PRESSURE-SUPPLY DEVICE FOR AN ELECTROHYDRAULIC VALVE CONTROL OF GAS-EXCHANGE VALVES IN INTERNAL COMBUSTION ENGINES

Abstract

A pressure-supply device for an electrohydraulic valve control of gas-exchange valves in internal combustion engines which has a fluid reservoir, a fluid output for the connection of the valve control, and a high-pressure pump which removes fluid from the fluid reservoir and delivers it under high pressure to the fluid output. To attain high pump efficiency and high system dynamics, the high-pressure pump is constructed as constant-displacement pump having a pump inlet and a pump outlet, and the pump outlet is connectible by a switchover valve alternately to the fluid output and, accompanied by blocking of the fluid output, to the fluid reservoir.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a pressure-supply device for an electrohydraulic valve control of gas-exchange valves in internal combustion engines.

BACKGROUND INFORMATION

[0002] In a conventional pressure-supply device described in, for example, German Patent Application No. DE 198 26 047, a high-pressure pump takes the form of a variable-displacement pump, regulated on the delivery side or suction side, which supplies a variable pressure and a variable volumetric flow. The variable-displacement pump is connected with its pump inlet directly to the fluid reservoir, and with its pump outlet, is connected via a non-return valve, with a blocking direction pointing toward the pump outlet, to the pressure-supply-device fluid output, to which is connected a high-pressure accumulator used for storing energy and damping pressure pulsation. The electrohydraulic valve control is supplied with fluid under high pressure via the fluid output, the distributor line or rail connected to the fluid output being designated as a high-pressure circuit of the electrohydraulic valve control. For each valve to be controlled, the electrohydraulic valve control has a hydraulic actuator or valve adjuster which has a positioning piston for the valve actuation, as well as two fluid-filled working chambers acting on the positioning piston. All the valve adjusters are linked to the distributor line or rail, which is under high pressure, in a manner that, in each case, the lower working chamber, acting in the valve-closing direction on a smaller effective area of the positioning piston, is connected directly to the rail, and the upper working chamber, acting in the valve-opening direction on a larger effective area of the positioning piston, is connected to the rail via a first electromagnetic control valve. In addition, the upper working chamber of each valve adjuster is linked via a second electronic control valve to a second rail forming a feedback line which leads to the fluid reservoir.

SUMMARY

[0003] A pressure-supply device, according to an example embodiment of the present invention, for the electrohydraulic valve control of gas-exchange valves may have the advantage that, by the combination of a constant-displacement pump and a switchover valve between the high-pressure circuit and unpressurized circulation, the very good efficiency of the cost-effective constant-displacement pump may be utilized, and a consumption-oriented coupling between the useful fluid flow and the circulation fluid flow is possible, so that the pressure characteristics in the high-pressure rail, linked to the fluid output of the pressure-supply device, for the electrohydraulic valve adjusters may be directly influenced. For example, pulsations in the pressure may be smoothed by purposeful overlapping of delivery of fluid into a high-pressure accumulator connected to the fluid output and removal of fluid from the high-pressure accumulator by the valve adjusters. Particularly when the switchover valve is designed as an electrically controlled solenoid valve, the switchover between delivery quantity zero and maximum delivery is carried out extremely quickly in the millesecond range, so that very high system dynamics are achieved. The switchover valve may be switched synchronously with consumption, time and/or crank angle. The switchover of the constant-displacement pump to unpressurized circulation during delivery pause also ensures a constant cooling and lubrication of the constant-displacement pump by the fluid.

[0004] According to one advantageous example embodiment of the present invention, the constant-displacement pump is self-priming and is connected with its pump inlet to the fluid reservoir. Alternatively, a presupply pump taking in fluid from the fluid reservoir may be arranged upstream from the pump inlet of the constant-displacement pump. The oil pump of the internal combustion engine may advantageously be utilized as a presupply pump.

[0005] According to one advantageous example embodiment of the present invention, the switchover valve is made up of a 2/2-way solenoid valve and a non-return valve. The non-return valve is positioned in a bypass which connects the outlet of the constant-displacement pump to the fluid reservoir. The non-return valve, with the blocking direction pointing toward the pump outlet, is connected on the incoming side to the pump outlet, at which the bypass also branches off, and is connected on the output side to the fluid output, and during unpressurized circulation of the fluid, blocks the high-pressure circuit with respect to the bypass and the high-pressure pump.

[0006] According to one alternative example embodiment of the present invention, the switchover valve is a 3/2-way solenoid valve, of whose three valve connections, one valve output is connected to the pressure-supply-device fluid output making the high pressure available for the valve control, one valve output is connected to the fluid reservoir, and one valve input, switchable alternately to the valve outputs, is connected to the outlet of the constant-displacement pump, so that depending upon the switching position of the solenoid valve, the high-pressure circuit is blocked with respect to the high-pressure pump or is connected to it.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention is described in detail in the following in terms of exemplary embodiments.

[0008] FIG. 1 shows a circuit diagram of a pressure-supply device for the valve control of gas-exchange valves of an internal combustion engine.

[0009] FIG. 2 shows an identical representation as in FIG. 1 according to a further example embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0010] The pressure-supply device shown in the block diagram in FIG. 1 is used for the fluid supply of an electrohydraulic valve control of gas-exchange valves of an internal combustion engine. Such a valve control is described, for example, in German Patent Application No. DE 198 26 047. For the pressure supply, the valve control is connected to a fluid output 11 of the pressure-supply device via a so-called rail which conducts fluid, preferably hydraulic oil, to all valve adjusters of the valve control.

[0011] The pressure-supply device has a fluid reservoir 12, a presupply pump 13, a constant-displacement pump 14 and a high-pressure accumulator 15 that is connected directly to fluid output 11. Fluid output 11 is connected via a pressure-limiting valve 16, that is set to the maximum permitted high pressure in high-pressure accumulator 15, to a return line 17 running to fluid reservoir 12. A restrictor 18 is also arranged in return line 17. On the intake side, presupply pump 13 is connected to fluid reservoir 12, and with its pump outlet, is connected on one hand to the inlet of constant-displacement pump 14, and on the other hand, is connected to return line 17 upstream of restrictor 18. With its pump outlet, constant-displacement pump 14 is connected via a switchover valve 19 to high-pressure accumulator 15 and fluid output 11, respectively. In the example embodiment in FIG. 1, the switchover valve is designed as a 3/2-way solenoid valve 20 having spring resetting, the valve being controlled by an electronic control unit 21 as a function of the fluid pressure prevailing at fluid output 11 and in high-pressure accumulator 15, respectively. The fluid pressure is detected by a sensor taking the form of pressure gauge 22. 3/2-way solenoid valve 20 has a valve input 201 connected to the outlet of constant-displacement pump 14, and two valve outputs 202, 203, to which valve input 201 may be switched alternately depending on the switching position. Valve output 202 is connected to fluid output 11 and high-pressure accumulator 15, and valve output 203 is connected to return line 17 on the input side of restrictor 18.

[0012] If 3/2-way solenoid valve 20 is in the switching position shown in FIG. 1, then high-pressure accumulator 15 is being charged, that is to say, constant-displacement pump 14 is delivering fluid into high-pressure accumulator 15 until the maximum pressure set by pressure-limiting valve 16 is reached in high-pressure accumulator 15 and at fluid output 11. If 3/2-way solenoid valve 20 is transferred by control unit 21 into its other switching position, then fluid output 11 and high-pressure accumulator 15 are blocked vis-à-vis constant-displacement pump 14, and the outlet of constant-displacement pump 14 is connected to return line 17. This results in a nearly pressureless circulation of the fluid, and only as much energy is needed as is necessary for overcoming friction. The operating state in which no quantity of fluid is needed in the high-pressure branch of the valve control, thus at fluid output 11, occurs constantly during normal operation of the internal combustion engine, since constant-displacement pump 14 is designed for full-load requirement, and thus in wide areas of the engine operating map in which only small quantities must always be redelivered into the rail, is over-dimensioned for the consumption occurring here. If there is an increased need for fluid quantity, e.g., as a result of the removal of fluid by the valve adjusters or because of a necessary pressure increase in high-pressure accumulator 15 due to a change in the operating point of the internal combustion engine, then 3/2-way solenoid valve 20 is reset via control unit 21 into its switching position shown in FIG. 1. Constant-displacement pump 14 now delivers fluid via fluid output 11 against the system pressure in valve control 21 into the rail. The power consumption of constant-displacement pump 14 is then proportional to the product of the pressure and the volumetric flow of the fluid.

[0013] The pressure-supply device shown in the circuit diagram in FIG. 2 is modified only with respect to the design of switchover valve 19. The remaining components match those in FIG. 1 and are designated by the same reference numerals.

[0014] In the pressure-supply device according to FIG. 2, switchover valve 19 has a 2/2-way solenoid valve 23 with spring resetting, as well as a non-return valve 24. 2/2-way solenoid valve 23 has a valve input 231 and a valve output 232 which are connected to each other or blocked from each other depending upon the switching position of 2/2-way solenoid valve 23. Valve input 231 is connected to the outlet of constant-displacement pump 14, and valve output 232 is connected to return line 17, so that 2/2-way solenoid valve 23 is situated in a bypass 25 circumventing fluid output 11 and high-pressure accumulator 15, and alternately opens or blocks it. Non-return valve 24 is positioned between the outlet of constant-displacement pump 14, and fluid output 11 and high-pressure accumulator 15, respectively, with a flow-through direction pointing toward fluid output 11 or high-pressure accumulator 15.

[0015] If 2/2-way solenoid valve 23 is in its switching position shown in FIG. 2, bypass 25 is blocked and constant-displacement pump 14 is delivering fluid into high-pressure accumulator 15. The maximum pressure available at fluid output 11 is in turn established by pressure-limiting valve 16. If 2/2-way solenoid valve 23 is switched over into the other switching position against the restoring force of its resetting spring, then the outlet of constant-displacement pump 14 is linked via bypass 25 to return line 17, and fluid is drawn in from fluid reservoir 12 in the unpressurized circulation and is delivered back again to fluid reservoir 12. Non-return valve 24 ensures that the pressure in high-pressure accumulator 15 and at fluid output 11, respectively, does not break down due to open bypass 25.

[0016] In a modification of the pressure-supply device, instead of restrictor 18 arranged in return line 17, a pressure-limiting valve 26 or a non-return valve 27 having a defined opening pressure is used, as symbolized in FIGS. 1 and 2 by components 26, 27 depicted next to restrictor 18. One is thereby able to ensure a constant intake pressure for presupply pump 13, and to avoid cavitations during the deactivation of the outlet of constant-displacement pump 14 by opening switchover valve 19.

[0017] According to a further modification of the pressure-supply device described, constant-displacement pump 14 is self-priming, and is connected with its inlet directly to fluid reservoir 12, so that it is possible to dispense with the presupply pump.

Claims

1-14. (canceled)

15. A pressure-supply device for an electrohydraulic valve control of a gas-exchange valve in an internal combustion engine, comprising: a fluid reservoir, a fluid output under high pressure for connection of a distributor line of the valve control; a switchover valve; and a high-pressure pump configured to deliver fluid from the fluid reservoir and to charge the fluid to high pressure, wherein the high-pressure pump is a constant-displacement pump having a pump inlet and a pump outlet, the pump outlet being connectible alternately by the switchover valve to the fluid output, and being connectible to the fluid reservoir accompanied by a blocking of the fluid output.

16. The pressure-supply device as recited in claim 15, wherein the constant-displacement pump is self-priming, and the pump inlet is connected to the fluid reservoir.

17. The pressure-supply device as recited in claim 15, a presupply pump configured to draw in fluid from the fluid reservoir connected to the pump inlet of the constant-displacement pump.

18. The pressure-supply device as recited in claim 15, wherein the switchover valve includes a 2/2-way valve positioned in a bypass connecting the pump outlet to the fluid reservoir, and a non-return valve that is connected on one hand to the pump outlet and on the other hand to the fluid output and has a blocking direction pointing toward the pump outlet.

19. The pressure-supply device as recited in claim 18, wherein the 2/2-way valve is a solenoid valve having spring resetting.

20. The pressure-supply device as recited in claim 15, wherein the switchover valve is constructed as a 3/2-way valve having two valve outputs and one valve input switchable alternately to the valve outputs; and the valve input is connected to the pump outlet of the constant-displacement pump, one of the valve outputs being connected to the fluid output and the other of the valve outputs is connected to the fluid reservoir.

21. The pressure-supply device as recited in claim 20, wherein the 3/2-way valve is a solenoid valve having spring resetting.

22. The pressure-supply device as recited in claim 19, further comprising: an electronic control unit that is connected to a sensor detecting the pressure at the fluid output, and that switches the solenoid valve depending upon a drop below or an exceeding of a pressure threshold, the solenoid valve being linked to the electronic control unit.

23. The pressure-supply device as recited in claim 15, wherein the fluid output is connected via a pressure-limiting valve to a return line running to the fluid reservoir.

24. he pressure-supply device as recited in claim 23, wherein the connection of the switchover valve to the fluid reservoir is produced on an output side of the pressure-limiting valve connected to the return line

25. The pressure-supply device as recited in claim 23, further comprising: a restrictor arranged in the return line.

26. The pressure-supply device as recited in claim 23, further comprising: a pressure-limiting valve arranged in the return line.

27. The pressure-supply device as recited in claim 23, further comprising: a non-return valve having a defined opening pressure, the non-return valve being arranged in the return line.

28. The pressure-supply device as recited in claim 15, further comprising: a high-pressure accumulator connected to the fluid output.