JPH021717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that can change steering force according to vehicle speed.

The power steering device has a configuration in which a power piston is incorporated into a manual steering mechanism that engages a sector shaft, and the movement of a wormshaft in conjunction with a steering wheel is assisted by hydraulic pressure acting on the power piston. There is. Therefore, the power steering device with the above configuration enables light and quick steering of the vehicle, but simply reducing the steering effort will result in more steering phenomena than necessary at high speeds, causing a sense of anxiety for the driver. give.

For this reason, at high speeds, increasing the reaction force applied to the steering wheel and increasing the steering force will make the vehicle run more comfortably.Therefore, power steering devices that change the steering force in response to vehicle speed have been proposed. has been done.

One type of steering device that has been proposed in the past includes sub-reaction chambers provided on both sides of the valve piston.
The auxiliary reaction force chamber is communicated with the main reaction force chamber via an orifice, and both auxiliary reaction force chambers are made conductive through a circuit having a variable orifice, and when the variable orifice is closed at high speed, one of the auxiliary reaction force chambers is connected to the main reaction force chamber. It incorporates a control valve device that introduces pressure according to the pump pressure and increases the reaction force against the valve piston. However, in this conventionally proposed device, since the differential pressure between both ends of the control valve is reduced at low speeds, the damping effect of the valve is small, and therefore valve vibrations are likely to occur.

An object of the present invention is to provide a power steering device that does not generate self-excited vibrations in the valve piston by providing a fixed orifice in the conventional variable orifice circuit.

To achieve this object, the present invention provides a wormshaft that interlocks with a steering wheel of a vehicle, a power piston that engages with the wormshaft via a steering nut and slides along the wormshaft, and a power piston that slides along the wormshaft. a sector shaft that engages with the rack and is interlocked with a link mechanism for changing the direction of the vehicle; a control valve device that is incorporated in the power piston and is actuated by a valve pin fixed to the steering nut; The control valve device has a valve piston having a pair of main reaction chambers therein, and a pair of auxiliary reaction chambers provided on both sides of the valve piston. In the power steering device, the variable orifice is provided in a power steering device in which the main reaction force chamber is connected to the main reaction force chamber, and the auxiliary reaction force chambers on both sides are connected by a circuit including a variable orifice whose opening degree changes in response to vehicle speed. It has a structure in which a fixed orifice is disposed on the circuit, and when the vehicle is to turn to the right, for example, when the steering wheel is turned to the right, the wormshaft and steering nut simultaneously rotate to the right.

Rotating the steering nut to the right rotates the valve pin integrated with it to the right, which operates the valve piston in the control valve device to the right, supplies hydraulic pressure to the right cylinder chamber, and moves the valve pin along the worm shaft of the power piston to the left. assisting the movement and reducing the movement of the sector shaft that engages the power piston.

On the other hand, oil escapes from the auxiliary reaction force chamber to a circuit with a variable orifice, and if there is no fixed orifice and the diameter of the variable orifice is large, the differential pressure on both sides of the valve piston becomes extremely small, and the resistance force acting on the valve piston increases. Therefore, when vibrations from the steering wheel act on the valve piston, self-excited vibrations are likely to occur.

In the present invention, a fixed orifice is arranged on the circuit, so even if the variable orifice opening is large and oil tries to escape, this oil is regulated by the diameter of the fixed orifice and no excess movement will occur. Since an appropriate pressure difference is provided on both sides of the valve piston, self-excited vibration of the valve piston can be prevented. Although it is possible to limit the opening degree of the variable orifice, in this case the characteristics change depending on the processing accuracy of the variable orifice. The present invention enables the purpose of preventing self-excited vibration to be easily achieved through a simple structure in which a fixed orifice is provided that facilitates machining accuracy.

Embodiments of the present invention will be described below with reference to the drawings.
2 and 3 show different embodiments, and are sectional views taken from A to A in FIG. 1, respectively. In the figure, reference numeral 1 denotes a power steering device, which has a wormshaft 3 rotatably supported at both ends of a housing 2 and a sector shaft 5 that engages with a rack of a power piston 4.

Further, one end of the worm shaft 3 is linked to a steering wheel (not shown), and a sector shaft 5
The worm shaft 3 is connected to a link mechanism (not shown) that changes the direction of the wheels, and the worm shaft 3 is connected to a power piston 4.
Both ends thereof are supported by thrust bearings 6, and are engaged with the wormshaft 3 via a ball and a steering nut 7 that restricts movement in the axial direction. Therefore, the steering nut 7 can only rotate within the power piston 4.

A valve pin 8 is fixed to the steering nut 7, and the tip of the valve pin 8 is connected to a control valve device 9 incorporated in the power piston 4.
is inserted in the center of the The control valve device 9 supplies hydraulic pressure to either a right cylinder chamber 10 or a left cylinder chamber 11, which are partitioned by the power piston 4 in the housing 2, depending on the steering direction, and controls the worm shaft 3 of the power piston 4.
It works to encourage movement along the lines.

That is, the control valve device 9 is housed in a cylinder 12 as shown in FIG. 2, and includes a valve piston 13 having a hole in the center into which the tip of the valve pin 8 is inserted. The valve piston 13 has a pair of bores 14 and 15 with one end open on its left and right sides, and a reaction piston 1 fixed to the power piston 4 is installed in the bores 14 and 15.
6 and 17 are inserted so as to form main reaction force chambers 18 and 19.

Further, on both sides of the cylinder 12, sub-reaction chambers 20 and 21 are formed which have a larger pressure acting area than the main reaction chamber. Further, a pair of annular grooves 22 and 23 are provided in the outer peripheral wall of the valve piston 13, one of the annular grooves 22 being communicated with the right cylinder chamber 10, and the other annular groove 23 being communicated with the left cylinder chamber 11.

Further, pairs of annular grooves 24, 25, 26, 27 are formed on the left and right sides of the inner peripheral wall of the cylinder 12, respectively.
4 and 26 are communicated with an oil pump 28, and grooves 25 and 27 are communicated with an oil reservoir 29.
The main reaction chambers 18 and 19 communicate with the annular grooves 22 and 23 of the valve pin 13 via orifices 30 and 31, and the sub reaction chambers 20 and 21 communicate with the reaction pistons 16 and 1.
It communicates with the auxiliary reaction force chambers 20 and 21 via orifices 32 and 33 provided at 7, respectively.

Further, the auxiliary reaction force chambers 20 and 21 communicate with each other via a circuit 35 incorporating a variable orifice 34. The variable orifice 34 changes its opening degree in response to vehicle speed, and is designed to be open at low speeds and closed at high speeds. 36, 36 are fixed orifices provided on the circuit 35 before and after the variable orifice 34. Although the fixed orifice 36 is provided on both sides of the variable orifice 34, it may be provided on only one side. The opening degree of the upper and lower limits of the variable orifice 34 can be changed in response to the vehicle speed, but if the diameter of the variable orifice 34 exceeds the diameter of the fixed orifice 36, it will not work effectively; Only the following will work: That is, the fixed orifice 36 is responsible for the upper limit, and the variable orifice 34 is responsible for the lower limit.

Next, to explain the operation, when the vehicle is running at low speed, the variable orifice 34 is open, and both auxiliary reaction force chambers 2 are opened.
The pressures at 0 and 21 are equal pressures. Here, when the valve piston 13 moves to the right, the piston 13
The groove 22 is in electrical communication with the groove 24 of the cylinder 12, and the oil valve from the pump 28 is supplied to the right cylinder chamber 10 to assist the movement of the power piston 4.

On the other hand, the groove 23 of the valve piston 13
The left cylinder chamber 11 is electrically connected to the oil reservoir 29 and is not subjected to hydraulic action. Note that the grooves 25 and 26 are closed by the land of the valve piston 13. Also, orifice 30, 32
Pressure from a pump 28 is supplied to the main reaction force chamber 18 and the sub reaction force chamber 20 via.

However, since the auxiliary reaction force chambers 20 and 21 are electrically connected and have approximately equal pressure, a reaction force corresponding to the differential pressure between the main reaction force chambers 18 and 19 acts on the valve piston 13.

On the other hand, at high speed, the variable orifice 3 of the circuit 35
4 is closed, and the auxiliary reaction force chambers 20 and 21 are in a non-conducting relationship. When the valve piston 13 is moved to the right by the valve pin 8 in this state, the hydraulic pressure from the pump 28 is transferred to the right cylinder chamber through the groove 22 as described above.
0, and the left cylinder chamber 11 communicates with the oil reservoir 29 via the groove 23.

In this way, the movement of the power piston 4 can be assisted, but the hydraulic pressure from the pump 28 is applied to the orifice 30,
32 to the main reaction force chamber 18 and the sub-reaction force chamber 20, the sub-reaction force chamber 20 acts on the end face of the valve piston 13 in addition to the reaction force from the main reaction force chamber 18.
The valve piston 13 receives his reaction force. That is, the steering wheel is made heavier at high speeds than at low speeds. Although the above example shows the case where the valve piston 13 is moved to the right, it can be easily understood that the same effect can be obtained even if the valve piston 13 is moved to the left.

FIG. 3 shows another embodiment, in which four annular grooves 24, 25, 26, 27 are formed in the cylinder 12 in FIG.
2 has three annular grooves 37, 38, and 39 formed therein to simplify the structure of the valve. The annular groove 37 communicates with the left cylinder chamber 11 through a circuit 40, and the annular grooves 38 and 39 communicate with the left cylinder chamber 11 through a circuit 40, respectively. 41 and 42 communicate with the right cylinder chamber 10. Further, the annular groove 37 is connected to the main reaction force chamber 19 by the orifice 43, and the annular groove 38 is connected to the main reaction force chamber 19 by the orifice 43, and the annular groove 38 is connected to the main reaction force chamber 19 by the orifice 43.
communicates with the main reaction force chamber 18 through an orifice 44. When the valve piston 13 moves to the right, the annular groove 22 communicating with the pump 28 communicates with the right cylinder chamber 10 via the annular groove 38, and the annular groove 23 communicating with the reservoir 29 communicates with the left cylinder chamber 10 via the annular groove 37. It communicates with the cylinder chamber 11. Also, when the valve piston 13 moves to the left, this communication is reversed. However, the embodiment shown in FIG. 3 is similar to the embodiment shown in FIG. 2 in terms of operation and effect.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a power steering device showing an embodiment of the present invention, and FIGS. 2 and 3 are sectional views taken along line A--A in FIG. 1 showing different embodiments. Explanation of the main parts of the diagram, 1... Power steering device, 3
...wormshaft, 4...power piston,
5... Sector shaft, 7... Steering nut, 8... Valve pin, 9... Control valve device, 10... Right cylinder chamber, 11... Left cylinder chamber, 12... Cylinder, 13... Valve piston, 16 , 17... Reaction piston, 18, 19
...Main reaction force chamber, 20, 21...Sub reaction force chamber, 22,
23, 24, 25, 26, 27... annular groove, 28
...Oil pump, 29 ...Oil reservoir, 3
0, 31... Orifice, 32, 33... Orifice, 34... Variable orifice, 35... Circuit,
36...Fixed orifice.

Claims (1)

[Claims] 1. A wormshaft that interlocks with the steering wheel of the vehicle; a power piston that engages with the wormshaft via a steering nut and slides along the wormshaft; and a power piston that engages with the rack of the power piston and that A sector shaft that interlocks with a link mechanism for changing direction, and a control valve device that is incorporated in the power piston and is actuated by a valve pin fixed to the steering nut, and the control valve device has a pair of control valve devices inside it. a valve piston having a main reaction force chamber, and a pair of sub-reaction force chambers provided on both sides of the valve piston, the sub-reaction force chambers communicating with the main reaction force chamber via an orifice, and In a power steering device in which the auxiliary reaction force chambers on both sides are connected by a circuit provided with a variable orifice whose opening degree changes in response to vehicle speed, a fixed orifice is disposed on the circuit provided with the variable orifice. A power steering device characterized by: