined voltage.
The reference DC voltage generator 25 generates a DC wave having a predetermined voltage. The reference AC voltage generator 24 and the reference DC voltage generator 25 are connected to the input terminal sides A and B of a power supply switching device 26 composed of a multiplexer.
Reference numeral 6 supplies an AC voltage or a DC voltage to the output terminal C in response to a switching signal from the CPU 35 described later.

A constant current device 27 is connected to the output terminal C of the power source switching device 26, and the constant current device 27 supplies a constant current to the load side regardless of the load on the load side. The coil 22 is connected to the constant current device 27,
Further, an AC signal processing device 28 and a DC signal processing device 29 are connected in parallel between the constant current device 27 and the coil 22.

The AC signal processing device 28 includes a bias circuit 38, a peak hold circuit 30, and a differential amplifier circuit 3.
1, the DC signal processing device 29 has a differential amplifier circuit 32 as a main component. The bias circuit 38 applies an offset voltage to the input waveform and outputs it to the output side. Further, the peak hold circuit 30 is the bias circuit 3
The maximum value of the waveform output from 8 is held and output.

Further, a differential amplifier circuit 31 of the AC signal processing device 28 and a differential amplifier circuit 32 of the DC signal processing device 29.
Outputs the input value after amplifying it with a predetermined amplification factor. The differential amplifier circuits 31 and 32 are respectively connected to the input terminal sides D and E of the signal switch 33, and the signal switch 33 is output by a switching signal from the CPU 35, which will be described later, like the power switch 26. The signal of the differential amplifier circuit 31 or the differential amplifier circuit 32 is output to the terminal F.

The alternating-current signal processing device 28 and the direct-current signal processing device 29 are connected to a processing device 34, and the processing device 33.
Is mainly composed of a CPU 35, a ROM 36, and a RAM 37. The ROM 36 stores data showing the relationship between the magnetic resistance of the coil 22 shown in FIG. 4 and the torque, and FIG.
The data indicating the relationship between the resistance value and the temperature and the program executed by the CPU 34 are stored.

The data showing the relationship between the magnetic resistance and the torque of the coil 22 shown in FIG. 5 is stored for each temperature of the coil 22. Further, the RAM 37 temporarily stores data necessary for the process of the CPU 35. The operation of the CPU 35 of the processing device 34 having the above configuration is shown in FIG.
The flowchart will be described.

In FIG. 6, step 100 is a step of determining whether or not it is time to detect temperature.
The time variable T1 is compared with the threshold value H, and when the time variable T1 is larger, it is determined that it is the timing for temperature detection, the time variable T1 is cleared to 0 in step 102, and the process proceeds to step 104. When the process proceeds to step 104, it is determined whether or not the steering determination flag set based on the steering determination process shown in FIG.

If the determination flag is 0, it is determined that the steering is not being performed and the process proceeds to step 106. If the determination flag is not 0, it is determined that the steering is being performed and the process proceeds to step 116. Step 106 to step 112 are for coil 22
In step 106, the power switch 26 and the signal switch 33 are operated to operate the coil 22.
A reference DC voltage generator 25 is connected to the processor, and a DC signal processor 29 is connected to the processor 34.

When the DC signal processing device 29 is connected to the processing device 34, the process proceeds to step 108, where the output signal of the DC signal processing device 29 is the voltage VC across the coil 22 and the noise elimination filter and the A / D converter are set. Through CPU3
Read in 5. Then, the process proceeds to step 110, and the resistance value RC of the coil 22 is calculated by the following equation.

[0032]

## EQU2 ## RC = VC / IC Here, IC is a current flowing through the coil 22, and this current IC has a current value predetermined by the constant current device 27. When this resistance value RC is obtained, the routine proceeds to step 112, where the resistance value RC of the coil 22 stored in the ROM 36.
And the temperature S of the coil 22 are obtained from the data indicating the relationship between the temperature S and the temperature S, and stored in the RAM 37.
At 14, the power switch 26 and the signal switch 33 are operated to connect the reference AC voltage generator 24 to the coil 22 and the AC signal processor 28 to the processor 34.

Next, in steps 116 to 118, the torque is calculated based on the relative rotation of the input shaft 10 and the output shaft 11. In step 116, the output signal of the AC signal processing device 28 is read into the CPU 35 as the voltage VT across the coil 22 via the AD converter. When the voltage VT across the coil 22 is read, the process proceeds to step 118 and the temperature S stored in the RAM 37 is read.
Based on the voltage VT across the coil 22 and the data indicating the relationship between the voltage across the coil 22 and the torque stored in the ROM 36, the temperature-corrected actual torque TM is output.

On the other hand, in step 100, the time variable T
1 is compared with the threshold value H, and when the time variable T1 is smaller, the routine proceeds to step 122, where the time constant T2 is added to the time variable T1, and then the input shaft 10 and the output shaft 11 from step 116 to step 118 Only the torque is calculated based on the relative rotation. Then, in step 120, the steering determination shown in FIG. 7 is performed.

This steering determination will be described with reference to FIG.
In step 200, a variable TA indicating the continuous time of non-steering
It is determined whether or not TIME is 0. If it is 0, the process proceeds to step 222, and if it is not 0, the process proceeds to step 202. When the process proceeds to step 202, the variable TATIM is continuously changed.
The minimum actual torque value TM1 within the time from the time when E is determined to be 0 to the present, that is, the time during which it is continuously determined to be non-steering is compared with the current actual torque TM0, and the current actual torque is compared. When TM0 is smaller, the procedure proceeds to step 204, and when TM0 is larger, the procedure proceeds to step 206.

At step 204, the current actual torque T
M0 is stored as the minimum torque TM1. On the other hand, when the routine proceeds to step 206, the maximum actual torque value TM2 and the current actual torque TM0 during the time when it is continuously determined that the steering is not performed.
When the current actual torque TM0 is larger, the routine proceeds to step 208, and when it is smaller, step 21
Go to 0.

At step 208, the current actual torque T
M0 is stored as the maximum torque TM2. Step 21
When it goes to 0, it is determined whether or not the difference between the maximum torque TM2 and the minimum torque TM1 is smaller than the allowable value TMS. If it is smaller, the torque fluctuation is so small that it can be determined that it is in the non-steering state. Then, the process proceeds to step 214, 1 is added to the variable TATIME, and the process proceeds to step 216.

The maximum torque TM2 and the minimum torque TM
When it is determined that the difference of 1 is larger than the allowable value TMS, it is determined that the steering is being performed, and the routine proceeds to step 212, where the variable TATIME
Is cleared to 0. When the process proceeds to step 216, the variable TAT
It is determined whether the duration of IME is longer than the set time VTRT, and if the variable TATIME is larger, it is determined that the temperature can be detected by continuing the non-steering state for a certain period of time, and the variable TATMG is set to 1 in step 218. It is added to determine the temperature detection timing.

When the variable TATIME is smaller, it is determined that the steering state is in effect, and the variable TATMG is cleared to 0 in step 220 to determine that the temperature cannot be detected. On the other hand, in step 200, it is determined that the variable TATIME indicating the non-steering duration is 0, and step 2
At 22, the current actual torque TM0 is set to the initial set value Hi.
It is determined whether or not it is larger than gh. If it is larger than gh, the current actual torque TM0 is changed to the maximum torque TM2 in step 224.
And the minimum torque TM1 is initialized to a value obtained by subtracting 1 from the current actual torque TM0.

In step 222, the current actual torque T
If M0 is smaller than the initial set value High, the current actual torque TM0 is initialized as the minimum torque TM1 in step 226, and the maximum torque TM2 is initialized to a value obtained by adding 1 to the current actual torque TM0. The process ends. By executing the flowcharts of FIGS. 6 and 7, the torque is detected after the temperature is detected during the non-steering, and only the torque is detected during the steering.

Further, the temperature detection may be performed in a predetermined cycle instead of only during the non-steering. In this case, torque cannot be detected if steering is performed during temperature detection.
In this case, it is necessary to make the execution speed of the flowcharts of FIGS. 6 and 7 as fast as possible to reduce the amount of change in the torque generated in one cycle.

In addition to the torque correction of the above embodiment, the detected temperature is used to detect the temperature of a device near the position where the torque sensor is installed, for example, the electric motor for assisting the power steering device. By using the sensor, it is possible to prevent failure due to heat generation of the electric motor. Further, in the above embodiment, the reference AC voltage generator 24
The voltage of the reference DC voltage generator 25 is set to a constant current by the constant current device 27 and the voltage across the coil 22 is detected. However, the present invention is not limited to this, and the reference AC voltage generator 24 and the reference The voltage of the DC voltage generator 25 is applied to the coil 22.
Alternatively, the current of the coil 22 may be detected directly.

In this case, when the reference DC voltage source 25 is connected and steering is performed while temperature detection is being performed, vibration due to a change in magnetic resistance occurs as shown in FIG. A filter is inserted in front of the differential amplifier circuit 32 to remove the vibration component.

[0044]

As described above, according to the present invention, the AC and DC power supplies are switched and connected to one coil so that the temperature and torque can be detected. Therefore, the device can be simplified, and the size and cost can be reduced. it can. Further, by detecting the torque and the temperature with one coil and compensating for the temperature, it is possible to eliminate the error due to the variation in the characteristics of the individual parts, and it is possible to perform the accurate torque detection.

Furthermore, if the temperature is detected when there is no change in the torque, the temperature can be detected without affecting the torque detection.

[Brief description of drawings]

FIG. 1 is a diagram showing an external view of a torque sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing an external view of a torque sensor according to an embodiment of the present invention.

FIG. 3 is an electric circuit diagram for performing temperature detection and torque detection.

FIG. 4 is a diagram showing a relationship between a resistance value of a coil and a temperature.

FIG. 5 is a diagram showing a relationship between magnetic resistance of a coil and torque.

FIG. 6 is a diagram showing an operation of a CPU.

FIG. 7 is a diagram showing an operation of a CPU.

FIG. 8 is a diagram showing a current value at the time of temperature detection in another embodiment.

FIG. 9 is a diagram showing a configuration of a conventional torque sensor.

[Explanation of symbols]

10 input axes 11 Output shaft 13 torsion bar 15 First cylinder 16 teeth 20 Second cylinder 21 teeth 22 coils 24 Reference AC voltage generator 25 Reference DC voltage generator 26 Power switch 28 AC signal processing device 29 DC signal processing device 33 Correction processing device N magnetic passage

─────────────────────────────────────────────────── ───Continued from the front page (56) References JP-A-4-296627 (JP, A) JP-A-5-113375 (JP, A) Practical Development JP-A-158936 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) G01L 3/10

Claims (4)

(57) [Claims] 1. A magnetic path of which magnetic resistance is changed by relative rotation of the input shaft and the output shaft is formed between an input shaft and an output shaft connected via a torsion bar, and the magnetic resistance of the magnetic path. In the torque sensor for detecting the torque by the change of, the reference DC power supply for generating the DC reference current, the reference AC power supply for generating the AC reference current, the reference DC power supply and the reference AC power supply selectively connected to the reference A coil for generating a magnetic flux in a magnetic path, a connecting means for selectively connecting the reference DC power supply and the reference AC power supply to the coil, and a voltage across the coil when the reference AC power supply is connected to the coil. And a temperature for obtaining the temperature of the coil by detecting the voltage across the coil when the reference DC power source is connected to the coil. Torque sensor is characterized in that a means out. 2. A magnetic path of which magnetic resistance is changed by relative rotation of the input shaft and the output shaft is formed between an input shaft and an output shaft connected via a torsion bar, and the magnetic resistance of the magnetic path is formed. In the torque sensor for detecting the torque by the change of, a reference DC power supply that generates a DC reference voltage, a reference AC power supply that generates an AC reference voltage, and the reference DC power supply and the reference AC power supply selectively connected to the reference AC power supply. A coil for generating a magnetic flux in a magnetic path, connecting means for selectively connecting the reference DC power supply and the reference AC power supply to the coil, and a current across the coil when the reference AC power supply is connected to the coil. And a temperature for obtaining the temperature of the coil by detecting the current across the coil when the reference DC power supply is connected to the coil. Torque sensor is characterized in that a means out. 3. The torque correction means for correcting the torque calculated by the torque detection means on the basis of the temperature calculated by the temperature detection means. Torque sensor. 4. The connecting means monitors a change in torque obtained by the torque detecting means. When the torque does not change, the reference DC power source and the coil are connected. When there is a change in torque, The torque sensor according to claim 1, 2 or 3, further comprising a connection control unit that connects the AC / DC power supply and the coil.