JPH08304193A - Torque sensor - Google Patents

Abstract

PURPOSE: To provide a torque sensor which can be easily manufactured and of which torque detection characteristic itself has a curvature change which is similar to a desired auxiliary steering force characteristic in a power steering device. CONSTITUTION: The torque sensor is provided with magnets 6a and 6b where the same magnetic poles are arranged oppositely with a certain space along the axial direction on the outer-peripheral part of a steering side shaft 1 out of the steering side shaft 1 and a steering machine mechanism side shaft 2 connected to a torsion bar 3, a Hall element 5 provided at the center position between the magnets 6a and 6b and on the center line of the magnets 6a and 6b, and yokes 7a and 7b which are supported by a supporting member consisting of a nonmagnetic material being provided at the axial edge of the steering mechanism side shaft 2 and whose length in the axial direction is nearly equal to that of the magnets 6a and 6b and is provided at positions opposite to the side surfaces of the magnets 6a and 6b while sandwiching a center line for connecting the magnets 6a and 6b and the center of the Hall element 5 and in the vertical direction to the center line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor applied to an electric power steering device of an automobile.

[0002]

2. Description of the Related Art An electric device has been developed as a power steering device for assisting a force for operating steered wheels of an automobile. This is a device that detects the steering torque of the driver, and an electric motor provided in the steering mechanism generates a steering assist force according to the detected torque. It has the feature that it does not consume engine output.

As the steering torque detecting means, a non-contact means having a simple structure is desirable in terms of reliability and cost. As such steering torque detecting means, for example,
It is disclosed in JP-A-61-235270 and the like,
The principle configuration is as shown in FIGS. 6 (a) to 6 (c).

In FIG. 6 (a), a steering side shaft 101 to which steering wheels (not shown) are attached and a steering mechanism side shaft 102 to which a steering mechanism (not shown) is attached are coaxial with each other via a torsion bar 103. And relatively rotatably connected to each other, and these shafts are rotatably supported by a cylindrical case 104 fixed to another component (not shown).

On the outer circumference of the shaft end of the steering mechanism side shaft 102,
The magnet 105 is fixed and the steering shaft 101
A Hall element 106 for detecting the magnetic flux generated by the magnet 105 is fixed to the outer periphery of the shaft end portion of the. The positional relationship between the magnet 105 and the Hall element 106 at this time is shown in FIG.
The combination is as shown in (b) or FIG. 6 (c).

Further, a slip ring 107 is attached to the outer circumference of the case 104 of the steering side shaft 101, and a brush 108 is attached to the inner circumference of the case 104 at a position corresponding to the slip ring 107. Element 10
A detection signal from 6 is amplified by a circuit 109 attached to the outside of the case 104 via a slip ring 107 and a brush 108, and is sent to a control circuit of a motor that generates a steering assist force.

In the torque sensor having such a configuration, when torque is applied from the steering side shaft 101 and the torsion bar 103 is twisted, the magnet 105 and the hall element 106 are provided.
Is relatively displaced, the magnetic flux density of the magnetic flux from the magnet 104 passing through the Hall element 106 changes, and the change of the magnetic flux density corresponding to the change of the applied torque (change of the twist angle) changes. And a torque detection signal is output. The magnet 105 and the Hall element 10
6 shows the torque detection characteristics with respect to the applied torque when the positional relationship with 6 is shown in FIGS. 6 (b) and 6 (c).

Then, the torque detection signal is processed by the control circuit of the electric motor, and the steering assist force corresponding to the steering force of the driver is generated by the electric motor based on the processing information.

By the way, in the power steering apparatus, when the steering force applied to the steering wheel by the driver is small, for example, in the correction steering during straight traveling, the steering assist force is suppressed to stabilize the steering operation feeling. On the contrary, it is necessary to give a feeling of light operation by generating a large steering assist force at the time of stationary steering when the vehicle is stopped or a steering operation at low speed running which requires a large steering force. Therefore, as shown in FIG. 8, the steering assist force characteristic with respect to the steering torque of the driver is suppressed near zero torque, and when the steering torque increases in the positive or negative direction, the steering assist force characteristic rises sharply and the driver operates with a large steering force. It is desirable to have a characteristic that does not require the handle to be operated.

[0010]

However, in the conventional torque sensor for the electric power steering apparatus having the structure shown in FIG. 6, the torsion bar 103 is twisted so that the magnet 105 moves toward the Hall element 106.
Since it is configured to be displaced in the directions of arrows X1 and X2 shown in (b) to FIG. 6 (c), the torque detection characteristic with respect to the input torque is as shown in FIG.
′) Has no curvature change linearly proportional to the input torque, or the output change is large near zero torque as shown in (b ″), and the torque increases as the input torque increases in the positive or negative direction. The slope of the detection characteristic curve becomes saturated (in the case of the configuration of FIG. 6B) or becomes asymmetrical depending on the input direction of the input torque as shown in FIG. 6C (FIG. 6C). In the case of the above configuration), a characteristic curve having a curvature change near zero torque cannot be obtained for a torque input in both directions as shown in FIG.

Therefore, the magnets 105a, 10 shown in FIG.
There is known a method of obtaining the characteristic curve having the curvature change shown in FIG. 8 by making the configurations of 5b and the Hall element 106 as shown in FIG.

In FIG. 9, when manufacturing the torque sensor, the Hall element 106 has a center line C3 of the magnets 105a and 105b.
If the Hall element 106 deviates from the center line C4 of the gap between the magnets 105a and 105b when the Hall element 106 deviates from the above, the torque detection sensitivity varies depending on the difference in the torque application direction. Magnet 105a,
It is necessary to precisely position 105b and the Hall element 106.

However, in the structure shown in FIG. 9, since the two magnets 105a and 105b are fixed to the other terminal of the torsion bar 103, the positions of the magnets 105a and 105b and the Hall element 106 can be manufactured with high precision. It is difficult.

Therefore, since the torque sensor having the configuration shown in FIG. 6B or 6C is practically used, the conventional torque sensor shown in FIG. 8 is used. In order to realize such a desirable steering assist force characteristic, arithmetic processing by a microprocessor or the like is required, which causes a problem that the control circuit becomes complicated and expensive, and it is a problem to solve this problem.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and the torque detection characteristic itself is desired in an electric power steering apparatus without relying on complicated arithmetic processing by a microprocessor or the like. An object of the present invention is to provide a torque sensor suitable for generating an auxiliary steering force characteristic, that is, having a torque detection characteristic having a curvature change similar to that of the auxiliary steering force characteristic.

[0016]

A torque sensor according to the present invention comprises two torque sensors which are coaxially connected to each other via a torsion bar and which can be relatively rotationally displaced by twisting the torsion bar when a rotational torque is applied. In a torque sensor for detecting the rotation torque of a shaft, the same poles of magnetic poles are provided facing each other at a constant interval along the axial direction on the outer peripheral portion of the shaft end of one of the two shafts. Each magnet, a Hall element provided at an intermediate position between the magnets and on the center line of each magnet, and a support member made of a non-magnetic material provided at the shaft end of the other shaft. The length in the axial direction is substantially the same as that of each of the magnets, and the side surface of each of the magnets is sandwiched between the center lines connecting the centers of the magnets and the Hall elements and in the direction perpendicular to the center line. It is characterized in that it has a structure in which each comprise a yoke made of a magnetic material provided at a position facing the respectively.

[0017]

The torque sensor according to the present invention, which has the above-described structure, is coaxially connected through the torsion bar, and when a torque is applied to the torque sensor, the torsion bar is twisted so that the magnetic poles have the same polarity. The gap between one magnet of the magnets provided at one shaft end facing each other and one of the yokes facing the side surface of the one magnet is narrowed, and at the same time, The gap between the other magnet and the other yoke facing the other magnet is opened. Therefore, of the total magnetic flux generated from one of the magnets, the magnetic flux passing through one of the yokes is increased, so the magnetic flux passing through the Hall element is reduced, and among the total magnetic flux generated from the other magnet, Since the magnetic flux passing through the other yoke decreases, the magnetic flux passing through the Hall element will increase, and as a result, the Hall element will detect more magnetic flux generated from the other magnet, and this information will also be detected. The torque will be detected.
At this time, the gap between each magnet and the facing yoke changes due to the application of the rotating torque, so that the torque detection characteristic has a curvature change similar to the auxiliary steering force characteristic.

Further, since each magnet and the Hall element may be fixed to the end of one of the two shafts when assembled, the magnet and the Hall element should be precisely positioned before the assembly with the torsion bar. This facilitates the manufacture, and as a result, facilitates the manufacture of a torque sensor whose detection characteristic has a curvature change similar to that of the auxiliary steering force characteristic.

[0019]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 is a block diagram showing an embodiment of a torque sensor according to the present invention, in which a steering shaft 1 on which steering wheels (not shown) are mounted and a steering mechanism (not shown) are mounted. The mechanism-side shaft 2 is coaxially and relatively rotatably coupled to each other via a torsion bar 3, and these shafts are connected by a cylindrical case 4 fixed to another component (not shown). It is rotatably supported.

A Hall element 5 and magnets 6a and 6b are fixed to the outer periphery of the end of the steering side shaft 1, and the outer periphery of the end of the steering mechanism side shaft 2 and the magnets 6a, 6b.
Yokes 7a and 7b are fixed at positions facing 6b, respectively.

Further, a slip ring 8 is attached to the steering shaft 1.
However, the brush 9 is attached to the case 4, and the hall element 5
The detection signal from is sent to the sensor circuit via the slip ring 8 and the brush 9.

Next, FIG. 2A is a detailed view of the positional relationship between the Hall element 5, the magnets 6a and 6b and the yokes 7a and 7b in FIG.

In FIG. 2A, the magnets 6 having the same shape are used.
a and 6b have a constant gap G between the same poles of their N or S poles.
It is fixed to the steering-side shaft 1 so as to face each other with h therebetween. Further, the Hall element 5 is at the center position of the gap Gh, and its magnetic detection surface Fh is the magnetic pole end surface F of the magnets 6a and 6b.
It is fixed to the steering side shaft 1 in parallel with m and its center is located on a center line C1 connecting the centers of the magnets 6a and 6b.

On the other hand, the yokes 7a and 7b made of a magnetic material have the same shape, and the yoke 7a is located at the center of the side surface of the magnet 7a in the direction sandwiching the center line C1 and perpendicular to the center line C1. The magnets 7b are opposed to each other with a gap G1 and G2 (the gaps G1 and G2 are equal to each other when no torque is applied) at the center of the side surface of the magnet 7b. The yokes 7a and 7b are fixed to the projecting portions 10a and 10b of the support member 10 which is fixed to the steering mechanism side shaft 2 and is made of a non-magnetic material having a U-shape.

As shown in FIG. 2 (b), the distance R1 from the axial center of the torsion bar 3 to the center of the height Mh of the magnets 6a and 6b is such that the torsion bar 3 can be built therein and the torque is reduced. In order to prevent the case 4 for protecting the sensor from becoming too large, it is desirable to set it to 10 to 30 mm, but in this embodiment, R1 was set to 23 mm.

Ferrite and SmC are used for the magnets 6a and 6b.
Although an o magnet or the like can be used, the SmCo magnet is used in this embodiment from the viewpoint of temperature stability of magnetic flux. If the total length Ml of the magnets 6a, 6b is too short, demagnetization is likely to occur, and if it is too long, the torque sensor itself cannot fit within a realistic length.
Although it is desirable to set it to ˜20 mm, in this embodiment, it is 6
mm.

The width Mw of the magnets 6a and 6b is determined by the Hall element 5
It is practical that the diameter is sufficiently larger than the magnetic detection area and smaller than the diameters of the steering-side shaft 1 and the steering mechanism-side shaft 2, and it is preferably 2 to 20 mm, but in this embodiment, it is 4 mm.

Similarly, the heights Mh of the magnets 6a and 6b are the distance R1 (10 to 30 mm) from the magnetic detection area of the Hall element 5 and the axis of the torsion bar 3 to the center of the height Mh of the magnets 6a and 6b. 2-10 mm depending on the balance with
It is desirable that the length be 4 mm in this embodiment.

Further, the gap Gh between the magnets 6a and 6b is 5 to 40 m so that the Hall element 5 can be mounted between them and the magnetic flux density penetrating the Hall element 5 is sufficiently high.
Although it is desirable to be m, in this embodiment, it is 10 mm.

On the other hand, the total length Yl and the height Yh of the yokes 7a and 7b are preferably 80% to 100% of the total length Ml and the height Mh of the magnets 6a and 6b, respectively.
In this embodiment, the total length Yl is 6 mm and the height Yh is 4 mm, and the thickness of the yokes 7a and 7b is preferably 1 mm or more in terms of processing. In this embodiment, it is 2 mm.

Then, the yokes 7a, 7b and the magnets 6a, 6
The distances G1 and G2 from b are equal to each other when the torsion bar 3 is not twisted, and are 10 to 20N.
When a torque having a magnitude of m is applied and one of the gaps G1 and G2 decreases, the gap is set to 0 to 0.5 mm. Usually, a torsion bar used for power steering is often designed so that the twist angle when a torque of 10 to 20 Nm is applied is within 10 degrees at the maximum, and the torsion bar is not limited to the magnets 6a and 6b. When the distance R1 from the torsion bar 3 is 30 mm at the maximum, the torsional displacement of the gaps G1 and G2 is 5 mm or less. Therefore, the gaps G1 and G2 are 5.5 mm.
It is desirable to set the distance to the following, and in this embodiment, the intervals G1 and G are
2 was 2 mm.

FIG. 3 is a circuit diagram showing the principle of the signal amplifying circuit of the Hall element 5, in which a constant voltage Vcc or a constant current Icc is applied between the terminals T1 and T3, and the terminals T2 and T4.
The potential difference generated therebetween is differentially amplified by the differential amplifier 11 to obtain the sensor output signal V.

Next, the operation of the torque sensor in this embodiment will be described.

In the torque sensor having the structure shown in FIG. 1, when torque is applied from the steering shaft 1, the torsion bar 3 is twisted and the yokes 7a and 7b are displaced in the X direction shown in FIG. The gap G1 between the yoke 7a and the magnet 6a increases, and the gap G2 between the yoke 7b and the magnet 6b decreases.

Here, FIG. 4A shows the positional relationship between the magnets 6a, 6b and the yokes 7a, 7b at zero torque, and at this time, the intervals G1 and G2 are equal. The magnetic flux φ generated from the magnets 6a and 6b is
The side surface of 6b passes through the yokes 7a and 7b, and the remaining part passes through the hall element 5. As shown in FIG. 4 (a), at zero torque, the gaps G1 and G2 are equal, so that among the total magnetic flux generated by the magnets 6a and 6b,
Since the ratios of the magnetic fluxes passing through the yokes 7a and 7b are equal, and the ratios of the magnetic fluxes passing through the magnets 6a and 6b are also equal, as a result, the magnetic flux density passing through the Hall element 5 becomes zero.

When torque is applied to the torsion bar 3 in this state, the gap G1 decreases and the gap G2 increases, as shown in FIG. 4 (b).

Therefore, if there is no magnet 6b, the magnetic flux φ passing from the magnet 6a through the yoke 7a decreases as the gap G1 increases, and the magnetic flux density passing through the Hall element 5 increases.

The rate of change of the magnetic flux density in this case is such that the distance G1 between the yoke 7a and the magnet 6a changes, so that the magnetic flux density passing through the yoke 7a rapidly increases as the distance G1 between the yoke 7a and the magnet 6a increases. The magnetic flux density passing through the Hall element 5 rapidly increases.

Further, the magnetic flux passing from the magnet 6b through the yoke 7b is assumed to be the magnet 6a if the magnet 6a is not present.
The magnetic flux φ passing from b to the yoke 7b increases as the gap G2 decreases, and the magnetic flux density passing through the Hall element 5 decreases.

According to the same principle, the rate of change of the magnetic flux density in this case is such that the magnetic flux density generated from the magnet 6b and passing through the Hall element 5 sharply decreases as the distance G2 between the yoke 7b and the magnet 6b decreases. To do.

Based on the above principle, in the case of FIG. 4 (b), the gap G1 increases and the gap G2 decreases, so that the magnetic flux density passing through the Hall element 5 changes from the magnet 6a to the magnet 6b. The component passing in the direction increases, and the rate of change increases rapidly as the intervals G1 and G2 change.

Here, FIG. 5 is a characteristic diagram showing torque detection characteristics of the torque sensor in this embodiment.
As can be seen from the above, according to the above principle, the detection sensitivity is low near zero torque, and the detection sensitivity increases as the applied torque increases.

Therefore, the torque detection characteristic has a curvature change similar to the auxiliary steering force characteristic.

Further, in this embodiment, each magnet 6
Since the a, 6b and the Hall element 5 are fixed to the end of the steering side shaft 1, the positions of the magnets 6a, 6b and the Hall element 5 are precisely adjusted in advance, and then the torsion bar 3 is used.
Since it can be mounted on a substrate and can be easily manufactured, it can be mass-produced and is practical.

[0046]

As described above, according to the torque sensor of the present invention, when the torsion bar is twisted,
The gap between one of the magnets having the same poles of the magnetic poles facing each other and provided at one shaft end and one of the yokes facing the side surface of the one magnet is narrowed, At the same time, the other magnet and the other yoke facing the other magnet are arranged so that the gap between them is increased, so that the torque detection characteristic can have a curvature change similar to that of the auxiliary steering force characteristic. Since each magnet and Hall element can be fixed to the end of one of the two shafts when assembled, it is possible to perform precise positioning of the magnet and Hall element before assembly with the torsion bar. As a result, it is possible to easily manufacture a torque sensor whose torque detection characteristic has a curvature change similar to that of the auxiliary steering force characteristic, and it is complicated by a microprocessor or the like. Without resorting to calculation processing results in Chodai effect of making it possible obtain inexpensive torque sensor is simple.

[Brief description of drawings]

FIG. 1 is a half cut sectional view showing an embodiment of a torque sensor according to the present invention.

2 is an explanatory view showing a positional relationship between a magnet and a Hall element in the torque sensor shown in FIG. 1, and is an explanatory view seen from an arrow A direction in FIG. 1 when torque is not applied (see FIG. 3A) and FIG. 2B are explanatory views (FIG. 2B) viewed from the arrow B direction.

FIG. 3 is a circuit diagram showing a connection relationship between a Hall element used in a torque sensor according to the present invention and a power supply and a differential amplifier.

FIG. 4 is an explanatory diagram (FIG. 4A) showing a magnetic flux distribution in a positional relationship between a magnet, a Hall element and a yoke when torque is not applied to the torque sensor according to the present invention and torque is applied to the torque sensor. It is explanatory drawing (FIG.4 (b)) which shows the magnetic flux distribution in the positional relationship of a magnet, a Hall element, and a yoke at this time.

FIG. 5 is an explanatory diagram showing an example of detection characteristics of the torque sensor according to the present invention.

FIG. 6 is a half cut sectional view showing an example of a conventional torque sensor (FIG. 6A), and an explanatory view showing configurations of a magnet and a Hall element incorporated in the torque sensor (FIG. 6).
It is (a) and FIG.6 (b)).

FIG. 7 is a characteristic diagram showing an example of torque detection characteristics in a conventional torque sensor.

FIG. 8 is an explanatory diagram showing an example of output characteristics of a desired steering assist force with respect to a steering torque in the power steering device.

FIG. 9 is an explanatory diagram showing another example of a conventional torque sensor.

[Explanation of symbols]

 1 Steering side shaft 2 Steering mechanism side shaft 3 Torsion bar 4 Case 5 Hall element 6a, 6b Magnet 7a, 7b Yoke 8 Brush 9 Sensor circuit 10 Supporting member 11 Differential amplifier φ Magnetic flux line

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[Procedure amendment]

[Submission date] September 1, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

FIG. 6 is a half cut sectional view showing an example of a conventional torque sensor (FIG. 6A), and an explanatory view showing configurations of a magnet and a Hall element incorporated in the torque sensor (FIG. 6).
It is (b) and FIG.6 (c)).

Claims (1)

[Claims] 1. A torque sensor, which is coaxially connected via a torsion bar and detects the rotational torque of two shafts which are relatively rotationally displaceable by the torsion of the torsion bar when a rotational torque is applied, 2 above
Each magnet having the same poles of the magnetic poles facing each other at regular intervals along the axial direction on the outer peripheral portion of the shaft end of one of the two shafts, and an intermediate position between the magnets. And the axial length of each of the magnets is substantially the same as that of each of the magnets supported by the Hall element provided on the center line of each magnet and the support member made of a non-magnetic material provided at the shaft end of the other shaft. And each yoke made of a magnetic material provided at a position sandwiching a center line connecting the centers of the respective magnets and Hall elements and facing each of the side surfaces of the respective magnets in a direction perpendicular to the center line. A torque sensor comprising: