JPS63117129A - Controlling method for compression ratio of variable compression ratio mechanism - Google Patents

Abstract

PURPOSE:To prevent the malfunction of a lock pin by preferentially changing compression ratio over to the side of low compression ratio when oil pressure for driving said lock pin has decreased. CONSTITUTION:An eccentric hearing 6 is rotatably positioned between a connecting rod 3 and a piston pin 4, and a lock pin 8 provided on said connecting rod 3 is hydraulically driven to change compression ratio. A hydraulic sensor 32 detects oil pressure in the above hydraulic system, and then inputs it into an electronic controller 23, and when said oil pressure is lower than its specified value, a directional control valve 22 is operated to change the compression ratio over to the side of low compression ratio. The malfunction of said lock pin 8 can be therefore prevented to check the damage of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling a variable compression ratio mechanism of an internal combustion engine using an eccentric bearing.

[Conventional technology]

A variable compression ratio mechanism has previously been proposed in which an eccentric bearing is interposed between the connecting rod and the piston pin, and the rotation of the eccentric bearing changes the relative position of the piston with respect to the connecting rod, thereby making the compression ratio variable (for example, Publication No. 58-172431).

Figures 6 and 7 show an example of a conventional variable compression ratio mechanism. In Figure 0, a piston 2 is slidably inserted into the cylinder 1, and the reciprocating movement of the piston 2 is controlled by a connecting rod. 3 to the crankshaft.

Between the piston pin 4 and the connecting rod 3,
An eccentric bearing 6 consisting of a cylindrical body whose inner and outer circumferences are eccentric with respect to each other is installed, and the relative position of the piston 2 with respect to the connecting rod 3 is changed depending on the amount of rotation of the eccentric bearing 6, thereby making the compression ratio variable. ing.

The eccentric bearing 6 is provided with a lock pin holding hole 9 which is a hole extending in the radial direction, and the connecting rod 3 is provided with a lock pin storage hole 7 in which a lock pin 8 is inserted. is slidably inserted. The lock pin 8 moves in and out of the lock bin retaining hole 9 by hydraulic pressure to lock or free rotation of the eccentric bearing 60.

A lock pin lock hydraulic passage 10 is connected to the lock pin storage hole 7 at a position where the lock pin 8 can be driven in the direction of the eccentric bearing 6, and a lock pin lock hydraulic passage 10 is connected to the lock pin storage hole 7 at a position where the lock pin 8 can be driven in the direction away from the eccentric bearing 6. A lock hydraulic passage 11 is connected thereto. Hydraulic passage for lock pin long 10. Hydraulic pressure is applied to the lock bin unlocking hydraulic passage 11 by a switching valve (path shown), and the switching valve is equipped with an oil pump (path shown).
Pressure oil is sent through it. Pressure oil from the oil pump is switched in a predetermined direction by a switching valve, including oil grooves 18 and 19 formed in the crank journal bearing, an oil passage 17 in the crankshaft 16, and an oil groove in the large end bearing of the connecting rod 3. 14 and 15, it is sent to the lock bin locking hydraulic passage 10 and the lock bin unlocking hydraulic passage 11.

In the variable compression ratio mechanism configured in this way, when the load is high, pressure oil is sent to the lock bin unlocking hydraulic passage 11, the lock pin 8 is removed from the lock bin retaining hole 9, and the eccentric bearing 6 is locked. will be released and become free. At this time, the piston receives compressed gas pressure and explosive force near the compression top dead center, and automatically rotates the eccentric bearing 6 to maintain a low position relative to the connecting rod 3, resulting in a low compression ratio.

Also, under light or medium load conditions, pressure oil is sent to the hydraulic passage 10 for locking the lock pin, and when the eccentric bearing 6 rotates and the lock pin retaining hole 9 comes to the position corresponding to the lock pin 8, the lock is activated. The pin 8 enters the lock pin engagement hole 9 and locks the rotation of the eccentric bearing 6. At this time, the piston 2 is locked at a high position relative to the connecting rod 3, resulting in a high compression ratio.

[Problem that the invention seeks to solve]

In order for the eccentric bearing to lock and unlock smoothly, the lock pin must be hydraulically driven smoothly.However, if the temperature of the lock pin drive oil rises excessively or the hydraulic passage is damaged. In this case, a problem arises in that the oil pressure cannot rise to the set level when switching the compression ratio. In addition, there may be a situation in which the oil pressure drops that cannot be controlled during the use process due to oil deterioration, clogging of the filter in the oil passage, or too low engine speed.

If you try to control the lock pin in the same way as normal when the oil pressure is low, it will cause the lock pin to malfunction, reducing the reliability of the variable compression ratio mechanism and impairing the durability of the mechanism. A problem arises.

Note that in a variable compression ratio mechanism using an eccentric bearing, switching the compression ratio from a high compression ratio to a low compression ratio is easier than switching the compression ratio from a low compression ratio to a high compression ratio. In other words, it is easier to remove a lock pin from a locked eccentric bearing than to engage a lock pin to a rotating eccentric bearing.
Even if the oil pressure applied to the lock pin decreases to some extent, switching to a low compression ratio can be performed reliably.

The present invention focuses on the above-mentioned problem, and prevents the lock pin from malfunctioning when the pressure of the oil for driving the lock pin drops below a predetermined pressure, and improves the reliability and durability of the variable compression ratio mechanism. The purpose is to provide a control method that can

[Means for solving problems]

The compression ratio control method of the variable compression ratio mechanism of the present invention that meets this purpose includes rotatably interposing an eccentric bearing between a connecting rod and a piston pin, and hydraulically driving a lock pin provided on the connecting rod side. In the compression ratio control method of a variable compression ratio mechanism in an internal combustion engine, the compression ratio is switched to a high compression ratio or a low compression ratio by locking or unlocking the eccentric bearing, in which the lock pin is hydraulically driven. The control method consists of constantly measuring the oil pressure, and controlling the compression ratio to be preferentially switched to the low compression ratio side if the oil pressure falls below a preset pressure.

[Effect]

In the compression ratio control method of the variable compression ratio mechanism configured in this way, the pressure of the oil for driving the lock pin is constantly measured, and if the oil pressure drops below a predetermined pressure, even if the load conditions are met, Even if a higher compression ratio is selected, the compression ratio is controlled to be switched to the lower compression ratio side with priority.In other words, the compression ratio is switched to the lower compression ratio side where the lock pin is reliably activated. Malfunction of the lock pin is prevented and reliability of the variable compression ratio mechanism is increased.

〔Example〕

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

First Embodiment FIG. 3 shows an example of a variable compression ratio mechanism for an internal combustion engine to which the compression ratio control method according to the first embodiment of the present invention is applied. The conventional structures shown in FIGS. 6 and 7 are also applied to the embodiment of the present invention.

In the third @, the cylinder 1 of the internal combustion engine has a piston 2
is slidably inserted therein, 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 retaining hole 9 having a diameter that allows the lock pin 8 to be inserted and retracted is formed in a thicker portion in the radial direction. When the lock pin 8 engages with the lock pin retaining 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, in this variable compression ratio mechanism, the compression ratio can be switched to two levels, high and low.

Next, the drive structure of the lock pin 8 will be described. A lock pin locking hydraulic passage lO and a lock pin unlocking hydraulic passage 11 are connected to the lock pin storage hole 7 with the lock pin 8 interposed therebetween.
is opened at a position that urges the lock pin 8 in the direction of the eccentric bearing 6.

Further, on the outer periphery of the eccentric bearing 6, a lock pin guide is provided at a position corresponding to the lock pin 8, and extends over the entire circumference in the circumferential direction. 112 is formed, and this groove 12 is provided with the lock pin retaining hole 9.

The hydraulic passage 1 provided in the connecting rod 3
0.11 are in communication with oil grooves 14 and 15 provided independently from each other on the circumference of the bearing at the large end of the connecting rod. The oil grooves 14 and 15 are connected to the crankshaft 1.
Oil grooves 18.6 are provided independently on the circumference of the journal bearing of the crankshaft via oil passages 17 in oil grooves 18.6.
19 so that they can communicate intermittently when the crankshaft 16 rotates.

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 ratios and a main oil passage 21 for low compression ratios are provided in the cylinder block, and the main oil passage 20 for high compression ratios communicates with the oil groove 18, The main oil passage 21 communicates with the oil groove 19. Oil 31 in the oil pan 30 is pumped up by the 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.

The switching valve 22 is controlled by the ECU (electronic control unit) 2 according to the load.
When the load is medium or high, pressure oil is sent to the main oil passage 21 for low compression ratio, and when the load is light, pressure oil is sent to the main oil passage 2 for high compression ratio. controlled to be sent.

The intake air amount Q detected by the air flow meter 24 and the engine rotation speed NB detected by the engine rotation speed sensor 25 are input to the ECU 23, respectively. That is, the ECU 23 is configured to operate the switching valve 22 in response to input signals of the intake air amount Q and the engine speed NE to switch the compression ratio.

The ignition control device consists of an igniter (ignition control circuit) 27 and an ibnirasilane coil (path shown), and the igniter 27 is connected to an output port of the ECU 23 to receive and receive an ignition signal. Ibnira Silan Coil is
It is connected to the center electrode of the distributor 2, and high voltage is distributed to the spark plugs 29 of each cylinder according to the rotation of the distribution shaft.

Further, an oil pressure sensor 32 is connected to the ECU 23 and constantly measures the pressure of oil 31 that hydraulically drives the lock bin 8.
It is located directly upstream of the And the above ECU23
The oil 31 necessary to drive the lock bin 8 is
The pressure value PL is stored in advance.

FIG. 1 shows a flowchart of compression ratio switching control in the first embodiment.

As shown in FIG. 1, for example, an interrupt is made to the CPU 23a in the ECU 23 every 180 degrees of crank angle, and in step 41, the pressure P of the oil 31 that drives the lock bin 8 measured by the oil pressure sensor 32 is input. . Next, the process proceeds to step 42, where the pressure P of the oil 31 is compared with a preset pressure value PL.

If the result is PL≦P, the process proceeds to step 43; otherwise, the process proceeds to step 51, which will be described later.

In step 43, engine speed NE and intake air amount Q are input as engine operating conditions, and in step 44, the compression ratio is determined. Figure 2 shows a compression ratio map, and as shown in the figure, the horizontal axis shows the engine speed NB, and the vertical axis shows the ratio Q/N E between the intake air amount Q and the engine speed NE.
The graph has a boundary value C that separates the high compression ratio region A and the low compression ratio region B. therefore,
In step 44, when signals from the engine speed sensor 25 and air flow meter 24 are input, high compression is determined depending on whether the intersection of the corresponding maps is in the high compression ratio region A or the low compression ratio region B. It outputs an output indicating whether a high compression ratio or a low compression ratio should be used.

Once the compression ratio ε is determined in step 44, the process proceeds to step 45 where it is determined whether the determined compression ratio ε is a high compression ratio or a low compression ratio. If the higher compression ratio is selected in step 45, the process proceeds to step 46, where the currently controlled compression ratio is detected, and if the result is a high compression ratio, the process proceeds to step 47 and returns. If the compression ratio is not high, the process proceeds to step 4 and a high compression ratio is achieved in step 48.

When the compression ratio is switched to a high compression ratio, the process proceeds to step 49, where the ignition timing is changed to high compression ratio, and in step 50, the compression ratio flag is set to F-1, and the process returns to step 47.

Note that if the lower compression ratio is selected in step 45, the process proceeds to step 51 and the actual compression ratio is detected. As a result, if the compression ratio is not high, the process returns to step 47, and if the compression ratio is high, the process proceeds to step 52, where a low compression ratio is achieved.

When the compression ratio is switched to a low compression ratio, the process proceeds to step 53, in which the ignition timing is changed to one for the low compression ratio, and in step 54, the compression ratio flag is set to F-0, and the process returns to step 47. Note that if the pressure P of the oil 31 is lower than the set pressure value PL in step 42, the process proceeds to step 51 as described above, and the compression ratio is switched to the low compression ratio side.

In this way, when the measured pressure P of the oil 31 is lower than the set pressure value PL, the compression ratio is changed to 771 shown in FIG.
Regardless of the conditions shown in the figure, the compression ratio is switched preferentially to the low compression ratio side.

Second Embodiment FIGS. 4 and 5 show a compression ratio control method for a variable compression ratio mechanism according to a second embodiment of the present invention, and the configuration of a hydraulic passageway to which this control method is applied.

The second embodiment differs from the first embodiment in the method of detecting oil pressure and the configuration of the hydraulic passage, and the rest is the same as the first embodiment, so a description of the similar parts will be omitted.

In FIG. 5, Pl+7 indicates the pressure detected by the oil pressure sensor 32. In this embodiment, the oil pumped up from the oil pump 26 is used for compression ratio control and for lubricating various parts of the engine. . That is, in this embodiment, two oil pressure sensors 32 are provided, and one sensor measures the pressure in the compression ratio oil pressure passage 41,
The other sensor is connected from the compression ratio hydraulic passage 41 to the orifice 4.
2 to measure the pressure in a hydraulic passage 43 connected to the cylinder head.

FIG. 4 shows a flow diagram of compression ratio switching control in the second embodiment.

As shown in FIG. 4, for example, an interrupt is made to the CPU 23a in the ECTJ 23 every 180 degrees of crank angle.
In step 61, the pressure P of the oil 31 that drives the lock pin 8 and the pressure P of the hydraulic passage 43 connected to the cylinder head are determined! is measured and input by two oil pressure sensors 32. Next, proceeding to step 62, the pressure P of the oil 31,
, PR is compared with a pressure setting value P0 stored in the ECU 23 in advance. The result is P+ −K (P+
If Pg)≧P0, the process proceeds to step 63; otherwise, the process proceeds to step 71, which will be described later. Here, K above indicates a coefficient due to the orifice.

In step 63, the engine speed NE and intake air amount Q are input as engine operating conditions, and in step 64, the compression ratio is determined based on the map shown in FIG.

Once the compression ratio ε is determined in step 64, the process proceeds to step 65, where it is determined whether the determined compression ratio C is a high compression ratio or a low compression ratio. If the higher compression ratio is selected in step 65, the process proceeds to step 66, where the currently controlled compression ratio is detected, and if the result is a high compression ratio, the process proceeds to step 67 and returns. If the high compression ratio has not been reached, the process proceeds to step 68, where the high compression ratio is achieved.

When the compression ratio is switched to a high compression ratio, the process proceeds to step 69, where the ignition timing is changed to one for the high compression ratio, and in step 70, the compression ratio flag is set to F-1, and the process returns to step 67.

Note that if the lower compression ratio is selected in step 65, the process proceeds to step 71 and the actual compression ratio is detected. As a result, if the compression ratio is not high, the process returns to step 67, and if the compression ratio is high, the process proceeds to step 72, where a low compression ratio is achieved.

When the compression ratio is switched to a low compression ratio, the process proceeds to step 73, in which the ignition timing is changed to one for the low compression ratio, and in step 74, the compression ratio flag is set to F-0, and the process returns to step 67. Note that in step 62, the estimated pressure P of the oil 31 is determined.

If K(P+Pz) is lower than the set value P,
As described above, the process proceeds to step 71, where the compression ratio is switched to the low compression ratio side.

In this way, in the second embodiment, the oil pressure applied to the lock pin 8 due to the oil pressure drop caused by the orifice 42 is estimated, and the estimated pressure value -PI-K (P, -Pt) is calculated as the pressure setting value P stored in advance in the ECU 23. .

If the compression ratio is lower than , the compression ratio is preferentially switched to the lower compression ratio side, and malfunction of the lock pin 8 is prevented.

Note that the above-described orifice 42 may be provided with a specially manufactured one, or may be replaced with a corresponding part.

〔Effect of the invention〕

As explained above, when using the compression ratio control method of the variable compression ratio mechanism of the present invention, the pressure of the oil that hydraulically drives the lock pin is measured, and if this pressure falls below a preset pressure, Since the compression ratio is controlled to be switched preferentially to the low compression ratio side, malfunction of the lock pin is prevented, and the reliability of the variable compression ratio mechanism is increased.
The durability of the mechanism can be increased.

In addition, if an orifice is provided in the hydraulic passage flowing to the cylinder head side and the pressure difference between the oil pressure on the upstream and downstream sides of the orifice is measured to estimate the pressure actually acting on the lock pin, the hydraulic pressure can be further improved. This makes it possible to accurately capture fluctuations in , increasing reliability. Furthermore, by providing the orifice, oil does not flow excessively toward the cylinder head, so it is possible to increase the oil pressure for the variable compression ratio.

[Brief explanation of the drawing]

FIG. 1 shows the flow of compression ratio control according to the first embodiment of the present invention.
Figure A and Figure 2 are compression ratio switching map diagrams according to the present invention, Figure 3 is a control system diagram of an internal combustion engine equipped with a variable compression ratio mechanism to which the present invention is applied, and Figure 4 is a second embodiment of the present invention. A flow diagram of compression ratio control according to an example, FIG. 5 is a schematic diagram of a hydraulic passage of a variable compression ratio mechanism to which control based on the flow diagram of FIG. 4 is applied, and FIG. 6 is a conventional variable compression ratio mechanism. A sectional view showing an example. FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6. 3......Connecting rod 6.
・・・・・・・・・・・・Eccentric bearing 8・・・・・・
・・・・・・Lock pin 10・・・・・・・・・・・・
Hydraulic passage for lock bin lock 11...
...Hydraulic passage for rotter pin unlock 22...
......Switching valve 23...ECU (electronic control unit) 23a...CPtJ 24......・Air flow meter 25・
...... Engine speed sensor 27...
・・・・・・・・・Igniter (ignition control circuit) 28
・・・・・・・・・・・・Distributor 29...
・・・・・・・・・Spark plug 32・・・・・・
......Oil pressure sensor NE......Engine speed Q......At the time of intake air amount Applicant: Toyota Motor Corporation, Figure 1 Figure 2 Rotation Engine rotation speed Ratio to HE number

Claims (1)

[Claims] (1) An eccentric bearing is rotatably interposed between a connecting rod and a piston pin, and a lock pin provided on the connecting rod side is hydraulically driven to lock or unlock the eccentric bearing and compress In a compression ratio control method for a variable compression ratio mechanism in an internal combustion engine in which the ratio is switched to a high compression ratio or a low compression ratio, the pressure of oil that hydraulically drives the lock pin is constantly measured, and the pressure of the oil is set in advance. 1. A compression ratio control method for a variable compression ratio mechanism, characterized in that the compression ratio is controlled to be switched preferentially to a lower compression ratio side when the pressure is lower than the specified pressure.