JPH0352607Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention relates to an electric power steering device for automobiles.

(Prior Art) Recently, various electric power steering devices have been proposed, such as U.S. Patent No. 3983953.
No., JP-A-58-133957, JP-A-58-53562
This method is disclosed in Japanese Utility Model Application Publication No. 171670/1983, etc.

Among these, the electric power steering device most related to the present invention is disclosed in Japanese Patent Laid-Open No. 133957/1983.

In this electric power steering device, the steering shaft is divided into two in the axial direction, and an elastic material is interposed between the two to allow twisting between the first and second shafts. The first shaft is linked to the steering wheel and corresponds to the control shaft of the present invention. Further, the second shaft is linked to the steering mechanism and corresponds to the steering shaft of the present invention. The elastic material corresponds to the torsion bar spring of the present invention.

In order to detect the steering force exerted by the steering wheel, the technique disclosed in Japanese Unexamined Patent Publication No. 58-133957 detects the amount of relative rotation between the control shaft and the steered shaft. For this purpose, in this technology, a sleeve (corresponding to the cam ring of the present invention) is attached to the steering shaft so as to be displaceable in the axial direction but not rotatable, and is connected to the control shaft by a spiral cam groove. ) is used. Since this sleeve or cam ring is displaced in the axial direction in proportion to the amount of relative rotation between the two shafts, the steering force is detected by detecting its position.

(Problem to be solved by the invention) According to this method, in order to detect the steering force by directly detecting the position of the sleeve or cam ring,
The sensitivity of the displacement detection sensor must be sufficiently high, and a special sensor, in this case an electromagnetic coil type sensor, must be used.

If a normal potentiometer or the like is used, the detection sensitivity is low and the electric motor cannot be precisely controlled, resulting in problems in operability.

Therefore, in the present invention, the control accuracy of the electric motor is improved while using a normal potentiometer with normal sensitivity.

(Means for solving the problem) The above problem is linked to the steering wheel,
a control shaft that rotates in accordance with the operation of the steering handle; a steering shaft that rotates to steer the direction of the steered wheels in cooperation with a steering mechanism that steers the direction of the steered wheels; a torsion bar spring that is interposed between the control shaft and the steered shaft and torsionally deforms according to the difference in rotational force between the two; an electric motor that is linked to the steered shaft so as to transmit rotation; and the control. It is provided between the shaft and the steering shaft, is attached to one of them so as to be displaceable in the axial direction, but is not rotatable, and is connected to the other through a spiral cam groove. A cam ring that is displaced in the axial direction depending on the direction and amount of relative rotation between the control shaft and the steered shaft, a torque sensor arm that amplifies the amount of axial displacement of the cam ring and transmits it to one end, and the torque sensor. The problem is solved by an electric power steering device having a potentiometer that detects the amount of displacement of the one end of the arm, and a motor controller that inputs a signal from the potentiometer to control the rotational direction and output of the electric motor. .

(Function) According to the electric power steering device having the above structure, the torsion bar spring is torsionally deformed in response to the steering force of the steering wheel, that is, the difference between the rotational force acting on the control shaft and the rotational force acting on the steered shaft. Therefore, the cam ring is displaced in the axial direction in accordance with the twisting direction and amount of this twisting deformation. The amount of displacement in the axial direction is amplified by the torque sensor arm, and the amount of torsion between the control shaft and the steered shaft is detected by the potentiometer in the amplified state.
Therefore, a potentiometer with normal sensitivity can be used, and even if a normal potentiometer is used, the electric motor can be controlled with sufficient precision.

(Description of Embodiments) This invention will be explained below based on FIGS. 1 and 2 showing embodiments. Rack and pinion steering device 1
The upper end of the control shaft 6 is connected to a steering handle 39 via a steering main shaft 42. The control shaft 6 has a cylindrical shape, and a cylindrical shaft portion 2a of the pinion 2 is coaxially inserted into the lower end of the control shaft 6. The inner diameter of the control shaft 6 and the inner diameter of the shaft portion 2a of the pinion 2 are the same size. A round bar-shaped torsion bar spring 7 is inserted into the shaft portion 2a and the control shaft 6, and the upper and lower ends thereof have a large diameter, and a pin 8,
9 are connected to the shaft portion 2a of the pinion 2 and the control shaft 6, respectively. The pinion 2 is rotatably supported in a rack housing 12 by angular bearings 10,11. As is well known, a rack meshes with this pinion 2, and when the pinion 2 rotates, the rack reciprocates and the direction of the steered wheels is steered. In other words, the pinion is connected to the steering mechanism. The angular bearing 10 is preloaded by the preload adjustment nut 13, and after adjusting the preload, the lock nut 1
Fixed by 4. Also control shaft 6
is rotatably supported by the upper housing 17 by a radial ball bearing 15 and a roller bearing 16. Upper housing 17 and rack housing 12 are connected by bolts 32. Above the roller bearing 16 are an oil seal 18 and a dust cover 1 to prevent foreign matter from entering.
9 are arranged. The dust cover 19 is attached to the control shaft 6.

A cam ring 20 having a U-shaped cross section is fitted into the control shaft 6 as a sensor mechanism for input torque so as to be slidable in the axial direction but not rotatable. That is, a long hole 6a is formed in the control shaft 6 in the axial direction, and a rotation stop pin 21 fixed to the cam ring 20 is slidably inserted into the long hole 6a.
Furthermore, on the opposite side of the rotation stop pin 21, the pinion 2
A pin 22 is attached to the shaft portion 2a of the cam ring 20, and the pin 22 is inserted into a diagonal groove (not shown) provided at the bottom of the cam ring 20. As a result, when a relative angular displacement occurs between the control shaft 6 and the shaft portion 2a of the pinion 2 via the torsion bar spring 7 due to the rotational operation of the steering handle 39, the cam ring 20 changes the relative angle in the axial direction of the control shaft 6. It moves in accordance with the direction and amount of displacement.

One end of a torque sensor arm 23 that amplifies the axial movement of the cam ring 20 is inserted into the groove of the cam ring 20, and the arm 23 is rotatably supported by the upper housing 17 with a pin 26. Since the length of the torque sensor arm 23 from the pin 26 to one end is shorter than the length to the other end, the movement at one end is magnified at the other end. In other words, the right end of the torque sensor arm 23 in FIG. 2 is the control shaft 6.
The torsion bar spring 7 is largely displaced in the vertical direction depending on the direction and amount of twist of the torsion bar spring 7 caused by the relative rotation between the pinion 2 and the pinion 2.
One end of a potentiometer 24 is attached to the other end of the torque sensor arm 23 to detect the amount of displacement of the torque sensor arm 23. The potentiometer 24 is fixed to the upper housing 17 by a fine adjustment lock nut 25.

Adjustment nut 2 is attached to Atsupa housing 17.
7 is attached, and a ball bearing 28 is attached to this.
and the drive gear 4 via the needle bearing 29
A shaft portion 4a is rotatably supported. After adjusting the preload of the drive gear 4, the adjuster nut 27 is fixed to the upper housing 17 by a lock nut 30. 31 is a dust cover provided on the upper housing 17 to protect the bearing 28 of the adjuster nut 27.

A gear 4b of the drive gear 4 meshes with a driven gear 5 attached to the shaft portion 2a of the pinion 2. The drive gear 4 is a flexible coupling 33
It is connected to the electric motor 3 via.

The rack housing 12 has a rack tube 34.
is fixed, and a motor bracket 35 is fixed to this rack tube 34. On the other hand, electric motor 3
is attached to a motor stay 36, and the motor stay 36 is attached to a motor bracket 35 with bolts 37 and nuts 38.

Potentiometer 24 is electrically connected to a control circuit 40, which is also electrically connected to battery 41 and electric motor 3. The potentiometer 24 outputs an electric signal corresponding to the rotational direction and steering torque of the steering handle 39 to the control circuit 40, and the control circuit 40 sets the rotational direction and output of the electric motor 3 based on the signal, and controls the electric motor 3. send. Note that a DC servo motor or a pulse motor is suitable as the electric motor 3.

In the above configuration, the steering handle 3
9 is rotated, the torsion bar spring 7 is twisted by the steering torque, and a relative angular displacement occurs between the control shaft 6 and the shaft portion 2a of the pinion 2. The direction and amount of this relative angular displacement are detected by the potentiometer 24 as the direction and amount of axial displacement of the cam ring 20. That is, the rotation direction of the steering handle 39 and the steering torque are detected by the potentiometer 24. These two signals are sent from potentiometer 24 to control circuit 40. The control circuit 40 sends a current having a direction and intensity according to this signal to the motor 3 to rotate the motor 3, and further rotates the pinion 2 via the drive shaft 33, drive gear 4, and driven gear 5. The rotation direction of the pinion 2 is a direction that reduces the steering torque, that is, a direction that reduces the relative angular displacement between the control shaft 6 and the pinion 2. The potentiometer 24 is set to issue a signal when the steering torque is greater than or equal to the set value, so if the steering torque is less than the set value, the electric motor 3
doesn't work.

As described above, the control shaft 6 is linked to the steering handle 39 and rotates as the steering handle 39 is operated. Further, the pinion 2 is linked to a steering mechanism that steers the direction of the steered wheels by a well-known rack-and-pinion connection, and when the pinion 2 rotates, the direction of the steered wheels is steered. That is, the pinion 2 functions as a steering shaft. The torsion bar spring 7 is connected to the control shaft 6 and the steered shaft 2.
It is interposed between the steering wheel and the steering wheel 39, and is used so as to be twisted and deformed according to the difference in rotational force between the two, that is, the operating force of the steering handle 39.

Then, the torque sensor arm 2
The right end of 3 in FIG. 2 is amplified with respect to the potentiometer 24 and is greatly displaced. This amount of displacement is detected by potentiometer 24. The signal from the potentiometer 24 is input to the control circuit 40, and the control circuit 40 controls the direction and amount of current flowing through the electric motor 3 based on this signal, thereby controlling the rotation direction of the electric motor 3 and the current amount. The output is controlled.

(Effect of the invention) According to the electric power steering device of the invention, the amount of relative rotation between the control shaft and the steered shaft is transmitted to one end of the torque sensor arm in a largely amplified state, and the potentiometer detects this large displacement. The amount of relative rotation between the control shaft and the steered shaft is detected from the amount. Therefore, the amount of relative rotation can be detected with high accuracy using a normal potentiometer with normal sensitivity, and the control accuracy of the motor is also improved. In this way, good operability is achieved.

[Brief explanation of the drawing]

FIG. 1 shows a perspective view of an embodiment of this invention.
FIG. 2 shows a longitudinal sectional front view of the main part of FIG. 1. 1... Rack and pinion steering device, 2... Pinion, 3... Electric motor, 6... Control shaft, 7... Torsion bar spring, 20...
Cam ring, 21... Rotation stopper bolt, 22...
Pin, 23... Torque sensor arm, 24... Potentiometer, 39... Steering handle, 40... Control circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A control shaft that is linked to a steering wheel and rotates in response to the operation of the steering handle, and a steering mechanism that steers the direction of the steering wheels,
A steering shaft that changes the direction of the steered wheels by rotating, and a torsion bar spring that is interposed between the control shaft and the steering shaft and that twists and deforms according to the difference in rotational force between them. an electric motor connected to the steered shaft so as to transmit rotation; and an electric motor provided between the control shaft and the steered shaft, and mounted so as to be displaceable in the axial direction and non-rotatable with respect to one of the control shafts. a cam ring which is connected to the other via a spiral cam groove and which is displaced in the axial direction depending on the direction and amount of relative rotation between the control shaft and the steered shaft; a torque sensor arm that amplifies the amount of axial displacement and transmits it to one end; a potentiometer that detects the amount of displacement of the one end of the torque sensor arm; and a signal from the potentiometer is input to determine the rotation direction of the electric motor. An electric power steering device that has a motor controller that controls output.