SE439910B - HYDRAULIC AID CONTROL DEVICE - Google Patents

Description

15 20 25 30 35 7810507 ~ 9 the following claims.

Three embodiments of the invention are described in the following with reference to the accompanying drawings, in which Fig. 1 shows a cross section through a rotary piston type control valve, Fig. 2 shows a longitudinal section through an axial slide type control valve and Fig. 3 shows a cross section through a control valve of rotary wear type.

The control valve 1 shown in Fig. 1 contains a valve body 2 and two control valve pistons 4a, 4b arranged in the oil supply space 3 transversely to and next to the longitudinal axis, each having its own bore 5 and 5, respectively. 6, in which engages a pin (not shown), which serves in a known manner for operating the control valve pistons 4a and 4b. The valve body 2 has a bore 7, through which a torsion bar transmits a rotational movement from a control spindle (not shown) via a gear to a rack. over this mechanical connection from a steering wheel to the steered wheels, the vehicle can also be steered manually manually in the event of a failure of the hydraulics.

Via a line 8 the working medium is fed to the control valve 1. The working medium flows over an inlet control edge 9 in the control valve piston 4a and an inlet control edge 9 'in the control valve piston 4b and over lines 10 and 10' to the working spaces 11 and 11 'in an uncompensated working cylinder 12. Via branch points 13 resp. 13 'and return flow guide edges 14 resp. 14 'in the control valve piston 4b resp. 4a, the working medium flows through bores 15a in the valve body 2 to the return line 15.

In the case of functionally symmetrically arranged guide edges and oil lines, equal pressure is set in the working spaces 11 and 11 'of the working cylinder 12, while at the branch points 13 and 13' there is also equal pressure. Through a choke 16 between the branch point 13 and the return flow edge 14, the working medium is dammed in front of the choke 16 and thus the pressure in the working space 11 is increased by the smaller area in relation to the working space 11 '. Before and after the throttle 16, a pressure difference depending on the flow of the working medium sets.

The pressure after the throttle 16 is determined by the pressure prevailing in the return line common to both workrooms, i.e. that the pressure after the throttling roughly corresponds to the pressure in the working space 11 '. Due to the now asymmetrical resistances in lines 10 and 10 ', the flow in line 10 is less than in line 10'. Due to the decreasing flow in the line 10, the effect of the choke 16 is limited. After reaching an optimum, despite the reduction of the cross-section of the choke 16, the pressure difference before and after the choke 16 can no longer be significantly increased.

A second choke 16 ', of the same size as the choke 16, in the conduit 10' between the supply guide edge 9 'and the branch 13' has ensured an even flow distribution of the working medium and the pressure-increasing effect of the choke 16 'has no influence on the working space 11' with the larger area.

By changing the size of the two throttles 16 and 16 ', each pressure difference can be established in the cylinder chambers at the neutral position of the control valve 1, so that no force acts on the working piston 17.

The throttles 16 and 16 'can be provided, for example, by narrowing the conduits 10 and 10'.

Fig. 2 shows another embodiment of the invention, in which a control valve is designed as an axial slide.

In this control valve, the parts corresponding to parts in the exemplary embodiment according to Fig. 1 have been provided with the same reference numerals.

A rotation of the knob is transmitted to the control valve piston 4, which is axially movable.

The throttles 16 and 16 'necessary for the pressure increase are arranged partly at the work space 11 with the smaller area ._ _., __._..._............_..... ..-_.......___. 7 15 20 25 7810507- * 9 assigned the return flow guide edge 14 and partly at the working space 11 'with the larger area assigned the inlet guide edge 9' between the inner diameter of the control valve 1 and the control valve piston 4.

Fig. 3 shows a further embodiment of the invention, in which a control valve is designed as a rotary slide.

The inlet of the working medium takes place via lines 8,8a, 8b, 8c and three afterwardly arranged inlet guide edges 9 to the workroom 11 with a smaller area, resp. over three inlet guide edges 9 'to the workroom 11' with the larger area.

The return flow of the working medium takes place over three return flow guide edges 14, three return flow guide edges 14 'and three radial bores 15a, 15b and 150 in the control valve piston 4 to the return line 15.

The pressure difference in the two working spaces 11 and 11 'is effected by three throttles 16, which act immediately after the three return flow guide edges 14, and three throttles 16', which act immediately before the three inlet guide edges 9 '.

In the control valves according to the invention, the throttles 16 and 16 'can be annular, faceted or surface-shaped through projections in the control valve pistons 4 or in the surface of the control valve housing.

Claims (6)

7810507-9 P A T E N T K R Å V Hydraulic auxiliary power steering device, in particular for motor vehicles, with a working cylinder (12), the piston (17) of which has different large active surfaces and which is connected via working lines (l0, l0 ') to a control valve, which can be actuated of rotational movements of a steering wheel and has an open central position and has a chamber connected to an inlet (8) and a return line (15), the two working spaces (ll, l1 ') of the working cylinder in the neutral position of the valve being simultaneously connected to these both chambers and in a line section serving exclusively for pressure medium return from the working space (ll) serving the less active surface, there is built-in a throttle (16) which is unchanged by the movement of the control valve to its cross-section, characterized in that a further cross-section a final throttle (16 ') is arranged between the chamber connected to the supply line (8) and the line (10') leading to the working space (11 ') with the larger operative surface. 2. Control device according to l, characterized in that the throttles (l6, l6 ') are designed as constrictions of the lines (l0, l0'). Control device according to claim 1, characterized in that the throttles (16, 16 ') are formed by cooperation between corresponding recesses and cylindrical wall parts in the control valve piston arranged at the control valve piston (4) or pistons (4a, 4b). or the pistons receiving the bore. Control device according to Claim 1, characterized in that the throttles (16, 16 ') are formed by the interaction between the corresponding recesses and cylindrical sections of the control valve piston worked into the surface (16) of the control valve piston receiving the bore. 7810507-9 B Control device according to Claim 3 or 4, characterized in that the throttles (16, 16 ') are annular or surface-shaped. Control device according to one of the preceding claims, characterized in that the throttles (16, 16 ') are made with an equally free cross-section.