JPS60230524A - Variable compression-ratio type engine - Google Patents

Abstract

PURPOSE:To effectively prevent the generation of knocking by making the mixed gas rich by increase-correcting the fuel injection amount when compression ratio is varied in acceleration, 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. A compression-ratio position sensor 32 as compression ratio detecting means is provided. 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 an aimed compression ratio is set into the microcomputer 27 according to the engine operation state, and a motor 24 is controlled according to the deviation of the actual compression ratio from the aimed compression ratio. Further, in order to make the mixed gas rich for a prescribed time, when the compression ratio is reduced in acceleration, the valve opening degree of an air bypass control valve 17 is reduced, and the fuel injection amount supplied from an injection valve 12 is increased.

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 knocking 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. However, these conventional devices still have the problem that knocking occurs particularly when changing the compression ratio due to a delay in the operation of the compression ratio control system.

(Objective of the Present Invention) Therefore, an object of the present invention is to provide a variable compression ratio engine capable of solving the problem of knocking caused by delay in operation of the variable compression ratio control system.

(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 a signal from the operating state detecting means using human power. compression ratio control means for outputting a control signal to the compression ratio variable means so that the compression ratio becomes a target compression ratio; The present invention is characterized by comprising an air-fuel ratio correcting means for correcting the air-fuel ratio.

According to the present invention, the engine operating state, such as engine speed, engine load, engine temperature, air-fuel ratio, transmission gear position, acceleration/deceleration state, intake air temperature, etc., is detected by the engine operating state detection means.

(Effects of the Present Invention) According to the present invention, when the compression ratio is lowered during acceleration, the air-fuel mixture is enriched in accordance with the change in the compression ratio.

As a result, even if there is a delay in the operation of the compression ratio control system, a large amount of vaporization heat is taken away from the intake air and the cylinder due to the vaporization of the fuel, suppressing the rise in engine cylinder temperature.
Non-king can be effectively prevented.

(Description of Embodiments) Referring to FIGS. 1 and 2, an engine E to which the present invention is applied includes a cylinder pore 2 in which a piston 1 reciprocates, and the cylinder pore 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 pore 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 1O, 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. 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 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 2o. 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 14a of the spark plug 14 is connected to one terminal of the distributor 25, and the voltage signal from the ignition coil 26 is applied to the spark plug 14 at a predetermined timing. In this example, a microcomputer (hereinafter referred to as microcomputer) 27 is used to control factors governing combustibility. Various information representing the operating state is input to the microcomputer 27. The intake temperature sensor 28 is attached to the air cleaner 9, detects the intake temperature, and sends a signal to the microcomputer 27. A signal from the air flow meter 10 is also input to the microcomputer 27 .

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 has an air bypass control valve opening sensor 3o that detects the opening of the liquid valve 17, the water jacket 3a of the engine E has a cooling water temperature sensor 31, and the water jacket 3a of the engine E has a cooling water temperature sensor 31. , a compression ratio position sensor +32 as compression ratio detection means for detecting the position of the piston 19, and a crank angle sensor 33 for detecting the crank angle on the crankshaft (not shown).
However, the transmission 34 is provided with a gear position sensor 35 that detects the gear position of the transmission 34, that is, a gear position, and an atmospheric pressure sensor 38 that detects atmospheric pressure. All signals 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 performs predetermined calculations on the EGR valve 37, injector 12, ignition coil 26, air bypass control solenoid 17a, drive motor 24 for compression ratio control, and transmission control. A predetermined command signal is output to the motor 34a. As the transmission 34, for example, V
A belt-type continuously variable transmission can be used, and the control motor 34a can be of a normal type as described in Japanese Patent Application Laid-open No. 57-161346.

Further, as shown in FIG. 2, 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 'fR (hereinafter referred to as CPU) 40. 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 when the switch 36 is on, the signal SL becomes 1, and when it is off, the signal SL becomes 0. 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 Se. The EGR signal Se is sent to the solenoid of the EGR valve 37 via the solenoid drive circuit 44 to control 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 includes a counter 2 (45) for controlling fuel injection timing and injection time, and the injection signal Ti is input to the injector drive circuit 46 via the counter 2 (45) to operate the injector 12. let Furthermore, the microcomputer 27 controls a counter 3 (47
), and the ignition timing signal Ts is provided with a counter 3 (
47), 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. The solenoid drive circuit 49 outputs a valve opening/closing command signal to the solenoid 17a of the air bypass control valve 17 in response to the control signal pb. In this case, when the signal pb is 1, the bypass air increases, and when the signal pb is 0, it decreases. The microcomputer 27 also includes a motor drive circuit 50 for controlling the operation of the drive motor 24 for compression ratio control, and this motor drive circuit 50 is controlled by two control signals M1 and M2. It has become. The values of the signals Ml and M2 and their control contents are shown in Table 1.

Table 1 The transmission 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. Signal M3, M4
The relationship between the value of and the gear ratio is 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 Sl 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 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 Tff (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 pcθ 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 regions, and the basic compression ratio position value pce is set according to each region. This value PCB is basically set so that it increases as the rotational speed increases, and decreases as the load increases. In the figure, the area indicated by l has a relatively small value PCB, the area indicated by h has a relatively large value, and the area indicated by m has an intermediate value. Similar master knobs are prepared for the basic fuel injection amount T18 and the basic ignition timing "l" SR, and these basic amounts are set based on them. Next, the basic compression ratio position value P is set using the above map. After the correction operation for B is performed (313-523), the position value Pco of the piston 19 that provides the target compression ratio is calculated (324). The correction is based on the presence or absence of EGR control indicated by the engine coolant temperature TwSEGR signal Se, the atmospheric pressure pt, and the intake air temperature T.
This is done by giving different correction coefficients depending on a.

In this case, the engine temperature correction coefficient Cp changes with the characteristics shown in FIG. 6 in relation to the engine coolant temperature Tw. Similarly, the altitude correction coefficient Cpcp is the atmospheric pressure pt
In relation to the intake air temperature Ta, the intake air temperature correction coefficient Cpca is given as a characteristic as shown in FIG. 7, and as 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 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 PcoO value becomes small. In this example, the target compression ratio position value Pco is set to one of three different values, PCl, PO2, and PO3, depending on the magnitude of the calculated value. Furthermore, the ratio Q a of the engine speed Ne to the intake air amount Qa and the engine speed Ne
The basic opening degree of the air bypass control valve 17 in the relevant operating state, that is, the basic air bypass valve position value p
an is calculated (531). Furthermore, a basic value for setting the gear position of the transmission 34 using a similar MA knob, that is, a basic T/M gear position value P
gB is calculated (S32). Next, the position of the piston 19 giving the actual compression ratio, that is, the deviation △ between the actual compression ratio position value Pc and the target compression ratio position value Pco.
Pc is calculated (333). According to the value of this deviation Pc, 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 signals are set to M1=1 and M2=1, and a correction value is given so that the ignition timing is advanced. (S36), and a correction value is given to increase the bypass air (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 M1
=1. M2=O (S41), and unlike the case where the compression ratio is increased, a correction value is given so that the ignition timing is on the retarded side (S42), and a correction value is given so that the bypass air is reduced ( 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 an air bypass control valve target position value Pao is calculated (398).
99). Further, the ignition timing TS1 and the injection amount T1 are calculated (S100.3101). 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 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 (S l O, 2). Based on this result, the gear ratio is corrected (3103-3106).

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 (3108-5ILO).

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 (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 (846-554).

Furthermore, when a change in the compression ratio occurs in an acceleration/deceleration state, corrections are made to the flammability governing factors for a certain period of time in a certain operating region (863-384); Corrections are given 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 (S100-5102).

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 (S115) and the controller power is turned off (S116).

According to this example, when the compression ratio is lowered during acceleration, the fuel injection amount is corrected to increase, so that the air-fuel mixture is enriched. Since this fuel absorbs a large amount of heat of vaporization from the surroundings, the temperature rise inside the cylinder is appropriately suppressed, and knocking can be prevented.

[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, and FIG.
Figures 3B, 3C, 3D, 3E and 4
The figure is a flowchart showing the details of control according to one embodiment of the present invention, FIG. 5 is a graph showing the relationship between target compression ratio and engine load and engine speed, and FIG. 6 is a graph showing the relationship between cooling water temperature and compression ratio position of the engine. Figure 7, a graph showing the relationship between temperature correction coefficient, shows the relationship between atmospheric pressure and compression ratio position height.
FIG. 8 is a graph showing the relationship between the intake air temperature and the compression ratio position intake temperature correction coefficient. 1...Piston, 3...Cylinder block, 4...
Cylinder head, 5... Combustion chamber, 8... Intake passage, l
O...Air flow meter, 18...Sub-cylinder, 1
9... Sub-piston, 27... Microcomputer, 33...
Crank angle sensor, 40...CPU, 41...A/
D converter. Figure 3E Figure 4 Figure 6 Figure 7 Figure 8 a Enter! Steam JLTa

Claims (1)

[Claims] an operating state detection means for detecting the operating state of the engine; a compression ratio variable means for changing the volume of the combustion chamber of the engine; Compression ratio control means for outputting a control signal to the compression ratio variable means; and air-fuel ratio correction means for enriching the air-fuel mixture for a predetermined period of time in response to a change in the compression ratio when the compression ratio is lowered during acceleration. A variable compression ratio engine.