JPS63277820A - Double crank type internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce vibration so as to improve mechanical efficiency by connecting each piston side end of connecting rods rotatably with each other, and providing thereby a displacement absorbing means which connects said end so as to be freely displaced to a specified direction. CONSTITUTION:Both a set of connecting rods 30A and 30B and a set of crank shafts 20A and 20B are arranged to one piston 13, and these crank shafts 20A and 20B are thereby allowed to be rotated synchronously in parallel with but opposite to each other. Large end sections 31A and 31B of the connecting rods 30A and 30B are rotatably connected with crank pins 22A and 22B. Small end sections 32A and 32B are connected with the piston 13 via an eccentric pin 40 acting as a displacement absorbing means. This constitution thereby not only enables vibration to be significantly reduced but also enables mechanical efficiency to be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a double-crank internal combustion engine that has two crankshafts for one piston, and is used for power applications that require low vibration and quietness. Can be used as a source.

[Conventional technology]

Traditionally, in order to avoid vibrations caused by engine rotation, a balance weight has been installed on the crankshaft to balance out the inertial force caused by the reciprocating movement of the piston.
Due to such a balance weight, a vibration with a component perpendicular to the piston movement direction and a counter torque due to a change in the rotational speed are generated.

On the other hand, in a mirror-image arrangement type double-crank internal combustion engine that has two crankshafts that rotate synchronously in parallel and opposite directions, a balance weight provided on each crankshaft allows the component perpendicular to the piston movement direction to be vibration and anti-torque can be canceled out by each other,
Vibration caused by driving can be extremely reduced.

[Problems to be Solved by the Invention] However, in a double crank internal combustion engine, if there is little play in the gear mechanism etc. for synchronously rotating the two crankshafts, the two crankshafts connecting each crankshaft and the piston may Book connecting rods always form a geometrically symmetrical isosceles triangle. Therefore, the movement axis of the piston is regulated on a constant axis following the piston-side end of the connecting rod,
It does not necessarily follow the axis of the cylinder, and high precision machining is required around the crank and cylinder to avoid excessive friction between the cylinder and piston and a decrease in mechanical efficiency. Consideration is required. This problem is caused by a decrease in the torsional rigidity of the crankshaft and a mismatch in torsional vibration modes at high rotation speeds.
This is particularly noticeable when there are multiple cylinders.

On the other hand, if the gear mechanism has backlash or a damper is inserted between the gear and the shaft, and a slight play is given to the isosceles triangle formed by the two sets of crankshafts and connecting rods, geometric symmetry can be achieved. The friction and efficiency problems mentioned above can be avoided by allowing some flexibility. However, the method of increasing the backlash of the gear mechanism has the problem of increased noise, and the method of interposing a damper etc. between the shaft and the gear requires a complicated mechanism to be installed in the high-speed rotating part.
This was structurally difficult and led to increased costs. Furthermore, since the play causes repeated impacts and associated vibration fatigue on each structural member, there is a problem in that particularly high strength is required.

[Means for solving problems]

In the present invention, two sets of connecting rods and crankshafts are arranged for one piston, and these crankshafts are rotated synchronously in parallel and opposite directions, and a displacement absorbing means is provided at the connecting portion between each of the connecting rods and the piston. The end portion is connected to the piston so as to be movable in a direction perpendicular to at least both the moving direction of the piston and the axial direction of the crankshaft, thereby forming a double crank internal combustion engine.

[Effect]

In the present invention, the displacement between the piston side end of each connecting rod and the piston is absorbed by the displacement absorbing means, and even if the play in the mirror image arranged crankshaft and connecting rod is eliminated, the geometrically symmetrical two Prevents the movement axis of the piston from being restricted by the equilateral triangle, achieving accurate and stable movement.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

A first embodiment of the invention is shown in FIGS. 1 and 2. FIG. In FIG. 1, an engine 10, which is a double crank internal combustion engine, is a so-called oHC type 4-stroke engine having a piston 13 that reciprocates within a cylinder 12 using combustion in a combustion chamber 11, and is shown in the lower part of the figure. There are two crankshafts 20A, 2 in the crankcase 14 of
Equipped with 0B.

These crankshafts 20A, 20B are arranged such that their rotation centers are parallel to each other in a direction orthogonal to the moving direction of the piston 13, and a gear 21A is provided integrally with each of them.
, 21B are meshed with each other and can rotate synchronously in opposite directions. Further, the crankshafts 20A and 20B each have crank pins 22A and 22B that are eccentric from the center of rotation, and balance weights 23A and 23B are provided on opposite sides of these crank pins 22A and 22B.

Here, the crank bins 22A and 22B have connecting rods 30A and 30B (7) large end portions 31A, respectively.
.

31B is rotatably connected to the connecting rod 30A.
, 30B, the small end portions 32A, 3 which are the ends on the piston 13 side.
2B is connected to the piston 13 via an eccentric piston pin 40 which is a displacement absorbing means.

As shown in FIG. 2, the eccentric piston pin 40 includes a large diameter part 42 as an eccentric part that is eccentric with respect to the center of small diameter parts 41 at both ends, and a ring-shaped collar 43 is attached to the piston 13 at the small diameter part 41. The crankshafts 20A and 20B are rotatably supported through the crankshafts, and are arranged parallel to the crankshafts 20A and 20B. Also,
The eccentric piston pin 40 has a large diameter portion 42 connected to the connecting rod 30A.

30B, and by changing the eccentric direction of the large diameter part 42 by rotating the eccentric piston pin 40, the piston 13 and the small end 32A,
32B are configured to be relatively displaceable in a direction orthogonal to the axis of the eccentric piston pin 40.

In this embodiment configured in this way, the combustion chamber 11
By combusting the air-fuel mixture at
The reciprocating movement of the eccentric piston pin 40 and connecting rod 30A
, 30B to the crankshafts 20A, 20B,
These are rotated synchronously in opposite directions. At this time, the small ends 32A, 32B of the connecting rods 30A, 30B are connected to the crankshafts 20A, 20B and the connecting rod 30A.

30B, it is always regulated on a constant axis. here,
If the axis of movement of the piston 13 changes due to thermal deformation of the cylinder 12, etc., the piston 13 will move between the small ends 32A and 32.
However, such displacement is absorbed by the change in the eccentric direction of the large diameter portion 42 due to the rotation of the eccentric piston pin 40.

According to this embodiment, the following effects can be obtained.

That is, since the eccentric piston pin 40 can absorb the displacement Rh that occurs between the piston 13 and the small ends 32A, 32B of the connecting rods 30A, 30B, the piston 13 and the cylinder 12 can be It is possible to prevent an increase in friction between the parts, improve mechanical efficiency, and enable stable operation.

Further, since the displacement of the piston 13 is not restricted by the small ends 32A, 32B, backlash in the gears 21A, 21B can be reduced, noise generation can be reduced, and smooth operation can be realized.

Furthermore, since the engine 10 of this embodiment uses the displacement absorbing means by the eccentric piston pin 40, no special space is required between the piston 13 and the crankshafts 2OA and 20B, and the overall height etc. It can be suppressed in the same way as an engine, and can be widely applied to small engines.

In addition, the eccentric piston pin 40 does not impair the function of a conventional mirror-image arrangement double-crank engine (balance weight 23A).

The inertial force of the piston 13 is canceled by the vertical component of the centrifugal force generated in the balance weight 23B, and the balance weight 23
Vibrations generated in the engine 10 can be significantly reduced by offsetting the centrifugal force in the lateral direction components in the drawings A and 23B, and counter torque of the balance weights 23A and 23B due to changes in rotational speed can be prevented.

In the first embodiment, as the eccentric piston pin 40 which is a displacement absorbing means, a large diameter portion 41 which is an eccentric portion eccentric to the small diameter portions 42 at both ends is formed in the middle.
However, as shown in FIG. 3, the eccentric portion may be formed by inserting both ends of the rod-shaped body 46 into the eccentric holes 45 of the two collars 44.

A second embodiment of the present invention shown in FIG. 4 uses a sub connecting rod as a displacement absorbing means, whereas the first embodiment has an eccentric piston pin 40 as a displacement absorbing means. Since the structure is the same as that of the first embodiment except for the displacement absorbing means, explanation of the similar parts will be omitted.

In FIG. 4, small end portions 3 of connecting rods 30A, 30B
2A and 32B are sub connecting rods 5 which are displacement absorbing means.
0 is penetrated by a connecting pin 51 and rotatably connected. Further, the other end of the sub connecting rod 50 is connected to a piston pin 52 in the piston 13, and the connecting pin 51 side is configured to be freely movable with respect to the piston 13.

In this embodiment configured in this way, the sub-connecting rod 50 swings relative to the piston 13 around the piston pin 52, so that the piston 13 and the connecting pin 5
1 and the small ends 32A, 32B.

In this embodiment, the same effects as those of the first embodiment can be obtained, and high precision can be achieved at low cost since parts such as the eccentric piston pin 40 that require precision processing are not required.

In addition, the small end 3 allowed by the sub connecting rod 50
The displacements of 2A and 32B can make the displacement of the piston 13 in the moving direction smaller than the displacement of the piston 13 in the radial direction, and the synchronization between the piston 13 and the crankshafts 20A and 20B can be made more accurate. The component force in the thrust direction caused by the fall can be further reduced.

In the second embodiment, a short sub-connecting rod 50 was used as the displacement absorbing means, but it may be a long one as shown in FIG. The intermediate portion 50A may be formed in the shape of a round bar and may be guided by a seal 53 that is slidably inserted therethrough, or the lower surface side of the piston 13 of the cylinder 12 may be used as a scavenging pump.

Furthermore, in each of the embodiments described above, the eccentric piston pin 40 or the sub connecting rod 50 is provided as a displacement absorbing means,
Although the small ends 32A and 32B are made movable in both the radial direction of the piston 13 and the movement direction of the piston 13, the displacement absorbing means is not limited to the above-mentioned one, but may have other structures. Good too.

For example, a rod-shaped piston pin is supported within the piston 13 so as to be movable in parallel in a direction perpendicular to the moving direction of the piston 13, and this rod-shaped piston pin is supported by the connecting rods 30A, 30B.
The small ends 32A, 32B may be passed through the small ends 32A, 32B of the two sets of crankshafts 2.
Since the piston 13 is restricted to a fixed axis by the connecting rods 0A, 20B and the connecting rods 30A, 30B, the piston 13 does not become unstable.

Further, in each of the above embodiments, the engine 10 is a 4-stroke OHC type, but the drive type of the intake and exhaust valves may be changed as appropriate in implementation, and the present invention
Excellent effects can be obtained not only in stroke engines but also in various types of two-stroke engines.

As described above, the present invention is not limited to the aspects of each of the embodiments described above, and any modification within the scope of the claims that can achieve the object of the present invention is included in the present invention.In short, At least the moving direction of the piston 13 and the crankshaft 20A are connected to the connecting portion between the piston 13 and the connecting rods 30A and 30B.

This means providing a displacement absorbing means that can tolerate displacement in a direction perpendicular to any of the rotation centers of 20B.

〔Effect of the invention〕

As described above, according to the double crank internal combustion engine of the present invention, vibrations accompanying operation can be reduced and
This has the effect of reducing friction generated between the piston and cylinder and improving mechanical efficiency.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention, FIG. 2 is a perspective view showing essential parts of the first embodiment, and FIG. 3 is a modification of the first embodiment. 14 is a longitudinal sectional view showing a second embodiment of the present invention, and FIG. 5 is a longitudinal sectional view corresponding to FIG. 4 showing a modification of the second embodiment. It is a diagram. 10...An engine that is a double crank internal combustion engine,
13...Piston, 20A, 20B...Crankshaft, 30A, 30B...Connecting rod, 40...Eccentric piston pin serving as a displacement absorbing means, 42.46...Large diameter portion serving as an eccentric portion, and Rod-shaped body, 50... Sub connecting rod which is a displacement absorbing means. Agent: Patent attorney Minoru Kinoshita (and 1 other person) Figures 2 and 3 8

Claims (3)

[Claims] (1) In a double-crank internal combustion engine in which two sets of connecting rods and crankshafts are arranged for one piston, and these crankshafts are rotated synchronously in parallel and opposite directions, the ends of the connecting rods on the piston side are Displacement absorbing means is provided which connects each other rotatably and connects the connected ends to the piston so as to be displaceable at least in a direction perpendicular to both the moving direction of the piston and the axial direction of the crankshaft. A double crank internal combustion engine characterized by: (2) In claim 1, the displacement absorbing means is an eccentric piston pin rotatably supported within the piston, and the eccentric piston pin is an eccentric portion eccentric from the rotational center axis of the connecting rod. A double-crank internal combustion engine characterized by a piston penetrating the end of the piston in a rotatable manner. (3) In claim 1, the displacement absorbing means is a swingable sub-con rod having one end connected to the piston, and the sub-con rod having the other end rotating toward the piston-side end of the connecting rod. A double-crank internal combustion engine characterized by being freely connected.