Method and device for controlling an internal combustion engine

Abstract

A method and device for controlling an internal combustion engine are proposed, the engine comprising at least one cylinder and a piston arranged therein, and featuring oil cooling for the piston. The flow of oil through the oil cooling system to the piston is controlled by a valve. Switching of the oil cooling valve is monitored by evaluating an acoustic signal. A faulty switching of the oil cooling valve affects the control of the internal combustion engine.

Description

State of the art

[0001] The invention relates to a method and a device for controlling an internal combustion engine according to the preamble of the independent claims. A method for controlling an internal combustion engine is already known from DE 10 2009 057 549 A1, which has oil cooling for a piston arranged in a cylinder. In this method, the oil cooling is switched on in certain operating ranges of the internal combustion engine and switched off in other operating ranges. Advantages of the invention

[0002] In contrast, the inventive method and device have the advantage that the switching of an oil cooling valve is reliably monitored. This allows for monitoring of the piston's oil cooling, and in particular, the detection of faulty switching, i.e., a failure of the valve to switch. In response to a faulty valve switching, the operation of the internal combustion engine can be adjusted accordingly. This increases the operational reliability of the internal combustion engine and allows its operation to be adapted to the oil cooling condition. This adaptation also reduces the emission of avoidable exhaust gases from the internal combustion engine.

[0003] Further advantages and improvements result from the measures described in the dependent patent claims. The evaluation of the oil cooling system's acoustic signals is particularly straightforward thanks to a knock sensor mounted on the internal combustion engine. Such knock sensors are already standard equipment on many internal combustion engines, eliminating the need for a separate sensor element. The acoustic signal can be used to conveniently detect when the valve opens. Furthermore, the acoustic signal can be used to monitor when the valve closes. In particular, the precise moment the valve switches can be evaluated. The amplitude of the acoustic signal can also be used to analyze the valve's switching behavior.If it is determined that the valve is faulty and fails to open, the thermal load on the internal combustion engine is limited by reducing its power output. If it is determined that the valve is faulty and fails to close, meaning the oil cooling is permanently active, operating conditions that could lead to oil being drawn into the combustion chamber, such as running in a shoe, are prevented. Both measures improve the operational reliability of the internal combustion engine. Drawings

[0004] Exemplary embodiments of the invention are shown in the drawing and explained in more detail in the following description.

[0005] It shows: Fig. 1 an internal combustion engine, with oil cooling, a knock sensor and an evaluation unit. Description

[0006] Fig.Figure 1 schematically shows an internal combustion engine 1 with a cylinder and a piston 3 arranged therein. The piston 3 moves up and down within the cylinder 2, a motion which is transmitted to a crankshaft 11 via a connecting rod 10. This is therefore a typical Otto or diesel internal combustion engine. For the sake of simplicity, common technical details of such internal combustion engines, such as air intake and exhaust routing, air inlet and exhaust valves, fuel injection, and spark plugs, are not shown, as they are also irrelevant to understanding the invention.

[0007] To ensure increased cooling of the piston 3 in certain operating ranges of the internal combustion engine 1, an oil cooling system 4 is provided for the piston 3. The oil cooling system 4 comprises an injection nozzle 7, a valve 6, and a pump 5. The pump 5 supplies the oil required for cooling under pressure, so that the injection nozzle 7 injects the oil onto the underside of the piston 3. This oil provides additional cooling of the piston 3 and thus enables improved operation of the internal combustion engine 1, particularly under operating conditions that result in high engine power output. Under other operating conditions, especially low engine power output or overrun operation, the use of the oil cooling system 4 is disadvantageous, as some of the injected oil can enter the combustion chamber above the piston 3 and be burned. This worsens the emissions of the internal combustion engine.This can lead to an undesirable increase in the power output of the internal combustion engine 1.

[0008] It is therefore planned to use the oil cooling system 4 in certain operating ranges of the internal combustion engine 1 and to deactivate it in other operating ranges. A valve 6 is therefore provided between the oil pump 5 and the injection nozzle 7, which is designed as a particularly simple mechanically switchable valve 6. The valve 6 is controlled by selecting a corresponding oil pressure, which is set by controlling the operation of the oil pump 5. At an increased pressure from the pump 5, the valve 6 opens, and at a decreased pressure, the valve 6 closes. By controlling the pressure generated by the pump 5, the valve 6 can thus be opened and closed.

[0009] Each time the valve 6 opens and closes, a movable element of the valve 6 is moved by the increasing or decreasing oil pressure until the movement of the movable element is limited by a stop, both for opening and closing. The movement of the movable element of the valve 6 generates an acoustic signal each time it encounters the stop, thus indicating that the valve has switched. Switching, in this context, refers to each change in the state of the valve, that is, a change from closed to open or from open to closed. Each of these changes in state, i.e., each switching, generates an acoustic signal.

[0010] According to the invention, this switching of the valve is detected by a knock sensor 8, which is mounted on the outside of the internal combustion engine 1. Each switching of the valve 6 generates an acoustic signal, in particular a structure-borne sound signal in the internal combustion engine 1 and especially on the outside of the cylinder 2, which can be measured by the knock sensor 8. Such knock sensors 8 are already provided in a multitude of internal combustion engines 1 to detect knocking combustion. Such knocking combustion causes impermissible pressure peaks in the combustion chamber of the internal combustion engine 1, which can lead to damage to the internal combustion engine 1. The signals from the knock sensor 9 are evaluated by a control unit 9, which is connected to the knock sensor 8 via a data line. Furthermore, the control unit 9 also controls the pump 5 via another data line and thus regulates the pressure of the oil for oil cooling.

[0011] The knocking signals of combustion occur at specific times, particularly close to the top dead center of piston 3's movement, where combustion in the internal combustion engine 1 ignites. The acoustic signals from valve 6 always occur when valve 6 switches, which can be clearly distinguished temporally from the occurrence of the knocking signals. The signals from the knock sensor 8 can therefore also be used to determine whether or not valve 6 switches. If pump 5 is activated to increase the pressure sufficiently to cause valve 6 to switch and open, an acoustic signal from valve 6 is to be expected within a specific time window after this activation.Similarly, when the pump is activated to reduce the pressure, causing valve 6 to close, an acoustic signal indicating that valve 6 has switched to the closed state is to be expected within a specific time window. By evaluating this acoustic signal, particularly in the time domain, it can be determined whether valve 6 has switched.

[0012] Furthermore, it can be evaluated whether the switching occurred at the expected time, or slightly too early or slightly too late. This also allows for a conclusion or diagnosis as to whether any deterioration or aging of valve 6 has occurred.

[0013] Furthermore, the amplitude of the acoustic signal can be evaluated. A deviation in the amplitude of the acoustic signal can also indicate a deterioration or aging of the properties of valve 6.

[0014] Furthermore, the absence of a switching signal can indicate whether valve 6 is stuck in a switching state, for example, whether valve 6 is permanently open or permanently closed. The operation of the internal combustion engine 1 can then be adjusted accordingly.

[0015] If valve 6 is permanently closed, piston 3 cannot be cooled by oil cooling 4. In such an operating condition, the thermal load on the internal combustion engine 1 should be reduced, for example by limiting the engine's power output.

[0016] If valve 6 is permanently open, oil is continuously injected or flows into the area below piston 3. During operation with lower power output or engine braking, some of this additional oil introduced below piston 3 can be drawn into the combustion chamber of engine 1 and burned there. This leads to a deterioration of the exhaust gases from the engine or an undesirable increase in power output. Therefore, the overrun fuel cut-off mode, in particular, could be disabled with valve 6 permanently open to prevent unwanted oil intake into the combustion chamber of engine 1. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2009 057 549 A1

[0001]

Claims

[1] Method for controlling an internal combustion engine having at least one cylinder and a piston arranged therein, wherein an oil cooling system is provided for the piston, wherein the flow of oil through the oil cooling system to the piston is controlled by means of a valve, characterized by , that switching of the oil cooling valve is monitored by evaluating an acoustic signal, and that in the event of a faulty switching of the oil cooling valve, the control of the internal combustion engine is affected. [2] Method according to claim 1, characterized by , that the evaluation of the acoustic signal of the oil cooling valve is carried out by a knock sensor arranged on the internal combustion engine. [3] Method according to any one of the preceding claims, characterized by , that the switching of the oil cooling valve is achieved by adjusting the pressure of the oil switched by the valve. [4] Method according to any one of the preceding claims, characterized by, that an acoustic signal for the opening of the valve is monitored. [5] Method according to any one of the preceding claims, characterized by , that an acoustic signal for the closing of the valve is monitored. [6] Method according to any one of the preceding claims, characterized by , that a time at which the acoustic signal occurs is evaluated. [7] Method according to any one of the preceding claims, characterized by , that the amplitude of the acoustic signal is evaluated. [8] Method according to any one of the preceding claims, characterized by , that if the valve fails to open, the performance of the internal combustion engine will be limited. [9] Method according to any one of the preceding claims, characterized by , that if the valve fails to close properly, overrun fuel cut-off of the internal combustion engine will not be permitted. [10] Device for controlling an internal combustion engine having at least one cylinder and a piston arranged therein, wherein an oil cooling system is provided for the piston, wherein the flow of oil through the oil cooling system to the piston is switched by means of a valve, characterized by , that the device monitors the switching of the oil cooling valve by evaluating an acoustic signal, and that in the event of a faulty switching of the oil cooling valve, the device influences the control of the internal combustion engine.

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