DE3422164A1 - Hydraulic system with two consumers of hydraulic energy - Google Patents

Abstract

Hydraulic system with a pressure-medium source 3 and at least two consumers 13, 28 attached to the pressure-medium source 3, in which arrangement the sum of the flows received by the consumers 13, 28 can be greater than the maximum delivery flow of the pressure-medium source 3, one 13 of the consumers 13, 28 being preferred and in each case receiving the full requisite flow by means of a special device, and a second consumer 28 being attached to a directional control valve 18 activated by means of control pressure, where, in order to manage with a small inexpensive directional control valve, the directional control valve 18, in the device which brings about the preference for the consumer 13, is connected between a low-pressure-medium source 21 and the control pressure space of an auxiliary directional control valve 25 hydraulically controlled against spring force and connected in front of the second consumer 28, and the spring-side control pressure space of this directional control valve 18 is acted upon by the pressure in the control pressure line 17, and the opposite control pressure space of this directional control valve 18 is acted upon by the pressure of the flow passing to the preferred consumer 13. <IMAGE>

Description

Hydraulic system with two hydraulic consumers

Energy The invention relates to a hydraulic (hydrostatic) System or circuit with a pressure medium source and at least two to this same pressure medium source connected consumers of hydraulic energy, where each of the two consumers is able to absorb such a large maximum current, that the sum of these two maximum flows is greater than the maximum flow the pressure medium source, whereby a device with a directional valve with two control pressure chambers, one of which is spring loaded, is provided which causes one of the two Consumer privileges, that is, at all times the full, from that consumer Required current receives, this consumer emits a pressure signal, which depends on the current flowing through this consumer (as per known as "load sensing control" or "demand current control") and furthermore the second consumer connected to the pressure medium source is connected to a second directional control valve controlled by means of control pressure.

In a vehicle with a pressure medium pump and a hydrostatic one Power steering and another consumer fed by the same pump hydraulic energy, for example a lifting cylinder or a forklift truck a tilt cylinder for the mast, it must be ensured that even if this second consumer takes a large current, the steering device at any time full power is available, which is required for the steering device. To this is to be secured in the case of a hydrostatic steering device with an open center position, So when there is no steering movement, a current through the steering device flows, as a device that ensures that the steering device at all times the required current flows in, a preferred current regulator known, whereby through this Current regulator always flows the current that the steering device needs and only one Excess is diverted through the preferred flow regulator to the second consumer. In the case of steering devices with a closed center position, that is, if none Steering movement takes place, does not consume electricity, is considered a device that causes that the steering device receives the full power required at all times, a priority valve provided through which the working current of the steering device flows (US-PS 4,023 646). Such valves, the flow from the full, both consumers be flowed through and withstand the highest pressure in the consumers are relatively complex.

The invention is based on the object of providing a control device create whose directional control valve is smaller and cheaper.

This object is achieved according to the invention in that the directional control valve the facility that causes one of the consumers to get the full needed at all times Electricity receives, and thus is given priority, between a low-pressure medium source and the control pressure chamber of a hydraulically controlled, upstream of the second consumer switched additional directional valve, which can be displaced against the force of a spring is, is switched and that the spring-side control pressure chamber of the directional control valve of this Means that causes one of the consumers to get the full amount needed at all times Receives current from the current-dependent pressure signal and the opposite control pressure chamber this directional control valve with the full pressure of the consumer to whom the full current should flow, that is, the flow of preferential consumer electricity is applied. That is, for the purpose of reaching out to one of the consumers the full required current always flows in, the required directional control valve is not from the full power flow flows through it, but is only used by a small one, for control purposes serving control pressure flow flows through, which also only has a lower pressure level has, so that this directional control valve only for a small stream and for a lower one Printing needs to be designed and is therefore much cheaper than before known priority valves. The one activated by the control pressure, before the second Consumer-switched directional control valve is preferably designed such that it between the extreme switching positions has transition positions in which a Throttling effect is effected.

In order to be able to control the second consumer arbitrarily, in the line leading to this is provided an arbitrarily actuatable control directional control valve be, which is in series with the directional control valve of the device that causes a the consumer has priority, switched is. This second one However, the consumer can also be controlled by one or preferably two control pressure transducers be, the directional control valve of the device that causes one of the consumers is preferred, in the line between the low-pressure medium source and control pressure transducer is switched.

There are systems in which the second consumer is essential for one higher pressure than the first, privileged consumer. In this Case can be provided that the current flowing to the preferred consumer on a separate flow path through the directional control valve of the device that causes that this consumer is privileged is led. Although in this case a Part of the power flow or the full power flow to which the preferred Consumer flows in, is passed through this valve, this can still be smaller and designed for a lower maximum pressure than that of the second Consumers leading current would have to be led through this valve.

So while with the previously known priority valves a pressure compensator depending on the pressure difference between the pressure of the flowing to the consumer Delivery flow and the flow flowing in from the consumer (usually by means of a Measuring orifice generated) current-dependent pressure signal at the preferred consumer controls the total power flow, is in the device according to the invention when switching on the preferred consumer, the non-preferred (secondary) Consumers controlled in the direction of a smaller flow rate or the power flow, which flows to this, throttled. This is also feasible if apart from the preferred one Consumers several subordinate, i.e. non-privileged further consumers available.

The invention also enables another to be achieved Advantage. Because in the control pressure line behind the directional control valve of the device, which causes one of the consumers to have priority, a control pressure signal only pending when the entire flow delivered by the pressure medium source is not sufficient to supply both consumers with a sufficient flow rate, there is the possibility of reducing the pressure in this control pressure line to be used as a signal by which the flow rate of the pressure medium source increases will. This can be achieved in that this control pressure is applied to an actuating cylinder is passed, in which an adjusting piston can be displaced, which is connected to the adjusting member the primary energy source driving the pressure medium source is connected, so that whenever this primary energy source has not yet reached maximum output or maximum speed is switched and the flow rate is insufficient, the pressure signal the setting element of the primary energy source to greater power output or higher The speed of the primary energy source is adjusted and thus a greater flow rate the pressure medium source causes. This results in an increase in the delivery rate when switched on of the preferred consumer, provided that the primary energy source has not yet was previously set to its maximum power output or speed, so that at Switching on the preferred consumer below the maximum speed of the Primary energy source that consumed by the connected preferred consumer Current is compensated by increasing the flow rate of the pressure medium source, at least partially.

Particularly expedient embodiments are set out in the subclaims specified.

The invention is further explained below with reference to the drawing, in which three particularly favorable exemplary embodiments are shown in the form of circuit diagrams are.

Figure 1 shows a system with a hydrostatic steering device as the preferred consumer and a cylinder as the secondary consumer, the is controlled by means of a directional valve.

Figure 2 shows another system with a steering device as the preferred one Consumer and a cylinder as a subordinate consumer, this cylinder is controlled by means of control pressure transducers.

Figure 3 shows a system with a steering device as the preferred one Consumer and a cylinder as a subordinate consumer, this cylinder is designed for a much higher working pressure than the steering device.

The internal combustion engine 1 serving as the primary energy source is overdriving a shaft 2, the adjustable pump 3 ″ acting as a pressure medium source, its actuator 4 is connected to an actuating piston 5 which is displaceable in an actuating cylinder 6 is. The pump 3 delivers into a delivery line, which is divided into two delivery branch lines 8 and 9 branches, the conveyor branch line 8 leading to the steering device 10, which is the preferred consumer -and in which a steering valve 11 is provided is, from which two lines 12 lead to a steering cylinder 13. The expiring Pressure medium flows via a line 14 to a pressureless container 15 a throttle point 16 is one of which the steering device 10 The current flowing through generates a pressure signal that is dependent on the pressure signal line 17 to the spring-side control pressure chamber of a control pressure-controlled two-position / two-port directional valve 18 leads.

The control pressure chamber of the directional control valve 18 opposite the spring is via the line 19, which is connected to the line 8, from that of the pump 3 of the steering device 10 applied pressure flowing in. To line 8 is still a line 20 connected, which leads to a pressure reducing valve 21, which acts here as a low-pressure medium source and from which the low-pressure line 22 which is connected to the first connection of the directional control valve 18. To the the second connection of the directional control valve 18, the control pressure line 23 is connected. The control pressure line 24 is connected directly to the line 22. The two Control pressure lines 23 and 24 serve to control the two control pressure chambers of the additional directional control valve 25 to apply control pressure.

This additional directional valve 25 is used by one of the two lines 26 and 27 to supply pressure medium to the cylinder 28 provided as the second consumer or to divert pressure medium on the second side through the line 29 to the container 15.

Between the two control pressure lines 23 and 24 on the one hand and the additional directional control valve 25, on the other hand, is a further one that can be operated arbitrarily Directional valve 30 switched from which the two control pressure lines 31 and 32 lead to the two control pressure chambers of the additional directional control valve 25.

The arbitrarily actuatable further directional valve 30 can optionally the control pressure line 23 with the control pressure line 32 and the control pressure line 24 with the control pressure line 31 or vice versa, the control pressure line 23 with the Control pressure line 31 and the control pressure line 24 with the control pressure line 32 be connected so that by arbitrarily operating the further Directional control valve 30, the position of the additional directional control valve 25 and thus the direction of movement and speed of movement of the piston in the cylinder 28 can be controlled.

From a middle connection of the additional directional valve 25 to which the pressure is applied to the cylinder 28, a control pressure line 33 exits, which leads to an input of a pressure-dependent automatic switching valve 34, the other input of which is connected to the pressure signal line 17 via the line 35 is, the valve 34 in each case leading to the higher pressure of the two lines 33 and 35 connects to the line 36, which on the spring-side control pressure chamber of the control directional valve 37 is switched, the opposite pressure chamber via the line 38 is connected to the lines 7, 8, 9 in a known manner controls the pressurization of the actuating cylinder 6 via the line 39 in such a way that that the actuator 4 of the pump 3 is set at any time such that the pump 3 promotes the flow required together by the consumers 10 and 28.

The mode of operation is as follows: In normal operation, there is a line 19 a pressure which is so much higher than the pressure in line 17 that the the force exerted by this pressure on the directional control valve 18 against the force of the spring moves into the position in which the valve 18 closes the lines 22 and the Line 23 connects to container 15. The additional directional valve 25 can in this State can be controlled arbitrarily by the further directional control valve 30 in such a way that the cylinder 28 is acted upon in such a way as this is controlled arbitrarily.

However, the preferred consumer 10 receives through the line 8 a flow rate that is too low, the pressure in line 17 increases relatively the pressure in the line 1 with the result that the force of the spring opens the valve 18 moves in the direction in which the valve 18, the control pressure line 23 with the Low pressure line 22 connects, so that initially strongly throttling then increasingly stronger the pressure in the control pressure line 23 increases with the result that the second Control pressure on the additional directional control valve 25 regardless of the position of the other Directional valve 30 is acted upon and this under the action of the force of the springs is shifted more and more towards its neutral position, so that to the consumer 28 flowing current is throttled more and more, that is, that an ever smaller current flows to the consumer 28, so that via the line 8 a sufficiently large current flows to the preferred consumer 10.

The actuator 40 of the internal combustion engine 1 is provided with an actuating piston 41 connected, which is displaceable in an adjusting cylinder 42 against the force of a spring is. The actuating cylinder 42 is connected to a switching valve 44 through a line 43 connected, which is connected between the two lines 31 and 32. This additional device has the effect that if by moving the directional control valve 18 a signal is given that the same steering device 10 flowing to the consumer current is not sufficient and therefore the current flowing to the consumer 28 is throttled must be, at the same time a pressure signal is given to the actuating cylinder 42, so that the internal combustion engine.l to a higher speed or output a higher power is set. Since in the directional control valve 30, the flow from the line 24 to the each controlled control pressure chamber of the additional directional control valve 25 flows, throttled that of the line 23 to the opposite control pressure chamber of the additional valve 25 incoming current flows through unthrottled, the switching valve switches 44 the higher pressure from line 31 or 32 to the actuating cylinder 42 leading line.

The embodiment according to FIG. 2 differs from the embodiment according to Figure 1 in that the steering device 10 for a significantly lower maximum pressure is designed like the cylinder 28. For example, the pressure relief valve 45 in the steering device 10 can be designed to 140 bar, while the steering cylinder 28 is designed for 190bar. In the system according to Figure 2 is instead of the System according to Figure 1 existing directional control valve 18 provided a directional control valve 48, the differs from the directional control valve 18 in that it has a further flow path has, with which the line 47 connected to the line 7 with the line 49 can be connected, which leads to the steering device 10 and to which the control pressure line 59 is connected. Depending on the position of the valve 48 is between the lines 47 and 49 established an unthrottled or more or less throttled connection. Otherwise, the mode of operation is the same as in the device according to FIG 1.

The device according to Figure 3 differs from the device according to Figure 1 only in that in this case the consumer 28 is not through the further directional control valve 30 is controlled by two control pressure transducers 52 and 53 via the lines 54 and 55, the two control pressure chambers of the additional valve 25 are applied.

The two control pressure transducers 52 and 53 are used as a low-pressure medium source provided auxiliary pump 51 is pressurized, the pressurization takes place via the directional control valve 18. In normal operation, the directional control valve 18 is through the pressure present in line 19, which is so much greater than that in the line 17 pending pressure that the spring force is overcome, pressed into the position, in which the delivery line 56 of the pump 51 is connected to the line 57 the two control pressure transducers 52 and 53 designed as pressure reducing valves connected are. However, increases as a result of too little flowing into the steering device 10 When the current increases, the pressure in line 17 shifts Pressure the directional control valve 18 such that it increasingly the line 57 with the unpressurized container 15 connects, so that the control pressure transducers 52 and 53 only a low pressure is available, so that as a result of the low pressure before the control pressure transducers 52 and 53 also the pressure in the respectively controlled the two lines 54 or 55 drops and thus the additional valve 25 in turn into the Position is shifted in which the consumer 28 flowing through the line 9 Current is throttled.

Claims (8)

Claims Hydraulic system with a pressure medium source and with at least two hydraulic consumers connected to this pressure medium source Energy, the sum of the maximum that can be consumed by one consumer in each case Currents is greater than the maximum flow rate of the pressure medium source, wobzi a Device provided with a directional valve with two control pressure chambers and a spring is that causes one of the consumers at any time the full required electricity receives, with this consumer being one of the flowing through this consumer Outputs current-dependent pressure signal and the second consumer also to a second directional control valve controlled by means of control pressure is connected, thereby characterized in that the directional control valve (18, 48) that one of the consumers at any time the full required electricity receives the effecting device (17, 18, 19, 23 or 48, 23, 24) between a low pressure medium source (21 or 51) and the control pressure chamber one hydraulically controlled against spring force, upstream of the second consumer (28) switched auxiliary directional valve (25) is switched and that the spring-side control pressure chamber this Directional control valve (18 or 48) of said device from the current-dependent pressure signal (Control pressure line 17) and the opposite control pressure chamber of this directional control valve (18 or 48) with the pressure of the consumer (10) to which the full current flows should, in the line (8 or 49) flowing current is applied. 2. Plant according to claim 1, characterized in that in the to the Control pressure chamber of the additional valve (25) leading control pressure line (23, 24) Arbitrarily actuatable control directional control valve (30) is switched. 3. System according to claim 1, in which the consumer, the constantly the full required current is to flow is designed for a lower pressure like the second consumer, characterized in that the consumer (lO), the the required current is to flow continuously, the current flowing in on a separate one Flow path through the directional control valve (48) of the device that causes one of the consumers the required current is constantly flowing in. 4. Installation according to claim 1, in which the second consumer is connected to a directional control valve is connected, the one spring opposite control pressure chamber to a arbitrarily actuatable control pressure transducer connected to the low pressure medium source is connected, characterized in that the directional control valve (18) of the device which has the effect that one (10) of the consumers receives the required electricity at all times, between the low pressure medium source (51) and the control pressure transducer (53 or 52) is switched. 5. Plant according to one of the preceding claims, characterized in that that the consumer (10), to which the required current should constantly flow, the hydrostatic Power steering device (11, 12, 13) of a vehicle. 6. Installation according to claim 5, characterized in that the vehicle is an industrial truck and the second consumer (28) is at least one with one Lifting device is operatively connected cylinder (28). 7. Plant according to one of the preceding claims, characterized in that that of the directional control valve (18 or 48) of the device that causes constant the required current flows to one of the consumers, outgoing control pressure line (23 or 24) branches off a branch line (43) which leads to an actuating cylinder (42), in which one with the adjusting element of the pump (3) forming the pressure medium source is driving Primary energy source (l) connected actuating piston (5) is displaceable. 8. Plant according to claim 1, characterized by an interpretation of the Control valves such that when the preferred consumer (10) is switched on the current through the secondary consumer (28) controlling valve smaller flow rate is controlled, so that the power distribution controlling Valve only from the secondary consumer or consumers flowing stream is flowed through, the pressure medium to the preferred Consumer (10) flows in through a line (8) bypassing this valve.