JP2015021410A - Variable compression ratio mechanism engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary a compression ratio with a simple mechanism without complicating a variable compression ratio mechanism of an engine.SOLUTION: A variable compression ratio mechanism engine includes a piston 3 stored in a cylinder 5, a connecting rod 4 having one end connected to the piston 3, a crankshaft 10 to which the other end of the connecting rod 4 is connected, and a universal joint disposed in a connection portion of the connecting rod 4 and the piston 3 and a halfway portion between both ends of the connecting rod 4, and by moving a connection portion of the connecting rod 4 and the crankshaft 10 to an axis of the cylinder 5 along a rotation axis direction of the crankshaft 10, a piston top dead center height and a piston bottom dead center height of the piston 3 are varied, and a compression ratio can be varied. By moving the connection portion of the crankshaft 10 and the connecting rod 4, the piston top dead center height and the piston bottom dead center height of the piston 3 can be varied, and thus, the compression ratio can be varied with a simple mechanism without complicating the device.

Description

  The present invention relates to a variable compression ratio mechanism engine capable of changing a compression ratio.

  It is known that the compression ratio of the engine affects the output and fuel consumption. For example, in a gasoline engine, in general, by setting a high compression ratio, it is possible to extract larger kinetic energy from the same amount of air-fuel mixture and expect to obtain high output and high torque. In addition, if the combustion efficiency increases by setting the compression ratio high, an improvement in fuel consumption can be expected. Similarly, in diesel engines, high output, high torque, and improved fuel efficiency can be expected by setting a high compression ratio.

  However, in a gasoline engine, if the compression ratio is set excessively, knocking or the like may occur. Even in a diesel engine, if the compression ratio is set excessively, the friction increases accordingly. For this reason, the internal combustion engine is set to an appropriate compression ratio in accordance with its use and specifications.

By the way, a variable compression ratio mechanism engine has been proposed in the past so that the compression ratio can be changed in accordance with the operating conditions and the like.
According to this variable compression ratio mechanism engine, for example, in a gasoline engine, when the engine is heavily loaded, the compression ratio can be lowered to prevent knocking. Further, when the load is low, the compression ratio can be increased to improve fuel efficiency. On the other hand, in a diesel engine, it is possible to reduce the friction by reducing the compression ratio in the high speed region of the engine, and improve the fuel efficiency by increasing the compression ratio in the low speed region.

  An example of a variable compression ratio mechanism engine is disclosed in Patent Document 1. In this variable compression ratio mechanism engine, the position of a piston and a connecting rod (connecting rod) can be adjusted by an eccentric sleeve provided between a small end portion of the connecting rod and a piston pin.

  The eccentric sleeve is provided with a pinion that rotates integrally with the eccentric sleeve. Further, the piston is provided with a rack that meshes with the pinion, and a rack drive and fixing mechanism that moves the rack forward and backward by hydraulic operation to fix the rack in a predetermined position. When the eccentric sleeve rotates due to the forward / backward movement of the rack, the relative position between the connecting rod and the piston in the stroke direction of the piston changes according to the eccentric position of the eccentric sleeve. Thereby, since the effective length of the connecting rod changes, the compression ratio in the combustion chamber can be appropriately changed.

JP-A-6-212993

  In the variable compression ratio mechanism engine described in Patent Document 1, a complicated device such as an eccentric sleeve, a rack, and a pinion is required to make the relative position between the piston and the connecting rod variable. It is desirable that the device be as simple as possible because of problems such as durability of components, maintenance, and cost. In addition, loss of work due to frictional resistance between the small end of the connecting rod and the eccentric sleeve, or the eccentric sleeve is dragged by the rotational movement of the small end of the connecting rod, making it difficult for the rack to smoothly advance and retract. There are also challenges.

  Accordingly, an object of the present invention is to make it possible to change the compression ratio of the engine with a simple mechanism without complicating the apparatus.

  In order to solve the above problems, a variable compression ratio mechanism engine according to the present invention includes a piston accommodated in a cylinder, a connecting rod having one end connected to the piston, and the other end of the connecting rod connected to each other. A connecting shaft between the connecting rod and the piston, or at least two universal joints provided in the middle part between both ends of the connecting rod, and the connecting rod and the crankshaft. The top dead center height and the bottom dead center height in the cylinder of the piston are changed by moving the connecting portion along the rotational axis direction of the crankshaft with respect to the axial center of the cylinder. A configuration in which the compression ratio is variable was adopted.

  Even if the connecting part between the connecting rod and the crankshaft moves along the rotation axis direction of the crankshaft with respect to the axis of the cylinder, the reciprocating motion of the piston is continued by the intervention of the two universal joints. The action of converting into the rotational motion of the shaft can be continued. Moreover, the top dead center height and the bottom dead center height in the cylinder of the piston are changed by moving the connecting portion between the crankshaft and the connecting rod along the rotation axis direction of the crankshaft, and the compression ratio is changed. It can be increased or decreased. Therefore, the compression ratio can be made variable with a simple mechanism without complicating the apparatus.

  The connecting rod includes a connection arm portion rotatably attached to a crankpin of the crankshaft around the axis of the crankpin, and a main body portion connecting the connection arm portion and the piston. The first universal joint portion provided between the main body portion and the piston, and the second universal joint portion provided between the main body portion and the connection arm portion may be provided.

  As a means for moving the connecting portion between the connecting rod and the crankshaft along the rotation axis direction of the crankshaft with respect to the axial center of the cylinder, for example, a hydraulic pressure or other gas pressure or a gas such as air Can be used.

For example, a pusher provided at one end of the crankshaft in the axial direction and pressing the crankshaft toward the other end in the axial direction, and provided at the other end in the axial direction of the crankshaft, the crankshaft toward the one end in the axial direction. Repulsive force applying means for pressing, and the crankshaft is pressed by the presser to move toward the other end in the axial direction and pressed against the repulsive force applying means in a state where the pressing force by the presser is released. It can be moved to one end side in the axial direction.
The crankshaft is pressed by the pressing element operated by hydraulic pressure or atmospheric pressure and moves to the other direction of the rotation axis, and is pressed by the repulsive force applying means in a state where the pressing force by the pressing element is released. Move to one direction of the rotation axis. As the repulsive force applying means, a repulsive force of an elastic body such as a spring, a hydraulic pressure such as a hydraulic pressure, or a gas pressure such as air can be used as in the case of a presser.

  At this time, the crankshaft is pressed by the pressing element and moves to the other end side in the axial direction to shift to a low compression ratio state, and is pressed by the repulsive force applying means to move to one end side in the axial direction to move to the high side. It is desirable to shift to a compression ratio state.

  According to the present invention, the compression ratio can be changed by moving the connecting portion between the crankshaft and the connecting rod along the direction of the rotation axis of the crankshaft. Therefore, the variable compression can be performed with a simple mechanism without complicating the device. A ratio mechanism engine can be realized.

FIG. 2 is a side view showing an embodiment of the present invention, where (a) is a high compression ratio state and (b) is a low compression ratio state. The example of a crankshaft moving means is shown, (a) is a side view, (b) is the principal part enlarged view of (a). It is a side view which shows the other example of a crankshaft moving means. It is a flowchart which shows the control process at the time of changing a compression ratio. (A) (b) is a side view which shows the modification of a crankshaft.

  Embodiments of the present invention will be described with reference to the drawings. Here, the configuration of a variable compression ratio mechanism engine 1 (hereinafter simply referred to as “engine 1”) capable of changing the compression ratio will be described in order by taking a four-cycle gasoline engine for automobiles as an example. It should be noted that in the drawings, the respective members of the engine 1 are partially omitted and simplified for easy understanding.

  In the engine 1, a piston 3 housed in a cylinder 5, a connecting rod 4 having one end connected to the piston 3 (hereinafter referred to as “connecting rod 4”), and the other end of the connecting rod 4 are connected. And a crankshaft 10. The piston 3 can reciprocate along the axial direction of the cylinder 5 as shown in FIG.

  The piston 3 has a circular shape in plan view, and includes a piston head 6 facing the combustion chamber 2 side and a piston boss portion 7 facing the crankshaft 10 side.

  The crankshaft 10 is connected to a crank web 13 serving as a counterweight at both ends of a crankpin 11 to which the connecting rod 4 is connected. Further, the crank webs 13 of adjacent cylinders are connected by a crank journal 12. The axial center of the crank journal 12 coincides with the rotational axis center of the crankshaft 10, and the axial center of the crankpin 11 is at a position eccentric from the rotational axis center of the crankshaft 10.

  The piston 3 receives the pressure of the combustion chamber 2 by the piston head 6, thereby moving in the cylinder 5 along the stroke direction to the crankshaft 10 side, and then reciprocating back to the cylinder head side. This reciprocating motion is transmitted to the crankshaft 10 via the connecting rod 4, whereby the crankshaft 10 rotates around the rotation axis.

  The connecting rod 4 is attached to the crankpin 11 of the crankshaft 10 and is connected to a connecting arm portion 4c that is rotatable around the axis of the crankpin 11, and a main body portion 4b that connects the connecting arm portion 4c and the piston boss portion 7 of the piston 10. Is provided.

  Here, one end of the connecting rod 4, that is, one end of the main body 4 b is connected to the piston boss 7 via the first universal joint 31. The first universal joint portion 31 has an inner member 31b made of a spherical protrusion provided on the connecting rod 4 side, and a recess into which the inner member 31b is fitted, and the inner surface of the recess has a spherical surface and a surface of the inner member 31b. It is a ball joint provided with the outer member 31a which is a spherical surface which can be contacted.

  Since the spherical surface of the inner member 31b of the first universal joint portion 31 is in sliding contact with the spherical surface of the outer member 31a, the connecting rod 4 is 360 degrees around its axis with respect to the axis of the piston 3, that is, the axis of the cylinder 5. It can be bent with respect to any orientation. In addition, the bending angle with respect to the axis of the cylinder 5 in each azimuth is allowed up to an angle as long as the spherical surfaces are in a range in which the spherical surfaces can slide. That is, the bending of the first universal joint portion 31 is allowed until the direction of the main body portion 4 b of the connecting rod 4 reaches a predetermined angle with respect to the axis of the cylinder 5.

  The other end portion of the connecting rod 4, that is, the other end portion of the main body portion 4 b is connected to a connection arm portion 4 c attached to the crankshaft 10 via a second universal joint portion 32. The second universal joint portion 32 has an inner member 32b formed of a spherical protruding portion provided on the main body portion 4b side of the connecting rod 4, and a concave portion provided on the connection arm portion 4c side in which the inner member 32b is fitted. The inner surface of the recess is a ball joint including an outer member 32a that is a spherical surface that can come into surface contact with the spherical surface of the inner member 32b.

  The spherical surface of the inner member 32 b of the second universal joint portion 32 is in sliding contact with the spherical surface of the outer member 32 a, so that the connecting rod 4 is connected to the crankshaft 10. With respect to the axis center (hereinafter referred to as “virtual axis center”) that rises perpendicularly to the cylinder head side through the center of the second universal joint portion 32 with respect to the eleven axis center 360 around the virtual axis 360 It can be bent with respect to any orientation. Further, the bending angle with respect to the virtual axis in each azimuth is allowed as long as the spherical surfaces are in a range in which the spherical surfaces can slide. That is, the bending of the second universal joint portion 32 is allowed until the direction of the main body portion 4b of the connecting rod 4 becomes a predetermined angle set in advance with respect to the virtual axis.

  The crankshaft 10 includes a crank boss portion 15 at one axial end shown on the left side in FIG. The crank boss portion 15 is a cylindrical member provided so as to protrude outward in the axial direction from the crank web 13 arranged on the most end side.

  Further, an end support shaft 19 that is rotatably supported around a crankcase (not shown) is disposed further outward in the axial direction of the crank boss portion 15. The one end support shaft 19 is a rotation shaft of the crankshaft 10 and is fitted inside the cylindrical member of the crank boss portion 15. At this time, the outer surface of the one end support shaft 19 and the inner surface 15a of the cylindrical member of the crank boss portion 15 are serration-coupled, and the one end support shaft 19 and the rotation shaft of the crankshaft 10 rotate integrally around the axis. Further, relative movement in the axial direction between the one end support shaft 19 and the crank boss portion 15 is allowed.

  The crankshaft 10 is provided with an axial connection portion 14 that protrudes coaxially with the rotation axis of the crankshaft 10 at the other axial end shown on the right side in FIG. The connecting portion 14 is provided so as to protrude outward in the axial direction from the crank web 13 disposed on the other end side.

  Further, the other end support portion 16 that is rotatably supported around the axis with respect to the crankcase is disposed further outward in the axial direction of the connection portion 14. The other end support portion 16 includes an end boss portion 17 that protrudes inward in the axial direction and toward the connection portion 14 side of the crankshaft 10. The end boss portion 17 is made of a cylindrical member, and the connection portion 14 is fitted inside the cylindrical member of the end boss portion 17. At this time, the outer surface of the connecting portion 14 and the inner surface 17a of the cylindrical member of the end boss portion 17 are serrated and connected, and the other end support portion 16 and the rotation shaft of the crankshaft 10 rotate together around the axis. In addition, relative movement of the other end support portion 16 and the connection portion 14 in the axial direction is allowed.

  As described above, since both ends of the crankshaft 10 are serration-coupled, members on both sides in the axial direction are allowed to move relative to each other in the axial direction across the selection coupling portion. Here, the one end support shaft 19 and the other end support portion 16 can be rotated around the axis with respect to the crankcase and are held so as not to move in the axial direction. Can be moved in the axial direction. That is, if the crankshaft 10 moves along the rotation axis direction of the crankshaft 10, the second universal joint portion 32 that is a connecting portion between the crankshaft 10 and the connecting rod 4 also has the same distance along the rotation axis direction. Just move.

  Further, a presser 20 is provided at one axial end of the crankshaft 10 to press the crankshaft 10 toward the other axial end of the rotating shaft. The presser 20 is supplied to an oil passage 21 communicated from a hydraulic supply source (not shown) to be pushed out to the other end side in the axial direction through the piston 22, and its tip is located at the most end side of the crankshaft 10. The crank web 13 to be pressed is pressed toward the other end in the axial direction.

  The other axial end of the crankshaft is provided with a repulsive force applying means 18 for pressing the crankshaft toward one end in the rotational axis direction. In this embodiment, a coil spring is employed as the repulsive force applying means 18. The coil spring is accommodated in the cylindrical member 17 and presses the end surface of the connecting portion 14 toward one end in the axial direction.

  The control of the variable compression ratio mechanism engine will be described below with reference to the flowchart of FIG. As a method for controlling the compression ratio, for example, the compression ratio can be used while being fixed to a constant high compression ratio state or can be used while being fixed to a constant low compression ratio state. Further, the compression ratio to be set can be increased or decreased stepwise or steplessly between the upper limit and the lower limit. Furthermore, when some trouble that does not cause the engine to stop occurs during operation in the high compression ratio state, the operation can be continued with the compression ratio lowered.

  As shown in FIG. 4, it is assumed that the hydraulic circuit that controls the presser 20 is operated in a state where the hydraulic pressure is released (hydraulic OFF state). At this time, the pressing element 20 does not press the crankshaft 10, and the crankshaft 10 is in the position shown in FIG. The second universal joint portion 32, which is a connecting portion between the connecting rod 4 and the crankshaft 10, is directly under the axis of the piston 3 and is set to a high compression ratio state with the highest compression ratio.

  In this embodiment, this high compression ratio state is set in the normal operation state. In particular, since the hydraulic pressure is not applied when the engine 1 is started, it is desirable that the state where the pressing by the presser 20 is not performed is a high compression ratio state so that the engine 1 can be started more smoothly. After the engine is started, the operation in the high compression ratio state is continued unless a factor for reducing the compression ratio occurs.

  Suppose that it is necessary to change the setting to a low compression ratio when there is a change in operating conditions or when some trouble occurs.

  Here, a predetermined hydraulic pressure is supplied to the oil passage 21 of the hydraulic circuit, and the presser 20 is pressed to the other end side in the axial direction through the piston 22. Thereby, the crankshaft 10 moves to the other end side in the axial direction from the state shown in FIG. 1A to the state shown in FIG. At the same time, the connecting portion between the connecting rod 4 and the crankshaft 10 and the second universal joint portion 32 also move to the other end side in the axial direction. Since the connecting portion between the connecting rod 4 and the crankshaft 10 moves away from the axial center of the cylinder 5 along the rotational axis direction of the crankshaft 10, the top dead center height and the bottom dead center height in the cylinder 5 of the piston 3 are Lower. That is, the top dead center position and the bottom dead center position are moved away from the piston head, whereby the low compression ratio state is set.

  When returning from the low compression ratio state to the high compression ratio state, the pressing force by the pressing element is released by releasing the hydraulic pressure of the hydraulic circuit. The crankshaft 10 is pressed by the repulsive force of the repulsive force applying means 18 and moves in one direction of the rotation axis, and is set to a high compression ratio state.

  If such a variable compression ratio mechanism engine 1 is used, it is possible to control the compression ratio in accordance with the rotational speed of the engine 1. In general, since the low engine speed range is likely to cause knocking, for example, in the low engine speed range, the compression ratio is automatically set based on a command from an electronic control unit (Electronic Control Unit) included in the automobile. In order to improve fuel consumption in the high engine speed range, the compression ratio is automatically increased to a predetermined high compression ratio based on a command from the electronic control unit. A control method for setting the compression ratio state can be adopted.

  Further, it is possible to control the compression ratio in accordance with the load on the engine 1. For example, the engine 1 of the automobile may be driven down from a high load state where the accelerator pedal is greatly depressed on an uphill, or downhill on an inertia, or the engine is completely stopped and the engine is idling. Used in various situations up to low load conditions. For this reason, for example, a control method that automatically reduces the compression ratio to prevent knocking when the engine 1 is in a high load state and automatically increases the compression ratio to improve fuel consumption in a low load state. Can be adopted.

  Here, the information on the engine speed can be obtained by an electronic control unit based on information from a crank angle sensor or the like. Further, information on the load on the engine can be calculated in the electronic control unit based on information such as the opening degree of the throttle valve linked to the accelerator pedal, the fuel injection amount, the engine speed, and the vehicle speed.

As described above, the first universal joint 31 and the second universal joint 32 are interposed between the piston 3 and the crankshaft 10, so that even if the crankshaft 10 moves along the rotation axis direction, Subsequently, the action of converting the rotational movement of the crankshaft 10 into the reciprocating movement of the piston 3 can be continued.
Further, the top dead center height and the bottom dead center height in the cylinder 5 of the piston 3 are changed by moving the connecting portion between the crankshaft 10 and the connecting rod 4 along the rotation axis direction of the crankshaft 10. The compression ratio can be increased or decreased.

In the said embodiment, the 1st universal joint part 31 is provided with the inner member 31b which consists of a spherical protrusion provided in the main-body part 4b side of the connecting rod 4, and the recessed part which is provided in the piston 3 side and the inner member 31b fits. The inner surface of the concave portion is a ball joint including an outer member 31a that is a spherical surface that can come into surface contact with the spherical surface of the inner member 31b, but the inner member 31b and the outer member 32b may be disposed in reverse. Good. That is, an outer member may be disposed on the main body portion 4b side and an inner member may be disposed on the piston 3 side.
The second universal joint portion 32 has an inner member 32b formed of a spherical protrusion provided on the main body portion 4b side of the connecting rod 4, and a recess provided on the connection arm portion 4c side for fitting the inner member 32b. Although the inner surface of the concave portion is a ball joint provided with the outer member 32a that is a spherical surface that can come into surface contact with the spherical surface of the inner member 32b, the inner member 32a and the outer member 32b may be arranged in reverse. . That is, an outer member may be disposed on the main body portion 4b side and an inner member may be disposed on the connection arm portion 4c side.

  FIG. 5 shows a modification. In this modified example, the universal joint portion is interposed at two places other than both ends of the connecting rod 4, that is, in the middle portion between both ends.

  In this example, the main body 4d of the connecting rod 4 is composed of two members, a first main body 4a and a second main body 4b.

One end of the first main body 4 a of the connecting rod 4 is connected to the piston boss 7 via a piston pin 8. Since the first main body portion 4 a of the connecting rod 4 is connected to the piston boss portion 7 via the piston pin 8, a hole through which the piston pin 8 is inserted is formed in the piston boss portion 7.
The other end of the first body portion 4a is connected to one end of the second body portion 4b via the first universal joint portion 31. The configuration of the first universal joint 31 is the same as that of the above-described embodiment.
The other end of the second body portion 4 b is connected to the connection arm portion 4 c of the connecting rod 4 via the second universal joint portion 32. The configuration of the second universal joint portion 32 is the same as that of the above-described embodiment.
The same is true in that the other end of the connection arm portion 4c is connected to the crankpin 11 of the crankshaft 10 so as to be rotatable about its axis.

Also in this modified example, the first universal joint portion 31 and the second universal joint portion 32 are interposed, so that even if the crankshaft 10 moves along the rotational axis direction, the rotational motion of the crankshaft 10 continues to be the piston. The action of converting to 3 reciprocating motions can be continued.
Further, the top dead center height and the bottom dead center height in the cylinder 5 of the piston 3 are changed by moving the connecting portion between the crankshaft 10 and the connecting rod 4 along the rotation axis direction of the crankshaft 10. The compression ratio can be increased or decreased.

  In the above embodiment, a ball joint (a ball-shaped universal joint using a ball joint) is used as the universal joint provided between the connecting rod 4 and the connecting rod 4 and the piston 3, but the type of the universal joint is a ball joint. It is not limited to. That is, as long as the reciprocating motion of the piston 3 can be transmitted to the rotational motion of the crankshaft 10 not only in a state where the axes of the members connected to each other are on the same straight line but also in a state of crossing each other, any A universal joint having the following form can be adopted. For example, both ends of the members to be connected to each other are bifurcated so that the members can bend up and down, swing, and swing across the joint portion, and the branched portions are arranged in a 90-degree orientation with respect to each other. A hook-shaped joint (cardan joint) or the like in which two branch portions are coupled with a cross-shaped pin can be employed.

  In each of the above embodiments, a four-cycle gasoline engine for automobiles has been described as an example. However, the present invention is not limited to this embodiment, and the present invention can be applied to, for example, a two-cycle gasoline engine and a diesel engine. The present invention can also be applied to reciprocating engines used in various transportation equipment other than automobiles and industrial machines.

1 Engine 2 Combustion chamber 3 Piston 4 Connecting rod (connecting rod)
5 Cylinder 6 Piston head 7 Piston boss 7
8 piston pin 10 crankshaft 11 crankpin 12 crank journal 13 crank web 14 connecting portion 15 crank boss portion 16 other end support portion 17 end boss portion 18 repulsive force applying means (elastic body)
19 One end support shaft 20 Presser 21 Oil passage 22 Piston 31, 32 Universal joint part 31a, 32a Outer member 31b, 32b Inner member

Claims (4)

A piston housed in a cylinder;
A connecting rod having one end connected to the piston;
A crankshaft to which the other end of the connecting rod is connected;
A connecting portion between the connecting rod and the piston, or at least two universal joint portions provided in an intermediate portion between both ends of the connecting rod;
By moving the connecting portion between the connecting rod and the crankshaft along the rotational axis direction of the crankshaft with respect to the axial center of the cylinder, the top dead center height and the bottom of the piston in the cylinder are moved. Variable compression ratio engine with variable compression ratio by changing dead height. The connecting rod is
A connecting arm portion rotatably attached to a crankpin of the crankshaft around the axis of the crankpin, and a main body portion connecting the connecting arm portion and the piston,
The universal joint portion is
A first universal joint provided between the main body and the piston;
A second universal joint provided between the main body and the connection arm;
The variable compression ratio mechanism engine according to claim 1. A presser provided at one axial end of the crankshaft, pressing the crankshaft toward the other axial end;
A repulsive force imparting means provided at the other axial end of the crankshaft and pressing the crankshaft toward one axial end;
The crankshaft is pressed by the pressing element and moved to the other end side in the axial direction, and the crankshaft is pressed by the repulsive force applying means in a state where the pressing force by the pressing element is released and moved to the one end side in the axial direction. Item 3. The variable compression ratio mechanism engine according to Item 1 or 2.   The crankshaft is pressed by the pressing element and moves to the other end side in the axial direction to shift to a low compression ratio state, and is pressed by the repulsive force applying means to move to one end side in the axial direction to move to the high compression ratio state. The variable compression ratio mechanism engine according to claim 3, which shifts to

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