Avoidance of a safety fuel cut-off during partial engine operation

Abstract

A method for operating an internal combustion engine that includes at least two cylinders, includes operating the internal combustion engine in a first operating mode in partial engine operation, in which at least one of the cylinders is not fired, monitoring the internal combustion engine during the partial engine operation for potentially torque-increasing errors, and switching over from the partial engine operation into a full engine operation in which all of the cylinders are fired when a potentially torque-increasing error is detected.

Claims

1. A method for operating an internal combustion engine that includes at least two cylinders, the method comprising: in a first operating mode, operating, by the internal combustion engine, in partial engine operation in which at least one of the at least two cylinders is not fired; monitoring, by processing circuitry, the internal combustion engine, during the partial engine operation, for a potentially torque-increasing error; and responsive to a detection in the monitoring step of the potentially torque-increasing error: tracking, by the processing circuitry, an amount of time lapsed from a time of the detection without removal of the potentially torque-increasing error; responsive to the tracked amount of time exceeding a first threshold time period, executing a control, by the processing circuitry, to switch over operation of the internal combustion engine from the partial engine operation to a full engine operation in which all of the at least two cylinders are fired; and the processing circuitry responding to a case where the switch over has not occurred by a time at which the tracked amount of time exceeds a second threshold time period that is greater than the first threshold time period by executing a control to operate the internal combustion engine with a safety fuel cut-off.

2. The method of claim 1, wherein the potentially torque-increasing error is an injection into the at least one cylinder.

3. The method of claim 2, wherein the monitoring includes checking for an injection into each of the at least two cylinders, generating an actual injection suppression mask based on the checking, and comparing the actual injection suppression mask with an expected injection suppression mask, a deviation detected in the comparing step being a detection of the potentially torque-increasing error.

4. The method of claim 1, wherein the potentially torque-increasing error is an ignition of the at least one cylinder.

5. The method of claim 4, wherein the monitoring includes checking for an ignition in each of the at least two cylinders, generating an actual ignition mask based on the checking, and comparing the actual ignition mask with an expected ignition mask, a deviation detected in the comparing step being a detection of the potentially torque-increasing error.

6. A device for operating an internal combustion engine that includes at least two cylinders, the device comprising: processing circuitry configured to: control the internal combustion engine to operate in a first operating mode in partial engine operation in which at least one of the at least two cylinders is not fired; monitor the internal combustion engine, during the partial engine operation, for a potentially torque-increasing error; and responsive to a detection in the monitoring step of the potentially torque-increasing error: track an amount of time lapsed from a time of the detection without removal of the potentially torque-increasing error; responsive to the tracked amount of time exceeding a first threshold time period, execute a control to switch over operation of the internal combustion engine from the partial engine operation to a full engine operation in which all of the at least two cylinders are fired; and respond to a case where the switch over has not occurred by a time at which the tracked amount of time exceeds a second threshold time period that is greater than the first threshold time period by executing a control to operate the internal combustion engine with a safety fuel cut-off.

7. The device of claim 6, wherein the potentially torque-increasing error is an injection into the at least one cylinder.

8. The device of claim 7, wherein the monitoring includes checking for an injection into each of the at least two cylinders, generating an actual injection suppression mask based on the checking, and comparing the actual injection suppression mask with an expected injection suppression mask, a deviation detected in the comparing step being a detection of the potentially torque-increasing error.

9. The device of claim 6, wherein the potentially torque-increasing error is an ignition of the at least one cylinder.

10. The device of claim 9, wherein the monitoring includes checking for an ignition in each of the at least two cylinders, generating an actual ignition mask based on the checking, and comparing the actual ignition mask with an expected ignition mask, a deviation detected in the comparing step being a detection of the potentially torque-increasing error.

11. A non-transitory computer-readable medium on which are stored instructions executable by a computer processor, the instructions which, when executed by the processor, cause the processor to perform a method for operating an internal combustion engine that includes at least two cylinders, the method comprising: controlling the internal combustion engine to operate in a first operating mode in partial engine operation in which at least one of the at least two cylinders is not fired; monitoring the internal combustion engine, during the partial engine operation, for a potentially torque-increasing error; and responsive to a detection in the monitoring step of the potentially torque-increasing error: tracking an amount of time lapsed from a time of the detection without removal of the potentially torque-increasing error; responsive to the tracked amount of time exceeding a first threshold time period, executing a control to switch over operation of the internal combustion engine from the partial engine operation to a full engine operation in which all of the at least two cylinders are fired; and responding to a case where the switch over has not occurred by a time at which the tracked amount of time exceeds a second threshold time period that is greater than the first threshold time period by executing a control to operate the internal combustion engine with a safety fuel cut-off.

12. A method for operating an internal combustion engine that includes at least two cylinders, the method comprising: in a first operating mode, operating, by the internal combustion engine, in partial engine operation in which at least one of the at least two cylinders is not fired; monitoring, by processing circuitry, the internal combustion engine, during the partial engine operation, for a potentially torque-increasing error; and responsive to a detection in the monitoring step of the potentially torque-increasing error: tracking, by the processing circuitry, an amount of time lapsed from a time of the detection; responsive to the tracked amount of time exceeding a first threshold time period without removal of the potentially torque-increasing error, executing a control, by the processing circuitry, to switch over operation of the internal combustion engine from the partial engine operation to a full engine operation in which all of the at least two cylinders are fired; and responsive to the tracked amount of time exceeding a second threshold time period without removal of the potentially torque-increasing error, executing a control, by the processing circuitry, to operate the internal combustion engine with a safety fuel cut-off, wherein the second threshold time period is greater than the first threshold time period.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic partial diagram of an internal combustion engine, which may be operated according to the present invention.

(2) FIG. 2 is a flowchart that shows a sequence of an example embodiment of the method according to the present invention.

DETAILED DESCRIPTION

(3) FIG. 1 shows an internal combustion engine, for example, of a motor vehicle, in the form of a highly schematic diagram and is generally denoted by reference numeral 10. Internal combustion engine 10 may be operated with the aid of a method according to the present invention.

(4) Internal combustion engine 10 includes two cylinder banks or engine banks 1, 2. Cylinders 11 through 13 (engine bank 1) and 21 through 23 (engine bank 2) are provided in each of engine banks 1, 2. Intake manifold systems 14 and 24, which are configured for supplying fresh air (combustion air) are assigned to each cylinder bank 1, 2. A throttle valve 15 is provided upstream from intake manifold system 14; a throttle valve 25 is provided upstream from intake manifold system 24. With the aid of throttle valves 15 and 25 it is possible to throttle the fresh air stream used to supply engine banks 1, 2. With the aid of intake valves 16 and 27, fresh air may be admitted into cylinders 11 through 13 (engine bank 1) and cylinders 21 through 23 (engine bank 2). Via exhaust valves 17 and 26, a combusted air-fuel mixture or uncombusted fresh air (in the case of deactivated cylinders) may be expelled from cylinders 11 through 13 (engine bank 1) and cylinders 21 through 23 (engine bank 2) into corresponding exhaust gas manifolds 19 and 29.

(5) Fuel may be supplied to cylinders 11 through 13 (engine bank 1) and cylinders 21 through 23 (engine bank 2) via fuel lines 18 and 28 assigned to each of engine banks 1 and 2, respectively. During the partial engine operation, a so-called engine bank injection suppression may occur, so that an introduction of fuel into cylinders 11 through 13 (engine bank 1) and 21 through 23 (engine bank 2) is suppressed during the partial engine operation phases by interrupting the injection, i.e., interrupting the supply of fuel to cylinders 11 through 13 (engine bank 1) and 21 through 23 (engine bank 2) via fuel lines 18 and 28. It should be pointed out that other methods for providing a partial engine operation are also suitable, such as switching off the gas exchange valves.

(6) A control unit 30 is provided which is able to influence a position of throttle valves 15 and 25, an injection of fuel into the cylinders and, if necessary, an ignition (in the case of gasoline engines) via signal lines (not shown) with the aid of control signals 31. Control unit 30 is programmed for carrying out a method according to the present invention, and is able for this purpose to detect a function or a condition of the throttle valves and the cylinders, for example, via inputs 32 which are also connected to corresponding sensors at the throttle valves and cylinders via signal lines (also not shown). In particular, an injection of fuel into the cylinder and an ignition of the cylinder may be detected.

(7) A preferred example embodiment of a method according to the present invention is illustrated in FIG. 2.

(8) The method starts at step 300, in which it is checked if all requirements for carrying out the example method according to the present invention have been satisfied. In particular, this includes whether internal combustion engine 10 is operated in partial engine operation. If the requirements for carrying out the method according to the present invention are present, steps 301 and 302 are implemented in parallel. The steps are used to check the partial engine operation for torque-increasing errors.

(9) In step 301, an ignition pattern test is carried out, and in step 302, an injection suppression pattern test is carried out.

(10) During partial engine operation, the changed activation of the actuators is checked using logical variables defined for this purpose. Relevant to this are ignition and injection, since the active spark plugs and injectors change. After a transition phase (of a few, e.g., 10, ms), a fixed pattern results which must be consistent with the intended pattern. If, for example, every second cylinder is to be fired in ignition sequence, the ignition pattern resulting from it and the injection suppression pattern resulting from it must each be in conformity with a certain expected value. In the control unit, this may be implemented by programming in the following manner.

(11) The mask and the expected value are made up of as many digits as the engine has cylinders. According to the ignition sequence, there is a first cylinder which bears the number 0, and a last cylinder which bears the number “number of cylinders of engine −1” (thus 5 in the case of a six-cylinder engine according to FIG. 1). In the software, the least significant bit stands to the right, so that the pattern is advantageously counted from the right as well.

(12) The typical mask for a six cylinder engine during half-engine operation is thus: 101010.

(13) The value “1” means “suppressed.” It is apparent that each second cylinder 1, 3, 5 (counted from the right) is suppressed and cylinders 0, 2, 4 are fired.

(14) An error could be, for example, that cylinder 1 was not suppressed. The mask then appears as follows: 101000. This error should be detected. In programming, an “unequal” may be readily used for that purpose. If the test result is unequal to the expected value, an error is present and a corresponding error output is set at 301 and 302.

(15) The error outputs are fed to an OR gate 303, which outputs an error if at least one of the inputs indicates an error.

(16) In the error case, a cut-off debounce time T.sub.0 of, for example, 500 ms is activated in step 304, after the end of which the safety fuel cut-off is requested in step 306 if the error continues to be present.

(17) Parallel to this, a switch-over debounce time T.sub.1 of, for example, 100 ms is now also activated in step 305, after the end of which the full engine operation is requested in step 307 if the error continues to be present. Simultaneously, this may be displayed to the driver of the motor vehicle and/or an error may be entered into an error memory.

(18) If full engine operation is assumed in good time after the end of switch-over debounce time T.sub.1, i.e., before the end of cut-off debounce time T.sub.0, the result of this is that the torque-increasing error is no longer present after the end of cut-off debounce time T.sub.0 and step 306 is thus not triggered. The safety fuel cut-off is thus avoided.

(19) In order to quickly achieve the full engine operation after the request in step 307, for example, a special bit in the software may be set in the request, which, when present, causes a normally provided switch-over function to immediately interrupt the half-engine operation.