DK159103B - CONTROL DEVICE FOR TWO THAN EACH OF TWO VENTILATIONS FROM A HIGH PRESSURE PUMP HYDRAULIC DEVICE - Google Patents

Description

DK 159103B

The present invention relates to a control device for two hydraulic devices, supplied by one of two branches of a high-pressure pump, and of the kind specified in the preamble of claim 1.

Such a control device is known from DE-OS 32 14 468. The flow of pressure medium from the pump is divided by means of a flow dividing valve into a working flow for a hydrostatic control device for the vehicle and in a working flow for another working device. To the supply line from the pump is connected a control line containing a measuring aperture and which leads a relatively small pilot flow to the control valve. The small pilot flow in the control valve neutral position can flow back to the oil tank and serves to upregulate a working pressure at the beginning of a control movement. The control valve is so designed that, in the event of an up-regulation of the working pressure, it gradually cuts off the pilot flow by a displacement of the control valve.

As the differential pressure at the measuring aperture according to the German "Offenlegungsschrift" changes in line with the pressure required at any given time, a constant pilot flow cannot be maintained in the control line. In addition, via the control conductor, a higher working pressure is usually available, corresponding to the pressure in the second hydraulic circuit. The control valve must therefore down-regulate this right pressure by means of a control movement with relatively large piston movement.

On the basis of this known control device, it is the object of the invention to keep the pilot flow constant at the control valve and to avoid a pressure load on the control device from the higher pressure of the working hydraulic system without incurring additional manufacturing costs.

This task is solved by the fact that the control device is peculiar to that of the characterizing part of claim 1.

According to the invention, the measuring aperture in the flow dividing valve is arranged in the flow direction following a control edge for a constant flow in the pilot flow line. The connection of the current branch of the working current to the control device can 2

DK 159103 B

thus made between said guide edge and the measuring aperture. This arrangement has the advantage that the higher pressure in the current branch of the other working device (the lifting hydraulic lick) can not affect the absoil expression prevailing on the measuring aperture. As mentioned, as the connection of the current branch of the control device's workflow occurs between the control edge and the measuring aperture, the working pressure of the second working device also cannot affect the working pressure of the current branch of the control device.

Further details of the invention are explained below by means of the drawings. In the drawing:

FIG. 1 shows an oil diagram of the control device according to the invention with a power steering as the first hydraulic device and a working hydraulic as the second device with control valves shown in neutral.

FIG. 2 shows the oil diagram of FIG. 1 with actuated control device.

FIG. 3 shows the structure of the device according to FIG. 1 and 2 are schematically shown flow valve.

20 In the control device according to FIG. 1, there is shown an oil container 1 from which a high-pressure pump 2 sucks pressure oil. The high-pressure pump 2 is constantly driven by means of a drive motor and therefore provides a certain amount of pressure oil. A high flow pump 2 is connected to the high pressure pump 3. The flow valve 3 has the task of limiting the pressure oil flow from the pump 2 in a substantially constant small flow stream 10 in a pilot flow line 4. This partial flow T starts from the oil flow supplied to the flow valve 3. that in a current branch 5, a corresponding residual current R. flows 30. The pilot current line 4 is connected to a control valve 6. The control valve 6 controls a first hydraulic device 7 associated with a control device with a working piston 8. The residual current R is fed to an operating valve 10 which controls another hydraulic device 11, for example 35 a lifting hydraulic. The control valve 10 is drawn in neutral position so that the applied pressure oil (residual flow R) can flow away via a return line 9 to the oil container 1.

DK 159103B

3

Between the current branch 5 and the return line 9 is placed a pressure limiting valve 12 which in the working position of the control valve 10 limits the working pressure to a maximum value. Commonly known building elements are used as control valve 10 and hydraulic device 5 11, so that a detailed description of the working method of these building elements is superfluous. The second hydraulic device 11 is dimensioned so that at its greatest required working speed it just comes out with the full residual flow R. In the present case, for example, the subcurrent T in the pilot flow line 4 can be 5 l / min and the residual current R in the current branch 5 is max. 145 rpm

The partial flow T supplied from the flow dividing valve 3 serves as pilot flow for the control valve 6. In the drawn position of the control valve 6, the partial flow T or the pilot flow flows via a control channel 13 and a return line 14 back to the oil container 1. Between the pilot flow line 4 and the return line 14 a pressure limiting valve 15 which limits the working pressure of the first hydraulic device 7 (the control device 20) to a maximum value. A dosing pump 17 and the hydraulic device 7 are connected to the displaceable control valve 16 which is displaceable by means of a steering wheel 16. The dosing device 17 is immediately connected to the steering wheel 16, which with a pivotal movement ensures that the hydraulic device 7 is always assigned pressure oil from the right pressure side to achieve the desired control result. In the neutral position shown in the control valve 6, the connections from the metering pump 17 and the hydraulic device 7 are blocked.

According to the invention, between a measuring aperture 19 located after a control edge 18 and a valve piston 20 in the flow dividing valve 3, there is connected a current branch 21 for the working flow to the control device. X shown in FIG. 1 shown in neutral position of the control valve 6, the current branch is shut off.

35 The operation will be described in more detail below with the aid of FIG. 2. This shows the control valve 6 in an outer position. The outlined position appears due to a 4

DK 159103 B

turning the steering wheel 16 at which the control valve 6 is displaced in known manner. By displacing the control valve 6 out of the neutral position, the flow cross-section of the control channel 13 is reduced to zero. The subcurrent T is throttled and 5 obtains an increased pressure in the pilot flow line 4 and thus also in the branch branch 21. A control channel 22 in the control valve 6 conducts the working stream in the current branches 21 to the metering pump 17. Through this control channel 22, as much pressure oil as the metering pump 17 can flow. record. The metering pump 10 conducts the applied pressure oil via an additional control channel 23 to the left side of the working piston 8. This causes the working piston 8 to shift to the right. From the right side of the working piston 8, the pressure oil flows via a control channel 24 to the return line 14 and thence to the oil container 1. 15, when the steering wheel is operated at the fastest speed (eg with parking at approximately idle speed}, an oil flow greater than the with the pilot current diminished transport current, the total pump current in the current branch A can flow to the metering pump, i.e. the pilot current 20 in the pilot current line 4 becomes zero.

In the embodiment shown in FIG. 2, at the same time, when the pressure valve 10 is removed from the second hydraulic device 11, the control valve 6 is drawn at the same time as residual current R can be supplied only a maximum of only 25 as the maximum output of the high pressure pump 2 minus the working flow A and the sub-flow T. for example, pump 2 delivers a maximum of 150 l / min. The workflow A is a maximum of 45 l / min. and the partial flow T 5 1 / min. Thus, a residual current R of 100 l / min remains in the current branch 5. With this residual current R, the second hydraulic device 11 must cope in the considered working phase. However, the hydraulic device 11 never gets smaller either, since the maximum consumption of the control device is determined by the maximum throughput through the metering pump 17. If the steering wheel 16 is rotated more slowly, 35 also in the metering pump 17 will have a correspondingly smaller oil flow which affects the workflow A. This does not apply to the partial flow. 10, since this is essentially held constant

DK 159103 B

5 of the flow valve 3. As a rule, the control operation takes place with diminished workflows, so that the second hydraulic device 11 can only cope with a substantially degraded oil supply in extreme operating phases of the control device.

In the arrangement according to the invention of the measuring aperture 19 after the control edge 18 between the pump 2 and the pilot flow line 4, ie. at the constant current output of the flow dividing valve 3, the operating pressure in the hydraulic branch 5 of the second hydraulic device 11 does not affect the absolute pressure prevailing at the measuring aperture 19. Also, since the current branch 21 of the operating flow of the control device (hydraulic device 7) is connected between the control edge 18 and the measuring aperture 19, the working pressure in the current branch 5 cannot influence the working pressure of the current branch 21. Due to the working flow A branched in front of the measuring aperture 19; 3 immediately after-regulate a lack of flow in front of the measuring aperture, thus keeping the floating partial flow T constant in the pilot flow line 4. By means of the described joint, the control device without the use of additional valve devices is protected against high operating pressures from, for example, a lifting device. The exact structure of the flow dividing valve is shown in more detail in FIG. 3. In a housing 25 a valve piston loaded with a spring 26 is guided 20. The valve piston has guide edges 18 and 28. Valve piston 20 regulates in known manner with the guide edge 18 when the pressure in the current branch 5 is greater than in the wire branch 21 or In the pilot flow line 4. Conversely, the control edge 28 regulates at a lower pressure in the current branch 5 than in the current branch 21 or in the pilot flow line 30 4. The measuring aperture 19 is located in the flow direction after the control edge 18. Between the measuring aperture 19 and the control edge 18 a current branch 21 is connected. the metering aperture 19 is supplied via a damping bore 27 through an opposite end face 29 of the valve piston 20 35, and the pressure after the aperture acts on an end face 30 facing the spring. Differential pressure on the measuring aperture 6

DK 159103 B

19 is thus a measure of the position of the valve piston 20.

This, by means of its guide edges 18 and 28, keeps the differential pressure above the measuring aperture 19 constant. A pressure oil flow flowing across the branch branch 21 is missing at the measuring aperture 5 19, thereby reducing the differential pressure at the measuring aperture.

The valve piston 29 is thereby shifted to the right against the force of the spring 26. By opening the guide edge 18 and simultaneously closing the guide edge 28, the pressure oil flow over the control edge 18 is increased, so that, regardless of the size of 10, a working current A in the branch line 21 is always a constant partial flow T in the pilot power line 4.

If the pilot flow line 4 or the branch line 21 is pressure-free (the control valve 6 in neutral position) and at the same time the operating pressure rises in the current branch 5, the control edge 18 lowers the oil-15 flow so much that an increase of the sub-flow T is prevented. Thus, independent of the pressure at the current branch 5, the pressure at the differential aperture 19 in the pilot current line 4 is always available, independent of the pressure at the current branch 5.

Claims (1)

DK 159103 B Control device for two via each of two current branches 5 from a high-pressure pumped hydraulic device, in which control device: - the first hydraulic device is a hydrostatic steering gear for an automobile, 10. a current branch for the workflow to the hydrostatic steering gear exits from a power split valve and is connected to the control valve, - the second power branch also exits from the power split valve and carries a residual working current to another working device, e.g., a lifting device. - a pilot flow line for regulating the working pressure is connected to the control valve via a measuring aperture, characterized in that - the measuring aperture (19) is located in the flow direction 20 after a control edge (18) in the flow dividing valve (3) for a constant flow in the pilot flow line (4 ), and - the connection of the current branch (21) to the working current of the control device is made between the control edge (18) and the measuring aperture (19) of the flow dividing valve. 25 ** 30