JPS63292029A - Torque sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor, which is characterized by excellent productivity and excellent durability and is not subject to the effect of temperature, by providing a torsion bar in an input shaft, and detecting the change in electromagnetic couplings accompanied by the relative rotation of magnetic cylinders, which are provided on both sides. CONSTITUTION:A torsion bar 1b is provided in the middle of an input shaft 1. Magnetic cylinders 11 and 12 are fixed to one side of the bar 1b. A magnetic cylinder 13 is fixed to the other side. Annular coils 21-23, which are electromagnetically formed with said cylinders, respectively, are fixed at the outer surface sides of the cylinders. The cylinders 12 and 13 have asymmetric shapes with respect to the axial center of the shaft 1. When, rotary torque is applied to an upper shaft part 1a of the shaft 1, the bar 1b is twisted in correspondence with the torque. The cylinder 12 is relatively rotated with respect to the cylinder 13. Then, the electromagnetic coupling with the cylinders are changed in correspondence with the amount of rotation. Since the electromagnetic coupling states of the cylinders 11 and 12 and the coils 21 and 22 are not changed, the applied torque can be detected based on the difference in signals obtained from the coils 21 and 23. The effects of temperature changes are offset since the difference between the coils 21 and 23 is obtained.

Description

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

[Prior art]

2. Description of the Related Art Electric power steering devices are being developed to assist the operating force applied to the steering wheels of automobiles. This is configured to detect 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, a strain gauge is fixed to the input shaft connected to the steering wheel, and detection is performed by measuring the detected displacement of the input shaft, or a torsion bar is inserted in the middle of the input shaft, and this torsion is detected. Devices that detect displacement using microswitches placed around the input shaft are known, but the former is easily affected by temperature and has problems with accuracy, while the latter uses a microswitch placed around the input shaft. It takes up a lot of space and is impractical.

[Problem that the invention seeks to solve]

Unexamined Japanese Patent Publication No. 56-9 as a solution to these problems
As described in No. 4232, a device that electromagnetically detects the rotation of the input shaft is known, but the parts made of conductive material used therein require high-precision notch machining, which is difficult to produce due to production technology.
In addition, there are economical disadvantages, and there is also the problem that it is difficult to assemble a coil disposed in or around this part due to the influence of temperature.

The present invention has been made to solve such problems, and includes providing a torsion bar in the input shaft and detecting changes in electromagnetic coupling due to relative rotation of magnetic cylinders provided on both sides of the torsion bar. An object of the present invention is to provide a torque sensor which has excellent productivity, is not affected by temperature i5W, and has excellent durability.

[Means for Solving the Problems] The torque sensor according to the present invention includes a rotatable shaft body in which a torsion bar is interposed in the middle, and a first torsion bar on one side of the torsion bar. A second magnetic cylinder is fixed to the other side, and a third magnetic cylinder is fixed to the other side in this order, and the first magnetic cylinder, the second magnetic cylinder, and the third magnetic cylinder are mainly attached to the outer peripheral side of these magnetic cylinders. The first magnetic cylinder is electromagnetically coupled to each of the third magnetic cylinders. Second. A third annular coil is fixedly installed, and a portion of the second or third magnetic cylinder that is involved in electromagnetic coupling with the second and/or third annular coil is relative to the axis of the shaft body. having an asymmetrical shape, the first . It is characterized in that the difference in electromagnetic coupling between the third annular coils is detected as information on the torque applied to one side or the other side of the torsion bar.

[Effect]

When rotational torque is applied to one side of the shaft, the torsion bar is twisted in accordance with the torque, and the second magnetic cylinder rotates relative to the third magnetic cylinder. Since the second or third magnetic cylinder is asymmetrical with respect to the axis of the shaft body, the second or third magnetic cylinder is asymmetrical with respect to the axis of the shaft body. The electromagnetic coupling with the third annular coil changes depending on the amount of rotation. 1st. A second magnetic cylinder and a first magnetic cylinder. Since the state of electromagnetic coupling with the second annular coil remains unchanged, the state of electromagnetic coupling with the second annular coil remains unchanged. The applied torque can be detected by the difference between the signals obtained from the third annular coil. Effects due to temperature changes are canceled out by determining the difference between the first and third annular coils.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a half-cut sectional view showing the structure of a torque sensor according to the present invention, and FIG. 2 is a perspective view of its inner member. In the figure, l is an input shaft, to which a steering wheel is attached on the right side of the figure, and connected to a binion (both not shown) that meshes with a rack connected to the steering wheel on the left side. The input shaft 1 has an upper shaft part 1a on the steering wheel side and a lower shaft part 1c on the binion side, which are coaxially connected via a torsion bar 1b, and the upper shaft part 1a is fixed to the vehicle body. It is rotatably supported by a cylindrical case 2 via a bearing 3.

The outer diameter of the lower end (left side in the drawing) of the upper shaft portion 1a is the lower shaft portion 1c.
Although the diameter is small for insertion into the hole at the upper end (on the right side of the drawing), a sleeve 4a made of a non-magnetic material is fitted and fixed to the lower end of the large diameter part of the upper shaft part 1a, and the sleeve 4a is fixed to the outer periphery of the sleeve 4a. The first part is made of a magnetic material. A second cylinder 11° 12 is externally fitted and fixed concentrically with the input shaft.

The upper and lower first cylinders 11 have upper and lower edges on a plane perpendicular to the axis of the input shaft 1, and have the same length at all positions in the circumferential direction.

The upper end edge of the lower second cylinder 12 is connected to the input shaft 1 like the first cylinder.
However, the lower edge is not perpendicular to the axis and has an asymmetrical shape with respect to the axis. That is, it has a shape that draws one spiral from a part in the circumferential direction.

A second sleeve 4b made of a non-magnetic material is fitted and fixed to the upper end of the lower shaft portion 1c, and a third cylinder 13 made of a magnetic material is fitted and fixed to the outside of the second sleeve 4b concentrically with the input shaft 1. . Cylinder 1
3 has the same shape as the cylinder 12 with the top and bottom opposite to each other, and the cylinder 12.
As shown in Fig. 1.2, the torsion bar 13 is fitted into the sleeves 4a and 4b with its position determined in the circumferential direction so that both opposing edges are parallel when no rotational force is applied to the torsion bar 1b. . A bobbin 5 having three circumferential grooves formed on its outer periphery is fitted and fixed in the case 2, and the center position of each groove in the axial direction is approximately the same as the axial center of each cylinder 11, 12, 13. The coils 21, 22, and 23 in a cylindrical shape are wound and stored therein. As a result, each coil 21.22.23 is mainly cylindrical 11.12.
．． It is electromagnetically coupled with each of 13. Coil 21.22.
The number of turns of 23 may be set as appropriate, but the number of turns of 1. third coil 2
It is convenient to set 1.23 as the same number of turns.

FIG. 3 is a block diagram schematically showing the electrical circuit of the sensor of the present invention. The second coil 22 is connected to the oscillator 6,
1st. The third coils 21 and 23 apply respective induced voltages to the - and ten terminals of the differential amplifier circuit. However, the output of the third coil 23 is sent to the differential amplifier circuit 7 via the potentiometer 8.
is giving to The output of the differential amplifier circuit 7 is used as the output of the sensor of the present invention.

Next, the operation of the sensor of the present invention will be explained. The magnetic flux generated in the coil 22 by driving the oscillator 6 is the magnetic flux generated in the coil 21.2.
3, and generates an induced voltage across them.

Even if the number of turns of the coils 21 and 23 are made equal, the distances between the coils 22 and 21 and 23 are made equal, and the volumes of the cylinders 11 and 13 are made to be approximately the same, it is difficult to make the outputs of the coils 21 and 23 equal. However, the output of the differential amplifier circuit 7 is adjusted to 0 by adjusting the potentiometer 8 when the steering wheel is not rotated, that is, when no rotational force is applied to the torsion bar 1b.

The sensor of the present invention is used under such conditions.

As shown in Figures 1 and 2, if the upper edge (or lower edge) of the cylinder 13 (or 12) is spirally deviated upward in the clockwise direction, the steering wheel is rotated clockwise (solid line). Then, cylinder 12 becomes cylinder 1 due to the action of torsion bar 1b.
rotated clockwise relative to 3, and its lower edge and
The distance from the upper edge of the cylinder 13 becomes smaller, and as a result, the electromagnetic coupling between the cylinders 12 and 13, and therefore the electromagnetic coupling between the coils 22 and 23 becomes larger, and the output voltage of the coil 23 becomes higher. On the other hand, since the electromagnetic coupling between the coils 21 and 22 remains unchanged, the output of the coil 21 is constant, and therefore the output of the differential amplifier circuit 7 takes a positive value commensurate with the above-mentioned relative rotation difference.

On the other hand, when the steering wheel is rotated counterclockwise (dashed line), the cylinder 1
The distance between the lower edge of cylinder 13 and the upper edge of cylinder 13 increases,
Contrary to what was described above, the output of the differential amplifier circuit 7 takes a negative value commensurate with the amount of relative rotation.

Since the amount of relative rotation is determined by the rotational torque applied to the input shaft 1 to the steered wheels, it follows that the torque can be measured using the output of the differential amplifier circuit 7.

Even if the temperature of the coils 21, 22, and 23 changes, as long as the coils 21, 22, and 23 are at the same temperature, the effect on the output change is the same, so temperature compensation can be performed by finding the difference between the outputs of the two. I can do it.

Note that the shape of the opposing edges of the magnetic cylinders 12 and 13 is not limited to the above-mentioned embodiments, but as long as the electromagnetic coupling with the second and/or third coil changes with the relative rotation thereof, In other words, it is sufficient if it is not centrally symmetrical with respect to the axis of the input shaft 1. The coil 23 is rotated by the relative rotation between the two.
This is because it is sufficient if the output voltage of the output voltage changes. For the same reason, it is not necessary for both 100 yen 1 m 12.13 to have such a shape, and either one is sufficient.

Furthermore, in order to obtain this function, it is possible to achieve this not only by making the shape of the opposing edge asymmetrical about the axis, but also by the shape of other parts.

Furthermore, in the above embodiment, positive and negative outputs were obtained depending on the rotation direction, but as shown in FIG.
2. The opposing shaft edge of 13 is set at θ (≠90
It may be configured so that
When rotating counterclockwise, the distance between the hundred cylinders 12 and 13 changes equally, so an output that depends only on the amount of rotation is obtained, regardless of the direction of rotation.

It goes without saying that the torque sensor of the present invention can be used not only in automatic electric power steering link devices but also in a wide variety of general applications, and can also be used to measure the amount of rotation itself.

〔effect〕

Since the sensor of the present invention as described above is essentially a non-contact type sensor, it has excellent durability.

Further, since the magnetic cylinder only has one end formed into a desired shape (a simple slope in the embodiment), it is easy to process and does not require high processing accuracy. Furthermore, the assembly of the magnetic cylinder and the coil is simply a matter of fitting, and there is no difficulty in assembling the magnetic cylinder and the coil. Circumferential alignment of the third magnetic cylinder is necessary, but adjustment in the coil output circuit (
In the embodiment, this can be done using a potentiometer or the like, so strict positioning is not required.

Furthermore, since the first magnetic cylinder and the first annular coil are provided, temperature compensation is performed, and there is no shadow 1 caused by this.

Furthermore, since the annular coil is attached to the case side, there is little temperature rise due to temperature rise of the input shaft. Furthermore, since each member is concentrically stacked and arranged, the present invention has excellent effects such as requiring only a small space.

[Brief explanation of drawings]

Fig. 1 is a half-cut sectional view showing the structure of the sensor of the present invention, Fig. 2 is a perspective view showing its internal structure, Fig. 3 is a block diagram schematically showing the electric circuit of the sensor of the invention, and Fig. 4 is a FIG. 7 is a perspective view showing the internal structure of another embodiment.

Claims (1)

[Claims] 1. A rotatable shaft having a torsion bar interposed in the middle, with first and second magnetic cylinders on one side of the torsion bar and a third magnetic cylinder on the other side. The first, second and third magnetic cylinders are fixed to each other in order and are electromagnetically coupled to the outer peripheral side of these magnetic cylinders.
Second and third annular coils are fixedly installed, and a portion of the second or third magnetic cylinder that is involved in electromagnetic coupling with the second and/or third annular coil is located on the shaft body. It has an asymmetrical shape with respect to the axis, and the difference in electromagnetic coupling between the first and third annular coils with respect to the second annular coil is to be detected as information on the torque applied to one side or the other side of the torsion bar. A torque sensor characterized by: 2. The torque sensor according to claim 1, wherein opposing portions of the second, second, and third magnetic cylinders have parallel lines that are not perpendicular to the axis of the shaft body.