JPS5963340A - Variable compression ratio engine - Google Patents

Abstract

PURPOSE:To raise the temperature of exhaust gas to maintain the purifying function of an engine exhaust gas purifier satisfactory by providing a catalytic sensor in the engine exhaust gas purifier so that a device for changing the volume of a combustion chamber is actuated in the direction of decreasing a compression ratio when the exhaust gas is lower than a predetermined temperature. CONSTITUTION:A catalytic type exhaust gas purifier 7 is disposed in an engine exhaust passage 6, and a cylinder 2 is provided with the second cylinder 9 communicated with a combustion chamber 9 and a compression ratio changing piston 10. A control circuit 24 which receives signals from a load sensor 25, a rotational speed sensor 26, a knock sensor 27, etc., computes a compression ratio giving an optimum combustion efficiency, and controls the position of the piston 22 through an actuator 22. The control circuit 24 receives a signal from a catalytic temperature sensor 8 and compensates a signal S6 in the direction of decrease in the compression ratio to lower combustion efficiency when a temperature is lower than a predetermined temperature, so that the temperature of exhaust gas is raised to sufficiently ensure the function of the exhaust gas purifier.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable compression ratio engine in which a catalytic exhaust purification device is provided in an exhaust passage.

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 the charging efficiency is high. A volume variable device that changes the volume is provided, and the volume variable device is controlled in response to engine operating conditions or in accordance with the presence or absence of knocking, so that the engine can be operated at the highest possible compression ratio without causing knocking. Variable compression ratio engines have been proposed.

On the other hand, today, many engines installed in automobiles, etc. are equipped with a catalytic exhaust purification device in the exhaust passage.The catalyst used in this type of exhaust purification device is generally
If the temperature is not maintained at about 300° C. or higher, the activity will be lost and the exhaust gas will not have a sufficient effect of converting the exhaust gas to fI.

However, such a catalytic exhaust purification device has the above-mentioned 6 problems.
If a J-variable compression ratio engine is used, the compression ratio will be greatly increased, improving combustion efficiency and lowering the exhaust gas temperature, so the catalyst temperature will not be maintained sufficiently, especially in the low load range. A problem may occur in which the exhaust gas purification function is impaired.

An object of the present invention is to provide a variable compression ratio engine that eliminates the above-mentioned problems.

The variable compression ratio engine of the present invention is a variable compression ratio engine equipped with a catalytic exhaust purification device as described above, which is equipped with a catalyst temperature sensor to detect the catalyst temperature, and when the catalyst temperature becomes below a predetermined temperature. When the activity of the catalyst is about to be lost, the control device that receives the output of the sensor operates the combustion chamber volume variable device in the direction of lowering the compression ratio, which is considered as the fl' sign.

If the compression ratio is lowered, the exhaust gas temperature will rise and the
The temperature is also on the same level, and the exhaust gas purification ability of the catalyst is maintained well.

Note that the catalyst temperature sensor is good because it can detect whether the catalyst is at a temperature that is sufficient to perform its purification function. Alternatively, the temperature may be detected indirectly by detecting the ambient temperature around the catalytic exhaust purification device or the exhaust gas temperature in the exhaust passage upstream or downstream of the catalytic exhaust purification device.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows a variable compression ratio engine according to one embodiment of the present invention. An exhaust boat 5 provided with an exhaust valve 4 is opened in the combustion chamber 3 defined by the cylinder 1 and the piston 2, and the exhaust boat 5 is connected to an exhaust passage 6.
is connected to. The exhaust passage 6 is provided with a catalytic exhaust purification device 7 that uses a catalyst to promote the oxidation and reduction of CO1, IC, NOx, etc. in the exhaust gas and removes these substances from the exhaust gas. The catalyst of this exhaust purification device 7 is
As is well known, sufficient catalytic activity is not exhibited unless the temperature is maintained at about 200 to 300° C. or above. Further, the exhaust gas purification device 7 is provided with a catalyst temperature sensor 8 that detects the temperature of the catalyst of the exhaust gas purification device 7.

On the other hand, a second cylinder 9 is formed in the cylinder head portion and communicates with the combustion chamber 3, and a variable compression ratio piston 10 is slidably housed in the second cylinder 9. The end of the rod 11 connected to the compression ratio 0] variable piston 10 is connected to a power piston 13 slidably disposed within the power cylinder 12.

Two oil passages 14 and 14' communicate with the power cylinder 12 on both sides (upper and lower in the figure) of the power piston 130, and these oil passages 14 and 14' are connected to a spool valve 15. The power cylinder 12 contains oil 16
Hydraulic oil stored in the hydraulic pump 17 is pumped through the discharge pipe 18 and the spool valve 15, and operates the power piston 13 of the power cylinder 12.
The hydraulic oil whose pressure has decreased is removed from the spool valve 15 and the return pipe 19.
The oil is returned to the oil reservoir 16 through the oil reservoir 16.

This spool valve 15 is conventionally used to control a power cylinder device, and the spool valve 15
Depending on the displacement direction (vertical direction in the figure) and displacement amount of a, oil path 1
The HilJ 1141L controls the supply of pressure oil to the power cylinder 12 via the pistons 4 and 14', and controls the vertical position of the power piston 13 in the figure. i.e. spool 1
When 5a is displaced upward from the reference position, the power piston 1
3 moves upward, and conversely, when the spool 15a moves downward, the power piston 13 moves downward.

A link 21 rotatably supported around a fulcrum 20 is connected to the spool 15a of the spool valve 15, and the link 21 is connected to a rod 23 that is moved vertically in the figure by an actuator 22. . When the actuator 22 is driven and the link 21 is moved, the spool 15a is displaced in the vertical direction in the figure, and the power piston 13 is displaced in the vertical direction, the compression ratio connected to the power piston 13 via the rod 11 is variable piston 10
The vertical position within the second cylinder 9 can be changed.

As a result, the volume of the combustion chamber 3 is changed, and the compression ratio of the air-fuel mixture compressed by the piston 2, which reciprocates with a constant stroke, is changed.

That is, the further the variable compression ratio piston 10 is located in the drawing, the larger the volume of the combustion chamber 3 is, and the lower the compression ratio is.
The answer product decreases and the compression ratio increases.

Control of the variable compression ratio piston 10 will be explained below. The actuator 22 that drives the variable compression ratio piston 10 moves the rod 23 by an electric iB device (not shown), and this electromagnetic device is driven by a drive signal S6 output from the open side j circuit 24. be done. The 1u () control circuit 4 receives a load signal S1 output from a load sensor 25 that detects engine load by detecting the opening degree of a throttle valve (not shown), and a pulse generator fixed to the crankshaft, for example. and a rotation speed signal S2 outputted by a rotation speed sensor 26 consisting of a pulse counter or the like, and a catalyst temperature signal S3 output by the catalyst temperature sensor 8. Knock sensor 2 consisting of a child
7 and a piston position signal S5 output by a piston position sensor 29 that detects the position of the variable compression ratio piston IO by detecting the position of the position detection rod 28 fixed to the power piston 13. It is now possible to do so.

The control circuit 24 processes the load signal S1 and the rotation speed signal S2, outputs a five-drive signal S6, and controls the actuator 2.
2 to control the position of the variable compression ratio piston 10,
For example, as shown in FIG. 2, the compression ratio is set depending on the engine load and engine speed. The compression ratio setting pattern as shown in the button in Figure 2 may be mapped and stored in a storage device such as H, (, lM, etc.), or it may be created using a function generator or the like. In the compression ratio setting pattern shown in Figure 2, the reason why the compression ratio is set lower as the engine speed is lower is because knocking is more likely to occur in such operating ranges. In addition, in this example, the engine load is detected by the throttle opening, so the setting is such that the engine load is suppressed by the throttle opening, but the engine load can of course be detected by other means such as intake negative pressure. Therefore, a compression ratio setting pattern suitable for each load detection means may be formed on such a platform.

Since the variable compression ratio piston 100 position ii7 corresponds to the three valleys of the combustion chamber and, in turn, to the compression ratio, the control circuit 24 detects the compression ratio based on the piston position signal S5, and matches the compression ratio with the set value. , if there is a deviation between the two, the drive signal S6 is corrected to eliminate the deviation.

In addition, the 11J tumor circuit 24 outputs a knock sensor output signal S4.
When the occurrence of non-king is detected, actuator 2
The drive signal S is applied so as to displace the rod 23 of No. 2 upward, that is, to displace the compression ratio variable piston] 0 upward.
6 is corrected, and the compression ratio is lowered outside of the setting pattern shown in FIG. 2, thereby suppressing the occurrence of non-king.

The control circuit 240 function described above is also provided in a conventional control device for a variable compression ratio engine.
In this embodiment, in the case of "b" compression ratio engine, further "
The second control circuit 24 ensures that the exhaust gas purification function of the catalytic exhaust purification device 7 described above is always maintained satisfactorily. This point will be explained in detail below. The control circuit 24,
When receiving the catalyst temperature signal S3 and detecting that the temperature of the catalyst of the exhaust purification device j't7 has fallen below a predetermined temperature, the drive signal S6 is changed so that the actuator 220 rod 23 is displaced upward, that is, compressed. The drive signal S6 is corrected so that the variable ratio piston 10 is displaced upward.

The predetermined temperature is a temperature at which the catalyst can maintain sufficient activity;
Alternatively, the temperature may be set to a slightly higher temperature with some margin. Note that the catalyst temperature decrease as described above occurs when the compression ratio is set quite high during engine operation, causing rapid combustion of the air-fuel mixture, thereby lowering the exhaust gas temperature.

If the compression ratio variable piston 10 is displaced upward by correcting the drive ratio S6, the combustion chamber size increases and the compression ratio decreases. As a result, the combustion rate decreases, the exhaust gas temperature increases, and the catalyst temperature also increases above the predetermined temperature,
Since the activity of the catalyst is maintained well, the exhaust purification device 7 has a sufficient exhaust gas purification function 4).

As described in detail above, the variable compression ratio engine of the present invention can be operated with variable compression ratio (・thermal efficiency), and does not cause deterioration of the exhaust purification device due to inappropriate setting of the compression ratio. It has become.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIG. 2 is a graph showing an example of a compression ratio setting pattern. 3... Combustion chamber 6... Exhaust passage 7
... Catalytic exhaust purification device 8 ... Catalyst temperature sensor 9 ... Second cylinder 10 ... Compression ratio variable piston 12 ... Power cylinder 13.・・・・・・
Power piston 15...Spool valve 22...
... Actuator 24 ... Control circuit

Claims (1)

[Claims] In a variable compression ratio engine equipped with a combustion chamber volume variable device and a catalytic exhaust purification device in the exhaust passage, there is provided a catalyst temperature sensor for detecting the catalyst temperature of the exhaust gas purification device, and a catalyst temperature sensor that receives the output of the catalyst warm sensor. A variable compression ratio engine, comprising: a control device that operates the variable combustion chamber volume device in a direction to lower the compression ratio when the catalyst temperature becomes equal to or lower than a predetermined engine temperature.