WO2011141130A1 - Method for operating an internal combustion engine having a multi-stage oil pump - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine, wherein in an oil circuit (14) of the internal combustion engine, in particular for forced-feed lubrication, a first oil pressure stage having a first minimum and maximum oil pressure level and at least one second oil pressure stage having a second minimum and maximum oil pressure level are alternatively produced by an oil pump (12), wherein the first minimum oil pressure level is less than or equal to the second minimum oil pressure level and the first maximum oil pressure level is less than the second maximum oil pressure level, wherein a camshaft (16) of the internal combustion engine is hydraulically adjusted by an actuator (18) by means of an oil pressure from the oil circuit (14) of the internal combustion engine. During the adjustment, a first adjustment speed of the camshaft (16) is set by the actuator (18) while the first oil pressure stage is produced by the oil pump (12), wherein a second adjustment speed of the camshaft (16) is set by the actuator (18) for at least one second oil pressure stage while the second oil pressure stage is produced by the oil pump (12), wherein at least one difference between the first and at least one second adjustment speed is determined, wherein a switching mechanism (20) of the oil pump (12) for switching between the oil pressure stages is classified as being in order if a magnitude of the difference is greater than or equal to a predetermined difference value, and the switching mechanism (20) of the oil pump (12) for switching between the oil pressure stages is classified as defective if a magnitude of the difference is less than a predetermined difference value.

Description

 description

Method for operating an internal combustion engine

 with multi-stage oil pump

The invention relates to a method for operating an internal combustion engine, wherein in an oil circuit of the internal combustion engine, in particular for pressure circulation lubrication, a first oil pressure stage with a first minimum and maximum oil pressure level and at least one second oil pressure stage with a second minimum and maximum oil pressure level is generated by an oil pump, wherein the first minimum oil pressure level is less than or equal to the second minimum oil pressure level and the first maximum oil pressure level is less than the second maximum oil pressure level, wherein a camshaft of the internal combustion engine of an actuator hydraulically by means of an oil pressure from the oil circuit of the

Internal combustion engine is adjusted, according to the preamble of patent claim 1.

Internal combustion engines usually have a mechanically driven oil pump. In some applications, it is by a corresponding actuator or a

Shift mechanism possible to approach two or more pressure levels with this oil pump with different oil pressure level or different value ranges in which the oil pressure moves depending on the operating condition of the internal combustion engine. The oil pump has a mechanically acting device for regulating the oil pressure. The internal combustion engine does not require the same, high oil pressure in each operating map point. Usually, the oil pressure can be lowered to low speeds and loads. Only when a corresponding, predetermined load and speed threshold is exceeded is switched to the higher second pressure level. The oil pressure is thus adapted to the current needs of the internal combustion engine. The power consumption of such a two-stage or multi-stage oil pump compared to a single-stage oil pump is lower. A problem of the two-stage oil pump is the diagnosis of the actuating mechanism. For this purpose, it is known to use a separate oil pressure sensor for each pressure stage. The two or

multistage oil pump therefore requires at least one additional pressure sensor. This additional sensor requires corresponding costs and requires space.

CONFIRMATION COPY The monitoring of an oil pressure by means of a pressure sensor is known for example from DE 10 2005 050 775 A1. In an engine oil circuit for an internal combustion engine, a pressure sensor is spatially integrated into a hydraulic component. As a result, an otherwise usual pressure switch for monitoring an existing minimum pressure accounts, since the

Output signal of the integrated pressure sensor can be used for pressure monitoring.

From DE 198 25 288 A1 discloses an internal combustion engine is known in which a

Camshaft adjuster (actuator for adjusting the camshaft) a hydraulic

Has wing actuator, which rotates the camshaft relative to the crankshaft and this is acted upon by an electrically actuated hydraulic valve with engine oil from the engine oil circuit.

From US 5 529 023 it is known to monitor the operability of a camshaft adjuster based on an adjustment angle of the camshaft adjustment. Becomes a

predetermined adjustment angle is not reached, a defect in the camshaft adjuster is assumed. However, this monitoring is suspended when an oil pressure in a camshaft adjuster supplying oil circuit is lower than a predetermined value. In this case, the camshaft adjustment is exposed to itself.

The invention is based on the object, a method of o.g. Kind regarding the

Simplify component complexity while improving the monitoring of the operability of the switching mechanism of the oil pump.

This object is achieved by a method of o.g. Art solved with the features characterized in claim 1. Advantageous embodiments of the invention are described in the further claims.

For this purpose, it is provided according to the invention in a method of the aforementioned type that a first adjustment speed of the camshaft is determined by the actuator, while the first oil pressure stage is generated by the oil pump, wherein for at least one second oil pressure stage, a second adjustment speed of the camshaft is determined by the actuator while the second oil pressure stage is generated by the oil pump, wherein at least a difference between the first and at least a second adjustment speed is determined, wherein a switching mechanism of the oil pump for switching between the oil pressure levels is classified as good, if an amount of difference equal to or greater as a predetermined differential value, and the switching mechanism of the oil pump for switching between the oil pressure levels is classified as defective when an amount of the difference is smaller than a predetermined difference value.

This has the advantage that a functionality of the switching mechanism of the oil pump is monitored without additional hardware exclusively with existing sensors, the monitoring is independent of tolerances on oil viscosity, the oil pump, the actuator or a valve of the actuator in the oil circuit.

An independent of the operating condition of the internal combustion engine monitoring of

Functionality of the switching mechanism of the oil pump without compensation, for example, by speed or load-related fluctuations in the oil pressure is achieved in that the first and at least a second adjustment speed at an identical

Operating condition of the internal combustion engine can be determined.

Additional monitoring of the operability of the oil pump itself is achieved in that in an operating state of the internal combustion engine, during which the first oil pressure stage is generated by the oil pump, the oil pressure is monitored by a pressure sensor.

An active diagnosis of the switching mechanism of the oil pump for the various

Oil pressure levels are achieved in that after determining the first

Adjusting the oil pump independently of the current operating state of the internal combustion engine switched to at least a second oil pressure stage, the camshaft adjusted and thereby the second adjustment speed is determined.

A check of the switching mechanism of the oil pump for the different oil pressure levels at defined states of the internal combustion engine is achieved by the fact that the first and the second adjustment speed at least one predetermined operating point of the

Internal combustion engine can be determined, regardless of the operating point, the respective oil pressure level is switched and the camshaft is adjusted.

In order to comply with pollutant limit values for the internal combustion engine, the at least one predetermined operating point of the internal combustion engine is selected such that a miriimale increase of pollutant emissions in the exhaust gas results.

The invention will be explained in more detail below with reference to the drawing. This shows in 1 is a schematic block diagram of an internal combustion engine for carrying out the method according to the invention,

Fig. 2 is a flow chart of a preferred embodiment of the invention

 Procedure and

Fig. 3 shows an operating map for an internal combustion engine.

The invention relates to an internal combustion engine, as shown schematically in Fig. 1, with an engine block 10, an oil pump 12 and a Mötorölkreislauf 14, which is in particular designed for circulation pressure lubrication. In the Mötorölkreislauf 14 for circulating pressure lubrication controllable hydraulic components are connected, the necessary for their operation operating fluid is provided by the engine oil of the engine oil circuit 14. The regulation of the fluid flow, that is, the hydraulic component flowing through the engine oil flow is effected by electrical control signals of a control electronics 22. Such, controllable

Hydraulic component is a hydraulic camshaft adjuster 18 for adjusting a camshaft 16 with a hydraulic valve, which is designed for example as a solenoid valve. In other words, the actuator for the camshaft adjustment is integrated into the Mötorölkreislauf.

The pressure prevailing in the Mötorölkreislauf oil pressure is provided by the mechanically driven oil pump 12 in the Mötorölkreislauf 14 available. The oil pump 12 has a

Switching mechanism 20 to switch between different oil pressure levels. Here, a first oil pressure stage is provided, wherein the oil pressure in response to a

Operating condition of the internal combustion engine in a first range between a first minimum oil pressure value (oil pressure level) and a first maximum oil pressure value

(Oil pressure level) fluctuates. Furthermore, at least one second oil pressure stage is provided in which the oil pressure fluctuates in a second range between a second minimum oil pressure value (oil pressure level) and a second maximum oil pressure value (oil pressure level) depending on an operating condition of the internal combustion engine. Here, the first minimum oil pressure value is less than or equal to the second minimum oil pressure value, and the first maximum oil pressure value is smaller than the second maximum oil pressure value. For the first oil pressure stage, an oil pressure sensor 24 is provided for monitoring the oil pressure. Depending on the level of oil pressure, the camshaft adjustment varies at different speeds. The resulting angular velocity correlates with the oil pressure. The angular velocity can be measured by passing through a sufficient adjustment range with maximum activation of the solenoid valve of the camshaft adjuster 18. The angular velocity is additionally dependent on the engine speed and oil temperature and should be corrected via this. It is typically in a range that is well and safely measurable with devices available in engine controls.

According to the invention, it is provided to use the angular velocity of the camshaft adjustment for monitoring the switching mechanism 20 of the oil pump 12 for different oil pressure levels. Due to the tolerance chain regarding, in particular, oil viscosity,

Pump characteristics, camshaft adjuster 18 and solenoid valve will not only the

Angular velocity determined in the not observable by the remaining oil pressure sensor second oil pressure stage. Rather, it is inventively provided even at the first Ödruckstufe. i.e. So in both pressure stages, the angular velocity of

Camshaft adjustment to measure or determine. Is the difference in the

Angular velocities are sufficiently pronounced, i. greater than or equal to one

predetermined threshold, it can be assumed that the

Switching mechanism 20 of the oil pump 12 is working properly. The first, low

Oil pressure level is monitored by the pressure sensor. The second pressure stage is monitored by comparing the above described comparison of the measured adjustment speed of the

Camshaft adjusting device 18 is evaluated at different oil pressure levels. If the speed of the camshaft adjustment is identical in both oil pressure stages, it can be assumed that the switching mechanism 20 of the oil pump 12 is not working properly. The oil pump 12 can only set a pressure or an oil pressure stage in this case.

In a preferred embodiment of the method according to the invention, first the first and then the second oil pressure stage are driven at a constant operating point. The term "constant operating point" here refers to an operating state of the internal combustion engine in which not necessarily one of the second, higher oil pressure stages and also not necessarily a camshaft adjustment is required. In other words, the oil pressure stage and the camshaft adjustment are independent of the current

Operating state of the internal combustion engine adjusted or changed. In both pressure stages, the adjustment speed of the camshaft adjustment is measured or determined and evaluated or determines the difference. The dependencies to the oil temperature and the

Last speed point are excluded in this way. The impact on the Emissions due to the non-optimal camshaft position during the measurement are taken into account by a suitable choice of the constant operating point.

The cost or installation space disadvantage of a second oil pressure sensor for the second oil pressure stage can be saved because no additional oil pressure sensor is required for monitoring whether the second pressure level is reached. A cost neutrality is achieved because the diagnosis of the second oil pressure stage is based on already existing in the internal combustion engine actuators and sensors.

FIG. 2 shows by way of example a flow diagram of a preferred embodiment of the method according to the invention. In a first step 100 will be

Incoming conditions for the procedure checked. For example, it is checked whether a load, a rotational speed and a temperature of a coolant and the engine oil are in a predetermined range. If this is not the case even for one of the aforementioned parameters, the diagnosis of the camshaft is not carried out and jumped back to step 100 via a first branch 102 "no".

If all tested parameters are within a predetermined range, then a second branch 104 "yes" is used to jump to a second step 106 "oil pump in pressure stage 1 => requirement camshaft desired jump". In this second step 106, the oil pump is operated in such a way that it provides a first pressure stage and the camshaft is adjusted. In a third step 108 "camshaft measurement" is a

Adjustment speed 1 of the camshaft during adjustment determined as angular velocity ω [ms] for the first pressure stage. In a fourth step 110 "oil pump in

Pressure level 2 => request camshaft desired jump ", the oil pump is operated such that it provides a second pressure level in the Öikreislaufsystem the internal combustion engine, wherein the pressure in Öikreislaufsystem the internal combustion engine pressure is different from the corresponding pressure at the first pressure stage, and it is In a fifth step 112 "Camshaft measurement", an adjustment speed 2 of the camshaft during the adjustment is determined as the angular speed ω [ms] for the second pressure stage, in a sixth step 114

"Verstellgeschwindigkeit 2> Verstellgeschwindigkeit 1" is checked whether the

Adjustment speed 2 for the second pressure stage is greater than the adjustment speed 1 for the first pressure stage. If the oil pump or the actuator for the pressure stages works correctly and generates a higher pressure in the Öikreislaufsystem the internal combustion engine in the second pressure stage than in the first pressure stage, the adjustment speed must. 2 Thus, conversely, this is an indication of a correctly working oil pump or switching between the pressure levels. Therefore, from the sixth step 114 via a third branch 118, "yes" is entered to a seventh step 116 "Test completed, oil pump pressure stage actuator OK", if in step 114 the result of the test is "Verstellgeschwindigkeit 2> Verstellgeschwindigkeit 1?" yes is. If this is not the case, however, then a fourth branch 120 "no" to an eighth step 122 "test completed, actuator for pressure stages of the oil pump is not in order" jumped.

FIG. 3 illustrates an operating map of an internal combustion engine, wherein a rotational speed n of the internal combustion engine is plotted on a horizontal axis 200 and an engine torque M or a load is plotted on a vertical axis 202. In this so-called "load speed map" results in an operating range for the internal combustion engine, which is limited by a first graph 204, the horizontal axis 200 and the vertical axis 202. Within this operating range of the internal combustion engine, there is a first

Map area 206, in which the first and second pressure stage of the oil pump can be driven. Within this first map area 206, there is a second map area 208, in which the diagnostic method described above can be performed, for which the following conditions must be fulfilled: both pressure levels must be permissible, an influence on the exhaust gas by the position jump of the camshaft must be low and An influence on the driving behavior of a vehicle equipped with the internal combustion engine by the position jump of the camshaft must be low. All of this is in the second

Map area 208 is satisfied. The rest of the operating range outside the first

Map area 206 is a third map area 210 in which only the second pressure stage can be driven. For this reason, this third map area 210 is not suitable for the diagnostic method described above.

LIST OF REFERENCE NUMBERS

block

oil pump

Oil circuit

camshaft

actuator

Switching mechanism of the oil pump for switching between the oil pressure levels control electronics

Oil pressure sensor

First step: Check the entry conditions for the procedure

Branch: "no"

Branch: "yes"

second step: oil pump in pressure stage 1 => request camshafts desired jump third step: Camshaft measurement

4th step: oil pump in pressure stage 2 => request camshaft nominal jump fifth step: camshaft measurement

sixth step "Adjustment speed 2> Adjustment speed 1

seventh step: test completed, actuator for pressure stages of the oil pump in order third branch "yes"

fourth second: "no"

Eighth step: Test completed, actuator for pressure stages of the oil pump out of order

horizontal axis: speed n

vertical axis: motor torque M

first graph

first map area

second map area

third map area

Claims

 claims Method for operating an internal combustion engine, wherein in an oil circuit of the internal combustion engine, in particular for pressure circulation lubrication, of an oil pump optionally a first oil pressure stage with a first minimum and maximum Oil pressure level and at least a second oil pressure stage with a second minimum and maximum oil pressure level is generated, wherein the first minimum oil pressure level is less than or equal to the second minimum oil pressure level and the first maximum oil pressure level is less than the second maximum oil pressure level, wherein a Camshaft of the internal combustion engine is hydraulically adjusted by an actuator by means of an oil pressure from the oil circuit of the internal combustion engine, characterized characterized in that a first adjustment speed of the camshaft is determined by the actuator, while the first oil pressure stage is generated by the oil pump, wherein for at least one second oil pressure stage, a second adjustment speed of the camshaft is determined by the actuator, while the second oil pressure stage is generated by the oil pump , wherein at least one difference between the first and at least one second adjustment speed is determined, wherein a The switching mechanism of the oil pump for switching between the oil pressure levels is classified as an order when an amount of the difference is equal to or greater than a predetermined differential value, and the switching mechanism of the oil pump for Switching between the oil pressure stages is judged to be defective when an amount of the difference is smaller than a predetermined difference value. A method according to claim 1, characterized in that the first and at least one second adjustment speed in an identical operating state of Internal combustion engine to be determined. Method according to at least one of the preceding claims, characterized characterized in that in an operating state of the internal combustion engine, during which the first oil pressure stage is generated by the oil pump, the oil pressure is monitored by a pressure sensor. 4. The method according to at least one of the preceding claims, characterized in that after determining the first adjustment speed, the oil pump independently of the current operating state of the internal combustion engine switched to at least a second oil pressure stage, the camshaft adjusted and thereby the second adjustment speed is determined. 5. The method according to at least one of the preceding claims, characterized  characterized in that the first and the second adjustment speed are determined at least one predetermined operating point of the internal combustion engine, wherein independently of the operating point, the respective oil pressure level is switched and the camshaft is adjusted. 6. The method according to claim 5, characterized in that the at least one  predetermined operating point of the internal combustion engine is selected such that there is a minimal increase of pollutant emissions in the exhaust gas.