JPH0413393Y2 - - 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 particularly relates to a hydraulic control device for 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. 58-172431
Publication No.).

The compression ratio variable mechanism using an eccentric bearing has a lock pin engagement hole in the eccentric bearing, a lock pin storage hole in the connecting rod, the lock pin is stored in the lock pin storage hole, and the lock pin is moved by applying hydraulic pressure to the lock pin. The lock pin is driven to move forward and backward in the direction of the engagement hole to engage and disengage the lock pin with the lock pin engagement hole.

A hydraulic passage for locking the lock pin and a hydraulic passage for unlocking the lock pin are connected to the lock pin storage hole, and when the load is light, the hydraulic directional control valve is switched to one side and oil is pumped to the hydraulic passage for the lock pin lock. It's summery. As a result, the lock pin moves and rotation of the eccentric bearing is locked, creating a high compression ratio state. Also,
When the load is medium or high, the hydraulic directional control valve is switched to the other side, and oil is forced into the hydraulic passage for unlocking the lock pin. Therefore, the eccentric bearing is unlocked and a low compression ratio state is created.

[Problem that the invention attempts to solve]

In order to reliably lock or unlock the eccentric bearing, it is desirable to increase the pressure of the oil supplied to the lock pin. However, when the lock pin is securely locked or unlocked, high oil pressure is not required, and the higher the oil pressure is set, the greater the energy loss of the oil pump becomes. In other words, by temporarily increasing the lock pin drive oil pressure only when switching the compression ratio, the switching of the compression ratio can be ensured.
Moreover, it becomes possible to provide a hydraulic control device with less energy loss.

Focusing on the above points, the present invention temporarily increases the lock pin drive oil pressure only when switching the compression ratio to ensure the switching of the compression ratio, and to reduce the energy loss of the oil pump after switching the compression ratio. The object of the present invention is to provide a hydraulic control device for a variable compression ratio mechanism that can perform the following steps.

[Means for solving problems]

The hydraulic control device for 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 variable compression ratio of an internal combustion engine, wherein a lock pin provided on the connecting rod side is hydraulically driven by the operation of a hydraulic directional control valve to lock or unlock the rotation of the eccentric bearing and switch the compression ratio. In the mechanism, a delay switching valve that operates later than the hydraulic directional switching valve and enables the hydraulic passage to communicate with a second relief valve is interposed in the hydraulic passage that pressure-feeds oil from the hydraulic directional switching valve to the lock pin. , a first relief valve whose relief pressure is set higher than that of the second relief valve is provided in a hydraulic passage that pressure-feeds oil to the hydraulic directional switching valve.

[Effect]

In the hydraulic control device for the variable compression ratio mechanism configured in this way, the driving hydraulic pressure of the lock pin is the first one.
It is switched to two stages by the relief valve and the second relief valve. In other words, when switching the compression ratio, the lock pin drive oil pressure is controlled by the first relief valve, which has a high relief pressure, and then the delay switching valve operates and the lock pin drive oil pressure is set to a low relief pressure. Controlled by a second relief valve. Therefore, when switching the compression ratio, the lock pin is driven by high hydraulic pressure, and the switching of the compression ratio is reliably performed.

Further, the lock pin drive oil pressure is temporarily increased and then lowered by switching the delay switching valve, so that the load on the oil pump is reduced, and energy loss in the oil pump is suppressed to a small level.

〔Example〕

Hereinafter, preferred embodiments of the hydraulic control device for a variable compression ratio mechanism of the present invention will be described with reference to the drawings.

First Embodiment FIGS. 1 to 6 show a first embodiment of the present invention. First, in FIGS. 3 and 4, a piston 2 is slidably fitted into a cylinder 1 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.

The wall thickness changes in the circumferential direction 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, and the inner circumferential circle and the outer circumferential circle are eccentric with respect to each other. A bearing 6 is rotatably interposed.

A lock pin housing 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 6. 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 be inserted and retracted 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 engagement by the lock pin 8 is released, the eccentric bearing 6 rotates freely and the compression top dead center is reached. The piston is in a low position, allowing a low compression ratio state to occur. 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 10 and a lock pin unlocking hydraulic passage 11 are connected to the lock pin storage hole 7 with the lock pin 8 in between, and the lock pin locking hydraulic passage 10 opens at a position that urges the lock pin 8 in the direction of the eccentric bearing 6. has been done. Furthermore, a lock pin guide groove 12 is formed on the outer periphery of the eccentric bearing 6 at a position corresponding to the lock pin 8, and extends all the way in the circumferential direction.
This groove 12 is provided with the lock pin engaging hole 9.

The hydraulic passages 10 and 11 provided in the connecting rod 3 communicate with oil grooves 14 and 15 provided independently on the circumference of the crank pin bearing portion of the connecting rod, respectively. There is.
The oil grooves 14 and 15 are connected to oil grooves 18 and 19 that are provided independently from each other on the circumference of the crank journal bearing portion through an oil hole 17 in the crankshaft 16.
The two are connected to each other so that they can communicate intermittently when the crankshaft 16 rotates.

A hydraulic passage 21 for high compression ratio control and a hydraulic passage 20 for low compression ratio control are provided in the cylinder block. The high compression ratio control hydraulic passage 21 communicates with the oil groove 18 , and the low compression ratio control hydraulic passage 20 communicates with the oil groove 19 .

FIG. 1 shows the hydraulic passages that supply oil to the lock pin. In FIG. 1, 30 indicates an oil pan, and oil 31 is stored in the oil pan. Oil 31 is pumped up by an oil pump 32, and is passed through an oil filter 33 to a hydraulic passage 34 leading to the crank journal bearing part where no oil passage for variable compression ratio is formed, a hydraulic passage 35 leading to the oil jet part, and a valve train. The oil is supplied to a lubricating passage 36 and a variable compression ratio hydraulic passage 37, respectively. oil filter 33
A first relief valve 38 is provided upstream of and in parallel with each of the above-mentioned hydraulic passages, and the pressure of oil supplied to each of the above-mentioned hydraulic passages is regulated by this first relief valve 38. ing. The relief pressure of the first relief valve 38 is set to, for example, 15 kg/cm ² and is higher than the relief pressure of the second relief valve, which will be described later.

A hydraulic directional switching valve 39 is provided downstream of the variable compression ratio hydraulic passage 37 . The hydraulic directional switching valve 39 is connected to hydraulic passages 40 and 41 for pumping oil to the lock pin 8, and a drain passage 48, respectively. A delay switching valve 42 that operates later than the hydraulic directional switching valve 39 is provided downstream of the hydraulic passages 40 and 41.

The delay switching valve 42 is composed of a cylinder 44 and a switching piston 43 that is slidably fitted into the cylinder 44 and moves within the cylinder by the pressure of oil supplied to the lock pin 8. A chamber surrounded by the cylinder 44 is divided into a first oil chamber 45 and a second oil chamber 46 by a switching piston 43 . The above-mentioned hydraulic passage 40 is connected to the first oil chamber 4
5 to a low compression ratio control hydraulic passage 20, and this low compression ratio control hydraulic passage 20 communicates with an oil groove 18 formed on the circumference of the crank journal bearing. Further, the hydraulic passage 41 is
It communicates with a high compression ratio control hydraulic passage 21 via a second oil chamber 46, and this high compression ratio control hydraulic passage 21 communicates with an oil groove 19 formed on the circumference of the crank journal bearing. ing.

A drain passage 49 is connected to the delay switching valve 42, and a second relief valve 47 whose relief pressure is set lower than that of the first relief valve 38 is provided in the drain passage 49. The relief pressure of the second relief valve 47 is lower than that of the first relief valve 38, for example, 5.
It is set at around Kg/ ^cm2 . The second relief valve 47 is configured such that the switching piston 43 moves from the first oil chamber 45 to the second oil chamber 46 side by the pressure of the oil that is force-fed from the hydraulic direction switching valve 39 through the hydraulic passage 40. When this movement is completed, the first oil chamber 4
It is now connected to 5. That is, in this state, the pressure of the oil that is pumped from the hydraulic directional control valve 39 through the hydraulic passage 40 and the first oil chamber 45 to the lock pin 8 side is controlled by the second relief valve 47.

Further, the second relief valve 47 is configured such that the switching piston 43 is moved from the second oil chamber 46 to the first oil chamber 45 side by the pressure of oil pumped from the hydraulic direction switching valve 39 through the hydraulic passage 41. It moves, and when this movement is completed, it is communicated with the second oil chamber 46. That is, in this state, the pressure of the oil that is pumped from the hydraulic directional control valve 39 through the hydraulic passage 41 to the lock pin 8 side via the second oil chamber is as follows.
It is controlled by a second relief valve 47.

As a result, the pressure of the oil supplied to the low compression ratio control hydraulic passage 20 or the high compression ratio control hydraulic passage 21 is maintained at the first relief valve 38, which has a high relief pressure, until the switching piston 43 completes movement. When the movement of the switching piston 43 is completed, the second relief valve 47 whose relief pressure is set lower than that of the first relief valve 38 is used.

The travel time of the switching piston 43 can be determined by changing the shape, weight, moving distance, etc. of the switching piston, or by providing an orifice 48 in the first oil chamber 45 to adjust the oil flow rate as shown in FIG. This makes it variable.

Next, the operation in the first embodiment will be explained.

Not shown when the engine is under light load
An actuation signal _E1 shown in FIG. 6 is output from the ECU (electronic control unit) to the hydraulic directional switching valve 39, and the hydraulic directional switching valve 39 is switched to one side as shown in FIG. 5A. As a result, the oil pumped up from the oil pump 32 is sent to the hydraulic direction switching valve 39, the delay switching valve 42, and the high compression ratio control hydraulic passage 21. Hydraulic passage 10 for lock pin lock via shaft oil hole 17 and oil groove 14
is sent intermittently. Therefore, lock pin 8
is engaged with the eccentric bearing 6, and a high compression ratio state is created.

In this case, immediately after the hydraulic directional switching valve 39 is switched, the switching piston 43 of the delay switching valve 42 is moved to the first oil chamber 45 side as shown in FIG. and stops at position C in Figure 1. Therefore,
The pressure of the oil force-fed to the high compression ratio control hydraulic passage 21 is determined by the time from immediately after the hydraulic directional switching valve 39 is switched until the switching piston 43 completes movement.
Inside T ₁ , the relief pressure is controlled by the first relief valve 38 set high, and the piston 43
After the movement of the second relief valve 4 is completed, the second relief valve 4
7.

When the engine is under high load, the hydraulic directional valve 3
9 is switched to the state shown in FIG. 1, and oil is sent to the hydraulic passage 41, the delay switching valve 42, and the low compression ratio control hydraulic passage 20. Further, the oil flows through the oil groove 19, the oil hole 17 of the crankshaft, and the oil groove 15.
It is intermittently sent to the lock pin unlocking hydraulic passage 11 via the lock pin unlocking hydraulic passage 11. Accordingly, the lock pin 8 is driven and disengaged from the eccentric bearing 6, resulting in a low compression ratio state.

In this case, as the oil is forced into the low compression ratio control hydraulic passage 20, the switching piston 43 of the delay switching valve 42 moves toward the second oil chamber 46, and when the movement of the switching piston 43 is completed, As shown in FIG. 1, the first oil chamber 45 and the second relief valve 47 are communicated with each other. Therefore, the pressure of the oil force-fed to the low compression ratio control hydraulic passage 20 is maintained at the first relief valve 38, which is set at a high relief pressure, until just before the switching piston 43 completes movement.
The switching piston 43 is controlled by the second relief valve 47 after the switching piston 43 completes its movement.

In this way, when switching the compression ratio, the lock pin 8
Since the pressure of the oil applied to the lock pin 8 is increased, the biasing force of the lock pin 8 is increased, and the compression ratio can be changed reliably. Further, since the pressure applied to the lock pin 8 is automatically lowered after being temporarily increased, the load on the oil pump 32 is reduced, and energy loss is reduced.

Second Embodiment FIGS. 7 and 8 show a second embodiment of the present invention. The second embodiment differs from the first embodiment only in the configuration of the delay switching valve, and other parts are similar to the first embodiment.
By assigning the same reference numerals as those in the embodiment, description of the corresponding parts will be omitted, and only different parts will be described.

In FIG. 7, reference numeral 50 indicates a delay switching valve that operates later than the hydraulic directional switching valve 39. In the first embodiment, the delay switching valve had a structure that was operated mechanically by hydraulic pressure, whereas the delay switching valve 50 of this embodiment was operated by an electric signal from an ECU (not shown). It's getting old. In other words, the hydraulic directional switching valve 39 is activated by an electric signal output after a predetermined period of time has elapsed since the hydraulic directional switching valve 39 was switched. This delay switching valve 50 includes a valve body 51.
A first oil chamber 52 and a second oil chamber 53 are formed.

In the second embodiment configured in this way,
When the engine is under high load, the delay switching valve 5
0 is switched to one side as shown in Figure 7A,
The low compression ratio control hydraulic passage 20 communicates with the hydraulic passage 40 via a first oil chamber 52 . In this state, the first oil chamber 52 and the second relief valve 47
The low compression ratio control hydraulic passage 20
The pressure of the oil pumped to is controlled by the second relief valve 47, which has a low relief pressure, and the load on the oil pump 32 is also small.

If the engine is under low load, first check the ECU.
An actuation signal _E2 is output from the hydraulic directional switching valve 39 to the hydraulic directional switching valve 39, and the hydraulic directional switching valve 39 is switched to the other direction as shown in FIG. In this state, the delay switching valve 50 is not yet switched, and the pressure of the oil forced into the high compression ratio control hydraulic passage 21 is controlled by the first relief valve 38 whose relief pressure is set high. Maintains high oil pressure.

The hydraulic directional control valve 39 is switched for a predetermined time.
When _T2 has elapsed, the ECU outputs an actuation signal _E3 to the delay switching valve 50, and the valve body 5 of the delay switching valve 50
1 is switched to the position shown in FIG. 7C. Therefore, the oil pressure-fed from the hydraulic directional switching valve 39 is forced-fed to the high compression ratio control hydraulic passage 21 via the second oil chamber 53 of the delay switching valve 50. In this case, the second oil chamber 53 and the second relief valve 47 are communicated with each other, so that the pressure of the oil fed to the high compression ratio control hydraulic passage 21 is controlled by the second relief valve 47.
7. In other words, when the hydraulic directional control valve 39 operates and it is determined that the eccentric bearing 6 is securely locked by the lock pin 8, the driving hydraulic pressure of the lock pin 8 is automatically switched from high pressure to low pressure, and the oil pump 32 is automatically switched from high pressure to low pressure. load becomes small.

[Effects of the invention] As explained above, when using the hydraulic control device of the variable compression ratio mechanism of the present invention, the hydraulic passage that pumps oil to the hydraulic directional valve or the lock pin operates later than the hydraulic directional valve. This hydraulic passage is connected to the second
A first relief valve whose relief pressure is set higher than that of the second relief valve is provided in a hydraulic passage that forcefully sends oil to the hydraulic directional control valve, with a delay switching valve that enables communication with the relief valve of the hydraulic directional control valve. Therefore, it is possible to temporarily increase the lock pin drive oil pressure when switching the compression ratio, and the switching of the compression ratio can be performed reliably.

In addition, after the lock pin drive oil pressure is temporarily increased, the lock pin drive oil pressure is controlled by the second relief valve with lower relief pressure, which reduces the load on the oil pump and reduces energy loss. It can be kept small.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a hydraulic control device for a variable compression ratio mechanism according to a first embodiment of the present invention, FIG. 2 is a sectional view showing an example of the delay switching valve in FIG. 1, and FIG. A sectional view of a variable compression ratio mechanism in which the device shown in the figure is incorporated, FIG. 4 is a sectional view taken along the - line of FIG. 3,
Figures 5A to 5C are system diagrams showing the operating order of the delay switching valves in the device shown in Figure 1, and Figure 6 is a system diagram showing the operating sequence of the delay switching valve in the device shown in Figure 1.
A relational diagram showing the relationship between the elapsed time at the time of compression ratio switching and the lock pin driving hydraulic pressure in the device shown in the figure. FIG. 8 is a system diagram showing the sequence of operations, and a relational diagram showing the relationship between the elapsed time at the time of switching the compression ratio and the lock pin drive oil pressure in the device of FIG. 7. 3... Connecting rod, 6... Eccentric bearing, 8... Lock pin, 10... Hydraulic passage for lock pin locking, 11... Hydraulic passage for lock pin unlocking, 14, 15, 18, 19... Oil groove, 32 ... Oil pump, 38 ... First relief valve, 39 ... Hydraulic directional control valve, 42, 50 ...
...Delay switching valve, 47...Second relief valve.

Claims (1)

[Claims for Utility Model Registration] (1) An eccentric bearing is rotatably interposed between a piston pin and a connecting rod, and a lock pin provided on the connecting rod side is operated by a hydraulic directional valve. In a variable compression ratio mechanism for an internal combustion engine that is hydraulically driven to lock or unlock the rotation of the eccentric bearing and switch the compression ratio, a hydraulic passage for pumping oil from the hydraulic directional control valve to the lock pin is provided. , a delay switching valve that operates later than the hydraulic directional switching valve and allows the hydraulic passage to communicate with the second relief valve is interposed therebetween, and the hydraulic passage that pressure-feeds oil to the hydraulic directional switching valve is connected to the second hydraulic directional switching valve. A hydraulic control device for a variable compression ratio mechanism, comprising a first relief valve whose relief pressure is set higher than that of the relief valve. (2) The hydraulic control device for a variable compression ratio mechanism according to claim 1, wherein the delay switching valve is configured to be operated by the pressure of oil supplied from the hydraulic directional switching valve side. . (3) The variable compression ratio mechanism according to claim 1, wherein the delay switching valve is configured to be operated by an electrical signal output later than the electrical signal of the hydraulic directional switching valve. Hydraulic control device.