JPS6042066B2 - power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that compensates for the amount of play even if a group of gears constituting a differential mechanism is worn out or damaged, thereby maintaining a constant input/output ratio.

The applicant of this application has already developed and applied for a power steering device equipped with a differential gear mechanism (Japanese Patent Application No. 48-11
552 (Special Publication No. 56-45824), Patent Application No. 47-
127974 (Special Publication No. 56-20226)).

As disclosed in these documents, the effect of adopting a differential gear mechanism in a power steering device is significant, and steering stability has been dramatically improved. However, in a differential gear mechanism composed of a large number of gear groups, each meshing part tends to wear out and the fitting parts become loose due to long-term use, and so-called play occurs in the mechanism itself. In addition, an initial reaction force due to a spring and a hydraulic reaction force are introduced into the control valve operated by the differential gear mechanism, and all the reaction forces generated here reverse the wear of the differential gear mechanism. is promoting.
The occurrence of play in the differential gear mechanism is undesirable from the viewpoint of steering stability, and may cause a decrease in straight-line performance, especially at high speeds, leading to steering errors. The present invention was proposed to overcome this problem, and aims to absorb play even if it occurs in the differential gear mechanism and maintain stable steering characteristics.

A detailed explanation will be given below based on the drawings. Reference numeral 1 indicates a cylinder housing, 2 indicates a differential mechanism housing, and 3 indicates an input shaft which is directly connected to a handle (not shown). 4 is a sector gear, which is connected to the pitman arm of the steering (not shown), and ultimately controls the rotation of the input shaft 3 (
The sector gear 4 rotates (output) in proportion to the input (input) and steers the steering wheels.

A piston 5 that meshes with a sector gear 4 is disposed within the cylinder housing 1, and defines working chambers A and B on both sides. The cylindrical screw shaft 6 is attached to this piston 5.
The torsion bar 9 is screwed into the inner peripheral surface of the
It is connected to the upper input shaft 3 via. The differential gear mechanism C includes sun gears 11a and 11b symmetrically carved on the peripheral surfaces of the input shaft 3 and screw shaft 6, sandwiching a rotatable disk 10, and a plurality of planet gears 12a and 11b meshing with the sun gears 11a and 11b, respectively. 12b
are arranged symmetrically on both sides of the disk 10 with pins 13.

Each planet gear 12a, 12b is similarly meshed with a ring gear 14a, 14b, one of which is rotatably supported is connected to a spool 16 of a control valve 17 via a rod 15, and the other ring gear 14 is connected to a spool 16 of a control valve 17 via a rod 15.
b is fixed to the differential mechanism housing 2. As the spool 16 moves, the control valve 17 appropriately connects the annular boats P, T, M, and selectively supplies pressure fluid to the working chamber A or B defined within the cylinder housing 1. The spool 16 of the control valve 17 is configured to move in the tangential direction of rotation of the ring gear 14a, and the rod 15 is moved by the left and right rotation of the ring gear 14a.
slide from side to side. Incidentally, the ring gear 14b may be rotatably arranged without being fixed and connected to the valve spool 16, and the ring gear 14a on the other input shaft side may be on the fixed side, or the ring gear 14b may be connected to a vehicle speed sensor or steering angle. A correction input method that controls rotation based on a sensor may also be used, and the spool valve 17
A spring reaction force or a hydraulic reaction force may be applied inside the vehicle to maintain appropriate responsiveness and handling sensation. Next, to explain the operation, first, the steering wheel is turned to rotate the input shaft 3.

Since the sector gear 4 connected to the steered wheel before turning is in a fixed state due to ground resistance, the piston 5 and screw shaft 6 that mesh with it are stationary, and one sun gear 11b is also fixed like the ring gear 14b. ing. Therefore, due to the rotation of the sun gear 11a of the input shaft 3, the planet gear 12a does not revolve but rotates, causing the ring gear 14a to rotate and the spool 16 to move.
The switched control valve 17 delivers pressurized fluid from the hydraulic pump to one of the working chambers A or B defined within the piston 5. At the same time, the rotational force (steering force) of the input shaft 3 is transmitted to the other screw shaft 6 while twisting the torsion bar 9.
1b starts rotating at the same rotational speed as sun gear 11a with a slight phase difference. Therefore, the planet gear 12a, which was only performing automatic movement, rotates and revolves in parallel, like the other planet gears 12b, and stops the ring gear 14a. In other words, the control valve 17 is maintained in the switched state and continues to supply pressurized fluid into the working chamber until the input shaft 3 stops. As the screw shaft 6 rotates, the piston 5, which is engaged with the screw shaft 6, moves by an amount proportional to the pitch, but this movement is performed smoothly by the pressure fluid supplied to the working chamber A or B, and the operator The sector gear 4 can be rotated with extremely little force, and the steered wheels can be turned. While the input shaft 3 is rotating, the piston 5 is moved by the working fluid by an amount proportional to this pitch and follows. When the input shaft 3 is stopped, the sun gear 11a is also stopped, but the other sun gear 11b rotates by an amount equivalent to the amount of twist imparted to the torsion bar 9 and then stops.

During this short period of time until it stops, the planet gears 12a, 1
Since the ring gear 2b continues to rotate, the ring gear 14a, which has been stopped until now, rotates in the opposite direction and stops at the initial position. In other words, the ring gear 14a rotates by the amount of twist of the torsion bar 9 applied when the input shaft 3 rotates, and the spool 16 also moves to the neutral position accordingly. In addition, if the pressure of the working fluid decreases due to a failure in the hydraulic power source, etc., and the driving force of the power cylinder is not generated even if the control valve is switched, the rotational force input to the input shaft 3 may directly twist the torsion bar 9. To rotate the screw shaft 6,
Even in such a case, the steered wheels can be turned, and from the point of view of steering stability, a so-called fail-save function can be achieved. This means that it is only necessary to have the mechanical strength necessary to switch the valve, and therefore each gear can be made small as a so-called signal transmission member.

As described above, the present invention connects the screw shaft 6 screwed to the piston 5 to the input shaft 3 via the torsion bar 9, and utilizes the phase difference between the two to create a differential gear mechanism consisting of two rows of planetary gear trains. C operates the control valve 17 that supplies pressure fluid to the working chambers partitioned on both sides of the piston 5, and transmits the rotation of the input shaft 3 to the sector gear 4 regardless of the play of the differential gear mechanism C. Therefore, planet gears 12a, 12b and ring gear 1
Even if play occurs due to wear in parts 4a, 14b, etc., it will not affect the relationship between the input shaft and output shaft, and the handling stability and steering characteristics will not change even after long-term use, especially when driving straight at high speeds. Can guarantee sex. Further, the reaction force within the control valve 17 can be compensated for by the torsion bar 9 or the like, which has the effect of reducing the load on the power transmission of the differential gear mechanism C.

[Brief explanation of drawings]

The drawings show an example of the implementation of the present invention, and FIG. 1 is a longitudinal sectional front view, FIG.
The figure is a sectional view taken along the line ■-■ as above. C... Differential gear mechanism, 3... Input shaft, 5... Piston, 6...
Screw shaft, 17... Control valve.

Claims (1)

[Claims] 1. A screw shaft that is screwed into the piston of the power cylinder and an input shaft that is an input shaft are connected via a torsion bar, and a sun gear is formed on the outer periphery of each of the input shaft and the screw shaft,
Planet gears that mesh with these sun gears are provided, and these planet gears are mounted and supported on both sides of a disk that is rotatably arranged around the input shaft, and ring gears are meshed with each of the outer sides of the disk, so that one ring gear is fixed and the other The ring gear is rotatably arranged and constitutes a differential gear mechanism for feedback control of a valve consisting of two rows of planetary gear trains connected with a torsion bar, and the movable ring gear is arranged in a direction tangential to the rotation of the control valve. The invention is characterized in that the pressure fluid can be selectively supplied to working chambers defined on both sides of the piston of the power cylinder in conjunction with switching of the control valve by rotational displacement of the input shaft. Power steering device.