Device for Controlling an Internal Combustion Engine

Abstract

A device for controlling an internal combustion engine in a motor vehicle, in particular, an electrified hybrid vehicle with a traction electric machine. The internal combustion engine has multiple cylinders, each of which is equipped with at least one outlet valve which can be switched to two stages. An electronic control unit controls: i) suppression of each of a plurality of cylinders of the internal combustion engine for at least one work cycle, wherein the outlet valves are kept closed, ii) actuation of the outlet valves and the inlet valves of the cylinders of the internal combustion engine in a synchronized manner, and iii) after the suppression process has ended, opening of the outlet valve at least in the first cylinder when the inlet valve is closed, and the enclosed gas is pushed out without being injected and ignited.

Claims

1.-4. (canceled)

5. A device for controlling an internal combustion engine in an electrified hybrid vehicle having a traction electric machine, wherein the internal combustion engine has multiple cylinders which are each equipped with at least one exhaust valve switchable in a two-stage manner, wherein: multiple cylinders of the internal combustion engine are each able to be suppressed for at least one working cycle, wherein at least the exhaust valves are kept closed, the exhaust valves and the intake valves of the cylinders of the internal combustion engine are controlled in a synchronized manner, and, at least in a first cylinder, from the end of the suppression, the exhaust valve is opened with the intake valve closed, and the enclosed gas is discharged without injection and ignition.

6. The device according to claim 1, wherein in the first cylinder only, from the end of the suppression, the exhaust valve is opened with the intake valve closed, and the enclosed gas is discharged without injection and ignition, and in the further cylinders after the first cylinder, from the end of the suppression, at least a predefined minimum amount of fuel is injected and ignited before the discharge of the enclosed gas.

7. The device according to claim 5, wherein a negative torque profile resulting from the suppression with enclosure of the residual gas is compensated by the traction electric machine.

8. The device according to claim 5, wherein after the discharge of the enclosed gas without injection and ignition, subsequently, at least the first cylinder is filled with a minimum amount of air and ignited with very low efficiency, and proceeding from there, the combustion, for torque build-up, is adjusted in an increasing and controlled manner by way of a shallow ramp, which is predefined so as to be compensated by the traction electric machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Further advantages and features of the disclosure emerge from the following description and from the following drawings, to which reference will be made.

[0031] FIG. 1 shows the main components of the control device according to the disclosure; and,

[0032] FIG. 2 shows an illustration of the torque profiles resulting from the disclosure during the transition from suppression into regulated combustion, for example, at least into fired overrun cut-off.

DETAILED DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 schematically shows an internal combustion engine 1, for example, a gasoline engine, with multiple cylinders, with just one cylinder 2 being illustrated here in a representative manner. As is known, a cylinder 2 consists of a cylinder head 3 and a piston 4 which is movably mounted in the cylinder. Valve seats for at least one intake valve 5 and for at least one exhaust valve 6 and an ignition plug 7 are arranged in the cylinder head 3.

[0034] The general functioning of internal combustion engines is well known from the prior art, and will therefore not be discussed further at this juncture.

[0035] It is furthermore known that, during the operation of an internal combustion engine, in certain operating phases, individual or all the cylinders of the internal combustion engine can be partially suppressed, for example, during a gearshift.

[0036] In order for flushing of a catalyst with fresh air to be avoided, it is provided according to the disclosure that all the exhaust valves 6 assigned to the suppressed cylinder 2 are kept closed immediately after the last combustion before a suppression.

[0037] For this purpose, the internal combustion engine 1 has, on an exhaust side, a valve drive 8, which is variable at least in two stages, in order to open and to close the exhaust valves 6 of the internal combustion engine 1.

[0038] For example, the valve drive 8 on the exhaust side comprises, for example, a stage system which, in particular, has a valve with switchable hydraulic valve compensation, a camshaft with sliding cams, and/or has a switching cam follower.

[0039] If required, the valve drive 8 can be switched in such a way that the exhaust valve 6 remains closed in a cycle-independent manner. The valve drive 9, on an intake side, can be continuously adjustable. The valve drives 8 and 9 are, for the sake of simplicity, illustrated merely schematically in FIG. 1.

[0040] In order for the valve drives 8 and 9 to be controlled according to the disclosure and as required, provision is made of an electronic control unit 10 that is programmed accordingly. The electronic control unit 10 may be implemented, for example, by one or more processors or CPUs, and software or firmware stored in a memory and/or RAM.

[0041] Further implementation details of the disclosure will be described below on the basis of FIG. 2, with time t being illustrated on the x-axis and torque M being illustrated on the y-axis.

[0042] A working cycle of an internal combustion engine 1 normally consists of an intake stroke, during which fresh air is sucked in, a compression stroke, during which the sucked-in fresh air is compressed and a fuel mixture is injected into the combustion chamber of the internal combustion engine 1, a power stroke, during which the compressed mixture is ignited, and an exhaust stroke, during which the combusted gas is discharged from the combustion chamber via the exhaust valve 6.

[0043] A suppression takes place, for example, during an overrun operation or during a drag operation.

[0044] Overrun operation refers, in the case of a motorized vehicle, to a driving state in which, without a separation of the frictional connection, that is to say with non-open clutch, the internal combustion engine 1 is kept in motion by the vehicle mass. This driving state occurs, for example, during downhill travel. With hybrid vehicles, it is moreover possible for the internal combustion engine to be also driven along by the electric machine, in certain load states.

[0045] During the exhaust stroke taking place immediately before the suppression, that is to say, after the last ignition before the suppression, the exhaust valve 8 is kept closed. During the intake stroke taking place immediately before the suppression, the intake valve 9 is likewise kept closed. The residual gas which is discharged via the exhaust valve 8 during conventional operation is consequently enclosed in the cylinder 2.

[0046] During the last exhaust stroke before ignition commences again, the exhaust valve 8 is opened in accordance with cycle, so that the enclosed residual gas is discharged or flushed out without combustion (that is to say, without injection and ignition). Subsequently, the intake valve 9 is opened and fresh air is sucked in. Then, the operation of the internal combustion engine 1 is continued, that is to say, injection and ignition are activated in accordance with cycle.

[0047] A traction electric machine 11 is provided, in addition to the internal combustion engine 1, as a further drive motor in FIG. 1. Uncomfortable drops in torque of the internal combustion engine 1 are compensated by the superimposing torque M of the traction electric machine 11.

[0048] FIG. 2 illustrates the transition after suppression back into conventional internal-combustion-engine-powered operation, in particular, also with compensatory torque engagement of the traction electric machine 11.

[0049] The following torque levels are schematically illustrated in FIG. 2: [0050] M1=maximum torque during fired overrun operation [0051] M2=current torque before suppression and exhaust-valve closure [0052] M3=minimum torque during fired overrun operation

[0053] The torque profile M_V of the internal combustion engine 1, which undergoes a cylinder suppression with exhaust-valve closure for enclosure of the residual gas up to time t1, which undergoes discharge of the residual gas without injection and ignition between times t1 and t2, and which is adjusted in a regulated manner up to the target torque, here M1, again, according to a predefined gradient, between times t2 and t3, is illustrated by a dotted line.

[0054] The V-shaped drop in torque of the torque profile M_V of the internal combustion engine 1 is compensated by the superimposing torque M_E of the traction electric machine 11: [0055] 1. The target torque M_E of the electric machine 11 is zero (0 [Nm]) before time t1 and after time t3 in this exemplary embodiment. Instead of a target torque M_E of zero for the electric machine 11, it is in principle possible for any operating point during traction or overrun operation to be predefined as a target torque M_E from which the compensation torque is imparted. [0056] 2. At time t2, the electric machine 11 has to make an adjustment, by way of its torque M_E, according to the increased drag torque M_V of the internal combustion engine 1 and the changed driver demand M_target. [0057] 3. From time t3, the driver demand M_target is again provided solely by the torque M_V of the internal combustion engine 1.

[0058] The target torque profile M_target, which can be initiated, for example, by a driver specification (for example switchover from depressed brake to accelerator pedal), which would result in an uncomfortable jolt without implementation of the present disclosure, is illustrated by a dash-dotted line.

[0059] The scenario of exiting ESCF operation is described in even greater detail below. According to the disclosure, the intention is for the unknown gas mixture in the cylinder to preferably not be ignited and to first of all be discharged. This results in increased engine friction. Subsequently, preferably at least the first cylinder is filled with a minimum amount of air and ignited with very low efficiency. Proceeding from there, the combustion is gradually brought to an optimum combustion in such a way that the torque build-up between time t2 and time t3 is achievable by way of a predefined shallow ramp R. The purpose of this shallow ramp R is to allow the best possible compensation by the electric machine 11; this is because a steep or uncontrolled gradient cannot be compensated well by the electric machine 11.

[0060] The transition from normal operation into ESCF operation can also be controlled in an analogous manner.