JP2000225957A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device free of a drop of the sensing accuracy originating from the wear and/or hysteresis. SOLUTION: An electric power steering device is equipped with a magnet 15 fixed to the peripheral surface of an input shaft 4 or output shaft 2 and a Hall element 16 fixed to the peripheral surface of the other member of them and positioned confronting the magnet 15. When the input shaft 4 and output shaft 2 are in relative rotation, a controller controls the output of a motor on the basis of the voltage generated in the Hall element 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus configured to detect a steering torque and apply an assist force based on the detected steering torque.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional electric power steering apparatus. An output shaft 2 is inserted into the casing 1, and the output shaft 2 is rotatably supported. A steering rod 3 having wheels (not shown) linked to both ends is incorporated in the casing 1. The pinion 2 a formed at the tip of the output shaft 2 is engaged with a rack 3 a provided on the steering rod 3.

[0003] An electric motor for applying an assist force is linked to the steering rod 3 at a position not shown. Further, the casing 1 includes the output shaft 2.
The input shaft 4 is coaxially inserted with the input shaft 4, and the input shaft 4 is rotatably supported. The input shaft 4 is linked to a steering wheel (not shown).

A torsion bar 5 is incorporated in a hollow portion of the input shaft 4, one end of the torsion bar 5 is fixed to the input shaft 4 via a pin 6, and the other end is fixed to the output shaft 2. I have. Therefore, relative rotation between the input shaft 4 and the output shaft 2 is allowed by twisting the torsion bar 5.

In such an electric power steering apparatus, when the steering wheel (not shown) is turned, the rotation is transmitted to the input shaft 4, but the output shaft 2 is prevented from rotating by the load on the wheel side. Therefore, the torsion bar 5 is twisted according to the steering torque, and the input shaft 4
And the output shaft 2 are relatively rotated.

The relative rotation amount and direction between the input shaft 4 and the output shaft 2 are detected by a potentiometer 7 as described below. A sleeve member 8 slidable in the axial direction is attached to the outer peripheral surfaces of the input shaft 4 and the output shaft 2. A guide pin 9 projecting from the outer peripheral surface of the input shaft 2 is slidably engaged with a spiral groove 10 formed in the sleeve member 8. A guide pin 11 protruding from the outer peripheral surface of the output shaft 2 is slidably engaged with an axial groove 12 formed in the sleeve member 8. Therefore, when the torsion bar 5 is twisted and the input shaft 4 and the output shaft 2 rotate relatively, the guide pins 9 and 11 and the spiral groove 1 are rotated.
0, the sleeve material 8 slides in the axial direction by the action of the axial groove 12.

The annular groove 1 is formed on the outer peripheral surface of the sleeve member 8.
3 is formed. The potentiometer 7 is attached to the casing 1, and the detection pin 14 of the potentiometer 7 is located in the annular groove 13.

Therefore, when the sleeve member 8 slides in the axial direction as described above, the detection pin 14 is moved, and the potentiometer 7 can detect the sliding amount and the direction of the sleeve member 8. And this sleeve material 8
Is proportional to the relative rotation amount and direction of the input shaft 4 and the output shaft 2. Therefore, if the controller controls the output of an electric motor (not shown) based on the detection result of the potentiometer 7, the steering torque Can be obtained in accordance with the assist force.

[0009]

However, the guide pins 9 and 11 are slid in the spiral groove 10 and the axial groove 12 of the sleeve member 8 and the detection pin is When the sliding is performed, the grooves 10, 12, and 13 and the pins 9, 11, and 14 may be worn over a long period of time, and the detection accuracy may be reduced.

Although not specifically shown in the potentiometer 7, since the wiper slides on the resistance element, the wiper and the resistance element may be worn. In addition, since the wiper slides on the resistance element, noise may be generated due to the sliding resistance.

Further, if the sleeve member 8 is slid on the outer peripheral surfaces of the two shafts 2 and 4 as in the above-described conventional example, a clearance is inevitably formed between the sleeve member 8 and the two shafts 2 and 4. Therefore, the sleeve member 8 rattles, and hysteresis occurs between the actual steering torque and the detection result, and the detection accuracy decreases.
An object of the present invention is to provide an electric power steering device that detects a steering torque using a magnet and a Hall element and does not cause the above-described problem.

[0012]

SUMMARY OF THE INVENTION The present invention provides an input shaft linked to a steering wheel, an output shaft linked to a steering rod for steering wheels, an input shaft and an output shaft arranged coaxially. And an electric motor for applying an assist force. The controller detects the relative rotation amount and direction between the input shaft and the output shaft, and the controller outputs the output of the electric motor based on the detection result. It is assumed that the electric power steering device is configured to control the power steering. According to a first aspect of the present invention, there is provided a magnet fixed to an outer peripheral surface of one of an input shaft and an output shaft, and a Hall element fixed to an outer peripheral surface of the other of the input shaft and the output shaft and facing the magnet. And the controller is configured to control the output of the electric motor based on the voltage generated in the Hall element when the input shaft and the output shaft rotate relative to each other.

According to a second aspect of the present invention, in the first aspect, a conductive wire is buried in a belt-shaped resin material for supplying a current to the Hall element or transmitting a voltage generated in the Hall element to a controller. A characteristic feature is that a flat cable is used, the inner end of the flat cable is fixed to a shaft on which the Hall element is fixed, and the flat cable is wound in a winding shape around the shaft.

According to a third aspect of the present invention, in the first aspect, a conductive wire is buried in a belt-shaped resin material for supplying a current to the Hall element or transmitting a voltage generated in the Hall element to a controller. Using a flat cable, the inner end of the flat cable is fixed to the axis on which the Hall element is fixed, and this flat cable is wound around the axis and elastically opposite to the winding direction. It is characterized by the fact that it is folded back with power applied.

[0015]

1 and 2 show an embodiment of an electric power steering apparatus according to the present invention. In this example,
Instead of using the potentiometer 7 as in the above conventional example, using the magnet 15 and the Hall element 16
The steering torque is detected. And
Since the other basic structure of the electric power steering device is the same as that of the above-described conventional example, the following description focuses on the differences, and the same components as those of the conventional example are denoted by the same reference numerals. However, a detailed description thereof will be omitted.

In the electric power steering apparatus of this embodiment, a worm wheel 17 is provided on the output shaft 2 instead of connecting an electric motor to the steering rod 3 as in the conventional example described above. An electric motor (not shown) is linked. Obtaining the assist force by the electric motor is, of course, the same as in the conventional example.

As shown in FIG. 1, a spacer 18 is fixed to the outer peripheral surface on the rear end side of the output shaft 2, and a magnet 15 is mounted on the spacer 18. The spacer 18 is for magnetically insulating the magnet 15 from the metal output shaft 2. On the other hand, a spacer 19 is fixed to the outer peripheral surface on the distal end side of the input shaft 4, and the Hall element 16 is mounted on the spacer 19. The spacer 19 is for electrically insulating the Hall element 16 from the metal input shaft 4.

When the input shaft 4 and the output shaft 2 are at the neutral position, that is, when the torsion bar 5 is not twisted, the Hall element 16 is made to face the magnet 15 just. Therefore, the Hall element 16 is placed in a magnetic field formed by the magnet 15.

When a current is applied to the Hall element 16 as described above, the magnet 15
An electromotive force is generated in relation to the magnetic field. Then, if the torsion bar 5 is twisted and the input shaft 4 and the output shaft 2 rotate relative to each other, the relative position between the Hall element 16 and the magnet 15 changes. Will generate a voltage. Therefore, by measuring the voltage, the relative rotation amount and direction of both shafts 2 and 4 can be detected. Then, the controller controls the output of an electric motor (not shown) based on the detection result, so that an assist force corresponding to the steering torque can be obtained.

Here, a flat cable 20 as shown in FIG. 2 is used to supply a current to the Hall element 16 from a controller (not shown) or to transmit a voltage generated in the Hall element 16 to the controller. . The flat cable 20 is formed by embedding a plurality of conductive wires 21 arranged substantially in parallel in a belt-shaped resin material 22.

The inner end of the flat cable 20 is
The input shaft 4 is fixed to the outer peripheral surface. Then, as shown in FIG. 1, the conductive wire 21 is exposed from the vicinity of the inner end of the flat cable 20 and connected to the Hall element 16. In this state, the flat cable 20 is
It is loosely wound around the input shaft 4 in a wobbled shape.
Therefore, the flat cable 20 has an elastic force, and the outermost portion of the flat cable is brought into contact with the inner peripheral surface of the casing 1.

Further, the outer end of the flat cable 20 wound in a wobbled shape is fixed to an external controller (not shown), and a conductive wire 21 is connected to the controller. Therefore, the Hall element 16 is connected to a controller (not shown) via the conductive wire 21 in the flat cable 20.

Next, the operation of the electric power steering apparatus of this embodiment will be described. When the steering wheel (not shown) is turned, as described above, the rotation is applied to the input shaft 4.
However, the rotation of the output shaft 2 is hindered by the load on the wheel side. Therefore, the torsion bar 5 is twisted according to the steering torque, and the input shaft 4 and the output shaft 2 rotate relatively.

If the input shaft 4 and the output shaft 2 rotate relatively,
Since the relative position between the Hall element 16 and the magnet 15 changes, a voltage corresponding to the relative rotation amount and direction of the two shafts 2 and 4 is generated in the Hall element 16. The controller (not shown) detects a voltage change of the Hall element 16 via the flat cable 20, controls the output of an electric motor (not shown) based on the detection result, and exerts an assisting force corresponding to the steering torque. Will be.

According to the electric power steering apparatus of the embodiment described above, when the shafts 2 and 4 rotate relative to each other, the relative position of the magnet 15 and the Hall element 16 is changed in a non-contact state. And Hall element 1
6 does not wear out, and the detection accuracy can be maintained. Moreover, since the potentiometer 7 is not used, the wiper and the resistance element inside the potentiometer 7 do not wear out, and no noise is generated due to the sliding resistance. Furthermore, since the sleeve member 8 is not slid on the outer peripheral surfaces of the two shafts 2 and 4, there is no place where rattling occurs, and the occurrence of hysteresis can be suppressed and the detection accuracy can be prevented from lowering.

Further, if the flat cable 20 is wound in a winding shape as in the above embodiment, when the input shaft 4 rotates, a large pulling force acts on the flat cable 20 or the flat cable 20 is twisted. There is no wrapping around the input shaft 4. For example, the Hall element 16 is
When connecting to a controller (not shown) via a linear cord, it is necessary to provide a margin for the cord length so that a large pulling force does not act on the cord even when the input shaft 4 rotates. is there. However, if the code is lengthened, when the input shaft 4 rotates, the code is twisted. In particular, since steering is frequently performed, the cord is twisted many times, and in some cases, the cord may be entangled with the input shaft 4.

On the other hand, if the flat cable 20 wound in the above-mentioned shape is used, when the input shaft 4 rotates, the flat cable 20 is moved in accordance with the direction of rotation.
Further, it is wound, or conversely, the winding is loosened. If the rotation of the input shaft 4 is dealt with by tightening or loosening the winding in this way, a large pulling force acts on the flat cable 20 or the flat cable 20 is twisted. There is no problem of winding.

When the winding of the flat cable 20 becomes tight or loose, the elastic force changes and acts on the input shaft 4. However, the elastic force is almost negligible compared to the steering torque, and the rotation angle range of the input shaft 4 is only a few degrees as a practical matter. Therefore, the elastic force of the wrapped flat cable 20 does not affect the steering.

FIG. 3 shows an example in which the way of winding the flat cable 20 is changed. That is, as described above, the inner end of the flat cable 20 is fixed to the outer peripheral surface of the input shaft 4. And this flat cable 2
The conductive wire 21 is exposed from the vicinity of the inner end of the hole 0 and connected to the Hall element 16. In this state, the flat cable 20 is wound around the input shaft 4. Instead of winding the flat cable 20 in the quill shape as in the above embodiment, after winding once or twice, the direction opposite to the winding direction is used. It is folded back with elasticity. Therefore, the flat cable 22 has an elastic force, and the outermost peripheral portion thereof is brought into contact with the inner peripheral surface of the casing 1. The outer end of the flat cable 20 is fixed to an external controller (not shown), and the conductive wire 21 is connected to the controller.

When the flat cable 20 wound in this manner is used, when the input shaft 4 is rotated, the flat cable 20 is further wound or loosened depending on the rotation direction. I do. If the rotation of the input shaft 4 is controlled by tightening or loosening the winding,
There is no problem that a large pulling force acts on the flat cable 20 or the flat cable 20 is twisted and wrapped around the input shaft 4. In addition, since the folded portion exerts an elastic force, for example, the length of the flat cable 20 can be shortened so as to have the same elastic force as the whole in the wobbled shape described in the above embodiment. it can.

[0031]

According to the first aspect of the present invention, when the input shaft and the output shaft rotate relative to each other, the magnet and the Hall element change their relative positions in a non-contact state, so that the magnet and the Hall element are worn. Without this, the detection accuracy can be maintained. In addition, since the potentiometer is not used, the wiper and the resistance element inside it are worn,
Noise does not occur due to sliding resistance.
Furthermore, since there is no place where rattling occurs, the occurrence of hysteresis can be suppressed and the detection accuracy can be prevented from lowering.

According to the second and third aspects of the present invention, when the input shaft and the output shaft rotate relative to each other, the flat cable is further wound or conversely wound according to the rotation direction of the shaft to which the Hall element is fixed. The winding is loosened. If the winding is tightened or loosened in response to the rotation of the shaft, a large pulling force acts on the flat cable or the flat cable is twisted to fix the Hall element. There is no problem of winding around. In particular, in the third aspect, since the elasticity is exerted at the folded portion, the length of the flat cable can be shortened so as to have the same elasticity as the whole wound in a wobbled shape. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an electric power steering device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a flat cable 20 wound in a wobbled shape.

FIG. 3 is a perspective view showing a flat cable 20 in which a winding method is changed.

FIG. 4 is a sectional view showing a conventional electric power steering apparatus.

[Explanation of symbols]

 2 Output shaft 3 Serpentine rod 4 Input shaft 5 Torsion bar 15 Magnet 16 Hall element 20 Flat cable 21 Conductive wire 22 Belt-shaped resin material

Claims (3)

[Claims] 1. An input shaft connected to a steering wheel, an output shaft connected to a steering rod for turning a wheel, a torsion bar connecting an input shaft and an output shaft arranged coaxially, and an assist. An electric motor for applying a force, the relative power and direction of the input shaft and the output shaft are detected, and the controller is configured to control the output of the electric motor based on the detection result. In the steering device, a magnet fixed to the outer peripheral surface of one of the input shaft and the output shaft, and a Hall element fixed to the other outer peripheral surface of the input shaft or the output shaft and facing the magnet, The controller is configured to control the output of the electric motor based on the voltage generated in the Hall element when the input shaft and the output shaft rotate relative to each other. Electric power steering device. 2. A method for passing a current through a Hall element and transmitting a voltage generated in the Hall element to a controller.
Using a flat cable with a conductive wire embedded in a belt-shaped resin material, fix the inner end of the flat cable to the shaft to which the Hall element is fixed, and wind this flat cable around the shaft. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is wound in a shape. 3. A method for transmitting a current to a Hall element and transmitting a voltage generated in the Hall element to a controller.
Using a flat cable with a conductive wire embedded in a belt-shaped resin material, the inner end of the flat cable was fixed to a shaft to which the Hall element was fixed, and this flat cable was wound around the shaft. 2. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is turned back in a state in which elasticity is given in a direction opposite to the winding direction.