JPH0765639B2 - Balancer shaft support device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a balancer shaft support device for a balancer provided in an engine.

(Prior Art) It is known that an inertial force is generated in an engine due to a reciprocating motion of a piston, and the inertial force causes vibration and the like in the engine. Therefore, a crank web is provided on the crankshaft in order to cancel out the inertial force due to the pistunt or the like and prevent the engine vibration or the like. However, since the crank web newly generates an inertial force in a direction orthogonal to the piston movement direction, and causes another vibration,
There is a need for a new balancer device that rotates at the same speed as the crankshaft and in the opposite direction to strike the extra inertial force of the crank web. That is, this balancer device cancels the inertial force of the piston in cooperation with the crank web in the moving direction of the piston and cancels the inertial force of the crank web in the direction orthogonal to the movement of the piston.

As an example of the above balancer device, see Japanese Utility Model Publication No. Sho 48-43281.
There is one shown in Japanese Patent Publication. This is as shown in FIG. 9, and the balancer shaft is composed of the crankcase 100 through which the crankshaft 101 is inserted and the gearcase 102 outside thereof.
106 is rotatably supported, and the balancer shaft 106 has a balancer 10
7 and the balancer gear 108 are fixed, and the crankshaft 10
With the crank gear 105 fixed to 1, the balancer gear 108 is rotated through a gear (not shown), and the balancer 107 is rotated. Incidentally, 104 is a crank web, and 103 is a connecting rod.

By the way, in a small stationary engine, that is, a so-called general-purpose engine, a small agricultural work machine such as a lawn mower, or an outboard motor, a recoil starter is used as a starting device, and a crank crank is generally used. Attach a recoil starter or flywheel to one end of the shaft,
The other end is used as the drive shaft of the device.

(Problems to be Solved by the Invention) In the above conventional technique, the balancer 107 is arranged outside the crankcase 100, and the crankcase 100 is compact and small. When the starter or flywheel is attached to the outside of the gear case 102, a special support member for the recoil starter is required.

As a result, the number of engine components increases in the above conventional technology, and the procedure for assembling the crankshaft 101 and the balancer shaft 106 with respect to the crankcase 100 and the gear gase 102 becomes complicated, and the difficulty is inevitable. Becomes

The present invention has been made to solve the above problems, and an object of the present invention is to provide a balancer outside the crankcase to make the crankcase itself compact and to attach it to a support member of the balancer shaft. The present invention provides a balancer shaft support device that has the function of supporting the above device to reduce the number of parts, downsize the entire engine, and facilitate the assembly of the engine.

(Means for Solving the Problems) Means for solving the above problems include a balancer shaft with a weight that rotates with the rotation of a crankshaft of an engine, and at least a part including a crank web of the crankshaft. A cylinder crankcase for accommodating, a balancer case formed in the cylinder crankcase for accommodating at least a part including a weight portion of the weighted balancer shaft, a case cover attached to the balancer case, One bearing provided on the balancer case for supporting one end of the balancer shaft, the other bearing provided on the case cover for supporting the other end of the balancer shaft, and the crankshaft Recoil star provided concentrically with the crankshaft on the axially outer end side A balancer shaft support device comprising: a starter; and a plurality of support portions provided on the case cover around the axis of the crankshaft to support the recoil starter.

Further, the crankshaft was placed almost vertically, and the lower end side was used as a power take-out portion.

(Operation) The weighted balancer shaft is supported outside the cylinder crankcase. Therefore, the cylinder crankcase becomes compact.

Further, the recoil starter is supported by the support portion at a plurality of positions sandwiching the crankshaft. For this reason, a separate component for supporting the recoil starter becomes unnecessary.

Furthermore, since the crankshaft is placed almost vertically and the lower end side is the power take-out portion, it can be mounted as a vertical engine.

(Embodiment) The first preferred embodiment of the present invention will be described with reference to an outboard motor as an example.
A detailed description will be given with reference to FIGS.

FIG. 1 shows an overall view of an outboard motor attached to a small boat, and 2 is a stern bracket attached to the stern of the hull via a clamp member 2a, and a swivel bracket 3 is pivotally attached via a support shaft 3a. I support you. The swivel shaft 4 rotatably supported in the swivel bracket 3 supports a middle portion of a support arm 5 on a head 4a, and one end of the support arm 5 supports an outboard motor body via an engine mount 6. 1 is supported, and an operation handle 7 is attached to the other end of the support arm 5.

The outboard motor body 1 has an external appearance including an engine cover 8 and an engine.
It is composed of an oil case 9 for supporting 20 and auxiliary equipment, and a lower case 10 to which a propeller 11 and the like are attached below it. When each case 9 and 10 are integrally connected by bolts or the like, The upper part of the case 10 is supported from both sides by extension mounts 12a of an arm member 12 extending from the swivel shaft 4 to prevent lateral contact of the outboard motor body 1 and the like.

FIG. 2 shows the structure of the engine 20 and auxiliary equipment supported on the oil case 9. The engine 20 is a 2-cylinder 4-cycle type in which a crankshaft 24 is vertically supported. Is a cylinder part having upper and lower pistons 22, 22, connecting rods 23, 23, etc.Cylinder block part 21a, 2
1a is formed, and a crankcase cylinder crankcase 21 in which a case half crankcase portion 21b is formed adjacent to the cylinder portions 21a, 21a and has a crankshaft 24 and the like, and the crankcase 21 Installed,
Cam shaft 26, rocker shaft 27, intake / exhaust valve 2
It is composed of an engine head 25 having 8, ...

The crankshaft 24 partially protrudes from the crank part 24a in the central part and the crankcase 21, and the lower shaft part 24b,
The crank portion 24a is provided with four crank webs 24a-1, ... (Balance weights) for canceling the inertial force generated by the reciprocating motion of the piston 22 and the like. Since the two pistons 22, 22 always move in the same direction, the four crank webs 24a-1, ... Are also arranged at the same position in the circumferential direction of the crankshaft 24 to cancel the inertial force generated by the pistons 22, 22, etc. It will rotate as much as possible.

Lower shaft part of the crankshaft 24 of the above engine 20
The propeller 11 is connected to 24c via a rotation transmission means (not shown), and a camshaft drive pulley 29 and a flywheel 30 are attached to the upper shaft portion 24b. A recoil starter 32 for manually starting the engine 20 is further connected to the upper shaft portion 24b via a starter pulley 31 supported by a flywheel 30.

Now, the balancer device 40 includes a drive gear 41, balancers 42, 42, a balancer case 43, a case cover 50, and the like.
A drive gear 41 of the balancer device 40 is attached to the upper shaft portion 24b of the crankshaft 24 between the upper portion of the crankcase 21 and the camshaft drive pulley 29, and the drive gear 41 is attached to the drive gear 41 as shown in FIG. Two balancers 42, 42 whose phases are shifted from each other by about 180 degrees around the drive gear 41 are engaged with each other via their gear portions 42c, 42c. The arrangement direction of the balancers 42, 42 around the crankshaft 24 is inclined by a predetermined obtuse angle (θ) with respect to the axial direction of the cylinder portion 21a of the crankcase 21 (longitudinal direction of the engine 20).

Here, the balancer 42 includes the gear portion 42c formed on the outer periphery in the radial direction and the weight portion 42 having a thick wall on one side in the radial direction.
a and a balancer shaft 42b arranged in parallel with the crankshaft 24, and the gear diameter of the gear portion 42c is equal to that of the drive gear 41, so that the gear portion 42c rotates in the opposite direction at the same rotation speed as the crankshaft 24. In addition, the weight portions 42a, 42a of the balancer gear 42 are arranged so that the weight portions 42a, 42a are oriented in the same direction with respect to the rotation of the crankshaft 24.

Next, the operation of the crank webs 24a-1, ... And the balancer device 40 will be described. The four crank webs 24a-1, ... Have a half of the inertial force due to the reciprocating mass of the crank system, and the weight portions 42a, 42a of the balancers 42, 42 of the balancer device 40 depend on the reciprocating mass. Each of the crank webs 24a-1, ... And the weight portions 42a, 42a are configured so that their directions coincide with each other at the top and bottom dead centers of the pistons 22,22. Therefore, the inertial force generated by the reciprocating motion of the pistons 22 and 22 becomes zero due to the cooperation of the crank webs 24a-1, ... And the balancer device 40, and the inertial force is generated by the crank webs 24a-1, ... and the balancer weight portions 42a, 42a. The inertial forces in the directions orthogonal to the movement directions of the pistons 22, 22 are also zero because the rotation directions are opposite to each other, and the vibration of the engine 20 is effectively suppressed.

In addition, since the acting surfaces of the balancer device 40 and the crank webs 24a-1, ...
A corner force acts to rotate the 24 up and down, and this corner force extends to the entire outboard motor body 1 through the oil case 9, but the outboard motor body 1 includes the engine mount 6 and the extension mount 12a. Since the upper and lower parts of the mount are supported by the swivel bracket 3, the corner force is applied to these mounts 6,12.
Absorbed and offset by a.

The balancer 42 is pivotally supported via a bearing 44 on a balancer case 43 formed by protruding the lower part of the balancer shaft 42b from the crankcase 21, and the upper part of the balancer shaft 42b is supported on the case cover 50 of the balancer case 43. It is pivotally supported via a bearing 44. The case cover 50 supports the starter case 33 of the recoil starter 32 above the case cover 50.

As is clear from the plan view of FIG. 5, the case cover 50 has a plurality of mounting holes 51, ...
The shaft hole 52 through which the upper shaft portion 24b of the crankshaft 24 is inserted is formed in the central portion while being fixed by tightening with a bolt or the like. A lower left portion of the shaft hole 52 in FIG. 5 is a bulging portion 57 that covers an upward projecting portion of the balancer 42, and a bearing holding portion 53 of the balancer shaft 42b is located in the central upper portion of the bulging portion 57. ing. Further, another bearing holding portion 53 of the balancer shaft 42b is also formed at a symmetrical position of the bulging portion 57 with respect to the shaft hole 52.

Further, as shown in FIG. 7, the case cover 50 is provided with three rising support parts 54 protruding upward and having screw holes 55, and these rising support parts 54, ... Are located above the flywheel 30.
So that it does not come out of the starter case 33
Are supported via bolts 58, .... Reference numeral 56 is an oil inlet.

A lower portion of the starter case 33 is supported by the case cover 50, and a recoil starter 32 having a rope groove 32a on an outer peripheral portion is pivotally supported on a downward protruding portion 33a of a central portion of the starter case 33. The arm that extends to
A guide hole 34 for the rope 35 is formed in 33b. Therefore, by pulling the rope 35 outward from the state where the rope 35 is wound around the rope groove 32a of the recoil starter 32, the recoil starter 32 rotates the flywheel 30 via the starter pulley 31 and starts the engine 20. .

In FIGS. 3 and 4, 60 is a carburetor, 61 is a starter for automatic engine start, and a vertically movable drive gear 62 meshes with the ring gear 30a of the flywheel 30 to start the engine 20. It is a thing.

(Effects of the Invention) As is clear from the above, according to the present invention, a cylinder crankcase for accommodating at least a part of the crankshaft of the crankshaft, including the weighted balancer shaft that rotates with the rotation of the crankshaft of the engine. And a balancer case formed on the cylinder crankcase for accommodating at least a part including the weight portion of the weighted balancer shaft, a case cover attached to the balancer case, and one end of the balancer shaft for supporting the balancer case. One bearing provided on the balancer case,
The other bearing provided on the case cover for supporting the other end of the balancer shaft, the recoil starter provided concentrically with the crankshaft at the axially outer end side of the crankshaft, and supporting this recoil starter. In order to achieve this, the balancer shaft with weights is supported outside the cylinder crankcase without increasing the size of the cylinder crankcase by being composed of a plurality of supporting parts provided on the case cover around the axis of the crankshaft. Moreover, the recoil starter can be easily supported by the support member at a plurality of positions around the axis of the crankshaft, and a separate component for supporting is unnecessary. Then, the entire engine can be made compact.

Further, since the crankshaft is placed almost vertically and the lower end side is used as the power take-out portion, it is easy to mount as a vertical engine.

[Brief description of drawings]

FIG. 1 is an overall view of the outboard motor, FIG. 2 is a cross-sectional side view of the engine and surroundings of the engine, and FIG.
FIG. 4 is a cross-sectional view of the balancer and a view showing a mounting state of other engine components, FIG. 5 is a plan view of a case cover of the balancer, FIG. 6 is a cross-sectional view taken along the line AA of FIG. FIG. 7 is a view showing a part of a sectional view taken along the line BB of FIG. 5, and FIG.
FIG. 9 is a sectional view taken along the line CC in FIG. 9, showing a conventional technique. In the drawing, 20 is an engine, 21 is a cylinder crankcase, 24 is a crankshaft, 32 is a recoil starter,
33 is a starter case, 42 is a balancer, 42b is a balancer shaft, and 50 is a case cover.

Claims (2)

[Claims] 1. A balancer shaft with a weight that rotates with the rotation of a crankshaft of an engine, a cylinder crankcase for accommodating at least a part of the crankshaft including a crank web, and a weight portion of the balancer shaft with a weight. A balancer case formed in the cylinder crankcase to accommodate at least a part of the balancer case, a case cover attached to the balancer case, and a balancer case provided to support one end of the balancer shaft. One bearing, the other bearing provided on the case cover to support the other end of the balancer shaft, and a recoil provided concentrically with the crankshaft at the axially outer end side of the crankshaft. In order to support the starter and this recoil starter, A balancer shaft support device comprising: a plurality of support portions provided on the case cover about the axis of the crankshaft. 2. The balancer shaft support device according to claim 1, wherein the crankshaft of the engine is placed substantially vertically, and a lower end side thereof serves as a power take-out portion.