JPS628613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable compression ratio mechanism for a reciprocating internal combustion engine in which an eccentric bearing is interposed between a piston pin and a small end of a connecting rod.

Conventionally, by displacing the piston relative to the connecting rod by the amount of eccentricity of the eccentric bearing,
There is a variable compression ratio mechanism that varies the compression ratio of an internal combustion engine. In this variable compression ratio mechanism, in order to switch between a high compression ratio and a low compression ratio, a lock pin that is removably attached to the connecting rod is inserted into and retracted from a pin engagement hole formed in the eccentric bearing. This is done by controlling the rotation of the When protruding the lock pin and fitting it into the pin engagement hole of the eccentric bearing in order to switch to the high compression ratio side, oil is poured into the high compression ratio side of the pressure chamber in which the lock pin is slidably installed. However, at this time, the oil that had flowed into the low compression ratio side of the pressure chamber is not immediately discharged, so the oil on the low compression ratio side acts as a resistance, causing a gap between the high compression ratio side and the low compression ratio side. However, a sufficient hydraulic pressure difference necessary for driving the lock pin cannot be obtained during this period, resulting in the disadvantage that the compression ratio cannot be switched reliably. Similarly, when switching to the low compression ratio side, the oil on the high compression ratio side of the pressure chamber is not immediately discharged, so the switching has the same drawbacks.

The purpose of the present invention is to greatly shorten the compression ratio switching operation time by reliably discharging the oil that creates resistance when driving the lock pin described above.
Another object of the present invention is to provide a variable compression ratio mechanism for an internal combustion engine that can provide high reliability.

A feature of the structure of the present invention is that oil passages for switching between high and low compression ratios are connected to the high compression ratio side and the low compression ratio side of a pressure chamber that is formed in the connecting rod and has a lock pin slidably installed therein. On the other hand, a variable compression engine is constructed so that the oil passages formed in the engine block for switching between high and low compression ratios can be connected to the oil passages of the conrods described above through a single oil passage formed in the crankshaft. In the ratio mechanism, one bypass passage is provided for each of the two oil passages formed in the engine block, and the oil passage on the side where the oil pressure for driving the lock pin is not acting is naturally opened to the atmosphere by a switching valve attached to it. As a result, the oil in the pressure chamber on the side where the hydraulic pressure for driving the lock pin is not acting and the oil in the oil passage are discharged as the crankshaft rotates, making the lock pin drive smooth and reliable. There is a particular thing.

Embodiments of the present invention will be described based on the drawings.

1 to 5 show a first embodiment of the invention. The piston 1 is attached to the small end of the connecting rod 3 via the piston pin 2.
An eccentric bearing 4 is interposed between the connecting rod 3 and the small end of the connecting rod 3. 4a is eccentric bearing 4
The pin engagement hole formed in the figure is shown. A pressure chamber 5 is formed inside the cooking rod 3, and a lock pin 6
is slidably installed inside the pressure chamber 5. The high compression ratio side 5a of the pressure chamber 5 is connected to an oil groove 8a formed in the large end of the connecting rod 3 via an oil passage 7, while the low compression ratio side 5b of the pressure chamber 5 is connected to an oil passage 9.
The oil groove 8b is connected to the oil groove 8b formed in the large end of the connecting rod 3 via the connecting rod 3. crankshaft 10
is rotatably fitted into the large end of the connecting rod 3, and the end is rotatably supported by a bearing portion of the engine block 11. Two oil grooves 12a and 12b are formed in the bearing portion of the engine block 11 to correspond to the aforementioned oil grooves 8a and 8b. Inside the crankshaft 10, there are oil grooves 8a, 8b and 12a, 12.
Oil passages 10a are formed that alternately connect the oil passages 10a and 10b.

The oil groove 12a is connected to the pressure switching valve 15 via an oil passage 13a, a high compression ratio main passage 14, and an oil passage 13b.
6a, low compression ratio main passage 17, oil passage 16b
The pressure switching valve 15 is connected to the pressure switching valve 15 via the pressure switching valve 15. The pressure switching valve 15 has oil passages 18a, 18b, 18c,
It communicates with oil 22 in an oil pan 21 via an oil pump 19 and a suction pipe 20. 23 is an oil return passage. Bypass passages 24 and 25 are connected to the oil grooves 12a and 12b, respectively.
Solenoid valves 26 and 27 are interposed in the bypass passages 24 and 25, respectively. The electromagnetic valves 26 and 27 are connected to the pressure switching valve 15 via lines 28 and 29, and depending on the position of the pressure switching valve 15, one side is open while the other is closed. In addition, in Fig. 3, 30 is Batchiri, 31
is the ignition switch, 32 is the relay, 33
34 is an intake negative pressure switch, 34 is an intake port, 35 is an intake valve, 36 is an exhaust valve, and 37 is a cylinder head.

The action will be explained below.

When the ignition switch is turned on, the pressure switching valve 15 is energized, the engine is started, and the pressure switching valve 15 is activated.

When the intake negative pressure switch 33 detects the negative pressure state of the air-fuel mixture in the intake port 34 and issues a switching signal to the pressure switching valve 15 to switch to a low compression ratio, the pressure switching valve 1
5, the oil is switched to the low compression ratio main passage 17, and at the same time, the solenoid valve 26 of the bypass passage 24 is opened, and the solenoid valve 27 is closed. Therefore, when the crankshaft 10 is located at the position shown in FIG. and tries to flow into the low compression ratio side 5b of the pressure chamber 5. That is, in this state, the pressure on the low compression ratio side 5b of the pressure chamber 5 increases by a constant pressure. Next, the crankshaft rotates, and the oil passage 10a of the crankshaft 10 is connected to the oil groove 8a.
When the oil groove 12a is communicated with the oil groove 12a, the oil in the high compression ratio side 5a of the pressure chamber 5 flows through the oil passage 7 and the oil groove 8.
a, the oil tries to flow into the oil groove 12a through the oil passage 10b. At this time, the solenoid valve 26 of the bypass passage 24 is open to the atmosphere, so the oil groove 12
The oil flowing into a is discharged into the oil pan 21 through a bypass passage 24 and a solenoid valve 26. Next, when the crankshaft 10 rotates and the oil groove 12b and the oil groove 8b communicate with each other again, pressure oil is again supplied to the low compression ratio side 5b of the pressure chamber 5, and the crankshaft 10 further rotates and the oil When the groove 12a and the oil groove 8a communicate with each other, the oil in the high compression ratio side 5a of the pressure chamber 5 is discharged into the oil pan 21 through the bypass passage 24. While the crankshaft rotates several times in this way, a sufficient amount of oil flows into the low compression ratio side 5b of the pressure chamber 5, the lock pin 6 is housed in the connecting rod, and the eccentric bearing 4 can rotate freely. It happens. In this way, the switching to the low compression ratio side is completed. In FIG. 5, the line XX represents the rotation axis of the crankshaft 10, and θ represents the angle between the rotation axis of the crankshaft 10 and the oil passage 10a. Further, A indicates the rotation direction of the crankshaft 10.

Next, the switching operation to the high compression ratio side will be explained.
When the switching valve 15 is switched by the signal issued by the intake negative pressure switch 33 and oil flows into the high compression ratio main passage 14, the solenoid valve 26 of the bypass passage 24 is closed in conjunction with the switching valve 15. The solenoid valve 27 of the bypass passage 25 is opened. Therefore, as the crankshaft 10 rotates, the oil groove 1
2a and the oil groove 8a are connected by an oil passage 10a, and the high compression ratio side 5a of the pressure chamber 5 is connected to the high compression ratio side 5a of the pressure chamber 5 via the oil passage 7.
Oil flows into the tank, creating high pressure. At this time, the oil in the low compression ratio side 5b of the pressure chamber 5 is transferred to the high compression ratio side 5b.
Since the pressure is equal to that of a, the lock pin 6 does not protrude yet. When the crankshaft 10 rotates by a certain angle and the oil passage 10a communicates with the oil groove 8b and the oil groove 12b as shown in FIG. , oil groove 12b, bypass passage 2
5. Open the oil pan 2 to the atmosphere through the solenoid valve 27.
It is discharged during 1. Then, similar to the switching to the low compression ratio side described above, while the crankshaft 10 rotates several times, a sufficient amount and pressure of oil flows into the high compression ratio side 5a, and the oil flows into the low compression ratio side 5b. Since the oil is drained from the hole, the lock pin 6 protrudes smoothly and reliably, and the eccentric bearing 4
It will fit into the pin engagement hole 4a. This completes the switching operation to the high compression ratio side.

FIG. 6 shows a second embodiment of the present invention, and the feature of this embodiment is that the bypass passages 24 and 25 of the first embodiment are eliminated, and a main passage 14 for high compression ratio and a main passage for low compression ratio are used. By using the main passage 17 as it is, a bypass passage 38 attached to the switching valve 15'
The purpose is to switch all at once. Switching valve 1
As 5', a rotary valve or the like can be used. Other operations are similar to those of the first embodiment.

FIG. 7 shows a third embodiment of the present invention, and the feature of this embodiment is that the solenoid valves 26, 27
The pump P is interposed on the oil pan side, thereby forcibly discharging oil from the bypass passage on the side where the solenoid valve is open. Other operations are similar to those of the first embodiment.

FIG. 8 shows a fourth embodiment of the present invention, and the feature of this embodiment is that the outlet of the bypass passage 38 in the second embodiment is connected to the suction side of the oil pump 19. As a result, oil is forcibly discharged through the bypass passage 38. Other operations are the same as in the second embodiment.

As explained above, according to the variable compression ratio mechanism for an internal combustion engine of the present invention, residual oil in the front of the lock pin movement direction is reliably disposed of when switching between the high compression ratio side and the low compression ratio side. The lock pin moves in and out in a short time and reliably, resulting in the effect that the switching of the compression ratio is completed reliably in a short time.

Furthermore, since the present invention has an extremely simple configuration, it has high operational reliability and is highly effective in improving durability and overall performance of the engine.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main part of the variable compression ratio mechanism,
The figures are a sectional view of FIG. 1, FIG. 3 is a sectional view of the cylinder block portion of the variable compression ratio mechanism, FIG. 4 is a partial perspective view of the crankshaft, and FIG. 5 is a perspective view showing the schematic structure of the present invention. 6 is a sectional view of the main part of the second embodiment of the present invention, FIG. 7 is a sectional view of the main part of the third embodiment of the invention, and FIG. 8 is a sectional view of the main part of the fourth embodiment of the invention. FIG. 1... Piston, 2... Piston pin, 3...
Conrod, 4... Eccentric bearing, 5... Pressure chamber, 6... Lock pin, 7, 9, 10a, 13
a, 13b, 16a, 16b, 18a... oil passage, 8a, 8b, 12a, 12b... oil groove,
10...Crankshaft, 15...Switching valve, 2
4, 25... Bypass passage, 26, 27... Solenoid valve, 31... Ignition switch, 33...
Intake negative pressure switch, 34... Intake port.

Claims (1)

[Scope of Claims] 1. A variable compression ratio mechanism for an internal combustion engine in which an eccentric bearing is interposed between a piston pin and a connecting rod, and the eccentric bearing can be fixed by a lock pin that is attached to the connecting rod so as to be able to move in and out.
A bypass passage is provided in a part of a high compression ratio oil passage and a part of a low compression ratio oil passage which are independent from each other for driving the lock pin, and the oil pressure for driving the lock pin acts on the oil passage. A variable compression ratio mechanism for an internal combustion engine, characterized in that only the side of the bypass passage that is not in the closed position is opened to the atmosphere by a valve attached to the bypass passage. 2. Both the oil passages are formed in the connecting rod and the cylinder block, respectively, and the oil passage on the cylinder block side and the oil passage on the connecting rod side are alternately communicated through one oil passage formed in the crankshaft. A variable compression ratio mechanism for an internal combustion engine according to claim 1, characterized in that: 3. The variable compression ratio mechanism for an internal combustion engine according to claim 2, wherein the bypass passage is formed in each of the oil passages on the cylinder block side. 4. The variable compression ratio mechanism for an internal combustion engine according to any one of claims 1 to 3, characterized in that a pump is interposed in the bypass passage.