JPH08122175A - Torque sensor - Google Patents

Abstract

PURPOSE: To provide a torque sensor in which a sufficient detection accuracy can be obtained, while shielding and assembling property for electro-magnetism are secured. CONSTITUTION: The torque sensor comprises a body 17 having a sensor part for detecting torque, a metal plate 24 composed of a good electric conductor directly fixed on the body 17, a substrate 25 fixed on the metal plate 24 but not directly fixed on the body 17, and a detection circuit part 27 connected to the sensor part provided on the substrate 25. The detection circuit part 27 is arranged only on one face of the substrate 25 and the other face in contact with the metal plate 24 of the substrate is grounded wholly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a torque sensor used in an electric power steering apparatus mounted on a vehicle or the like to assist steering operation and reduce the force required for steering.

[0002]

2. Description of the Related Art As an electric power steering device for a vehicle or the like, the rotational output of an electric motor, which is an auxiliary steering torque, is reduced by a gear device and transmitted to an output shaft of a steering mechanism to assist the steering force applied to a steering wheel. Then, there is known one configured to steer the wheels.
In such an electric power steering device,
A torque sensor for detecting the steering force transmitted to the input shaft, that is, the torque is provided, and the electric motor is driven according to the detection result of the torque sensor to generate the auxiliary steering force.

As such a torque sensor, for example,
There is a torque sensor as described in Japanese Utility Model Publication No. 2-89336. In this conventional technique, a terminal box provided with a mounting plate on the detection device body, in which a feedthrough capacitor bushing terminal, which is highly effective in reducing high frequency noise components connected to the electric circuit of the detection device body, is attached by soldering It is arranged so as to straddle the opening of the section. At this time, the area of the mounting plate is made smaller than the opening area of the opening. As a result, the workability of soldering is improved, and the plating amount for forming the solder plating layer can be reduced. Therefore,
It is an advantage of the above prior art that workability at the time of soldering the cover and other large parts is improved, and at the same time, cost reduction can be realized.

[0004]

[Problems to be solved] However, even when the bushing terminal is used as described above, the number of man-hours for mounting is still large, which is disadvantageous in terms of workability and cost. Further, since the electrical components of the torque sensor are provided on both sides of the substrate, there is a problem in workability during mounting, and there is a risk that they will fall off to the detection element side.

In the past, a resin plate member was often used as a substrate on which electrical components are mounted, but the resin substrate is a substrate such as a connector for connecting a magnetic sensor as a detection element and a detector body. There is a risk that warping or distortion may occur due to external force applied to the board when the board is inserted or removed. It was also susceptible to thermal expansion.

Further, conventionally, the substrate itself is attached to the detector body, but in this case, there are the following problems. That is, electronic parts are generally weak against stress, and the smaller the size, the stronger the tendency. For this reason, when the substrate has a warp or a distortion, if it is firmly fixed to the main body in order to correct it, the electronic component is affected and, as a result, performance deterioration such as output drift occurs. Further, even when there is no problem when assembled, the performance may be deteriorated later due to thermal expansion or the like.

It is an object of the present invention to provide a torque sensor which has improved assemblability, can suppress the influence of stress, and is low in cost and strong against external noise.

[0008]

In order to achieve the above object, a torque sensor according to the present invention comprises a main body having a sensor portion for detecting a torque, and a metal plate made of metal which is a good electric conductor and is fixed directly on the main body. And a detection circuit section that is fixed on the metal plate but is not directly fixed to the main body, and a detection circuit section that is provided on the board and connected to the sensor section. It is characterized in that it is arranged only on one surface of the substrate, and the other surface of the substrate that comes into contact with the metal plate is grounded entirely.

[0009]

According to the torque sensor of the present invention, all the electronic components are mounted on one surface of the substrate and not arranged on the side of the detection element, so that the noise shielding effect is improved and the assembling property is also improved. In addition, since it is possible to prevent failures due to parts falling off, the reliability of the device is improved and the performance is stable. Since the element that cuts off the high frequency noise component is also mounted on this one surface, the number of soldering steps can be reduced. Furthermore, by utilizing the wide chassis ground on the back surface of the substrate, it is possible to maximize the ability to cut noise. In addition, since the mounting opening has a space and separate rooms, the input / output line (connector), the detection circuit, and the detection element are electromagnetically separated. Furthermore, even if no direct external force is applied to the board (when the connector is disconnected), warpage and distortion of the board can be prevented, and the effect of thermal expansion can be minimized to prevent performance deterioration.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. In the drawings, the same parts are designated by the same reference numerals. FIG. 1 shows a torque sensor 5 according to an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view in the axial direction showing the state in which 0 is attached to the electric power steering device 100.

In FIG. 1, an electric power steering apparatus 100 is inserted and mounted in a cylindrical lower column 22,
An input shaft 10, which is connected to a steering wheel (not shown) via a mechanism (not shown) and transmits the steering force of the steering wheel, is arranged concentrically with the input shaft 11, and a vehicle wheel via a mechanism (not shown). Output shaft 10 for steering
And a torsion bar 18 as an elastic member inserted in the end portions of the input shaft 10 and the output shaft 11 which face each other.

The input shaft 1 in which the torsion bar 18 is inserted.
0 and the end of the output shaft 11 are housed in the main body of the torque sensor 50, that is, the housing 17. The output shaft 11 is rotatably supported by the housing cover 30 of the torque sensor 50 via a bearing 17. The input shaft 10 is rotatably supported by the housing 17. The housing 17 and the housing cover 30 constitute a gear box that houses a gear device and the like.

A cylindrical member 19 is fitted and fixed on the outer periphery of the input shaft 10 and rotates integrally with the input shaft 10. Furthermore,
The cylindrical member 51 slides in the axial direction of the input shaft 10 according to the twist of the torsion bar 18. The detection element of the torque sensor 50, that is, the detection coil 20 that is the sensor unit that detects the torque, has a cylindrical member 1 with a predetermined minute gap therebetween.
It is arranged so as to oppose the outer circumference of 9. Detection coil 2
0 is the detection circuit section 27 of the substrate 25 by the cable 21.
It is connected to the. The torque is detected by changing the relative opposing positions of the detection coil 20 and the cylindrical member 19 in accordance with the sliding of the cylindrical member 19 in the axial direction.

A worm wheel 1 is provided at the end of the output shaft 11.
4 is provided, and the worm wheel 14 meshes with the worm 13 attached to the worm shaft 12 which is the output shaft of the electric motor 15. Therefore, the rotation of the electric motor 15 is transmitted to the output shaft 11 via the gear device 16.

Next, the details of the torque sensor 50 according to the embodiment of the present application will be described with reference to FIGS. 2 and 3. FIG. 2 shows A of FIG.
FIG. 3 is a top view seen from the direction of the arrow, and FIG. 3 is a cross-sectional view of the main part taken along the line BB of FIG. As shown in FIG. 3, the housing 17 has a cylindrical portion 35 having a substantially cylindrical cross section, and two wall portions 31 and 32 integrally protruding from the cylindrical portion 35 and extending in the axial direction. Further, the housing 17 is provided with a step portion 33 adjacent to the wall portion 31. The detection circuit unit 27 is not shown in FIG.

As shown in FIG. 1, the input shaft 10 and the input shaft 1 are provided in the cylindrical portion 35 of the housing 17, which is a good conductor of electricity.
The cylindrical member 19 fitted to 0 and the detection coil 20 facing the cylindrical member 19 are inserted. The output shaft 10 is omitted in FIGS. 2 and 3. At the ends of the walls 31 and 32, a metal plate 24 made of a metal that is a good conductor of electricity and has an opening 37 in the approximate center is arranged. A resin substrate 25 is placed on the metal plate 24. The walls 31 and 32 of the housing 17 and the metal plate 24 define a space 34 in which the cable 21 is accommodated. The cable 21 has a cylindrical portion 35 of the housing 17.
And extends through an opening 36 that opens into the space 34.

On the substrate 25, a detection circuit section 27 composed of a large number of electronic parts is provided. An unillustrated connector unit 28 for an input / output line is mounted on the step portion 33 of the housing 17. Connector unit 2
The main body of 8 is fixed to the metal plate 24, and only the terminal portion 29 of the connector unit 28 is connected to the detection circuit portion 27 on the substrate 25 via the metal plate 24.
Therefore, it is possible to prevent an unnecessary external force from being applied to the substrate 25 when the input / output line is taken in and out of the connector unit 28. The connector unit 28 is connected to the electric motor 15 via a controller (not shown). Therefore, the controller outputs a drive signal based on the detection result of the detection circuit unit 27 to drive the electric motor 15, and as a result, the output shaft 1 is output via the gear device 16.
1 is driven. A cover 23, which is a good conductor of electricity, is provided on the substrate 25 to protect the detection circuit unit 27 and the like from the outside.

The substrate 25 is sized to cover all the openings 37 of the metal plate 24 below it. Detection circuit section 2
Even when the electronic component 7 and the screw for fixing the substrate 25 are dropped due to vibration or the like, the periphery of the substrate 25 is closed by the substrate 25 and the metal plate 24.
Parts are dropped on the side of the detection coil 20 below the substrate 25 and the metal plate 24 to affect the detection, or the parts are bitten in the gear mechanism part of the gear device 16 and other mechanism parts, and the electric power steering device 100. It is possible to prevent damage to the body and hinder the operation.

A high frequency component cutting element 26 such as an inductor or a three-terminal capacitor is provided on the substrate 25, and a detection circuit section 27 is provided.
Between the connector unit 28 and the connector unit 28
It is provided near the door. Therefore, high-frequency noise from the outside that tries to enter from the connector unit 28 via the input / output line is blocked by the high-frequency component cut element 26 and prevented from entering the detection circuit unit 27.

Next, the housing 1 of the torque sensor 50
7, the assembly of the metal plate 24, the substrate 25, the cover 23, and the connector unit 28 will be described with reference to FIG.
First, the connector unit 29 is housed in the stepped portion 33 of the housing 17 with the terminal portion 29 facing upward. Next, the metal plate 24 is placed on the housing 17. In this state, the connector unit 28 is attached to the metal plate 24 and the housing 1.
It is sandwiched between 7 and. The above-described opening 37 and the second opening 40 smaller than the opening 37 are provided in the metal plate 24. The terminal portion 29 of the connector unit 28 is inserted through the second opening 40 and connected to the connecting portion 47 of the substrate 25. The connector unit 28 is directly fixed to the metal plate 24 with screws, and the substrate 25 is not involved in fixing the connector unit. As a result, the substrate 25
No unnecessary force is applied to.

A substrate 25 on which a detection circuit portion 27 (not shown in FIG. 4) is further mounted on the metal plate 24 so as to cover all the openings 37 of the metal plate 24.
This substrate 25 has a screw hole 4 formed by screwing a screw 41 through a hole 42 formed at the end of the substrate 25 into a metal plate 24.
It is fixed to the metal plate 24 by being screwed onto the plate 8.
The terminal portion 29 of the connector unit 28, which is inserted through the second opening of the metal plate 24, is connected to the terminal connecting portion 47 provided at the end portion facing the hole 42.

The metal plate 24 to which the substrate 25 is fixed is
The holes 43 formed at the four corners of the cover 23 are fixed to the housing 17 by screwing the screws 43 aligned with the holes 46 and inserted through the holes 45 formed at the four corners of the cover 23 into the screw holes 44 of the housing. Therefore, the substrate 25 is fixed to the metal plate 24 with a single screw, and is indirectly fixed to the housing 17 by the metal plates 24 screwed to the housing 17 at the four corners. Therefore, since the substrate 25 is not directly screwed to the housing 17, stress such as distortion and warpage applied to the substrate 25 is easily released when the resin substrate 25 is attached, and the substrate 25 and the detection circuit unit mounted on the substrate 25 are easily released. 27 It is possible to prevent the influence of the stress on the electronic components, which are relatively weak against the equal stress, and the deterioration of the performance such as the output drift. Further, since the deformation of the housing 17 and the like due to the thermal expansion and the stress due to the thermal expansion are not affected, it is possible to prevent the performance degradation of the detection circuit unit 27.

The substrate 25 will be described below. Although the substrate 25 is formed of resin as in the conventional case, as is clear from FIGS. 1 and 3, the high frequency component cut element 26 and the detection circuit unit 27, that is, all mounted components such as electronic components are on one surface of the substrate 25. (Only on the upper surface of the substrate 25 in the embodiment). A copper foil is attached to the entire other surface of the substrate 25, that is, the lower surface, and the entire lower surface serves as a ground surface (GND surface). A circuit pattern is also formed on the upper surface of the substrate 25 with copper foil,
Furthermore, electronic parts are mounted on it. Therefore, in this embodiment, since the metal plate 24 contacts the ground surface of the substrate 25, the chassis ground of the main body of the torque sensor 50 can be shared while ensuring a sufficient contact area.

Further, it will be described with reference to FIG. 3 that the torque sensor 50 is constructed so that external noise does not enter the detection circuit section 27. In FIG. 3, high-frequency noise from an input / output line (not shown) of the connector unit 28, which is a high-frequency noise transmission source, is generated by the metal plate 24 and the housing 17.
Since the connector unit 28 is isolated from the wall portion 31 of the above, it does not enter the detection circuit portion 27. Similarly,
Since it is blocked by the wall portion 31, high-frequency noise from the input / output line of the connector unit 28 is detected by the detection coil 20.
It can also be prevented from affecting. That is, in this embodiment, the detection circuit section 27, the connector unit 28, and the detection coil 20 on the upper surface of the substrate 25 are electromagnetically isolated from each other so as not to be influenced by each other. Further, since the high frequency noise cut element 26 is arranged in the vicinity of the connector unit 28, the detection circuit unit 27
The high-frequency component can be effectively blocked in front of.

[0025]

As described above, according to the torque sensor of the present invention, the following effects can be obtained.

Since the substrate is fixed to the metal plate and is not directly fixed to the body of the torque sensor, it is possible to prevent the substrate from being deformed when it is mounted during assembly, and to prevent the stress due to thermal expansion from affecting the substrate. .

Further, since the electronic components including the detection circuit portion are arranged on one surface of the substrate and the other surface is grounded on the whole surface, a good chassis G having a large area can be formed with the main body made of a metal having good electrical conductivity.
ND can be secured.

Therefore, the substrate can be protected from the stress and the external force, the assembling property is improved, and the torque sensor having the improved electromagnetic shielding property can be obtained. In addition, since it is possible to prevent failures due to parts falling off, the reliability of the device is improved and the performance is stable. Furthermore, by utilizing the wide chassis ground on the back side of the board, it is possible to maximize the ability to cut noise.

Furthermore, according to the embodiment, since the connector unit is fixed to the metal plate, it is possible to prevent unnecessary stress from being applied to the board when the connector unit is inserted or removed. Further, since the element that cuts off the high frequency noise component is also mounted on one surface of the substrate on which the detection circuit section is arranged, the number of soldering steps can be reduced.

Further, according to another embodiment, since the connector unit, the detection circuit section, and the sensor section are electromagnetically isolated from each other, the detection circuit section and the sensor section are prevented from radiation noise from the outside. Since they are shielded and separated from each other, they are not affected by external noise. Further, noise and the like conducted to the input / output line (connector unit) are also removed by the high-frequency component cutting element in the immediate vicinity of the terminal, and do not enter the detection circuit section beyond that. Further, the radiation noise near the input / output line (connector unit) is not affected by the noise because it is blocked by the chassis GND (metal plate) and the wall of the main body.

Further, according to another embodiment, it is possible to prevent the harmonic components of the frequencies used in the detection circuit section and the sensor section from leaking to the outside, and do not affect other electric equipment. Furthermore, because they are physically separated (separated into each room), even if parts drop out due to vibration, etc., the screws will approach the sensor part and the sensor will make erroneous detection.・ There is no risk of the steering wheel being locked by the gear.

[Brief description of drawings]

FIG. 1 is a partial axial cross-sectional view of an electric power steering device incorporating a torque sensor according to an embodiment of the present invention.

FIG. 2 is a top view of the torque sensor seen from the direction of arrow A in FIG.

3 is a radial cross-sectional view of the torque sensor taken along the line BB of FIG.

FIG. 4 is an essential part assembly view showing the assembly of the torque sensor.

[Explanation of symbols]

 50 Torque sensor 17 Housing (main body) 24 Metal plate 25 Substrate 27 Detection circuit section

Claims (3)

[Claims] 1. A main body having a sensor section for detecting torque, a metal plate made of a metal that is a good conductor of electricity fixed directly on the main body, and a metal plate fixed on the metal plate but directly on the main body. In a torque sensor including a substrate that is not fixed and a detection circuit unit that is provided on the substrate and connected to the sensor unit, the detection circuit unit is disposed only on one surface of the substrate and the metal plate of the substrate. The torque sensor is characterized in that the other surface that comes into contact is grounded entirely. 2. The torque sensor includes a connector unit for an input / output line having a terminal portion connected to the detection circuit portion, and the connector unit, the detection circuit portion, and the sensor portion are respectively provided. The torque sensor according to claim 1, wherein the torque sensors are electromagnetically isolated from each other. 3. The torque according to claim 1, wherein a high-frequency component cut element is provided on the substrate between the connector unit and the detection circuit section in the vicinity of the connector unit. Sensor.