JPH0715418B2 - Torque detector for power steering - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a torque detection device capable of accurately and non-contactly measuring the axial torque of a steering shaft in a vehicle such as a forklift truck with a compact structure. .

[Prior Art] An electric power steering device such as a forklift truck detects torque acting between an input shaft and an output shaft,
The drive wheels are being steered. This electric power steering device is used, for example, in a battery-operated reach forklift as shown in FIG.
Input shaft 1 connected to and output shaft 2 connected to steering drive wheel 9G
The torque between and is detected by the trick detector 9 and the detection signal is input to the controller 9A. Then, the servomotor 9B is driven by the signal from the controller 9A, the output shaft 2 is driven by the gear mechanism 98, and further, the drive unit 9F, that is, the steering is operated through the chain transmission mechanism 9C, the transmission shaft 9D, and the gear train 9E. Drives drive wheel 9G.

As a conventional torque detecting device for such an electric power steering device, the one shown in Fig. 20 has been proposed (Shokaisho 61-107682). In this torque detecting device 9, a spring joint 90 is provided between the input shaft 1 and the output shaft 2 to convert the relative angular displacement between the two shafts into a linear motion while using a gear. The torque is detected by using the motion direction conversion mechanism 95.

That is, in the torque detection device 9, the large gear of the input shaft 1
Reference numeral 91 meshes with one small gear 93 of the movement direction conversion mechanism 95, and the large gear 92 of the output shaft 2 meshes with the other small gear 94 of the movement direction conversion mechanism 95. The movement direction conversion mechanism 95
Is composed of a cylindrical cam device and includes a roller 951 and the roller 951.
The cam groove 952 into which is fitted. In addition, the above small gear 94
Are integrally connected to a support shaft 941. The support shaft 941 has a cam shaft 96 coaxially therein. And the camshaft
96 rotates integrally with the support shaft 941. Then, the camshaft 2
A potentiometer 97 is provided at the tip of 6. Reference numeral 921 in the figure is a stopper bolt.

Therefore, when the input shaft 1 is rotated left and right by the handle 10, the spring joint 90 is twisted according to the operating force, and a relative angular displacement is generated between the input shaft 1 and the output shaft 2. This displacement is detected by the movement direction conversion mechanism 95 and the potentiometer 97, and the signal is sent to the controller 9A, and the steering drive wheel 9G is driven to the right or left as described above.

[Problems to be solved]

However, as described above, the conventional torque detecting device is provided with large and small gears 91, 93, 92, 94 on the input shaft and output shaft sides, respectively, and a movement direction conversion mechanism using rollers or the like.
95, potentiometer 97 and many other components are required. Therefore, a large space is required for disposing the torque detection device.

When this torque detection device is mounted on a forklift truck or the like, it is arranged in the lower front of the driver's seat (lower of the steering shaft), which adversely affects the operability around the driver's seat and the feet of the driver. Become.

In addition, the conventional torque detection device described above includes a torque-displacement conversion portion (such as the spring joint 90 and gears 91 to 94) and a displacement detection portion (movement direction conversion mechanism 95, potentiometer 97, etc.).
Since there are parts that come in contact and slide, the accuracy is not sufficient, and there is concern about reliability and durability.

In view of such problems, the present invention aims to provide a torque detection device for power steering, which has a compact structure and is capable of performing non-contact measurement with high accuracy.

[Means for solving problems]

The present invention is a torque detection device for detecting a steering wheel input in a vehicle such as a forklift truck,
The input shaft and the output shaft, on which the torque detecting device is mounted, have their front end portions rotatably fitted to each other, and at the fitting portion, a leaf spring is inserted in a direction perpendicular to the axial direction of the output shaft. The input device is configured to be rotated by an input shaft via a leaf spring, and the torque detection device has a detection coil whose inductance changes according to a rotation angle difference due to a rotation torque on the input shaft side and the output shaft side. The solenoid coil and the capacitor, which are arranged so as to face each other and are wound around the rotary shaft of either the input shaft or the output shaft, are connected in series and fixed on the rotary shaft, and these are connected in series. A resonance circuit, and a detection unit having a set of an input coil and an output coil composed of a magnetic core and a coil wound around the magnetic core is provided, and the input coil and the output coil of the detection unit are rotated. The resonance circuit and the detection unit are arranged to face the solenoid coil above with a gap, and an oscillation circuit that oscillates at the resonance frequency of the resonance circuit is formed. A torque detection device for a power steering characterized by detecting as a change.

What should be noted in the present invention is that the leaf spring is provided between the input shaft and the output shaft as described above, and the output shaft is driven through the leaf spring,
Corresponding to the torque by fixing the detection coil whose inductance changes according to the rotational angle difference (rotational angle displacement) due to the torque, facing each other on both shafts, and with a gap facing the solenoid coil. This is because the rotation angle difference is detected as a change in the oscillation frequency.

That is, in the present invention, the input shaft and the output shaft have a leaf spring inserted in the fitting portion in a direction perpendicular to the axial direction, and when the input shaft is rotated by the handle, the output is output via the leaf spring. The shaft is configured to be driven. The leaf spring is composed of a resilient plate-like body such as a spring steel plate.

Further, as the detection coil, as shown in the embodiment,
Using a detector consisting of a magnetic core and a coil wound around it,
Two sets of these detectors are made to face each other and fixed on the input shaft and the output shaft. This facing is the rotation axis (input axis,
Output shaft) in the axial direction. Further, the pair of detectors are connected in series, and the mutual inductance of the pair of detectors changes depending on the rotation angle difference, so that the total inductance of the detection coil changes.

Furthermore, two sets of detection coils are provided, one set of detection coils is connected so that mutual inductance reduces the total inductance, and the other set is connected so that mutual inductance increases the total inductance. The difference or ratio of these two oscillation frequencies can be sent as an output to the resonance circuit (see the third embodiment).

To increase the change in inductance, shorten the coil width to a length equal to or smaller than the coil diameter.
There are means such as shortening the facing distance between the pair of detection coils. Further, it is preferable that the coil diameter is equal to or larger than a diameter at which the areas facing each other become zero at the maximum measurement angle difference of the rotating shafts. For example, if a detection coil having a coil with a diameter of 2.5 mm is fixed on a shaft with a diameter of 50 mm, the circumferential surface moves about 2.5 mm with an angle difference of 6 degrees, and the facing area of the coil disappears (see below. (See Figure 2).

Further, the solenoid coil is constructed by winding a conducting wire on a rotating shaft, and the conducting wire is connected in series with a capacitor and the detection coil. This constitutes a closed resonant circuit. Further, the input coil and the output coil of the detection unit are arranged with a gap facing the solenoid coil on the rotating shaft.

[Action]

In the present invention, when torque is applied to the input shaft due to the rotation of the handle, the leaf spring between the input shaft and the output shaft is compressed, and a rotation angle difference (for example, 3 degrees) is generated between the two shafts. This rotation angle difference is caused by the displacement of the leaf spring. Then, due to the difference in the rotation angle, the total inductance of the detection coil provided so as to face each other between the input shaft and the output shaft changes. this is,
This is caused by a change in the number of magnetic force lines coupled to each other when the facing area of the pair of detection coils changes.

Then, the resonance frequency of the resonance circuit formed on the rotation axis changes due to the change of the total inductance in the detection coil, and the oscillation frequency of the detection unit provided outside the rotation axis changes. Since the amount of change in the inductance of the detection coil corresponds to the amount of torque, the applied torque is detected from the amount of change in the oscillation frequency. Then, the steering drive wheels are driven as described above according to the detected torque.

〔effect〕

According to the present invention, the torque-displacement conversion portion and the displacement detection portion, which are conventionally composed of the spring joint, the gear, the movement direction conversion mechanism, the potentiometer, etc., are separated from the leaf spring, the detection coil, the resonance circuit and the detection portion. And an oscillator circuit. Therefore, the torque detection device can be made extremely compact (small) as compared with the conventional one.

Further, since the detection coil and the resonance circuit are arranged on the rotation axis, the change of the total inductance of the detection coil changes the resonance frequency of the resonance circuit, and the change is non-contact by the detection unit provided outside the rotation axis. Can be detected. Therefore, its detection accuracy and sensitivity are extremely excellent.

Further, since the signal transmission to the detection unit provided outside the rotation axis is transmitted as a frequency by the solenoid coil, the S / N ratio is high and the power of the excitation coil of the detection unit can be reduced.

In the present invention, the provision of a leaf spring between the input shaft and the output shaft and the construction of the transmission circuit are important requirements for having non-separable integrity with respect to their effects. This will be described in detail below.

That is, in the input of the present invention, the torque detection device is constructed compactly as described above. One of the reasons why such compactness has been realized is that the input shaft and the output shaft are connected by a leaf spring. That is,
As a result, the torque detection device could be configured on one axis along with the input shaft and the output shaft. Conventionally, as described above, the axis lines of the input shaft and the output shaft and the movement direction converting mechanism are provided in parallel with the axis lines, so to speak, the torque detecting device is configured on the two axis lines. In the present invention, 1
Since the torque detection device is configured on the axis of the book, not only is the size reduced, but also the outer shape is neat and the mounting space is extremely small.

On the other hand, the leaf spring is useful for compactification as described above, but even if the leaf spring is used instead of the spring joint in the above-mentioned conventional technique, the function of the torque detection device is insufficient. The reason for this is that leaf springs suffer damage such as cracks when attempting to take large displacements, resulting in low durability. Therefore, when the leaf spring is used, a large displacement cannot be taken, and the torque cannot be accurately detected by the device using the gear, the motion direction changing mechanism and the like as in the prior art.

The present invention takes advantage of the compactness of the torque detection device using leaf springs, while solving the drawback that "the displacement cannot be made large" of the leaf springs by means of the oscillator circuit consisting of the resonance circuit and the detection section, which is compact and has high measurement accuracy. It provides a torque detection device having good durability and excellent durability.

As described above, according to the present invention, it is possible to provide a torque detection device for a power steering, which has a compact structure and can accurately detect a rotating shaft torque in a non-contact manner. Moreover, unlike the conventional torque detection device, since no contact or sliding parts are interposed, the accuracy is high, and the reliability and durability are excellent.

〔Example〕

An embodiment of the torque detecting device for power steering of the present invention will be described later (fourth embodiment) with reference to FIGS. 1 to 6 including a mounting state of a leaf spring and an oscillation circuit. Prior to that, an embodiment focusing on the oscillation circuit will be described first.

First Embodiment A torque detection device according to this embodiment will be described with reference to FIGS. 7 to 12.

FIG. 7 is a conceptual diagram showing a resonance circuit and a detection unit in the torque detection device of this example, and FIG. 8 is a rotation angle of the detection coil generated by the displacement of the input shaft and the output shaft via the leaf spring. Fig. 9 shows the difference, Fig. 9 shows the detection coil J,
Oscillation circuit diagram consisting of LC series circuit K, detection unit L and waveform shaping circuit N, FIGS. 10 and 11 are views showing the periphery of the detection coil and detection unit, and FIG. 12 is angular displacement (rotational angle difference) S It is a relationship diagram of an oscillation frequency.

The torque detection device in this example is as shown in FIG.
Detecting coil J provided facing the input shaft 1 and the output shaft 2
And an LC series circuit K fixed to the rotary shaft 1 and a detection unit L provided outside the rotary shaft 1 as one set, and the torque is detected by this.

That is, first, the input shaft 1 and the output shaft 2 are provided with a leaf spring 8 interposed therebetween (see FIGS. 1 to 6 of the fourth embodiment). Then, the detection coil J is a pair of detectors.
It consists of 31,32. As shown in FIG. 10, the detector 31 has a coil formed by winding a conductive wire 312 around a magnetic core 311. This detector 31 is fixed to the end of the input shaft 1 by the fixture 1D.
Fix at 1C. Similarly, the detector 32 is fixed to the end 2C of the output shaft 2 (Fig. 7). Then, both detectors 31 and 32 are arranged so that their axes coincide with each other when no torque is applied to the input shaft.

Next, the LC series circuit K, which constitutes a resonance circuit together with the detection coil, is composed of a solenoid coil 5 wound around the entire circumference of the input shaft 1 and a capacitor 59 connected in series with the solenoid coil 5. Fix on input shaft 1. Then, the detection coil J and the LC series circuit K are connected in series to form a resonance circuit.

Further, as seen in FIG. 9, the detection unit L for detecting the resonance frequency output from the solenoid coil 5 is
It comprises an input coil 6 connected to a driving power supply V and an output coil 7 for transmitting a detected signal. As shown in FIG. 11, the input coil 6 is composed of a magnetic core 61 and a coil 62 wound around the magnetic core 61, and the output coil 7 is composed of a magnetic core 71 and a coil 72 wound around the magnetic core 71. The input coil 6 and the output coil 7 are arranged so as to face the solenoid coil 5, and a gap M is provided between the coils 6 and 7 and the solenoid coil 5.

Next, the detection coil J, the LC series circuit K and the detection unit L are
As shown in FIG. 9, an oscillation circuit that is electrically connected to the waveform shaping circuit N to generate the output f ₀ is formed. Where f ₀
Indicates the resonance frequency. In the figure, 36 is a comparator, 37 is a diode, 38 is a current limiting resistor, and V is a drive power supply.

Then, in the input shaft 1 and the output shaft 2, when the output shaft 2 is rotated by the input shaft 1 and torque is applied to both, the leaf spring 8 is compressed and displacement occurs in both shafts 1 and 2.

As a result, misalignment occurs between the detectors 31 and 32 arranged opposite to both ends 1C and 2C of the input shaft 1 and the output shaft 2.
That is, the rotation angle difference θ is generated as shown in the eighth nest.

Due to the displacement of the facing surfaces, the facing areas of the detectors 31 and 32 in the detecting coil change, and the number of magnetic force lines coupled to each other changes. Therefore, the mutual inductance changes and the total inductance of the detection coil J changes. Along with this, the resonance frequency of the LC series circuit K coupled to the detection coil J changes. With the change, the oscillation frequency in the detection section L changes, and is taken out as the output f ₀ by the circuit shown in FIG.

In the above description, in the detection unit L, the input coil 6
The output signal from the solenoid coil 5 is caught by the output coil 7 and the output coil 7, and is output to the waveform shaping circuit N as described above. The output f ₀ from the waveform shaping circuit is the frequency −
It is output as a voltage signal by a known means such as a voltage converter.

Therefore, since the amount of change in the inductance of the detection coil corresponds to the amount of torque, from the amount of change in the oscillation frequency,
The applied torque can be detected.

FIG. 12 is a curve A showing an example of the relationship between the angular displacement (rotational angle difference) and the oscillation frequency. This example shows the relationship when the input shaft 1 and the output shaft 2 have a diameter of 50 mm, the detectors 31 and 32 have a diameter of 2.5 mm, and the rotation angle difference changes from -6 to +6 degrees. As can be seen from the figure, the oscillation frequency changes by about 5 KHz with a change of ± 6 degrees.

As described above, according to this example, the rotational torques of the input shaft 1 and the output shaft 2 can be detected as inductance changes by the detection coils 31 and 32, and can be taken out of the rotary shaft in a non-contact state. Excellent detection accuracy and sensitivity.
Moreover, since the signal is transmitted from the resonance circuit to the detector by the solenoid coil, the S / N ratio is high and the power of the exciting coil of the detector can be reduced.

Second Embodiment As shown in FIG. 13, this embodiment is different from the first embodiment in that the solenoid coils 50 and 51 and the detectors 65 and 75 are arranged differently.

That is, the solenoid coils 50 and 51 are arranged such that the current flow directions are opposite to each other with respect to the circumferential direction of the rotating shaft, and are connected in series. By arranging the solenoid coil as described above, the input coil 65
And the output coil 75 can be miniaturized. That is,
Both coils 65 and 75 can be configured by small solenoid coils similar to the detection coil, instead of the U-shaped core as in the first embodiment. The coils 65 and 75 are arranged opposite to each other with a gap at an intermediate position between the solenoid coils 50 and 51. Also, in the figure, reference numerals 651 and 751 are magnetic cores and 652 and 752, respectively.
Is a coil.

According to this example, the same effect as that of the first example can be obtained,
The detection unit can be further downsized and the cost can be reduced.

Third Embodiment In this embodiment, as shown in FIGS. 14 to 17, two circuits are provided independently of the configuration shown in the second embodiment. However, this example also shows an oscillator circuit used in the torque detecting device shown in a fourth embodiment described later.

That is, first, the detection coils Jx and Jy are fixed to both ends 1C and 2C of the input shaft 1 and the output shaft 2, respectively (Fig. 14). Then, as shown in FIG. 15, similarly to the second embodiment, the detection coil Jx forms an oscillation circuit together with the LC series circuit Kx and the detection unit Lx. Similarly, the detection coil Jy also forms a circuit together with the LC series circuit Ky and the detection unit Ly.

However, what is important here is that the detection coils Jx and Jy differ as follows. That is, as can be seen in FIG. 14, the detectors 31 and 32 in the detection coil Jx have a direction in which their mutual inductance reduces the overall inductance (hereinafter, referred to as reverse phase), as in the first and second embodiments. Connect to.
On the other hand, the detectors 33 and 34 in the detection coil Jy are the first and second detectors.
Unlike the embodiment, the connection is made in the direction in which the overall inductance increases (hereinafter referred to as the positive phase).

Therefore, in the oscillator circuit (Fig. 15), the oscillation frequencies from the detection units Lx, Ly are processed by the waveform shaping circuits Nx, Ny, as in the oscillator circuit of the first embodiment (Fig. 9). It is taken out as output signals fx and fy, respectively. At this time, since the detection coils Jx and Jy are in the opposite phase and the positive phase as described above, the relationship between the angular displacement and the transmission frequency is
As shown in FIG. 16, a reverse phase output fx is represented by a curve X, and a positive phase output fy is represented by a curve Y. Then, when the difference (fx-fy) of the oscillation frequencies is output, the above relationship is expressed as a curve B shown in FIG. The curve B shows a large change with respect to the angular displacement as compared with the case of only the normal phase or the reverse phase. That is, by arranging the detection coils in two systems, the positive phase and the negative phase, and outputting them,
A large output (difference in oscillation frequency) can be obtained with respect to angular displacement.

Further, according to this example, temperature compensation can also be performed. That is, when one detection coil is used, the oscillation frequency is offset due to temperature change. This is due to the temperature dependence of the ferrite core in the detection coil. And
In both cases of the sex phase and the reverse phase, the temperature dependence of the temperature dependence causes the oscillation frequency to decrease with increasing temperature. Therefore, this temperature dependence can be canceled by taking the output difference between the positive phase and the negative phase as described above. This is the same when the ratio of the positive phase and the negative phase is taken.

As described above, according to this example, the same effects as those of the first and second examples can be obtained, and the difference of the oscillation frequency with respect to the difference of the rotation angle can be obtained and the temperature compensation can be performed, so that the temperature can be more accurately measured. The torque can be detected.

Fourth Embodiment This embodiment is an electric power steering device (Fig. 19 above).
2 shows a torque detecting device applied to the power steering torque detecting device according to the third embodiment of the present invention. This example is the first
This will be described with reference to FIGS.

The torque detection device of this example has a bobbin 85 fixed to the input shaft 1.
And two sets of detection coils Jx and Jy provided facing the tip of the bobbin 85 and the rotor 25 on the output shaft 2 side, and two sets of LC having solenoid coils 50 and 51 wound around the bobbin 85. It consists of a series circuit Kx, Ky and two sets of detectors Lx, Ly consisting of an input coil 65 (Fig. 2) and an output coil 75 (Fig. 1) facing each other with a gap between the bobbin 85. .

That is, first, the upper end of the input shaft 1 is connected to the handle, and the housing 41 is provided below the input shaft 1 via the bearing 42.
The lower end of the housing 41 is rotatably supported on the output shaft 2 via a flange 43 and a bearing 23.

The input shaft 1 is a bobbin which is coaxially fixed to the input shaft 1 by a fixing nut 87 inside the housing 41.
Has 85. The lower end of the output shaft 2 is connected to the drive output side, has upper end portions 27A and 27B having a two-step convex shape on the upper side, and has a base portion 21 on the lower side.

Then, in the recesses 11A and 11B below the input shaft 1, the output shaft 2
The tip portions 27A and 27B are inserted, and an oil-free bearing 271 is inserted between the concave portion 11B and the tip portion 27B in order to smooth the shaft displacement of the input shaft 1 and the output shaft 2. Further, a rod-shaped stopper 28 is provided at the tip portion 27A of the output shaft 2, and the stopper 28 is fitted into a stopper hole (not shown) of the input shaft 1 to protect the leaf spring 8 from the input shaft 1 and the output shaft. Two
The relative angular displacement of is regulated (for example, 6 degrees).

Then, the base 21 of the output shaft 2 is fitted into the opening 11 at the lower end of the input shaft 1, and the leaf spring 8 is interposed between the two. This state is shown in FIGS. 2 to 6.

That is, the long hole 22 of the base 21 and the cutout of the opening 11 of the input shaft 1
A leaf spring 8 is provided between the valve 12 and the valve 12. The leaf spring 8 is formed by arranging arc-shaped springs 82, 82 with their convex portions facing each other, and arranging a flat plate 81 on the outer side thereof. These are elastically fitted between the elongated hole 22 and the cutout portion 12. To do. A cylindrical holder is arranged around the outer periphery of the fitted leaf spring 8, that is, around the opening 11 so that the leaf spring 8 does not protrude and does not hinder the angular displacement of the input shaft and the output shaft. (Not shown).

Further, as shown in FIG. 1, a retainer spring 24 is arranged below the base 21 of the output shaft 2 in the direction of the bobbin 85, and is rotatably arranged below the input shaft 1 by a bearing 26. Support the rotor 25.

Therefore, detectors 32 and 34 of detecting coils are provided at the tip of the rotor 25. Further, at the position facing the detectors 32, 34, the detectors 31, 3 are attached to the flange 86 below the bobbin 85.
Provide 3. Then, the detectors 31, 32 and 33, 34 respectively constitute one set of detection coils Jx and Jy. Further, the solenoid coils 50 and 51 are wound around the outer circumference of the bobbin 85,
Two sets of LC series circuits Kx and Ky are formed. The housing
The sensor board 45 fixed to the bracket 44 of 41 has the LC
Input coil 6 of the detectors Lx, Ly facing the series Kiro, Kx, Ky
5,65 and output coils 75,75 are arranged (Fig. 2). The input coil 65 and the output coil 75 are arranged at an angle of 45 degrees. The sensor substrate 45 is provided with the ends of the input and output coils, and the ends are connected to the waveform shaping circuit N by a lead wire 451.

Since the torque detection device of this example is configured as described above, it has the following effects.

That is, when the steering wheel of the vehicle is turned, the steering input torque is transmitted from the input shaft 1 to the output shaft 2 via the leaf spring 8. When the torque is input, the leaf spring 8 enters a compressed state as shown in FIGS. 5 to 6, and a relative angular displacement occurs between the input shaft 1 and the output shaft 2. At this time, a positional deviation occurs between the detection coils 31 and 33 provided on the flange at the lower end of the bobbin on the input shaft 1 side and the detection coils 32 and 34 provided on the rotor 25 on the output shaft 2 side.

Therefore, the torque can be detected as in the case of the third embodiment. Further, in response to the detected torque, as shown in FIG. 19, the servo motor 9B is operated and the steering drive wheels 9G are rotated. For details of these, refer to the description of the third embodiment and the above-mentioned prior art section.

[Brief description of drawings]

1 to 6 show a torque detecting device for power steering according to a fourth embodiment of the present invention. FIG. 1 is a front sectional view thereof, and FIG. 2 is a sectional view taken along the line AA of FIG. Fig. 3 is an exploded view of the leaf spring installation, Fig. 4 is a perspective view of the leaf spring, Fig. 5 is a view showing the state of the leaf spring at the time of installation, and Fig. 6 is a view showing the state of the leaf spring at the time of displacement.
FIG. 12 shows the first embodiment, FIG. 7 is a conceptual diagram of a torque detection device, FIG. 8 is a diagram showing a difference in rotation angle between a rotation shaft and a detection coil, FIG. 9 is an oscillation circuit diagram, and FIG. 11 is a layout diagram of the detection coil, FIG. 11 is a layout diagram of the detection unit, FIG. 12 is a diagram showing the relationship between the angular displacement and the oscillation frequency, and FIG. 13 is a conceptual diagram of the torque detection device in the second embodiment. 14 to 17 show a third embodiment, FIG. 14 is a conceptual diagram of a torque detection device, FIG. 15 is an oscillation circuit diagram, FIG. 16 is a diagram showing the relationship between angular displacement and oscillation frequency, FIG. 17 is a diagram showing the difference between the angular displacement and the oscillation frequency, and FIG. 18 is a plan view showing a conventional torque detection device.
FIG. 19 is an explanatory diagram of an electric power steering device. 1 …… input axis, 2 …… output axis, 31,32,33,34 …… detector, 41
...... Housing, 45 …… Sensor board, 5,50,51 …… Solenoid coil, 59 …… Capacitor, 6,65 …… Input coil, 7,7
5 …… Output coil, 8 …… Leaf spring, 85 …… Bobbin, J, Jx, Jy …… Detection coil, K, Kx, Ky …… LC series circuit, L, L
x, Ly …… Detector, N, Nx, Ny …… Wave shaping circuit,

Claims (1)

[Claims] 1. A torque detecting device for detecting a steering wheel input in a vehicle such as a forklift truck, wherein an input shaft and an output shaft on which the torque detecting device is mounted are fitted at their front end portions so as to be rotatable with respect to each other. At the same time, a leaf spring is inserted in the fitting portion in a direction perpendicular to the axial direction, and the output shaft is rotated by the input shaft via the leaf spring. The detection coil, whose inductance changes according to the rotation angle difference due to, is placed on the input shaft side and the output shaft side so as to face each other, and is wound around either the input shaft or the output shaft. A solenoid coil and a capacitor are connected in series and fixed on the rotating shaft, and they are connected in series to form a resonance circuit. Further, a magnetic core and a coil wound around the magnetic core are formed. And a detection unit having a set of an input coil and an output coil, each of which includes an input coil and an output coil, and the input coil and the output coil of the detection unit are arranged to face the solenoid coil on the rotating shaft with a gap, respectively, and the resonance circuit A torque detector for power steering, comprising: an oscillation circuit that oscillates at the resonance frequency of the resonance circuit, and detects a rotation angle difference corresponding to torque as a change in the oscillation frequency.