JPH01168573A - Power steering - Google Patents

Abstract

PURPOSE:To make an effective steering state securable by performing steerage with a power cylinder alone when steering load is small, and making working force of an auxiliary cylinder addable in addition when the steering load is large. CONSTITUTION:A rack piston 11 and a sensor gear 7 are surrounded by a housing 12 solidly formed together with a gear housing 1, while this housing 12 doubles as an auxiliary cylinder 12a of the rack piston 11, and a front oil chamber 13 and a rear oil chamber 14 are formed in this auxiliary cylinder 12a by the rack piston 11. The rear oil chamber 14 in the auxiliary cylinder 12a forms a chamber continued to a front oil chamber 6 of a power cylinder 1a. Pressure oil controlled by a directional control valve 8 is fed to the power cylinder 1a and the auxiliary cylinder 12a according to size of steering load via a load sensitive valve 15 being set up on a pressure-oil circuit.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a power steering device for an automobile.

<Prior Art> In an automobile power steering system, an integral or semi-integral power steering system consists of a ball screw rotated by a steering shaft, a ball nut piston that is threadedly engaged with the ball screw and moves in the axial direction, and a ball screw that is rotated by a steering shaft. a cross shaft having a sector gear that meshes with a rack formed on the nut piston; a gear housing that also serves as a power cylinder that surrounds the pole nut screws 1 to 1 and the sector gear and has oil chambers formed in the front and rear (left and right) of the ball nut piston; and a directional switching valve that is provided within the gear housing and controls supply and discharge of pressure oil to and from the oil chamber.

<Problems to be solved by the invention> The necessary conditions for such a power steering device are: 8. Reduction of the amount of operation B, reduction of cutting blades C1 Improvement of steering stability at high speed, cost reduction [ , weight reduction [and fuel efficiency].

However, the above A and B, B and C, B and E, B and F,
The relationship between B and D was a contradictory theme, and it was difficult to reconcile them.

Means for Solving the Problems> The present invention has been made in view of the above-mentioned problems of the conventional art, and its characteristic configuration is a pole screw rotated by a steering shaft, and a pole screw that is threadedly engaged with the ball screw in the axial direction. A power cylinder includes a moving ball nut piston, a cross shaft including a sector gear that meshes with a rack formed on the ball nut piston, and a power cylinder surrounding the ball nut piston and sector gear and forming an oil chamber before and after the ball nut piston. A gear housing that also serves as
In the power steering device including a direction control valve provided in the gear housing and controlling the supply and discharge of pressure oil to the oil chamber of the power cylinder, the rack piston meshing with the sector gear is aligned with an axis parallel to the ball nut piston. A cylinder is provided so as to be movably arranged in parallel, surrounds the rack piston and the sector gear, and has an oil chamber formed before and after the rack piston, and the rear oil chamber of this cylinder is connected to the front oil chamber of the power cylinder. When the steering load is small, the pressure oil controlled by the directional control valve is supplied and discharged to the front oil chamber or the rear oil chamber of the power cylinder, and the auxiliary cylinder is in lost motion, and when the steering load is large, the power cylinder and the It is equipped with a load-sensitive valve that controls supply and discharge to the front oil chamber or rear oil chamber of the auxiliary cylinder.

With the above configuration, when the steering load is small, the steering is performed using the power cylinder's independent operating force, and the auxiliary cylinder is in lost motion. In addition, when the steering load is large, use the operating force of both the power cylinder and the auxiliary cylinder to steer the vehicle.
-F conditions were achieved.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. 1 is a gear housing that also serves as a power cylinder 1a. Reference numeral 2 denotes an input shaft rotatably supported by the gear shaft 1, and is connected to a steering shaft 2a. A ball screw 3 is rotatably held in the gear housing 1 and faces into the power cylinder 1a. This ball screw 3
is coaxially connected to the input shaft 2 via a torsion bar 4. A ball nut piston 5 is screwed onto the ball screw 3 through a pawl, and is slidably fitted into the power cylinder 1a, and has a front oil chamber 6a and a rear oil chamber 6b inside the power cylinder 1a. and is moved in the axial direction by the rotation of the ball screw 3.

The ball nut piston 5 is provided with a rack 5a, which meshes with a sector gear 7 provided on a cross shaft 7a. 10 indicates a pitman arm connected to the cross shaft 7a.

A direction control valve 8 is controlled by the rotational direction of the input shaft 2, and is provided in the gear housing 1 and supplies pressure oil from a hydraulic pump 9 driven by the engine to the front and rear oil chambers of the power cylinder 1a. Switching control is performed to supply the oil to either one of the oil chambers 6a, 6b and to discharge the oil from either the front or rear oil chambers 6a, 6b to the tank.

In the power steering device of the present invention, the rack piston 11 that meshes with the sector gear 7 of the cross shaft 7a is arranged side by side so as to be movable along an axis parallel to the ball nut piston 5. The rack piston 11 and the sector gear 7 are surrounded by a housing 12 integrally formed with the gear housing 1. This housing 12 also serves as an auxiliary cylinder 12a for the rack piston 11, and the rack piston 11 moves forward into the auxiliary cylinder 12a. Oil chamber 13
and a rear oil chamber 14. Further, the rear oil chamber 14 in the auxiliary cylinder 12a forms a continuous chamber with the front oil chamber 6a of the power cylinder 1a.

Furthermore, a load sensitive valve 15 is arranged on the pressure oil circuit to control supply and discharge of the pressure oil controlled by the direction control valve 8 to the power cylinder 1a and the auxiliary cylinder 12a according to the magnitude of the steering load. .

Since the present invention is configured as described above, the following operation is performed. Pressure oil from the hydraulic pump 9, which is switched by the direction control valve 8 depending on the rotational direction of the input shaft 2, is controlled according to the magnitude of the steering load. Based on the load sensitive valve 15 which is switched, the power is supplied to the power cylinder 1a or the auxiliary cylinder 12a, and the ball nut piston 5 alone or both of the rack pistons 11 are actuated. That is, when the steering load is small, the oil is supplied to and discharged from the front oil chamber 6a or the rear oil chamber 6b of the power cylinder 1a, and the auxiliary cylinder 12a is set to lost motion.

When the steering load is large, the oil is supplied to and discharged from the rear oil chambers 6a, 13 or rear oil chambers 6b, 14 of the power cylinder 1a and auxiliary cylinder 12a.

Therefore, the ball nut piston 5 and the rack piston 11
By operating both of the above, it is possible to reduce the amount of operation and the number of stationary cutting blades. Further, if the pole nut cylinder 5 is operated independently, the steering force becomes heavy due to movement resistance of the rack piston 11.

As described above, these controls operate both the ball nut piston 5 and the rack piston 11 when traveling at low speeds or when the vehicle is stationary, and operate the pole nut piston 11 when traveling at high speeds by means of the load sensitive valve 15 which is switched according to the magnitude of the steering load. 5 It is said that it operates independently.

<Effects of the Invention> As described above, the present invention provides a rack piston and a cylinder in parallel with the power cylinder of conventional integral or semi-integral power steering, and provides a load that can be switched according to the magnitude of the steering load. The configuration uses a sensitive valve to operate either the ball nut piston of the power cylinder alone or both the rack piston of the auxiliary cylinder, which reduces the amount of operation by 1111 and improves the reduction of stationary cutting blades. This prevents excessive steering force and improves steering stability.

Furthermore, due to the above-mentioned improvements in performance, equipment such as hydraulic pumps, power cylinders, and auxiliary cylinders for medium-sized commercial vehicles can be applied to passenger cars, thereby reducing costs, weight, and fuel efficiency. Ru.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of the invention. 1... Gear housing, 1a... Power cylinder,
2... Input shaft, 3... Pole screw, 5... Ball Nara L-piston, 7... Sector gear, 7a... Cross shaft, 8... Directional control valve, 9... Hydraulic pump, DESCRIPTION OF SYMBOLS 11... Rack piston, 12... Housing, 12a... Auxiliary cylinder, 15... Load sensitive valve.

Claims (1)

[Claims] A ball screw rotated by a steering shaft,
a cross shaft that includes a ball nut piston that is threaded with the ball screw and moves in the axial direction; and a sector gear that meshes with a rack formed on the ball nut piston;
A gear housing that surrounds the ball nut piston and the sector gear and also serves as a power cylinder with oil chambers formed before and after the ball nut piston, and a direction provided within the gear housing that controls the supply and discharge of pressure oil to the oil chamber of the power cylinder. In a power steering device equipped with a control valve, rack pistons meshing with the sector gear are arranged so as to be movable along an axis parallel to the ball nut piston, and the rack piston and the sector gear are surrounded by An auxiliary cylinder having a chamber is provided, and the rear oil chamber of this auxiliary cylinder and the front oil chamber of the power cylinder are connected, and when the steering load is small, the pressure oil controlled by the direction control valve is transferred to the power cylinder. The auxiliary cylinder is provided with a load sensitive valve that controls supply and discharge to the front oil chamber or the rear oil chamber of the power cylinder and the auxiliary cylinder when the steering load is large. A power steering device characterized by: