JP2540109B2 - Engine balancer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a balancer shaft for a reciprocating piston engine,
Particularly, it relates to a bearing structure of the shaft.

(Prior Art) In a reciprocating piston engine, due to a centrifugal force acting on an eccentric rotating part of a crankshaft or a crankpin of a crankshaft, an inertial force acting on a reciprocating part of a piston or a piston pin, or the like. There is a problem that vibration force is generated. For such an oscillating force, a balance weight is provided on the crank arm or the like to generate an oscillating force in the opposite direction to balance the two. For example, the most basic engine In the in-line 4-cylinder 4-cycle engine, which is the type, the secondary vibration force (the vibration frequency is twice the crankshaft rotation speed) due to the inertial force of the reciprocating motion is canceled only by the balance weight as described above. I can't.

With respect to this problem, an engine balancer device such as that disclosed in Japanese Patent Publication No. 57-44863 is conventionally known. This is a structure in which a balancer shaft having an unbalanced portion is arranged in parallel with the crankshaft so that the balancer shaft is driven by the crankshaft. In the case of a four-cylinder cylinder engine, the secondary excitation force due to the inertial force of the reciprocating motion portion as described above is offset by driving at a rotation speed twice the crankshaft rotation speed.

However, when an engine is equipped with this balancer shaft, it is necessary to dispose the unbalanced portion at the center in the longitudinal direction of the engine so that a new exciting force such as a pitching moment is not generated by the unbalanced portion. It is necessary to provide the bearing portion of the shaft at a highly rigid portion of the cylinder block, that is, at a partition wall portion between adjacent cylinders. Therefore, conventionally, regarding the structure of the unbalanced portion or the bearing portion, for example, in the case of an in-line four-cylinder engine, the structure shown in FIGS. 5A to 5C has been proposed or adopted. There is.

That is, as shown in FIG. 5 (a), the unbalanced portion 2 of the balancer shaft 1 is arranged on the side of the _second and third cylinders 3 ₂ and 3 ₃ located at the center in the longitudinal direction of the engine. first, second bearing portions at both ends of the unbalanced portion 2 4 _1, 4
₂ is provided, these bearing portions 4 _1, 4 ₂ first in the cylinder block, the second cylinder 3 _1, 3 between the _two partition walls 5 ₁ and the third, fourth cylinder 3
The partition wall 5 ₃ between ₃ and 3 _{4 is} pivotally supported. Further, an extension shaft portion 6 connected to a drive mechanism (not shown) is provided at one end side of the unbalanced portion 2, and a third bearing portion 4 ₃ is provided at an end portion of the shaft portion 6.
The provided, the bearing part 4 ₃ is a structure in which is journaled on the side 5 ₄ of the end portion of the cylinder block.

The one shown in FIG. 5 (b) is the same as that shown in FIG. 5 (a).
In addition to the above construction, a fourth bearing portion 4 ₄ ′ is provided in the intermediate portion of the unbalanced portion 2 ′, and this bearing portion 4 ₄ ′ is a partition wall between the _second and third cylinders 3 ₂ and 3 ₃ in the cylinder lock. 5 is a ₂ to was axially supported structure. That is, in this structure, the balancer shaft 1'is provided with the first and second bearing portions at both ends of the unbalanced portion.
4 ₁ ′, 4 ₂ ′ and the third bearing portion 4 ₃ ′ at the end of the extension shaft portion 6 ′
And a total of four bearing portions, the fourth bearing portion 4 ₄ ′, are provided.

Further, the one shown in FIG. 5 (c), first in FIG. 5 (b), the second bearing portion 4 ₁ ', 4 _2' which was abolished, in this structure, the balancer shaft 1 " Two bearing parts are provided, a first bearing part 4 ₁ ″ in the middle of the unbalanced part 2 ″ and a second bearing part 4 ₂ ″ at the end of the extension shaft part 6 ″.
This structure is that disclosed in the above publication.

(Problems to be Solved by the Invention) The bearing structures of the balancer shaft shown in FIGS. 5 (a) to 5 (c) have the following problems, respectively.

That is, in the structure shown in FIG. 5 (a), a first opposite ends of the unbalanced portion 2, since the second bearing portions 4 _1, 4 span between the _two becomes long, due to the centrifugal force to the unbalanced part 2 And a large bending moment acts on the partition walls 5 ₁ , 5 _{3 to which} the first and second bearing portions 4 ₁ , 4 ₂ and these are fitted.
The bearing hole (or the bearing metal attached to the hole) is easily abraded and seized easily.

Further, in the structure shown in FIG. 5 (b), since the fourth bearing portion 4 ₄ ′ is provided in the intermediate portion of the unbalanced portion 2 ′,
Although the above-mentioned adverse effects due to the bending moment acting on the unbalanced portion 2'are prevented or reduced, on the other hand, since the number of bearings is increased, the drive loss due to the sliding resistance in each bearing is increased. Will increase.

Furthermore, in the structure shown in FIG. 5 (c), the drive loss since the number of the bearing portion is small can be reduced, the Ann by "first bearing portion 4 ₁ provided in the middle portion of the" unbalanced part 2 The generation of a large bending moment due to the centrifugal force acting on the balance portion 2 ″ is suppressed, but in this structure, the portion 2a ″ on the side of the anti-extension shaft portion of the unbalance portion 2 ″ is cantilevered. The part 2a ″ swings around, and the first bearing part
4 ₁ "and this negative effects such as uneven wear in the mated bearing hole is of rather becomes remarkable.

(Means for Solving Problems) The present invention solves the above problems related to the balancer shaft of an engine, particularly the bearing structure of the shaft,
The purpose is to realize a balancer shaft with low drive loss and without uneven wear or seizure in the bearing.
In order to achieve this object, it is characterized by having the following configuration.

That is, the balancer shaft of the engine according to the present invention is
Place the unbalanced part in the center of the engine in the longitudinal direction,
Further, an extension shaft portion is connected to the drive mechanism by connecting one end side of the unbalanced portion to the drive mechanism, and a first bearing portion is provided at an end portion of the extension shaft portion, and an end of the unbalanced portion on the side opposite to the extension shaft portion. Second in the section
The bearing portion is provided with the third bearing portion in the middle of the unbalanced portion. And, between the first and third bearing portions and between the second and third bearing portions, the first and third bearings having the longer dimension between the bearing portions.
Weight distribution is performed so that the weight of the unbalanced portion is larger than that between the second and third bearing portions having shorter bearing portions.

(Operation) According to the above configuration, in the balancer shaft in which the unbalanced portion is arranged at the center in the longitudinal direction of the engine, the centrifugal force acting on the unbalanced portion by the third bearing portion provided in the intermediate portion of the unbalanced portion. The bending moment caused by the force is suppressed, and the occurrence of the bending moment due to whirling is also prevented because the unbalanced portion has no cantilevered portion. Moreover, since the number of bearings is three, the drive loss for driving the balancer shaft can be relatively small.

Further, according to the present invention, in particular, the weight of the unbalanced portion is calculated by comparing the weight of the first and third bearing portions with the first of the second and third bearing portions, which has the longer dimension between bearing portions, that is, the longer span. By distributing so that the distance between the third bearing portions is larger than that between the shorter second and third bearing portions, the following problems can be avoided.

That is, when the balancer shaft is rotated, particularly when it is rotated at a high speed, the shaft is bent by the action of the centrifugal force that accompanies the eccentric rotation of the unbalanced portion. In that case, the weight of the unbalanced portion is increased. If the two spans are evenly mixed, as shown in FIG. 6 in a simplified manner, the third bearing portion 7 ₃ provided at the intermediate portion of the balancer shaft 7 (unbalanced portion) will not be used on both sides thereof. Bearings
Even when the maximum deflection amounts in both spans between 7 ₁ and 7 ₂ are the same or the longer span is slightly larger, the deflection angles α ₁ , on both sides of the journal portion of the third bearing portion 7 ₃ , α ₂ is the deflection angle α on the long span side
₁ is smaller than the bending angle α ₂ on the shorter side. In that case, an oil clearance is provided between the bearing hole 8 ₃ and the journal portion in the third bearing portion 7 ₃ in order to generate a desired oil film. However, as described above, both deflection angles α ₁ , When α ₂ is different and the difference between the two exceeds a certain limit, a so-called one-side contact in which the journal portion and the bearing hole 8 ₃ abut or slide only on the short span side, as indicated by the symbol X at the same time. occurs, further uneven wear to abnormal wear would seizing occurs due to this the third bearing portion 7 _3. Also. Even when the rigidity of the journal portion is increased and the journal portion itself hardly bends, as shown in an exaggerated view of the main part in FIG. This causes various harmful effects such as wear.

However, according to the present invention, as described above, the weight of the unbalanced portion is distributed such that the longer span has a larger value. Therefore, the maximum deflection amount of the longer span is equal to the shorter deflection amount of the longer span. As a result, the deflection angles α ₁ and α ₂ shown in FIG. 6 are substantially equal to each other, and the problems such as one-side contact as described above are solved.

(Examples) Hereinafter, examples of the present invention will be described with reference to the drawings. still,
This embodiment relates to an in-line four-cylinder four-cycle engine, and deals with secondary vibration force due to inertial force of reciprocating motion parts such as pistons.

As shown in FIG. 1, the cylinder block of the engine 10
A partition 12 is provided between each adjacent cylinder in the 11,
A crankshaft 13 is arranged at the center of the skirt of the cylinder block 11 in the cylinder row direction. The crankshaft 13 is rotated by a main bearing 15 composed of the partition walls 12 and end walls (not shown) at both ends of the cylinder block, and bearing caps 14 attached to these walls. Although not shown, the piston of each cylinder is connected to a crank pin provided at an eccentric position via a crank arm via a connecting rod, which is freely supported. Further, the cylinder block 11 of the engine 10 is provided with a pair of left and right balancer shafts 30, 30. These balancer shafts 30, 30 are supported on the left and right sides of the crankshaft 13 in a slightly upper direction in parallel with and symmetrically with the shaft 13, and are supported by the crankshaft 13 via a drive mechanism (not shown). The shafts 13 are driven in opposite directions at a rotation speed twice that of the shaft 13.

Next, the configuration of the balancer shaft 30 and the shaft
The bearing structure of the shaft 30 will be described with reference to FIG.
Is an unbalanced part that is provided at an eccentric position with respect to the axis.
31 and an extension shaft portion 32 that is connected to one end of the unbalanced portion 31, and a first journal portion 33 is provided at the end portion of the extension shaft portion 32. A second journal portion 34 is provided at the end portion on the side of the anti-extension shaft portion, and a third journal portion 35 is provided at the intermediate portion of the unbalanced portion 31. The unbalanced section 31 is the engine
The first journal portion 33 is formed on the side wall of the second and third cylinders 10 ₂ and 10 ₃ in the central portion of the cylinder 10 in the longitudinal direction, and the first journal portion 33 is formed on the end wall 16 of the cylinder block 11 on the fourth cylinder 10 ₄ side. Second bearing hole 18 in which a second journal portion 34 is formed in a partition wall 12 ₁ between the _first and second cylinders 10 ₁ , 10
In addition, the third journal portion 35 is rotatably attached to the third bearing hole 19 formed in the partition wall 12 ₂ between the _second and third cylinders 10 ₂ and 10 ₃ via the bearing metals 20, 21 and 22, respectively. The first to third bearing portions I, II, and III are formed by fitting. A projecting end portion 36 projecting from the cylinder block end wall 16 is provided at an end portion of the balancer shaft 30 on the side of the first journal portion 33, and a drive mechanism between the shaft portion 36 and the crankshaft 13 is provided. The constituent gear 37 is fixed.

Here, the end wall 16 of the cylinder block 11 and the partition wall 12 ₁ ,
12 _second oil passage 24, 25, 26 derived from the oil gallery 23 shown in Figure 1 is provided in the above the bearings I, II, and first to third journal portion 33, 34 in the III The lubricating oil is supplied to the bearing sliding surfaces between the first to third bearing holes 17,18,19 (bearing metal 20,21,22) in which these journals are fitted. , The above oil passages 24, 2
The ends of the cylinder blocks 5 and 26 that open to the outer surface are closed by brand plugs 27 ... 27. Also, the above end wall
16 and the first to the partition wall 12 _2, the third bearing part I, but baffle 28 which covers the III is provided, these oil flows out the bearings I, from III is scattered in a cylinder block 11 This is to prevent it from becoming an oil mist.

However, the unbalanced portion 31 of the balancer shaft 30 has a weight distribution as shown below.

That is, the first and third journal portions of the balancer shaft 30
Of the space between 33 and 35 and the space between the second and third journal parts 34 and 35,
The axial length L _{1 of} the first unbalanced portion 31 ₁ located on the longer side of the span is made longer than the length L _{2 of the second} unbalanced portion 31 ₂ located on the shorter side of the span. In addition, since the cross-sectional areas of the first and second unbalanced portions 31 ₁ and 31 ₂ are made equal to each other, the first unbalanced portion 31 _{1 has} a larger cross-sectional area than the second unbalanced portion 31 _2. The weight is increased by a predetermined amount.

The outer peripheral surface of the third journal portion 35 and the bearing metal 22
An oil clearance is provided between the inner peripheral surface and the inner peripheral surface (the same applies to the first and second bearing portions I and II) so as to generate a desired oil film.

 Next, the operation of this embodiment will be described.

First, when the engine 10 is in operation, a secondary vibration force is generated by the inertial force acting on the reciprocating motion parts such as the piston and the piston pin. This vibration force is generated by the pair of left and right balancer shafts 30, 30. It is canceled as follows. That is, these balancer shafts 30, 30 are symmetrically arranged and have a rotational speed of 2 times that of the crankshaft 13.
Since they are driven in opposite directions at double speed, the resultant force of the centrifugal forces acting on the unbalanced parts 31, 31 of both balancer shafts 30, 30 fluctuates upward in a cycle that is half the rotation cycle of the crankshaft 13. It will be. Therefore, by setting the phases of the crankshaft 13 and both balancer shafts 30, 30 appropriately, the centrifugal force acting on the unbalanced parts 31, 31 when the exciting force due to the inertial force of the reciprocating part is upward. The resultant force can be generated downward, and the resultant force can be generated upward when the exciting force is downward, so that the exciting force is canceled. In that case, since both balancer shafts 30 and 30 are symmetrically arranged and driven in the opposite directions at the same speed, a new centrifugal force acting on the unbalanced portions 31 and 31 causes a new component due to the horizontal component force. Since no vibration force is generated and the unbalanced portions 31, 31 are arranged substantially in the center in the longitudinal direction of the engine 10, a centrifugal force acting on the unbalanced portions 31, 31 may generate a pitching moment. Instead, the vibration of the engine 10 is reduced in this way.

However, in this type of balancer shaft, a bending moment is generated due to the centrifugal force acting on the unbalanced portion, and this bending moment acts as a load on the bearing portion. An intermediate portion of the unbalanced portion 31 is formed by a third bearing portion III including a third journal portion 35 in the middle portion of 31 and a third bearing hole 19 (bearing metal 22) into which the journal portion 35 is fitted. Is supported, the bending moment acting on the unbalanced portion 31 is suppressed, and the loads acting on the first and second bearing portions I and II at both ends of the shaft 30 are reduced. Further, since the second bearing portion II is provided at the end portion of the unbalanced portion 31 on the side opposite to the extension shaft portion, the second and third journal portions 34, 3 of the unbalanced portion 31 are provided.
The part between 5 does not swing around and a large load acts on the third bearing part III.

In particular, in the balancer shaft 30, the first unbalanced portion 31 ₁ located between the first and third journal portions 33 and 35 and the second and third journal portions 34 and 35 having the longer span. However, since the weight is larger than that of the _second unbalanced portion 312 located in the shorter span,
When the shaft 30 rotates, especially at a high speed, the shaft 30 causes the first, second, and third bearing portions I, II, and II to be acted on by the centrifugal force generated by the eccentric rotation of the unbalanced portion 31.
When bent about I as a fulcrum, the journal portion 35 of the third bearing portion III is favorably supported by the bearing hole 19 or the bearing metal 22 as follows.

That is, when the balancer shaft 30 formed so that the span lengths differ from each other as described above, the first and second balancer shafts 30 are bent as described above with reference to FIGS. 6 and 7.
Assuming that the weights of the unbalanced parts 31 ₁ and 31 ₂ are evenly distributed, the deflection angles on both sides of the third journal part 35 are different (the first unbalanced part 31 ₁ side is the second unbalanced part). part 31 is an angle less bent than ₂ side), but would cause a situation where, according to the present invention, first towards the unbalance portion 31 ₁ is larger the weight by a predetermined amount as described above As a result, as shown by the solid line in FIG. 3, the bending angles θ ₁ of the first and second unbalance parts 31 ₁ and 32 ₂ ,
θ ₂ is the same or substantially the same. As a result, the third journal portion 35 is favorably held by the third bearing hole 19 or the bearing metal 22 while ensuring an oil clearance for producing a desired oil film on the peripheral surface portion thereof. As indicated by the chain line, since the journal portion 35 and the bearing metal 22 have different deflection angles from each other, there is a problem that the third bearing portion III is unevenly worn or seized. It is avoided.

In addition, in this embodiment, the first unbalance unit 31
By reducing the cross-sectional area over the entire length of the unbalanced portion 31 by an amount corresponding to the extension of ₁ , the weight of the entire unbalanced portion 31 is configured to be the required amount. Therefore, the load on each bearing portion I, II, III It is also possible to obtain the effect of improving the distributability of.

Incidentally, FIG. 4 also shows another embodiment of the second bearing portion,
In this embodiment, the bearing hole in the second bearing portion II '
18 'penetrates to the outside of the cylinder block 11', and a blind plug 29 'is attached to this penetrating portion.

By the way, according to such a bearing structure, the bearing hole 18 '
Since the closed space a is formed on the plug 29 'side of the cylinder block 11', the lubricating oil supplied from the oil passage 25 'between the journal portion 34' and the bearing metal 21 'is inside the cylinder block 11' on the opposite side. It will flow only to the space b side, and the lubricity for the portion of the bearing surface on the plug 29 'side will deteriorate. Therefore, in this embodiment, the journal portion 34 'of the balancer shaft 30' is provided with a communicating hole 38 'penetrating in the axial direction, and the space a is communicated with the internal space b of the cylinder block 11' by the hole 38 '. Thus, the lubricating oil supplied to the bearing portion is made to flow evenly to both the spaces a and b.

(Effects of the Invention) As described above, according to the present invention, in the engine in which the balancer shaft having the unbalanced portion is driven by the crankshaft to reduce the vibration, the number of the bearing portions is unnecessarily increased. In addition, it is possible to effectively suppress the bending moment caused by the centrifugal force acting on the unbalanced portion, and especially when the span lengths on both sides of the bearing portion provided in the middle of the unbalanced portion are different. However, the deflection angles of the unbalanced portions on both sides of the bearing portion are equalized, and the one-sided contact occurring on the bearing portion is prevented. As a result, significant wear and seizure of each bearing portion (particularly the bearing portion in the middle of the unbalanced portion) are prevented, and the durability of the bearing structure of this type of balancer shaft is improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional front view of an essential part of an engine showing an embodiment of the present invention, and FIG. 2 is a balancer shaft provided in the engine and an enlarged cross section of the essential part taken along line II-II in FIG. A plan view, FIG. 3 is an enlarged cross-sectional plan view of an essential part showing the operation of the above embodiment, FIG. 4 is a cross-sectional plan view of an essential part showing another embodiment of the bearing part, and FIGS. 5 (a) to 5 (c). FIGS. 6A and 6B are schematic diagrams showing a conventional bearing structure of a balancer shaft, and FIGS. 6 and 7 are schematic explanatory diagrams showing exaggerated conventional problems. 10 ... Engine, 13 ... Crank shaft, 30 ... Balancer shaft, 31 ... Unbalanced part, 32 ... Extension shaft part, I-III ... First to third bearing parts.

Claims (1)

(57) [Claims] 1. A balancer shaft for an engine, which is arranged parallel to a crankshaft and is driven by the crankshaft and has an unbalanced portion, wherein the unbalanced portion is arranged at a central portion in the longitudinal direction of the engine. In addition, an extension shaft portion is connected to the drive mechanism by connecting one end side of the unbalanced portion to the drive mechanism, and a first bearing portion is provided at an end portion of the extension shaft portion and an anti-extension shaft of the unbalanced portion. The second bearing portion is provided at the end portion on the side of the portion, and the third bearing portion is provided at the intermediate portion of the unbalanced portion.
Among the bearing portions and between the second and third bearing portions, the unbalanced portion of the unbalanced portion is larger than that of the first and third bearing portions, which have a longer dimension between the bearing portions, and which have a shorter dimension between the bearing portions. The balancer shaft of the engine, which is characterized by having a large weight.