JP2005113743A - Variable compression ratio internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technique for restricting effects of variation of a compression ratio on vibration states of an internal combustion engine and combustion control in a V-type internal combustion engine in which the compression ratio can be varied in simple constitution. <P>SOLUTION: In this V-type variable compression ratio internal combustion engine, two inclined cylinder blocks are relatively moved to a crankcase, so that the compression ratio in the respective cylinders in the cylinder blocks are varied. The intersection of center axes of the cylinders in the two cylinder blocks exists at Obs on the cylinder block side to a crankshaft center Oc when the V-type internal combustion engine has the minimum compression ratio, and at Obr on the opposite side of the cylinder blocks to the crankshaft center Oc when the V-type internal combustion engine has the maximum compression ratio. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a variable compression ratio internal combustion engine in which a compression ratio is variable by changing a combustion chamber volume, and more particularly to a V-type internal combustion engine having two inclined cylinder blocks.

  In the conventional internal combustion engine, the volume of the combustion chamber is constant and the compression ratio is also constant. However, if an optimal compression ratio can be obtained according to the driving state, fuel efficiency and output performance can be improved. In view of this, a variable compression ratio type internal combustion engine has been proposed in which the performance is improved by variably controlling the compression ratio.

As a method of variably controlling the compression ratio, a cylinder block formed with a cylinder and a crankcase are connected so as to be relatively movable, and a cam mechanism interposed between the cylinder block and the crankcase is used. There has been proposed a technique for changing the compression ratio of an internal combustion engine by moving a cylinder block and a crankcase closer to or away from each other (see, for example, Patent Document 1).
JP 7-26981 A JP 2003-206871 A Japanese Patent Laid-Open No. 2002-9040 Japanese Patent Laid-Open No. 2002-250241 JP 2002-256801 A JP 2002-256802 A JP 2003-515696 A

  Considering the case where the above prior art is applied to a V-type internal combustion engine, when changing the compression ratio, the two cylinder blocks are integrally moved relative to the crankcase to simplify the mechanism. Desirable from a viewpoint. However, in this case, the amount of offset of the crankshaft center with respect to the cylinder center axis in the two cylinder blocks changes. When the amount of offset of the crankshaft center with respect to the cylinder center shaft changes, the state of the piston slap changes, and accordingly, the controllability of combustion control such as KCS control changes. Further, the state of higher-order unbalance force generated in the internal combustion engine changes. As a result, the vibration state in the V-type internal combustion engine and the combustion control may be adversely affected.

  An object of the present invention is a technology that can change the compression ratio with a simple mechanism in a V-type internal combustion engine and can suppress the influence of the change of the compression ratio on the vibration state and combustion control of the internal combustion engine. Is to provide.

  In order to achieve the above object, the present invention is a variable compression ratio internal combustion engine in which two inclined cylinder blocks in a V-type internal combustion engine are integrally moved relative to a crankcase, and the compression ratio is changed. At this time, the intersection of the center axes of the cylinders in the two cylinder blocks (hereinafter, referred to as “cylinder center axis intersection”) has a maximum movement range including the crankshaft center in the V-type internal combustion engine. Features.

More specifically, the V-type variable compression ratio internal combustion engine changes the compression ratio in each cylinder of the cylinder block by integrally moving the two inclined cylinder blocks in the V-type internal combustion engine relative to the crankcase. When the V-type internal combustion engine has the minimum compression ratio, the cylinder center axis intersection is on the two cylinder blocks side with respect to the crankshaft center, and when the V-type internal combustion engine has the maximum compression ratio, The crankshaft is on the opposite side of the two cylinder blocks with respect to the center of the crankshaft.

  Here, when the compression ratio is changed in the V-type internal combustion engine, the two cylinder blocks are moved integrally in the vertical direction with the two cylinder blocks facing up. Thus, it is conceivable to move relative to the crankcase. As described above, this is desirable from the viewpoint of simplifying the mechanism.

  In this case, when the compression ratio of the V-type internal combustion engine is changed to the low compression ratio side, the cylinder center axis intersection point is the center of the V shape constituted by the center axes of the cylinders in the two cylinder blocks. Move upward on a line (hereinafter referred to as “cylinder block center line”).

  Conversely, the cylinder center axis intersection moves downward on the cylinder block center line when the compression ratio of the V-type internal combustion engine is changed to the high compression ratio side.

  In the present invention, as described above, in the V-type internal combustion engine, when the two cylinder blocks are integrally moved relative to the crankcase, the intersection of the cylinder center axes is the minimum compression of the V-type internal combustion engine. When the V-type internal combustion engine has the maximum compression ratio, it is on the opposite side of the two cylinder blocks with respect to the crankshaft center. By doing so, the intersection of the cylinder center axes and the center of the crankshaft are prevented from being separated too much with the change of the compression ratio.

  In this way, the amount of offset of the crankshaft center with respect to the center axes of the two cylinders in the V-type internal combustion engine (hereinafter referred to as “crank offset amount”) can be prevented from becoming excessive.

  Here, the crank offset amount in the internal combustion engine affects the state of the piston slap and the controllability such as KCS control related thereto. It also affects the magnitude of higher-order unbalance forces generated in the internal combustion engine.

  Piston slap refers to a phenomenon in which the piston tilt angle changes near the top dead center of the internal combustion engine and noise is generated. The degree of occurrence changes depending on the amount of crank offset. The KCS control is a control for preventing the occurrence of knocking by outputting an optimal ignition timing signal of the spark plug from the ECU in accordance with the knocking state detected by the knock sensor. Therefore, when abnormal noise or impact due to piston slap increases, the controllability of the KCS control is also adversely affected. Further, the higher-order unbalanced force generated in the internal combustion engine is an inertial force that causes vibration that cannot be canceled by addition of a counterweight, and the magnitude of the force increases as the crank offset increases. I know.

  Therefore, in the present invention, as described above, the crank offset amount in the V-type internal combustion engine can be prevented from being excessive, and therefore, the influence of the variable compression ratio control on the controllability such as piston slap and KCS control is excessive. Can be suppressed, and the high-order unbalance force of the internal combustion engine can be suppressed from becoming excessive. As a result, the compression ratio can be changed with a simple mechanism without affecting the vibration state and combustion control of the internal combustion engine.

Here, when the V-type internal combustion engine is symmetrical, the crankshaft center is on the cylinder block center line. However, in practice, in order to optimize the state of piston slap and the like while suppressing the above-mentioned higher-order unbalance force as much as possible, the center of the crankshaft is intentionally shifted with respect to the cylinder block center line. In some cases, the center axis of the cylinder in the cylinder block is offset with respect to the center of the crankshaft.

  At this time, the amount of crank offset is uniquely determined geometrically by the amount of deviation between the crankshaft center and the cylinder block center line. Accordingly, the deviation amount between the crankshaft center and the cylinder block center line is set so that the crank offset amount becomes an optimum value from the viewpoint of the above-mentioned higher-order unbalance force and the influence on the piston slap.

  Also in such a case, in the present invention, when the V-type internal combustion engine has a minimum compression ratio, the cylinder center axis intersection is on the two cylinder block side with respect to the crankshaft center, and the V-type internal combustion engine When the engine reaches the maximum compression ratio, the crank offset is greatly deviated from the above-mentioned optimum value by making the cylinder center axis intersection point on the opposite side of the two cylinder blocks with respect to the crankshaft center. Can be suppressed. Therefore, it is possible to suppress the variable compression ratio control from adversely affecting the vibration state and combustion control in the V-type internal combustion engine.

  In the present invention, when the cylinder center axis intersection is the center compression ratio in the compression ratio variable range of the V-type internal combustion engine, the cylinder center axis intersection is closest to the crankshaft center. Is good.

  By doing so, the cylinder center axis intersection moves in a substantially symmetric range around the point closest to the crankshaft center, which can occur in the variable compression ratio control of the V-type internal combustion engine. The maximum value of the crank offset can be suppressed. Therefore, it is possible to more effectively suppress the variable compression ratio control from adversely affecting the vibration state and combustion control in the V-type internal combustion engine.

  Further, if the amount of deviation between the cylinder center axis intersection at this time and the center of the crankshaft is set so that the crank offset amount becomes the optimum value as described above, the center of the variable compression ratio range of the V-type internal combustion engine can be reduced. In the compression ratio, the vibration state of the V-type internal combustion engine and the state of combustion control can be optimized.

  In this case, the maximum deviation of the crank offset amount from the optimum value, which can occur in the variable compression ratio control of the V-type internal combustion engine, can be reduced. Therefore, the variable compression ratio control can be performed in a vibration state in the V-type internal combustion engine or in a state where the combustion control is close to optimum.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, in a V-type internal combustion engine, the compression ratio can be changed with a simple mechanism, and the influence of the change in the compression ratio on the vibration state and combustion control of the internal combustion engine can be suppressed. .

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 which is a V-type variable compression ratio internal combustion engine according to the present embodiment. In this embodiment, the two cylinder blocks 3 and 23 that are inclined symmetrically with respect to the center line L of the crankcase 4 form a V-shaped bank. The tilt angles of the cylinder blocks 3 and 23 are 45 degrees with respect to the center line L of the crankcase 4. A plurality of cylinders are formed in the two cylinder blocks 3 and 23. FIG. 1 shows only a cross-sectional view of the cylinders 3a and 23a in the foremost side. The configuration of the cylinder not shown in the cross-sectional view is substantially the same as the configuration of the cross-sectional view shown in FIG.

  In the present embodiment, the two cylinder blocks 3 and 23 are integrated by being connected by the connecting portion 6 to form the V-type cylinder block 2. Then, the compression ratio in each bank is changed by moving the V-shaped cylinder block 2 up and down along the center line L of the crankcase 4 with respect to the crankcase 4.

  Here, cam mechanisms 7 a and 7 b are provided at the lower portions on both sides of the V-shaped cylinder block 2. And the worm wheels 8a and 8b shown with a broken line are attached to one end of each cam mechanism 7a and 7b in the front direction with respect to the paper surface. Further, the worm wheels 8 a and 8 b are engaged with worms 9 a and 9 b indicated by broken lines attached to the output shaft of the motor 5.

  Then, by rotating the motor 5, the cam mechanisms 7a and 7b are operated via the worms 9a and 9b and the worm wheels 8a and 8b. The cam mechanisms 7 a and 7 b move the V-type cylinder block 2 in parallel with the center line L of the crankcase 4. With this series of operations, the compression ratio of each cylinder in the internal combustion engine 1 can be controlled. In the present embodiment, the center line L of the crankcase 4 coincides with the cylinder block center line.

Next, a change in the positional relationship between the intersection of the central axes of the cylinders 3a and 23a and the center of the crankshaft when the compression ratio of the V-type internal combustion engine in the present embodiment is changed will be described with reference to FIG.
Note that the vertical direction in FIG. 2 coincides with the vertical direction in FIG.

  In FIG. 2, the center of the crankshaft is represented by Oc. Further, the center axis of the cylinders 3a and 23a is represented by a one-dot chain line. The intersection of the central axes of the cylinders 3a and 23a when the compression ratio in the internal combustion engine 1 is minimized is Obs, and the intersection of the central axes of the cylinders 3a and 23a when the compression ratio in the internal combustion engine 1 is maximized. Expressed as Obr. In this embodiment, the intersection of the central axes of the cylinders 3a and 23a moves on the center line L of the crankcase 4 between Obs and Obr in accordance with the change control of the compression ratio of the internal combustion engine 1.

  Here, Obs is located on the V-type cylinder block 2 side with respect to Oc, and Obr is located on the opposite side of the V-type cylinder block 2 with respect to Oc.

  In the present embodiment, the crankshaft center Oc is shifted by Z in the horizontal direction with respect to the center line L of the crankcase 4. Further, the position of the crankshaft center Oc in the height direction in FIG. 2 is the same position as the midpoint Obc of the line segment connecting Obs and Obr in FIG. That is, when the compression ratio in the internal combustion engine 1 is the central compression ratio between the maximum compression ratio and the minimum compression ratio, the intersection of the central axes of the cylinders 3a and 23a is closest to the crankshaft center Oc, and the amount of deviation at that time Is configured to be Z.

The above-described deviation amount Z is such that when the intersection of the central axes of the cylinders 3a and 23a is located at Obc, the offset amount of the crankshaft center Oc with respect to the central axes of the cylinders 3a and 23a in the internal combustion engine 1 is determined by the piston slap. It is a value set so as to be an optimum value from the viewpoint of the state and the magnitude of the higher-order unbalance force. At this time, the amount of offset of the crankshaft center Oc with respect to the center axis of the cylinders 3a and 23a is geometrically Z / √2. In other words, the optimum value of the offset amount of the crankshaft center Oc with respect to the center axis of the cylinders 3a and 23a is Z / √2.

  Here, consider a case where the compression ratio of the internal combustion engine 1 is minimized. At this time, the intersection of the central axes of the cylinders 3a and 23a is at Obs. The amount of offset between the center axis of the cylinder 3a and the crankshaft center Oc at this time is represented by Es3 as shown in the drawing. Similarly, the amount of offset between the center axis of the cylinder 23a and the crankshaft center Oc is represented by Es23.

  When the compression ratio of the internal combustion engine 1 is increased from that state, the intersection of the central axes of the cylinders 3a and 23a moves on the center line L of the crankcase 4 from Obs to Obr. During this time, the amount of offset between the center axis of the cylinder 3a and the cylinder 23a and the crankshaft center Oc once decreases. When the intersection of the central axes of the cylinders 3a and 23a reaches Obc, the amount of offset of the crankshaft center Oc with respect to the central axis of the cylinders 3a and 23a is Z / √2. Thereafter, when the compression ratio is further increased and the compression ratio of the internal combustion engine 1 becomes maximum, the intersection of the central axes of the cylinder 3a and the cylinder 23a reaches Obr. The amount of offset between the center axis of the cylinders 3a and 23a and the crankshaft center Oc at this time is represented by Er3 and Er23, respectively, as shown in the figure.

  As described above, in the present embodiment, the intersection of the central axes of the cylinders 3a and 23a is on the V-type cylinder block 2 side with respect to the crankshaft center Oc when the internal combustion engine 1 has the minimum compression ratio. When the internal combustion engine 1 has the maximum compression ratio, it is on the opposite side of the V-type cylinder block 2 with respect to the crankshaft center Oc, so that the crankshaft center Oc is the center of the cylinders 3a and 23a with respect to the horizontal direction in FIG. It can be included in the movement range of the intersection of axes.

  Thereby, the center axis of the cylinders 3a and 23a is compared with the case where the crankshaft center Oc is located above or below the movement range of the intersection of the center axes of the cylinders 3a and 23a in the horizontal direction in FIG. The amount of offset from the center of the crankshaft does not greatly deviate from Z / √2, which is the optimum amount of offset considering piston slap and higher-order unbalance force.

  Furthermore, as shown in FIG. 2, when the compression ratio of the internal combustion engine 1 is the compression ratio at the center of the variable range, the crankshaft center Oc and the intersection of the center axes of the cylinders 3a and 23a are closest. Since the distance is set to Z, the maximum value of the difference between the amount of offset that can occur in the compression ratio change control in the internal combustion engine 1 and Z / √2 that is the optimum amount of offset is suppressed. be able to.

  Next, a change in the amount of offset between the center axis of the cylinder 3a and the crankshaft center Oc when the compression ratio is changed as described above will be described based on the graph of FIG. FIG. 3 is a graph in which the compression ratio in the internal combustion engine 1 is plotted on the horizontal axis, and the amount of offset between the central axis of the cylinder 3a and the crankshaft center Oc is plotted on the vertical axis.

In FIG. 3, when the compression ratio in the internal combustion engine 1 is the minimum εs, the intersection of the central axes of the cylinders 3a and 23a is at Obs. The amount is Es3. Here, as the compression ratio increases, the amount of offset approaches zero. Then, when the value of the compression ratio becomes εm, which is the compression ratio in the middle of the maximum compression ratio and the minimum compression ratio in the variable compression range of the internal combustion engine 1, the amount of offset is Z / √2. When the compression ratio further increases, the maximum compression ratio εr is reached after passing through the compression ratio where the amount of offset becomes zero. Here, since the intersection of the central axes of the cylinders 3a and 23a is at Obr, the amount of offset between the central axis of the cylinder 3a and the crankshaft center Oc is Er3.

  In FIG. 3, the offset amount between the center axis of the cylinder 3a and the crankshaft center Oc has been described. However, the cylinder 23a has a substantially similar graph.

  From the graph of FIG. 3 as well, in the present embodiment, the amount of offset between the center axis of the cylinders 3a and 23a and the crankshaft center Oc in the compression ratio at the center of the compression ratio variable range of the internal combustion engine 1 is the piston slap. It can also be understood that the optimal offset amount Z / √2 is set in consideration of higher-order unbalance force and the like. When the compression ratio of the internal combustion engine 1 is changed, the offset amount is varied substantially symmetrically about the optimum offset amount Z / √2, and the offset amount greatly deviates from Z / √2. It can be understood that this is suppressed.

  In this embodiment, the amount of horizontal deviation between the crankshaft center Oc and the centerline L of the crankcase 4 is set to Z, but when this is set to 0, the cylinders 3a and 23a FIG. 4 shows a change in the positional relationship between the intersection of the central axes and the center of the crankshaft. That is, FIG. 4 is a diagram when Z = 0 in FIG. In FIG. 4, the crankshaft center Oc is on the center line L of the crankcase 4. Therefore, when the compression ratio in the internal combustion engine 1 is the central compression ratio in the variable range, the intersection Obc of the central axes of the cylinder 3a and the cylinder 23a coincides with the crankshaft center Oc.

  Therefore, in this case, the crank offset amount in the cylinders 3a and 23a can be simultaneously reduced to 0 in the compression ratio at the center of the variable range. Further, even in a compression ratio other than the central compression ratio of the variable range, the amount of offset between the center axis of the cylinder 3a and the crankshaft center Oc and the amount of offset between the center axis of the cylinder 23a and the center of the crankshaft Oc are made equal. Can do. Furthermore, in FIG. 4, since the distance between Oc and Obs is the same as the distance between Oc and Obr, the sizes of Es3, Es23, Er3, and Er23 can all be made equal.

It is the figure which showed schematic structure of the internal combustion engine which is a V-type variable compression ratio internal combustion engine which concerns on a present Example. It is a figure which shows the positional relationship of the intersection of the central axis of two cylinders in a present Example, and a crankshaft center. It is a graph which shows the change of the amount of offsets between the center axis | shaft of a cylinder, and the center of a crankshaft when the compression ratio of the internal combustion engine in a present Example changes. It is a figure which shows the positional relationship of the intersection of the center axis | shafts of two cylinders, and the crankshaft center when the amount of horizontal shift | offset | difference of the crankshaft center in a present Example and the centerline of a crankcase is set to 0. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... V type cylinder block 3, 23 ... Cylinder block 3a, 23a ... Cylinder 4 ... Crankcase 5 ... Motor 6 ... Connection part 7a, 7b ..Cam mechanism 8a, 8b ... Worm wheel 9a, 9b ... Worm 10 ... Crank shaft L ... Crank case center line Oc ... Crank shaft center Obs, Obc, Obr ... Cylinder center Axis intersection

Claims (2)

A variable compression ratio internal combustion engine for changing a compression ratio in each cylinder of the two cylinder blocks by integrally moving two inclined cylinder blocks in a V-type internal combustion engine relative to a crankcase. ,
The intersection of the center axes of the cylinders in the two cylinder blocks is on the side of the two cylinder blocks with respect to the center of the crankshaft when the V-type internal combustion engine has a minimum compression ratio in the compression ratio variable range, and the V The variable compression ratio internal combustion engine, wherein the internal combustion engine is on the opposite side of the two cylinder blocks with respect to the center of the crankshaft when the maximum compression ratio is within the variable compression ratio range.   The intersection of the center axes of the cylinders in the two cylinder blocks is closest to the center of the crankshaft when it is the central compression ratio in the compression ratio variable range of the V-type internal combustion engine. The variable compression ratio internal combustion engine according to claim 1.

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