JP2511502B2 - Fluid pressure steering mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL FIELD OF APPLICATION The present invention relates to a pump connected to a pump via a pump conduit.
Connected to a steering motor via one motor conduit and connected to a vessel via a vessel conduit, actuating a manual steering wheel or the like releases the supply path via the metering device and at least one supply throttle and returns path. The closing direction by the pressure of a throttle valve, in particular a priority valve, which is connected to the upstream of the pump conduit and which is connected to the end of the pump conduit via the inlet pressure conduit Steering mechanism constituted by a slide loaded in the direction of pressure and released in the release direction by the pressure of a second pressure chamber connected to the load pressure detection region behind the supply throttle via a spring and a load pressure conduit .

(Prior Art) Such a fluid pressure steering mechanism is known.

(Problems to be Solved by the Invention) It is known that steering difficulty occurs during overrun operation. Such an overrun operation occurs when an external force (so-called negative steering force) acts on the steered wheels and is adjusted at a speed faster than the steering speed of the steering device. Such a difficulty of steering is particularly remarkable in a coupled vehicle because not only wheels but also parts of a vehicle having a relatively large mass rotate during steering.
Such rotation of the wheels and parts of the vehicle may generate a large acceleration force as negative steering.

(Means for Solving the Problem) An object of the present invention is to provide a fluid pressure steering mechanism of the type described above, which can substantially avoid the difficulty of steering during such an overrun operation. It is a thing.

This object of the invention is solved by the fact that the inlet pressure conduit is constituted by the throttle position and is connected to the supply side of the motor conduit via a bridge conduit constituted by a pressure reducing valve on the side of the throttle position remote from the pump conduit. It

With the help of the pressure reducing valve, it is ensured that the pressure on the supply side of the motor conduit does not drop below the value predetermined by this valve. If the steering motor piston is moved by the effect of the negative steering force faster than the pressure fluid is replenished by the controller,
If this results in a lower pressure on the supply side of the motor conduit, replenishment is bypassed by the controller. This replenishment is done from the pressure side, ie without the aid of a vacuum. As a result, the load pressure drawn in the detection region does not drop to a value at which the throttle or priority valve no longer functions correctly. At the same time, a pressure drop occurs at the throttle position. The pressure in the first control chamber of the throttle valve is therefore reduced compared to the pressure at the outlet of the throttle valve. This compensates for the drop in load pressure, so that the throttle valve
As will be described in more detail below, it operates substantially normally.

A particularly simple construction results if the bridge conduit is connected to both motor conduits via individual check valves which open to the motor conduit. Such check valves are already known for the case where replenishment is done by suction. However, in the present case, the replenishment is done from the pressure side and therefore more aggressively and faster.

The check valve must be spring biased. This ensures that the check valve is closed in the neutral position of the control device, even under vibration. Therefore, the two motor pressure chambers are not inadvertently interconnected.

The output pressure of the pressure reducing valve need not be a high value to achieve the desired result. Particularly, it is desirable that the pressure reducing valve is set to an outlet pressure lower than the pressure corresponding to the spring provided in the throttle valve.

In many cases, the flow resistance in the return path is due to the steering motor piston reaching its end position.
It is sufficient to ensure that the bridge conduit is not connected via the check valve to the return path of the motor conduit. If this flow resistance is not sufficient, it is desirable to provide an overpressure valve in the vessel conduit with the inlet pressure set to a value higher than the outlet pressure of the pressure reducing valve.

In particular, the inlet pressure of the overpressure valve is in the region of pressure corresponding to the spring provided on the throttle valve.

The throttling location is preferably a diaphragm with holes having a diameter of 1.5 to 2 mm. Therefore, this is a very simple part.

Embodiments Embodiments of the present invention will be described in more detail with reference to the drawings.

The control device 1 comprises a pump connection P, two motor connections L and R, a vessel connection T and a load pressure connection LS. The pump connection P is in communication with the pump 3 and the end 2 of the pump conduit 5 constituted by a priority valve operating as a throttle valve 4.
Connected with. The two motor connections L and R are connected via motor connections 6 and 7 to the respective motor chamber 8 or 9 of the steering motor 10, the piston 11 of which is the vehicle part to be steered by the piston rod 12. To operate. The vessel connection T is connected via a vessel conduit 13 to a supply vessel 14 for pressure fluid. The vessel conduit 13 has an overpressure valve which holds the inlet pressure at a predetermined value, for example 5 bar.

When the manual steering wheel (handle) 17 is operated, the control device 1 in FIG. 1 releases the supply passage 18 and the return passage 19 leading to the motor chamber 8. A metering motor 20 that determines the passing flow rate is arranged in the supply path 18. The four throttles A1, A2, A3, and A4 in the supply path 18 and the throttle A5 in the return path 19 are manual steering wheels.
17 and metering motor. FIG. 2 shows a closed center non-reactive steering system in which all throttles are closed in the neutral position of the control unit 1. The throttling operation is performed in the supply path and the return path, the motor connecting portions L and R are connected to the pump connecting portion B and the vessel connecting portion T by the rotation direction of the manual steering wheel 17, and the flow direction of the fluid flowing to the steering motor 10 is determined. Also, multiple throttles are required because they must also be generated by the metering motor 20 based on the direction of rotation. Between the throttles A3 and A4 is a load pressure detection area 21 connected to the load pressure connection LS. The throttle valve 4 is a priority valve, which, if necessary, directs the quantity delivered by the pump 3 by means of the end 2 to the control device and the rest by the second conduit 22 to other consumer elements. Therefore, two counter-acting diaphragm positions 23 and 24 are provided, which are controlled by one slide 25. Regarding the throttle position 23, the slide is the first pressure chamber.
It is loaded in the closing direction by the pressure of 26 and is loaded in the opening direction by the pressure of the pretensioned spring 27 and the second pressure chamber 28. The applied tension of the spring 27 corresponds to a pressure of, for example, 4 to 7 bar. The first pressure chamber 26 is connected to the end 2 of the pump conduit via an inlet pressure conduit 29. Second pressure chamber
28 is connected to the pressure detection connection LS via the pressure detection conduit 30.

The inlet pressure conduit 29 is constituted by the throttle position 31. The latter is constituted by a diaphragm having holes with a diameter of, for example, 1.5 to 2 mm. Entrance conduit 29
On the side of the throttle position far from the pump conduit
It is connected to a point 34 via a bridge conduit 33 with 32, which is connected to the motor conduit 6 via a check valve 35 biased by a first spring and biased by a second spring. It is connected to the motor conduit 7 via a check valve 36. Pressure reducing valve 32
Holds its outlet pressure at a predetermined value, for example 3 to 4 bar.

When the manual steering wheel 17 is actuated during normal steering operation, the pressure fluid is steered from the pump through the throttle valve 23 of the priority valve 4, through the supply line 18 of the controller 1 and through the motor conduit 6. It flows into the motor chamber 8 of the motor 10. It is from the motor chamber 9, the motor conduit 7, the return path 10 of the control device 1.
And via the vessel conduit 13. When the manual steering wheel is rotated in the opposite direction, the motor chamber 9 is supplied with pressurized fluid. During normal steering operation, the bridge conduit 33 and throttle position 31 are
It does not work because the outlet pressure of 32 is lower than the pressure of the supply side motor conduit and the pressure of the return side motor conduit.

First, the overrun operation that occurs in the absence of the throttle position 31, the pressure reducing valve 32 and the bridge conduit 33 will be examined. When the pressurized fluid is supplied to the motor 10 at a certain speed through the motor conduit 6, but the piston rod 12 is affected by an external force such that the piston 11 moves at a speed faster than the speed corresponding to the supply of the fluid. , The pressure in the motor conduit drops, and in extreme cases even vacuum. A corresponding decrease occurs in the load pressure of the pressure chamber 28 of the throttle valve 4, which causes the throttle position 23 to move towards the closed position. This reduces the flow to the steering motor 10, which intensifies the overrun condition. Since the metering motor 20 measures a lower flow rate, the valve slide in the controller 1 follows the metering motor 20 at a slower speed,
Therefore, all throttles, including the return throttle A5, move to their maximum open position. This means that the fluid from the motor chamber 9 on the return side will be drained to a lower pressure and thus the overrun condition will be worse.

(Effects of the Invention) In contrast to this, in the present invention, another feature is added, and the following effects occur. As long as the negative steering force is very low and the pressure in the motor conduit 6 does not drop below the outlet pressure of the pressure reducing valve 32, the steering system will operate as usual. However, if the pressure in the supply side motor conduit 6 drops below the value at this outlet, part of the flow will go through the bridge conduit 33 to the steering motor 10 as the pressure reducing valve 32 and the check valve 35 open. Flow to. The pressure in the motor chamber 8 therefore does not drop below this minimum pressure. At the same time, the load pressure does not drop below the values mentioned above. Therefore, the pressure in the pressure chamber 28 of the throttle valve 4 is artificially maintained. At the same time, the pressure in the pressure chamber 26 is artificially reduced, because a flow through the throttle position 31 causes a pressure drop compared to the pressure at the pump connection B. Slide 25 by both features
Does not move to the closed position of the diaphragm position 23 and holds the normal adjustment position. This in turn causes the control device 1 to be supplied with pressurized fluid without any additional throttling losses, and a corresponding amount of flow is also generated in the steering motor 10 via the metering motor 20. Throttle A of control device 1
A5 to A5 do not have to move to their maximum open position, since the metering motor can follow the rotational speed of the steering wheel 17. Therefore, the feedback throttle A5
Has a relatively high resistance, so that the effect of the load force on the displacement rate is smaller. In short, overrun conditions are substantially reduced. The disadvantageous consequences associated therewith no longer occur, and in particular the steering difficulties do not occur. It is possible to bear the fact that the quantity replenished via the bridge conduit 33 is no longer measured by the metering motor 20.

Of course, such a condition would also be obtained if the motor conduit 7 served for the supply flow and the motor conduit 6 served for the return flow.

Many variations can be made from the described embodiments without departing from the basic concept of the invention. For example, if the load pressure is withdrawn in the control device and acts on the throttle valve in the opposite direction to the inlet pressure, a different known construction of control device 1 and throttle valve 4 can be used.

The additional parts provided according to the invention take up very little space. Therefore, they can be housed in the valve block of the steering device, preferably the valve block already provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a steering mechanism according to the present invention. FIG. 2 is a diagram showing the control device of FIG. FIG. 3 is a sectional view of the throttle valve of FIG. 1 ... Control device, 4 ... Throttle valve, 6, 7 ... Motor conduit, 13 ... Vessel conduit, 15 ... Overpressure valve, 17 ... Steering wheel, 29 ... Inlet pressure conduit, 31 ... Throttle Position, 32 ... Pressure reducing valve, 33 ... Bridge conduit, 35, 36 ... Check valve, A1, A2, A3, A4, A5 ... Throttle.

Claims (7)

(57) [Claims] 1. Connected to a pump via a pump conduit, 2
Connected to a steering motor via one motor conduit and connected to a vessel via a vessel conduit, actuating a manual steering wheel or the like releases the supply path via the metering device and at least one supply throttle and returns path. The closing direction by the pressure of the first pressure chamber connected to the end of the pump conduit via the throttle valve and the input pressure conduit, which is composed of a priority valve connected to the upstream of the pump conduit Steering mechanism constituted by a slide loaded in the direction of release and loaded in the release direction by the pressure of a second pressure chamber connected to the load pressure detection region behind the supply throttle via a spring and a load pressure conduit At the inlet pressure conduit (29)
Is connected by a throttle position (31) to the supply side of the motor conduit (6, 7) via a bridge conduit (33) constituted by a pressure reducing valve (32) on the side of the throttle position remote from the pump conduit. A fluid pressure steering mechanism characterized in that 2. The bridge conduit (33) is connected to both motor conduits (6, 7) via respective check valves (35, 36) opening towards the motor conduit. The fluid pressure steering mechanism according to claim 1. 3. The fluid pressure steering mechanism according to claim 2, wherein the check valves (35, 36) are biased by springs. 4. The pressure reducing valve 32 is set to an outlet pressure lower than a pressure corresponding to a spring provided in the throttle valve (4).
A fluid pressure steering mechanism as described. 5. The overpressure valve (15) provided in the vessel conduit (13) has an inlet pressure set to a value higher than the outlet pressure of the pressure reducing valve 32.
The fluid pressure steering mechanism according to any one of claims 1 to 4. 6. The fluid pressure steering mechanism according to claim 5, wherein the inlet pressure of the overpressure valve (15) is in a pressure range corresponding to a spring provided in the throttle valve (4). 7. The diaphragm position (31) is a diaphragm having a hole with a diameter of 1.5 to 2 mm.
7. The fluid pressure steering mechanism according to any one of 6 to 6.