Method for operating a device for injecting water into an internal combustion engine

Abstract

A method for operating a device for injecting water into an internal combustion engine, the device including a water tank for storing water, a pump for conveying the water, the pump being connected to the water tank via a first line, and the pump being operable in a conveying mode and in a back-suction mode, a drive for driving the pump, at least one water injector, which is configured to inject water into an air-conducting line of the internal combustion engine, the water injector being connected to the pump via a second line, the at least one water injector being opened during the operation of the pump in the back-suction mode, in which the water is conveyed in the direction of the water tank, so that air flows into the second line.

Claims

1. A method for operating a device for injecting water into an internal combustion engine, the device including a water tank for storing water, a pump for conveying the water, the pump being connected to the water tank via a first line, and the pump being operable in a conveying mode and in a back-suction mode, a drive for driving the pump, at least one water injector, which is configured to inject water into an air-conducting line of the internal combustion engine, the water injector being connected to the pump via a second line, the method comprising: opening the at least one water injector during the operation of the pump in the back-suction mode, in which the water is conveyed in a direction of the water tank, so that air flows into the second line, wherein the back-suction mode of the pump is started after the internal combustion engine is switched off.

2. The method as recited in claim 1, wherein the device for injecting water includes a control unit, the control unit controlling the operation of the pump and the at least one water injector.

3. The method as recited in claim 2, wherein the control unit controls, model-based, at least one of: a starting point in time, a duration, and a sequence of the back-suction mode of the pump.

4. The method as recited in claim 3, wherein the duration of the back-suction mode corresponds at least to a period of time, which is required for back-suctioning a volume of water, which extends from the pump to and including the water injector.

5. The method as recited in claim 1, wherein at least 75% of the water, which was in the second line and in the at least one water injector before the start of the back-suction mode, is suctioned back after termination of the back-suction mode.

6. The method as recited in claim 2, wherein the control unit controls at least one of: (i) a point in time, and (ii) a period of time, of an opening of the at least one water injector.

7. The method as recited in claim 1, wherein the at least one water injector is opened simultaneously with a start of the operation of the pump in the back-suction mode.

8. The method as recited in claim 1, wherein the at least one water injector is opened with a time delay relative to a start of the operation of the pump in the back-suction mode.

9. The method as recited in claim 1, wherein the at least one water injector is opened at least 100 ms later than a start of the operation of the pump in the back-suction mode.

10. The method as recited in claim 1, wherein the device includes a pressure sensor, which in the second line measures a pressure of the water in the line and the at least one water injector not being opened during the operation of the pump in the back-suction mode until the water pressure in the second line drops below a limiting value.

11. The method as recited in claim 1, wherein in the back-suction mode, air flows into the second line from the air-conducting line of the internal combustion engine.

12. The method as recited in claim 1, wherein the second line is directly connected to the pump.

13. The method as recited in claim 8, wherein the time delay is a function of a back-suction capacity of the pump and a volume of water to be emptied in the second line.

14. The method as recited in claim 10, wherein the limiting value corresponds to a pressure that is no more than an air pressure at an air inlet port of the internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an example of a device for injecting water into an internal combustion engine.

(2) FIG. 2 shows an example of a positioning of a water injector on an internal combustion engine.

(3) FIG. 3 shows two possible sequences of the method according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(4) A device 1 for injecting water and a detail of an internal combustion engine 2 are depicted by way of example in FIG. 1 and FIG. 2.

(5) The device 1 for injecting water includes a pump 4 and an electric drive 5 for driving the pump 4. A water tank 3 is also provided, which is connected to pump 4 via a first line 10. A second line 11 connects pump 4 to at least one water injector 6. As depicted here, a plurality of water injectors 6 may be connected to one another and to pump 4 via a distributor 7 or a rail.

(6) To inject water into an air inlet port 22 or the intake manifold of internal combustion engine 2, water is fed from water tank 3 through pump 4 into water injector 6. The water in water tank 3 is, for example, a condensate from an air conditioning unit not shown here, the condensate being fed via an inflow line 8 to water tank 3. Alternatively or in addition to the condensate from the air conditioning unit, water tank 3 may be filled preferably with deionized water from the outside via a refill line 9. A screen 91 may be optionally provided in refill line 9. Furthermore, a prefilter 92 is situated in first line 10 and a fine filter 93 is situated in second line 11, in order to filter potentially present foreign bodies or dirt particles from the water. Prefilter 92 and/or fine filter 93 may optionally be designed to be heatable.

(7) A sensor 32 may also be situated in or on water tank 3, which measures the fill level of the water in water tank 3 and/or the temperature of the water in water tank 3, and which forwards the result to a control unit 30 for monitoring and controlling the device 1 for injecting water.

(8) Control unit 30 also controls pump 4 and its operating mode, i.e., the conveying direction, the conveying capacity and the duration of the respective operating modes of pump 4. Pump 4 may be operated in two opposite conveying directions. In the so-called conveying mode, pump 4 conveys water from water tank 3 to water injector 6. In the back-suction mode, pump 4 conveys or suctions the water from water injector 6 back into water tank 3. By selecting the appropriate speed of pump 4, it is possible to adjust the desired conveying capacity of pump 4.

(9) To regulate the water pressure in second line 11, a pressure sensor 31 and/or a pressure regulator in the form of an aperture 33 may be situated in a return flow line 12 in device 1. Return flow line 12 connects second line 11 to water tank 3. Situated in return flow line 12 is a check valve 34, which prevents pump 4 from suctioning water via the return flow line 12 from water tank 3 into second line 11 during the operation of pump 4 in the back-suction mode.

(10) Control unit 30 regulates the desired pressure in second line 11 by a combination of pressure sensor 31 with a speed variation of pump 4. The pressure in distributor 7 or in water injector 6 is set preferably in the range of 3-10 bar. This has the advantage that water covering the wall of the air inlet port 22 is minimized or eliminated when water is injected into air inlet port 22 of internal combustion engine 2. As a result, all of the injected water enters the combustion chamber 23.

(11) Internal combustion engine 2 schematically depicted in FIG. 2 includes a plurality of valves. Internal combustion engine 2 includes one combustion chamber 23 per cylinder, in which a piston 24 is moveable back and forth. Internal combustion engine 2 also includes two inlet valves 25 per cylinder, each having one inlet port 22, via which air is fed to combustion chamber 23. An exhaust gas is discharged via an exhaust pipe 26. For this purpose, an inlet valve 25 is situated on inlet port 22 and an outlet valve 27 is situated on outlet port 26. A fuel injector 28 is also situated on combustion chamber 23.

(12) A water injector 6 is situated on air inlet port 22 or on the intake manifold, which injects water in the direction of inlet valve 25 of internal combustion engine 2 while controlled by control unit 30.

(13) Control unit 30 controls the operation of pump 4 and of water injector 6. Control unit 30 also controls the operation of internal combustion engine 2. Control unit 30 receives information via various sensors such as, for example, pressure sensor 31, velocity sensor, temperature sensor 32, etc. about the surroundings and about the operating states of the individual components of device 1 for injecting water and internal combustion engine 2, and based on this information is able to control and/or regulate the operation of device 1 for injecting water as well as internal combustion engine 2. Control unit 30 may distinguish between various operating states of internal combustion engine 2: drive and control devices-overrun.

(14) Two possible embodiments of the method according to the present invention for operating a device 1 for injecting water are schematically depicted in FIG. 3. In a first method step 100, internal combustion engine 1 is switched off, i.e. the operating state of internal combustion engine 1 changes from drive to control devices-overrun. Control unit 30 in device 1 for injecting water correspondingly starts the method according to the present invention. Due to the change of the operating mode of internal combustion engine 1, control unit 30 also initiates a change of the operation in pump 4 from conveying mode to back-suction mode. The conveying mode of pump 4 is reversed, so that the water from water injector 6 or the water injectors is suctioned back in the direction of water tank 3. This corresponds to second method step 101 in FIG. 3. The start of the back-suction mode of pump 4 typically takes place immediately with the change of the operating mode in internal combustion engine 2.

(15) In the method sequence according to FIG. 3 a), water injector 6 or the water injectors is/are opened simultaneously with the start of the back-suction mode of pump 4, so that air from air inlet port 22 of internal combustion engine 2 is able to flow into device 1 for injecting water, simultaneously meaning that the two actions are initiated within a time span of 50 ms.

(16) In an alternative method sequence according to FIG. 3b), water injector 6 or the water injectors is/are opened with a time delay relative to the start of the back-suction mode of pump 4 in a further method step 102. The time delay may be a previously determined fixed period of time of, for example, 100 ms or 200 ms. Alternatively, the precise value of the time delay may be selected as a function of the back-suction capacity of pump 4 and of the volume to be emptied in second line 11 and of water injector 6 or the water injectors.

(17) Alternatively, it is also possible that the time delay is varied situationally. Control unit 30 monitors the water pressure in second line 11 via pressure sensor 31 situated in second line 11. Control unit 30 opens water injector 6 or the water injectors only if the pressure measured by pressure sensor 31 drops below a limiting value. This limiting value for the pressure is preferably equal to the air pressure prevailing in air inlet port 22 or is below the air pressure in air inlet port 22. This prevents a portion of the water from flowing from water injector 6 or from second line 11 into air inlet port 22 of internal combustion engine 2 and potentially freezing solid there when internal combustion engine 2 is stopped and with low outside temperatures.

(18) In last method step 103, the back-suction mode of pump 4 is terminated by switching off the pump and water injector 6 is closed again.

(19) The duration and sequence of the operation of pump 4 in the back-suction mode are controlled by control unit 30. In the process, the duration and/or the sequence of the back-suction mode may be model-based or situationally controlled. In the model-based sequences, the duration of the operation of pump 4 in the back-suction mode is established as a function of the volume of the components to be emptied, of the adjusted conveying capacity of pump 4, as well as of the activation strategy of water injectors 6. The duration in this case corresponds to at least a period of time, which is required with the established conveying capacity of pump 4 for back-suctioning the volume of water extending from pump 4 up to water injectors 6.

(20) The conveying capacity of pump 4 is proportional to the speed of pump 4. Also proportional to the speed of pump 4 are the noises caused by pump 4. It is conceivable, for example, that as long as additional noise-generating components, for example, a cooler or a fan for the internal combustion engine, are still active, the pump is operated at a higher speed and that with the reduction of the number of additional noise-generating components, the speed of pump 4 and, therefore, the noises generated by pump 4, are reduced. In principle, it is conceivable that the speed of pump 4 remains constant during the back-suction phase. Alternatively, the speed of the pump may also be gradually and/or continuously reduced.

(21) In the case of a situationally controlled sequence of the operation of pump 4 in the back-suction mode, control unit 30 regulates the speed of pump 4 as a function of the operating state of additional components of the internal combustion engine such as, for example, as a function of the entire background noise of the internal combustion engine and/or of additional parameters of the surroundings such as, for example, the outside temperature.

(22) The control unit may, for example, operate the pump in the back-suction mode until at least 75% of the water is suctioned back. The residual water located in second line 11 and water injectors 6 may be calculated in the control unit on the basis of the pressure information of pressure sensor 31 situated in second line 11 and on the basis of the information stored in the control unit regarding the volume to be emptied. The maximum amount of water located in second line 11 and in water injector 6 or the water injectors at the start of the operation of pump 4 in the back-suction mode provides the initial value for the computation. A maximum of 25% of the original water remains behind after the end of the operation of pump 4 in the back-suction mode. Tests by the applicant have shown that this amount of water in the frozen state generally does not damage the components. Preferably at least 85% of the water is suctioned back.

(23) Water tank 3 and the components situated in or on water tank 3 must be designed to be freeze-resistant, since naturally these components of device 1 for injecting water remain filled even after the end of the operation of pump 4 in the back-suction mode. In addition, the water may not be suctioned off from aperture 33, check valve 34 and return flow valve 12, so that these components are also designed to be freeze-resistant.