JPS62237044A - Control method for variable compression ratio mechanism of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent knocking of an engine while suppressing its output decrease, by determining a compression ratio-switching boundary value from an engine speed and an intake air quantity and correcting the compression ratio-switching boundary value, when switching is performed from high compression ratio to low compression ratio, so as to quicken the switching to the low compression ratio. CONSTITUTION:An engine, equipped with a variable compression ratio mechanism, sets a high compression ratio operation region and a low compression ratio operation region from a relation between an engine speed, intake air quantity and its ratio to the engine speed. And the engine, in which a boundary value of the both regions is corrected when switching is performed from the high compression ratio region to the low compression ratio region, quickens the switching to the low compression ratio. That is, an electronic control unit 23, which inputs the engine speed NE and the intake quantity Q, discriminates the operation region, but the compression ratio is decided by performing a correction in which a value of b(constant)Xphi is added to Q/NE when a throttle opening speed phi is in a predetermined value or more.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling a variable compression ratio mechanism for an internal combustion engine, which varies the compression ratio according to the operating state of the engine.

[Conventional technology]

In internal combustion engines, increasing the compression ratio improves combustion efficiency, improves fuel efficiency, and improves shaft torque, so it is desirable to increase the compression ratio. However, when the compression ratio is increased, adiabatic compression occurs in the combustion chamber, and when the temperature rises, it becomes easier to ignite and cause knocking (this limits the increase in the compression ratio. This is less likely to occur at light loads when the intake air amount is small and the actual degree of compression in the combustion chamber is small, so the compression ratio is varied according to the load, and the It is desirable to increase the compression ratio, which has been set appropriately for the engine, when the load is light.In this sense, many variable compression ratio mechanisms for internal combustion engines have been proposed.

Proposals related to variable compression ratio mechanisms include a mechanism that calculates the optimum compression ratio according to engine operating conditions, such as Japanese Patent Laid-Open No.
There are proposals such as Publication No. 188056 and Publication No. 196532 of 1983.

Conventional mechanisms for determining the optimal compression ratio have been based on feedback control in which the load and rotational speed are introduced into a control circuit to determine the optimal compression ratio, and the compression ratio is controlled using this output.

[Problem that the invention seeks to solve]

However, the above-described compression ratio control using feedback control has a problem in that control delays occur in response to rapid changes in engine operating conditions. Therefore, when switching the compression ratio from high to low in response to a sudden increase in load, etc., there is a problem in that the compression ratio control cannot follow the rapid change in the operating state, and noaking occurs due to control delay. In addition,
If you want to simply prevent non-king, you can simply delay the ignition timing, but this method has the problem of not generating torque in response to accelerator movement.

An object of the present invention is to provide a variable compression ratio control method that can prevent non-king caused by control delay without reducing output.

[Means for solving the problem] A method for controlling a variable compression ratio mechanism for an internal combustion engine according to the present invention in accordance with this object is a method for controlling a variable compression ratio mechanism for an internal combustion engine in which the compression ratio can be switched between high and low levels. In this step, a boundary value that separates a high compression ratio region and a low compression ratio region of the engine is set from the relationship between the rotation speed of the engine, the intake air amount, and the ratio of the rotation speed of the engine, and the compression ratio is set. When switching from a high compression ratio to a low compression ratio, the boundary value is corrected according to changes in engine operating conditions, and the compression ratio is switched to the low compression ratio side earlier than when the boundary value is not corrected. Consists of a controlled method.

[Effect]

In such a control method for a variable compression ratio mechanism of an internal combustion engine, selection of a high or low compression ratio is performed based on a preset boundary value. If the compression ratio changes from a high compression ratio to a low compression ratio due to a change in the engine load, the boundary value will be corrected according to the change in the engine operating conditions (e.g. throttle opening or opening speed). The compression ratio is quickly lowered based on the corrected boundary value.

Therefore, the delay in compression ratio control becomes smaller, and in effect,
Occurrence of non-king due to control delay is prevented.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for controlling a variable compression ratio mechanism for an internal combustion engine according to the present invention will be described below with reference to the drawings.

3 and 4 show a variable compression ratio mechanism to which the present invention is applied. In the figure, a piston 2 is slidably fitted into a cylinder l of an internal combustion engine, and the piston 2 is connected to a connecting rod 3 via a piston pin 4. The piston pin 4 is fixedly or rotatably supported in the piston pin hole of the piston 2.

Between the piston pin insertion hole 5 at the small end of the connecting rod 3 and the outer periphery of the piston pin 4, there is an eccentric bearing 6 whose wall thickness changes in the circumferential direction and whose inner and outer circumferential circles are eccentric from each other. is rotatably installed.

A lock pin storage hole 7 extending in the radial direction of the eccentric bearing 6 is formed at a position of the connecting rod 3 corresponding to the eccentric bearing 6, and a lock pin 8 is slidably inserted into the hole 7 and inserted from the hole 7. It is housed so that it can freely move in and out of the eccentric bearing 8. On the other hand, in the eccentric bearing 6, a lock pin engagement hole 9 having a diameter that allows the lock pin 8 to move in and out is formed in a thicker portion in the radial direction. When the lock pin 8 engages with the lock pin engagement hole 9, the piston 2 is kept at a high position and a high compression ratio is achieved, and when the lock pin 8 is released, the eccentric bearing 6 freely rotates and compresses. At top dead center, the piston is in a low position, creating a low compression ratio state. That is, this variable compression ratio mechanism allows the compression ratio to be switched between two levels, high and low.

Next, the drive structure of the lock pin 8 will be described. The lock pin storage hole 7 is connected to a lock pin locking hydraulic passage 10 and a lock pin unlocking hydraulic passage 11 with the lock pin 8 in between. Hydraulic passage 1
0 is opened at a position that urges the lock pin 8 in the direction of the eccentric bearing 6.

Furthermore, a lock pin guide groove 12 is formed on the outer periphery of the eccentric bearing 6 at a position corresponding to the loft pin 8 and extends over the entire circumference in the circumferential direction, and the lock pin retaining hole 9 is provided in this groove 12. ing.

The hydraulic pressure i[1 provided in the connecting rod 3
11% 10.11 are respectively communicated with oil grooves 14.15 provided independently on the circumference of the bearing at the large end of the connecting rod. The oil grooves 14.15 are connected to oil grooves 18.19 provided independently on the circumference of the journal bearing of the crankshaft via an oil passage 17 in the crankshaft 16 when the crankshaft 16 rotates. Connected for intermittent communication.

The oil groove 18 can communicate with the lock pin locking hydraulic passage 10 via the oil groove 14, and the oil groove 19 can communicate with the lock pin unlocking hydraulic passage 11 via the oil groove 15.

A main oil passage 20 for high compression ratio and a main oil passage 21 for low compression ratio are provided in the cylinder block, and the main oil passage 20 for high compression ratio is communicated with the oil groove 18, The oil passage 21 communicates with the oil groove 19. Lubricating oil in the oil pan (path shown) is pumped up by an oil pump 26 and sent to either the high compression ratio main oil passage 20 or the low compression ratio main oil passage 21 via the switching valve 22. That is, the switching valve 22 is activated by a signal from the ECU (electronic control unit) 23 depending on the load, and in the case of medium or high loads, pressure oil is sent to the main oil passage 21 for low compression ratios, and for light loads. In this case, the pressure oil is controlled to be sent to the high compression ratio main oil passage 20.

The above-mentioned ECU 23 stores the engine speed NE, intake air amount Q, throttle opening speed ψ, and other engine operating conditions detected by the throttle opening speed detection sensor 25 linked to the accelerator pedal 24 and other sensors. It has been entered.

FIG. 1 shows a block diagram of a control method for a variable compression ratio mechanism of an internal combustion engine according to an embodiment of the present invention, and shows an example of an interrupt routine performed every 180 degrees of crank angle.

As shown in FIG. 1, first, an interrupt is made to the CPU in the ECU 23 at a necessary time, and in step 31, the compression ratio is determined based on the engine operating conditions of the detected engine speed NE and intake air filQ.

That is, in step 31, the compression ratio corresponding to the operating state is read from a map created based on the relationship between the engine speed NE, the intake air amount Q, and the ratio Q/NE of the engine speed NE. As shown in Figure 2, the compression ratio map shows the engine speed NB on the horizontal axis and the ratio Q/NE of the intake air amount Q and engine speed NE on the vertical axis. It has a boundary value C that separates the region A and the low compression ratio region B. When signals are input from the engine speed sensor (indicated path) and air flow meter (indicated path) installed in the engine, it is determined whether the intersection of the corresponding maps is in the high compression ratio region or in the low compression ratio region. It outputs an output indicating whether a high compression ratio or a low compression ratio should be used depending on whether the compression ratio is high or low.

Normally, the compression ratio is set based on the conditions input in step 31, but in order to cope with control delays, the intake air amount Q
and the ratio Q/NE with the engine speed NE is the correction step 3
2, correction is possible.

To explain the correction step 32 in detail, first, in step 33, it is determined whether the flag F is 1 and the compression ratio is high.

Here, if F=O, no correction is performed and the process proceeds to step 37, where the compression ratio is determined. If F-1, the process proceeds to step 34 and the throttle opening speed ψ is input.

Then, in step 35, the throttle opening speed ψ is compared with a preset setting (Ia), and if the result is less than or equal to the set value a (including -), no correction is made and the process proceeds to step 37, where the compression ratio is determined. If ψ>a, the process proceeds to step 36, where Q/NE is corrected by adding, for example, the value of b (constant)×ψ, and the compression ratio is determined.

In step 38, it is determined whether the compression ratio to be controlled should be higher or lower. If the higher compression ratio is selected in step 38, the process proceeds to step 39, where the actual compression ratio is detected, and if the result is a high compression ratio, step 40 is performed.
and will be returned. If the compression ratio is not high, the process proceeds to step 41, where a command to switch to the high compression ratio is output to step 42, and in step 42, the high compression ratio is achieved. When the high compression ratio state is reached, the ignition timing is also adjusted to match the high compression ratio in step 43.

Note that if the lower compression ratio is selected in step 38, the process proceeds to step 44, where the actual compression ratio is detected. As a result, if the compression ratio is not high, the process returns to step 40, and if the compression ratio is high, the process proceeds to step 45, and a command to switch to a low compression ratio is output to step 46. In step 46, a high compression ratio is realized. . Then, in step 47, the ignition timing is adjusted to match the low compression ratio, as described above.

In this way, when the compression ratio is switched from a high compression ratio to a low compression ratio, the intake air amount Q and the engine speed NE
Since the ratio Q/NE of It will be set to the indicated position. Therefore, throttle opening speed ψ
exceeds the set value, that is, when the load increases rapidly, a low compression ratio is implemented early based on the corrected boundary value, and the non-king caused by control delay is eliminated without causing a decrease in output. occurrence is prevented.

[Effects of the Invention] As explained above, when the control method for a variable compression ratio mechanism for an internal combustion engine according to the present invention is used, when the compression ratio is switched from a high compression ratio to a low compression ratio, the operating conditions of the engine are changed. The boundary value is corrected according to the change, and the compression ratio is controlled to be switched to the low compression ratio side earlier than when the boundary value is not corrected, so the delay in compression ratio control is reduced and the load increases rapidly. Even in such a case, it is possible to prevent the occurrence of non-king caused by control delay without causing a decrease in output.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a control method for a variable compression ratio mechanism for an internal combustion engine according to an embodiment of the present invention, Fig. 2 is a compression ratio map diagram, and Fig. 3 is a variable compression ratio mechanism to which the present invention is applied. FIG. 4 is a cross-sectional view of the variable compression ratio mechanism in a direction perpendicular to FIG. 3. ３・・・・・・・・・・・・・・・・・・ Connecting rod 6・・・・・・・・・・・・・・・ Eccentric bearing 8・・・・・・・・・・・・・・・・・・・・・Lock bin 22・・・・・・・・・・・・・・・・・・Switching valve 23・・・・・・・・・・・・・・・・・・・・ECU
(Electronic control unit) 24...
・・・Accelerator NE・・・・・・・・・・・・・・・
Engine speed Q・・・・・・・・・・・・・・・・・・
・Intake air amount A・・・・・・・・・・・・・・・・・・
High compression ratio region B・・・・・・・・・・・・・・・・・・
Low compression ratio area C・・・・・・・・・・・・・・・・・・
Boundary Value Applicant Toyota Motor Corporation Figure 4

Claims (1)

[Claims] (1) In a control method for a variable compression ratio mechanism for an internal combustion engine in which the compression ratio can be switched between high and low levels, a boundary value that separates a high compression ratio region and a low compression ratio region of the engine is determined by the rotation of the engine. The boundary value is set based on the relationship between the number, the intake air amount, and the rotational speed of the engine, and when the compression ratio is switched from a high compression ratio to a low compression ratio, the boundary value is set according to changes in engine operating conditions. A control method for a variable compression ratio mechanism for an internal combustion engine, characterized in that the compression ratio is controlled to be switched to a lower compression ratio side earlier than when the boundary value is not corrected.