JPH0792001B2 - Engine with balancer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an engine equipped with a balancer.

(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 this inertial force due to the piston or the like and prevent engine vibration or the like. However, because the crank web generates a new inertial force in the direction orthogonal to the piston movement direction and causes another vibration,
A new balancer is required to counteract the excess inertial force of the crank web by rotating in reverse at the same speed as the crankshaft. That is, this balancer cancels the inertial force of the piston in the direction of movement of the piston in cooperation with the crank web and cancels out the inertial force of the crank web in the direction orthogonal to the movement of the piston.

As shown in Japanese Utility Model Publication No. 52-32802, a pair of balancers as described above is generally provided in a pair on both sides of a crankshaft and driven by the crankshaft, and as described in the publication, the balancer is used. There is a structure in which the balancer is oriented obliquely with respect to the cylinder axis so that the balancer does not protrude from the engine body as much as possible. Further, the applicant of the present application, in the case of mounting the balancer as described above on the outboard motor, is to arrange the balancer on one side outside the engine body to reduce the size of the engine body.
-23333. That is, when mounting a balancer on a small internal combustion engine such as an outboard motor, the size of which is limited, a pair of balancers is mounted on the outside of the engine body around the crankshaft near the engine body, and The balancer is oriented obliquely to the cylinder axis to make the engine as small as possible, and
It is desirable to make the engine area as small and compact as possible.

Here, the crankcase of the engine body is generally formed by a skirt portion of the cylinder block and a split case assembled to the skirt portion, and the crankshaft is housed so as to be sandwiched between the skirt portion of the cylinder block and the split case. Therefore, if a pair of balancers are arranged on one side outside the engine body so that their directions are inclined with respect to the cylinder axis, one balancer is arranged on the cylinder block side and the other balancer is arranged on the other side. It will be arranged on the split case side.

(Problems to be Solved by the Invention) In the small internal combustion engine having the pair of balancers as described above, the balancer arranged on the split case side does not hinder the assembly work of the split case. Consideration was needed. Also, when other engine components such as a belt for transmitting the rotation of the crankshaft to the camshaft are attached to the engine body, the balancer arranged on the cylinder block side attaches the engine components close to the engine body. In addition, it was necessary to take care not to become an obstacle.

The present invention has been made to solve the above problems, and a purpose thereof is to dispose a pair of balancers on the outside of an engine body and to form the balancer in an oblique direction with respect to the cylinder axis direction of the engine. It is an object of the present invention to provide an engine provided with a balancer that does not become an obstacle when the split case is attached to the cylinder block even when the split case is installed.

The present invention also provides an engine provided with a balancer that allows the engine components to be arranged as close as possible to the engine body.

(Means for Solving Problems) Means for solving the above problems form a skirt portion of a cylinder block forming a part of a crankcase and a remaining portion of the crankcase assembled to the skirt portion. In an engine in which a crankcase is sandwiched and supported by a split case, a pair of balancers having a gear portion and a weight portion sandwiching the crankshaft on both sides in the radial direction of the crankshaft protruding outward from the cylinder block and the crankcase. The balancer is arranged obliquely with respect to the cylinder axis direction, and the weight portion protruding from the gear portion of the balancer is arranged on one side of the gear portion side surface and on the split case side. That is, the weight portion of the balancer provided is arranged on the side away from the engine side.

Further, the weight portion of the balancer arranged on the cylinder block side is arranged on the engine side.

Furthermore, the crankshaft is placed vertically.

(Operation) The weight portion of the pair of balancers having the gear portion and the weight portion is arranged on one side of the gear portion side surface, and the weight portion of the balancer arranged on the split case side is arranged on the side away from the engine side. Since it is installed, a space as large as possible can be secured between the balancer on the split case side and the split case,
The cylinder block of the split case can be easily attached.

Since the weight portion of the balancer arranged outside the cylinder block is arranged on the engine side, the engine component can be arranged outside the balancer on the cylinder block side as close to the engine as possible.

Furthermore, since the crankshaft is placed vertically, there is no interference with other components below the engine.

(Embodiment) A preferred embodiment of the present invention will be described with reference to an outboard motor as an example.
This will be described in detail 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 configuration including an engine cover 8, an oil case 9 for supporting the engine and auxiliary equipment, and a lower case 10 below which a propeller 11 and the like are attached.
The cases 9 and 10 are integrally connected by bolts and the like, and the upper part of the lower case 10 is supported from both sides by the extension mounts 12a of the arm member 12 extending from the swivel shaft 4 to prevent lateral contact of the outboard motor body 1 or the like. To prevent.

FIG. 2 shows the entire structure of the engine supported on the oil case 9. The engine is of a 2-cylinder 4-cycle type in which a crankshaft 24 is vertically supported, and includes a cylinder block 21, a cylinder head 22, and a division. An engine body 20 including a case 23 and pistons 25, 25, connecting rods 26, 26, a crankshaft 24, a camshaft 27, a rocker shaft 28, an intake / exhaust valve 29, ... 20 Externally mounted balance device 40, cam pulley 30, camshaft drive pulley 31, transmission belt 32, flywheel 33, starter pulley 34, recoil starter 35 and other engine bodies 20
It consists of the outer engine components.

Upper and lower cylinders 21a, 21a for accommodating pistons 25, 25 and connecting rods 26, 26 are formed in the cylinder block 21,
The skirt portion 21b forms a crankcase together with the split case 23, and the crankshaft 24 is held and housed so as to be sandwiched between the skirt portion 21b of the cylinder block 21 and the split case 23, and at the same time, the cylinder head.
A cam shaft 27, a rocker shaft 28, intake and exhaust valves 29, ... And, the crankshaft 24 partially protrudes outward from the crank portion 24a in the central portion and the cylinder block 21 and the like, and the lower shaft portion 24b,
24c and the crank part 24a has pistons 25,2
Four crank webs 24a-1, ... (Balance weights) that cancel the inertial force generated by the reciprocating motion of 5 are attached. Since the two pistons 25, 25 always move in the same direction, the four crank webs 24a-1, ...
Is also arranged at the same position in the circumferential direction of the crankshaft 24, and rotates to cancel the inertial force generated by the pistons 25, 25 and the like.

Further, the propeller 11 is connected to the lower shaft portion 24c of the crankshaft 24 via a rotation transmission means (not shown), and the upper shaft portion 24b is provided with a drive gear 41 of the balancer device 40, a camshaft drive pulley 31, and a flywheel 33. It is installed sequentially. Camshaft drive pulley 31 is the camshaft
27 Cam pulley 30 and transmission belt 32 mounted on the upper end
And transmits the rotation of the crankshaft 24 to the camshaft 27. A recoil starter 35 for manually starting the engine is connected to an upper portion of the flywheel 33 via a starter pulley 34.

Now, the balancer device 40 has the drive gear 4 as shown in FIG.
1, balancer 42, 42, balancer case 43 and case cover
The balancer case 43 is composed of 45 and the like, and the balancers 42, 42 and the drive gear 41 are housed in a balancer case 43 formed on the upper surfaces of the cylinder block 21 and the split case 23.
Two balancers 42, 42 are inserted through the gear portions 42c, 42c so as to sandwich the drive gear 41 on both sides of the drive gear 41 mounted on the upper shaft portion 24b of the crankshaft 24 extending upward through the three. I'm in mesh. That is, the balancer 42 is provided such that its weight portion 42a is offset to one side in the radial direction of the gear portion 42c, and the two gear portions 42c, 42c of the balancer 42, 42 mesh with each other so as to form a substantially flush plane with the drive gear 41. Further, the lower part of the balancer shaft 42b fixed through the center of the gear part 42c of the balancer 42 is pivotally supported by the balancer case 43 via a bearing 44, and the upper part of the balancer shaft 42b is driven by the balancers 42, 42 and the drive. A case cover 45 that covers the gear 41 is pivotally supported by a bearing 44, and the two balancers 4
A balancer device 40 including 2, 42 is attached to the Linder block 21 and the split case 23 as close as possible.

Further, the arrangement direction of the balances 42, 42 around the crankshaft 24 is inclined by a predetermined acute angle (θ) with respect to the cylinder axis (l) direction of the cylinder block 21, that is, the longitudinal direction of the engine as shown in FIG. The overall width of the engine is reduced to make the outboard motor as small and compact as possible.

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 balancer weight portions 42a, 42a are provided on the pistons 22, 22,
Since the directions are aligned at the bottom dead center, the inertial force generated by the reciprocating motion of the pistons 22, 22 becomes zero due to the cooperation of the crank webs 24a-1, ... And the balancer device 40, and the crank webs 24a The inertial forces in the directions orthogonal to the moving directions of the pistons 25, 25 due to -1, ... And the balancer weight portions 42a, 42a are zero because the rotation directions are opposite to each other, and the engine vibration is effectively suppressed.

In addition, since the acting surfaces of the inertial force between the balancer device 40 and the crank webs 24a-1 ,.
A corner force acts to rotate the crankshaft 24 up and down around a point in the longitudinal direction of 24, and this corner force is applied to the entire outboard motor body 1 via the oil case 9,
Since the outboard motor body 1 is supported by the swivel bracket 3 above and below the engine mount 6 and the extension mount 12a, the corner forces are absorbed and offset by these mounts 6 and 12a.

Now, the balancers 42, 42 should be as close as possible to the cylinder block 21 and the split case 23, and
Of the cylinder block (1) is obliquely arranged so as to have a predetermined acute angle (θ) and is mounted so that the engine periphery is as small and compact as possible. 21 and the other balancer 42 is arranged above the split case 23, and since the weight portion 42a of the balancer 42 projects from the side surface of the gear portion 42c, the weight portion 42a of the balancer 42 is disposed. May interfere with other engine components on the cylinder block 21, and the weight portion 42a of the balancer 42 may be
Becomes a hindrance, and problems such as improper assembly of the split case 23 are likely to occur.

More specifically, as shown in FIG. 4, the balancer 42A on the cylinder block 21 side is a transmission belt that connects the camshaft drive pulley 31 attached to the crankshaft 24 and the cam pulley 30 attached to the camshaft 27. 32 and the balancer on the split case 23 side
42B interferes with the split case 23, and when the split case 23 is attached to the cylinder block 21 via the bolts 50, ..., The bolts 50 ,.

Therefore, the weight portion 42a of the balancer 42 is provided closer to one side of the side surface of the gear portion 42c, and the weight portion 42a of the balancer 42A on the cylinder block 21 side is provided on the lower side of the gear portion 42c on the cylinder block 21 side. The weight part 42a of the balancer 42B is provided on the upper side of the gear part 42c above the split case 23 so as to avoid the above-mentioned problems. That is, since the weight portion 42a of the balancer 42A on the cylinder block 21 side is arranged so as to enter the cylinder block 21, the upper surface of the balancer 42A and the upper surface of the case cover 45 can be brought as close as possible to the cylinder block 21 side. The space for arranging the belt 32 can be secured, interference between the transmission belt 32 and the balancer device 40 can be sufficiently suppressed, and the weight portion 4 of the balancer 42B on the side of the split case 23 can be prevented.
Since 2a is provided upward so as to move away from the split case 23, a sufficient mounting space for the split case 23 to the cylinder block 21 can be secured, and the flange portion 23a of the split case 23 can be replaced with the flange portion 21b of the skirt portion 21b of the cylinder block 21. When it is attached to -1, as shown in FIG. 3, the mounting bolts 50, ... Can be inserted and tightened from the split case 23 side, and the split case 23 can be easily attached to the cylinder block 21.

Since the positions of the weight portions 42a, 42a of the balancers 42, 42 are slightly displaced in the longitudinal direction of the crankshaft 24, this balancer device 40 causes a new corner force on the crankshaft 24. Since the positional deviation between the weight portions 42a, 42a of the 42, 42 is small and the generated corner force is small, and the outboard motor body 1 is supported by the engine mount 6 and the extension mount 12a, the outboard motor body 1 is It is not affected by corner force.

As described above, the weight portions 42a, 42a of the balancers 42A, 42B are arranged closer to one side with respect to the gear portions 42c, 42c, and the protrusion portions of the balancer device 40 and the engine due to the protrusion of the weight portions 42a, 42a. Since the weight portions 42a, 42a of the balancers 42A, 42B are arranged so as to avoid interference with the main body 20 and other engine components as much as possible, the camshaft drive pulley 3
Engine components such as 1 and transmission belt 32
Since it can be disposed close to the engine, the size and size of the engine can be reduced, and the assembling work of the split case 23 can be facilitated to improve the assemblability and the maintainability of the engine body 20.

Reference numeral 60 in FIGS. 3 and 4 is a carburetor.

(Effects of the Invention) As is apparent from the above, according to the present invention, a pair of balancers having a gear portion and a weight portion are provided on both sides of the crankshaft protruding outward of the cylinder block and the split case, and the balancer In an engine in which this balancer is arranged obliquely with respect to the cylinder axis direction such that one is on the cylinder block side and the other is on the split case side, the weight portion protruding from the gear portion of the balancer is attached to the side surface of the gear portion. Since the weight part of the balancer on the split case side is arranged on the side away from the engine side and the space on the split case side of this balancer is set as large as possible, the split case is mounted on the cylinder block with bolts or the like. Even if it is attached to the, the work becomes easy.

Also, since the weight portion of the balancer on the cylinder block side is arranged on the engine side, and the mounting space is provided on the outer side of the balancer so that the engine components can be arranged as close to the engine as possible, the crankshaft is used. Engine components such as a cam pulley that drives the camshaft and a transmission belt can be arranged as close to the engine as possible, and the size around the engine can be reduced.

Furthermore, since the crankshaft is placed vertically, there is no interference with other components below the engine.

[Brief description of drawings]

FIG. 1 is an overall view of an outboard motor, FIG. 2 is a sectional side view of an engine arranged on an oil case, FIG. 3 is a front view of the engine showing a section of a balancer device, and FIG. FIG. 3 is a sectional view taken along the line AA of FIG. In the drawing, 20 is the engine body, 21 is the cylinder block,
Reference numeral 23 is a split case, 24 is a crankshaft, 42 is a balancer, 42a is a weight portion, 42c is a gear portion, and 1 is a cylinder axis.

Claims (3)

[Claims] 1. An engine in which a crankshaft is sandwiched between a skirt portion of a cylinder block forming a part of a crankcase and a split case assembled to the skirt and forming the remaining portion of the crankcase. A pair of balancers having a gear portion and a weight portion are arranged on both sides in the radial direction of the crankshaft projecting outward from the split case, and the arrangement direction of the balancers is arranged with respect to the cylinder axis direction. And the weight part projecting from the gear part of the balancer is arranged on one side of the gear part side surface, and the weight part of the balancer arranged on the split case side is arranged on the side away from the engine side. An engine equipped with a balancer. 2. The balancer engine according to claim 1, wherein the weight portion of the balancer disposed on the cylinder block side is disposed on the engine side. 3. The crankshaft according to claim 1, wherein the crankshaft is placed vertically.
An engine equipped with the balancer according to the item.