JPH01309874A - Power steering device - Google Patents

Abstract

PURPOSE:To ensure auxiliary power only when necessary with a simple structure by installing a preset spring between the input/output shafts of a steering shaft and providing an actuator which receives turning force from the input shaft and which outputs an auxiliary power to the output shaft. CONSTITUTION:As the steering load of a steering shaft 20 becomes above the pre-load of a preset spring 81 installed between an input shaft 21 and an output shaft 27, the input shaft 21 is precedingly rotated generating difference in the rotation phase between the input/output shafts 21, 27. Thereupon, the spool rod 34 pivotally installed on a spool lever 72 and the spool valve 33 of a power- assisting actuator 30 which is one with the input shaft 21 are moved rearward. As a result, oil is fed under pressure to the rear oil pressure chamber of a cylinder 42 moving a piston 43 forward while moving the body side of the actuator 30 rearward. Thereby, power is transmitted to the output shaft 27 via a center arm 75 to lighten a steering force.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power steering device in which a preset spring is provided on a steering shaft.

[Prior art] As a power steering device that does not use a gear mechanism, the steering shaft is divided into an input shaft and an output shaft, and the input shaft and output shaft are connected with a torsion bar to create a phase difference in rotation. Japanese Patent Publication No. 49-23172 discloses a system in which a control valve is interposed between both shafts, and a power assist cylinder, a piston, and a swash plate mechanism are provided around the output shaft.

Although this power steering device had a simple appearance, it had a complex structure with a control valve interposed in the middle of the steering shaft, and a power assist cylinder, piston, and swash plate mechanism installed around the lower shaft. .

In order to make the power assist actuator more compact by using a simple input/output mechanism without incorporating a control valve section or a power assist cylinder section into the steering shaft, the present applicant has:
First, we proposed patent application No. 1983-42468.

This involves dividing the steering shaft into an inner shaft and an outer shaft, using the inner shaft as a torsion bar, and spline-fitting the shaft end fixed to the inner shaft and the outer shaft with a predetermined gap in the direction of rotation. The control valve part of the power assist actuator is connected to a lever provided on the outer shaft, and the power assist cylinder part is connected to an arm provided at the shaft end.

As a result, the torsion bar, which is the inner shaft, is twisted, creating a phase difference that lags behind the rotation of the outer shaft. A simple input/output mechanism can be constructed using the phase difference generating section, lever and arm, and a power assist actuator can be constructed separately from the steering shaft in a compact manner.

[Problems to be Solved by the Invention] However, the structure of the steering shaft is complicated due to the double structure in which a long torsion bar is passed over substantially the entire length within the outer shaft.

In addition, according to the torsion bar twisting method, the power assist actuator is always activated even with light steering force, and for example, in the case of a hydraulic type, the oil pump is driven.
Even when such a light steering force is applied, the engine requires horsepower to drive the oil pump, which increases the fuel consumption of the engine.

Therefore, an object of the present invention is to provide a power steering device that simplifies the structure of the steering shaft by eliminating the long torsion bar as described above, and also provides a dead area in which the power assist actuator is not activated by light steering force. Our goal is to provide the following.

[Means for Solving the Problems] In order to achieve the above problems, the present invention provides the steering shaft 20 with an input shaft 21 side member and an output shaft 27 side member. 27 side member are spline-fitted with each other with a predetermined gap C in the rotational direction, and the power assist actuator inputs rotation from the input shaft 21 side member and outputs auxiliary power to the output shaft 27 side member. 30, and between the input shaft 21 side member and the output shaft 27 side member, a preset spring 81 to which a preload is applied is installed between the input shaft 21 side member and the output shaft 27 side member, respectively. It is characterized by being provided in a locked manner.

[Operation] When a steering load is input to the steering shaft 20,
The input shaft 2 is spline-fitted to the output shaft 27 side member with a predetermined gap C in the rotational direction.
The first side member tries to rotate first. At this time, if the steering load exceeds the preload of the preset spring 81 which is locked to the input shaft 21 side member and the output shaft 27 side member and is provided between the two members, the preload of the preset spring 81 will be increased. Against this, the input shaft 21 side member rotates first by the gap 0, that is, the input shaft 21 side member and the output shaft 27
A rotational phase difference occurs between the side member and the side member. The power assist actuator 30, which receives the rotation of the input shaft 21 side member, outputs auxiliary power to the output shaft 27 side member, thereby reducing the steering force.

In this way, the long torsion bar is eliminated, and a preset spring 81 is provided between the input shaft 21 side member and the output shaft 27 side member of the steering shaft 20, and is engaged with each of both members. Since this is adopted, the structure of the steering shaft is simplified.

In the case of a light steering load that is less than the preload of the preset spring 81, the input shaft 21 side member and the output shaft 27 side member rotate together via the preset spring 81, that is, there is a gap between the two members. Since no rotational phase difference occurs, the actuator will not operate.

In other words, if the steering force is light, such as a slight steering force when driving straight, the preload of the preset spring 81 will be lower than the preload, and the actuator 30 will not operate, so in the case of a hydraulic actuator, for example, the oil pump will be in the lowest oil pressure state, and the engine will pump the oil. The pump requires less horsepower to drive.

Therefore, fuel efficiency during light steering is 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 equipped with low-pressure tires at the front and rear of a vehicle body in which an engine 1 is mounted in the center are shown in FIG. The engine power is transmitted to the front wheels 2 and rear wheels 3, 4 is a front fender, 5 is a seat, and 6 is a rear fender. Operate the bar handle 7 located above. The bar handle 7 is fixedly attached 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, and tie rods 9 are installed between a steering arm 29 fixed to the lower end of the steering shaft 2 and a knuckle arm 8 supporting the front wheel 2, respectively. 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 11 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. An actuator 30 is arranged at.

The steering shaft 20 has an upper part supported by a holder 18 at the front end of the main pipe 11, and a lower part supported by a bracket 19 installed between the steering under-hold pipes 15, and an actuator 30 extending from the steering under-hold pipe 15 at the rear. It is pivotally supported on the right pipe end 16 via a vertical shaft 17.

The hydraulic power steering device is comprised of a control valve section (2) built into the actuator 30, a power assist cylinder section 31, an oil reservoir tank T1, an oil pump P, and the like. The reservoir tank T is fixed between the upper parts of the front pipes 13, and the oil pump P
is fixed to the cylinder head 1a of the engine 1 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 H1, and the oil pump P and the actuator 30 are connected to each other by a suction hose H1. Feed hose H2 is connected, actuator 3o and reservoir tank T are connected to return hose H3
Connected with

By the way, the steering shaft 20 consists of a long input shaft 21, a short inner shaft 24 at its lower end, and an output shaft 27, as shown in FIG. 5 and FIG. 6 showing an enlarged view of the main part thereof. 21 is connected at its upper end to a steering bridge 23 to which the bar handle 7 is fixed. The upper part of the inner shaft 24, whose upper end is closed and the lower end is open, is inserted into the lower part of the input shaft 21 and fixed by welding, and the upper part of the output shaft 27 is inserted into the inner shaft 24 between the upper and lower parts. bearing 28
A steering arm 29 is fixed to the lower end of the output shaft 27.

A spool lever 72 is bolted to the stayer 1 fixed to the outer periphery of the lower part of the input shaft 21 by welding, and a center arm 75 is fixed to the outer periphery of the intermediate portion of the output shaft 27 by a serration fitting part Se. .

This center arm 75 has a housing shape inside,
The circular flange portion 25 at the intermediate portion of the inner shaft 24 is inserted into the circular inner peripheral portion of the upper portion of the center arm 75, and the two are spaced apart from each other by a predetermined gap c, c on both sides in the rotational direction as shown in FIG. 7(C). They are connected by a spline fitting portion Sp provided.

Further, the flange portion 25 of the inner shaft 24 and the bottom of the center arm 75 both have a bottle hole 26 parallel to the axis.
．． 76 are formed respectively, and both the bottle holes 26 and 76 substantially coincide with each other when the inner shaft 24 and the center arm 75 are connected by the spline fitting portion 5p. Further, a circular storage part 77 is formed in the center arm 75 to cover the lower outer periphery of the flange part 25 of the inner shaft 24, and a preset spring 81 having a C-shape in plan view is disposed within this storage part 77 as shown in FIG. 7(d). is stored.

This preset spring 81 is C-shaped in plan view and square in cross section.
Upper and lower input bins 83 and output bins 84 are provided sandwiched between both ends 82 and 82 forming the notched interior, respectively. The input bin 83 is inserted and held in the pin hole 26 of the inner shaft 24, and the output pin 84 is inserted and held in the pin hole 76 of the center arm 75.

The above preset spring 81 has an input bin 83 and an output bin 84 sandwiched between both ends 82 and 82.
are urged into a compressed state with a preset load, and within the range of the set preload, the input pin 83
and output bin 84 are in a consistent state.

The power assist actuator 30 is shown in Figure 7.
The configuration is shown in FIGS. 8(a) and 8(b) and enlarged in FIG. 8 and subsequent figures. This actuator 30 is formed by bolting a valve body 31 onto a cylinder body 41,
A valve hole 32 provided in the valve body 31 and opening at the front, and a cylinder 42 provided at the cylinder body 41 and opening at the rear.
are vertically parallel.

A spool rod 34 is pivotally connected to the forward protruding part of a spool valve 33 installed in the valve hole 32 with a vertical pin 35, and the front part of the rod 44 of a piston 43 installed in the cylinder 42 via a seal projects forward. It faces into the round hole 45 at the front of the cylinder body 41. A boot 36 is provided between the valve body 31 and the spool rod 34, a check valve 37 is built into the upper part of the valve body 31, and joints 38 and 39 are provided on the upper surface to connect the hoses H1 and H2. . The rear part of the piston rod 44 is sealed to the cylinder 42 by a rod guide 46, etc., and a rod end 47 provided at the rear protrusion is pivotally supported on the vertical shaft 17 via a rubber bushing 48 with a collar. A boot 49 is provided between 47.

The spool lever 72 is connected to the input shaft 2.
1. The front end of the spool rod 34 protrudes to the right from the outer periphery of the lower part, and the front end of the spool rod 34 is connected to the ball joint 74 via the vertical pin 73.
Pivotally connected at.

Further, the center arm 75 is also connected to the output shaft 2.
7 Projects to the right from the outer periphery of the intermediate portion, and the front end of the cylinder body 41 is pivotally connected to the right end of the cylinder body 41 via a vertical bolt 78 and a bearing 79. In the embodiment, when the vehicle is traveling straight, the vertical pin 73, the ball joint 74, and the vertical bolt 78 are aligned on the same axis.

Next, the operation will be explained.

The oil discharged from the oil pump P passes through the feed hose H2 to the spool valve 3 in the actuator 30.
Pass through the 3rd grade and return from the hose H3 to the reservoir tank T
After being filtered by a filter, it is circulated to the oil pump P through a suction hose (11). Inlet oil passage 51 and return oil passage 5 provided in actuator 30
A check valve 3 is installed in the bypass oil passage 58 between the oil return passages 59 and 9 and allows flow only from the return oil passage 59 to the entry oil passage 51.
7, oil is circulated within the actuator 30 when the pump is stopped.

When moving straight without turning the bar handle 7, oil flows from the oil passage 51 into the valve hole 32 as shown by the arrow in FIG. Front and rear oil passages 55, 52 provided
The oil is distributed to the front and rear lands 62 and 64 through the oil holes 63 and 65, passes through the spool central oil passage 66, and is returned to the reservoir tank T through the return oil passage 59.

Turn the bar handle 7 to the right and the steering shaft 2
0 is an input shaft 2 integrated with an inner shaft 24 connected to an output shaft 27 by a spline fitting part Sp with a gap C as shown in FIG. 7(C).
1 tries to rotate clockwise by the gap C as shown by the arrow R in FIG. At this time, if the steering load exceeds the preload of the preset spring 81, the input shaft 21 rotates first by the gap 0, against the preload of the preset spring 81, that is, the input shaft 21 and the output shaft 27 rotate. A rotational phase difference occurs between the two.

As a result, the spool rod 34, which is pivotally connected to the spool lever 72 integral with the input shaft 21, moves rearward as shown in FIG.

In this way, at the beginning of steering when the preload of the preset spring 81 is exceeded, the spool lever 72 on the input side rotates about the center of the steering shaft with a certain phase difference from the center arm 75 on the output side.

And input shaft 21 and outer shaft 27
The phase difference is amplified by the swing radius of the spool lever 72 and 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 central land 61, and the oil passage 52.
From there, it is fed into the rear hydraulic chamber of the cylinder 42 via oil passages 53 and 54 in the cylinder body 41. Further, the oil in the front hydraulic chamber of the cylinder 42 flows from the oil passage 56 in the cylinder body 41 to the front land 62 via the oil passage 55, and the oil in the rod hole 45 also flows from the oil passage 57 in the cylinder body 41 to the front land 62. It flows into the land 62, and flows to the oil hole 63, the oil path 66, and the return oil path 59.

The piston 43 moves forward inside the cylinder 42 due to the pressure of the oil sent into the rear hydraulic chamber of the cylinder 42 in this way, but since the piston rod 44 is supported by the vehicle body at the rod end 47, the actuator 30
The body side of the will move backward. Power is transmitted to the integrated output shaft 27 by the rear 8 arms on the body side of the actuator 30 via the center arm 75 pivotally connected to the front part of the cylinder body 41, and the output shaft 27 is rotated by hydraulic pressure. Steering force is reduced.

In this case, the piston rod end 47 is pivotally supported via the rubber bush 48 to the vehicle body frame 10 (the steering underhold pipe end 16 on the right side) so as to be able to swing about the vertical axis 17, so that the spool lever 72 and the center arm The left and right rocking of the actuator 30 due to the rotation of the actuator 75 is absorbed.

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

Turn the bar handle 7 to the left and the preset spring 8
If the steering load exceeds the preload of the steering wheel, first the clearance 0 is
The spool valve 33 is connected to the spool valve 33 via the spool lever 72 and the spool rod 34 from the input shaft 21, which rotates counterclockwise as shown by the arrow in FIG. 7(a).
Move forward as shown. Oil enters the oil passage 51 as shown by the arrow through the front eight positions of this spool valve 33.
The oil is sent from the central land 61 and oil passages 55 and 56 to the hydraulic chamber in front of the cylinder 42 . Further, the oil in the rear hydraulic chamber of the cylinder 42 flows from the oil passages 54, 53, 52, the rear land 64, and the oil hole 65 into the oil passage 66, where it is distributed back and forth from the oil hole 63, the front land 62, and the oil passage 57. It flows into the rod hole 45 and also flows from the oil passage 66 to the return oil passage 59. The pressure of the oil sent into the front hydraulic chamber of the cylinder 42 causes the piston 43 to move rearward within the cylinder 42, that is, the body side of the actuator 30 moves forward, and force is transmitted from the center arm 75 to the output shaft 27.

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

Since a round hole 45 is provided in front of the cylinder 42 through which the piston rod 44 moves forward and backward, sealing measures on the front wall of the cylinder 42 are not required. 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, when the steering force is a light steering load that is less than the preload of the preset spring 81, the input bin 83 and output pin 84 sandwiched between the both ends 82 and 82 of the preset spring 81 and the preset spring 81 itself are used. The input shaft 21 (including the inner shaft 24) and the output shaft 27 rotate together. That is, since no rotational phase difference occurs between the input shaft 21 and the output shaft 27, the actuator does not operate.

In other words, when the steering force is light, such as a slight steering force when traveling straight, the preload of the preset spring 81 is lower than the preload, and a region (b) in which the actuator 30 does not operate can be provided as shown in the solid line characteristic (a) in FIG. Therefore, in the case of the hydraulic actuator 30 of the embodiment, the oil pump P is in the lowest hydraulic pressure state, and the driving horsepower of the oil pump P by the engine 1 can be reduced. Therefore, fuel efficiency can be improved when the steering force is light.

In this respect, in the torsion bar torsion method using a double-structured steering shaft in which a long torsion bar is passed through almost the entire length of the outer shaft, the actuator operates even under light steering force as shown in the chain line characteristic (c), and the oil pump The driving horsepower of the engine was large.

The above preload setting of the preset spring 81 is arbitrarily set depending on the model and intended characteristics.

In the embodiment, the power steering device of the present invention is installed on a straddle-type four-wheeled vehicle, but the power steering device of the present invention can also be applied to general vehicles.

[Effects of the Invention] As described above, according to the power steering device of the present invention, the preset spring is provided between the input shaft side member and the output shaft side member of the steering shaft by being locked to each of the members. , it is possible to simplify the steering shaft structure by eliminating the torsion bar, and also to provide a trouble-free region where the power assist actuator does not operate with light steering force.

Therefore, for example, in the case of a hydraulic actuator, fuel efficiency can be improved by reducing the driving horsepower of the oil pump by the engine when the steering force is light.

[Brief explanation of the drawing]

Figure 1 is an external side view of a straddle-type four-wheel vehicle equipped with the power steering device of the present invention, Figure 2 is a schematic perspective view showing the steering system, power transmission system, and suspension system, and Figure 3 is a power assist vehicle. 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 in the direction of the arrow rv force in FIG. 3; FIG. 5 is a longitudinal side view of the actuator portion including the steering shaft; FIG. 7(a) and 7(b) are enlarged vertical cross-sectional views of the preset spring portion, and FIGS.
A partial plan view taken along the arrow A-A line in the figure and a partial front view taken from the direction of the arrow B in the figure, and FIG. 7 (c) and (d) are cross-sectional views taken along the arrow C-C line in FIG. 8 is an enlarged longitudinal sectional view of the inside of the actuator when the actuator is moving straight, and FIGS. 9 and 10 are similar enlargements when the handle is turned to the right and left, respectively. A longitudinal side view, FIG. 11 is a characteristic diagram showing the relationship between the steering wheel phase difference and the steering wheel. In addition, in the drawing, 7 is a steering wheel, 20 is a steering wheel preset, 21 is an input shaft, 27 is an output shaft, 29 is a steering arm, 30 is a power assist actuator, ■ is a control valve part, S
is the power assist cylinder part, 72 is the spool lever,
75 is the center arm, 81 is the preset spring,
83 is input pin, 84 is output pin, Sp
is a spline fitting part, and C is a gap.

Claims (2)

[Claims] (1) An input shaft side member and an output shaft side member are provided on the steering shaft, and the input shaft side member and the output shaft side member are spline-fitted to each other with a predetermined gap in the rotational direction, and the input shaft side member is A power assist actuator is provided that inputs rotation and outputs auxiliary power to the output shaft side member, and a preset spring with a preload is installed between the input shaft side member and the output shaft side member on the input shaft side. A power steering device comprising: a member and an output shaft side member that are respectively engaged with each other. (2) In the actuator, the control valve part and the power assist cylinder part are integrally constructed, and the control valve part is connected to the input shaft side member and the power assist cylinder part is connected to the output shaft side member. 1. The power steering device according to 1.