JPH048274Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable compression ratio mechanism for an internal combustion engine using an eccentric bearing, and more particularly to a hydraulic passage for driving a lock pin for reliably switching the compression ratio.

[Conventional technology]

One mechanism for varying the compression ratio in an internal combustion engine is to interpose an eccentric bearing between the piston pin and the connecting rod, and angularly displace the eccentric bearing to raise or lower the relative position of the piston to the connecting rod. There is a compression ratio variable mechanism that allows for variable settings (for example, Japanese Patent Application Laid-Open No. 58-91340
Publication No.).

The compression ratio variable mechanism using eccentric bearings is the fourth
As shown in Fig. 5, eccentric bearing 1
A lock pin engagement hole 2 is provided in the connecting rod 3, a lock pin storage hole 4 is provided in the connecting rod 3, a lock pin 5 is stored in the lock pin storage hole 4, and the lock pin 5 is inserted into the engagement hole by applying hydraulic pressure to the lock pin 5. The lock pin 5 is engaged with and disengaged from the lock pin engagement hole 2 by being driven forward and backward in the direction.

The lock pin storage hole 4 includes a hydraulic passage 6 for locking the lock pin and a hydraulic passage 7 for unlocking the lock pin.
When the load is light, oil is forced into the lock pin lock hydraulic passage 6 to lock the eccentric bearing and create a high compression ratio state. Also, when the load is high enough to cause knocking, oil is forced into the lock pin unlocking hydraulic passage 7 and the eccentric bearing 1
The lock is released, the eccentric bearing 1 rotates, and a low compression ratio state is created.

A hydraulic passage 6 for locking the lock pin and a hydraulic passage 7 for unlocking the lock pin are formed on the circumference of the crank pin bearing portion 8 of the connecting rod 3.
It is connected to two independent oil grooves 9 and 10. These two oil grooves 9 and 10 are connected to two independent oil grooves 1 formed on the circumference of the crank journal bearing part 12 via an oil hole 11 in the crankshaft 17.
3 and 14. And oil groove 13,
14 is a hydraulic passage 15 for low compression ratio control and a hydraulic passage 1 for high compression ratio control formed in the cylinder block.
6, respectively.

In such a variable compression ratio mechanism, when the compression ratio is switched to the high compression ratio side, the oil pumped from the high compression ratio control hydraulic passage 16 to one oil groove 13 on the crank journal side is transferred to the crankshaft. It reaches the lock pin 5 side through the oil hole 11 of 17, one oil groove 9 on the crank pin bearing side, and the lock pin lock hydraulic passage 6, and the lock pin 5 is pushed toward the eccentric bearing 1 side by this oil pressure, and the eccentric bearing 1 is locked. In this case, in order to reliably engage the lock pin 5 with the lock pin engagement hole 2 of the eccentric bearing 1, it is necessary to apply hydraulic pressure to the lock pin 5 at an appropriate crank angle.

[Problem that the invention attempts to solve]

However, in the case of the above-mentioned hydraulic lock mechanism, in the high rotation range of the engine, there is a delay in the transmission of hydraulic pressure at the oil hole in the crankshaft due to the effects of air bubbles mixed in the oil, and the lock pin operation timing is delayed. The problem arises that there is a delay. As a result, it becomes difficult to fit the lock pin into the lock pin engagement hole of the eccentric bearing, resulting in a problem that it becomes impossible to switch the compression ratio to a high compression ratio.

The present invention focuses on the above-mentioned problems and compensates for the lock pin activation delay caused by the hydraulic pressure transmission delay.
It is an object of the present invention to provide a hydraulic passage structure capable of reliably locking an eccentric bearing even in a high rotation range of an engine.

[Means for solving problems]

The hydraulic passage of the variable compression ratio mechanism of the present invention that meets this purpose includes an eccentric bearing rotatably interposed between the piston pin and the connecting rod, a lock pin engagement hole provided in the eccentric bearing, and a connecting rod. A lock pin that goes in and out of the lock pin engagement hole is provided on the rod side, and an oil groove formed on the circumference of the crank pin bearing portion of the connecting rod and an oil groove formed on the circumference of the crank journal bearing portion are provided. , communication is possible through an oil hole formed in the crankshaft, and by applying hydraulic pressure to the lock pin through the oil hole and oil groove, the lock pin is engaged with or disengaged from the lock pin engagement hole, thereby rotating the eccentric bearing. In the hydraulic passage of the variable compression ratio mechanism that locks or unlocks the oil pressure, the timing at which communication between the oil groove on the crank journal bearing side and the oil hole starts is controlled by the oil groove on the crank pin bearing side and the oil hole. It consists of items that preceded the start of communication.

[Effect]

In the hydraulic passage of the variable compression ratio mechanism configured in this way, the timing at which communication between the oil groove and oil hole on the crank journal bearing side starts is longer than the timing at which communication between the oil groove and oil hole on the crankpin bearing side starts communicating. Since the lock pin is moved earlier, the lock pin operates earlier, and the delay in lock pin operation caused by the delay in hydraulic pressure transmission is compensated for. Therefore, the lock pin is actuated quickly at an appropriate crank angle, and the eccentric bearing is reliably locked even in the high engine speed range.

〔Example〕

Hereinafter, preferred embodiments of the variable compression ratio mechanism hydraulic passage according to the present invention will be described with reference to the drawings.

1 and 2 show a hydraulic passage of a variable compression ratio mechanism according to an embodiment of the present invention. 1st
In the figures and FIG. 2, a piston 21 is slidably inserted into a cylinder 22, and the reciprocating motion of the piston 21 is converted into rotational motion of a crankshaft 25 via a piston pin 23 and a connecting rod 24. be done.

Connecting rod 24 and piston pin 23
An eccentric bearing 26 whose inner and outer circumferences are mutually eccentric is interposed between the eccentric bearing 2 and
The compression ratio is changed according to the amount of rotation of the engine. A lock pin engagement hole 27 extending in the radial direction is bored in the eccentric bearing 26, and a lock pin 28 is disposed on the connecting rod 24 side. The lock pin 28 is slidably housed in a lock pin housing hole 29, and is moved by the differential pressure between two hydraulic passages 30 and 31 formed in the connecting rod 24 for driving the lock pin. One hydraulic passage 30 is a hydraulic passage for a lock pin lock that drives the lock pin 28 in the direction of the eccentric bearing 26, and the other passage 31
is a hydraulic passage for unlocking the lock pin that drives the lock pin 28 in a direction away from the eccentric bearing 26.

The lock pin locking hydraulic passage 30 and the lock pin unlocking hydraulic passage 31 communicate with mutually independent oil grooves 32 and 33 formed on the circumference of the crank pin bearing portion 35 of the connecting rod 24, respectively. The oil grooves 32 and 33 can communicate with mutually independent oil grooves 38 and 39 formed on the circumference of the crank journal bearing 36 via an oil hole 34 formed in the crankshaft 25.

The oil hole 34 communicates the oil groove 32 and the oil groove 38 in the half rotation range of the crankshaft 25, and communicates the oil groove 33 and the oil groove 39 in the other half rotation range of the crankshaft 25. It's getting old.

The oil groove 38 is connected to a high compression ratio control hydraulic passage 41 formed in the cylinder block 40, and the oil groove 39 is connected to a low compression ratio control hydraulic passage 42 similarly formed in the cylinder block 40. ing. The hydraulic passage 41 for high compression ratio control and the hydraulic passage 42 for low compression ratio control include an oil pan (not shown).
Oil pumped up by an oil pump (not shown) and set at a predetermined pressure is pumped through the switching valve 43.

FIG. 3 shows the lock pin hydraulic drive timing. In other words, it shows the state of communication between the oil hole in the crankshaft and each oil groove at high compression ratios and at low compression ratios. In FIG. 3, A ₁ and A ₂ indicate the communication timing between each oil groove and oil hole for switching to the high compression ratio side. A ₁ indicates the timing of communication between the oil groove 38 and the oil hole 34 on the side of the crank journal bearing 36, and A ₂ indicates the timing of communication between the oil groove 32 and the oil hole 34 on the side of the crank pin bearing 35. There is.
As shown in the figure, the communication period _A1 is longer than the communication period _A2 , and the communication start point P of the communication period _A1
The communication timing is advanced by θ ₁ in terms of crank angle compared to the communication start point Q at the communication timing A ₂ .

That is, the communication starting point P in FIG. 3 indicates A in FIG. 34 and the oil groove 32 on the crank pin bearing side are not yet in communication with each other.
The communication starting point Q in FIG. 3 indicates B in FIG. The oil hole 32 on the bearing side is opened immediately after communication starts.

B ₁ and B ₂ in FIG. 3 indicate the communication timing between each oil groove and oil hole for switching to the low pressure welding ratio side. In other words, B ₁ is the oil groove 3 on the crank journal bearing side.
9 and the oil hole 34, and _B2 shows the timing when the oil groove 33 on the crank pin bearing side communicates with the oil hole 34. In this case as well, similarly to the above, the communication start time of the communication time _B1 is earlier than the communication start time of the communication time _B2 by _θ1 in terms of crank angle.

In this embodiment, the means for advancing the communication start timing is achieved by extending the oil groove 38 on the high compression ratio side and the oil groove 39 on the low compression ratio side in the opposite direction to the rotational direction of the crankshaft 25. There is.

Next, the operation of the variable pressure welding ratio mechanism in the hydraulic passage will be explained.

Not shown when the engine is under light load
An activation signal is output from the ECU (electronic control unit) to the switching valve 43, and the switching valve 43 is switched to one side.
As a result, the pressure oil is sent under pressure to the oil groove 38 via the switching valve 43 and the high compression ratio control hydraulic passage 41, and the pressure oil is further transferred from the oil groove 38 to the oil hole 34 of the crankshaft and the oil groove 32. The oil is intermittently sent to the lock pin lock hydraulic passage 32 through the lock pin. In this case, the oil groove 38 and oil hole 34 on the crank journal bearing side
The communication start point P of _A1 is the communication timing between the oil groove 32 and the oil hole 34 on the crank pin bearing side.
Since A precedes the communication starting point Q of ₂ ,
Hydraulic pressure acts on the lock pin 28 earlier than in the past, and the delay in the operation of the lock pin 28 is compensated accordingly.

In other words, even if there is an influence such as air bubbles in the oil in the high speed range of the engine, the hydraulic pressure will reliably act on the lock pin 28 from the communication start point Q to the end point R, and there will be virtually no delay in the operation of the lock pin. . Therefore, the eccentric bearing 26 is reliably locked and the compression ratio is smoothly switched to a high compression ratio side.

In addition, in this example, the communication relationship between each oil groove and oil hole for low compression ratio is configured in accordance with the communication relationship between each oil groove and oil hole for high compression ratio, so that the eccentric bearing 26 can also be performed smoothly.

[Effect of idea]

As explained above, when using the hydraulic passage of the variable compression ratio mechanism of the present invention, the communication start timing between the oil groove on the crank journal bearing side and the oil hole in the crankshaft is determined by the oil groove on the crank pin bearing side. Since the timing is set earlier than the timing at which communication with the oil hole starts, it is possible to compensate for the delay in lock pin operation caused by a delay in the transmission of hydraulic pressure, and the eccentric bearing is reliably locked even in the high rotation range of the engine. You can get the effect that you can.

Moreover, since the means for advancing the communication start time is simply extending the length of the oil groove in the direction opposite to the direction of rotation of the crankshaft, the purpose can be achieved without complicating the hydraulic passage.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the state of communication between the oil grooves of the crank pin bearing and the crank journal bearing in the hydraulic passage of a variable compression ratio mechanism according to an embodiment of the present invention, and FIG. Figure 3 is a perspective view of the oil passage near the crankshaft.
A relationship diagram showing the communication relationship between the oil hole in the crankshaft and each oil groove in the variable compression ratio mechanism shown in the figure, Figure 4 is an overall sectional view of the conventional variable compression ratio mechanism, and Figure 5
The figure is a sectional view taken along the - line in FIG. 4. 21... Piston, 23... Piston pin, 2
4...Connecting rod, 25...Crankshaft, 26...Eccentric bearing, 27...Lock pin engagement hole, 28...Lock pin, 32,3
3, 38, 39...Oil groove, 34...Oil hole, 35...
...Crank pin bearing part, 36...Crank journal bearing part, _A1 , _A2 ...Time of communication between oil groove and oil hole, P, Q...Communication start point.

Claims (1)

[Scope of utility model registration request] An eccentric bearing is rotatably interposed between the piston pin and the connecting rod, a lock pin engaging hole is provided in the eccentric bearing, and a lock pin that goes in and out of the lock pin engaging hole is provided on the connecting rod side. An oil groove formed on the periphery of the crank pin bearing of the connecting rod and an oil groove formed on the periphery of the crank journal bearing can be communicated through an oil hole formed in the crankshaft. In the hydraulic passage of the variable compression ratio mechanism, the lock pin is engaged with or disengaged from the lock pin engagement hole by applying hydraulic pressure to the lock pin through the oil hole and the oil groove to lock or unlock the rotation of the eccentric bearing. , the variable pressure welding is characterized in that the timing at which the oil groove on the crank journal bearing side starts communicating with the oil hole is made earlier than the timing at which communication starts between the oil groove on the crank pin bearing side and the oil hole. Hydraulic passage of ratio mechanism.