Method and arrangement for controlling an internal combustion engine, comprising at least two control units

Abstract

A method for controlling an internal combustion engine, wherein a first engine control device generates a control signal to actuate a function of the engine. A switchover device transmits the control signal of the first control device to the engine to actuate the function of the engine. The first control device transmits a sign-of-life signal which indicates functionality of the control device to the switchover device. The first engine control device does not transmit the sign-of-life signal or transmits the signal incorrectly if a fault occurs which endangers proper actuation of the function of the engine by the first engine control device. If the sign-of-life signal of the first engine control device is not or is incorrectly received by the switchover device, the switchover device stops transmitting the control signals of the first engine control device and starts transmitting a control signal generated by a second engine control device to the engine to actuate the function of the engine.

Claims

1. A method for controlling an internal combustion engine, comprising the steps of: generating at least one control signal with a first engine control unit to actuate at least one function of the internal combustion engine; passing along the at least one control signal of the first engine control unit to the internal combustion engine by a switchover device for actuating the at least one function of the internal combustion engine; transmitting a sign-of-life signal indicating functionality of the first engine control unit continuously or periodically from the first engine control unit to the switchover device; wherein the first engine control unit does not transmit the sign-of-life signal or does not transmit the signal correctly when an error occurs that puts at risk proper actuation of the at least one function of the internal combustion engine by the first engine control unit; and wherein the switchover device stops passing along the control signal of the first engine control unit to the internal combustion engine and begins passing along at least one control signal generated by a second engine control unit for actuation of the at least one function of the internal combustion engine to the internal combustion engine when the sign-of-life signal of the first engine control unit is not being received or is not being received correctly by the switchover device, wherein, during operation of the internal combustion engine, the second engine control unit continuously generates the at least one control signal, even when the control signal is not being passed along by the switchover device to the internal combustion engine.

2. The method according to claim 1, wherein the first engine control unit transmits to the second engine control unit data necessary for actuating the at least one function of the internal combustion engine a single time after or at starting of the internal combustion engine, periodically or as needed; or wherein data necessary for actuating the at least one function of the internal combustion engine are stored in the second engine control unit, and the data are called up when the actuation of the at least one function of the internal combustion engine is switched over to the second engine control unit.

3. The method according to claim 2, wherein the first engine control unit transmits the data to the second engine control unit after a change in the data.

4. The method according to claim 1, wherein the second engine control unit transmits a sign-of-life signal indicating functionality of the second engine control unit continuously or periodically to the switchover device or to the first engine control unit.

5. The method according to claim 1, wherein the second engine control unit monitors a continuously generated control signal in order to detect whether or not said second control unit is actuating the at least one function of the internal combustion engine.

6. The method according to claim 5, wherein the second engine control unit initializes parameters for the actuation of the at least one function of the internal combustion engine with stored values or releases retained values of the parameters for variation when the second engine control unit recognizes that it is actuating the at least one function of the internal combustion engine.

7. The method according to claim 5, wherein the second engine control unit generates a voltage, based on which a current flows when the second engine control unit is actuating the at least one function of the internal combustion engine, wherein no current flows when the control signal is not being passed along by the switchover device to the internal combustion engine; wherein the second engine control unit monitors whether or not a current is flowing; wherein the second engine control unit actuates a suction throttle; and wherein the second engine control unit monitors the current flowing from the second engine control unit through the suction throttle.

8. The method according to claim 7, wherein the second engine control unit monitors whether or not the current is exceeding a previously determined threshold value.

9. The method according to claim 7, wherein the second engine control unit continuously actuates the suction throttle.

10. The method according to claim 1, wherein the first or the second engine control unit actuates an actuator system of the internal combustion engine.

11. The method according to claim 10, wherein the actuator system includes at least one injector and/or at least one suction throttle.

12. A switchover device for use in controlling an internal combustion engine wherein the switchover device can be brought into functional connection with a first engine control unit, with a second engine control unit, and with an internal combustion engine; wherein the switchover device is configured to pass along at least one control signal from the first engine control unit or from the second engine control unit to the internal combustion engine; wherein the switchover device is operative to switch over from passing along the signal of the first engine control unit to passing along the signal of the second engine control unit; wherein the switchover device is configured to receive a sign-of-life signal from the first and/or from the second engine control unit, wherein, during operation of the internal combustion engine, the second engine control unit continuously generates the at least one control signal, even when the control signal is not being passed along by the switchover device to the internal combustion engine; and wherein the switchover device is configured so as to stop passing along the at least one control signal of the first engine control unit to the internal combustion engine and starts passing along the at least one control signal of the second engine control unit to the internal combustion engine when the sign-of-life signal of the first engine control unit is not being received or is not being received correctly by the switchover device.

13. The switchover device according to claim 12, wherein the switchover device comprises at least one switch.

14. The switchover device according to claim 13, wherein the switch is a semiconductor switch or an electromechanical switch.

15. The switchover device according to claim 14, wherein the switch is a relay.

16. The switchover device according to claim 12, further comprising anti-interrupt means that permits the switchover device to continue to send at least one control signal to the internal combustion engine during a switchover between the engine control units.

17. An arrangement for controlling an internal combustion engine, comprising: a first engine control unit; a second engine control unit; and a switchover device wherein the first engine control unit and the second engine control unit are set up to generate control signals to actuate at least one function of the internal combustion engine, wherein the switchover device brings the first engine control unit and the second engine control unit into functional connection with the internal combustion engine and passes along the control signals to the internal combustion engine, wherein the first engine control unit is set up to generate and transmit a sign-of-life signal indicating functionality of the first engine control unit, wherein the first engine control unit is set up so that the sign-of-life signal is not or is not correctly generated and/or transmitted when an error occurs which puts at risk a proper actuation of the at least one function of the internal combustion engine by the first engine control unit, wherein the first engine control unit is functionally connected to the switchover device so that the sign-of-life signal is received by the switchover device, and wherein the switchover device is configured to stop passing along the at least one control signal of the first engine control unit to the internal combustion engine and to begin passing along the at least one control signal of the second engine control unit to the internal combustion engine when the sign-of-life signal of the first engine control unit is not being received or is not being correctly received by the switchover device, wherein, during operation of the internal combustion engine, the second engine control unit continuously generates the control signal, even when the control signal from the second engine control unit is not being passed along by the switchover device to the internal combustion engine.

18. An internal combustion engine comprising an arrangement according to claim 17.

19. The internal combustion engine according to claim 18, wherein the internal combustion engine is configured as a common-rail engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is explained in greater detail below on the basis of the drawings:

(2) FIG. 1 shows a schematic diagram of an exemplary embodiment of an arrangement for controlling an internal combustion engine;

(3) FIG. 2 shows a flow chart representing one embodiment of the method for controlling an internal combustion engine;

(4) FIG. 3 shows a schematic automatic control diagram for a preferred embodiment of the method; and

(5) FIG. 4 shows a schematic diagram of an exemplary embodiment of an arrangement, wherein a switchover device comprises an anti-interrupt means.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 shows a schematic diagram of an exemplary embodiment of an arrangement 1 for controlling an internal combustion engine 3. The arrangement 1 comprises a first engine control unit 5, a second engine control unit 7, and a switchover device 9.

(7) The first engine control unit 5 and the second engine control unit 7 are able to generate control signals, which serve to actuate at least one function of the internal combustion engine, preferably to control and/or to automatically control a plurality of functions or the entire internal combustion engine. The first engine control unit 5 is functionally connected by a functional connection 11 to the switchover device 9, the second engine control unit 7 being connected to it by a functional connection 13, these connections allowing the control signals from each control unit to be transmitted to the switchover device. The switchover device 9 is functionally connected to the internal combustion engine 3 by a third functional connection 15 for passing along the control signals to the engine. At any one time, the switchover device 9 passes along the control signals of only one of the two engine control units 5, 7 to the internal combustion engine 3.

(8) In the exemplary embodiment shown here, each of the engine control units 5, 7 generates a sign-of-life signal, which indicates its functionality, wherein, in the case of the first engine control unit 5, it is transmitted by way of a fourth functional connection 17 and, in the case of the second engine control unit 7, by way of a fifth functional connection 19, to the switchover device 9.

(9) So that the second engine control unit 7 has available all of the data necessary for actuation of the at least one function of the internal combustion engine 3, in particular for its control or automatic control, the first engine control unit 5 is preferably functionally connected to the second engine control unit 7 by way of a fieldbus 21, so that the data can be transmitted from the first engine control unit 5 to the second engine control unit 7 a single time, namely, when the internal combustion engine 3 is being started or immediately thereafter, periodically, or as needed, in particular after a change in the data.

(10) In the exemplary embodiment shown here, it is provided that the first engine control unit 5 is used as the primary control unit. After the internal combustion engine 3 has been started, the switchover device 9 passes along the control signals generated by the first engine control unit 5 to the internal combustion engine 3 as long as it, i.e., the switchover device, is receiving the sign-of-life signal from that control unit. At the same time, the second engine control unit 7 also preferably generates all of the control signals necessary for actuation, but the switchover device 9 does not pass them along to the internal combustion engine 3. The second engine control unit 7, in the exemplary embodiment shown there, is used as a backup control unit, which is redundant to the first engine control unit 5 and, in the event of an error, can take over the job of actuating the at least one function of the internal combustion engine 3 or the automatic control of that function.

(11) The way in which the arrangement 1 functions will now be explained on the basis of the flow chart of FIG. 2, which represents a schematic diagram of a preferred embodiment of the method for controlling the internal combustion engine 3. At regular intervals, i.e., preferably after predetermined time intervals, or continuously, the first engine control unit 5 checks for the presence of an error or malfunction which puts at risk the proper actuation of the at least one function of the internal combustion engine 3. As long as no such error or malfunction is present, the first engine control unit 5 generates the sign-of-life signal correctly and sends this signal to the switchover device 9 in a step S2. The switchover device 9 passes along the control signals of the first engine control unit 5 to the internal combustion engine 3, so that the engine, in a step S3, is controlled and/or automatically controlled by the first engine control unit 5 at least with respect to the at least one function.

(12) If, however, an error or a malfunction does occur, or if the first engine control unit 5 fails completely, the control unit stops generating and/or transmitting the sign-of-life signal or stops correctly generating and/or transmitting it in a step S10. The sign-of-life signal of the first engine control unit 5 is then no longer received or is no longer received correctly by the switchover device 9, as a result of which, in a step S11, the switchover device is caused to stop passing along the control signals of the first engine control unit 5 to the internal combustion engine 3 and instead to begin passing along the control signals generated and transmitted by the second engine control unit 7 to the internal combustion engine 3 to control and/or automatically to control it at least with respect to the at least one function. From that point on, the second engine control unit 7, in a step S12, controls and/or automatically controls the internal combustion engine 3 at least with respect to the at least one function.

(13) The method illustrated by the flow chart according to FIG. 2 is preferably carried out in exactly the same way for the second engine control unit 7, as previously explained in conjunction with the first engine control unit 5, when the at least one function of the internal combustion engine 3 is being actuated by the second engine control unit 7. For this purpose, the second engine control unit 7 also preferably generates a sign-of-life signal indicating its functionality and transmits this to the switchover device 9. If then an error or a malfunction occurs in the second engine control unit 7 or if it fails completely, the switchover device 9 can preferably switch back to the first engine control unit 5, if its functionality has been restored after only a temporary error and the sign-of-life signal of the first engine control unit 5 is again being received by the switchover device 9.

(14) FIG. 3 shows a schematic automatic control diagram for a preferred embodiment of the method. Elements which are the same or which serve the same function are designated by the same reference numbers, so that to this extent reference can be made to the preceding description. The diagram according to FIG. 3 describes the redundant automatic control of a controlled variable 23 to maintain it at a nominal value 25. As redundant controllers, the first engine control unit 5 and the second engine control unit 7 are arranged in parallel. Also shown is the switchover device 9, which transmits a control quantity 27 either from the first engine control unit 5 or from the second engine control unit 7 to an actuator 29. This actuator influences a correcting variable 31, which acts on a controlled system 33.

(15) To measure the controlled variable 23 in the embodiment of the method shown or in an exemplary embodiment of the arrangement, two independent measurement elements are provided, namely, a measurement element 33, which is assigned to the first controller or first engine control unit 5, and a second measurement element 35, which is assigned to the second controller or second engine control unit 7. A first actual value 37 of the controlled variable is compared with the nominal value 25, so that a first control deviation 39 is sent to the first controller. The second measurement element 35 determines a second actual value 41, from which, in association with the nominal value 25, a second control deviation 43 is calculated, which is sent to the second controller. It is advantageous for both the controllers and the measurement elements to be configured redundantly, because in this way it is possible again to compensate for errors, malfunctions, or complete failures of sensors by switching over to a parallel automatic control circuit.

(16) As long as the first engine control unit 5 is active as a controller, it sees a closed controlled system, because the control quantity 27 which it generates is passed along by the switchover device 9 to the actuator 29. The second engine control unit 7, however, sees an open automatic control circuit, because there is no functional connection to the actuator 29 as long as the switchover device is passing along the control quantity 27 of the first engine control unit 5 to the actuator. This creates the problem that, over time, the integral components in the second engine control unit 7 take on values which are not usable for the automatic control of the controlled variable 23. To solve this problem, one of the previously described alternative procedures is implemented when control is switched over to the second engine control unit 7.

(17) In a preferred embodiment of the method, the controlled quantity 23 is the rpm's of the internal combustion engine or the speed of a vehicle driven by the internal combustion engine. The actuator 29 in this case is at least one injector. Preferably all of the injectors of the internal combustion engine are used as actuators. Alternatively, the controlled quantity 23 is preferably the pressure in a high-pressure accumulator of an injection system of the internal combustion engine, in particular the automatic pressure controller for the rail of an internal combustion engine configured as a common-rail diesel engine. The actuator 29 in this case is the suction throttle on a high-pressure pump, the opening of which is varied to control the rail pressure.

(18) Another embodiment of the method is also preferred in which the first engine control unit 5 or the second engine control unit 7 automatically control both the rpm's or the speed of the internal combustion engine and the high pressure for an injection system. In this case, the diagram according to FIG. 3 is to be, as it were, duplicated; i.e., the first engine control unit 5 and the second engine control unit 7 each generate two control quantities, namely, a first for actuating the at least one injector and a second for actuating the suction throttle. Thus separate measurement elements for the rpm's or speed on the one hand and for the high pressure on the other hand are also provided. In addition, the engine control units 5, 7 each comprise, correspondingly, two inputs for two control deviations in the two automatic control circuits.

(19) It has been found that a switchover from the first engine control unit 5 to the second engine control unit 7 must be executed within a very short time period, preferably within a time interval of less than 100 ms, to prevent the internal combustion engine from stalling because, for example, no fuel or not enough fuel is being injected or because the pressure becomes too high. For this purpose it is necessary in particular to supply the suction throttle of the high-pressure pump with current uninterruptedly. To guarantee this, the switchover device 9 comprises preferably an anti-interrupt means.

(20) FIG. 4 shows an exemplary embodiment of an arrangement 1 in which the switchover device 9 comprises such an anti-interrupt means 45. Elements which are the same or which serve the same function are designated by the same reference numbers, so that to this extent reference is made to the preceding description. The first engine control unit 5 and the second engine control unit 7 are configured identically here, so that only the structure of the first engine control unit 5 will be explained in detail. This comprises a switch 47, by which a voltage source 49 can be connected to an output 51, which is connected to a first input 53 of the switchover device 9. As the control quantity, a current flows from the voltage source 49 via the output 51 to the input 53 of the switchover device 9, which transmits it to a suction throttle (not shown) serving as an actuator 29, the opening, i.e., open cross section, of which is controlled by way of the flow of current through a coil 55. The current flows back by way of a first output 57 of the switchover device 9 to an input 59 of the first engine control unit 5. This control unit preferably comprises a measuring device 61 for measuring the current flowing through the coil 55. By means of the measuring device 61, the engine control unit 5 can also decide whether or not it is actuating the throttle valve at the time in question. This is explained in greater detail below in conjunction with the second engine control unit 7. Preferably, however, both engine control units 5, 7 detect whether or not they have the control responsibility at any particular moment, i.e., whether or not they are actuating the actuator system such as the suction throttle. To avoid excessive voltage peaks when the switch 47 is opened, i.e., when the voltage source 49 is cut off from the output 51, a flyback diode 63 is arranged between the output 51 and the input 59 in the known manner.

(21) As previously indicated, the second engine control unit 7 has the same configuration as the first engine control unit 5. Here in particular the measuring device 61 serves to detect whether or not the suction throttle (not shown) is being actuated by the second engine control unit 7. As long as this is not the case, an output 51′ is not connected to the input 53 of the switchover device 9. Neither is an input 59′ of the second engine control unit 7 connected to the output 57 of the switchover device 9. Therefore, although the voltage produced by the voltage source (not shown) of the second engine control unit 7 is present at the output 51′, no current is flowing. To switch over from the first engine control unit 5 to the second engine control unit 7, the switchover device 9 comprises, in the exemplary embodiment shown here, a first switch 65 and a second switch 67. By means of the first switch 65, the connection between the output 51 an the input 53 can be cut, and a connection between the first output 51′ and the input 53 can be established. In similar fashion, the second switch 67 can establish a connection between the input 59′ and the output 57, whereas the connection between the input 59 and the output 57 can be cut. After the switchover has been accomplished, the current circuit of the second engine control unit 7 is closed via the output 51′, the input 53, the coil 55, the output 57, and the input 59′. In this case, the measuring device of the second engine control unit 7 detects the flow of current, which is preferably greater than a previously determined threshold value. On that basis, the second engine control unit 7 recognizes that the actuation of the suction throttle has been switched over to it. The integral components of the second engine control unit 7 are then preferably initialized according to one of the previously described embodiments.

(22) The current must continue to flow through the coil 55 preferably during the switchover from the first engine control unit 5 to the second engine control unit 7, so that the internal combustion engine does not stall or so that the pressure in the high-pressure accumulator does build up excessively. To guarantee this, the switchover device 9 comprises the anti-interrupt means 45, which is configured here as a flyback element 69. This is configured in such a way that that the current circuit remains closed across the flyback element 69; i.e., current continues to flow through the coil 55 via the flyback element 69 while the first switch 65 and the second switch 67 are actuated. The flyback element 69 preferably comprises at least one diode, here three diodes 71/1, 71/2, 71/3.

(23) The anti-interrupt means 45 is preferably configured in such a way that it does not influence the measurement of the current by the measuring device 61 or by the corresponding measuring device in the second engine control unit 7. For this purpose, it is provided in particular that the flyback means 69 is adapted appropriately to the flyback diode 63. In the exemplary embodiment shown here, this is ensured in that three diodes 71/1, 71/2, 71/3 are used in the flyback means 69, whereas, in the first engine control unit 5, and, correspondingly also in the second engine control unit 7, only one flyback diode 63 is provided.

(24) It has been found that the flow of current through the coil 55 correlates with the amount of fuel being delivered through the suction throttle. As a result, the flow of current influences the pressure in the high-pressure accumulator. By means of the anti-interrupt means 45, the flow of current is kept essentially constant even during the switchover, so that the pressure in the high-pressure accumulator also remains essentially constant during the switchover.

(25) Overall it has been found that, by means of the method and the arrangement for controlling an internal combustion engine, it is easily possible to recognize whether or not an engine control unit controlling the internal combustion engine has a malfunction which puts at risk the proper operation of the engine. It is therefore possible to switch over, promptly and seamlessly, from the one engine control unit to the other without causing any relevant disturbance in the operation of the internal combustion engine, wherein the engine would stall. The method, furthermore, is uncomplicated and extremely reliable.