DE4135016A1 - Heating system for pressure medium in hydraulic circuit - uses continuous measurement of temp. of pressure medium and/or part of circuit - Google Patents

Abstract

The system is for use in a hydraulic circuit (1-24), in which a pressure is built-up. When a certain pressure level is reached, pressure medium is brought to a lower level, by a pressure limitation valve. The temp. of the pressure medium, and/or one of the parts in the hydraulic circuit, is continuously measured. The heating process is continued, until a ceiling temp. is reached. During the heating process, the hydraulic circuit is operated under part load. USE/ADVANTAGE - Simplified warming process for pressure medium in hydraulic circuit.

Description

Invention relates to a method for warming up the Pressure medium in a hydraulic circuit in which a Pressure is built up and when a certain one is reached Pressure levels Pressure medium over at least one pressure limit control valve is brought to a lower pressure level. However, the invention also relates to a suitable one Contraption.

Commercial vehicles with a hydraulic circuit, such as construction machines, especially excavators, are described in the Way warmed up before starting to minimize wear to keep. The warm-up procedure is usually carried out by driving a hydraulic energy consumer who is braked. This can e.g. B. be the slewing gear of the excavator. The emerging in the line leading to the consumer Pressure is released by pressure relief valves, whereby the end spraying through the pressure relief valves Pressure medium heated. The quality of the warm up will determined only by the driver, because the warm-up process is controlled by him arbitrarily.  

The present invention is based on the object Simplify warm-up process.

This object is achieved in that the Temperature of the pressure medium and / or at least one of the Components continuously measured in the hydraulic circuit and the warm-up process is forcibly until a limit temperature has been reached. The warming up process takes place automatically when the machine is too cold, whereby the Driver no cumbersome warm-up procedure by actuation is required by consumers, except for the start of the System no further intervention by the driver for the warm-up operation is provided. It also ensures that the machine is already at operating temperature at the start of work or at least a wear-reducing temperature has reached.

It is particularly advantageous in a method in which the delivery volume of a hydrostatic variable displacement pump from a demand flow controller is regulated and one from the funding pressure-dependent first signal and one from the consumer pressure-dependent second signal to the demand flow controller be supplied until the limit temperature is reached Demand flow controller one in the same direction as the second Signal acting third signal and the adjustment to adjust the pump in the direction of increasing the displacement len. In this way, the hydraulic Circulation existing components used for warming up.

In a development of the invention it is provided that the hydraulic circuit while warming up under part load is operated in order to be as gentle as possible To achieve warm up.  

Since in the method according to the invention mostly a hydraulic one Pump is powered by an internal combustion engine, it is cheap if the internal combustion engine with compared to the provided full load of the hydraulic circuit Operating speed reduced speed is operated. This will wear out the still cold combustion motors reduced. In further training of this configuration it is proposed that with increasing temperature the Speed of the internal combustion engine is increased by the To speed up the warm-up process. This can be done in stages or also done continuously.

To carry out the generic method is at a device in which the hydraulic circuit is a hydrostatic variable displacement pump and at least one on it connected consumers and a demand flow controller has, by a of the delivery pressure of the variable displacement pump dependent first signal and a consumer pressure dependent second signal is controllable, according to the invention provided that a warm-up regulator on the input side the temperature of the pressure medium and / or at least one of the components in the hydraulic circuit measuring temperature sensor is connected and a comparison device with a limit temperature value stored therein, is in operative connection with the demand flow controller, whereby below the limit temperature on the demand flow controller third signal in the direction of an increase in displacement Variable pump is effective.

According to an advantageous development of the fiction moderate device in which an auxiliary constant pump with a connected control device for controlling the Consumer is provided, it is proposed that the Active connection from one in the delivery line of the auxiliary arranged constant pump and when reaching the limit temperature against spring force from a starting position in  a switch position switchable overflow valve is formed is that by the warm-up regulator towards the switching position can be acted upon, in the starting position of the Overflow valve the connection of the control unit with the Auxiliary constant pump interrupted and the demand flow controller is connected to a signal line in which the third Signal is guided, and being in the switching position of the over flow valve the auxiliary constant pump with the control unit connected and the signal line is interrupted. As long as the limit temperature has not yet been reached, remains Warm-up regulator passive, so that the overflow valve in its Starting position persists and thus in the signal line and thus on the demand flow controller in the direction of a stroke volume Enlargement of the variable pump effective third signal pending. At the same time, an arbitrary activation of the Prevents consumers, which ensures that no unintended movements of the consumer will. As soon as the limit temperature is reached, a ensures from the warm-up controller to the overflow valve Signal that the relief valve from the output position in the switch position and thereby the Forwarding of the third signal to the demand flow controller is interrupted, whereupon the variable pump again minimal displacement is pivoted. The arbitrary Activate the consumer by applying the tax device with the delivery pressure from the auxiliary constant pump now possible again.

It is favorable if according to a first embodiment variant in the initial position of the overflow valve Delivery line of the auxiliary constant pump with the first input of a shuttle valve is connected, the second input attached to a line to which consumer pressure can be applied is closed and its exit with one towards one Effective increase in delivery volume of the variable displacement pump  Control surface of the demand flow controller is connected. The effective during the warm-up on the demand flow controller The third signal is the flow rate or the delivery pressure the auxiliary constant pump and in the normal Work operation loadable with consumer pressure Sensing line fed, creating the load sensing side of the demand flow controller in the direction of a delivery volume enlargement of the variable pump is applied.

As an alternative to the first embodiment described it is a variant based on a second design variant it is also possible that the demand flow controller has an additional in the direction of an increase in the delivery volume Pump effective control surface to which one with the Overflow valve connected signal line is guided in Starting position of the overflow valve with the delivery line the auxiliary constant pump and in the switching position of the overflow valve is connected to a drain line. Here too so the delivery pressure of the auxiliary constant pump as the third Signal used and in a special signal line during of the warm-up process to the demand flow controller.

Finally, in a third variant be provided in the initial position of the overflow valve the signal line with a the delivery pressure of the adjuster pump leading line and in the switching position of the over flow valve the signal line with a consumer to connect the pressure-carrying line. The signal line will So constantly used, namely when warming up to guide the third signal, which is taken from the high pressure circuit, and during normal operation of the plant to manage the Load sensing signal.  

In an advantageous development of these three variants, in the line that can be supplied with delivery pressure the variable displacement pump has a pressure relief valve arranged, it is proposed that the pressure relief valve under Interposition of a first throttle a second pressure limit valve is connected in parallel, the first Pressure relief valve has a relief connection, the one with the load connection of the second pressure limitation valve is connected and from one to the overflow valve leading line branches in which a second throttle is arranged and in the starting position of the overflow valve connected to a drain line and in switching position of the overflow valve is blocked. The consequence the increase in the displacement of the variable displacement pump Conveying line pressure arises as a result of the special Arrangement of the two pressure relief valves on one value limited, which is below the maximum in working mode permissible, through the first pressure relief valve specified pressure.

Regardless of which of the design variants featured see, it is advantageous to the comparator to add a summing element with two inputs one input the output of the comparison device and at its other entrance an arbitrarily operable one On-off switch is connected. After completing the Warm-up phase is therefore a switching on of the overflow valve, in order to be able to control the consumer via the control unit, only possible by pressing this switch, as for Generation of an output signal of the summing element is not only the limit temperature with which a must be reached first input signal is formed on the summing element, but also a signal at the second input, namely the Switch-on signal of the on-off switch must be present.  

Further advantages and details of the invention will be based on the schematically shown in the figures Embodiment explained in more detail. It shows:

Fig. 1 is a hydraulic circuit diagram of a device for carrying out the method according to the invention in a first variant of embodiment,

Fig. 2 shows a detail of the circuit diagram of FIG. 1 with a second embodiment variant of the device,

Fig. 3 shows a third embodiment variant,

Fig. 4 shows a fourth embodiment variant.

Fig. 1 is driven by an internal combustion engine 1 hydrostatic variable displacement pump 2 to a delivery line 3 to which a plurality of consumers, not shown in the figure via the valve means 4 are connected hydraulic energy. It is e.g. B. to the usually existing on a hydraulic excavator consumers, such as slewing gear, traction motors, boom cylinders, bucket cylinders, etc. The valve devices 4 are connected to a load-sensing line 5 , in which the highest pending at one of the consumers during operation Pressure is guided and used to regulate the flow rate of the variable displacement pump. For this purpose, a demand flow controller 6 is provided in a known manner, which is connected to a line 7 branching from the delivery line 3 , which opens at an adjusting cylinder 8 of the variable pump 2 . The demand flow controller 6 is controlled during operation by the delivery pressure of the variable pump 2 (first signal) and the highest consumer pressure (second signal). Both the delivery line 3 and the load-sensing line 5 are protected by pressure relief valves 9 and 10, respectively. The control of the valve devices 4 is carried out with the aid of control devices 11 , which are provided for connection to the delivery line 12 of an auxiliary constant pump 13 also driven by the internal combustion engine 1 .

After starting the internal combustion engine 1 , the variable displacement pump 2 is set to a minimum delivery volume, since in the case of unactuated consumers the delivery pressure in the delivery line 3 and thus in the line 7 moves the demand flow regulator to the right in the figure, as a result of which pressure medium in the actuating cylinder 8 on both sides of the there arranged control piston acts and due to the surface conditions this is moved into a position that corresponds to an adjustment of the variable pump 2 to the minimum delivery volume. To warm up the pressure medium and thus the hydraulic components, one of the consumers has been controlled and held or braked according to the prior art, so that on the demand flow controller 6 a consumer pressure acts in addition to the delivery pressure and the delivery volume of the variable displacement pump 2 is increased until due to the resulting pressure rise in the delivery line 3, the pressure relief valve 9 opens and pressure medium is sprayed into the reservoir with simultaneous heating.

This is where the invention comes into play: In the delivery line 12 of the auxiliary constant pump 13 , an overflow valve 14 configured as a 2/2 way valve is arranged, which can be actuated electromagnetically. The overflow valve 14 is spring-loaded in the direction of its starting position, the connection of the delivery line 12 of the auxiliary constant pump 13 to the control units 11 being interrupted in this starting position. The input connections of the control devices 11 are instead connected to a pressureless reservoir.

At the same time, the delivery line 12 is connected to a signal line 15 , which is connected to a first input of a shuttle valve 16 , which has its second input and its output connected to the load-sensing line 5 .

A temperature sensor 17 is arranged, for example, so that the temperature of the pressure medium in the reservoir can be measured. The temperature sensor 17 is connected to a warm-up controller 18, which is connected on the output side to the overflow valve 14 and, when an output signal is present, applies it in the direction of a switching position in which the delivery line 12 of the auxiliary constant pump 13 is connected to the control units 11 and the signal line 15 is connected to the unpressurized storage container. The warm-up controller 18 has a comparison device 19 to which the temperature sensor 17 is connected and in which a limit temperature value is stored. The output of the comparison device 19 is connected to the one input of a summing element 20 , the other input of which is connected to an energy supply line 21 which leads to a battery 22 and in which an on / off switch 23 which can be actuated by the driver is arranged. An operational amplifier 24 is connected to the summing element.

The operation of the device described is like follows.

The temperature of the pressure medium measured by the temperature sensor 17 at the beginning of the warm-up process is compared in the comparison device 19 with the limit temperature value and, in the case of a cold system, it is determined that the limit temperature has not yet been reached. Therefore, no signal from the comparison device 19 or a signal with the level 0 is passed on to the summing element 20 .

As a result, no signal is passed on by the summing element 20 , so that the overflow valve 14 is not acted upon and remains in its spring-loaded starting position. It is therefore the delivery line 12 of the auxiliary constant pump 13 (the delivery pressure of the auxiliary constant pump 13 thus forms a third signal effective only when warming up) with the signal line 15 , so that the demand flow controller from the delivery pressure of the auxiliary constant pump 13 via the delivery line 12 , the signal line 15 , the shuttle valve 16 and between the shuttle valve 16 and the spring side is the demand flow regulator lying branch 5 'of the load-sensing line 5 and thus the applied Ver variable displacement pump 2 in the direction of a capacity enlargement adjusted. Characterized pressure medium is sprayed over the Druckbe limit valve 9 in the delivery line 3 to the unpressurized reservoir and heated. A loading of the control units 11 by the delivery pressure of the auxiliary constant pump 13 is prevented due to the starting position of the directional valve 14 .

As soon as the limit temperature is reached, the comparison device 19 of the warm-up controller 18 outputs a signal to the summing element 20 . If the on-off switch 23 is switched on by the driver, there is also a signal at the second input of the summing element 20 , so that the warm-up controller 18 sends an output signal to the overflow valve 14 , which then switches to the switch position. The signal line 15 is therefore connected to the reservoir and the delivery line 13 to the control units. As a result, the shuttle valve 16 can switch freely into a position in which the transmission of a consumer pressure to the demand flow regulator 6 is made possible.

According to one embodiment of the invention, the temperature sensor 17 is additionally connected to a control device 24 , which is provided to influence the speed of the internal combustion engine 1 . As a result, the internal combustion engine 1 , which normally has an approximately constant operating speed when the system is in operation, can be operated at a lower than the operating speed during the warm-up phase in order to reduce wear in the cold state. Moreover, it is also possible during warm-up - graded the speed of the engine 1 by the controller 24 or to increase continuously to accelerate process to perform the warming - with increasing temperature of the pressure medium.

In Fig. 2 and the other figures, the same reference characters are used for components that have already been described for Fig. 1. In the embodiment variant according to FIG. 2, there is an additional footprint on the demand flow controller 6 , which is effective in the direction of increasing the displacement of the variable pump 2 , to which a signal line 15 a is led, which in the initial position of the overflow valve 14 a is connected to the delivery line 12 of the auxiliary constant pump 13 . In the switching position of the overflow valve 14 a, the signal line 15 a is closed to the unpressurized reservoir and the delivery line 12 to the control devices 11, not shown in the figure. The load sensing line 5 is constantly connected to the demand flow controller.

In the embodiment variant according to FIG. 3, in contrast to those of FIGS. 1 and 2 as a 3/2-way valve formed spill valve 14 b is provided, in addition led to the further, branching off from the delivery line 3 of the variable displacement pump 2 line 25 is. The line 25 is in the starting position of the overflow valve 14 b with the line branch 5 ', which opens at the effective in the direction of an increase in displacement of the variable displacement pump 2 footprint of the demand flow controller 6 and in the switching position of the overflow valve 14 b connected to the load sensing line 5 is. Thus, the influencing of the load-sensing side (tongue side) of the demand-feed regulator 6 during the warm-up operation is not performed by tapping the operating in the low-pressure region auxiliary constant pump 13 but of working at high pressure variable displacement pump. 2

In the embodiment variant according to FIG. 4, as in FIGS. 1 and 2, the delivery line 12 of the auxiliary constant pump 13 is provided for obtaining the third signal which is effective during the warming-up. The overflow valve 14 c is here, however, also designed as a 3/2-way valve in order to be able to take on a further function. So that the resulting during the warm-up in the delivery line 3 of the variable pump 2 delivery pressure does not reach the maximum value provided in normal working mode, is connected to the delivery line 3 pressure relief valve 9 with the interposition of a first throttle 26, a second pressure limiting valve 27 connected in parallel. As shown in FIG. 4, this is preferably adjustable. The load connection of the second pressure relief valve 27 is connected to the relief connection of the first pressure relief valve 9 . In addition, a line 28 branches off from the load connection of the second pressure limiting valve 27 , which leads to the overflow valve 14 c with the interposition of a second throttle 29 . In the initial position of the overflow valve 14 c, the load sensing line 5 is interrupted. The remaining line branch 5 'is connected to the delivery line 12 of the auxiliary constant pump 13 . The line 28 is connected to the unpressurized reservoir as are the inputs of the control devices 11 not shown in FIG. 2. The arrangement of the pressure relief valves 9 and 27 and the throttles 26 and 29 in the initial position of the relief valve 14 c limits the pressure in the delivery line 3 of the variable displacement pump 2 to a lower value than the maximum value usually predetermined by the pressure relief valve 9 , whereby both pressure relief valves 9 and 27 are effective. In the switching position of the overflow valve 14 c, however, the line 28 is blocked, so that only the pressure relief valve 9 is effective.

Claims (12)

1. A method for heating the pressure medium in a hydraulic circuit, in which a pressure is built up and pressure medium is brought to a lower pressure level via at least one pressure relief valve when a certain pressure level is reached, characterized in that the temperature of the pressure medium and / or at least one of the Components are continuously measured in the hydraulic circuit and the warm-up process is forcibly carried out until a limit temperature is reached. 2. The method according to claim 1, in which the delivery volume of a hydrostatic variable pump is regulated by a demand flow controller and a first signal dependent on the delivery pressure and a second signal dependent on the consumer pressure are supplied to the demand flow controller ( 6 ), characterized in that until the Limit temperature to the demand flow controller act in the same direction as the second signal, the third signal is fed and the variable pump ( 2 ) is adjusted in the direction of an increase in displacement. 3. The method according to claim 1 or 2, characterized net that the hydraulic circuit during the Warming up is operated under partial load. 4. The method according to any one of the preceding claims, in which a hydraulic pump is driven by an internal combustion engine, characterized in that the internal combustion engine ( 1 ) is operated at a reduced speed compared to the operating speed provided at full load of the hydraulic circuit. 5. The method according to claim 4, characterized in that the speed of the internal combustion engine ( 1 ) is increased with increasing temperature. 6.Device for warming up the pressure medium in a hydraulic circuit, the hydraulic circuit having a hydrostatic variable displacement pump and at least one consumer connected to it and a demand flow regulator which can be controlled by a first signal dependent on the delivery pressure of the variable displacement pump and a second signal dependent on the consumer pressure, characterized in that a warm-up controller ( 18 ) is connected to the input side of which a temperature sensor ( 17 ) measuring the temperature of the pressure medium and / or at least one of the components in the hydraulic circuit is connected and which has a comparison device ( 19 ) with a limit temperature value stored therein, regulator to the demand power is (6) in operative connection, wherein below the limit temperature at the demand flow regulator (6) a third signal in the direction of a Hubvolumenvergrößerung the variable displacement pump (2) is effective. 7. The device according to claim 6, wherein an auxiliary constant pump with an attached control device for controlling the consumer is provided, characterized in that the operative connection of one in the delivery line ( 12 ) of the auxiliary constant pump ( 13 ) and upon reaching the limit temperature against spring force overflow valve ( 14 , 14 a, 14 b, 14 c) which can be switched from a starting position into a switching position and which can be acted upon by the heating controller ( 18 ) in the direction of the switching position, with the overflow valve ( 14 , 14 a, 14 b , 14 c) the connection of the control device ( 11 ) to the auxiliary constant pump ( 13 ) is interrupted and the demand current controller ( 6 ) is connected to a signal line ( 15.5 ', 15 a) in which the third signal is carried, and wherein in the switching position of the overflow valve ( 14 , 14 a, 14 b, 14 c) the auxiliary constant pump ( 13 ) is connected to the control unit ( 11 ) and the signal line ung ( 15.5 ', 15 a) is interrupted. 8. The device according to claim 7, characterized in that in the starting position of the overflow valve ( 14 ), the delivery line ( 12 ) of the auxiliary constant pump ( 13 ) with the first input of a shuttle valve ( 16 ) is connected, the second input of which can be acted upon by a consumer pressure line ( 5 ) is connected and its output is connected to a control surface of the demand flow regulator ( 6 ) which is effective in the direction of increasing the volume of the variable displacement pump ( 2 ). 9. The device according to claim 7, characterized in that the demand flow controller ( 6 ) has an additional effective in the direction of a volume increase of the adjusting pump effective control surface to which a with the overflow valve ( 14 a) connected signal line ( 15 a) is guided in the starting position of the overflow valve ( 14 a) with the delivery line ( 12 ) of the auxiliary constant pump ( 13 ) and in the switching position of the overflow valve ( 14 a) with a drain line. 10. The device according to claim 7, characterized in that in the starting position of the overflow valve ( 14 b), the signal line ( 5 ') with a line leading the delivery pressure of the variable displacement pump and in the switching position of the overflow valve ( 14 b) with a line leading the consumer ( 5 ) is connected. 11. The device according to one of claims 8 to 11, wherein a pressure relief valve is arranged in a line to which the variable displacement pump can be supplied with delivery pressure, characterized in that the pressure relief valve ( 9 ) with the interposition of a first throttle ( 26 ), a second pressure relief valve ( 27 ) in parallel is switched, wherein the first pressure relief valve ( 9 ) has a relief connection, which is connected to the load connection of the second pressure relief valve ( 27 ) and from which branches to the overflow valve ( 14 c) leading line ( 28 ) in which a second throttle ( 29 ) is arranged and in the starting position of the overflow valve ( 14 c) is connected to a drain line and is shut off in the switching position of the overflow valve ( 14 c). 12. Device according to one of claims 7 to 11, characterized in that the comparison device ( 19 ) is followed by a summing element ( 20 ) with two inputs, at one input of the output of the comparison device ( 19 ) and at the other input an arbitrary actuatable on-off switch ( 23 ) is connected.