JPH0575971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a torque sensor, and particularly provides a torque sensor suitable for application to an electric power steering device of an automobile.

[Conventional technology]

2. Description of the Related Art Electric power steering devices are being developed that assist the power to operate the steering wheels of automobiles. This is designed to detect rotational torque applied to the steering wheels and rotate an electric motor provided in the steering mechanism in accordance with the detected torque.

By the way, as this torque detection means, for example, a torque sensor having a structure shown in FIG. 3 has been developed. FIG. 3 is a half-cut partial sectional view of the torque sensor. An upper shaft 1a to which a steering wheel (not shown) is attached is concentrically connected via a torsion bar 1b to a lower shaft 1c to which a steering mechanism (not shown) is attached. A first sleeve 2 made of a non-magnetic material is fitted and fixed onto the upper shaft 1a, and cylinders 3 and 4 made of magnetic material are fitted and fixed onto the first sleeve 2 at an appropriate distance apart in the axial direction. Each shaft end surface of the cylinder 3 is connected to the upper shaft 1.
It is a plane perpendicular to the axis of a.

The shaft end surface of the cylinder 4 facing the cylinder 3 is a plane perpendicular to the axial center of the upper shaft 1a, and the shaft end surface on the opposite side has a predetermined inclination angle to the axial center of the upper shaft 1a and is non-perpendicular. Furthermore, the plane is asymmetrical with respect to the axis.

That is, the cylinder 4 has the longest axial length from one side A to the other side (not shown) of the radially symmetrical position R ₁ and the other half circumference R ₂ from the other side to one side A. The dimensions are gradually shortened from the shortest dimension to the shortest dimension, and it is shaped like a ratchet gear with two teeth.

A second sleeve 5 of non-magnetic material is externally fitted and fixed to the lower shaft 1c, and a cylinder 6 of magnetic material is externally fitted and fixed to the second sleeve 5. This cylinder 6 is the cylinder 4
The same size, same shape, and inclined shaft end face,
They are positioned on the inclined shaft end side of the cylinder 4 and facing each other with an appropriate distance apart.

On the sides of the positions where the axial end surfaces of the cylinders 3 and 4 and the axial end surfaces of the cylinders 4 and 6 are facing each other, magnetic cylinders 7 and 8 having inner flanges are installed. It is placed an appropriate length away from 6 and straddles them. A temperature compensation coil 9 and a torque detection coil 10 are wound around the inner peripheral grooves of the cylinders 7 and 8, respectively. The output voltages of these coils 9 and 10 are applied to a differential amplifier 11.

In this torque sensor, when an oscillator is connected to the temperature compensation coil 9 and the torque detection coil 10, the cylinder 7 and the cylinders 3 and 4 form a magnetic circuit, and the cylinder 8 and the cylinders 4 and 6 form a magnetic circuit. do. When the upper shaft 1a is rotated in one direction or the other direction, the torsion bar 1b is twisted and the cylinders 4 and 6 rotate relative to each other. Therefore, the opposing gap between the axial end surface of the cylinder 4 and the axial end surface of the cylinder 6 decreases/or increases, and the cylinder 4
The state of magnetic resistance between the cylinder 6 and the cylinder 6 changes. Therefore, a positive/negative voltage corresponding to the state of magnetic resistance is induced in the torque detection coil 10. On the other hand, since the opposing gap between the cylinders 3 and 4 is constant, the voltage induced in the temperature compensation coil 9 is constant. Therefore, by obtaining the difference between the voltage of the torque detection coil 10 and the voltage of the temperature compensation coil 9, the voltage change of both coils 10 and 9 due to temperature change is canceled out, and the amount of relative rotation between the cylinders 4 and 6 is reduced. A voltage with a state of magnetoresistance corresponding to that can be obtained.

Since the amount of relative rotation between these cylinders 4 and 6 is determined by the rotational torque applied to the upper shaft 1a, the torque acting on the torsion bar 1b is detected from the voltage induced in the torque detection coil 10.

[Problem to be solved by the invention]

By the way, when the above-mentioned conventional torque sensor is assembled with the torsion bar 1b being bent during the assembly process, the cylinders 4 and 6 fixed to the upper shaft 1a and the lower shaft 1c are opposed to each other. This results in an initial state in which the gap deviates from the predetermined value. In addition, when the upper shaft 1a is steered and the torsion bar 1b is bent, the torsion bar 1b makes a sliding movement using the joint between the torsion bar 1b and the lower shaft 1c as a fulcrum, and the opposing gap between the cylinders 4 and 6 changes. It turns out. Therefore, there is a problem in that the opposing gap between the cylinders 4 and 6 changes due to factors other than the torque acting on the torsion bar 1b, reducing the torque detection accuracy.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a torque sensor that detects torque with high precision without being affected by the deflection of a torsion bar.

[Means to solve the problem]

The torque sensor according to the present invention is a magnetic material that is inserted into a cylindrical case, interlocks with each of two shafts connected via a torsion bar, and whose magnetic resistance state changes with the relative rotation of the two shafts. A torque sensor that detects torque by detecting the magnetic resistance state of the plurality of cylinders, the torque sensor comprising a plurality of cylinders made of A plurality of bearings are fitted inside and fixed, two tubes made of non-magnetic material are fitted and fixed to the bearings, and each of the plurality of cylinders is individually fitted and fixed on the outside, and the two shafts are fixed to each other. It is characterized by comprising a connecting member disposed between the outer periphery and the inner periphery of the two tubular bodies, and connecting these shafts and the tubular bodies so as to be relatively movable in the axial direction.

[Effect]

When rotational torque is applied to one of the shafts connected to the torsion bar, the torsion bar is twisted in accordance with the torque. One of the tubes made of a non-magnetic material, which is fixedly fitted inside one of the bearings, rotates, and one cylinder made of a magnetic material, which is fixedly fitted and fixed to the outside thereof, rotates.
The opposing gap between the shaft end of the other cylinder made of magnetic material, which is fixed externally to the other tube made of non-magnetic material, which is fixed internally to the other bearing, and the shaft end of one cylinder changes. . The state of magnetic resistance of a plurality of cylinders is detected to detect the torque acting on the torsion bar. When the torsion bar is bent, the shaft and the tube move relative to each other in the axial direction via the connecting member, and there is no change in the facing gap between the shaft end of one cylinder and the shaft end of the other cylinder.

Therefore, the opposing gap between the two cylinders is not affected by the deflection of the torsion bar.

〔Example〕

The present invention will be described in detail below with reference to drawings showing embodiments thereof.

FIG. 1 is a half-cut sectional view showing the structure of a torque sensor according to the present invention. An upper shaft 21a to which a steering wheel (not shown) is attached, and a steering mechanism (not shown)
The lower shaft 21c to which the upper and lower shafts 2 are attached
Pins 21d and 21d driven into 1a and 21c, respectively
are coaxially connected via a torsion bar 21b. Pin insertion holes 21e, 21e are formed on the outer circumferential surfaces of the upper and lower shafts 21a, 21c at positions spaced apart by an appropriate length in the axial direction from their respective tips, and each pin insertion hole 21e, 21e is provided with a connecting member. One end of short barrel pins 22, 22 is inserted.
These pin insertion holes 21e and 21e are located on the upper and lower shafts 21.
A plurality of pins 21a and 21c are formed at suitable distances apart in the circumferential direction of the outer circumferential surface of each of the pins 21a and 21c, and a pin 22 is inserted into each of the pins 22. The upper and lower shafts 21a and 21c are inserted into the inner peripheral surface of the cylindrical case CA, which is fixed to the vehicle body (not shown).
Bearings 23 and 24 are internally fitted and fixed at positions spaced apart from each other in the direction of the substantially equilong axes from opposing positions on the shaft end surfaces of c. On the inner periphery of each of the bearings 23 and 24, tubes 25 and 26 made of a non-magnetic material and having a slightly larger diameter than the outer diameter of the upper shaft 21a are installed, with the end surfaces of the shafts on one side separated by an appropriate length. It is stuck inside. Pipe bodies 25 and 2
6 has an upper shaft 21a and a lower shaft 21c on the inner circumferential surface.
The pipe bodies 25, 26 are placed at a position opposite to the pin 22 inserted into the pipe body, with a width and depth that allows the pin 22 to be inserted into the pipe body 25, 26.
Pin guide grooves 25a and 26a are formed from the tip of the pin guide grooves 25a and 26a, respectively, which are parallel to the axis and have appropriate length dimensions. The other ends of the pins 22, 22 are slidably engaged in the pin guide grooves 25a, 26a. The other end of each pin 22 has a circular arc surface for smooth sliding. As a result, the upper shaft 21a
The rotational force of the lower shaft 21c is transmitted to the tube 25 via the pin 22, and the rotational force of the lower shaft 21c is transmitted to the tube 26 via the pin 22, so that the tubes 25 and 26 are connected to the upper and lower shafts 21a and 21c. It's starting to work together.

As shown in the half-cut side view of FIG. 2, a first cylinder 27 and a second cylinder 28 made of a magnetic material are fitted onto the outer circumferential surface of the tube body 25 and are fixedly spaced apart from each other by an appropriate length in the axial direction. ing. Each shaft end surface of the cylinder 27 is a plane perpendicular to the axis of the upper shaft 21a.

The shaft end surface of the cylinder 28 facing the cylinder 27 is a plane perpendicular to the axial center of the upper shaft 21a, and the shaft end surface on the opposite side has a predetermined inclination angle to the axial center of the upper shaft 21a and is non-perpendicular. Furthermore, the plane is asymmetrical with respect to the axis.

That is, the axial length of the cylinder 28 is such that the axial length of the radially symmetrical side R1 from one side A to the other side (not shown) and the other half circumference R2 from the other side to the one side A is from the longest dimension to the shortest dimension. The dimensions are gradually shortened, and it is shaped like a ratchet gear with two teeth.
A third cylinder 29 made of a magnetic material is externally fitted and fixed to the tube body 26 . This cylinder 29 has the same size and shape as the cylinder 28, and is positioned such that its inclined shaft end face is opposed to the inclined shaft end face of the cylinder 28 with a suitable distance therebetween. The axial end surfaces of the opposing cylinders 28 and 29 are inclined surfaces inclined in the same direction with respect to the axial center. Also,
Inner flanges 30a, 30a are provided on the inner peripheral surface of the case CA between the bearings 23 and 24 disposed.
A magnetic cylindrical body 30 and an inner flange 31 having
A cylindrical body 31 of magnetic material having cylindrical bodies 31a and 31a is fitted and fixed therein. And the cylinder 30 is the cylinder 27 and 28
The cylinder body 31 is placed in a position spanning the cylinders 28 and 2.
9 and are placed at appropriate distances from each other. In the inner circumferential groove of each cylinder 30, 31, a temperature compensation coil 3 with an appropriate number of windings is arranged along the groove.
2. The torque detection coil 33 is wound. The respective outputs of the temperature compensation coil 32 and the torque detection coil 33 are both given to a differential amplifier 34, and the output of the differential amplifier 34 is used as the torque output TS.

Next, the operation of the torque sensor of the present invention will be explained. The magnetic flux generated in the temperature compensation coil 32 and the torque detection coil 33 by the oscillation operation of an oscillator (not shown) interlinks with the cylinders 27, 28 and 28, 29, and induces a voltage in these. Will be using it.

As shown in FIG. 2, if the lower edge (or upper edge) of the cylinder 28 (or 29) is an inclined surface that is displaced upward (or downward) in the clockwise direction (or counterclockwise direction), the steering wheel When rotated clockwise (in the direction of the solid line arrow), the torsion bar 21b
Due to this action, the cylinder 28 rotates relative to the cylinder 29 in the clockwise direction. Then pin 2
The cylinders 27 and 28 rotate together with the tubular body 25 via the tube 25, and the opposing gap between the lower end edge (left end in the drawing) and the upper end edge (right end in the drawing) of the cylinder 29 is shortened, the magnetic resistance is reduced, and the torque detection coil 33 output voltage increases. On the other hand, since the state of magnetic resistance between the cylinders 28 and 27 is constant, the temperature compensation coil 32
The output voltage of the differential amplifier 34 is constant, and the output of the differential amplifier 34 takes a positive value corresponding to the above-mentioned relative rotation amount.

On the other hand, when the steering wheel is rotated counterclockwise (in the direction of the dashed arrow), the opposing gap between the lower edge of the cylinder 28 and the upper edge of the cylinder 29 expands, increasing magnetic resistance.
The output voltage of the torque detection coil 33 becomes smaller.
Then, the output of the differential amplifier 34 becomes a negative value corresponding to the relative rotation amount.

Since the amount of relative rotation is determined by the rotational torque applied to the upper shaft 21a by the steering wheels, the torque can be detected by the output of the differential amplifier 34.

By the way, the cylinders 28 and 29 described above are
Since the torsion bar 21b is fitted and fixed to the outside of the tube bodies 25 and 26 which are fitted and fixed to the tubes 3 and 24 respectively, the torsion bar 21b
Even if the tubes are bent, the pins 22, 22 engaged with the upper and lower shafts 21a, 21c slide along the pin guide grooves 25a, 26a formed in the tubes 25, 26, and the bending force is transferred to the tubes. There is nothing to give on 25th and 26th.
Therefore, even if the torsion bar 21b bends and performs a sliding movement, the opposing gap between the cylinders 28 and 29 does not change at all.

When the upper shaft 21a rotates, the tube body 25 and the cylinder 28 are accurately rotated via the pin 22.

Therefore, according to the present invention, since it is not affected by the deflection of the torsion bar at all, it is possible to provide a torque sensor that always detects only the torque acting on the torsion bar and has high detection accuracy.

In this embodiment, the opposing shaft end surfaces of the cylinders 28 and 29 are both sloped surfaces in the same direction, but the same effect can be obtained even if they are vertical surfaces. In addition, the upper and lower shafts 21a, 21c and the pipe bodies 25, 26
Although pins 22, 22 are interposed between the two pins 22, 22, respectively, it goes without saying that coil springs having relatively high mechanical strength may be used instead of the pins 22, 22.

〔effect〕

As detailed above, according to the present invention, even if the torsion bar interposed between one shaft and the other shaft is bent, the opposing gaps between the plurality of cylinders that occur in response to the torque will not change at all. do not.

Therefore, only the torque acting on the torsion bar can be detected at all times. Therefore, it is possible to provide a torque sensor that always detects torque with high precision.

[Brief explanation of the drawing]

FIG. 1 is a half-cut sectional view of a torque sensor according to the present invention, FIG. 2 is a half-cut side view of its cylinder, and FIG. 3 is a half-cut partial sectional view of a torque sensor that detects torque by a change in the state of magnetic resistance. . 21a... Upper shaft, 21b... Torsion bar, 21c... Lower shaft, 23, 24... Bearing, 2
5, 26... tube body, 27, 28, 29... cylinder,
30, 31... Cylindrical body, 32... Temperature compensation coil,
33... Torque detection coil, 34... Differential amplifier, CA... Case.

Claims (1)

[Claims] 1. A plurality of cylinders made of a magnetic material are inserted through a cylindrical case, interlock with each of two shafts connected via a torsion bar, and whose magnetic resistance state changes with the relative rotation of the two shafts. , a plurality of torque sensors for detecting torque by detecting the magnetic resistance state of the plurality of cylinders, the plurality of torque sensors being concentric with the two axes, spaced apart from each other in the axial direction, and fixedly fitted inside the case; a bearing, two tubes made of a non-magnetic material that are fitted and fixed to the bearings, and each of the plurality of cylinders is individually fitted and fixed to the outside, and outer peripheries of the two shafts and the two tubes. A torque sensor comprising: a connecting member disposed between the inner periphery of the shaft and the tube body to connect the shaft and the tube body so as to be movable relative to each other in the axial direction.