JP2001004466A - Toque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and inexpensive torque sensor. SOLUTION: A shaft 1 is fixed with a ring magnet 11. Shield members 12, 13 are fixed to the shaft 1 at a specified interval while covering the magnet 11. The shield members 12, 13 are provided with a slit, respectively, and a Hall element 14 detects flux leaking through the slit. A torque applied to the shaft 1 is detected by the detection circuit 15 based on the output from the Hall element 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor, and more particularly to a torque sensor using a device for detecting a change in magnetic flux.

[0002]

2. Description of the Related Art There are applications for measuring torque in various industrial fields. For example, in the field of automobiles, electric power steering systems have been put to practical use in applications such as detecting torque generated due to steering by a driver and detecting torque in the rotational direction of a tire during traveling. Hereinafter, an example of detecting the torque applied to the shaft will be described.

[0003] As a method of detecting torque, for example,
(1) A method of attaching a circuit for detecting torque to a shaft and extracting the output of the circuit, and (2) A method of attaching a magnet to the shaft and detecting a change in magnetic flux generated by the magnet are known. I have.

FIG. 6 is a diagram schematically showing a torque sensor having a configuration in which a circuit for detecting torque is attached to a shaft. In the configuration shown in FIG. 6, when a torque is applied to the shaft, the relative position between the coil 3 provided on the input side of the leaf spring and the coil 4 provided on the output side of the leaf spring changes. The resonance frequency of the resonance circuit also changes. On the other hand, the detection circuit uses a magnetic effect between the coil 1 and the coil 2 to detect a change in the resonance frequency in the resonance circuit. Then, the conversion unit converts the detected frequency into, for example, a voltage and outputs the voltage. Thereby, the torque applied to the shaft is detected.

FIG. 7 is a diagram showing a torque sensor configured to detect a change in magnetic flux. In this configuration, a ring-shaped first magnetic body is mounted at a predetermined position on the shaft, and a cylindrical member is mounted at a predetermined distance from the first magnetic body in the axial direction of the shaft. Further, a second magnetic body is attached to the cylindrical member so as to be disposed close to the outer periphery of the first magnetic body. Then, the surfaces of the first and second magnetic bodies facing each other include:
Each has irregularities. Further, a Hall element is provided on the side of the first and second magnetic bodies.

In the above configuration, when a torque is applied to the shaft, the relative positions of the first and second magnetic bodies change, thereby changing the magnetic flux around the first and second magnetic bodies. This change in magnetic flux is detected by the Hall element. That is, the torque applied to the shaft is detected as the output of the Hall element. The torque sensor having this configuration is disclosed in detail in, for example, Japanese Patent Application Laid-Open No. 5-196520.

[0007]

However, the configuration shown in FIG. 6 has high torque detection accuracy, but has the disadvantage that the configuration is complicated and the cost is high. on the other hand,
The configuration shown in FIG. 7 requires a plurality of magnets (first and second magnetic bodies), and it is necessary to form irregularities on each of the magnets. For this reason, the size of the torque sensor itself becomes large, and further, the manufacture of the magnet is complicated.

An object of the present invention is to solve these problems and to provide a small and inexpensive torque sensor.

[0009]

According to the present invention, there is provided a torque sensor for detecting a torque applied to a shaft, the magnet being attached to the shaft and a magnetic sensor for detecting a magnetic flux generated by the magnet. A first member fixed at a first position on the shaft to shield magnetic flux between the magnet and the magnetic sensor; a first member fixed at a second position on the shaft and the magnet and the magnetic sensor And a second member for shielding magnetic flux between the first member and the second member. Each of the first and second members is formed with one or more slits for passing a magnetic flux generated by the magnet.

[0010] In the above structure, when torque is applied to the shaft, a twist is generated between the first position and the second position of the shaft, whereby the slit formed in the first member is The position relative to the slit formed in the second member changes. When the position relative to these slits changes, the amount of magnetic flux reaching the magnetic sensor from the magnet changes. Therefore, the torque applied to the shaft can be detected by monitoring the magnetic flux using the magnetic sensor.

According to another aspect of the present invention, there is provided a torque sensor having a magnet attached to a shaft, and one or more slits fixed to a first position of the shaft for passing a magnetic flux generated by the magnet. A first member formed, a second member fixed at a second position of the shaft and having one or more slits formed therein for passing a magnetic flux generated by the magnet, A magnetic sensor provided outside the first and second members to detect a magnetic flux generated by the magnet. The operation of this torque sensor is the same as that described above.

As described above, the torque sensor of the present invention does not need to provide a detection circuit on the shaft and does not need to attach a plurality of magnets to the shaft, so that the configuration is simple.

When a torsion bar is formed on the shaft, the first position is defined as one side of the torsion bar, and the second position is defined as the other side of the torsion bar. According to this configuration, the torque can be detected with high sensitivity. Further, a plurality of Hall elements may be used as the magnetic sensor, and the torque applied to the shaft may be detected based on the outputs of the plurality of Hall elements. According to this configuration, the detection accuracy of the torque sensor is improved.

[0014]

FIG. 1 is a diagram showing a configuration of a torque sensor according to an embodiment of the present invention. In the following example,
The case where a torque applied to a shaft connected to a steering wheel is detected will be described.

The shaft 1 transmits an instruction given by using the steering wheel to a mechanism for controlling the direction of the tire. The torsion bar 2 is provided on the shaft 1 by forming a part of the shaft 1 thin. Since the torsion bar 2 is provided, when torque is applied to the shaft 1, the "torsion amount" between the input side and the output side of the torsion bar 2 increases, and the sensitivity of torque detection is high. Become. The provision of the torsion bar for detecting the torque is a known technique.

The magnet 11 is a ring-shaped permanent magnet and is fixed to the shaft 1 as shown in FIG. A constant magnetic flux is always generated in the area near the magnet 11. Note that ring-shaped magnets are generally inexpensive,
Mounting to the shaft 1 is also easy.

Shielding member (first member or second member)
Reference numeral 12 denotes a substantially cylindrical shape, and is attached to the shaft 1 at a predetermined position on the input side of the torsion bar 2.
The shielding member 12 is made of, for example, a material such as iron that hardly allows a magnetic flux to pass. Further, the shielding member 12 is provided with a plurality of slits as shown in FIG.

Shielding member (second member or first member)
Reference numeral 13 denotes a substantially cylindrical shape, which is attached to the shaft 1 at a predetermined position on the output side of the torsion bar 2.
Like the shielding member 12, the shielding member 13 is also made of a material that does not allow magnetic flux to pass easily. Further, the shielding member 12 is also provided with a plurality of slits as shown in FIG.

The shielding member 12 and the shielding member 13 are attached so as to surround the magnet 11. For this reason,
The magnetic flux generated by the magnet 11 is shielded or blocked by the shielding members 12 and 13. However, since a slit is formed in each of the shielding member 12 and the shielding member 13, a part of the magnetic flux generated by the magnet 11 passes through those slits. The number of slits formed in the shielding member 12 and the number of slits formed in the shielding member 13 are preferably the same, but need not necessarily be the same. When the number of slits formed in the shielding member 12 and the number of slits formed in the shielding member 13 are the same, the shielding member 12 and the shielding member 13 are attached to the shielding member 12 in a state where no torque is applied to the shaft 1. The slit formed and the slit formed in the shielding member 13 are attached to the shaft 1 so as to overlap each other.

The Hall element (magnetic sensor) 14 is a device that converts the strength of a magnetic field into an electric signal using the Hall effect, and outputs a voltage corresponding to the magnetic flux density generated by the magnet 11. Specifically, the Hall element 14 detects a magnetic flux that has passed through slits formed in the shielding members 12 and 13. The detection circuit 15 outputs a signal representing the torque applied to the shaft 1 based on the voltage generated by the Hall element 14.

FIGS. 3A and 3B are views for explaining the operation of the torque sensor, and show a section taken along the line AA 'shown in FIG. FIG. 3A shows a state in which no torque is applied to the shaft 1, and FIG.
Represents a state in which torque is applied to.

When no torque is applied to the shaft 1, as shown in FIG. 3A, the slit formed in the shielding member 12 and the slit formed in the shielding member 13 are arranged so as to overlap each other. Is done. Therefore, the amount of magnetic flux that leaks outside through the shielding members 12 and 13 is maximized. This magnetic flux is applied to the Hall element 14.
Is detected by

When a torque is applied to the shaft 1, a “twist” occurs in the shaft 1, and the shield members 12 and 13 fixed at positions separated from each other relatively move about the axis of the shaft 1. It will be in a rotated state. Note that the angle of the relative rotation depends on the magnitude of the torque applied to the shaft.

For this reason, when torque is applied to the shaft 1, as shown in FIG. 3B, the position of the slit formed in the shielding member 12 and the position of the slit formed in the shielding member 13 are mutually shifted. Will not match. As a result, a part of the magnetic flux that has passed through the slit formed in the shielding member 12 is shielded by the shielding member 13, and the amount of the magnetic flux detected by the Hall element 14 increases the torque applied to the shaft 1. It is reduced compared to that in the state where it is not performed.

As described above, the Hall element 14 outputs a voltage corresponding to the magnetic flux density. Therefore, the torque applied to the shaft 1 can be detected based on the output voltage of the Hall element 14.

When the torque applied to the shaft 1 increases, the shielding members 12 and 13
And the relative angle of rotation between them is greater. Further, as the relative rotation angle increases, the rate at which the magnetic flux generated by the magnet 11 is shielded increases. Furthermore, when the ratio of shielding the magnetic flux increases, the output voltage of the Hall element 14 increases (or decreases). Therefore, Hall element 14 generates a voltage corresponding to the torque applied to shaft 1. In particular, if an appropriate Hall element is selected, the Hall element 14 generates a voltage proportional to the torque applied to the shaft 1, as shown in FIG.

FIG. 5 is a diagram showing a configuration of a torque sensor according to another embodiment of the present invention. This torque sensor includes a plurality of Hall elements 21a to 21d, and the detection circuit 22
The torque applied to the shaft is detected based on the outputs of the plurality of Hall elements 21a to 21d. For example, when the characteristics of the Hall elements 21a to 21d are the same and the distances from the shaft to the Hall elements 21a to 21d are the same, the detection circuit 22 determines the output voltages of the Hall elements 21a to 21d. The torque applied to the shaft is detected based on the average value. By introducing this configuration, the detection accuracy of the torque sensor is improved.

In the above-described embodiment, a slit is formed in the shielding member as a mechanism for adjusting the amount of magnetic flux passing or shielding in accordance with the torque applied to the shaft. It is not limited to the configuration.
That is, the present invention may have another structure as long as it is a mechanism for adjusting the amount of magnetic flux passing or shielding in accordance with the torque applied to the shaft. For example, a plurality of holes may be formed in the shielding member instead of the slit.

In the above embodiment, the Hall element is used to detect the strength of the magnetic field. However, the present invention is not limited to this, and an electric signal is output according to the strength of the magnetic field. Any sensor that can be used in the torque sensor of the present invention.

The torque sensor having the above structure is useful, for example, in an application for detecting torque generated due to driver's steering in an electric power steering system, but is applicable to any application for detecting torque. It is.

[0031]

According to the present invention, since the structure of the torque sensor is simplified, it is expected that the size and the cost are reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a torque sensor according to an embodiment of the present invention.

2A is a perspective view of a magnet, and FIG. 2B is a perspective view of a shielding member.

3A and 3B are diagrams illustrating the operation of the torque sensor according to the present embodiment, wherein FIG. 3A illustrates a state in which no torque is applied to the shaft, and FIG. 3B illustrates a state in which torque is applied to the shaft.

FIG. 4 is a diagram showing a relationship between a torque applied to a shaft and an output of a Hall element.

FIG. 5 is a diagram illustrating a configuration of a torque sensor according to another embodiment of the present invention.

FIG. 6 is a diagram schematically showing an existing torque sensor having a configuration in which a circuit for detecting torque is attached to a shaft.

FIG. 7 is a diagram showing an existing torque sensor configured to detect a change in magnetic flux.

[Description of Signs] 1 Shaft 2 Torsion bar 11 Magnet 12, 13 Shielding member 14 Hall element 15 Detection circuit

Claims (5)

[Claims] 1. A torque sensor for detecting a torque applied to a shaft, comprising: a magnet attached to the shaft; a magnetic sensor for detecting a magnetic flux generated by the magnet; A first member that is fixed and shields magnetic flux between the magnet and the magnetic sensor; and a second member that is fixed at a second position of the shaft and shields magnetic flux between the magnet and the magnetic sensor. A torque sensor having at least one slit formed in each of the first and second members to allow a magnetic flux generated by the magnet to pass therethrough. 2. A torque sensor for detecting a torque applied to a shaft, the magnet being attached to the shaft, and fixed to a first position of the shaft, for passing a magnetic flux generated by the magnet. A first member having one or more slits formed therein, and a second member fixed to a second position of the shaft and having one or more slits formed for passing magnetic flux generated by the magnet. And a magnetic sensor provided outside the first and second members as viewed from the magnet and detecting a magnetic flux generated by the magnet. 3. The torsion bar is formed on the shaft, the first position is on one side of the torsion bar, and the second position is on the other side of the torsion bar. 3. The torque sensor according to 1 or 2. 4. The torque according to claim 1, wherein the magnetic sensor includes a plurality of Hall elements, and further comprising a detection circuit for detecting a torque applied to the shaft based on outputs of the plurality of Hall elements. Sensor. 5. A torque sensor for detecting a torque applied to an object having a rotation axis, the magnet being attached to the object, and a magnetic flux generated by the magnet in accordance with a twist amount of the object. A torque sensor, comprising: a magnetic flux adjusting unit for adjusting a passing amount of the magnetic flux; and a detecting unit for detecting a magnetic flux passing through the magnetic flux adjusting unit.