JPH0450228B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a torque detection mechanism suitable for an electric power steering device.

(Prior Art) An electric power steering device has a function of reducing the steering force by causing an electric motor attached to the steering device to generate auxiliary torque in conjunction with steering wheel operation. In order to operate the electric motor, it is necessary to detect at least the direction and magnitude of the steering torque, and therefore a torque detection mechanism is required.

Conventional torque detection mechanisms place a torsion bar, which is an elastic member, between the input shaft and the output shaft, and convert the torque between the input and output shafts into a relative angular displacement proportional to the torque. A cylindrical member is fitted, an elongated hole parallel to the axial direction is bored in the cylindrical member, and a support shaft provided integrally with the input shaft is fitted into the elongated hole to move the cylindrical member in the axial direction. A cam mechanism that is freely supported and placed between the output shaft and the cylindrical member converts the relative angular displacement into an axial displacement of the cylindrical member, and detects torque by detecting the axial displacement of the cylindrical member. The auxiliary torque is generated based on the detected value.

(Problems to be Solved by the Invention) However, in an electric power steering device equipped with such a conventional torque detection mechanism, torque detection is performed based on the axial displacement of the cylindrical member, that is, the relative relationship between the input and output shafts, as described above. Since this is done by detecting angular displacement, if a sudden large difference in rotational speed occurs between the input and output shafts, the operation of the electric motor, that is, the generation of auxiliary torque, cannot follow the steering wheel operation, and as a result, the steering wheel operation The steering characteristic (responsiveness) for the steering wheel overshoots the desired value and then oscillates attenuated around the desired value. In such a state, stable steering characteristics cannot be obtained and the steering feeling deteriorates.

Therefore, the present invention was made to eliminate such conventional problems, and its purpose is to suppress the sudden large difference in rotational speed between the input and output shafts, thereby improving stability. It is an object of the present invention to provide a torque detection mechanism for an electric power steering, which can obtain excellent steering characteristics and further improve the steering feeling.

(Means and effects for solving the problem) In order to solve the above problem, the present invention provides an input shaft 1
and an output shaft 2 are connected via an elastic member 8, and a torque detection mechanism of an electric power steering device detects the torque applied between the two shafts 1 and 2 by converting it into a relative rotational displacement between the two shafts, A damper mechanism 7 is configured in parallel with the elastic member 8 by providing a viscous fluid 7a between the input shaft 1 and the output shaft 2 that generates a resistance force in response to the relative rotational speed of the two shafts 1 and 2. Therefore, the resistance force of the damper mechanism 7 can suppress a sudden large rotational speed difference between the shafts 1 and 2, and excessive steering characteristics and vibration can be reduced.

(Embodiment) A preferred embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a mechanical component showing a torque detection mechanism according to the present invention, and in this figure, the cutting line is bent at 90 degrees at the center to form a cross section. FIG. 2 is a diagram showing a connecting portion between the input shaft and the output shaft, and FIG. 3 is a diagram showing the connecting portion, and is a longitudinal cross-sectional view, a left side view of FIG. 2, and a right side view of FIG.

1 is an input shaft, 2 is an output shaft, and these shafts are rotatably supported by bearings 20 and 21 provided in the case 19. The input shaft 1 has a small diameter portion 1a concentrically provided at its left end, and is fitted into a concentric hole drilled in a large diameter portion 2a at the right end of the output shaft 2, and rotates via bearings 3 and 4. It can be installed freely. Seal rings 5, 6 are provided on the outside of the bearings 3, 4.
A viscous fluid 7a such as oil or grease is filled in a space S formed by the seal ring 5, the hole in the large diameter part 2a, the seal ring 6, and the outer periphery of the small diameter part 1a, and the input shaft 1 This forms a damper mechanism 7 that generates a resistance force that is approximately proportional to the relative rotational speed of the output shaft 2, and also lubricates the bearings 3 and 4. A torsion bar 8, which is an elastic member, is provided concentrically between the input shaft 1 and the output shaft 2. One end of the torsion bar 8 is fixed to the input shaft 1 with a pin 23, and the other end is fixed to the output shaft with a pin 9. Shaft 1 and output shaft 2
generates a relative rotational displacement proportional to the torque between. The input shaft 1 is provided with two grooves 1b having a substantially fan-shaped cross section at symmetrical positions, and the grooves 2b, 2b having a substantially fan-shaped cross-section protruding from two symmetrical positions on the left end of the output shaft are provided with an appropriate gap. It is mated. Therefore, the input shaft 1 and the output shaft 2 can only be rotated by a certain angle from a predetermined position, and the groove 1b and the pawl 2b engage with each other to prevent relative rotation beyond that angle. The mechanism is configured.

A hollow iron alloy movable part 10 is provided on the outer periphery of the input shaft 1.
protrusions 10a, 10a each having a generally fan-shaped cross section are integrally provided at both ends of the movable portion 10.
The protrusions 10a, 10a are formed by hollow discs 11 that are continuous with one end of the leaf springs 11, 11, as shown in FIG.
a, 11a, and is press-fitted and fixed into hollow copper alloy cylindrical members 12, 13 as shown in FIG. In this way, one end of the leaf springs 11, 11 is integrally attached to the movable part 10. The other end of the leaf spring 11 shown in FIG. 3 provided at the left end of the movable part 10 is integrally fixed to the input shaft 1 by rivets 14, 14, while the other end of the leaf spring 11 shown in FIG. The other end of the spring 11 is connected to the movable part 10
A hollow fixing member 16 having a coil spring 15 wound around its outer periphery for compressing and biasing through a cylindrical member 12.
is fixed together with the input shaft 1. Therefore, the movable part 10 is movable only in the axial direction by the leaf spring 11 and biased to the left by the coil spring 15. Cylindrical member 13 fixed to the left end of the movable part 10
has a cam surface 13a at least at one end, and a pin 2 is attached to the side surface of the output shaft 2 on the cam surface 13a.
A bearing 17, which is a roller rotatably supported via b, is engaged. The cam surface 13a and the roller 17 constitute a cam mechanism 18. Therefore,
The relative rotational displacement between the input shaft 1 and the output shaft 2 is converted into an axial displacement of the movable part 10 by the cam mechanism 18, the coil spring 15, and the leaf spring 11.

By the way, the input shaft 1 and the output shaft 2 are rotatably supported by bearings 20 and 21 provided in a case 19, and the outer circumference of the movable part 10 is provided with an appropriate gap and is attached to the inner circumferential surface of the case 19. An integrally fixed differential transformer 22 is provided, which converts the axial displacement of the movable part into an electrical signal. The differential transformer 22 has a primary coil 22a provided at its center, and secondary coils 22b, 2 at both ends.
2c, and an alternating current voltage is applied to the primary coil 22a. At this time, the induced voltages of the secondary coils 22b and 22c change differentially depending on the position of the movable part 10, and the axial displacement of the movable part 10 is converted into an electric signal and detected.

With the above configuration, the viscous fluid, which is oil grease, sealed in the space formed by the hole of the large diameter part 2a of the seal rings 5, 6 and the outer periphery of the small diameter part is distributed between the input and output shafts. A damper mechanism is configured that acts as a resistor that is approximately proportional to the rotational speed, and the action of the damper mechanism can suppress sudden and large rotational speed differences between the input and output shafts, thereby preventing excessive steering characteristics and Vibration can be reduced.

In the torque detection mechanism of this embodiment, the movable part 10 does not slide relative to other members but is displaced in the axial direction. Highly accurate torque detection can be performed. and cam mechanism 1
8 promotes the above effect by the action of the roller.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, it is possible to suppress sudden large rotational speed differences between the input and output shafts, and stable steering characteristics can be obtained. It is possible to provide a torque detection mechanism for an electric power steering device that can further improve the feeling.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the mechanical components of the torque detection mechanism according to the present invention, and in this figure, the cross section is formed by bending the cutting line at 90 degrees at the center. Fig. 2 is a diagram showing the connecting part between the input shaft and the output shaft, Fig. 3 is a diagram also showing the connecting part, and Fig. 2 is a longitudinal sectional view;
They are a left end view of , and a right end view of . In the drawing, 1... input shaft, 2... output shaft,
7... Damper mechanism, 7a... Viscous fluid, 8... Torsion bar which is an elastic member, 10... Movable part which is a cylindrical member, 11... Leaf spring, 13a... Cam surface, 17... Roller, 18... ...It is a cam mechanism.

Claims (1)

[Claims] 1. Connect the input shaft and output shaft via an elastic member,
In the torque detection mechanism of the electric power steering device that converts the torque applied between the two shafts into a relative rotational displacement between the two shafts and detects the torque, the elastic member is connected between the input shaft and the output shaft in parallel with the elastic member. A torque detection mechanism for an electric power steering device, characterized in that a damper mechanism is configured by providing a viscous fluid that generates a resistance force in response to the relative rotational speed of both shafts.