JPH05471Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention relates to a rack-and-pinion type electric power steering device, and more specifically, a protective member supported by a gear case is interposed between the rack shaft and the electric motor. The present invention relates to an electric power steering device that prevents a rack shaft from interfering with an electric motor.

(Prior Art) A rack-and-pinion type electric power steering device in which an electric motor generates a steering assist force is proposed in Japanese Patent Laid-Open No. 59-50864, etc.
An electric motor installed coaxially with the rack shaft is connected to the rack shaft via a ball screw mechanism, etc., and the steering assist force generated by the electric motor is transmitted from the rack shaft to the steering wheels along with the manual steering force applied to the steering handle. This reduces the steering burden.

The present applicant also proposed this type of electric power steering device in Japanese Utility Model Application Laid-open No. 63-43875. The electric power steering device proposed by the present applicant has an electric motor and a ball screw mechanism, each of which is configured coaxially with the rack shaft, disposed in the axial direction of the rack shaft, thereby achieving further miniaturization. .

(Problem to be solved by this invention) However, in the rack-and-pinion type steering device according to the prior application, the electric motor is disposed coaxially with the rack shaft at approximately the center of the rack shaft. Therefore, when a bending moment is applied to the rack shaft due to a road reaction force, the rack shaft is bent and deformed, and there is a risk that the rack shaft may interfere with the electric motor, resulting in malfunction. Therefore, it is necessary to take measures such as securing a considerable space between the electric motor and the rack shaft, and it has not been possible to achieve sufficient miniaturization.

This idea was made in view of the problems mentioned above, and is a rack-and-pinion type electric power steering device that can prevent interference between the rack shaft and the electric motor and obtain stable operation without increasing the size. is intended to provide.

(Means for Solving the Problem) This invention supports a rack shaft connected to a steering wheel in a slidable manner in a gear case, and connects rack teeth formed on the rack shaft within the gear case to a steering handle. An electric motor is provided that meshes with the connected pinion and generates a steering assist force coaxially around the rack shaft, and the steering assist force generated by the electric motor is applied to the steering wheel along with the manual steering force applied to the steering wheel. The gist of the rack-and-pinion electric power steering device for transmitting power to a vehicle wheel is that a reinforcing tube supported by the gear case and through which the rack shaft is inserted is interposed between the rack shaft and the electric motor.

(Function) According to the rack-and-pinion type electric power steering device according to the present invention, the rack shaft comes into contact with the auxiliary pipe to restrict bending deformation, and no excessive deformation occurs. Therefore, there is no interference between the electric motor and the rack shaft when a bending moment is applied to the rack shaft, and the electric motor can be provided close to the reinforcing tube, resulting in miniaturization.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a rack-and-pinion type electric power steering device according to an embodiment of the invention, and is a longitudinal sectional view of the whole.

In the figure, 21 is a gear case attached to a vehicle body (not shown), and the gear case 21 is
Cylindrical center case 21a, the center case 2
It consists of side cases 21L and 21R fitted into openings at both ends of the case 1a, respectively, and a pinion case 21b attached to the side case 21R on the right side in the figure, and these center case 21a and side case 2.
Seal members 22, 23, 24 are interposed at the joints of 1L, 21R and pinion case 21b, respectively, to seal the inside. A pinion shaft 25 connected to a steering handle (not shown) is rotatably supported in the gear case 21, and a rack shaft 26 connected to a steering wheel via a steering linkage such as a tie rod is axially slidable. A pinion gear 27 that is freely supported and fixed to a pinion shaft 25 inside the gear case 21 meshes with rack teeth 26a formed on a rack shaft 26, as will be described later.

The pinion shaft 25 includes a first shaft 25a and a second shaft 25
b are connected to each other by a torsion bar 25c so as to be capable of a predetermined relative rotational displacement, and the pinion case 21
b and into the pinion case 21b and side case 21R.
It is rotatably supported via 9 and 30. This pinion shaft 25 has a pinion gear 27 at its lower end.
is formed, and this pinion gear 27 is connected to the easy shaft 2.
It meshes with the rack teeth 26a formed on the back side in the figure of 6.

Around the pinion shaft 25, a pinion case 2
A steering torque sensor 31 is provided inside 1b, and a generator 32 (indicated by the same reference numeral as the steering rotation sensor) functioning as a steering rotation sensor 32 is provided on the outer wall of the pinion case 21b. In the generator 32, a bevel gear 33a fixed to a rotating shaft is connected to a pinion shaft 25.
It meshes with a bevel gear 33b fixedly attached to rotate integrally with the pinion shaft 25, and outputs to the control device 34 a steering rotation signal with a polarity corresponding to the rotation direction of the pinion shaft 25 and a potential corresponding to the rotation speed. . The steering torque sensor 31 connects the pinion shaft 25 to shafts 25a and 25b.
A movable iron core 35 is fitted so as to be able to slide in the axial direction near the joint between the pinion case 21b and a differential transformer 36 that is fixed to the inner wall of the pinion case 21b and detects the axial displacement of the movable iron core 35. ing. The movable iron core 35 is
The shaft 25 of the pinion shaft 25 has a cam groove that converts the relative rotational motion of the shafts 25a and 25b into axial motion.
It is displaced in the axial direction according to the relative rotational displacement between a and 25b, that is, the steering torque. The differential transformer 36 is
It is connected to the control device 34 and outputs a steering torque signal representing the displacement of the movable iron core 35, that is, the acting direction and magnitude of the steering torque. The details of this steering torque sensor 31, etc. were disclosed by the applicant on April 23, 1986.
Since it is described in detail in the specification of Japanese Patent Application No. 61-93950 (see Japanese Patent Application Laid-open No. 62-251274) filed on the date, the following explanation will be omitted.

The rack shaft 26 is formed with the above-mentioned rack teeth 26a and a spiral groove 26b over a movable distance l (see FIG. 2) in the axial direction. Possibly supported. This rack shaft 26 passes through a hollow reinforcing tube 37 that is cantilever-supported by the side case 21R on the right side of the figure, and also passes through a hollow reinforcing tube 37 that is slidably supported on the side case 21L on the left side of the figure. A tube 38 is inserted therethrough. Reinforcement pipe 3
Although not shown in the figure, a window 7 is formed by cutting out a portion where the pinion gear 27 engages with the rack shaft 26a and a portion where the rack guide engages with each other. This reinforcing pipe 3
7, a seal member 78 and a seal member 59 provided on the rack shaft 26 are slidably engaged with the side case 21R, and a seal member 59 provided on the rack shaft 26 is slidably engaged with the side case 21R. It's sealed. Protection tube 38
has a length approximately equal to half of the movable distance l of the rack shaft 26, is disposed so as to be able to protrude and retract from the side case 21L, and has a stopper portion 38a and a stopper portion 38b formed at both ends thereof, respectively. The protective tube 38 has its stopper portion 38a in contact with the end of the side case 21L to determine the retracted position, and the stopper portion 38b in contact with the end of the side case 21L.
The protruding position is determined by contacting the 1L inner diameter reduced portion. A seal member 39 provided on the protection tube 38 and in sliding contact with the rack shaft 26 is interposed between the rack shaft 26 and the protection tube 38, and a side case 39 is provided between the protection tube 38 and the side case 21L. 21
A sealing member 40 that is provided at L and makes sliding contact with the outer peripheral surface of the protective tube 38 is interposed. This rack shaft 2
The sealing member 39 between the protection tube 6 and the protection tube 38 has a greater sliding resistance than the sealing member 40 between the protection tube 38 and the side case 21L. In addition, 41
L and 41R are dust boots at each end of the rack shaft 26.

A center case 2 is provided around the rack shaft 26.
1a, an electric motor 42 is disposed on the outer periphery of the reinforcing tube 37, and a ball screw mechanism 43 is disposed as a power transmission mechanism in the left side case 21L in the figure. Electric motor 4
2 so that power can be transmitted. Electric motor 42
is arranged coaxially within the center case 21a separated by the rack shaft 26 and the reinforcing tube 37, and is rotatably arranged between the field magnet 44 fixed to the inner wall of the center case 21a and the field magnet 44 and the reinforcing tube 37. The rotor 45 is provided with a rotor 45. The rotor 45 is
It has a cylindrical shaft 48 which functions as an output shaft, and this cylindrical shaft 48 is separated from the rack shaft 26 by a reinforcing tube 37 and rotatably supported radially outwardly of the reinforcing tube 37 by bearings 46 and 47. A laminated iron core 49 having a skew groove and a multi-wound armature winding 50 are coaxially and integrally fixed to the outer circumference of the cylindrical shaft 48 . The armature winding 50 is connected to the control device 34 via a commutator 51 fixed to the cylindrical shaft 40 and a brush 53 housed in a holder 52 and in elastic contact with the commutator 51.
It is energized and rotates.

In the ball screw mechanism 43, a nut member 56 rotatably supported by the side case 21L via a pair of bearings 54 and 55 connects to the cylindrical shaft 48 of the electric motor 42.
It is connected so that it can rotate integrally. Nut member 5
6 has a spiral groove 56a formed on its inner circumferential surface, and is screwed into a spiral groove 26b formed on the rack shaft 26 via a large number of balls 57. In this ball screw mechanism 43, a nut member 56 is driven and rotated by an electric motor 42, and the power generated by the electric motor 42 is transmitted to the rack shaft 26.

Next, the operation of this embodiment will be explained.

In this rack-and-pinion type power steering device, an electric motor 42 is energized by a control device 34 based on output signals of a steering torque sensor 31 and a steering rotation sensor 32, and the steering assist force generated by this electric motor 42 constitutes a power transmission mechanism. It is transmitted to the rack shaft 26 via the ball screw mechanism 43. Then, the rack shaft 26 is moved from the neutral position shown in the figure in the left and right axial directions by the steering assist force generated by the electric motor 42 and the manual steering force applied to the steering handle via the rack teeth 26a. Steering the wheels.

At this time, the seal member 59 provided on the rack shaft 26 slides against the inner peripheral surface of the reinforcing tube 37 to seal the space within the gear case 21 in which the ball screw mechanism 43 is disposed. Therefore, even if the dust boot 41R is damaged, dust and the like will not adhere to the ball screw mechanism 43, and high reliability and improved durability can be achieved. The rack shaft 26 is connected to the reinforcing tube 3.
Since the seal member 59 only moves in the axial direction relative to the seal member 7, the seal member 59 only slides in the axial direction and is not acted on by force in other directions, improving durability.

On the other hand, in this electric power steering device, the easy shaft 2
A bending moment acts on the rack shaft 26, causing bending deformation of the rack shaft 26. However, the rack shaft 26
By contacting the reinforcing tube 37, bending deformation is restricted, and the rotor 45 of the electric motor 42, for example, the cylindrical shaft 48, etc., are not affected. Therefore, even if the gap between the rack shaft 26 and the electric motor 42 is reduced, the electric motor 42 will not be damaged, and high reliability can be achieved as well as downsizing.

2 to 6 show a rack-and-pinion type electric power steering device according to another embodiment of the invention, in which FIG. 2 is an overall sectional view and FIG. Cross-sectional view, Figure 4 is the second
Figure 5 is a cross-sectional view taken from the arrow in Figure 2.
A sectional view taken in the direction of arrows, and FIG. 6 is a partially enlarged perspective view. Note that the same parts as those in the embodiment described above are represented by the same reference numerals, and the following explanation will be omitted.

As shown in the figure, the pinion shaft 25 has bearings 64 and 65 in a pinion holder 63 that is rotatably supported by the gear case 21 by bearings 61 and 62.
The section staff can freely insert it through the . This pinion holder 63 has its center of rotation offset from the center of rotation of the pinion shaft 25, and rotates as the pinion shaft 25 swings in response to a steering reaction force. Around this pinion shaft 25, as shown in detail in FIG.
A generator 32 is connected to the pinion shaft 25 via a generator 32 and functions as a steering rotation sensor, and a steering torque sensor 31 that detects steering torque from rotational displacement of the pinion holder 63 is also provided.
These generator 32 and steering torque sensor 31
As shown in FIG.
8 and 69, and this control circuit 67 is connected to a drive circuit 70 disposed below the pinion shaft 25 by a printed wiring 71. The drive circuit 70 is connected to the electric motor 42 and supplies current to the electric motor 42 based on a signal input from the control circuit 67 . These correspond to the control device 34 in FIG.

The steering torque sensor 31 is connected to the pinion holder 63
A movable iron core 35 protruding from the upper surface of the control circuit 6
7, and a differential transformer 36 connected to the terminal 7. As described above, the differential transformer 36 receives an AC pulse signal from the control circuit 67 and outputs a detection signal of the rotational displacement of the pinion holder 63, that is, the steering torque, to the control circuit 67. In FIG. 3, 73 is a guide mechanism for the rack shaft 26, 74 is a neutral position biasing mechanism for the pinion holder 63, 75 is a seal member, and 76 is a cap.

The rack shaft 26 is slidably axially inserted through a reinforcing tube 77 supported approximately at the center of the gear case 21, and an electric motor 42 is provided coaxially with the rack shaft 26 on the outer periphery of the reinforcing tube 77. The reinforcing tube 77 is fitted into the gear case 21 with a seal member 78 interposed between the right end in the figure on the side of the pinion shaft 25 and the outer peripheral surface.
Also, the left end in the figure is the G wall 7 that is integrated with the gear case 21.
9 is clamped between the rack shaft 26 and a sealing member 80 that is in sliding contact with the shaft 26. As described above, the electric motor 42 is coaxially disposed on the outer periphery of the reinforcing tube 77.
A cylindrical shaft 48 of a rotor 45 of this electric motor 42 is connected to a screw shaft 82 of a ball screw mechanism 43 via a gear reduction device 81. The screw shaft 82 is the rack shaft 26
A spiral groove 82a is formed parallel to the rack shaft 26 and rotatably supported by bearings 83 and 84, and extends over a range corresponding to the movable distance of the rack shaft 26. As shown in FIG. 5, a nut member 85 is screwed into a spiral groove 82a of the screw shaft 82 via a number of balls (not shown). The nut member 85 is
It is fixed via a pair of bolts 88 to a rack holder 87 which is fastened to the rack shaft 26 by bolts 86, and is only allowed to move in the axial direction integrally with the rack shaft 26. This ball screw mechanism 43 connects the electric motor 42 and the rack shaft 26 so that power can be transmitted.

Note that 89 is a seal member provided at the left end of the gear case 21 in the figure so as to be able to come into sliding contact with the rack shaft 26, and this seal member 89 seals the space in the gear case 21 in which the ball screw mechanism 43 is disposed. are doing.

Even in the rack-and-pinion type electric power steering device according to this embodiment, bending deformation of the rack shaft 26 due to the bending moment is regulated by the rack shaft 26 coming into contact with the reinforcing tube 77, and the motor 42 is Even if the rack shaft 26 is provided close to the rotor 45 of the electric motor 42, the rack shaft 26 will not interfere with the rotor 45 of the electric motor 42, and the size of the rack shaft 26 can be reduced.

(Effects of the invention) As explained above, according to the rack-and-pinion electric power steering device according to the invention, the bending deformation of the rack shaft due to road reaction force, etc. is regulated by the reinforcing tube. Therefore, the gap between the rack shaft and the electric motor can be reduced and the electric motor can be arranged coaxially with the rack shaft, making it possible to reduce the size and improve the reliability of the operation of the electric motor.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a rack-and-pinion type electric power steering device according to an embodiment of the invention. 2 to 6 show a rack-and-pinion type electric power steering device according to another embodiment of the invention, in which FIG. 2 is an overall vertical sectional view, and FIG. 3 is a sectional view taken in the direction of the arrow - figure,
FIG. 4 is a sectional view taken along the - arrow in FIG. 2, FIG. 5 is a sectional view taken along the - arrow in FIG. 2, and FIG. 6 is a partially enlarged perspective view. 21... Gear case, 25... Pinion shaft, 2
6...Rack shaft, 26a...Rack shaft, 27...
Pinion gear, 37, 77... Reinforcement pipe, 42...
Electric motor, 43... Ball screw mechanism constituting the power transmission mechanism, 45... Rotor.

Claims (1)

[Claims for Utility Model Registration] (1) A pinion in which a rack shaft connected to a steering wheel is slidably supported in a gear case, and rack teeth formed on the rack shaft are connected to a steering handle within the gear case. An electric motor is provided which generates a steering assist force coaxially around the rack shaft, and the steering assist force generated by the electric motor is transmitted from the rack shaft to the steering wheel along with a manual steering force applied to the steering wheel. A rack and pinion type electric power steering device for transmitting power, characterized in that a reinforcing tube supported by the gear case and through which the rack shaft is inserted is interposed between the rack shaft and the electric motor. electric power steering device. (2) A power transmission mechanism is disposed in the gear case in the axial direction of the rack shaft with respect to the electric motor, and the electric motor is connected to the rack shaft through the power transmission mechanism so as to be capable of transmitting power; A sealing member is provided between the reinforcing pipe,
The rack-and-pinion electric power steering device according to claim 1, wherein the space in which the power transmission mechanism is installed is sealed by the seal member.