JPS60230548A - Variable compression-ratio type engine - Google Patents

Abstract

PURPOSE:To reduce the variation of torque when compression ratio is switched, by correcting at least either of the amount of the inhaled air or the air-fuel ratio according to the switching of the compression ratio, in an engine in which the compression ratio is varied by varying the capacity of a combustion chamber. CONSTITUTION:The capacity of a combustion chamber 5, namely the compression ratio is stepwise varied by vertically moving a piston 19 by revolving a cam 20 by a motor 24. Further, the operation-state detecting means such as air flow meter 10 and crank-angle sensor 33 are provided. Each output of these detecting means is input into a microcomputer 27, and a motor 24 is controlled according to the deviation between the aimed compression ratio set into the microcomputer 27 according to the engine operation state and the actual compression ratio detected by a compression-ratio position sensor 32. Further, when the compression ratio is switched from low compression ratio to high compression ratio, the correction to suppress the increase of the output for a prescribed time is performed, and when the compression ratio is switched from high to low, the reverse correction is performed for the amount of the inhaled air or the air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a variable compression ratio engine in which the compression ratio of the engine can be changed by changing the volume of the combustion chamber. This invention relates to a variable compression ratio engine whose compression ratio changes depending on the state.

(Conventional technology) In internal combustion engines, improving output and reducing fuel consumption.
Increasing the compression ratio is effective in improving thermal efficiency, but increasing the compression ratio causes the problem of non-king occurring in high load, low rotation ranges, etc. In order to solve this problem, an engine is known in which the compression ratio is changed by changing the volume of the combustion chamber depending on the rotational speed and load of the engine. Furthermore, in such a variable compression ratio engine, a hydraulic chamber is formed on the back side of the piston for variable combustion chamber volume,
An improved type that simplified the hydraulic mechanism by combining the functions of a hydraulic cylinder and achieved miniaturization of the device was published in Japanese Patent Application Laid-open No. 5
8-197439. However, in a variable compression ratio engine that changes the compression ratio in stages, there is a problem in that a shock occurs when the compression ratio is changed, causing discomfort to the occupants.

(Object of the present invention) Accordingly, an object of the present invention is to provide a variable compression ratio engine that can effectively prevent the occurrence of output shock when switching the compression ratio in a variable compression ratio engine that switches the compression ratio in stages. is to provide a formula engine.

(Configuration of the present invention) In order to achieve the above object, the present invention is configured as follows. That is, the variable compression ratio engine of the present invention includes an operating state detection means for detecting the operating state of the engine, and a variable compression ratio means for changing the compression ratio in steps by changing the combustion chamber volume of the engine in steps. Output of the operating state detection means.

compression ratio control means for controlling the compression ratio variable means so that the compression ratio of the engine becomes a target compression ratio according to the compression ratio; and at least one of the intake air amount and the air-fuel ratio when the compression ratio is switched. The present invention is characterized by comprising a correction means for correcting accordingly.

In the present invention, for example, engine rotation speed, engine load, engine coolant temperature, air-fuel ratio, transmission gear position, acceleration/deceleration state, intake air temperature, etc. are detected by the engine operating state detection means. Further, the actual compression ratio in the current operating state is detected by the compression ratio detection means. According to the present invention, when switching the compression ratio, for example, when switching from a low compression ratio state to a high compression ratio state, control is performed to suppress the increase in output for a predetermined time on the intake air amount or the air-fuel ratio. It is carried out against

Further, when switching from a high compression ratio state to a low compression ratio state, reverse control is performed.

(Effects of the Present Invention) According to the present invention, when the compression ratio is switched in the direction of increasing the output, the output is suppressed, and when the compression ratio is switched in the direction of decreasing the output, the output upward control is carried out on the intake air. It is given to the amount or air-fuel ratio. Therefore, fluctuations in output shock at the time of switching the compression ratio can be effectively suppressed.

(Description of Embodiments) Referring to FIGS. 1 and 2, an engine E to which the present invention is applied includes a cylinder bore 2 in which a piston 1 reciprocates, and the cylinder bore 2 is connected to a cylinder block. 3 and a cylinder head 4. A combustion chamber 5 is formed in the upper part of the cylinder bore 2, and an intake boat 6 opens into the combustion chamber 5. This intake boat 6
An intake valve 7 is combined with the combustion chamber 5, and a spark plug 14 faces the opposite side of the intake boat 6 of the combustion chamber 5. An intake passage 8 is connected to the intake boat 6, and the intake passage 8 is provided with an air cleaner 9, an air flow meter 10, and a throttle valve 11 to form an intake system. Further, a fuel injector 12 is arranged near the intake port 6 of the intake passage 8. Further, an exhaust port (not shown) is opened in the combustion chamber 5 in a conventional manner, and an exhaust passage 13 is connected to the exhaust port to form an exhaust system. Further, a valve train system including a cam 15 for operating the liquid valve 7 engages with the intake valve 7 . Note that a bypass passage 16 that bypasses the throttle valve 11 is connected to the intake passage FIpt8, and an air bypass control valve 17 that controls opening and closing of the bypass passage 16 is provided. Furthermore, the combustion chamber 5 has an auxiliary cylinder 18 at its upper part that protrudes upward.
is formed continuously, and the sub-cylinder 18 is provided with a sub-piston 19 that slides inside the sub-cylinder 18 .

The stem 19a of the piston 19 projects outward from the sub-cylinder 518, and its tip abuts against the circumferential surface of the cam 20. A disk 21 is attached near the tip of the stem 19a, and a spring 22 is in contact with the disk 21, thereby biasing the piston 19 upward in the figure. The cam shaft 23 of the cam 20 is rotated by a drive motor 24, which causes the piston 19 to move up and down, thereby changing the volume of the combustion chamber 5, that is, the compression ratio. This constitutes a compression ratio variable means.Furthermore, the lead wire 14a of the spark plug 14 is connected to the one of the distributor 25.
the ignition coil 26
A voltage signal from the spark plug 14 is applied to the spark plug 14 at a predetermined timing. The device in this example uses a microcomputer (
(hereinafter referred to as a microcomputer) 27. Microcomputer 27
Various information representing the operating state is input to the . The intake temperature sensor 2B is attached to the air cleaner 9, detects the intake temperature, and sends a signal to the microcomputer 27. Microcomputer 2
A signal from the air flow meter 10 is also input to 7. Further, the opening degree of the throttle valve 11 is detected by a throttle opening degree sensor 29, and is similarly input to the microcomputer 27. Furthermore, the air bypass control valve 17 is equipped with an air bypass control valve opening sensor 30 that detects the opening of the liquid valve 17.
, a cooling water temperature sensor 31 is provided near the cam 20, a compression ratio positive sensor 32 as a compression ratio detection means for detecting the position of the piston 19 is provided near the cam 20, and a crank angle sensor is provided on the crankshaft for detecting the crank angle. 33, the transmission 34 is provided with a gear position sensor 35 that detects the gear position of the transmission, that is, a gear position, and an atmospheric pressure sensor 3B that detects atmospheric pressure. All signals are input to the microcomputer 27. A signal from the ignition switch 36 is also input to the microcomputer 27 . The microcomputer 27 performs predetermined calculations on the input information representing these operating conditions, and controls the EGR valve 37, injector 12, ignition coil 26, and air bypass control solenoid 17.
a, a predetermined command signal is output to the drive motor 24 for compression ratio control and the transmission control motor 34a. As the transmission, for example, a belt type continuously variable transmission can be used, and as the control motor 34a, a normal type as described in Japanese Patent Application Laid-open No. 161346/1983 can be used. can.

Further, as shown in FIG. 3, a crank angle sensor 33
The signal is passed through a waveform shaping circuit 39, shaped into a waveform, and sent to a central processing unit (hereinafter referred to as CPU) 40. Signals from other various sensors are sent to the A/D converter 41
The signal is converted into a digital signal and input to the CPU 40.

The signal St from the ignition switch 36 is also input to the microcomputer 27, and when the switch 36 is ON, the signal S1 becomes 1, and when it is OFF, the signal S1 becomes O. The microcomputer 27 is a ROM in which predetermined constants are written.
41, and a RAM 42 for writing and reading information representing the operating state, calculation results, etc. from each sensor.

Furthermore, the microcomputer 27 includes a counter 1 (43) that constantly counts the time, and can use the time as information if necessary. The CPU 40 determines whether EGR control should be performed based on various input information and outputs an EGR signal S'e. EGR signal Se
is the EGR valve 3 via the solenoid drive circuit FIlr44.
When the signal Se is 1, EGR control is performed, and when the signal 3e is 0, the EGR control is stopped. The microcomputer 27 includes a counter 2 (45) for controlling fuel injection timing and injection time, and controls the injection signal T.
i is input to the injector drive circuit 46 via the counter 2 (45) to operate the injector 12. Furthermore, the microcomputer 27 is equipped with a counter 3 (47) for controlling the ignition timing, and the ignition timing signal Ts'' is sent to the counter 3 (47), which controls the ignition circuit 48, the ignition coil 26, and the distributor. 25, an ignition signal is generated to the spark plug 14 at a predetermined timing.The CPU also determines whether or not to supply air that bypasses the throttle valve 11. That control signal p
b is input to the solenoid drive circuit 49. The solenoid drive circuit 49 operates the solenoid 17 of the air bypass control valve 17 in response to the control signal pb.
Outputs a valve opening/closing command signal to a. In this case, when the signal Pb is 1, the bypass air increases, and when the signal Pb is 0, the bypass air decreases. The microcomputer 27 also includes a motor drive circuit 50 to control the operation of the drive motor 24 for compression ratio control, and this motor drive circuit 50 receives two control signals M.
1 and M2. The values of the signals Ml and M2 and their control contents are shown in Table 1.

Table 1 Also, the gear ratio control motor 34a of the transmission 34 is operated by a motor drive circuit 51, and this motor drive circuit 51 is controlled by control signals M3 and M4. ing. The relationship between the values of signals M3 and M4 and the gear ratio is as shown in Table 2.

Table 2 Also, the control signal Sp is input to the controller, that is, the power supply circuit 52 of this microcomputer 27, so that the controller is turned ON when the signal Si from the ignition switch 36 is 1. , it will not turn off unless the signal Sp is set to 0.

In the compression ratio control device having the above configuration, one of the compression ratio control
Let's discuss an example.

The programs shown in the flowcharts of FIGS. 3A to 3E are basic programs that are normally repeatedly executed when the ignition switch 36 is ON and the engine is in a complete combustion state, that is, under normal engine operating conditions. This program controls the compression ratio change, calculates the correction amount of ignition timing, fuel injection timing and injection amount, transmission gear ratio deviation, bypass air valve opening deviation, and also calculates the transmission gear ratio deviation. , generates a command signal for changing the bypass valve opening degree and the EGR valve opening degree. The program shown in the flowchart of FIG. 5 is an included routine that is executed by interrupting the above basic program every time the crank angle reaches TDC, and calculates the TDC period of the engine and gives instructions for fuel injection and ignition. Generate a signal.

In the figure, the following symbols are used to indicate constants and discarded variables.

In the basic program, the engine rotation speed Ne is calculated from the TDC cycle Tff (SS2) calculated in the ink club routine (S4).

Then, various data representing the operating state are read (35 to S9). Next, from the map created based on the relationship between the engine speed Ne, the intake air amount Qa, and the ratio Qa/Ne of the engine speed Ne, the basics of the compression ratio and other combustibility governing factors corresponding to the operating state are determined. The quantities are each read out (810-512). This map is, for example, the position value Pc of the piston 19 that gives the basic compression ratio.
1ll is as shown in FIG. According to this map, the area below the output characteristic curve a is divided into a plurality of small areas, and the basic compression ratio position value PCB is set in accordance with each area. This value pce is basically set so that it increases as the rotational speed increases, and decreases as the load increases. Therefore, at low rotation and high load times such as during acceleration (for example, area 11 in FIG. 5), the value P. 8 is getting smaller. The area indicated by β in the figure is the value P. B is relatively small, the area indicated by h is relatively large, and the area indicated by m is set to an intermediate value. A similar map is prepared for the basic fuel injection amount Tll1 and the basic ignition timing TsB, and these basic amounts are set based on them.

Next, after a correction operation is performed on the basic compression ratio position value Pcl1 set by the above map (S1
3 to 323), a piston 19 giving a compression ratio of Fll[
position value Pc.

is calculated (S24). The correction is performed by providing different correction coefficients depending on the engine coolant temperature Tw, the presence or absence of EGR control represented by the EGR signal Se, the atmospheric pressure pt, and the intake air temperature Ta. In this case, the engine temperature correction coefficient Cpew changes with the characteristics shown in FIG. 6 in relation to the engine coolant temperature Tw. Similarly, the altitude correction coefficient Cpcp has the characteristics shown in FIG. 7 in relation to the atmospheric pressure pt, and the intake air temperature correction coefficient Cpca has the characteristics shown in FIG. 8 in relation to the intake air temperature Ta. Given. Therefore, when the intake air temperature Ta, that is, the outside air temperature is high, and when the cooling water temperature Tw is high, the value Pco becomes smaller, and the lower the atmospheric pressure pt, that is, the higher the altitude, the larger the value Pco becomes.

Further, when EGR is performed, the target compression ratio position value Pc.

The value of becomes smaller. In this example, the target compression ratio position value Pco is set to one of three different values, pet, PC9, and P(:l), depending on the magnitude of the calculated value.

Furthermore, the basic opening degree of the bypass air control valve 170 in the relevant operating state is determined from a map prepared in advance based on the engine speed Ne and the ratio Q a / Ne of the intake air amount Qa and the engine speed Ne. Bypass air valve position value Pae is calculated (33
1). Furthermore, basic values for setting the gear position of the transmission 34, that is, basic T/M gear position values P&'R are calculated using the same map (33
2). Next, the position of the piston 19 that gives the actual compression ratio, that is, the deviation ΔPc between the actual compression ratio position value Pc and the target compression ratio position value Pco is calculated (333
). According to the value of this deviation ΔPc, the compression ratio change control signals M1 and M2 are set to predetermined values and output (S35.
541) When the target compression ratio position value Pco is positive, that is, when increasing the compression ratio, the control signal is M1.
=1 and M2=1, a correction value is given so that the ignition timing is advanced (336), and a correction value is given so that the bypass air is increased (337). Furthermore, a correction value is given to increase the fuel injection amount (
338). On the other hand, when the target compression ratio position value Pco is negative, the control signal is set to Ml-1, M2 = 0, and unlike when increasing the compression ratio, a correction value is given so that the ignition timing is delayed. At the same time, a correction value is given to reduce the amount of bypass air (S45).

Then, the position of the transmission gear to which a correction value that increases the fuel injection amount is given is set to the low speed side (S45).
. Next, considering such a correction command signal, the transmission 3
4 target position value Pgo is calculated (39B), and bypass air valve target position value Pao is calculated (S
99). Further, the ignition timing Ts and the injection amount Ti are calculated (S 100.5IOI). In addition,
In this case, although the control signals M1 and M2 for changing the compression ratio are output to the drive motor drive circuit 50, the compression ratio is in a transient state where it has not yet reached the target compression ratio.

Next, the deviation of the gear ratio of the transmission 34 from the target value is calculated (S102). Based on this result, the gear ratio is corrected (S, 103-5106).

Then, regarding the opening degree of the air bypass control valve 17 that determines the amount of air that bypasses the throttle valve 11, the deviation between the target opening degree Pao and the actual opening degree Pa is calculated (S107), and based on the result, the opening degree is calculated. The degree is corrected (3108-3110).

When the actual compression ratio matches the target compression ratio, that is, when the compression ratio change is completed, the flammability governing factors, ignition timing, fuel injection amount, etc., are changed depending on whether the compression ratio has decreased or increased. A predetermined correction value is given to the amount of bypass air for a certain period of time. That is, when the compression specific force S increases, the ignition timing is shifted to the advanced side, the amount of bypass air is decreased, and a correction amount is given such that the amount of injection is decreased (856 to 858). Also, when the compression ratio decreases, the opposite correction amount is given (859
~561).

These correction values are designed to attenuate over time (846-856).

Further, when a change in the compression ratio occurs in the acceleration/deceleration state, correction is made to the flammability governing factors for a certain period of time in a certain operating region (863 to S8'4).
When the engine is in an accelerating state, corrections are made to reduce the amount of bypass air, increase the amount of fuel injection, and shift the ignition timing to the retarded side.

Furthermore, a correction amount is given to change the gear position of the transmission to a lower speed side. On the other hand, during deceleration, a correction amount is given that increases the amount of bypass air and fuel injection and changes the ignition timing to the advanced side.

Finally, the combustibility governing factors are determined by comprehensively taking into account the basic amount from the map, the correction amount due to compression ratio change, and the correction amount due to acceleration/deceleration (3100-s102).

The ignition timing signal TS and fuel injection signal Ti thus determined serve as command signals for the spark plug 14 and the injector 12 when the included routine is executed.

Then, when the ignition switch 36 is turned OFF, the target compression ratio position is set to the low compression ratio position at the time of starting (5ill), and the compression ratio is lowered until the target value is reached (3112-5114).
When the compression ratio falls to the starting position, the compression ratio control motor is stopped (3115) and the controller power is turned off.
It is made FF (3116).

According to this example, when the compression ratio is changed to a higher compression ratio side, the air-fuel ratio is controlled so that the intake air is decreased for a predetermined period of time, and the fuel injection amount is also decreased, so that the air-fuel ratio becomes lean. . When the compression ratio is changed to the low compression ratio side, the opposite control is performed. Therefore, fluctuations in torque output at the time of compression ratio switching can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an engine to which the present invention is applied; FIG. 2 is an explanatory diagram of a microcomputer according to an embodiment of the present invention; FIGS. 3A, 3B, 3C, 3D, and 3E. 4 and 4 are flowcharts showing the details of control according to an embodiment of the present invention, FIG. 5 is a graph showing the relationship between engine load and target compression ratio with respect to engine speed, and FIG. FIG. 7 is a graph showing the relationship between atmospheric pressure pt and compression ratio position altitude correction coefficient, and FIG. 8 is a graph showing the relationship between intake air temperature and compression ratio position engine temperature correction coefficient. It is a graph showing the relationship with the temperature correction coefficient. 1...Piston, 3...Cylinder block, 4...
Cylinder head, 5... Combustion chamber, 8... Intake passage, 1
0... Air flow meter, 18... Sub cylinder, 1
9... Sub-piston, 27... Microcomputer, 33...
Crank angle sensor. 40...CPU, 41...A/D converter. Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] An operating state detection means for detecting the operation and state of the engine; a compression ratio variable means for changing the compression ratio step by step by changing the combustion chamber volume of the engine; compression ratio control means for controlling the compression ratio variable means so that the compression ratio of the compression ratio becomes a target compression ratio; and when the compression ratio is switched, at least one of the intake air amount and the air-fuel ratio is corrected in accordance with the switching. A variable compression ratio engine characterized by comprising a correction means.