JPH0330600Y2 - - Google Patents

Description

[Detailed description of the invention] The invention is a displacement device attached to each cylinder of an internal combustion engine to change the volume of an auxiliary combustion space connected to the main combustion space of the cylinder, which is displaceable by a displacement device. The present invention relates to a device for adjusting the compression ratio of a reciprocating piston internal combustion engine using an auxiliary piston.

The efficiency loss caused by throttling the fuel in a gasoline engine under partial load is compensated for by changing the size of the compression space and thereby changing the compression ratio of the gasoline engine, thus reducing the It is already known that the waste of fuel and the emission of harmful substances in the case of load conditions are reduced. The best results are obtained if the final compression pressure or the maximum combustion pressure remains approximately constant, regardless of the particular engine load, and no knock-inducing combustion occurs.

In known devices for adjusting the compression ratio, the displacement of the auxiliary piston is generally carried out as a function of the load of the internal combustion engine, that is to say as a function of the position of a power-setting member of the internal combustion engine, such as, for example, an accelerator pedal. At that time, if the load increases and the amount of operation of the accelerator pedal increases accordingly, the auxiliary piston is displaced to expand the auxiliary space.

However, in the case of such a compression ratio adjustment, the space fraction must be limited to a value sufficiently far from the knocking limit, especially when different types and qualities of fuel are used, and when the knocking limit is reached. In case the influencing internal and external engine operating temperatures, for example operating temperatures, cannot be captured and taken into account, they must be limited to values far enough apart.

The object of the invention is to create a device for adjusting the compression ratio of the type mentioned at the outset, according to which:
To enable more efficient operation by always maintaining the compression ratio of an engine slightly below the knocking limit regardless of the load state.

The above object is achieved by the characteristic device described in the claims of the utility model registration. According to the invention, the onset of knocking combustion inside at least one of the cylinders of the internal combustion engine itself is used to adjust the compression ratio, and advantageously at least one detection device is provided for detecting the onset of knocking combustion. The displacement device attached to the auxiliary piston can be controlled by the signal from this detection device. At this time, the displacement of the auxiliary piston is discontinuously set step by step to reduce the auxiliary combustion space unless knocking combustion occurs, and to expand the auxiliary combustion space when there is a signal that knocking combustion is occurring. It is displaced in steps. In this case, when the displacement is performed in the direction of expanding the auxiliary combustion space when knocking combustion occurs, the displacement is performed with a larger step length, that is, the stepwise displacement width, than the displacement in the direction of decreasing the auxiliary combustion space. is a valid purpose. This means that when there is a sudden change in the load condition of the internal combustion engine, for example from a small partial load to a full load, the auxiliary combustion space is rapidly expanded and the knocking combustion condition is thus minimized for a minimum time. Guaranteed to be limited. In the case of a displacement of the auxiliary piston in the opposite direction, in the direction of reducing the auxiliary combustion space, a fast follow-up, on the contrary, is not necessary. This is because, even in the most unfavorable case, the internal combustion engine is operated at an inefficient compression ratio rather than at an optimal compression ratio.

An important effect of the present invention is that it allows an oil cycle internal combustion engine to be operated at the best compression ratio just below the knocking limit over a wide range of conditions, regardless of load conditions. The compression ratio is then automatically adapted to the different types and qualities of fuel and to the internal and external engine operating variables.

An exemplary embodiment of the invention is shown in the attached figure by a schematic longitudinal section of a cylinder of an internal combustion engine operated with compression ratio adjustment according to the invention.

In the figure, symbol 1 refers to the entire body of an internal combustion engine for driving a car, for example.
The symbol 2 designates the cylinder of this internal combustion engine 1, in which the main piston 3 slides. This main piston, facing the cylinder head 5, defines a working space, a main combustion space 4, to which the intake and exhaust pipes are connected in the usual manner. Of these pipes, only the suction pipe, designated by the symbol 6, is shown in this figure, and a suction valve 7 is attached to this pipe.

The main combustion space 4 is connected to an auxiliary combustion space 8 arranged in the cylinder head 5, the volume of which is determined by an auxiliary piston 10 which is guided to slide in a bore 9 in the cylinder head. It is becoming possible to change. For displacing the auxiliary piston 10, this piston is connected to a displacement device 11 which can be controlled by a control device 13. The control device 13 also
It is connected to a detection device 12 located at a suitable position in the cylinder 2, which sends a signal to a control device 13 when knocking combustion occurs in the main combustion space 4.

Even if it is theoretically possible to provide each cylinder 2 of the internal combustion engine 1 with its own compression ratio adjustment device, different from the other cylinders, it is expedient to provide a common adjustment device. , for example using a displacement device 11 common to the auxiliary pistons 10 of all cylinders, which displacement device can be controlled by a control device 13 to only one detection device 12 or, for example, to a number of detection devices 12 equal to the number of cylinders. It is expedient to be controlled on the basis of a signal.

The displacement device for displacing the auxiliary piston 10 can be formed in any manner. This device is the control device 1
It must be at a location where the auxiliary piston 10 is displaced and controlled to expand or contract the auxiliary combustion space 8 by the control signal No. 3.

It is possible, for example, to provide a displacement device as described in DE 31 17 133 A1. In this example, the displacement of the auxiliary piston is carried out hydraulically, the position of the piston being determined by an axially displaceable control sleeve. This control sleeve is actuated for control by a step-by-step control device 13 depending on the signal of the detection device 12 which captures the knocking. In this case, the step-by-step control device displaces the control piston via the control sleeve in individually discrete steps in the direction of reducing the auxiliary combustion space 8, and the detection device 12 detects knocking combustion. The displacement will continue unless a signal indicating this is issued. On the contrary, when the detection device 12 recognizes that knocking combustion has occurred in one or all combustion spaces of the internal combustion engine 1, the auxiliary piston 10 is moved step by step in the opposite direction to enlarge the auxiliary combustion space 8. The displacement is discontinuously stepped and continued until knocking no longer occurs. A displacement in the opposite direction is then induced again.

That is, the auxiliary piston 10 is constantly displaced, and the volume of the main combustion space moves back and forth around a limit condition that causes knocking combustion. The most efficient combustion pressure is thus established, automatically taking into account the type and quality of the fuel. In addition to the above, aging and other internal and external engine operating variables are also considered and maintained at near knocking combustion operating conditions at all times.

In order to prevent the driving state of knocking combustion from continuing for a long time, especially when the load suddenly changes to a large one, the step width of the displacement that expands the auxiliary combustion space, that is, the stepwise displacement width, generally reduces the auxiliary combustion space. It must be longer than the stride length. In this way, a rapid adaptation of the combustion space takes place, avoiding long knocking phases when the load increases, whereas a certain, but not significant, adaptation occurs when the load decreases. The adaptation is performed a little slowly, with some loss of efficiency. As a result, during operation, rather than being located on the boundary line of knocking combustion, the engine remains below the boundary line, ie, in a state where no knocking combustion occurs.

Other possibilities for manipulating the displacement of the auxiliary piston are also conceivable. For example, when a knocking combustion occurs subsequently during some compression phase, the control device 13 gradually increases the step of displacement enlarging the combustion chamber, so that a faster adaptation to the increasing load takes place. It is also possible to form The step of displacement of the auxiliary piston in the direction of enlarging the combustion space depends on the frequency at which knocking combustion occurs.

[Brief explanation of the drawing]

The attached figure is a schematic longitudinal cross-sectional view of a cylinder of an internal combustion engine controlled by a compression ratio adjusting device according to the present invention. In the figure, 1... Internal combustion engine, 4... Main combustion space, 8... Auxiliary combustion space, 10... Auxiliary piston, 11... Displacement device, 12... Detection device, 13
...It is a control device.

Claims (1)

[Scope of utility model registration request] Reciprocating piston internal combustion is achieved by means of an auxiliary piston attached to each cylinder of an internal combustion engine so as to vary the volume of an auxiliary combustion space connected to the main combustion space of the cylinder, which is displaceable by a displacement device. In a device for adjusting the compression ratio of an engine, which controls a displacement device 11 via a control device 13 in accordance with a signal from a detection device 12 that notifies knocking combustion, the auxiliary piston 1
0 is constructed so that it can be displaced discontinuously in steps by a step-by-step type control device 13 that controls the displacement device 11, and the auxiliary piston 10 can be displaced step by step in the direction of enlarging the auxiliary combustion space 8. A device characterized in that the advance displacement width is larger than that of the displacement in the direction of reducing the auxiliary combustion space 8.