JP2000356559A - Torque-detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always accurately detect torque without being affected by temperature change by generating difference in the output of opposing magnetic sensors due to a rotary phase difference being generated in input and output shafts, and detecting a rotary torque from the output difference. SOLUTION: When steering operation is made, an input shaft 2 is rotated around an axis according to the operation direction, and an output shaft 3 also rotates around the axis via a torsion bar 6. Since the load or the like of a steering wheel is applied to the output shaft 3, the torsion bar 6 is twisted according to the steering operation force and relative rotary phase difference is generated between the input and output shafts 2 and 3. Therefore, the output change in a magnetic sensor 10 precedes, and that of a magnetic sensor 11 follows it. Also, the larger the steering operation force, namely a rotary torque given to the input shaft 2 is, the larger the difference between the output of both the magnetic sensors 10 and 11 becomes. And a signal-processing circuit 12 performs operation for obtaining the output difference of both the inputted magnetic sensors. By obtaining the output difference, the amount of influence to both the output due to temperature change is cancelled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a torque detecting device in a power steering device and the like.

[0002]

2. Description of the Related Art In a power steering apparatus, an input shaft connected to a steering wheel and an output shaft directly connected to a rack / pinion gear or the like are connected via a torsion bar. In such a configuration, the torsion bar is twisted according to the steering force applied to the input shaft, and a relative rotational phase difference occurs between the input shaft and the output shaft.
By generating the steering assist force according to the phase difference, light steering can be performed. For example, Tokuho 7-21
In the conventional torque detection device for a power steering device described in Japanese Patent No. 433,433, a toothed projection formed on an end face of a cylindrical member at equal intervals is attached to an input shaft and an output shaft, respectively. They are arranged to face each other. Then, the facing area of the tooth-shaped projection is changed by the rotational phase difference between the input shaft and the output shaft, and the magnetic resistance is changed. Due to this change in the magnetic resistance, the voltage induced in the magnetic coupling detection coil (magnetic sensor) provided near the tooth-like projection changes. The torque can be detected from this voltage.

[0003]

However, such a conventional torque detecting device as described above is expensive because it is not easy to manufacture a cylinder having tooth-like projections with high precision. Also, since the magnetic sensor as described above is originally susceptible to a change in temperature, there is a difference in accuracy in detecting the rotational phase due to the change in temperature.

[0004] In view of the above-mentioned conventional problems, an object of the present invention is to provide a torque detecting device which has a configuration which is easy to manufacture and which is hardly affected by a temperature change on detection accuracy. .

[0005]

A torque detecting device according to the present invention is mounted eccentrically on an input shaft to which a rotational torque is applied, and the first detecting plate made of a magnetic material and the input shaft are provided via a torsion bar. A second detection plate, which is eccentrically attached to an output shaft disposed coaxially with the shaft and has the same or similar outer shape as the first detection plate, and a second detection plate facing the first detection plate; And a first magnetic sensor disposed in a manner opposed to the second detection plate, and having the same relative positional relationship between the first magnetic sensor and the first detection plate. A second magnetic sensor that configures a positional relationship with respect to the second detection plate; and a second magnetic sensor that is provided to the input shaft based on a difference between an output of the first magnetic sensor and an output of the second magnetic sensor. Signal processing means for detecting the applied rotation torque, That.

In the torque detecting device configured as described above, when the input shaft rotates, the output shaft rotates following the twist of the torsion bar according to the rotation torque. Due to the torsion of the torsion bar, a rotational phase difference occurs between the input shaft and the output shaft. When the detected plate is eccentric and a rotational phase difference is generated, the distance between the magnetic plate and the magnetic sensor facing each other is different between the first detected plate and the second detected plate. There is a difference in sensor output. The signal processing means detects the rotational torque from the difference.

In the above torque detecting device, the detected plate may have a circular outer shape, and a magnetic sensor may be arranged at a predetermined distance from an outer peripheral end surface of the plate. In this case, the distance from the opposing magnetic sensor changes smoothly and stably, and linearity in the output characteristics of the magnetic sensor is ensured.

[0008]

FIG. 1A is a sectional view showing an example in which a torque detecting device according to an embodiment of the present invention is provided in a power steering device. In the figure, an input shaft 2 connected to a steering wheel (not shown) and an output shaft 3 directly connected to a rack and pinion gear (not shown) are connected to a gear box 1 of a power steering device via ball bearings 4 and 5, respectively. It is supported rotatably. The input shaft 2 and the output shaft 3 are arranged coaxially with each other, and are connected to each other by a torsion bar 6. That is, the torsion bar 6 is fixed to the input shaft 2 at the upper end by the pin 7 and spline-coupled to the output shaft 3 at the lower end.

A donut-shaped detection plate 8 made of a magnetic material is fitted on the input shaft 2. In addition, this detected plate 8
A detection plate 9 made of a magnetic material having the same outer shape as that described above is externally fitted to the output shaft 3. In the present embodiment, the outer diameter of the input shaft 2 and the outer diameter of the output shaft 3 are the same. Therefore, 2
The detected plates 8 and 9 have exactly the same shape. FIG. 1B shows detection plates 8 and 9 and a magnetic sensor (magnetic coupling detection coil, Hall IC, etc.) 1 arranged opposite thereto.
The positional relationship of 0 and 11 on a plan view is shown. The detection plate 8 and 9, the center O ₂ of the outer circle is eccentric with respect to the center O ₁ of the inner circumference. Therefore, the width (radial thickness) of the detected plates 8 and 9 ranges from the maximum W1 to the minimum W2,
It is changing smoothly.

The pair of magnetic sensors 10 and 11 are mounted on the inner wall of the gear box 1, and the mounting positions in the circumferential direction of the inner wall are also the same. (A) and (b)
As shown in (1), when the input shaft 2 is in the neutral state, the magnetic sensors 10 and 11 are arranged to face the end faces of the phase positions where the detected plates 8 and 9 have the maximum width W1. The distance (gap) between the detected plates 8 and 9 and the magnetic sensors 10 and 11 at this phase position is the minimum value d1, and the distance increases with the rotation of the input shaft 2 and the output shaft 3. When the input shaft 2 and the output shaft 3 are rotated by 180 degrees from the illustrated state, the distance becomes the maximum value. Therefore, the outputs of the magnetic sensors 10 and 11 are maximum when the detected plates 8 and 9 are at the illustrated positions, and are minimum when the detected plates 8 and 9 are rotated 180 degrees therefrom.

The magnetic sensors 10 and 11 are gear box 1
Is connected to a signal processing circuit 12 provided outside the device, where an operation for calculating a difference between the two outputs is performed, and an output based on the difference is output from the signal processing circuit 12. Based on this output, a steering assisting force is generated by a known mechanism (not shown). The magnetic sensors 10 and 11 are:
Of the same type. Therefore, both the output characteristics and the temperature characteristics match.

In the torque detecting device configured as described above, when the steering operation is performed, the input shaft 2 rotates around the axis according to the operation direction. The rotation of the input shaft 2 is transmitted to the output shaft 3 through the torsion bar 6, and the output shaft 3
Rotates around the axis. Since the load of the steered wheels is applied to the output shaft 3, the torsion bar 6 is twisted according to the steering operation force, and a relative rotation phase difference occurs between the input shaft 2 and the output shaft 3. Therefore, as shown in FIG. 2, the output change (solid line) of the magnetic sensor 10 precedes and the magnetic sensor 11
(Dotted line) follows this. Also,
As the steering operation force, that is, the rotational torque applied to the input shaft 2 increases, the difference between the output of the magnetic sensor 10 and the output of the magnetic sensor 11 increases. This difference is obtained by the signal processing circuit 12, and a steering assist force is generated based on the difference. For example, in FIG. 2, an output difference ΔP is obtained for a certain steering amount.

In the output change curve during one rotation of the input shaft 2, a portion A shown in the figure is based on the fact that the distance between the detected plate 8 and the magnetic sensor 10 changes smoothly and stably. This is a linearity region with high linearity. At this time, the detected plate 9 and the magnetic sensor 1 are rotated by the rotation of the output shaft 3.
The linearity with the distance 1 is also high in a similar manner. Therefore, the output difference ΔP particularly in this linearity region has high reliability, and therefore, the accuracy of torque detection is high.
Detected plates 8 and 9 and magnetic sensor 10 facing them
The distance between the magnetic sensors 10 and 11 is set to a predetermined value while observing the output waveforms of the magnetic sensors 10 and 11 so that the linearity region can be secured as long as possible.

As described above, by taking the output difference between the pair of magnetic sensors 10 and 11, the magnetic sensors 10 and 1 are obtained.
1, even if the change in temperature affects the output, this influence is offset and the output difference ΔP is not affected.
Therefore, according to the torque detection device described above, it is possible to always accurately detect torque without being affected by a temperature change.
Further, since the signal processing circuit 12 simply takes the output difference between the pair of magnetic sensors 10 and 11, the circuit is extremely simple and the number of parts is small. Also, the detected plates 8 and 9
Is a simple magnetic member, and can be easily manufactured at low cost.

In the above embodiment, the input shaft 2
3 and 3, the detection plates 8 and 9 are mounted so as to be in the same phase with each other, and the magnetic sensors 10 and 11 are mounted at the same position in the circumferential direction of the inner wall of the gear box 1. It is not limited to the mounting form. In short, since the relative positional relationship between the detected plate 8 and the magnetic sensor 10 and the relative positional relationship between the detected plate 9 and the magnetic sensor 11 are the same as each other, the torsion bar 6 If the input shaft 2 and the output shaft 3 rotate in synchronization with no twist, the magnetic sensor 10
And 11 should just match each other. For example, the detected plate 9 and the magnetic sensor 1 in FIG.
With regard to the mounting of 1, the position may be shifted from the illustrated position by a fixed angle phase in the rotation direction of the output shaft 3. Further, in the above embodiment, the outer shape of the detected plate 8 and the outer shape of the detected plate 9 are the same, but one outer shape may be similar to the other outer shape. Of course, also in this case, when the input shaft 2 and the output shaft 3 rotate synchronously on the assumption that there is no torsion of the torsion bar 6, the outputs of the magnetic sensors 10 and 11 may coincide with each other. is necessary.

Although the torque detecting device in the above embodiment is applied to a power steering device, it goes without saying that the torque detecting device can also be applied to a device having a similar torque transmitting structure.

[0017]

The present invention configured as described above has the following effects. According to the torque detecting device of the first aspect, when the detected plate is eccentric, when a rotation phase difference occurs between the input shaft and the output shaft, the distance between the opposed magnetic sensor and the first detected plate is reduced. The second detection plate and the second detection plate are in different states, and the output of the two magnetic sensors is different. The signal processing means detects the rotational torque from the difference. Therefore, the configuration of the detection target plate is simple, and manufacture is easy.
Further, the difference based on the temperature characteristic of the magnetic sensor cancels out the error, so that the torque can be detected with a constant accuracy regardless of the temperature.

According to the torque detecting device of the present invention, the distance between the magnetic sensor and the opposing magnetic sensor changes smoothly and stably, and the linearity of the output characteristics of the magnetic sensor is ensured. Can be detected.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating an example in which a torque detection device according to an embodiment of the present invention is provided in a power steering device, and FIG. 1B is a diagram illustrating a detection target plate and an opposing plate; FIG. 5 is a plan view showing a positional relationship with a magnetic sensor.

FIG. 2 is a waveform chart showing output characteristics of the magnetic sensor.

[Explanation of symbols]

 2 input shaft 3 output shaft 6 torsion bar 8, 9 plate to be detected 10, 11 magnetic sensor 12 signal processing circuit

Claims (2)

[Claims] 1. An eccentrically mounted input shaft to which a rotational torque is applied, eccentrically mounted on a first detection plate made of a magnetic material, and an output shaft arranged coaxially with the input shaft via a torsion bar. A second detection plate that is attached and has the same or similar outer shape as the first detection plate, and a first magnetic sensor that is disposed to face the first detection plate; The first magnetic sensor and the first detection plate are disposed so as to face the second detection plate, and have the same relative positional relationship as the relative positional relationship between the first magnetic sensor and the first detection plate with respect to the second detection plate. And a signal processing means for detecting a rotational torque applied to the input shaft based on a difference between an output of the first magnetic sensor and an output of the second magnetic sensor. A torque detector, comprising: 2. The torque detecting device according to claim 1, wherein the plate to be detected has a circular outer shape, and the magnetic sensor is arranged at a predetermined distance from an outer peripheral end surface thereof.