Method and device for controlling a throttle valve in an intake manifold of an internal combustion engine

Abstract

A method and a device for controlling a throttle valve (1) in an intake manifold (2) of an internal combustion engine (10) are proposed, wherein a power demanded by a user of the internal combustion engine is converted by control signals to open the throttle valve (1). The power demanded by the user at a first time is converted at a second, later time by control signals of the throttle valve (1).

Description

State of the art

[0001] The invention relates to a method and a device for controlling a throttle valve in the intake manifold of an internal combustion engine according to the preamble of the independent claims. It is already generally known to control the power output of an internal combustion engine by influencing the amount of air drawn in by the engine. For this purpose, a throttle valve in the intake manifold of the internal combustion engine is actuated to influence the amount of air drawn in. If the throttle valve is actuated unfavorably, an unintended engine stall can occur, typically in the near-idle range due to improper clutch operation. Advantages of the invention

[0002] In contrast, the inventive method or device with the features of the independent claims has the advantage of ensuring improved control of the throttle valve. In particular, it avoids changes in the throttle valve position that could lead to undesired operating conditions of the internal combustion engine. This ensures the desired operation of the internal combustion engine. Specifically, the inventive method or device significantly reduces the risk of an unintended engine stop during rapid changes in driving conditions.

[0003] Further advantages and improvements result from the measures outlined in the dependent patent claims. A suitable crankshaft angle for controlling the throttle valve can be selected particularly easily. This angle can be advantageously chosen so that the fuel injection quantity can be adjusted according to the throttle valve control. A time delay between the throttle valve control and the resulting air volume can be advantageously taken into account. This improves the quality of the throttle valve control. Furthermore, the compression work of the internal combustion engine resulting from a change in the throttle valve position is advantageously considered. For this purpose, the throttle valve adjustment is specifically limited to a maximum value. An unfavorable throttle valve adjustment is particularly problematic for the internal combustion engine at low engine speeds.It is therefore possible to carry out the method according to the invention only up to a predetermined engine speed. It can be particularly simple to implement a change in the engine's power output, requested with the air intake valve open, by means of control signals to the throttle valve only after the air intake valve has closed again. If control signals are calculated within predetermined angular windows, specific angular windows can be provided for the calculation and output. An angular window immediately before the air intake valve closes is particularly advantageous. Drawings

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

[0005] They show: the Fig. 1 a schematic view of an internal combustion engine, and Fig. Two different signals from the internal combustion engine compared to an angle scale. Description

[0006] In the Fig. Figure 1 schematically shows an internal combustion engine 10 with a cylinder 3 in which a piston 4 is arranged. Above the piston 4, the cylinder 3 forms a combustion chamber 5 into which a mixture of fuel and air is introduced and combusted. The combustion of the fuel-air mixture in the combustion chamber 5 increases the pressure in the combustion chamber 5, and this pressure is converted into mechanical work by the movement of the piston 4 in the cylinder 3 via a connecting rod (not shown) and a crankshaft. This is thus a well-known Otto engine or diesel engine.

[0007] To supply air to the combustion chamber 5, an intake manifold 2 is provided, in which the amount of supplied air is controlled by a throttle valve 1. Opening and closing the throttle valve 1 controls the amount of air introduced into the combustion chamber 5. Furthermore, a fuel injection valve is provided, either in the intake manifold 2 or directly in the combustion chamber 5, through which fuel is injected either into the flowing air in the intake manifold 2 or directly into the combustion chamber 5. For the sake of simplicity, this fuel injection valve is located in the Fig. 1 not shown in the drawing. To route the exhaust gases after combustion, an exhaust pipe 8 is provided, through which the combusted exhaust gases are transported from the combustion chamber 5. Furthermore, in the Fig. Figure 1 schematically shows an air intake valve 6 and an exhaust outlet valve 7. By opening and closing the air intake valve 6 and the exhaust outlet valve 7, the combustion chamber 5 is connected to the intake manifold 2 or the exhaust pipe 8, depending on the operating phase of the internal combustion engine 10. A control unit 9 is also shown for controlling the internal combustion engine 10; this unit generates signals for controlling the throttle valve 1 or the injection valves.

[0008] Such an internal combustion engine 10 is typically operated using a four-stroke cycle. In the first intake stroke, fresh air is drawn into the combustion chamber 5 by opening the air intake valve 6 and moving the piston 4 from top dead center to bottom dead center. This movement of the piston creates a vacuum in the combustion chamber, drawing air in through the intake manifold 2. The amount of air introduced into the combustion chamber 5 is controlled by opening the throttle valve 1. If fuel is injected into the intake manifold 2, it is also introduced into the combustion chamber 5 during this phase. A compression stroke then follows, in which the piston 4 moves from bottom dead center back to top dead center, thus compressing the fuel-air mixture in the combustion chamber. If fuel is injected directly into the combustion chamber 5, fuel injection can also occur during the compression stroke.Following the compression stroke, the combustion stroke occurs, in which the fuel-air mixture is burned in combustion chamber 5. This combustion significantly increases the pressure in combustion chamber 5, and this pressure is converted into mechanical work by the movement of the piston 4 from top dead center to bottom dead center. During the combustion stroke, both the air intake valve 6 and the exhaust valve 7 are closed. Afterwards, the exhaust stroke occurs, in which the exhaust valve 7 opens, and the exhaust gases, i.e., the byproducts of combustion, are expelled from combustion chamber 5 through the exhaust pipe 8 by the movement of the piston 4 from bottom dead center to top dead center.

[0009] In a single-cylinder internal combustion engine, torque is generated and the engine accelerates only during the combustion stroke. During the other strokes—intake, compression, and exhaust—the engine decelerates and slows down. During the combustion stroke, energy is fed into the mechanical system of piston, connecting rod, and crankshaft. This energy must be sufficient to cover the energy consumption of the exhaust, intake, and compression strokes until the next combustion stroke. Therefore, it must be ensured that the acceleration generated by the combustion stroke is sufficient to maintain the engine's rotation until the next combustion stroke.This can be particularly problematic in internal combustion engines with only one cylinder and a very small intake manifold volume 2 if a very rapid and significant change in the position of the throttle valve 1 occurs. A large change in the amount of air supplied significantly alters the energy demand during the compression stroke. This fact is illustrated by the... Fig. 2 explained.

[0010] In the Fig. Figure 2 illustrates various operating parameters of an internal combustion engine in relation to different operating cycles. A complete operating cycle of the engine from 0° to 720° is shown, followed by an intake stroke between 0° and 180°. The crankshaft angles of the engine are plotted on the right, with an intake stroke extending from 0° to 180°, a compression stroke from 180° to 360°, a combustion stroke from 360° to 540°, and an exhaust stroke from 540° to 720°. Upon reaching 720°, the operating cycle of the engine begins again; that is, 720° corresponds to 0° with respect to a new operating cycle.

[0011] In the Fig. Figure 2A illustrates a power demand placed on the internal combustion engine by a user. It shows that the power demand on the engine is sharply increased at a very small angle (approx. 20°) at the beginning of the intake stroke and then maintained at this value. If, in accordance with this demand, the throttle valve 1 opens simultaneously to introduce a correspondingly large quantity of air into the combustion chamber 5, this leads to the problem that a correspondingly large quantity of air must be compressed in the subsequent compression stroke. Since the energy required for compression or compression work must be generated by the preceding combustion, and since this sudden increase in the air volume was not yet known during this combustion, it is possible that the increased air volume cannot be compressed at all. In this case, the internal combustion engine would stall unintentionally.This can lead to the internal combustion engine stalling. Furthermore, it is possible that the required amount of fuel, corresponding to the air volume, will not be injected into combustion chamber 5 in time. Since the need for a higher fuel quantity is only known when the air volume increases, this additional fuel quantity must be recalculated. The time required for this calculation may be too short, or the time required for the calculation itself, or the sum of the time required for the calculation and the injection time, may be too short. The calculation of the fuel quantity can also be delayed, as such calculations cannot be performed instantly but are only possible at specific times.These problems are particularly serious when the volume of the intake manifold 2 is very small in relation to the volume of the combustion chamber 5, since in this situation a change in the position of the throttle valve very quickly leads to a change in the filling of the combustion chamber 5 with air.

[0012] According to the invention, it is therefore proposed that a change in the engine's power output, requested by a user at a first point in time, be implemented at a second, later point in time by means of corresponding control signals from the throttle valve 1. The second, later point in time is chosen such that the aforementioned problems caused by changing the position of the throttle valve at an unfavorable first point in time are avoided.

[0013] In the Fig. Figure 2B shows the control signals from control unit 9 to throttle valve 1 relative to the crankshaft angles. As in the Fig. As can be seen in 2B, the requested change in power is implemented at a later, second time point by corresponding control signals from control unit 9 to the throttle valve 1. The corresponding signal is made shortly before the end of the intake stroke at an angle of approximately 170°. In the Fig. Figure 2C shows the resulting actual position of throttle valve 1. There is a time lag between the control signals, which were sent at approximately 170°, and the actual action taken by the throttle valve. This delay means that the actual change in the position of throttle valve 1 only occurs at approximately 190° crankshaft angle. Therefore, throttle valve 1 only opens when the air intake valve 6 is already closed and thus has no effect on the compression stroke (between 180° and 360°) or the combustion stroke (between 360° and 540°).

[0014] This leaves sufficient time before the next combustion cycle to perform the necessary calculations of the fuel quantity for the changed air quantity.

[0015] Furthermore, the user's input was Fig. The requested performance increase (2A) was not fully converted into corresponding control signals for the throttle valve. As the Fig. Figure 2B shows that the throttle valve control is changed in such a way that the full power demanded by the user of the internal combustion engine is not achieved. This only occurs in the next intake stroke, i.e., in the angle range between 720° and 180°. By limiting the change in the throttle valve control to a maximum value, it is ensured that a sufficient amount of energy is generated in the combustion stroke (360° to 540°) to guarantee the subsequent exhaust stroke, intake stroke, and the following compression stroke with the increased air volume.

[0016] Through the procedure according to the Fig. 2. Safe operation of the internal combustion engine is ensured. If a user requests a change in power output at an unfavorable initial time, this change will only be implemented at a later time by corresponding control signals to the throttle valve 1, which is suitable for the operation of the internal combustion engine. The selection of this later time is based, in particular, on a specific crankshaft angle of the internal combustion engine within its operating cycle. This is done in such a way as to avoid excessively large changes while the air intake valve is open.

[0017] Furthermore, the time required to calculate the fuel injection quantity should be considered. Such calculations take a certain amount of time or are only scheduled for specific crankshaft angles. Therefore, the time required to calculate the injection quantity, or the timing of the calculation, should be taken into account when selecting the second timing point.

[0018] Furthermore, it should be taken into account that there is a time delay between the throttle valve being controlled and an actual change in the amount of air controlled by the throttle valve.

[0019] Furthermore, it should be considered that a change in the air volume also changes the work or energy required for the subsequent compression of the air in combustion chamber 5. This should be taken into account both with regard to the selection of the second point in time and with regard to the magnitude of the change in the throttle valve position. In particular, when the user requests a significant increase in engine power, a correspondingly large adjustment of the throttle valve 1 should not be made in a single step. It is advisable to distribute a requested large adjustment of the throttle valve over several individual steps in successive combustion cycles. This can be easily achieved by limiting the change in the throttle valve control to maximum values.

[0020] A change in the throttle valve position at unfavorable times is particularly problematic at low engine speeds. This is primarily because the energy stored in the mechanical system of piston, connecting rod, and crankshaft is significantly less at low speeds than at high speeds. Therefore, it can be particularly simple to apply the inventive method only up to a certain engine speed. Alternatively, different procedures can be provided for different engine speed ranges; for example, the maximum permissible adjustment of the throttle valve can depend on the engine speed.

[0021] As mentioned above, a large adjustment of the throttle valve is particularly problematic when the air intake valve is open at that time, i.e., during the intake stroke. Therefore, it is possible, in principle, to allow throttle valve adjustment only when the air intake valve is closed.

[0022] If the calculation of control signals for the internal combustion engine is only performed within predefined angular windows of the internal combustion engine, then the calculation and output of the control signal for throttle valve 1 can be particularly simple, provided it is only within a specific angular window. This is implemented in the Fig. Displayed in 2D. In the Fig. In 2D, time windows for calculating control signals are displayed. These occur every 180° and begin, for example, at an angle of 110° in the intake stroke, at an angle of 290° in the compression stroke, at an angle of 470° in the combustion stroke, and at an angle of 650° in the exhaust stroke. In the Fig. Based on the 2D representation of the typical calculation window length of approximately 30° crankshaft angle, the calculation window that begins at 110° crankshaft angle is particularly suitable for calculating and outputting control signals for throttle valve 1. Therefore, this calculation window is suitable for calculating and outputting control signals for throttle valve 1.

Claims

[1] Method for controlling a throttle valve (1) in an intake manifold (2) of an internal combustion engine (10), wherein a power demanded by a user of the internal combustion engine is converted by control signals to open the throttle valve (1), characterized by , that the power requested by the user at a first time is implemented at a second later time by control signals of the throttle valve (1). [2] Method according to claim 1, characterized by , that for the selection of the second later time point, a specific crankshaft angle of the internal combustion engine (10) is selected in a working cycle of the internal combustion engine. [3] Method according to claim 2, characterized by, that the choice of the second later time point is such that at the chosen second time point in the operating cycle of the internal combustion engine (10) an adjustment of an injection quantity of fuel to an air quantity resulting from the control of the throttle valve (1) can still take place. [4] Method according to claim 2 or 3, characterized by , that for the selection of the second later time point, a time delay between the actuation of the throttle valve (1) and a change in the change in the amount of air flowing into the internal combustion engine (10) caused by the actuation is taken into account. [5] Method according to claim 1, characterized by , that the compression work of the internal combustion engine (10) is taken into account when choosing the later time. [6] Method according to any one of the preceding claims, characterized by that the change in the control signals is limited to a maximum value. [7] Method according to any one of the preceding claims, characterized by , that for the selection of the second later time, a rotational speed of the internal combustion engine (10) is taken into account, in particular that the conversion of the power requested by a user at a first time at a second later time only takes place up to a predetermined rotational speed. [8] Method according to any one of the preceding claims, characterized by , that a power requested by the user when the air intake valve of the internal combustion engine (10) is open is implemented at a second later time when the air intake valve is closed by control signals of the throttle valve (1). [9] Method according to any one of the preceding claims, characterized by, that in a working cycle of the internal combustion engine extending over 720° crankshaft angle, a calculation of control signals is carried out at fixed crankshaft angles, in particular every 180° crankshaft angle, and that the control for the throttle valve (1) takes place in the calculation immediately before the closing of the air intake valves. [10] Device for controlling a throttle valve (1) in an intake manifold (2) of an internal combustion engine, which converts a power demanded by a user of the internal combustion engine (10) by means of control signals to open the throttle valve (1), characterized by , that the device converts the power requested by the user at a first time into a second, later time by means of control signals from the throttle valve (1).

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