JP5120214B2 - Variable compression ratio mechanism of internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio mechanism for an internal combustion engine.

  As a variable compression ratio mechanism for an internal combustion engine, an upper connecting rod connected to a piston pin and a lower connecting rod connected to a crank pin of a crankshaft are connected, and a swing arm is connected to the lower connecting rod (patent) Reference 1), various connecting rods such as a connecting rod connected to a piston and a second connecting rod connected to a crankshaft, and a control rod connected to the first connecting rod (Patent Document 2). A device has been devised.

  Patent Documents 1 and 2 both change the compression ratio by moving the above swing arm, control rod, etc. with another actuator, changing the apparent connecting rod length, and changing the top dead center position of the piston. is there.

JP 2001-317383 A JP 2000-54873 A

  By the way, in a multi-cylinder internal combustion engine, the fuel control (fuel injection amount) of each cylinder is determined a certain time before the piston reaches the top dead center. There is a cylinder that is displaced, which may cause deterioration of exhaust gas. Therefore, it is desirable to change the compression ratio for each cylinder.

  Further, as in Patent Documents 1 and 2, the mechanism for changing the top dead center position of the piston by swinging the connecting rod using a swing arm, a control rod, or the like changes the piston speed relative to the crank angle as the compression ratio is changed. Therefore, vibrations and noises of different frequency components are induced, and the countermeasures are complicated.

  Accordingly, an object of the present invention is to provide a variable compression ratio mechanism of an internal combustion engine that can change the compression ratio for each cylinder.

To achieve the above object, an internal combustion engine variable compression ratio mechanism according to the present invention includes an inner piston connected to a crankshaft via a connecting rod, an outer piston slidably fitted on the inner piston, A pressure working chamber formed between the top back surface of the outer piston and the top surface of the inner piston; a working fluid supply / discharge passage provided in the connecting rod for supplying and discharging working fluid to the pressure working chamber; An opening / closing valve disposed in the working fluid supply / discharge passage and opening / closing the working fluid supply / discharge passage, and provided on the connecting rod, and opening / closing the opening / closing valve to supply / discharge the working fluid to / from the pressure working chamber. A control unit that changes the compression ratio of the internal combustion engine by changing the position of the outer piston with respect to the inner piston. When supplying the working fluid to the dynamic chamber, during the intake stroke to open the on-off valve to the displacement of the outer piston is equal to or greater than the target displacement, when discharging the working fluid from said pressure working chamber, said outer during the compression stroke The on-off valve is opened until the piston displacement matches the target displacement.

Here, the variable compression ratio mechanism is provided in the connecting rod and generates power by the vertical movement of the connecting rod, and the electric current provided in the connecting rod and generated by the power generating unit is used for the operation of the control unit. You may provide further the pressure accumulation part which accumulates in order to use .

  According to the present invention, there is an excellent effect that the compression ratio can be changed for each cylinder.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view of a variable compression ratio mechanism for an internal combustion engine according to an embodiment of the present invention. The piston pin and the crank pin extend substantially parallel to each other, but the portion below the two-dot chain line L in FIG. 1 shows a cross section orthogonal to the cross section of the portion above the two-dot chain line L.

  As shown in FIG. 1, in the variable compression ratio mechanism 10 according to the present embodiment, the piston 11 includes an inner piston 14 connected to a crankpin 13 of a crankshaft via a connecting rod (connecting rod) 12, and an inner piston 14. A bottomed cylindrical outer piston 15 that is slidably fitted to the outer piston 15, and a pressure working chamber (hydraulic working chamber) between the top back surface 15 a of the outer piston 15 and the top surface 14 a of the inner piston 14. 16 is partitioned. The connecting rod 12 is provided with a working fluid supply / discharge passage 17 for supplying and discharging the working fluid (engine oil in this embodiment) to the pressure working chamber 16.

  The inner piston 14 is connected to one end (small end) 12a of the connecting rod 12 via a piston pin 18, and the other end (big end) 12b of the connecting rod 12 is connected to a crankshaft via a connecting rod bearing (not shown). Are connected to the crank pin 13. A ring seal 19 for sealing a gap between the outer piston 15 and the inner piston 14 is attached to the inner piston 14.

  In this embodiment, in order to supply and discharge the working fluid, the crankpin 13 of the crankshaft is provided with a fluid passage (oil passage) 13a extending in the longitudinal direction of the crankpin 13 and a fluid passage 13a. And a fluid hole (oil hole) 13 b extending in the radial direction of the crankpin 13. Further, the piston pin 18 is provided with a fluid hole (oil hole) that extends in the radial direction of the piston pin 18 and is provided in the middle portion in the longitudinal direction so as to communicate with the fluid groove (oil groove) 12 d on the inner periphery of the small end 12 a of the connecting rod 12. ) 18a, a fluid passage (oil passage) 18b provided in communication with the fluid hole 18a and extending in the longitudinal direction of the piston pin 18, and a fluid passage 18b in communication with the fluid passage 18b. A fluid hole (oil hole) 18c extending in the radial direction is provided. The inner piston 14 is connected to a fluid hole 18c of the piston pin 18 and is provided on the inner periphery of the piston pin hole 14b and extends in the circumferential direction of the piston pin hole 14b. A fluid hole (oil hole) 14d that communicates the groove 14c and the top surface 14a is provided.

  A sensor part of a displacement sensor (capacitive displacement meter in the present embodiment) 20 for detecting the displacement (position) of the outer piston 15 relative to the inner piston 14 is attached to the top of the inner piston 14. The displacement sensor 20 is electrically connected to a control unit 22 described later via a lead wire 21.

  A power generation unit 23, a pressure accumulating unit 24, a control unit 22, an actuator (piezo solenoid in this embodiment) 25 and an on-off valve (check valve) 26 are built in the rod portion 12 c of the connecting rod 12. In the present embodiment, the rod portion 12c is divided in the vicinity of the big end 12b in order to incorporate the power generation portion 23, the pressure accumulating portion 24, the control portion 22, the piezo solenoid 25, and the on-off valve 26 in the rod portion 12c. These divided parts are joined by a sleeve nut 27.

  The opening / closing valve 26 is disposed in the working fluid supply / discharge passage 17 and opens / closes the working fluid supply / discharge passage 17. The control unit 22 drives the piezo solenoid 25 to open / close the opening / closing valve 26. Is controlled to open and close.

  FIG. 2 shows an outline of the power generation unit 23. The power generation unit 23 is capable of reciprocating in the outer cylinder 28, a coil 29 provided in the outer cylinder 28, a fluid passage (oil passage) 30 defined inward of the coil 29, and the fluid passage 30. And a provided magnet (permanent magnet) 31. In order to supply and discharge the working fluid, the magnet 31 is provided with a fluid hole (oil hole) 31 a communicating with the fluid passage 30. Due to the vertical movement of the connecting rod 12 accompanying the operation of the internal combustion engine, the magnet 31 moves up and down in the fluid passage 30 inside the coil 29 to generate electromotive force. The fluid passage 30 inside the coil 29 forms a part of the working fluid supply / discharge passage 17, and the working fluid in the fluid passage 30 attenuates the vertical movement of the magnet 31, thereby the magnet 31, the outer cylinder 28, etc. It becomes possible to prevent damage.

  FIG. 3 shows an outline of the control unit 22. The current generated by the power generation unit 23 is rectified and regulated in the pressure storage unit 24 and then stored in the capacitor. The current stored in the capacitor is used to operate the control unit 22 (driver) and drive the piezo solenoid 25 and the like. The displacement signal of the displacement sensor 20 attached to the top of the inner piston 14 is transmitted to the control unit 22 via the lead wire 21 and is transmitted to the ECM (engine control module) 32 by the control unit 22. The ECM 32 determines the target displacement of the outer piston 15 based on the displacement signal of the displacement sensor 20, and transmits a drive signal for the piezo solenoid 25 corresponding to the determined target displacement to the control unit 22. The control unit 22 receives the drive signal from the ECM 32, operates the driver according to the drive signal, drives the piezo solenoid 25, and opens and closes the on-off valve 26.

  When the piezo solenoid 25 is driven to open the on-off valve 26, the working fluid is supplied to the crankshaft crank pin 13 (fluid passage 13a, fluid hole 13b), on-off valve 26 in the connecting rod 12 (working fluid supply / discharge passage 17), The pressure is applied to the pressure working chamber 16 through the piston pin 18 (fluid hole 18a, fluid passage 18b, fluid hole 18c) and the inner piston 14 (fluid groove 14c, fluid hole 14d). The outer piston 15 is pushed up by the working fluid supplied to the pressure working chamber 16. When the displacement of the outer piston 15 reaches a predetermined displacement, if the piezo solenoid 25 is driven to close the on-off valve 26, the working fluid in the pressure working chamber 16 is retained, and the required compression ratio can be obtained. It becomes possible.

  That is, in the present embodiment, the working fluid in the pressure working chamber 16 between the outer piston 15 and the inner piston 14 is opened and closed by opening and closing the on-off valve 26 provided in the connecting rod 12 (working fluid supply / discharge passage 17). By adjusting the amount (oil amount), the top height of the piston 11 (outer piston 15) is changed to change the compression ratio.

  In order to change the compression ratio stably in a short time, in the present embodiment, the control unit 22 opens the on-off valve 26 during the intake stroke in which the negative pressure acts on the pressure working chamber 16, so that the working fluid is supplied early. It flows into the pressure working chamber 16. At this time, since a lift loss occurs during compression due to leakage of working fluid from the gap between the inner piston 14 and the outer piston 15, air mixing, etc., the control unit 22 determines that the displacement of the outer piston 15 is the target in the intake stroke. The working fluid is caused to flow into the pressure working chamber 16 so that the displacement is equal to or greater than the displacement, and during the next compression stroke in which positive pressure acts on the pressure working chamber 16, the opening / closing valve 26 is opened and closed for a short time. By feeding back the working fluid from the pressure working chamber 16, the displacement of the outer piston 15 is matched with the target displacement.

  That is, since it is difficult to make the displacement of the outer piston 15 coincide with the target displacement only by opening / closing (supplying of working fluid) of the on-off valve 26 during the intake stroke due to lift loss at the time of compression, in the present embodiment, during the intake stroke Open the on-off valve 26 and allow a larger amount of working fluid to flow into the pressure working chamber 16 so that the displacement of the outer piston 15 becomes equal to or greater than the target displacement, and open the on-off valve 26 during the next compression stroke to allow more inflow. By causing a part of the working fluid to flow out from the pressure working chamber 16, the displacement of the outer piston 15 is made to coincide with the target displacement.

  Here, changing the compression ratio for each cylinder in accordance with the load of the internal combustion engine is very effective in improving the fuel efficiency in the medium / low speed range.

  In gasoline engines, in order to prevent abnormal combustion (detonation) in the high load region of the gasoline engine, the compression ratio is lowered only in the high load region, and the compression ratio in the medium / low load region is kept high. This makes it possible to improve fuel efficiency in the middle / low speed range.

  In a diesel engine, an increase in the amount of EGR gas is expected due to recent exhaust gas countermeasures. In the high load region where the fuel injection amount is large, the in-cylinder pressure increases remarkably, so it is effective to lower the compression ratio in order to reduce NOx. Further, in order to avoid an increase in engine strength accompanying an increase in in-cylinder pressure, it is also necessary to lower the compression ratio in a high load region.

  In this embodiment, the inner piston 14 connected to the crankshaft via the connecting rod 12, the outer piston 15 slidably fitted to the inner piston 14, the top back surface 15a of the outer piston 15 and the top of the inner piston 14 A pressure working chamber 16 formed between the surface 14a, a connecting rod 12 and a working fluid supply / discharge passage 17 for supplying and discharging working fluid to and from the pressure working chamber 16 and a working fluid supply / discharge passage 17 are arranged. And an opening / closing valve 26 that opens and closes the working fluid supply / discharge passage 17 and a control unit 22 that controls opening / closing of the opening / closing valve 26. The displacement (position) of the outer piston 15 relative to the inner piston 14 can be changed by changing the compression ratio for each cylinder. It is possible.

  That is, in the known variable compression ratio mechanism, since the compression ratio is changed at the same time for all the cylinders, there is a cylinder in which optimum fuel control is shifted, which may cause deterioration of exhaust gas. In the ratio mechanism 10, since the compression ratio is changed for each cylinder during the intake stroke and during the compression stroke, there is no problem in fuel control, no deterioration of exhaust gas is caused, and fuel consumption can be improved.

  Further, in the present embodiment, the piston speed with respect to the crank angle does not change with the compression ratio change, so that vibrations and noises of different frequency components are not induced.

  In the present embodiment, when supplying the working fluid into the pressure working chamber 16, the control unit 22 opens the on-off valve 26 during the intake stroke in which a negative pressure acts on the pressure working chamber 16, When the working fluid is discharged from the valve, the on-off valve 26 is opened during the compression stroke in which the positive pressure acts on the pressure working chamber 16, so that the pressure working chamber 16 is utilized using the pressure (negative pressure or positive pressure) in the pressure working chamber 16. It is possible to supply and discharge the working fluid with respect to 16, and to prevent the mechanism from becoming large and heavy.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

FIG. 1 is a side sectional view of a variable compression ratio mechanism for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating the power generation unit. FIG. 3 is a diagram illustrating an outline of the control unit.

Explanation of symbols

10 Variable compression ratio mechanism 11 Piston 12 Connecting rod (connecting rod)
14 inner piston 14a top surface 15 outer piston 15a top back 16 pressure working chamber 17 working fluid supply / discharge passage 22 control section 26 on-off valve

Claims (2)

An inner piston connected to the crankshaft via a connecting rod, an outer piston slidably fitted to the inner piston, and a pressure formed between the top back surface of the outer piston and the top surface of the inner piston A working chamber, a working fluid supply / discharge passage provided in the connecting rod for supplying / discharging working fluid to / from the pressure working chamber, and disposed in the working fluid supply / discharge passage for opening / closing the working fluid supply / discharge passage. An on-off valve and a connecting rod, provided on the connecting rod, open and close the on-off valve to supply and discharge the working fluid to and from the pressure working chamber, thereby changing the position of the outer piston relative to the inner piston, thereby reducing the compression ratio of the internal combustion engine. And a control unit that changes the outer piston during the intake stroke when supplying the working fluid into the pressure working chamber. Open the shutoff valve to the emission of the displacement is equal to or greater than the target displacement, when discharging the working fluid from said pressure working chamber opens the on-off valve during the compression stroke until the displacement of the outer piston coincides with the target displacement A variable compression ratio mechanism for an internal combustion engine.   A power generation unit that is provided in the connecting rod and generates power by the vertical movement of the connecting rod; and a pressure accumulating unit that is provided in the connecting rod and stores the current generated by the power generation unit for use in the operation of the control unit. The variable compression ratio mechanism for an internal combustion engine according to claim 1.

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