JP2006300815A - Rotation angle detector, and torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor which prevents its detection precision from lowering due to changes in temperature. <P>SOLUTION: Expansion amounts of a steel input shaft 23a and a steel output shaft 23b are small, and on the contrary, the expansion amount of a pinion housing 25 made of an aluminum alloy is large. A stator holding member 36 which holds stators 35S, 37S and is made of the aluminum alloy, expands toward the side of a stop ring 38 having flexibility, i.e., in the reverse direction of the pinion housing 25, since a flange 36u is in contact with the upper end surface 25u of a recess 25a of the pinion housing 25. Therefore, the expansion of the pinion housing 25 is reversed with the expansion of the stator holding member 36, and sift amounts of rotors 35R, 37R and the stators 35S, 37S can be made small in the axial direction C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention detects a rotation angle by a rotation angle sensor attached between a first member and a second member which is disposed on the outer periphery of the first member and is formed of a material having a coefficient of thermal expansion different from that of the first member. The present invention relates to a rotation angle detection device and a torque sensor.

2. Description of the Related Art Conventionally, there is known an electric power steering apparatus that reduces the steering force by a steering wheel by applying an assist force by a motor to a steering mechanism connected to a steering shaft. In such an electric power steering apparatus, a torsion bar type torque sensor may be used to detect steering torque.

The configuration of this torque sensor will be described with reference to FIG.
The carbon steel input shaft 23 a and the torsion bar 31 from the steering side are connected by a pin 32. The other end side of the torsion bar 31 is connected to a carbon steel output shaft 23b to the pinion shaft side. The output shaft 23b is rotatably supported in an aluminum alloy housing 25 by a bearing 33. Further, a first resolver 35 and an output shaft 23b are provided between the input shaft 23a and the pinion housing 25. A second resolver 37 is provided between the housing 25 and the housing 25. With this configuration, the input shaft 23a from the steering side and the output shaft 23b to the pinion shaft side can be connected to each other by the torsion bar 31 so as to be relatively rotatable, and the rotation angle (steering angle) of the steering shaft Can be detected by the first resolver 35. Further, the twist amount (corresponding to the steering torque) of the torsion bar 31 can be detected from the angle difference between the first steering angle and the second steering angle.
As an electric power steering apparatus using such a torque sensor, for example, there is Patent Document 1.
JP 2003-327137 A

However, the torque sensor described above with reference to FIG. 7 has a problem that the temperature characteristic is poor, the output of the resolver changes due to temperature change, and the detected torque value changes depending on the temperature.
As a result of the examination of the cause by the present inventor, the input shaft 23a and the output shaft 23b that support the rotors 35R and 37R of the first and second resolvers 35 and 37 are made of carbon steel having a low coefficient of thermal expansion. The housing 25 supporting the 35S and 37S sides is made of an aluminum alloy having a high thermal expansion coefficient, and the relative position in the thrust direction between the rotors 35R and 37R and the stators 35S and 37S is shifted due to temperature change, and the output changes. It came to the conclusion that it is.

The rotation angle detection device of the present invention has been made to solve the above-described problems, and an object of the rotation angle detection device is to provide a rotation angle detection device and a torque sensor whose detection accuracy does not decrease due to a temperature change. is there.

In order to achieve the above object, the invention of claim 1 includes the first members 23a and 23b and the second member formed on the outer periphery of the first member and made of a material having a higher coefficient of thermal expansion than the first member. 25, a support member 33 that is interposed between the first members 23a and 23b and the second member 25 and supports the first member relatively rotatably with respect to the second member,
Inner peripheral side annular bodies 35R and 37R attached to the outer peripheral surfaces of the first members 23a and 23b, and an outer peripheral side attached to the inner peripheral surface of the second member 25 so as to face the inner peripheral side annular body. In the rotation angle detection device 30 including the rotation angle sensors 35 and 37 including the annular bodies 35S and 37S,
The outer peripheral side annular bodies 35S, 37S are cylindrical holding members 36 formed of a material having a larger coefficient of thermal expansion than the first members 23a, 23b, and the support members 33 in two open ends. It is a technical feature that the opening end portion 36u side far from the side is held by the cylindrical holding member 36 fixed to the second member.

The invention of claim 2 includes a first member 23, a second member 25 disposed on the outer periphery of the first member 23 and formed of a material having a smaller coefficient of thermal expansion than the first member 23,
A support member 33 interposed between the first member 23 and the second member 25 and supporting the first member 23 rotatably relative to the second member 25;
An inner peripheral side annular body 35R attached to the outer peripheral surface of the first member 23, and an outer peripheral side annular body 35S attached to the inner peripheral surface of the second member 25 so as to face the inner peripheral side annular body. A rotation angle sensor comprising: a rotation angle sensor 35 comprising:
The inner circumferential annular body 35R is a cylindrical holding member 36 made of a material having a larger coefficient of thermal expansion than the second member 25, and is located on the side farther from the support member 33 at the two open ends. The open end portion 36u side of this is held by a cylindrical holding member 36 fixed to the first member 23, which is a technical feature.

In the invention of claim 3, the steel input shaft 23a is fixed to one end of the torsion bar 31, the steel output shaft 23b is fixed to the other end, and the input shaft 23a and the output shaft 23b are placed in the aluminum alloy housing 25. The rotor 35R and the stator 35S of the first resolver 35 are disposed on the input shaft 23a and the housing 25, and the output shaft 23b and the housing 25 A torque sensor 30 that detects the torque applied to the torsion bar 31 based on the difference in rotation angle obtained between the first resolver 35 and the second resolver 37. In
The stator 35S of the first resolver 35 and the stator 37S of the second resolver 37 are made of an aluminum alloy cylindrical holding member 36, and have an opening end on the side farther from the bearing 33 of the two opening ends. A technical feature is that the portion 36 u side is held by a cylindrical holding member 36 fixed to the housing 25.

In the rotation angle detection device according to the first aspect, since the second member 25 is made of a material having a larger coefficient of thermal expansion than the first members 23a and 23b, the second member 25 is based on the support member 33 when heat is applied. The side expands more thermally than the first members 23a and 23b. Here, the cylindrical holding member 36 that holds the outer peripheral side annular bodies 35 </ b> S and 37 </ b> S is formed of a material having a high coefficient of thermal expansion, and the opening end portion 36 u side far from the support member 33 is fixed to the second member 25. Therefore, the second member 25 is thermally expanded in a direction opposite to the direction in which the second member 25 is deformed with reference to the support member 33. Therefore, the inner circumferential side annular bodies 35R and 37R fixed to the first members 23a and 23b that do not expand greatly even at high temperatures and the cylindrical holding member 36 that cancels the thermal expansion of the second member 25 at high temperatures are retained. The relative positions in the thrust direction of the outer peripheral side annular bodies 35S and 37S do not change so much due to temperature changes, and the outputs of the rotation angle sensors 35 and 37 do not change. For this reason, the accuracy of the rotation angle sensors 35 and 37 is not lowered by a temperature change.

In the rotation angle detection device according to the second aspect, since the second member 25 is made of a material having a smaller coefficient of thermal expansion than the first member 23, the first member 23 side becomes the first with respect to the support member 33 when heat is applied. The thermal expansion is larger than that of the two member 25 side. Here, the cylindrical holding member 36 that holds the inner circumferential side annular body 35 </ b> R is formed of a material having a large coefficient of thermal expansion, and the opening end 36 u side far from the support member 33 is fixed to the first member 23. Therefore, the first member 23 is thermally expanded in the direction opposite to the direction in which the first member 23 is deformed with reference to the support member 33. Therefore, the outer peripheral side annular body 35S fixed to the second member 25 side that does not expand greatly even at high temperatures, and the inner peripheral side held by the cylindrical holding member 36 that cancels the thermal expansion of the first member 23 at high temperatures. The relative position in the thrust direction does not change much with the annular body 35R due to temperature change, and the output of the rotation angle sensor 35 does not change. For this reason, the accuracy of the rotation angle sensor is not lowered by a temperature change.

In the torque sensor 30 according to the third aspect, the housing 25 is formed of an aluminum alloy having a coefficient of thermal expansion greater than that of the steel input shaft 23a and the output shaft 23b. It expands more thermally than the input shaft 23a and the output shaft 23b. Here, the cylindrical holding member 36 that holds the stators 35 </ b> S and 37 </ b> S is formed of an aluminum alloy having a large coefficient of thermal expansion, and the opening end 36 u side far from the bearing 33 is fixed to the housing 25. The housing 25 is thermally expanded in the direction opposite to the direction in which the housing 25 is deformed with reference to the bearing 33. Accordingly, the rotors 35R and 37R fixed to the input shaft 23a and the output shaft 23b side that do not expand greatly even at high temperatures, and the stator 35S held by the cylindrical holding member 36 that cancels the thermal expansion of the housing 25 at high temperatures, With 37S, the relative position in the thrust direction does not change so much due to temperature change, and the output of the resolvers 35 and 37 does not change. For this reason, the accuracy of the resolver is not lowered by a temperature change.

[First embodiment]
Hereinafter, an embodiment of an electric power steering apparatus using a rotation angle detection device and a torque sensor according to a first embodiment of the present invention will be described with reference to the drawings.
First, the main configuration of the electric power steering apparatus 20 will be described with reference to FIGS. 1 and 2. FIG. 1 is an overall configuration of the electric power steering apparatus 20, and FIG. 2 is an enlarged view of an ellipse taken along the alternate long and short dash line II shown in FIG. 1. The electric power steering apparatus 20 mainly includes a steering wheel 21, a steering shaft 22, a pinion shaft 23, a rack shaft 24, a torque sensor 30, a motor 40, a ball screw mechanism 50, and the like. The steering state is detected, and an assist force corresponding to the steering state is generated by the motor 40 to assist the steering by the driver. Note that wheels (not shown) are connected to both sides of the rack shaft 24 via tie rods or the like.

That is, as shown in FIGS. 1 and 2, one end side of a steering shaft 22 is connected to the steering wheel 21, and the other end side of the steering shaft 22 is accommodated in an aluminum alloy pinion housing 25. A carbon steel input shaft 23 a of the pinion shaft 23 and a torsion bar 31 are connected by a pin 32. Further, the carbon steel output shaft 23b of the pinion shaft 23 is connected to the other end side 31a of the torsion bar 31 by spline coupling.

The output shaft 23b is rotatably supported in the pinion housing 25 by a bearing 33. Further, between the input shaft 23a and the pinion housing 25, a rotor 35R and a stator 35S of the first resolver 35 are also provided. A rotor 37R and a stator 37S of the second resolver 37 are provided between the output shaft 23b and the pinion housing 25, respectively. The first resolver 35 and the second resolver 37 can detect the steering angle by the steering wheel 21 and are electrically connected to an ECU (not shown) via a terminal 39.

A pinion gear 23c is formed at an end portion of the output shaft 23b of the pinion shaft 23, and a rack groove 24a of the rack shaft 24 is coupled to the pinion gear 23c so as to be meshed. Thus, a rack and pinion mechanism is configured.

With this configuration, the steering shaft 22 and the pinion shaft 23 can be connected to each other by the torsion bar 31 so as to be relatively rotatable, and the rotation angle of the steering shaft 22, that is, the rotation angle of the steering wheel 21 is set to the first angle. It can be detected by the resolver 35. Further, the twist amount of the torsion bar 31 (corresponding to the steering torque) can be detected as the twist angle from the angle difference between the first steering angle and the second steering angle.

The rack shaft 24 is housed in a rack housing 26 and a motor housing 27, and a motor 40 is disposed in the middle thereof, and a ball screw mechanism 50 is provided that can move the rack shaft 24 in the axial direction by rotation of the motor. It has been. In other words, the ball screw mechanism 50 can convert the forward / reverse rotation torque of the motor 40 into a reciprocating motion in the axial direction of the rack shaft 24. As a result, the reciprocating motion becomes an assist force that reduces the steering force of the steering wheel 21 via the pinion shaft 23 that constitutes the rack and pinion mechanism together with the rack shaft 24.

The first resolver 35 and the second resolver 37 in FIG. 2 are enlarged and shown in FIG.
The rotor 35R of the first resolver 35 is held near the lower end of the input shaft 23a, and the rotor 37R of the second resolver 37 is held near the upper end of the output shaft 23b. On the other hand, the stator 35 </ b> S of the first resolver 35 and the stator 37 </ b> S of the second resolver 37 are fixed to the inner peripheral surface of the pinion housing 25 while being held by the stator holding member 36.

4A shows a cross-sectional view of the pinion housing 25, and FIG. 4B shows a cross-sectional view of the stator holding member 36. As shown in FIG. The stator holding member 36 is formed in a cylindrical shape made of the same aluminum alloy as the pinion housing 25, and flanges 36u and 36d directed to the inner peripheral side are provided at the upper end and the lower end. The distance D1 between the upper end side flange 36u and the lower end side flange 36d is set to be larger than the sum of the height D2 and the height D3 of the stator 35S and the stator 37S, and as shown in FIG. The stator 37S is held with a slight gap between the upper end side flange 36u and the lower end side flange 36d. In order to fix the stator holding member 36, a substantially cylindrical concave portion 25 a is formed on the inner periphery of the pinion housing 25, and the upper end surface 25 u of the concave portion 25 a abuts on the upper end side flange 36 u of the stator holding member 36. It is formed in a horizontal shape. At the lower end of the recess 25a, a ridge groove 25d for accommodating the retaining ring 38 having a wedge-shaped cross section shown in FIG. 3 is formed. The groove 25d is inclined at the lower end surface. The retaining ring 38 is a circlip made of a flexible metal. As shown in FIG. 3, the upper end side flange 36u of the stator holding member 36 is formed by the upper end surface 25u of the recess 25a by the retaining ring 38 having a tapered cross section. It is pressed to the side.

FIG. 5 is a schematic view for explaining thermal deformation in the torque sensor.
The input shaft 23a and the output shaft 23b to which stress is applied are made of carbon steel having a low coefficient of thermal expansion, and deformation due to temperature change is small. On the other hand, the pinion housing 25 to which no stress is applied is made of an aluminum alloy having a large thermal expansion coefficient for weight reduction, and is greatly deformed by a temperature change. A pinion housing 25 is fixed to the vehicle side, and an output shaft 23b is rotatably supported via a bearing 33. The input shaft 23a is rotatably supported by the output shaft 23b via a rotation stopper 34a and a metal 34b, and is fixed to the torsion bar 31 via a pin 32 as shown in FIG.

FIG. 5 is a diagram for explaining a shift in the axial direction, that is, a thrust direction, between the rotors 35R and 37R of the first resolver 35 and the second resolver 37 and the stators 35S and 37S. For this reason, the linear expansion amount in the direction of the axis C of the input shaft 23a, the output shaft 23b, and the pinion housing 25 with the bearing 33 as the center is schematically indicated by arrows. When the temperature in the engine room rises while the vehicle is traveling, the input shaft 23a and the output shaft 23b linearly expand as indicated by arrows in the figure, but the amount of linear expansion is small because they are made of carbon steel. On the other hand, since the pinion housing 25 is made of an aluminum alloy, it linearly expands greatly. However, the stator holding member 36 that holds the stators 35S and 37S is made of an aluminum alloy, and the upper end side flange 36u is in contact with the upper end surface 25u of the recess 25a of the pinion housing 25. It linearly expands in the direction opposite to the linear expansion direction of the ring 38 side, that is, the pinion housing 25. That is, the linear expansion of the pinion housing 25 can be canceled by the linear expansion of the stator holding member 36, and the amount of deviation in the axis C direction between the rotors 35R and 37R and the stators 35S and 37S can be reduced.

In particular, in the configuration of the first embodiment, the input shaft 23a is fixed to the torsion bar 31 via a pin 32 as shown in FIG. Therefore, the lower end side of the input shaft 23a linearly expands in the direction opposite to the direction in which the steel torsion bar 31 linearly expands (upward in FIG. 5) with the bearing 33 as the center. Since the linear expansion of the torsion bar 31 and the linear expansion of the input shaft 23a cancel each other, the displacement amount of the rotor 35R is particularly small. For this reason, by taking the said structure, the deviation | shift amount of the axis line C direction of the rotor 35R and the stator 35S can be made small.

In the torque sensor of the first embodiment, the rotor 35R, 37R fixed to the input shaft 23a and the output shaft 23b side that does not expand greatly even at high temperatures, and the stator holding member 36 that cancels thermal expansion of the pinion housing 25 at high temperatures. The relative positions in the thrust direction do not change so much with the stators 35S and 37S held by the temperature, and the outputs of the first and second resolvers 35 and 37 do not change. For this reason, the accuracy of the first and second resolvers 35 and 37 is not lowered by a temperature change.

[Second Embodiment]
FIG. 6 is a configuration diagram illustrating a configuration of the rotation angle detection device according to the second embodiment.
In the torque sensor described above with reference to FIGS. 2 to 5, the shaft side is made of carbon steel having a low coefficient of thermal expansion, and the housing side is made of an aluminum alloy having a high coefficient of expansion. On the other hand, in the second embodiment, the shaft 23 side is made of a high expansion coefficient aluminum alloy, and the housing 25 side is made of a low thermal expansion coefficient carbon steel. In the rotation angle detection device of the second embodiment, the shaft 23 is rotatably held with respect to the housing 25 via a bearing 33. A recess 23d is formed in the shaft 23, and a rotor 35R of a resolver 35 is attached via a rotor holding member 36 made of aluminum alloy. In the rotor holding member 36, the flange 36u on the upper end side of the rotor holding member is pressed against the upper end surface 23u of the recess 23d by a flexible retaining ring 38. On the other hand, a stator 35 </ b> S of a resolver 35 is fixed to the inner peripheral surface of the housing 25.

When the temperature rises, the pinion housing 25 linearly expands as indicated by an arrow in the figure, but since it is made of carbon steel, the amount of linear expansion is small. On the other hand, since the shaft 23 is made of an aluminum alloy, it linearly expands greatly. However, since the rotor holding member 36 that holds the rotor 35R is made of an aluminum alloy and the flange 36u is in contact with the upper end surface 23u of the recess 23d of the shaft 23, the flexible retaining ring 38 side, That is, linear expansion is performed in the direction opposite to the linear expansion direction of the shaft 23. That is, the linear expansion of the shaft 23 can be canceled by the linear expansion of the rotor holding member 36, and the amount of deviation in the thrust direction between the rotor 35R and the stator 35S can be reduced.

In the above-described embodiment, an example in which a resolver is used as the rotation angle sensor has been described. However, the configuration of the present invention may include, for example, a rotation angle such as an optical rotation angle sensor using a slit plate and a photo interrupter, a magnetic type, and a rotary encoder. Needless to say, the present invention can also be applied to sensors and the like.

It is a lineblock diagram showing the composition of the electric power steering device concerning a 1st embodiment of the present invention. FIG. 2 is an enlarged view inside an ellipse by a dashed line II shown in FIG. 1. FIG. 3 is an enlarged view of a first resolver and a second resolver in FIG. 2. (A) is sectional drawing of a pinion housing, (B) is sectional drawing of a stator holding member. It is a schematic diagram explaining the thermal deformation in a torque sensor. It is a block diagram which shows the structure of the torque sensor of 2nd Embodiment. It is a block diagram which shows the structure of the torque sensor of a prior art.

Explanation of symbols

20 Electric Power Steering Device 23 Pinion Shaft 23a Input Shaft 23b Output Shaft 23c Pinion Gear 24 Rack Shaft 25 Pinion Housing 30 Torque Sensor 31 Torsion Bar 33 Bearing 35 First Resolver 35S Stator 35R Rotor 36 Rotor Holding Member, Stator Holding Member 37 First 2 resolver 37S stator 37R rotor

Claims (3)

A first member, and a second member disposed on the outer periphery of the first member and formed of a material having a larger coefficient of thermal expansion than the first member;
A support member interposed between the first member and the second member, and supporting the first member so as to be relatively rotatable with respect to the second member;
A rotation angle composed of an inner peripheral side annular body attached to the outer peripheral surface of the first member and an outer peripheral side annular body attached to the inner peripheral surface of the second member so as to face the inner peripheral side annular body. A rotation angle detection device comprising a sensor,
The outer peripheral side annular body is a cylindrical holding member made of a material having a larger thermal expansion coefficient than the first member, and the opening end portion side of the two opening end portions far from the support member is The rotation angle detecting device is held by a cylindrical holding member fixed to the second member. A first member, and a second member disposed on the outer periphery of the first member and formed of a material having a smaller coefficient of thermal expansion than the first member;
A support member interposed between the first member and the second member, and supporting the first member so as to be relatively rotatable with respect to the second member;
A rotation angle composed of an inner peripheral side annular body attached to the outer peripheral surface of the first member and an outer peripheral side annular body attached to the inner peripheral surface of the second member so as to face the inner peripheral side annular body. A rotation angle detection device comprising a sensor,
The inner peripheral annular body is a cylindrical holding member made of a material having a larger coefficient of thermal expansion than the second member, and an opening end on the side farther from the support member of the two opening ends The rotation angle detection device, wherein the side is held by a cylindrical holding member fixed to the first member. A steel input shaft is fixed to one end of the torsion bar, a steel output shaft is fixed to the other end, and the input shaft and the output shaft are rotatably supported through a bearing in an aluminum alloy housing. A rotor and stator of a first resolver are disposed on the input shaft and the housing, and a rotor and stator of a second resolver are disposed on the output shaft and the housing, and the first resolver and the second resolver are disposed. In the torque sensor that detects the torque applied to the torsion bar based on the difference in rotation angle obtained in
The stator of the first resolver and the stator of the second resolver are made of an aluminum alloy cylindrical holding member, and an opening end side far from the bearing of two opening ends is in the housing. A torque sensor characterized in that the torque sensor is held by a cylindrical holding member fixed thereto.

Images