JP6818233B2 - Variable compression ratio internal combustion engine - Google Patents

Description

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

Various variable compression ratio mechanisms have been proposed for internal combustion engines. For example, in Patent Document 1, an eccentric mechanism is provided at the small end of the connecting rod, and this eccentric mechanism is connected to an actuator on the crankcase side by a link, and the eccentric mechanism is rotated by the actuator to increase the size of the connecting rod. A variable compression ratio mechanism that can change the distance between the end and the small end is disclosed.

Japanese Unexamined Patent Publication No. 2013-40607

In the piston of an internal combustion engine, the piston side pressure rises near top dead center due to the positional relationship between the combustion pressure and the connecting rod. In general, the load on the thrust side of the piston is high, so in many cases, a piston pin offset is provided on the anti-thrust side in order to improve the positional relationship with the connecting rod. The requirement for the amount of piston pin offset increases as the engine speed decreases, and decreases as the engine speed increases. Therefore, in general, the piston pin offset amount is increased in the low-speed engine and decreased or eliminated in the high-speed engine.

However, in Patent Document 1, since the eccentric mechanism is provided at the small end of the connecting rod as a means for changing the compression ratio, there is a problem that the piston pin offset amount changes with the compression ratio. Since the compression ratio requirement changes not only with the engine speed but also with the load, there is inevitably a range in which the piston pin offset amount does not match the requirement.

For example, as shown in FIG. 9, it is preferable to set a high compression ratio in order to improve thermal efficiency at low rotation speed and low load, but abnormal combustion such as knocking and pre-ignition at high rotation speed even at low rotation speed. It is preferable to use a low compression ratio in order to suppress the above. As described above, the requirements for the compression ratio differ depending on the load even at the same rotation speed, but in Patent Document 1, since the piston pin offset amount also changes as the compression ratio changes, the load on the thrust side or the anti-thrust side of the piston increases. , Increased friction, generation of piston slap noise, etc. are concerned.

Further, in Patent Document 1, since the eccentric mechanism having a double structure is provided at the small end of the connecting rod, the outer diameter of the small end of the connecting rod is inevitably large, and in addition, interference with the back surface of the piston is avoided. Since it is necessary to secure a large amount of relief and restrictions such as ensuring the strength of the piston are added, it is unavoidable to increase the weight and inertial weight, and it is undeniable that it is disadvantageous for weight reduction.

The present invention has been made in view of the above points of the prior art, and an object of the present invention is to provide an internal combustion engine having a variable compression ratio which is advantageous in avoiding a change in a piston pin offset amount and an increase in weight and inertial weight. To do.

In order to solve the above problems, the variable compression ratio connecting rod engine according to the present invention has at least one cylinder, a piston housed in the cylinder so as to be reciprocally slidable, and a crank having a crank pin corresponding to the piston. The shaft, the connecting rod whose large end is rotatably connected to the crank pin, and the first connecting portion which is rotatably connected to the piston via the piston pin and is in a position different from the piston pin. A swing member that is angularly displaceably connected to the small end of the connecting rod and a second connecting rod whose tip is at a different axis position from the first connecting rod is angularly displaceably connected to the rocking member. A movable rod whose base end is displaceable with respect to the connecting rod and a driving means for displacement of the movable rod with respect to the connecting rod are provided , and the driving means is a crankcase. The base end of the movable rod is fixedly arranged on the side, and the base end of the movable rod is connected to one end of an intermediate rocking member swayably supported by the connecting rod, and the other end of the intermediate rocking member is driven. It is connected to the tip of a swing arm that is swingably supported by a movable shaft that is displaced by means .

According to the above configuration, the present invention obtains an optimum compression ratio according to the operating conditions while avoiding a change in the piston pin offset amount and an increase in the diameter of the small end of the connecting rod and the accompanying increase in weight and inertial weight. be able to.

It is a side view which shows the variable compression ratio internal combustion engine which concerns on embodiment of this invention. It is a schematic perspective view which shows the variable compression ratio internal combustion engine which concerns on embodiment of this invention. It is an exploded perspective view which shows the variable compression ratio internal combustion engine which concerns on embodiment of this invention. It is a side view which shows each position of the crank angle (a) 0 degree, (b) 90 degree, (c) 180 degree, (d) 270 degree of the variable compression ratio internal combustion engine which concerns on embodiment of this invention. It is a schematic side view which shows each position of the crank angle 0 degree, 90 degree, 180 degree, 270 degree of the variable compression ratio internal combustion engine which concerns on embodiment of this invention. It is a side view of the main part which shows the low compression ratio position (a) and high compression ratio position (b) of the variable compression ratio internal combustion engine which concerns on embodiment of this invention. It is a schematic side view which shows the compression ratio change of the variable compression ratio internal combustion engine which concerns on embodiment of this invention. It is a side view which shows the variable compression ratio mechanism of a reference example . It is a graph which shows the relationship between an engine speed, a torque, and a required compression ratio.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 to 3 show a movable portion of an internal combustion engine 100 provided with a variable compression ratio mechanism 110 according to an embodiment of the present invention, in which an engine block or the like is omitted. FIG. 1 shows a two-dot chain line of a cylinder 10. It is outlined in. Although only one cylinder of the internal combustion engine 100 is shown in FIGS. 2 and 3, a plurality of cylinders may be arranged side by side in the axial direction of the crankshaft 2. The following description assumes the case of multiple cylinders.

A piston 1 is housed inside the cylinder 10 so as to be slidable back and forth, and a combustion chamber 10b whose volume changes according to the position of the piston 1 is provided between the crown surface 1a of the piston 1 and the cylinder head 10a. It is defined. The cylinder head 10a is provided with an intake valve and an exhaust valve (not shown). A piston ring groove 13 for mounting a piston ring is provided on the peripheral side surface of the piston 1, and a piston pin hole 12 for fitting the piston pin 11 penetrates below the groove 13 in the lateral direction.

The crankshaft 2 is composed of a crank journal 20, a crank pin 21, a balance weight 22, and a crank arm 23, and is rotatably supported by an engine block in the crank journal 20, and the crank pin 21 is a large end of a connecting rod 3. It is rotatably connected to 32 (bearing portion 30).

In a general reciprocating internal combustion engine, the piston pin is directly connected to the small end of the connecting rod, but in the internal combustion engine 100 provided with the variable compression ratio mechanism 110 according to the present invention, the small end 31 of the connecting rod 3 is It is connected to the piston pin 11 via the swing member 4 (see saw-shaped arm) described below.

The swing member 4 is a small-shaped link arm in which the entire or most of the swing member 4 is housed in the inner 14 surrounded by the skirt portion of the piston 1. A through hole 40 is provided in the substantially center of the swing member 4 so as to be angularly displaceably fitted to the piston pin 11, and arms 43 and 44 extend on both sides thereof.

A first connecting portion 41 is provided on one arm portion 43 located at a position different from the piston pin 11, and a small end 31 of the connecting rod 3 is connected to the first connecting portion 41 so as to be angularly displaceable. A second connecting portion 42 is provided on the other arm portion 44 located at a position different from the piston pin 11, and the tip 52 of the movable rod 5 is connected to the second connecting portion 42 so as to be angularly displaceable.

The base end 51 of the movable rod 5 (second connecting rod) is connected to the eccentric shaft 61 on one end side of the intermediate swing member 6 so as to be angularly displaceable, so that the movable rod 5 (second connecting rod) is substantially longitudinally connected to the connecting rod 3. It is provided so that it can be displaced. The movable rod 5 constitutes a four-node link mechanism together with the connecting rod 3, the swing member 4, and the intermediate swing member 6 (eccentric intermediate shaft 60).

The intermediate swing member 6 is rotatably supported by a bearing hole 36 penetrating near the large end 32 of the connecting rod 3, and has an eccentric intermediate shaft 60 having an eccentric shaft 61 protruding from one end side, and the other end 62. The base end 64 is non-rotatably fixed to the intermediate swing arm 63, and the tip 65 of the intermediate swing arm 63 (the other end of the intermediate swing member 6) is the tip of the swing arm 7. It is rotatably connected to 71.

In FIG. 3, the other end 62 of the eccentric intermediate shaft 60 and the base end 64 of the intermediate swing arm 63 are schematically shown as shafts and shaft holes having a circular cross section that are fitted to each other. Mutually fitted parts Torque can be transmitted as a fitting part of a non-rotating cross section such as a circular cross section or a square cross section, or an eccentric intermediate shaft 60 and an intermediate swing arm 63 are formed by one member. Is also good.

The swing arm 7 is swingably connected to an eccentric shaft 81 of a rotation shaft 8 that is angularly displaced toward the crankcase side at its base end 72 (bearing portion 70). The rotating shaft 8 is arranged in parallel with the crankshaft 2, and a pair of flange portions 82 (disk portions) are integrally provided adjacent to the connecting rod 3 of each cylinder, and the rotating shaft 8 is integrally provided between the flange portions 82. The eccentric shaft 81 is extended.

An actuator 9 (driving means) is connected to the rotating shaft 8 as schematically shown in FIG. As the actuator 9, various actuators that give an angular displacement to the rotating shaft 8 and have a holding force against the angular displacement can be used. For example, an electric or hydraulic motor that drives and rotates a worm wheel fixed to the rotating shaft 8 and a worm that engages with the worm wheel, and an electric or hydraulic rotary actuator that gives an angular displacement to the rotating shaft 8 can be used. it can.

(Change in piston top dead center position due to variable compression ratio mechanism)
In the variable compression ratio mechanism 110 configured as described above, the rotation shaft 8 is rotated by the actuator 9, and the angular positions (CH to CL) of the eccentric shaft 81 are changed as shown in FIG. , The distance between the eccentric shaft 81 and the crankshaft 2 and the distance between the swing arm 7 and the connecting rod 3 (eccentric intermediate shaft 60) are changed, and the intermediate swing member 6 is given an angular displacement centered on the eccentric intermediate shaft 60. ..

Along with this, the movable rod 5 is displaced relative to the connecting rod 3 in the substantially longitudinal direction, and the swing member 4 is angularly displaced about the first connecting portion 41 with the small end 31 of the connecting rod 3 and the crank pin. By changing the distance between the center 21a of the 21 and the center 11a of the piston pin 11, the top dead center position (CH to CL) of the piston 1 is changed, and the compression ratio is changed.

FIG. 6B shows the variable compression ratio mechanism 110 of the internal combustion engine 100 in which the piston 1 is in the high compression ratio position CH at the top dead center, and the eccentric shaft is above the rotation shaft 8 (control angle 0 °). 81 is located. On the other hand, FIG. 6A on the left side shows the variable compression ratio mechanism 110 ″ of the internal combustion engine 100 ″ in which the piston 1 ″ is in the low compression ratio position CL at the top dead center, with respect to FIG. 6B. , The rotation shaft 8 "rotates 90 ° counterclockwise in the drawing, and the eccentric shaft 81" is angularly displaced to the left side in the drawing of the rotation shaft 8 ". Along with this, the intermediate swing member 6 "rotates about 30 ° counterclockwise in the figure, the movable rod 5" moves downward, and the swing member 4 "turns about 5 ° counterclockwise in the figure. By moving, the piston 1 ″ is displaced to the lower low compression ratio position CL.

FIG. 7 shows the positions of the members when the rotation shaft 8 of the variable compression ratio mechanism 110 is angularly displaced to the control angles of 0 °, 45 °, and 90 °, and the variable compression ratio mechanism 110 is the connecting rod 3. A four-bar link mechanism is configured in which the intermediate rocking member 6 is the driving link, the rocking member 4 is the driven link, and the movable rod 5 is the intermediate link, and the intermediate rocking member is the driving link. It can be seen that the swing member 4 and the movable rod 5 are deterministically displaced with respect to the connecting rod 3 according to the displacement of the member 6.

(Relationship between displacement by variable compression ratio mechanism and periodic displacement according to crank angle)
The variable compression ratio mechanism 110 according to the embodiment has a swing arm 7 and an intermediate swing member 6 from an actuator 9 outside the reciprocating motion of the piston 1 to a movable rod 5 on the connecting rod 3 side that reciprocates with the piston 1. As shown in FIGS. 4 and 5, the swing arm 7 and the intermediate swing member 6 swing with the reciprocating motion of the piston 1 because the displacement CV is transmitted via the piston 1.

Therefore, other than the top dead center, the displacement (CH to CL) given by the variable compression ratio mechanism 110 is added with a periodic displacement according to the crank angle, but at the top dead center, the variable compression ratio mechanism is exclusively used. The top dead center position (CH to CL) of the piston 1 is determined by the displacement given by 110.

Further, even if it is assumed that the bottom dead center position is displaced in the same direction as the top dead center position by adding a periodic displacement according to the crank angle, the displacement of the bottom dead center position is The effect on the compression ratio is negligible.

Therefore, regardless of the displacement of the bottom dead center, a desired compression ratio can be obtained according to the top dead center position (CH to CL) by the variable compression ratio mechanism 110.

Incidentally, referring to FIG. 5, when the eccentric shaft 81 of the rotating shaft 8 is in the high compression ratio position CH, the eccentric shaft 61 of the eccentric intermediate shaft 60 is above the center 60a of the eccentric intermediate shaft 60 (top dead center). Since the displacement (61') is performed on the point side), the displacement of the bottom dead center in the reciprocating direction of the piston 1 is almost the same as that on the top dead center side.

On the other hand, as shown by the two-point chain line in FIG. 7, when the eccentric shaft 81 of the rotating shaft 8 is in the low compression ratio position CL (81 ″), the intermediate swing member 6 ″ (intermediate swing arm 63). ″) Is displaced downward, and the eccentric shaft 61 of the eccentric intermediate shaft 60 is displaced laterally, but this displacement is canceled by the displacement according to the crank angle on the bottom dead center side, and the reciprocating direction of the piston 1 There is almost no displacement of the bottom dead center to. That is, the displacement of the bottom dead center according to the crank angle acts in the direction of further reducing the minimum compression ratio (the direction of expanding the variable range CV of the compression ratio). It will be.

(Effect obtained by the variable compression ratio mechanism of the embodiment)
In the variable compression ratio mechanism 110 configured as described above, the piston pin 11 is connected to the swing member 4 so as to be angularly displaceable without an eccentric mechanism or the like.
(I) Even if the compression ratio is changed, the offset position of the piston pin does not change and is held at the optimum position. Therefore, it is possible to suppress an increase in friction on the thrust side or the anti-thrust side and the generation of a piston slap sound due to fluctuations in the piston pin offset.
(Ii) It is possible to avoid an increase in the required space above the piston pin (clearance for avoiding interference with the back surface of the piston), which is advantageous for making the piston compact.
(Iii) The relative motion of the connecting rod, the swinging member, and the movable arm due to the reciprocating motion of the piston is small, and the relative angular velocity is equivalent to that of a normal connecting rod having no variable compression mechanism, so that deterioration of lubrication conditions can be avoided. ..

Since the second connecting portion 42 of the swinging member 4 is located at a position different from the piston pin 11 (11a), a lever ratio corresponding to the control force transmitted via the movable rod 5 can be obtained, and the load of the driving means can be obtained. It is advantageous in avoiding the increase.

Therefore, the configuration in which the line connecting the center of the large end (21a) of the connecting rod 3 and the center 11a of the piston pin 11 passes between the center of the first connecting portion 41 and the center of the second connecting portion 42 of the swing member 4. In addition to being particularly advantageous in the above points, the combustion pressure received by the piston 1 is proportionally divided between the connecting rod 3 and the movable rod 5 (second connecting rod) via the swing member 4, so that the compression ratio It is also advantageous in avoiding fluctuations in transmission efficiency to the crankshaft due to changes.

Due to the configuration in which the center 11a of the piston pin 11 is on the combustion chamber side with respect to the line connecting the center of the first connecting portion 41 and the center of the second connecting portion 42 of the swing member 4 (FIG. 5), it accompanies the reciprocating motion of the piston. It is possible to avoid an increase in clearance above the piston pin due to the swing of the swing member 4 (FIGS. 4 and 5), which is advantageous in reducing the size of the piston.

Since the movable rod 5 is connected to the connecting rod 3 via the eccentric intermediate shaft 60, the connecting rod 3, the swinging member 4, and the movable rod 5 have a structure similar to that of a truss, and the combustion pressure received by the piston 1 is increased. It is reliably transmitted to the crankshaft 2 via the connecting rod 3 and the movable rod 5 (second connecting rod).

Further, in the illustrated example, when the piston 1 is on the top dead center side, the link of the intermediate swing member 6 (center 60a of the eccentric intermediate shaft 60-eccentric shaft 61) and the movable rod 5 are linearly arranged. By setting the initial displacement angle of the eccentric shaft 61 (so as to be the dead center of the four-section link mechanism), the combustion pressure received by the piston 1 is the connecting rod 3 and the movable rod 5 (second connecting rod). ), There is also an advantage that it is more effectively transmitted to the crankshaft 2.

( Reference example )
FIG. 8 shows the vicinity of the connecting rod 203 of the internal combustion engine 200 provided with the variable compression ratio mechanism 210 according to the reference example of the present invention. The configuration of the piston and the crankshaft omitted in the drawing is the same as that of the embodiment, but in the variable compression ratio mechanism 210 of the reference example , the connecting rod 203 that reciprocates together with the piston 1 as a driving means for displaces the movable rod 205. Is provided with a hydraulic cylinder 207.

The hydraulic cylinder 207 is formed at the large end 232 of the connecting rod 203, and the base end 251 of the movable rod 205 is connected to the tip 261 of the piston rod 206 integrated with the piston 271. An oil passage 273 is communicated with the oil chamber 270 of the hydraulic cylinder 207, and the oil passage 273 communicates with the oil passage penetrating the inside from the end of the crankshaft to the crankpin in the bearing surface. Since the structure of this oil passage is well known, detailed description thereof will be omitted here.

According to the variable compression ratio mechanism 210 configured as described above, the piston rod 206 protrudes against the urging of the return spring 272 by supplying the oil pressure to the oil chamber 270 through the oil passage 273, and the movable rod. 205 is held at the high compression ratio position CH. When the supply of hydraulic pressure is stopped, the piston rod 206 retracts due to the urging of the return spring 272, and the movable rod 205 is held at the low compression ratio position CL.

In this way, by displacing the movable rod 205 to the high compression ratio position CH or the low compression ratio position CL by the hydraulic cylinder 207, the second connecting portion 242 is attached to the tip 252 of the movable rod 205 as in the embodiment. The connected rocking member 204 is angularly displaced about the first connecting portion 241 to change the distance between the crank pin and the piston pin 211, and the compression ratio of the internal combustion engine 200 is changed.

Further, when the combustion pressure is high, the force received by the piston 1 is transmitted to the hydraulic cylinder 207 via the movable rod 205, so that the sudden increase in the in-cylinder pressure can be alleviated and knocking can be avoided.

Further, by interposing the spring in series with the hydraulic cylinder, the force received by the piston 1 is transmitted to the spring via the movable rod 205, and the spring is compressed and deformed, thereby causing a sudden in-cylinder pressure as described above. It can also mitigate the rise and avoid knocking.

In the above reference example , the case where the single-acting hydraulic cylinder 207 is used is shown, but by forming oil chambers on both sides of the piston 271 and providing oil passages communicating with each oil chamber, the double-way hydraulic cylinder It can also be.

The variable compression ratio mechanism 210 configured as described above needs to be provided with a hydraulic system through the crankshaft, but on the other hand, a link mechanism (intermediate rocking) for transmitting a control force from the outside of the piston reciprocating motion to the movable arm 205. The moving arm 63 and the swing arm 7) can be omitted, which is advantageous in terms of simplification and weight reduction of the mechanism.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, the case where the compression ratios of a plurality of cylinders are changed all at once by the rotating shaft 8 and the actuator 9 is shown, but an actuator can be provided in each cylinder and the compression ratio can be controlled for each cylinder.

Further, instead of angularly displacement the support shaft (eccentric shaft 81) of the base end 72 of the swing arm 7, a member (slide block or the like) provided with the support shaft is displaced by using a linear actuator such as a screw feed mechanism or a hydraulic cylinder. It can also be displaced linearly to control the compression ratio.

Further, in the above embodiment, the case where the eccentric mechanism (eccentric intermediate shaft 60) is used as the link of the intermediate swing member 6 is shown, but a general link other than the eccentric mechanism (lever including the intermediate swing arm 63) Can also be used.

In each of the above embodiments, the piston pins 11 and 211 are connected to substantially the center of the swing members 4, 204, and the movable rods 5, 205 are connected to the second connecting portions 42, 242 located at different axes from the piston pins 11 and 211. Although the case of being connected is shown, the second connecting portions 42 and 242 may be in the coaxial position with the piston pins 11 and 211.

In each of the above embodiments, the installation directions of the movable rods 5, 205 and the swing arm 7 with respect to the rotation direction of the crankshafts 2 of the internal combustion engines 100 and 200 are not particularly limited, and may be in the direction opposite to the illustrated example. good.

1 Piston 2 Crankshaft 3,203 Connecting rod 4,204 Swing member 5,205 Movable rod 6 Intermediate rocking member 7 Swing arm 8 Rotating shaft 9 Actuator (driving means)
10 Cylinder 11,211 Piston pin 21 Crank pin 31,231 Small end 32,232 Large end 41,241 First connection 42,242 Second connection 51,251 Base end 52,252 Tip 60 Eccentric intermediate shaft 61 Eccentric shaft 63 Intermediate swing arm 207 Hydraulic cylinder (driving means)
206 Piston rod 271 Piston 272 Return spring 100,200 Internal combustion engine 110,210 Variable compression ratio mechanism

Claims (5)

With at least one cylinder,
A piston housed in the cylinder so as to be slidable back and forth,
A crankshaft having a crankpin corresponding to the piston,
A connecting rod whose large end is rotatably connected to the crank pin,
An oscillating member that is angularly displaceably connected to the piston via a piston pin and is angularly displaceably connected to the small end of the connecting rod at a first connecting portion that is located at a position different from the piston pin.
A movable tip that is angularly displaceably connected to the swinging member at a second connecting portion that is located at a different axis position from the first connecting portion, and a base end that is displaceably provided with respect to the connecting rod. With the rod
A driving means that displaces the movable rod with respect to the connecting rod, and
Equipped with a,
The drive means is fixedly arranged on the crankcase side.
The base end of the movable rod is connected to one end of an intermediate rocking member swayably supported by the connecting rod, and the other end of the intermediate rocking member swings to a movable shaft displaced by the driving means. Connected to the tip of a swing arm that is movably supported,
Variable compression ratio internal combustion engine. The variable compression ratio internal combustion engine according to claim 1, wherein the second connecting portion is located at a position different from the piston pin. The variable compression ratio internal combustion engine according to claim 1 or 2, wherein a line connecting the center of the large end of the connecting rod and the center of the piston pin passes between the center of the first connecting portion and the center of the second connecting portion. The variable compression ratio internal combustion engine according to any one of claims 1 to 3, wherein the center of the piston pin is on the combustion chamber side with respect to the line connecting the center of the first connecting portion and the center of the second connecting portion. With at least one cylinder,
A piston housed in the cylinder so as to be slidable back and forth,
A crankshaft having a crankpin corresponding to the piston,
A connecting rod whose large end is rotatably connected to the crank pin,
An oscillating member connected to the small end of the connecting rod, an intermediate oscillating member connected to the large end side of the connecting rod, and the oscillating member to form a four-node link mechanism including the connecting rod. And a movable rod that connects the intermediate rocking member,
The piston pin connected to the swing member and
A driving means for angularly displacement the intermediate swing member with respect to the connecting rod,
Equipped with a,
The drive means is fixedly arranged on the crankcase side.
The base end of the movable rod is connected to one end of the intermediate swing member, and the other end of the intermediate swing member is a swing arm oscillatingly supported by a movable shaft displaced by the drive means. Connected to the tip,
Variable compression ratio internal combustion engine.

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