JP2001140985A - Balance shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a balance shaft improved so as to miniaturize a counter weight part without deteriorating rigidity of a journal part. SOLUTION: In balance shafts 13L, 13R having eccentric weight parts (counter weight parts 19) and journal parts (first journal parts 18) arranged on the same axis so as to negate unbalance force of an engine, the journal part is provided with round contour parts 18a provided on axial both ends, a recessed part 22 provided on the opposite weight side in the axial central part, and a first rib 23 for connecting the round contour parts to each other on the flat surface on which the central axis of the balance shaft in the recessed part passes. Therefore, since material of the journal part is removed by forming a recessed part, the weight of the eccentric weight part can be reduced, and deterioration of rigidity of the journal part by removing material is compensated by the first rib.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balance shaft, and more particularly to a balance shaft provided with a counterweight for canceling the vibrating force generated by an engine piston.

[0002]

2. Description of the Related Art A balance shaft having a counterweight for canceling a secondary vibration generated by an engine piston is arranged below a crankshaft in an oil pan, and a chain / sprocket mechanism, a gear mechanism, and the like are arranged. A balancing device that transmits the rotation of a crankshaft to a balance shaft via the same is known, for example, from Japanese Utility Model Publication No. 5-39233.

[0003] In this balancing device, if the balance shaft is deflected, the vibration damping effect is diminished. Therefore, the rigidity of the journal for rotatably supporting the balance shaft is preferably as high as possible. Therefore, the journal portion of the balance shaft generally employs a solid structure with a perfect circular contour.

[0004]

However, when the journal portion is solid, the desired equivalent inertial mass is given when the journal portion is solid.
The counterweight must be enlarged.

[0005] The present invention has been devised to solve such problems of the prior art, and its main objects are as follows.
An object of the present invention is to provide an improved balance shaft so that the counterweight portion can be reduced in size without impairing the rigidity of the journal portion.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, an eccentric weight portion (counter weight portion) arranged on the same axis in order to cancel the unbalanced force of the engine. 19) and the journal (No. 1)
(13L · 1)
3R), the journal portion is provided with a perfect circular contour portion (18a) provided at both ends in the axial direction, a concave portion (22) provided on the anti-weight side at a central portion in the axial direction, and the balance shaft in the concave portion. And a first rib (23) connecting between the perfectly circular contour portions on a plane through which the central axis passes. According to this, since the journal portion is lightened by forming the concave portion, the weight of the eccentric weight portion can be reduced.
Supplemented by ribs.

According to a second aspect of the present invention, in addition to the above configuration, the second rib (21) extending on the same plane as the first rib and connecting to the journal portion is provided opposite to the portion where the eccentric weight portion is arranged. It is provided on the weight side. Thereby, the bending rigidity between the eccentric weight portion and the journal portion is further enhanced.

According to a third aspect, the radial outer end face of the first rib is recessed from the outer peripheral face of the perfect circular contour portion. Thereby, the inner peripheral surface of the bearing hole supporting the journal and the first
A gap is formed between the rib and the outer end surface of the rib, so that the lubricating oil in the concave portion flows easily, and the rotational resistance does not need to be increased.

According to a fourth aspect of the present invention, the radially projecting end of the first rib is rounded. Thereby, the stirring resistance of the oil is reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a reciprocating piston engine to which the present invention is applied. The engine E is an in-line four-cylinder engine in which a crankshaft 1 extends in a horizontal direction, and includes a head cover 2, a cylinder head 3, a cylinder block 4, a lower block 5, a balancing device 6, and an oil pan 7. .

The balancing device 6 reduces the secondary vibration of the engine E caused by the reciprocating motion of the piston. The balancing device 6 includes a lower surface 5 (crankshaft) of the lower block 5 in a state of being enclosed in the oil pan 7. 1). The balancing device 6 includes a large sprocket 8 fixed to a front end portion of the crankshaft 1 (hereinafter referred to as a crank pulley or a chain case side) and a left sprocket 8 (hereinafter referred to as a left-right direction toward the crank pulley or the chain case). A small sprocket 9 fixed to the front end of a balance shaft (to be described in detail later), and an endless link chain 10 bridged between the large and small sprockets 8.9.
, The rotation of the crankshaft 1 is transmitted.

The endless link chain 10 is rested by a chain guide 11 fixed on the left side of the center of the crankshaft on the front surface of the lower block 5 and at the right end of the small sprocket 9 on the front end surface of the balancing device 6. An appropriate tension is always applied by the fixed chain tensioner 12.

As shown in FIGS. 2 to 4, the balancing device 6
Is a pair of left and right balance shafts 13 having substantially the same shape.
L ・ 13R and these two balance shafts 13L ・ 13R
Upper and lower housings 14U and 14U which are vertically divided along a plane passing through the centers of the balance shafts 13L and 13R in order to support and accommodate the parallel housings in parallel with each other.
L.

The balance shafts 13L and 13R are connected to the helical gear 15 integrally connected to the balance shafts 13L and 13R.
L · 15R are linked to each other. Here, the driving force of the crankshaft 1 is transmitted to the left balance shaft 13L via the large sprocket 8, the endless link chain 10, and the small sprocket 9, as described above. Thus, the left balance shaft 13L is rotationally driven at twice the rotation speed of the crankshaft 1 and in the same direction as the crankshaft 1, and the right balance shaft 13R is rotated in the opposite direction by the meshing of the helical gears 15L and 15R. Driven.

As shown in FIGS. 2 and 3, portions of the upper housing 14U corresponding to the helical gears 15L and 15R correspond to both axial end surfaces of the helical gears 15L and 15R integrated with the balance shafts 13L and 13R. A contacting thrust receiving surface 16 is formed. This portion is open upward and both helical gears 1
A part of the outer periphery of the 5L / 15R is always exposed in the oil pan 7 and dripped from above, or lubricating oil scattered in the oil pan 7 enters the meshing portions of both helical gears 15L / 15R and the thrust receiving surface 16. , So that the part is sufficiently lubricated.

Each of the balance shafts 13L and 13R is formed integrally with a relatively large-diameter first journal portion 18 at its rear end and a relatively small-diameter second journal portion 17 at its front end. Also, each balance shaft 13L / 13R
On the rear end side, a counterweight portion 19 divided into two parts before and after the first journal portion 18 is integrally formed. The counterweight portion 19 has its center of gravity deviated radially outward from the center of rotation, and the diameter of the rotation locus is
The diameter is larger than the diameter of the first journal portion 18 (see FIG. 4).

The shaft portion 20 of the counterweight portion 19 has a small diameter in order to obtain the desired equivalent rotational mass after making the counterweight portion 19 as small as possible. Then, in order to compensate for the decrease in rigidity due to the reduced diameter and to prevent the shaft end from oscillating, the second ribs 21 connected to the axial end faces of the first journal portion 18 sandwich the first journal portion 18 from front and rear. The two shaft portions 20 are provided at portions extending over the entire length on the non-weight side. The second rib 21 has a tapered shape in which the height dimension decreases toward the shaft end in order to minimize the weight increase due to the provision of the rib and optimize the stress distribution.

Further, in order to shift the position of the center of gravity of the first journal portion 18 toward the counterweight portion 19 to further reduce the size of the counterweight portion 19, the counterweight side of the first journal portion 18 is provided with a first journal. The portion 18 is hollowed out except for the perfect circular contour portions 18a and 18b at both ends in the axial direction. Then, the meat is cut off and the two rounded contour portions 18a
The recesses 22 formed between the joints 18b are connected by first ribs 23 along a plane through which the central axis of the first journal portion 18 passes in order to compensate for a decrease in bending rigidity due to lightening (FIG. 5).
reference). The first rib 23 provided at the axial center of the first journal portion 18 and the second rib 21 provided at the shaft portion 20 of the counterweight portion 19 extend along the same plane. I have.

By doing so, the outer peripheral surface on the anti-weight side of the perfect circular contour portion 18a of the first journal portion 18 comes into contact with the inner peripheral surface of a metal bearing described later, so that the entire first journal portion 18 In spite of the small contact area with the bearing hole as described above, the oil film is not broken, which can contribute to the reduction of the rotational resistance.

The first rib 23 is provided with a through-hole 24 communicating between both surfaces of the first rib 23, and by facilitating the flow of the lubricating oil in the hollowed recess 22, the recess is formed. Lubricating oil is prevented from staying in the inside 22 to cause an increase in rotational resistance. This through hole 24
In order to minimize the decrease in rigidity of the first rib 23 due to the opening, the first rib 23 is provided on the shaft center side.

As a structure for facilitating the flow of the lubricating oil in the recessed portion 22 as described above, as shown in FIG. 6 and FIG. 18 may be recessed from the outer peripheral surface of the perfect circular contour portion 18a. According to this, a gap G is formed between the inner peripheral surface of the first bearing hole 26 that supports the journal portion 18 and the radially outer end surface of the first rib 23, and the gap G in the recess 22 is formed through the gap G. Lubricating oil can be made to flow. Further, in this case, if the radial protruding end of the first rib 23 is rounded, the oil stirring resistance is further reduced. In this case, it is possible to contribute to improvement in accuracy of lapping processing for finishing the outer peripheral surface of the journal portion 18 as compared with the case where the outer peripheral surface of the rib 23 is provided on the outer peripheral surface of the journal portion 18.

On the other hand, the first journal portion 1 of each balance shaft
8 is supported by a first bearing hole 26 having a split metal bearing formed by joining the upper and lower housings 14U and 14L to each other. The second journal portion 17 of each of the balance shafts 13L and 13R is supported by a second bearing hole 25 provided integrally with the front wall 25a of the lower housing 14L.

When the balance shafts 13L and 13R are accommodated in the housings 14U and 14L, the balance shafts 13L and 13L are placed with the counterweight portion 19 facing upward.
R is connected to the front wall 25 integral with the lower housing 14L.
a, each second journal portion 17 is supported in the second bearing hole 25 by being inserted into the second bearing hole 25 provided in the first bearing hole 25, and the first bearing hole 26 provided with a split metal bearing is provided.
, The first journal portions 18 of the balance shafts 13L and 13R are respectively mounted on the half portions of the lower housing 14L side, and further, in this state, the half portions of the first bearing holes 26 of the upper housing 14U are replaced with the respective balance shafts. 13L ・ 13R
The upper and lower housings 14U and 14L are joined to each other after being aligned with the first journal portion 18 of the first and second journal portions 18, so that the two balance shafts 13L and 13R
It will be rotatably accommodated in U.14L.

This eliminates the need to insert the counterweight portion 19 into the bearing hole.
8 and 19 can be made thinner in a sufficient range in terms of strength, so that rotational resistance is reduced and the balance shaft 13L
The reduction in size and weight of the housings 14U and 14L accommodating the 3Rs can be further promoted.

FIG. 8 shows a front end surface of the lower housing 14L.
As shown, a trochoid type lubricating oil pump 27 for pumping lubricating oil to each part of the engine is provided. The lubricating oil pump 27 includes an outer rotor 29 received in a pump housing 28 bolted to the front end surface of the lower housing 14L, and an inner rotor 30 connected to the front end of the right balance shaft 13R. The inner rotor 3 rotates integrally with the right balance shaft 13R.
0 cooperates with the outer rotor 29 and the lower housing 14L.
The lubricating oil in the oil pan 7 sucked from the oil strainer 31 attached to the bottom wall of the oil pan 7 through the suction pipe 32 integrally formed on the bottom wall of the lower housing 14L is installed in the lower block 5, the cylinder block 4, and the like. The pressure is fed to each part of the engine via a discharge oil passage 33 connected to the connected oil passage (not shown).

As shown in FIG. 3, the oil strainer 3
The one mounting boss 34 is connected to a bearing wall 26a provided with a half portion of the first bearing hole 26 at an intermediate portion in the front-rear direction of the lower housing 14L. Also, the lower housing 1
The suction pipe 32 integrally formed on the lower surface of the 4L has a front wall 25a.
Is terminated near to. The mounting boss 34 of the oil strainer 31 and the hollow suction pipe 32 are connected to the two balance shafts 13 on the lower surface of the lower housing 14L.
Between the front wall 25a and the bearing wall 26a, which are integrally formed so as to be continuously connected in series at a position between L and 13R and support the front and rear ends of the lower housing 14L, particularly the balance shafts 13L and 13R. Is connected to the mounting boss 34 of the oil strainer 31 and the suction pipe 32, which greatly contributes to enhancing the rigidity of the bearing walls 25a and 26a.

The suction pipe 32 has two balance shafts 1.
A part thereof is cut between the 3L and 13R (see FIG. 4). This reduces the amount of downward swelling. At the same time, the oil strainer 31 moves the lower housing 1
Since the lower housing 14L is directly mounted on the bottom wall of the 4L, the lower housing 14L is prevented from being unnecessarily large, and contributes to downsizing of the engine.

A pin-like projection 35 is provided upright on the bottom surface of the suction port provided with the oil strainer 31 made of a wire mesh in order to suppress inward deformation of the oil strainer 31. The projection 35 and the inner peripheral surface of the strainer mounting boss 34 are connected by a rib 36. This rib 36
Thereby, the rigidity of the strainer mounting boss 34, particularly the half portion of the bearing wall 26a, is further enhanced.

As shown in FIG. 4, the respective edges of the left and right side walls in contact with the divided surfaces of the upper housing 14U and the lower housing 14L are offset from each other in the radial direction of the balance shafts 13L and 13R. This allows
A gap 37 that opens upward is formed on a plane through which the centers of the balance shafts 13L and 13R pass. The lubricating oil OL collected at the bottom of the lower housing 14L is scraped up by the counterweight 19 with the rotation of the balance shafts 13L and 13R (in the direction of the arrow), and is discharged from the gap 37 to the outside of the housings 14U and 14L. You.

On the left and right side walls of the upper housing 14U,
An eave-shaped protrusion 38 extends in the axial direction. The eave-shaped protruding portion 38 faces the open surface of the gap 37 described above, and functions to prevent lubricating oil dropped from above from entering the housings 14U and 14L from the gap 37.

The eave-shaped protrusion 38 is provided in the manner shown in FIGS.
As shown in FIG. 5, a bolt B1 is formed over the entire length of the left and right side walls of the upper housing 14U in the front-rear direction and fastens the upper and lower housings 14U and 14L.
Helical gear 15L integrally connected to the balance shafts 13L and 13R.
A thrust bearing wall 16a provided with a thrust receiving surface 16 which abuts on 15R and regulates the axial position thereof is connected, thereby contributing to an increase in rigidity of the upper housing 14U.

The upper and lower housings 14U.
14L is fastened with three bolts B2 at the position of the bearing wall 26a, so that the bearing wall 26a, on which the radial acceleration due to the rotation of the counterweight portion 19 acts, is less likely to be loosened. Have been.

The eave-shaped protrusion 38 is extended to the left and right sides,
Providing an appropriate cross-sectional shape as shown in FIG. 11 can also serve as a baffle plate for preventing the oil surface in the oil pan from being roughened.

As shown in FIG. 12, the second journal unit 1
7 may be formed in the split surfaces of the upper and lower housings 14U and 14L.
According to this embodiment, the first and second journal sections 18.
7 can share a common dividing surface for each bearing, so that the accuracy of the axial center between the two bearings can be improved. In addition, as shown in FIGS. 13 and 14, the eave-shaped protrusion 38 extends to the support portion of the second journal portion 17 to connect the front wall 25a and the bearing wall 26a with the eave-shaped protrusion 38. Therefore, the rigidity of both walls 25a and 26a can be further increased.

The balancing device 6 configured as described above includes:
As shown in FIG. 4, a through bolt B3 inserted from below
Is fastened to the lower block 5.

[0037]

As is apparent from the above description, according to the present invention, the axially opposite ends of the journal portion adjacent to the eccentric weight portion for canceling the vibrating force generated by the piston of the engine are provided. Since the lightening portion is formed and the first rib for connecting between both ends in the axial direction is provided in the lightening portion, the eccentric weight portion is reduced in weight with the weight reduction of the journal portion. In addition, since the first rib compensates for the decrease in rigidity due to the reduction in thickness, a large effect can be obtained in achieving both high compactness and high rigidity of the balance shaft.

In particular, if the second rib extending on the same plane as the first rib and connected to the journal is provided on the opposite side of the portion where the eccentric weight is placed,
Further enhancement of the bending stiffness between the eccentric weight and the journal may be contemplated.

In addition to this, if the radial outer end surface of the first rib is recessed from the outer peripheral surface of the perfect circular contour portion, the inner peripheral surface of the bearing hole supporting the journal portion and the first rib can be formed. Since a gap is formed between the outer end face and the outer end face, the lubricating oil in the concave portion can easily flow, and the rotational resistance does not need to be increased.
If the radial protrusions of the ribs are rounded, the oil stirring resistance can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view in which only a main part of an engine to which the present invention is applied is cut away.

FIG. 2 is a partial vertical sectional view of the inside of the oil pan cut along the axis of a left balance shaft.

FIG. 3 is a longitudinal sectional view cut along an axis of a right balance shaft of the balancing device.

FIG. 4 is a longitudinal sectional view of an essential part taken along line IV-IV in FIG.

FIG. 5 is a cross-sectional view of a plane orthogonal to an axis of a first journal portion on a balance shaft.

FIG. 6 is a side view of a balance shaft showing another form of the first journal part, partially cut away;

FIG. 7 is a perspective view of a main part of the balance shaft shown in FIG. 6;

FIG. 8 is a longitudinal sectional view of an essential part along the line VIII-VIII in FIG. 3;

FIG. 9 is a right side view of the balancing device.

FIG. 10 is a top view of the balancing device.

FIG. 11 is a partial longitudinal sectional view showing another form of the eave-shaped protrusion.

FIG. 12 is a partial longitudinal sectional view showing another form of the second journal portion.

FIG. 13 is a right side view showing another embodiment of the balancing device.

FIG. 14 is a top view showing another embodiment of the balancing device.

[Explanation of symbols]

 13L / 13R Balance shaft 18 Journal part 18a True circular contour part 19 Counter weight part 20 Shaft part 21 Second rib 22 Depression 23 First rib

Claims (4)

[Claims] 1. A balance shaft comprising an eccentric weight portion and a journal portion arranged on the same axis to cancel an unbalance force of an engine, wherein the journal portions are provided at both ends in the axial direction. A first round connecting portion between the perfect circular contour portions, a concave portion provided on the anti-weight side at the axial center portion, and a plane passing through the central axis of the balance shaft in the concave portion; A balance shaft having ribs. 2. A second rib extending on the same plane as the first rib and connected to the journal portion is provided on a non-weight side of a portion where the eccentric weight portion is arranged. The balance shaft according to claim 1, wherein 3. The balance shaft according to claim 1, wherein a radially outer end surface of the first rib is recessed from an outer peripheral surface of the perfect circular contour portion. 4. The balance shaft according to claim 1, wherein a radially projecting end of said first rib is rounded.