JPS60230549A - Variable compression-ratio type engine - Google Patents

Abstract

PURPOSE:To improve starting performance by allowing a compression-ratio control means to output a control signal to reduce the compression ratio on engine start, thus obtaining the superior warming performance, 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 varied by moving a piston 19 vertically 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 actual compression ratio detected by a compression-ratio position sensor 32 and an aimed compression ratio set higher in low loading in comparison with that in high loading according to the engine operation state. Further, on engine start, the compression ratio is reduced by outputting a control signal to reduce the compression ratio into the motor 24, and the superior warming performance can be obtained.

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.

(Prior art) In order to improve output and reduce fuel consumption in internal combustion engines, increasing the compression ratio improves thermal efficiency, which is effective. A problem arises in which non-king occurs.

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 varying the volume of the combustion chamber, which also functions as a hydraulic cylinder, simplifying the hydraulic mechanism and reducing the size of the device. The improved type that achieved this was published in JP-A-58-1.
It is described in Publication No. 97439. In these conventional devices, especially those that aim to improve thermal efficiency by increasing the compression ratio when the engine is under low load, it is common for the engine to be in a high compression ratio state when the engine is stopped.

Therefore, such a device will be started in a high compression ratio state. However, when starting under a high compression ratio state, there is a drawback that warm-up performance is poor and, therefore, starting performance is poor.

(Object of the present invention) Therefore, an object of the present invention is to provide a variable compression ratio engine in which the compression ratio is higher at low load than at high load, and to improve starting performance by starting from a low compression ratio state. The object of the present invention is to provide a variable compression ratio engine that provides the following.

(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 detecting means for detecting the operating state of the engine, a variable compression ratio means for changing the combustion chamber volume of the engine, and an engine operating state detecting means for changing the engine combustion chamber volume according to the output of the operating state detecting 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 that is set higher at low load than at high load; The compression ratio correcting means outputs a control signal for reducing the compression ratio. In the present invention, for example, engine speed, engine load, engine cooling water salinity, 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. Preferably, the control is performed using a signal from the cooling water temperature sensor so as not to return to the high compression ratio until the engine completely explodes.

(Effects of the Present Invention) According to the present invention, since the IEm ratio is set to be small at the time of starting the engine, the engine warms up well, and therefore good startability can be obtained.

(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 rad 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 port 6
An intake valve 7 is combined with the combustion chamber 5, and a spark plug 14 is provided on the opposite side of the combustion chamber 5 from the intake boat 60. An intake passage 8 is connected to the intake port 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 boat 6 in the intake passage 8. Furthermore, an exhaust boat (not shown) is opened in the combustion chamber 5 by a method of lightning, and an exhaust passage 13 is connected to the exhaust boat to form an exhaust system. Further, a valve train system including a cam 15 for operating the liquid valve 7 is engaged with the intake valve 7 . Note that a throttle valve 11 is provided in the intake passage 8.
A bypass passage 16 is connected thereto, and an air bypass control valve 17 is provided to control opening and closing of the bypass passage 16. Furthermore, a sub-cylinder 18 that protrudes upward is continuously formed in the upper part of the combustion chamber 5, and a sub-piston 19 that slides inside the sub-cylinder 18 is disposed. has been done. A stem 19a of the piston 19 projects outward from the sub-cylinder 18, 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 urging 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 is changed, thereby forming a compression ratio variable means. Further, the lead wire 14, a of the spark plug 14 is connected to one terminal of the distributor 25, so that a voltage signal from the ignition coil 26 is applied to the spark plug 14 at a predetermined timing. . The device of this example includes a microcomputer (hereinafter referred to as microcomputer) 27 to control factors governing combustibility. Various information representing the operating state is input to the microcomputer 27. The intake air temperature sensor 28 is installed in the air cleaner 9, detects the air intake air temperature, and sends a signal to the microcomputer 27. Microcomputer 27
The signal from the air flow meter 10 is also input manually.

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. Further, 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 has a cooling water temperature sensor 31, a compression ratio position sensor 532 near the cam 20 serves as a compression ratio detection and output means 7 for detecting the position of the piston 19, and a crank angle sensor 532 on the crankshaft. The transmission 34 is provided with a crank angle sensor 33 for detecting the gear position, a gear position sensor 35 for detecting the gear position of the transmission, and an atmospheric pressure sensor 38 at a predetermined position for detecting atmospheric pressure. All signals from these sensors are input to the microcomputer 27. Further, 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 and the injector 1.
2. Ibukon sotion coil 26, air bypass control solenoid 17a, drive motor 24 for compression ratio control
And a predetermined command signal is output to the transmission control motor 34a. As the transmission, for example, a V-belt type continuously variable transmission can be used, and as the control motor 34a, a conventional type as described in Japanese Patent Laid-Open No. 57-161346 can be used. can.

Further, as shown in FIG. 2, a crank angle sensor 33
The signal is passed through the waveform shaping circuit 'FPf39, where the waveform is shaped and sent to the central processing unit (hereinafter referred to as CPU) 40.
sent to. Signals from other various sensors are converted into digital signals by the A/D converter 41 and input to the CPU 40.

The signal St from the ignition switch 36 is also input to the microcomputer 27, and the S signal Si becomes 1 when the switch 36 is ON, and becomes 0 when the switch 36 is OFF. 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.

Further, the microcomputer 27 includes a counter 1 (43) that constantly counts the time, and can use the time as information as necessary. The CPU 40 determines whether ECR control should be performed based on various input information and outputs an EGR signal Se. The EGR signal Se is sent to the solenoid of the EGR valve 37 via the solenoid drive circuit 44 to control the opening and closing of the liquid valve. When the signal Se is 1, EGR control is performed and the signal Se is 0.
At this time, EGR control is stopped. The microcomputer 27 is equipped with a counter 2 (45) for controlling the fuel injection timing and injection time, and the injection signal Ti is inputted to the injector drive circuit 46 by passing the counter 2 (45) to the injector 12. Activate. Furthermore, the microcomputer 27 controls a counter 3 (47
), and the ignition timing signal Ts is provided with a counter 3 (4
7), thereby generating an ignition signal to the ignition plug 14 at a predetermined timing via the ignition circuit 48, ignition coil 26, and distributor 25. The CPU 40 also determines whether to supply air that bypasses the throttle valve 11, and its control signal Pb is input to the solenoid drive circuit 49. Solenoid drive time Flit 49 C. Solenoid 1 of the air bypass control valve 17 according to IIJ control signal pb
A valve opening/closing command signal is output to 7a. In this case, when the signal pb is 1, the bypass air increases, and when the signal pb is 0, it decreases. Further, the microcomputer 27 controls the motor drive times &! in order to control the operation of the drive motor 24 for compression ratio control. 8
50, and this motor drive circuit 50 is controlled by two control signals M1 and M2. The values of the signal, ML M2, and its control details 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 3G is 1. , it will not turn off unless the signal Sp is set to O.

An example of pressure wI ratio control in the compression ratio control device having the above configuration will be described.

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 figures, the following symbols are used to represent constants or variables.

In the basic program, the engine rotation speed Ne is calculated from the TDC period TJJ (332) calculated in the included routine (S4).

Then, various data representing the operating state are read (35-39). Next, the ratio Q a / N between the engine speed Ne, the intake air amount Qa, and the engine speed Ne
From the map created in relation to e, the compression ratio and other basic quantities of combustibility governing factors corresponding to the operating state are read (810-512). This map is as shown in FIG. 5, for example, regarding the position value Peal of the piston 19 that provides the basic compression ratio. According to this map, the region below the output characteristic curve a is divided into a plurality of small WI regions, and the basic compression ratio position value pcn is set according to each region. This value pce is basically set so that it increases as the rotational speed increases, and decreases as the load increases. Therefore, at low speeds and high loads such as during acceleration (for example, area 11 in FIG. 5), the value P. O is getting smaller. In the area indicated by l in the figure, the value P0 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 T□ and the basic ignition timing T5D, and these basic amounts are set based on them. Next, after a correction operation is performed on the basic compression ratio position value P'C11 set by the above map (
813-523), piston 19 providing the target compression ratio
position value Pc.

is calculated (324). The correction is based on the engine coolant temperature T.
This is done by giving different correction coefficients depending on w, the presence or absence of EGR control represented by the EGR signal Se, atmospheric pressure pt, and intake air temperature Ta. In this case, the engine temperature correction coefficient Cpcw changes with the characteristics shown in FIG. 6 in relation to the engine cooling water temperature Tw. Similarly, the altitude correction coefficient Cpep has the seventh value in relation to the atmospheric pressure Pt.
As shown in the figure, the intake air temperature correction coefficient Cpca is given by the characteristics shown in FIG. 8 in relation to the intake air temperature Ta. 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 Pea becomes smaller, and the lower the atmospheric pressure pt, that is, the higher the altitude, the larger the value Pco. 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, pci, PO2, and PIJ, depending on the magnitude of the calculated value. Furthermore, the basic opening of the air bypass control valve 17 in the relevant operating state is determined from a map prepared in advance based on the engine speed N'e and the ratio Qa/pJe of the intake air amount Qa and the engine speed Ne. degree, that is, the basic air bypass valve position value PaB is calculated (3
31). Furthermore, basic values for setting the gear position of the transmission 34 using a similar map, that is,
The basic 17M gear position value Pg is calculated (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 (S35.5
41). When the target compression ratio position value Pco is positive, that is, when increasing the compression ratio, the control signal is Ml
-1 and M2=1, a correction value is given so that the ignition timing is advanced (S3f3), and a correction value is given so that the bypass air is increased (S3'7).

Furthermore, a correction value is given to increase the fuel injection amount (S38). On the other hand, when the target compression ratio position value Pco is negative, the control signals are set to Ml-1 and M2=0 (
341), unlike the case of increasing the compression ratio, a correction value is given so that the ignition timing is on the delayed side (S42)
At the same time, a correction value is given to reduce the amount of bypass air (S43). 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 (345). Next, in consideration of such a correction command signal, a target position value Pgo of the transmission 34 is calculated (398), and air bypass control valve target position values P and ao are calculated (S99). Furthermore, the ignition timing Ts and the injection amount Ti are calculated (
S 100.5 lots). In this case, although the control signals M1 and M2 for changing the compression ratio are outputted to the drive motor drive circuit 5o, the compression ratio is in a transitional 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 (3103 to SIO6).

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 (3107), and based on the result, the opening degree is calculated. The degree is corrected (3108-5IIO).

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 ratio increases, the ignition timing is shifted to the advanced side, the amount of bypass air is decreased, and a correction amount is given that reduces the amount of injection (S56 to 558). Also, when the compression ratio decreases, the opposite correction amount is given (859~
561).

These correction values are designed to attenuate over time (346-554).

Furthermore, when the compression ratio is changed in an acceleration/deceleration state, corrections are made to the flammability governing factors for a certain period of time in a certain operating region (863 to 584); , corrections are made to reduce bypass air, increase fuel injection amount, and shift 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 (S100 to 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 an operation is performed to lower the compression ratio until the target value is reached (3112-3114).
When the compression ratio drops to the positive control at startup, the compression ratio control motor is stopped (3115) and the controller power is turned off.
It is made FF (3116).

Therefore, according to this example, the piston 19 is always set to a positional position that provides a low compression ratio at the time of starting, so that the engine can be started with good warm-up performance, and the engine startability can be improved.

[Brief explanation of drawings]

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. Figure 7 is a graph showing the relationship between atmospheric pressure and compression ratio position altitude correction coefficient, and Figure 8 is a graph showing the relationship between atmospheric pressure and compression ratio position altitude correction coefficient. It is a graph showing a relationship with a correction coefficient. 1...Piston, 3...Cylinder block, 4...
Cylinder head, 5... Combustion chamber, 8... Intake passage, 1
0...Air flow meter, 1B...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 operating state of the engine; a compression ratio variable means for changing the combustion chamber volume of the engine; Compression ratio control means for controlling the compression ratio variable means to achieve a high target compression ratio; and compression ratio correction means for outputting a control signal to the compression ratio control means to lower the compression ratio when the engine is started. A variable compression ratio engine featuring: