JPH0277359A - Power steering device - Google Patents

Abstract

PURPOSE:To improve operability by providing a rack-pinion mechanism formed by engaging a rack portion disposed on an actuator with a pinion portion disposed on a steering shaft. CONSTITUTION:An actuator 30 for power shift provided separately from a steering mechanism and a steering shaft 20 are connected by a rack-pinion mechanism formed by engaging a rack portion 82 provided on the actuator 30 with a pinion portion 77 provided on the steering shaft 20. Accordingly, the actuator 30 is moved along the direction of the center line by the rectilinear motion of a rack portion 82 engaged with the pinion portion 77 of the steering shaft 20 rotated by steering. Accordingly, the vibration change of the center line of the actuator is not caused so that the power assisting force can be used effectively and the operability can be further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power steering device, and particularly to a connection structure between a power assist actuator provided separately from a steering mechanism and a steering shaft.

[Prior Art] In Japanese Patent Application No. 6:1-42468, the present applicant proposed a power steering device for a vehicle that includes a power assist actuator that is connected to a steering shaft and is provided separately from a steering mechanism.

[Problems to be Solved by the Invention] However, in the past, the connection between the actuator and the steering shaft was configured by a link mechanism using an arm, and the center line of the actuator oscillated due to the oscillation locus of the arm around the steering shaft. Therefore, the power assist force generated by the actuator in the center line direction becomes a component force in the tangential direction of the swing locus of the arm. Therefore, as the steering angle increases, the power assist force decreases, making it impossible to use the power assist force effectively, and conversely, the actuator is designed to generate extra power assist force to compensate for the decrease. There is a need.

Therefore, an object of the present invention is to prevent swinging changes in the center line of the actuator and effectively utilize the power assist force by devising a connection structure between the power assist actuator, which is installed separately from the steering mechanism, and the steering shaft. An object of the present invention is to provide a power steering device with improved operability.

[Means for Solving the Problems] In order to achieve the above problems, the present invention provides a power assist actuator 30 that interlocks with the steering shaft 20.
In a vehicle that is provided separately from the steering mechanism,
A rack portion 82 provided on the actuator 30 connects the actuator 30 and the steering shaft 20.
The present invention is characterized in that it is constituted by a rack and pinion mechanism in which the and pinion portion 77 provided on the steering shaft 20 are meshed with each other.

[Function] The power assist actuator 30 and the steering shaft 20, which are separately provided from the steering mechanism, are a rack and pinion mechanism in which the rack portion 82 provided on the actuator 30 and the onion portion 77 provided on the steering shaft 20 are engaged with each other. Since they are connected, the actuator 30 is moved along the centerline direction by the linear movement of the rack part 82 that meshes with the pinion part 77 of the steering link shaft 20 which is rotated by steering. Therefore, since there is no oscillating change in the center line of the actuator, the power assist force can be used effectively, and the operability is further improved.

[Example] Examples will be described below based on the accompanying drawings.

In FIG. 1 showing the external appearance of a straddle-type four-wheeled vehicle to which the present invention is applied, the left and right front wheels 2 and rear wheels 3 are shown in FIG. Engine power is transmitted to front wheels 2 and rear wheels 3, 4 is a front fender, 5 is a seat, and 6 is a rear fender. 4. Operate the bar handle 7 located above. The bar handle 7 is fixed to the upper end of the steering shaft 20 as shown in the figure, a power assist actuator 30 is connected to the lower part of the steering shaft 20, a steering arm 29 is fixed to the lower end of the steering shut 20, and a knuckle arm that supports the front wheel 2. A tie rod 9 is installed between each of the 8 spaces. In this straddle-type four-wheel vehicle equipped with the bar handle 7, the steering arm 29 is used to transmit power from the steering shaft 20 to the tie rod 9, and the larger the diameter tire or the wider the tire, the greater the steering force required. The embodiment is equipped with a hydraulic power steering device.

As shown in FIGS. 3 and 4, the front part of the vehicle body frame 10 is composed of a main pipe 11, an under pipe 12°, a front pipe 13, a front cushion pipe 14, and a steering under hold pipe 15. Power assist actuator 3
0 is placed. The steering shaft 20 has an upper part supported by a holder 18 at the front end of the main pipe ti, a lower part supported by a bracket 19 installed between the steering under-hold pipes 15, and an actuator 30.
is pivotally supported via a vertical shaft 17 on a right-hand pipe end 16 extending from a steering under-haul pipe 15 at the rear.

The power steering device includes a control valve section V, a power assist cylinder section S, an oil reservoir tank T, an oil pump P, etc. built into the actuator 30.

The reservoir tank T is fixed between the upper parts of the front pipes 13, and the oil pump P is pumped into the cylinders of the engine 1.
The camshaft 1b is of a trochoid type that is fixedly attached to the camshaft 1b and driven integrally with the camshaft 1b or via a joint (not shown). The oil pump P and the reservoir tank T are connected by a suction hose, the oil pump P and the actuator 30 are connected by a foot hose H2, and the actuator 30 and the reservoir tank T are connected by a return hose H3.

By the way, as shown in FIG. 5, the steering shaft 20 consists of an outer shaft 21, an inner shaft 22 which is a torsion bar, and a shaft end 25, both of which are made of pipes.
2 is connected at its upper end to a steering bridge 23 on which the bar handle 7 is fixedly secured by tightening a pipe connector 24. Then, the upper end of the shaft end 25 is inserted into the lower end of the inner shaft 22 and fixed by the welding joint 26, and the lower inner circumference of the outer shaft 21 and the upper outer circumference of the shaft end 25 are arranged at a predetermined angle on both sides in the rotational direction of each other as shown in FIG. They are connected by a spline fitting portion 27 provided with gaps C, C. A bearing 28 is interposed between the upper and lower portions of the spline fitting portion 27, and a steering arm 29 is fixed to the lower end of the shaft end 25.

The power assist actuator 30 is configured as shown in an enlarged manner in FIGS. 7 and subsequent figures. That is, the actuator 30 connects the valve body 31 to the cylinder body 41.
The valve hole 32 provided in the valve body 31 and opened at the front and the cylinder 42 provided in the cylinder body 41 and opened at the rear are vertically parallel to each other.

A spool rod 34 is pivotally connected to the forward protruding part of a spool valve 33 installed in the valve hole 32 through a ball joint 35, and the front part of the rod 44 of a piston 43 installed in the cylinder 42 via a seal is It faces into the rod hole 45 in the front part of the cylinder body 41 that protrudes forward. A boot 36 is provided between the valve body 31 and the spool rod 34, and a joint 38.39 is provided on the upper surface of the valve body 31 to connect the hose 82.113.
or has been established. The rear part of the piston rod 44 is sealed to the cylinder 42 by a rod guide 46, etc., and the rod end 47 provided at the rear protrusion is connected to a rubber bushing 48 with a collar.
A boot 49 is provided between the cylinder body 41 and the rod end 47.

Also, as shown in Fig. 9, the outer part of the steering shaft 20
Stay vibe 7 fixed by welding to the outer periphery of the lower part of the shaft 21
A spool lever 72 is bolted to the spool lever 1, and the spool lever 72 projects to the right and is pivotally connected to the spool rod 34 via a ball joint 73 at its right end. In the embodiment and example, when the vehicle is traveling straight, the ball joint 73 coincides with the center line of the steering shaft 20 when viewed from the side.

Furthermore, the shaft end 2 at the bottom of the steering shaft 20
A center pipe 75 is fixed to the outer periphery of the intermediate portion 5 through a lower serration fitting portion 76, and a serration portion 77 is formed on the outer periphery of the upper end of the center pipe 75. A sliding bush 78 is interposed between the outer circumference of the lower end of the outer shaft 21 where the pinion portion 77 is located and the inner circumference of the upper end of the center pipe 75.

A rack pipe 81 having a rack portion 82 that engages with the pinion portion 77 is fitted and fixed to the front portion of the cylinder body 41 of the actuator 30. A bearing guide groove 83 is formed on the rear side of the rack part 82 of the rack pipe 81, and is supported by a ball bearing 85 or a rod 86 that fits in the guide groove 83, and the rod 86 is mounted, for example, under the steering wheel on the right side of the vehicle body. It is installed on the hold pipe 15 or the like (see FIGS. 10 and 11 above).

Here, FIG. 9 shows normal operation when the bar handle 7 is not turned and is running straight, and the oil passage 51 enters as shown by the arrow.
The oil flowing into the valve hole 32 from the oil passage 52 provided in the valve hole 32 from the runt 61 of the spool valve 33
, 53 to the lands 62, 63, and is returned to the reservoir tank T via the return oil passage 59 directly and via the oil passage 64. In addition, a check valve 37 installed in the spool valve 33 and allowing flow only from the return oil path 59 side to the input oil path 51 side allows oil to circulate within the actuator 30 when the pump is stopped.

When the bar handle 7 is turned to the right, the inner shaft 22 is twisted according to the steering force, and the steering shaft ent 25
The outer shaft 21 connected by the spline fitting part 27 with a gap C as shown in FIG. 6 first rotates clockwise by the amount of twist as shown by the arrow R in FIG. The spool rod 34, which is pivotally connected to the lever 72, moves rearward as shown in Figure i12. The inner shaft 22, which is a torsion bar integrated with the shaft end 25, is twisted in accordance with the gap 0 minutes, that is, the inner shaft 22 is twisted like the outer shaft 21.
There will be a phase difference that lags behind the rotation of . Therefore, the steering force corresponding to the torsion of the inner shaft 22 is transmitted to the shaft end 25, and from the pinion part 77 provided in the center pipe 75 integrated with the shaft end 25, the rake Part 8
The steering force corresponding to the torsion of the inner shaft is also transmitted to the actuator 30 through the engagement with the actuator 2 in a linear motion consistent with the actuator center.

In this manner, at the beginning of steering, the spool lever 72 on the input side rotates about the steering shaft center with a certain phase difference from the center pipe 75 on the output side.

The phase difference between the steering outer shaft 21 and the steering inner shaft 22 is amplified by the swing radius of the spool lever 72 and is transmitted from the spool rod 34 to the spool valve 33. By operating this spool valve 33, the oil flow changes as shown in FIG.

That is, when the spool valve 33 moves backward, the oil enters as shown by the arrow and flows through the oil passage 51, the land 61, and the oil passages 52, 5.
6. Oil in the front chamber is sent to the rear chamber of the cylinder 42 via the oil passages 54 and 53 through the land 6.
3, the oil in the rod hole 45 also flows into the land 63 from the oil passages 57 and 58, and the oil in the rod hole 45 also flows into the land 63 from the oil passage 64
The oil returns from there and flows into the oil path 59.

The pressure of the oil sent into the rear chamber of the cylinder 42 in this way causes the piston 43 to move forward within the cylinder 42, or the piston rod 44 moves toward the rod end 47.
Since the actuator 30 is supported by the vehicle body, the actuator 30 moves rearward. As the actuator 30 moves backward, force is transmitted from the rack section 82 at the front of the cylinder body 41 to the steering shaft end 25 through the engagement of the pinion section 77, and in this way, the steering shaft end 25 is rotated by hydraulic pressure. The steering force is reduced.

Further, when the input from the bar handle 7 exceeds the gap C, the steering force is directly transmitted from the spline fitting portion 27 to the steering shaft end 25.

When the bar handle 7 is turned to the left, the spool lever 72 is moved from the outer shaft 21, which rotates counterclockwise as shown by the arrow in FIG. The spool valve 33 is moved forward via the spool rod 34 as shown in FIG. The steering force of the torsion of the inner shaft 22, which functions as a torsion bar with a phase difference that lags behind the rotation of the outer shaft 21, is transmitted from the shaft end 25 to the actuator 30 via the pinion section 77 and the rack section 82, and is input at the initial stage of steering. Side spool lever 72 or output side center pipe 7
It rotates around the steering shaft center with a certain phase difference of 5.

By moving the spool valve 33 backward, oil enters as shown by the arrow and is sent into the front chamber of the cylinder 42 through the oil passage 51, the runt 61, and the oil passages 53 and 54. Also, the cylinder 42
The oil in the rear room is oil passages 55, 56, 52, and land 62.
It flows back into the oil passage 59, and further flows into the oil passage 64 and the runt 6.
3 and oil passages 58 and 57 into the rod hole 45.

The piston 43 moves backward in the cylinder 42 due to the pressure of the oil sent into the front chamber of the cylinder 42. In other words, the actuator 30 moves forward and moves from the rack part 82 at the front part of the cylinder body 41 through the engagement of the pinion part 77. force is transmitted to the steering shaft end 25.

The above hydraulic power steering device can be easily installed in commercially available vehicles by simply replacing the steering system.

Since a rod hole 45 is provided in front of the cylinder 42 through which the piston rod 44 moves forward and backward, there is no need for sealing measures on the front wall of the cylinder 42, and the provision of an oil passage 57 eliminates the need for sealing measures when the piston rod 44 moves. hole 45
The oil inside can be supplied and discharged, and the piston rod 44 can be moved back and forth smoothly without resistance.

In the above, regarding the meshing between the binion part 77 of the center pipe 75 fixed to the steering shaft ent 25 and the rack part 82 of the rack pipe 81 fixed to the cylinder body 41 of the actuator 30, the rack part 82 has meshing teeth with respect to the binion part 77. The steering shaft tries to escape outward from the center due to the partial pressure caused by the pressure angle. However, the rack portion 8 of the rack pipe 81
A ball bearing 85 positioned and supported by a rod 86 fixed on the frame lO side is fitted into the bearing guide groove 83 formed on the rear side of the rack 82, so that the rack part 82 always meshes normally with the binion part 77. It has become.

Next, a comparison will be made between the conventional structure and the structure of the present invention with regard to the configuration of the connecting portion between the power assist actuator 30 provided separately from the steering mechanism to which the present invention is applied and the steering shaft 20.

First, the conventional structure of Japanese Patent Application No. 63-42468 is of a link mechanism type in which a center arm fixed to the steering shaft 20 is pivotally connected to the actuator 30, so the center arm and the actuator are pivotally connected as shown in Fig. 17. The point draws a trajectory that moves in an arc from the steering neutral position N to the left and right maximum steering positions a and b depending on the steering angle.

Therefore, the center line of the actuator swings around the fulcrum P and changes direction (see C- and Cb). Therefore, the power assist force F1 of the actuator acts on the steering shaft by only the component force F1 corresponding to the moment of the steering force, and the power assist force becomes F,・R, which is smaller than the force F8・R near the steering neutral position N. will also decrease. That is, the power assist force decreases as the steering angle increases from the vicinity of straight-ahead travel. Here, the steering shaft center is 0 point.

On the other hand, in the present invention, the connection portion between the actuator 30 (cylinder body 41) and the steering shaft 20 (shaft end 25) is connected to the rack portion 82 provided on the cylinder body 41 and the binion portion 77 provided on the shaft end 25. Since the rack and pinion mechanism is made by meshing the 7 and 7 with each other, as shown in FIG.
The rack portion 82 that engages with the steering wheel 7 draws a trajectory that moves linearly from the neutral steering position N to the left and right maximum steering positions a l + b l in response to steering. In other words, since the actuator 30 only performs linear motion along the center line (cylinder center) CI, the power assist force does not change depending on the steering angle and is always F
It becomes a-R. In this way, it is possible to obtain power assist forces F and -R that do not change, so they change depending on the driver's required steering force or the turning radius of the vehicle (increases according to the steering angle).
Therefore, the operability can be further improved.

In this case, since the spool lever 72 and the spool valve 33 are connected via the spool rod 34 and the ball joints 73.35 at both ends, the spool lever 72 and the spool valve 33 are Swinging of the lever 72 and the spool rod 34 is absorbed by each ball joint 73.35.

Incidentally, as shown in FIG. 14, a rack and pinion mechanism may also be adopted for the connection structure between the steering outer shaft 21 and the spool valve 33.

That is, as shown in FIGS. 15 and 16, the input pipe 91 with the binion portion 92 formed thereon is fixed to the outer shaft 21 by welding or the like, and the rack par 93 is integrally fixed to the spool valve 33 by welding or the like. , its rack part 9
4 is meshed with the pinion portion 92. In this case, since the valve hole 32 in the body of the actuator 30 and the cylinder 42 are parallel, the upper rack part 94 is parallel to the lower rack part 82, and the steering direction from the outer shaft 21 to the spool valve 33 can also be detected. This is performed in a linear motion parallel to the center line of the actuator 30. however,
This backlash in the rack portion 94 and the pinion portion 92 must be made as small as possible in order to sensitively transmit the steering direction to the spool valve 33.

Although the power steering device of the present invention is installed on a saddle type four-wheeled vehicle in the embodiment, it is also possible to apply it to general vehicles.

[Effects of the Invention] As described above, according to the power steering device of the present invention, the actuator and the steering shaft, which are separately provided from the steering mechanism, can be connected to the ink portion provided on the actuator and the nion portion provided on the steering shaft. Because of the structure in which the rack and pinion mechanisms are connected by meshing with each other, the actuator can be moved along the centerline direction by linear movement of the rack part that meshes with the pinion part of the steering shaft that rotates by steering. Therefore, it is possible to prevent swinging changes in the center line of the actuator and effectively utilize the power assist force, thereby further improving operability.

[Brief explanation of the drawing]

Fig. 1 is an external side view of a straddle-type four-wheel vehicle equipped with the device of the present invention, Fig. 2 is a schematic perspective view showing the steering system, power transmission system, and suspension system, and Fig. 3 is a FIG. 4 is a schematic side view of the front part of the vehicle body frame showing the arrangement of actuators, etc., FIG. 4 is a front view taken from the direction of arrow ■ in FIG. 3, FIG. 5 is a longitudinal side view of the actuator portion including the steering shaft, and FIG. A cross-sectional view along the arrow ■-■ line in FIG. 5, FIG. 7 is a plan view taken from the direction of the arrow ■ in FIG. 5, and FIG. 8 is a cross-sectional view along the arrow ■-■ line in FIG. FIG. 9 is an enlarged vertical sectional side view of the inside of the actuator including the connection part with the steering shaft when traveling straight, FIG. 1O is a cutaway plan view of the main part of the rack and pinion mechanism, and FIG. 12 and 13 are longitudinal sectional side views similar to FIG. 9 when the steering wheel is turned to the right and left, respectively. Figure 15 is a longitudinal cross-sectional side view similar to Figure 9 showing the case where a rack and pinion mechanism is also adopted for the input connection to the spool valve, Figure 15 is a cutaway plan view of the main part of the rack and pinion mechanism, and Figure 16 is a 15 is a cutaway front view of the main part along the arrow Jun-Ren line, and FIG. 17 is a line diagram explaining the locus of the connection point between the steering shaft and the actuator. In addition, in the drawing, 20 is the steering shaft. 30 77 is a pinion portion, and 82 is a rack portion.

Claims (1)

[Claims] In a vehicle that is equipped with a power assist actuator that is connected to a steering shaft and is provided separately from a steering mechanism, a connecting portion between the actuator and the steering shaft is provided on a rack portion provided on the actuator and on the steering shaft. A power steering device comprising a rack and pinion mechanism in which a pinion part and a pinion part are meshed with each other.