JPS59188056A - Variable compression ratio engine - Google Patents

Abstract

PURPOSE:To surely suppress knocking, by first reducing compression ratio upon detection of knocking, and delaying ignition timing when knocking cannot be suppressed irrespective of reduction in compression ratio by a predetermined amount. CONSTITUTION:When a control circuit 24 receives an output from a knocking sensor 7 during engine operation and decides creation of knocking, it compares a real compression ratio E given by a compression ratio sensor 28 with a minimum compression ratio E0 dependent upon engine rotational speed. When E> E0 is given, the real compression ratio is reduced by a predetermined amount DELTAE to determine a maximum compression ratio E, and a variable compression ratio control valve 22 is controlled to control a position of a compression ratio varying piston 10. Further, when it is decided that subsequent knocking is created, and E<=E0 is given, a real ignition timing is reduced by a predetermined amount to determine a final timing advance and delay ignition timing of an ignition plug 8.

Description

[Detailed Description of the Invention] Regarding Engines As is well known in internal combustion engines such as gasoline engines, increasing the compression ratio improves thermal efficiency. However, if the compression ratio is set too high, knocking is likely to occur, especially at high loads when charging efficiency is high. Therefore, for example, as shown in Japanese Utility Model Application Publication No. 56-79639, a volume variable device that changes the volume of the engine combustion chamber is provided, and the volume variable device is adapted to correspond to all engine operating conditions or depending on the presence or absence of non-king. Variable compression ratio engines have been proposed that can be controlled and operated at as high a compression ratio as possible without knocking.

On the other hand, as a method to suppress knocking when it occurs, it is also effective to delay the ignition timing.
No. 3-60430 proposes an ignition device for an internal combustion engine that aims to maintain a stable engine condition by automatically delaying the ignition timing when knocking occurs.

However, delaying the ignition timing means moving the ignition timing toward the expansion stroke side, which means that the combustion pressure at the time of ignition and explosion does not increase sufficiently, and combustion is insufficient and some of the fuel is exhausted as it is. etc., and output loss becomes a problem. On the other hand, if the compression ratio is lowered, a power loss still occurs, but it is thought to be smaller than the loss caused by delaying the ignition timing, and this has been experimentally proven.

However, there is a limit to lowering the compression ratio, and if the compression ratio is lowered beyond a certain point, the fire propagation distance becomes longer due to the structure, the combustion speed becomes slower, and the output loss increases.

For this reason, it is desirable to raise the compression ratio as much as possible, and when knocking occurs, lower the compression ratio to suppress it. If knocking cannot be completely suppressed, it is possible to effectively suppress knocking by delaying the ignition timing.

In view of the above circumstances, the present invention first lowers the compression ratio completely when knocking is detected to completely suppress non-king, and when knocking cannot be suppressed even after lowering the compression ratio by a predetermined amount, the ignition timing is delayed.

The purpose of this invention is to provide a variable compression ratio engine that has a variable compression ratio.

In the variable compression ratio engine of the present invention, when synknock is detected by the knocking sensor, the compression ratio variable device first increases the volume of the combustion chamber υ based on a signal from the control circuit to increase the compression ratio by a predetermined amount. According to the present invention, the ignition timing of the ignition device is delayed only when knocking cannot be sufficiently suppressed even if the compression ratio is lowered by a predetermined amount. When knocking occurs, knocking is first suppressed by completely lowering the compression ratio with relatively small output loss, so knocking can be suppressed efficiently, and if non-king suppression is still insufficient, the ignition timing can be delayed, ensuring reliable knocking. Non-king can be completely suppressed.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram illustrating a variable compression ratio engine according to one embodiment of the present invention. An exhaust port 5 in which an exhaust valve 4 is provided in the cylinder head 6 opens into the combustion chamber 3 formed by the solinter 1, the piston 2, and the cylinder head 6, and the exhaust port 5 is connected to an exhaust passage provided in an exhaust manifold. and communicates with the outside air via a muffler or the like (not shown). The cylinder head 6 has the combustion chamber 3
A second cylinder 9 is formed which communicates with the 27th cylinder 9, and a variable compression ratio piston 10 is slidably housed within this 27th cylinder 9. The end of the rod 11 connected to the variable compression ratio piston 10 is connected to a power piston 13 slidably disposed within the power cylinder 12. In the power cylinder 12, two oil passages 14a and 14b are provided in each of oil chambers 20a and 20b (referred to as an upper oil chamber 20a and a lower oil chamber 20b, respectively) which are divided into upper and lower parts in the figure. These oil passages 14'a communicate with each other,
i, 4 bH Connected to Sgur valve 15. The spool valve 15 is connected to a discharge pipe 18 through which the hydraulic oil stored in the oil sump 16 is sucked and discharged by a hydraulic pump 17, and a return pipe 19 that returns the hydraulic oil to the oil sump 16. 15 by discharge pipe 18
and return piping 19 and oil path], 4. a, 14.
b is selectively communicated with.

The spool 15a of the spool valve 15 has a link 2.
One end 21c of the link 21 is rotatably connected, and the other end 2], a of the link 21 is rotatably connected to an auxiliary rod lla of the power piston 13 that projects on the side opposite to the rod 11.

Further, the link 21 has a predetermined position 2.1. determined depending on the stroke of the power piston 13 and the spool 15a.
A rod 23 of the variable compression control valve 22 is rotatably connected to b.

Spool valve 15, spool 21 and variable compression control valve 22
is conventionally used for controlling a power cylinder device, and the direction of displacement of the variable compression control valve 22 (
From the spool valve] 5, depending on the vertical direction in the figure) and displacement amount,
<This is to control the vertical position of the ζ1 no piston 13 in the figure by feeding all the pressure oil into the Warn cylinder device. For example, if we consider a case where the rod 23 of the variable compression control valve 22 is displaced by a predetermined amount downward in the figure, the displacement of the rod 23 causes the link 21 to be moved to the auxiliary rod of the power piston 13]
], the other end 21c is pushed down as a fulcrum at the connecting point 24ai with a. (This is the oil passage 14a, 1 communicating with the oil chamber 20a, 20b of the power cylinder device.
4. b are both closed by the spool valve 15, and the power piston 13 is held static. )
Therefore, the spool], 5a of the spool valve 15 is also pushed down, and the discharge pipe 18 and the oil passage], 4a are communicated with each other, and the return pipe J9 and the oil passage 14b are communicated with each other. Pressure oil is sent from the oil passage 14a to the upper oil chamber 20a, and oil in the lower oil chamber 20b is discharged from the oil passage 14b via the return pipe 19. As a result, the power piston 13 is pushed down, and the variable compression ratio piston 10 connected thereto is also pushed down, increasing the compression ratio, and the auxiliary rod lla is also pushed down. When the auxiliary rod lla is lowered, the rod 23 of the variable compression control valve 22 is held at the position where the rod 23 has been displaced by the predetermined amount, so that the link 21 serves as a fulcrum at the connection point 21bi with the rod 23, completely pushing up the spool 15a. Thereby, the piping 18, 19 and the oil passage 14a in the spool valve 15.

14b is gradually closed, and when this communication is completely closed, the power cylinder 13 is held stationary at that position.

In this way, by moving the rod 23 of the variable compression control valve 22 up and down, the position of the power cylinder 13 in the vertical direction in the figure can be controlled, and as a result, the compression ratio can be controlled by moving the variable compression ratio piston 10i up and down. That is, when the lower position of the variable compression ratio piston 10 in the 27th cylinder 9 is changed, the volume of the combustion chamber 3 is changed, and the compression ratio of the air-fuel mixture compressed by the piston 2 that reciprocates with a constant stroke is changed. . In this case, if the rod 23 of the variable compression control valve 22 is displaced upward, the compression ratio decreases, and if it is displaced downward, the compression ratio increases.a The stroke of the rod 23 of the variable compression control valve 22 is as follows.
Based on a control signal from the control circuit 24, it is controlled by, for example, electromagnetic means. This control circuit 24 receives an output signal from a load sensor 25 that detects the engine load by detecting the full opening of the throttle valve, an output signal from a rotation sensor 26 that detects the engine rotation speed, and an output signal from the combustion chamber 3. output signal from the knock sensor 7, which is installed in a position facing the engine and detects all occurrences of non-king, and the power cylinder] 3
An output signal from a compression ratio sensor 28 that detects the compression ratio by detecting the position of the rod 11 connected to - and an output signal from a memory circuit 27 that stores information for calculating all optimum values are input. Based on these input signals, a signal for fully driving the variable compression control valve 22 and a signal for adjusting the ignition timing are sent to an ignition system consisting of the variable compression control valve 22, a spark plug 8, an ignition coil (not shown), etc. Output each.

FIG. 2 shows a flowchart of the control in the control circuit 24, and the compression ratio control and ignition timing control will be fully explained based on this diagram.

The flow starts from step S1 (is step S2
Based on the signal from the knock sensor 7, the presence or absence of knocking is determined. When it is determined that knocking has not occurred, the process proceeds to step S6, where it is determined whether the ignition timing is advanced or delayed relative to the optimum ignition timing. This determination is performed by comparing the optimum advance angle Igo (L, rpm) determined based on the engine load (L) and engine speed (, rpm) stored in advance in the memory circuit 27 and the actual advance angle "gl" at the time of determination. Ig1≧I
go (L, rpm), proceed to step S7,
Igl<Igo(L.

, rpm), the process advances to step S8. Note that the optimum advance angle g is stored in the storage circuit 27. (L.

rpm) is divided into several ranges (a, b, c) by dividing the load and rotation speed into several ranges as shown in Figure 3.
, . Therefore, for example, when the load is 41 and the rotational speed is rl, the stored value in the area where the point p1 determined by that value is located is the optimum value of the advance angle at that time.

When it is determined in step S6 that Ig1≧■go (L, rpm), there is no ignition timing delay and knocking has not occurred, so the compression ratio is increased to near the knocking generation range and used in a place where the thermal efficiency is as high as possible. It is desirable to do so. Therefore, the process proceeds to step S7, where the final compression ratio Ei is determined by increasing the current compression ratio by a predetermined amount ΔE, and the process proceeds to step S9. In this case, the ignition advance angle g1 is maintained as the final advance angle and the process proceeds to step S9.

In step S6, Igl<Ig, (L, rpm
), the ignition timing is delayed from the optimum timing even though there is no knocking, so it is desirable to advance the ignition timing to reduce the output loss due to the ignition timing delay. Therefore, the process proceeds to step S8, and the final advance angle Ig is increased (increased by 1) by a predetermined amount ΔIg.

is determined and the process proceeds to step S9. In this case, the compression ratio E can be maintained as the final compression ratio and the process proceeds to step S9.

When it is determined in step S2 that knocking has occurred, the process advances to step S3 and the current compression ratio E
and the minimum compression ratio Eo (
rpm). The minimum compression ratio, Eo (r
pm') indicates the minimum value of the compression ratio within the range in which the total output loss can be suppressed to less than the predetermined value, and is set for each predetermined rotation range as shown in the table, and is stored in advance in the memory circuit 27. There is.

In table step S3, when it is determined that E≦Eo (rp+η), the current compression ratio E is already the minimum compression ratio Eo.
(rpm) or less, further lowering the compression ratio is not desirable because the output loss will become too large. Therefore, proceed to step S4,
To suppress non-king, the current ignition advance angle is the total predetermined amount ΔIg
With the reduced (delayed) final advance angle Ig1, the compression ratio E is held as the 111 final compression ratio and the process proceeds to step S9.

If it is determined in step S3 that E>Eo (rpm), the compression ratio can be lowered to the minimum compression ratio Eo (rpm), so in order to suppress knocking, the ignition timing remains unchanged and the compression ratio It is desirable to lower this from the viewpoint of output loss. Therefore, the process proceeds to step S5, where the final compression ratio E is determined by reducing the current compression ratio by a predetermined amount ΔE, and the ignition advance angle Ig is maintained as the final advance angle by 1 inch, and the process proceeds to step S9. , Steps S4゜85, S according to each condition.
After the final advance angle Ig and final compression ratio E are determined in step S7 or S8, the process proceeds to step S9. Step S
At step 9, a full signal is output to the variable compression control valve 22 to control the position of the variable compression ratio piston 10, as shown in FIG. 1, so that the final compression ratio E is obtained. Next, proceed to step SIO, and after determining the final ignition timing IT obtained by adding the final advance angle Ig to the basic ignition timing t (L, rpm) set in advance based on the rotation speed and load, step Go to Sll and set the ignition timing
A control signal is output to the spark plug 8. The basic ignition timing t(L, rpm) is determined by dividing the load and rotation speed into several ranges as shown in Fig. 4.
How many areas (a', b', C',...11'
, . . .), and the basic ignition timing It(L, rpm) for each region is stored in advance in the storage circuit 27.

Thereafter, the process returns from step 11 to step 2, and the same flow is repeated again. Note that this flow is performed once for each cycle consisting of intake, compression, explosion, and exhaust, and is controlled to achieve the optimum efficiency for each cycle.

In this way, by controlling according to the flow shown in Figure 2, when there is no knocking, first optimize the ignition timing, then increase the compression ratio as much as possible (to just before knocking occurs) to improve thermal efficiency and prevent knocking from occurring. Sometimes, the compression ratio is first lowered to the minimum compression ratio, and if knocking cannot be suppressed even then, knocking can be suppressed by delaying the ignition timing.

As explained above, according to the present invention, when knocking occurs, the compression ratio is first lowered to the lower limit (minimum compression ratio) within a predetermined limit, and the output loss is not relatively increased.
Knocking can be efficiently suppressed, and if knocking still cannot be suppressed, the ignition timing can be delayed to reliably suppress knocking.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing one embodiment of the present invention, Fig. 2 is a flowchart showing a control example of the present invention, Fig. 3 is a graph for setting the optimum advance angle in the embodiment of the present invention, and Fig. 4 is a It is a graph for setting basic ignition timing in an example of the present invention.

Claims (1)

[Claims] a compression ratio variable device for changing the volume of the combustion chamber; an ignition device for igniting; a knocking sensor for detecting the presence or absence of knocking; A variable compression ratio engine comprising: a variable compression ratio device and a control circuit that controls the ignition device to suppress non-knocking by lowering a set amount, and to cause the ignition device to delay ignition timing when the knocking prevention is insufficient. .