JPH05262247A - Ball screw type hydraulic power steering device - Google Patents

Abstract

PURPOSE:To eliminate the excessive play of a handle and prevent the occurrence of reduction of a steering auxiliary force by inserting a piston in an inner cylinder and radially and elastically displaceably supporting the inner cylinder to a housing. CONSTITUTION:An inner cylinder 40 is radially displaced and a ball nut 7 is radially displaceable. When radial pressurization is applied on the ball nut 7, the ball nut 7 is radially displaced, the ball nut 7 and a ball screw 2 are pressed against each other through a ball 6 and a relative clearance between the ball screw 2 and the ball nut 7 is removed. Since a piston 8 is pressed against the inner surface of the inner cylinder 40 and the inner cylinder 40 is radially elastically displaced, friction between the piston 8 and the inner cylinder 40 is reduced. This constitution prevents wear of the inner surface of the inner cylinder 40 and prevents the occurrence of leakage of oil between a pair of oil chambers 46 and 47.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw type hydraulic power steering device.

[0002]

2. Description of the Related Art A ball screw which is rotated by a steering input, and a housing which supports the ball screw,
A ball screw including a ball nut that meshes with the ball screw, a rack formed on the ball nut, a sector gear that meshes with the rack, and an output shaft that is integrated with the sector gear and is supported by the housing. Conventional steering devices have been used.

In such a ball screw type steering device, when the ball screw is rotated by a steering input, the nut moves axially, and the axial movement of the nut causes a sector gear meshing with a rack formed on the nut. When the sector gear rotates, the output shaft rotates. The rotation of the output shaft causes a steering member such as a pitman arm to swing, and the swing of the steering member is transmitted to a steering wheel that is connected to the steering member via a tie rod, a knuckle arm, or the like. Steering is done.

In the ball screw type steering device as described above, there is a problem that the play of the steering handle becomes excessive when the ball screw and the ball nut rattle relative to each other.

Therefore, in the ball screw type manual steering device, a radial preload is applied to the ball nut to eliminate relative rattling between the ball screw and the ball nut.

[0006]

In the ball-screw type manual steering device, there is no device that prevents the radial displacement of the ball nut. Therefore, when a preload is applied to the ball nut in the radial direction, the ball nut can be displaced in the radial direction, so the ball screw and the ball nut are pressed against each other via the ball, which causes the relative movement of the ball screw and the ball nut. Rattling is eliminated.

However, in the ball screw type hydraulic power steering device, a piston is integrated with the ball nut, and the interior of the housing is partitioned by the piston to form a pair of oil chambers, which are arranged depending on the steering direction. A steering assist force is applied by the high-pressure oil supplied to the oil chamber. The piston is in close contact with the inner surface of the housing via a seal ring or the like so that oil does not leak between the pair of oil chambers. When the piston is in close contact with the inner surface of the housing, the piston and the ball nut are integral with each other, and the radial displacement of the ball nut is prevented by the housing. Therefore, in the ball screw type hydraulic power steering device, even if a radial preload is applied to the ball nut, the relative rattling of the ball screw and the ball nut cannot be removed.

Further, in the ball screw type hydraulic power steering device, a part of the reaction force acting on the steering wheel from the road surface is supported by the inner surface of the housing via the piston. Therefore, there is a problem in that the inner surface of the housing is worn to cause oil leakage and the steering assist force is reduced.

It is an object of the present invention to provide a ball screw type hydraulic power steering device which can solve the above-mentioned problems of the prior art.

[0010]

A feature of the present invention is that a ball screw that is rotated by a steering input, a housing that supports the ball screw, a ball nut that meshes with the ball screw, and a ball nut that are integrated with the ball nut. A piston formed into a ball nut, a rack formed on the ball nut, a sector gear meshing with the rack, and an output shaft integrated with the sector gear and supported by the housing. In a ball screw type hydraulic power steering device in which a pair of oil chambers are formed by partitioning the interior, and a high pressure oil supplied to the oil chambers in accordance with the steering direction generates a steering assist force, an inner portion is provided inside the housing. A cylinder is inserted and the piston is inserted inside the inner cylinder. Down is inserted, the inner cylinder is in that it is resiliently displaceably supported in the radial direction relative to the housing.

[0011]

According to the structure of the present invention, the inner cylinder is inserted into the housing, and the piston is inserted into the inner cylinder. Therefore, the piston is brought into close contact with the inner surface of the inner cylinder through the seal member, so that Oil leakage between oil chambers is prevented. Therefore, when radial preload is applied to the ball nut, the piston integrated with the ball nut pushes the inner cylinder in the radial direction. Since the inner cylinder is supported so as to be elastically displaceable in the radial direction with respect to the housing, the inner cylinder is displaced in the radial direction. Therefore, if a preload is applied to the ball nut in the radial direction, the ball nut can be displaced in the radial direction. Tatsuki is removed.

The piston is pressed against the inner surface of the inner cylinder by a part of the reaction force applied to the steering vehicle from the road surface. The inner cylinder is elastically displaced in the radial direction, so that the piston and the inner cylinder are separated from each other. The friction between them is reduced. Therefore, abrasion of the inner surface of the inner cylinder is prevented, and oil leakage between the pair of oil chambers can be prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

The ball screw type hydraulic power steering device 1 shown in FIGS.
A housing 5 that supports the ball screw 2 via bearings 3 and 4, a ball nut 7 that meshes with the ball screw 2 via balls 6, a piston 8 integrated with the ball nut 7, and the ball nut. 7 and a sector gear 10 that meshes with the rack 9, and a housing 5 that is integrated with the sector gear 10 and has bearings 12 and 13 interposed therebetween.
And an output shaft 11 supported by.

The ball screw 2 is connected to an input shaft 21 via a torsion bar 20, and the input shaft 21 is supported by a housing 5 via a bearing 22 and protrudes from the housing 5 via an oil seal 23. A steering handle (not shown) is connected to the input shaft 21.
Further, the seal rings 18 and 19 are interposed between the output shaft 11 and the housing 5, and the output shaft 11 has the dust seal 16
Through the housing 5. A pitman arm 14 is attached to the output shaft 11, and the pitman arm 14 is connected to a vehicle steering wheel (not shown) via a link rod and a knuckle arm.

As a result, when the input shaft 21 is rotated by operating the handle, the rotation is transmitted to the ball screw 2 via the torsion bar 20, so that the ball screw 2 rotates. The rotation of the ball screw 2 causes the ball nut 7 to move in the axial direction together with the piston 8. Since the movement of the ball nut 7 is transmitted to the output shaft 11 via the rack 9 and the sector gear 10, the output shaft 11
Rotates. The rotation of the output shaft 11 causes the pitman arm 14 to swing, and the swing of the pitman arm 14 is transmitted to the steering wheel via the link rod and the knuckle arm, so that the vehicle is steered.

The housing 5 has a first member 5a which covers the ball nut 7 and the piston 8, a second member 5b which is fitted to one end of the first member via a seal 30 and is connected by a bolt, and A third member 5c screwed into the other end of the first member 5a via a seal 31, and a first member 5c
A fourth member 5d that is cast integrally with the member 5a and covers the sector gear 10 and the output shaft 11, and a fifth member 5e that is fitted to the fourth member 5d via a seal member 32 and is connected by a bolt. It consists of and.

An inner cylinder 40 is inserted inside the first member 5a of the housing 5. The inner cylinder 40 is open at both ends and has an opening 40a on its side wall as shown in FIG. The sector gear 10
Engages with the rack 9 by entering the inside of the inner cylinder 40 through the opening 40a. Further, a dowel pin 55 is inserted into the inner cylinder 40 and the fifth member 5e of the housing 5 to prevent the inner cylinder 40 from rotating with respect to the housing 5.

The inner cylinder 40 is supported by an elastic O-ring 41 attached to the first member 5a of the housing 5, and is provided between the inner peripheral surface of the first member 5a and the outer peripheral surface of the inner cylinder 40. Is provided with a gap δ. Thereby, the inner cylinder 40 can be elastically displaced in the radial direction with respect to the cylinder 5. It should be noted that in order to prevent the inner cylinder 40 from moving in the axial direction and rattling, an O having elasticity is provided between one end surface of the inner cylinder 40 and the second member 5b of the housing 5.
The ring 42 is interposed. Further, in order to smooth the radial displacement of the inner cylinder 40, an annular member 43 having a small friction coefficient is provided between the other end surface of the inner cylinder 40 and the step surface formed on the first member 5a of the cylinder 5. Intervened.

The piston 8 is inserted inside the inner cylinder 40. By partitioning the inside of the housing 5 by the piston 8, a pair of oil chambers 46, 4
7 are formed. The piston 8 is in close contact with the inner surface of the inner cylinder 40 via a seal ring 45 in order to prevent oil leakage between the pair of oil chambers 46 and 47. In order to seal between the inner circumference of the piston 8 and the outer circumference of the ball screw 2, the tubular member 48 is inserted into the inner circumference of the piston 8 via the seal ring 49 and the retaining ring 51.
The ball screw 2 is inserted into the tubular member 48 via a seal ring 50. The inner cylinder 40
The O-ring 41 that supports the inner cylinder 40
Through the gap δ between the oil chamber 46 and the cylinder 5, both oil chambers 46, 4
It also serves as a seal member for preventing 7 from communicating with each other.

A control valve 60 is provided on the outer circumference of the input shaft 21. This control valve 60
Is a pump port 61 connected to a pump, a tank port 62 connected to a tank, a first port 63 communicating with one oil chamber 46 through an oil passage (not shown) formed in the housing 5, and the other. Second port 6 leading to the oil chamber 47 of
4 and a valve member 65 that rotates relative to the input shaft 21 due to the torsion of the torsion bar 20 based on the steering direction and steering resistance. The control valve 60 supplies the high pressure oil supplied from the pump port 61 to one of the oil chambers 46 and 47 according to the steering direction and the steering resistance, and the oil chamber 4
Bring oil from the other side of 6, 47 back to the tank. As a result, a hydraulic pressure acts on the piston 8 to generate a force for moving the ball nut 7 in the axial direction, that is, a steering assist force. A publicly known control valve 60 can be used.

A screw shaft 33 is screwed onto the fifth member 5e of the housing 5. The screw shaft 33 is the output shaft 1.
It is connected to the shaft 1 so as to be rotatable relative to the center of the shaft and not to move relative to the shaft. Further, the output shaft 11 is supported so as to be movable in the axial direction with respect to the housing 5. Accordingly, when the screw shaft 33 is rotated, the output shaft 11 moves in the axial direction. The teeth of the rack 9 and the teeth of the sector gear 10 are inclined to each other so that the backlash between the teeth of the rack 9 and the teeth of the sector gear 10 is adjusted by the axial movement of the output shaft 11. A lock nut 34 is screwed onto the screw shaft 33.

According to the above structure, the ball nut 7 is attached to the position shown in FIG.
When the radial preload is applied to the ball nut 7 by pushing it to the right in FIG. 2, the piston 8 integrated with the ball nut 7 pushes the inner cylinder 40 in the radial direction, so that the inner cylinder 40 is displaced in the radial direction. .. In the prior art, the piston comes into contact with the inner surface of the housing even if a preload is applied to the ball nut, so that radial displacement of the ball nut is prevented. However, according to the above configuration, the inner cylinder 40 is radially displaced. Since the ball nut 7 can be displaced, the ball nut 7 can be displaced in the radial direction. Therefore, if a radial preload is applied to the ball nut 7,
Is displaced in the radial direction, the ball nut 7 and the ball screw 2 are pressed against each other via the ball 6, and the relative rattling of the ball screw 2 and the ball nut 7 is removed.

The magnitude of the preload applied to the ball nut 7 is determined by the set value of the distance between the shaft center of the ball screw 2 and the shaft center of the output shaft 11.

Further, the piston 8 is pressed against the inner surface of the inner cylinder 40 by a part of the reaction force applied to the steering vehicle from the road surface, but the inner cylinder 40 is elastically displaced in the radial direction. Friction with the cylinder 40 is reduced. Therefore, abrasion of the inner surface of the inner cylinder 40 is prevented, and the pair of oil chambers 46, 4
Oil leakage between 7 can be prevented.

Further, in the above embodiment, since the first member of the housing 5 having a complicated shape does not come into contact with the piston 8, it is not necessary to polish the inner surface, while the inner cylinder 40 has a simple opening at both ends. The cylindrical shape facilitates the polishing of the inner surface and facilitates the polishing process.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the inner cylinder was supported via the O-ring which also serves as the seal member, but the supporting means is not limited as long as it is elastically supported.

[0028]

According to the ball screw type hydraulic power steering device of the present invention, the relative rattling of the ball screw and the ball nut can be removed by applying the radial preload to the ball nut. Your play will never be overkill. Further, even if a reaction force acts on the steering vehicle from the road surface, the inner surface of the inner cylinder is not worn and oil leakage between the pair of oil chambers can be prevented, so that the steering assist force does not decrease.

[Brief description of drawings]

FIG. 1 is a plan sectional view of a steering device according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a steering device according to an embodiment of the present invention.

FIG. 3 is a perspective view of an inner cylinder according to an embodiment of the present invention.

[Explanation of symbols]

 2 Ball Screw 5 Housing 7 Ball Nut 8 Piston 9 Rack 10 Sector Gear 11 Output Shaft 40 Inner Cylinder 46, 47 Oil Chamber

Claims (1)

[Claims] 1. A ball screw which is rotated by a steering input, and a housing which supports the ball screw,
A ball nut that meshes with the ball screw, a piston integrated with the ball nut, a rack formed on the ball nut, a sector gear that meshes with the rack, and a sector gear that is integrated with the sector gear and by the housing. A ball that has an output shaft supported and a pair of oil chambers is formed by partitioning the inside of the housing by the piston, and high pressure oil supplied to the oil chambers depending on the steering direction generates a steering assist force. In a screw type hydraulic power steering device, an inner cylinder is inserted into the housing, the piston is inserted into the inner cylinder, and the inner cylinder is supported so as to be elastically displaceable in a radial direction with respect to the housing. Ball screw type hydraulic power station Ring device.