Balancer device

Abstract

Provided is a balancer device including: a pair of balancer shafts 12, 13 respectively having first and second counter weights 31, 32 and first and second counter weights 33, 34 for generating an excitation force by a rotational force transmitted from an internal combustion engine; and a balancer housing 11 having a housing chamber 11a in which the pair of balancer shafts are rotatably housed. The balancer housing has a lower housing 16 and an upper housing 17. On opposed inner surfaces of both side walls 20, 20 of at least the upper housing, projection parts 38 are provided, of which tip parts 28a project toward recessed parts 31a, 32a provided in recessed shapes in the radial direction of the counter weights 31, 32. With this configuration, it is possible to suppress an increase in size while increasing the rigidity of the housing of the balancer device.

Description

Balancer device

[0001] The present invention relates to a balancer device that reduces secondary vibrations in an internal combustion engine.

[0002] A conventional balancer device for an internal combustion engine is described in the following Patent Document 1. Outlined, the balancer device includes a housing attached to the lower part of the crankcase of the internal combustion engine and housed in an oil pan, the housing being made up of an upper housing and a lower housing, a drive-side balancer shaft rotatably housed and supported via a plain bearing in an accommodation chamber inside the housing and to which rotational force is transmitted from the crankshaft, and a driven-side balancer shaft rotatably housed and supported via a plain bearing in the accommodation chamber and to which rotational force is transmitted from the drive-side balancer shaft.

[0003] The drive-side balancer shaft receives rotational force from the crankshaft via a drive chain wound around a drive-side sprocket at the front end thereof, and is provided with a pair of counterweights.

[0004] The driven balancer shaft receives rotational force from a drive gear provided on the driving balancer shaft via a driven gear. The driven balancer shaft also has a pair of counterweights integrally provided thereon.

[0005] When the engine starts and the crankshaft is driven to rotate, the drive-side balancer shaft is driven to rotate at twice the rotational speed of the crankshaft via the drive-side sprocket of the drive-side balancer shaft wound by the drive chain, and as the drive-side gear rotates, the driven-side gear meshing with it rotates in the opposite direction, driving the driven-side balancer shaft to rotate in the opposite direction to the drive-side balancer shaft.This rotation of the counterweights effectively suppresses secondary vibrations of the internal combustion engine.

[0006] Japanese Patent Application Publication No. 2013-154282

[0007] In the balancer device, the housing must be strong enough to withstand vibrations caused by the rotation of the counterweights. Therefore, in the conventional balancer device, both side walls of the upper housing and the lower housing are formed straight along the axial direction of each balancer shaft, and therefore, in order to ensure rigidity, the overall thickness of both side walls of each housing is increased to increase rigidity.

[0008] However, if the thickness of each side wall of the upper housing and the lower housing is made large, the side walls of both housings will protrude outward, which will not only force the housings to become larger, i.e., the entire balancer device to become larger, but may also result in an increase in weight.

[0009] In particular, when the housing is made of aluminum alloy, the thickness of the walls must be made even larger to ensure the rigidity of both side walls compared to when the housing is made of cast iron, which makes the device even larger in size.

[0010] The present invention has been devised in view of the technical problems with the conventional balancer devices, and has as its object to provide a balancer device that can increase the rigidity of the housing while suppressing an increase in size.

[0011] The invention described in claim 1 comprises a pair of balancer shafts, each having a counterweight that generates a vibratory force by the rotational force transmitted from an internal combustion engine, and a balancer housing having an accommodation chamber in which the pair of balancer shafts are rotatably accommodated, wherein the balancer housing has protrusions, the tip ends of which protrude toward the counterweights, on the opposing inner surfaces of both side walls that are arranged along the axial direction of the balancer shafts and that form the accommodation chamber.

[0012] According to this invention, it is possible to prevent the balancer device from becoming large while ensuring strength by increasing the rigidity of the housing.

[0013] Fig. 5 is a front view of a main part showing a state in which an embodiment of a balancer device according to the present invention is attached to an internal combustion engine. Fig. 6 is a plan view of the balancer device according to this embodiment. Fig. 7 is a side view of the balancer device. Fig. 8 is a perspective view of an upper housing used in this embodiment, viewed from the bottom side. Fig. 9 is a bottom view of the upper housing. Fig. 10 is a cross-sectional view taken along line A-A in Fig. 5. Fig. 11 is a perspective view of a lower housing used in this embodiment, viewed from above. Fig. 12 is a plan view of the lower housing. Fig. 13 is a cross-sectional view taken along line B-B in Fig. 8.

[0014] Hereinafter, an embodiment of a balancer device according to the present invention applied to, for example, an in-line four-cylinder internal combustion engine of an automobile will be described with reference to the drawings. [First Embodiment] Fig. 1 is a front view of a main part showing an embodiment of a balancer device according to the present invention attached to an internal combustion engine, Fig. 2 is a plan view of the balancer device, and Fig. 3 is a side view of the balancer device.

[0015] As shown in FIG. 1, a bearing cap 4 having a bearing portion for supporting a crankshaft 3 is fixed to the lower part of a cylinder block 2 of an internal combustion engine 1, and an oil pan (not shown) which is divided into upper and lower parts and which stores engine oil therein is attached to the lower part of the bearing cap 4.

[0016] The crankshaft 3 is rotatably supported by a plurality of bearings, including bearing caps 4, which are connected to the lower part of the cylinder block 2 by bearing bolts, and a crank sprocket 6 is attached to the shaft end 3a integrally formed at the front end.

[0017] The crank sprocket 6 is joined by shrink fitting to the shaft end 3a of the crankshaft 3 via an insertion hole 6a formed in the center.

[0018] A balancer device 10 for suppressing secondary vibrations of the engine is housed and disposed in a space surrounded by the lower part of the cylinder block 2, the bearing cap 4, and the oil pan.

[0019] 4 is a perspective view of the upper housing used in this embodiment as seen from the bottom side, FIG. 5 is a bottom view of the upper housing, FIG. 6 is a cross-sectional view taken along line A-A in FIG. 5, FIG. 7 is a perspective view of the lower housing used in this embodiment as seen from above, FIG. 8 is a plan view of the lower housing, and FIG. 9 is a cross-sectional view taken along line B-B in FIG. 8.

[0020] As shown in Figures 1 to 9, this balancer device 10 comprises a balancer housing 11 fixed to the underside of the cylinder block 2, a drive side balancer shaft 12 and a driven side balancer shaft 13 rotatably supported in an accommodation chamber 11a inside the balancer housing 11 and arranged parallel to each other in the longitudinal direction of the engine, and a helical drive side gear 14 and a driven side gear 15 respectively provided near the axial front ends of the balancer shafts 12 and 13 and having teeth that mesh with each other.

[0021] 1 and 3, the balancer housing 11 is composed of a lower housing 16 on the oil pan side and an upper housing 17 located above the lower housing 16. Both housings 16, 17 are made of aluminum to reduce weight, and are fastened together from above and below by a plurality of fastening bolts 18.

[0022] 4 to 8, the lower housing 16 and the upper housing 17 have side walls 19, 19, 20, 20 respectively provided along the axial direction of the balancer shafts 12, 13, and front end walls 21 provided at both longitudinal ends of each of the side walls 19 to 20. Each of the side walls 19, 19, 20, 20 is basically formed almost straight, with mating surfaces (abutment surfaces) facing each other from above and below formed as flat surfaces, and three parallel, front to rear cross beam deck portions 23, 23, 23 for bearings that are connected across each of the side walls 19 to 20 are integrally provided.

[0023] 7 and 8, an oil groove 24 is formed in the longitudinal direction on the flat upper surface of one side wall 19 (19a) of the lower housing 16, for supplying lubricating oil to each of the half-split bearing portions 23a formed in each cross beam deck portion 23. An oil passage is formed in this oil groove 24 by abutting the flat lower surface of one side wall 20 (20a) of the upper housing 17 shown in FIG. 4 against the upper surface of one side wall 19 (19a) so as to cover it. In other words, the flat lower surface of one side wall 20a of the upper housing 17 functions as a sealing surface that seals the oil groove 24 formed in the upper surface of one side wall 19a of the lower housing 16.

[0024] 2, 4, and 5, the upper housing 17 has a plurality of (eight in this embodiment) fixing bosses 25 integrally formed on the outer sides of each of the side walls 20. Each fixing boss 25 is formed in a substantially cylindrical shape and has an insertion hole 25a formed therein along the vertical direction, through which a bolt (not shown) is inserted to attach and secure the balancer housing 11 to the lower part of the cylinder block 2. Furthermore, each of the six fixing bosses 25, excluding the two fixing bosses 25 on the front end wall 21 side, has connecting portions 25b, 25b on both sides that are substantially triangular in shape when viewed from the plane where they are connected to the side walls 20.

[0025] The upper housing 17 is formed as eight flat mounting surfaces, with the upper surfaces of the fixing bosses 25 abutting against the lower surface of the cylinder block 2 .

[0026] The drive-side balancer shaft 12 has a helical-tooth idler driven gear 26 mounted on its tip shaft portion 12a, which protrudes forward from the balancer housing 11. As shown in FIG. 2, this idler driven gear 26 meshes with an idler gear 27 mounted on the outer periphery of an idler shaft 35, which will be described later. The idler driven gear 26 transmits rotational force from the crankshaft 3 to the drive-side balancer shaft 12 via a drive chain 28 wound between an idler sprocket 36, which is integrally mounted on the front end of the idler gear 27, and the crank sprocket 6. This causes the balancer shafts 12 and 13 to rotate in opposite directions via the drive-side gear 14 and the driven-side gear 15. The balancer shafts 12 and 13 are set to rotate twice per rotation of the crankshaft 3. The tension of the drive chain 28 is adjusted by a chain tensioner 29, as shown in FIG. 1.

[0027] The journal portion 12e of the tip shaft portion 12a is rotatably supported by a half-split bearing portion 30 formed between the lower housing 16 and the upper housing 17, and this bearing portion 30 is fixed vertically by a pair of fastening bolts 18 that fasten the lower housing 16 and the upper housing 17 together.

[0028] As shown in Figures 4 and 5, the drive-side balancer shaft 12 has three cylindrical journal surfaces 12b, 12c, and 12d formed on the front, central, and rear axial ends, respectively, and these three journal surfaces 12b to 12d are rotatably supported by two plain bearings provided in first to third bearing grooves formed in the first to third cross beam deck portions 23 of the lower housing 16 and the upper housing 17, respectively.

[0029] As shown in Figures 4 to 6, the drive-side balancer shaft 12 is integrally provided with two semicircular counterweights, first and second counterweights 31, 32, at symmetrical positions on either side of the second cross beam deck section 23. Each of these counterweights 31, 32 has a recess 31a, 32a formed at one radial end, and each recess 31a, 32a is cut out to have a substantially V-shaped cross section, with the central portions 31b, 32b being the deepest recess. Furthermore, as shown in Figures 8 and 9, each of the other radial end faces 31c, 32c of each of the counterweights 31, 32 is cut out along the axial direction to form a flat shape, and the counterweights are set to have the same weight.

[0030] The drive-side gear 14 is fixed to the drive-side balancer shaft 12 by press-fitting or the like, and is sandwiched between a thrust wall (not shown) so that its movement in the axial direction is restricted.

[0031] As shown in Figures 2 to 5, the driven-side balancer shaft 13 has an axial length shorter than that of the drive-side balancer shaft 12, and journal surfaces 13b, 13c, and 13d formed at three axial locations are rotatably supported via plain bearings in two semicircular arc-shaped bearing grooves formed in each cross beam deck portion 23.

[0032] 2 to 8, the driven-side balancer shaft 13 is integrally provided with two semicircular arc-shaped first and second counterweights 33, 34 at symmetrical positions in the front and rear with the central second cross beam deck portion 23 in between. These counterweights 33, 34 have the same shape as the first and second counterweights 31, 32 of the drive-side balancer shaft 12, and have recesses 33a, 34a cut out in a substantially V-shaped cross section at one radial end, with central portions 33b, 34b being the deepest recess. Furthermore, the other radial end faces 33c, 34c of each counterweight 33, 34 are cut out along the axial direction to form a flat shape, and are set to have the same weight.

[0033] The recesses 31a to 34a provided in the counterweights 31 to 34 on the driving and driven sides are designed to allow the clamping portion, which is part of the crankshaft 3, to enter during rotation, thereby enabling the balancer device to be brought closer to the internal combustion engine from above and below.

[0034] The driven gear 15 is fixed to the driven balancer shaft 13 by press fitting or the like, and, like the drive gear 14, is sandwiched within a groove formed in the lower housing 16, i.e., between opposing thrust walls of the groove, so that its axial movement is restricted.

[0035] 1 and 2, the upper housing 17 has an idler shaft 35 mounted on a fixing boss 25 on the outer side of the front end. The idler shaft 35 is fixed to the fixing boss 25 via a flange 35a by the fastening force of a washer nut 37 that is threaded onto a male thread (not shown), and rotatably supports an idler gear 27 and an idler sprocket 36 that is integral with the idler gear 27 on its outer periphery.

[0036] 4 to 6, the upper housing 17 has four protrusions 38 formed integrally on the opposing inner surfaces of both side walls 20, 20 at positions corresponding to the positions where the four counterweights 31 to 34 are formed. Each of these protrusions 38 is formed in a substantially triangular convex shape when viewed from above, has a solid interior, and is formed in a padded shape, with each tip 38a projecting into the recesses 31a to 34a of each of the counterweights 31 to 34 and positioned so as to overlap with each of the counterweights 31 to 34 in the axial direction.

[0037] Each protrusion 38 is disposed between the two adjacent fixing bosses 25 and is joined to the fixing bosses 25 via the connecting portions 25b, 25b across the side walls 20. In other words, each protrusion 38 is connected to the fixing bosses 25 via the connecting portions 25b, 25b in a substantially V-shape in plan view.

[0038] 7 to 9, the lower housing 16 has four protruding wall portions 39 integrally formed on the opposing inner surfaces of both side walls 19, 19 at the same vertical positions corresponding to the protruding portions 38 of the upper housing 17. Each of these protruding wall portions 39 is formed in a substantially triangular shape in plan view, like each of the protruding portions 38. However, unlike each of the protruding portions 38, each of the protruding wall portions 39 is not solid, but is formed with a hollow interior by partially deforming the both side walls 19, 19 bulging inward. Each of the protruding wall portions 39 is positioned so that its tip end 39a protrudes into the recessed portions 31a to 34a of each of the counterweights 31 to 34 and overlaps with each of the counterweights 31 to 34 in the axial direction.

[0039] [Operation and Effect of the Present Embodiment] Therefore, according to this balancer device 10, when the engine is started and the crankshaft 3 is driven to rotate, the drive-side balancer shaft 12 rotates at twice the speed of the crankshaft 3 via the crank sprocket 6, drive chain 28, idler gear 27, and idler driven gear 26. As a result, the driven-side balancer shaft 13 rotates at the same speed in the opposite direction to the drive-side balancer shaft 12 via the meshing rotation transmission of the drive-side gear 14 and driven-side gear 15. As a result, the counterweights 31, 32, 33, and 34 also rotate in opposite directions to each other, canceling out the left and right centrifugal forces of the balancer shafts 12 and 13 themselves.

[0040] At this time, the balancer housing 11 prevents interference between the oil remaining in the oil pan and the balancer shafts 12, 13, and receives and simultaneously transmits the vibratory force generated when the balancer shafts 12, 13 rotate. In this way, the counterweights 31 to 34 rotate with the rotation of the balancer shafts 12, 13, transmitting the vibratory force to the internal combustion engine 1, thereby suppressing secondary vibration.

[0041] In this embodiment, the four protrusions 38, each with a tip 38a protruding toward the recesses 31a, 32a of the counterweights 31, 32, are provided on the opposing inner surfaces of each of the side walls 20, 20 of the upper housing 17, thereby increasing the rigidity and strength of each of the side walls 20, 20. Therefore, the overall rigidity of the balancer housing 11 is improved, and the strength is sufficiently increased.

[0042] Furthermore, in this embodiment, four convex wall portions 39 are provided on the inner surfaces of both side walls 19, 19 of the lower housing 16, with each tip portion 39a protruding toward each recess 33a, 34a of each counterweight 33, 34, thereby increasing the rigidity of each side wall 19, 19 and increasing its strength.

[0043] Therefore, the synergistic effect of the protrusions 38 and the convex wall portions 39 further improves the rigidity of the balancer housing 11, further increasing the strength.

[0044] Furthermore, since each of the protrusions 38 and each of the convex wall portions 39 is formed to protrude so as to fit into the recesses 31a to 34a formed in each of the counterweights 31 to 34, the dead space between each of the housings 16, 17 and each of the counterweights 31 to 34 can be effectively utilized to shorten the widthwise length of the balancer housing 11, thereby making it possible to prevent the overall size from increasing.

[0045] That is, in this embodiment, it is possible to improve the overall rigidity of the balancer housing 11 while suppressing an increase in size.

[0046] However, if the axial distance between the pair of balancer shafts 12, 13 is long, the distance between the side walls 19, 19 of the lower housing 16 of the balancer housing 11 and the side walls 20, 20 of the upper housing 17 also becomes large, and therefore the side walls 19, 19 and 20, 20 become easily deformed when the upper housing 17 and the lower housing 16 are joined by the fastening bolts 18. This deformation generates a gap between the upper housing 17 and the lower housing 16, making it easier for oil to leak from the oil passage formed between the two housings 16, 17 via the oil groove 24.

[0047] However, in this embodiment, the protrusions 38 and the convex wall portions 39 increase the rigidity and strength of the side walls 19-20 of each housing 16, 17, thereby suppressing deformation of the side walls 19-20 when the upper housing 17 and the lower housing 16 are joined with the fastening bolts 18, thereby suppressing oil leakage from the oil passages.

[0048] In particular, each of the protrusions 38 and each of the convex wall portions 39 are formed in a substantially triangular convex shape in plan view, which effectively increases the rigidity of each of the housings 16, 17. As a result, deformation of each of the housings 16, 17 can be sufficiently suppressed.

[0049] Furthermore, each of the protrusions 38 of the upper housing 17 is formed as a solid mound inside, which increases the rigidity of the upper housing 17, which requires high rigidity particularly when coupled with the internal combustion engine 1. Meanwhile, each of the convex wall portions 39 of the lower housing 16 functions as a rib, as both side walls 19, 19 are deformed to bulge inward, ensuring rigidity while suppressing an increase in weight.

[0050] Furthermore, the two side walls 20, 20 of the upper housing 17 are connected by a so-called truss structure using the six fixing bosses 25, the connecting portions 25b, and the protrusions 38, which further increases the rigidity of the upper housing 17. As a result, deformation of the upper housing 17 can be more effectively suppressed.

[0051] As described above, by allowing the crank pin side of the rotating crankshaft 3 to enter into each of the recesses 31a to 34a formed on the outer circumferential surface of each of the counterweights 31 to 34, it becomes possible to move the balancer device 10 closer to the internal combustion engine. This makes it possible to reduce the vertical height of the entire internal combustion engine 1 including the balancer device 10, thereby enabling the vehicle to be lowered.

[0052] REFERENCE SIGNS LIST 1 internal combustion engine, 2 cylinder block, 3 crankshaft, 4 bearing cap, 6 crank sprocket, 10 balancer device, 11 balancer housing, 11a accommodation chamber, 12 drive side balancer shaft, 13 driven side balancer shaft, 13a, 13b first and second counterweights, 14 drive side gear, 15 driven side gear, 16 lower housing, 17 upper housing, 19, 19 ...Both side walls on the lower housing side, 20.20... Both side walls on the upper housing side, 24... Oil groove, 25... Fixing boss portion, 25b... Connection portion, 31.32... First and second counterweights on the driving side, 31a.32a... Recesses, 31b.32b... Central portion, 33,34... First and second counterweights on the driven side, 33a.34a... Recesses, 33a.34a... Central portion, 38... Protrusion, 38a... Tip portion, 39... Convex wall portion, 39a... Tip portion.

Claims

1. A balancer device comprising: a pair of balancer shafts, each having a counterweight that generates a vibratory force by the rotational force transmitted from an internal combustion engine; and a balancer housing having an accommodation chamber in which the pair of balancer shafts are rotatably accommodated, wherein the balancer housing is provided with protrusions, the tips of which protrude toward the counterweights, on the inner surfaces of both side walls that are arranged along the axial direction of the balancer shafts and that constitute the accommodation chamber.

2. A balancer device as described in claim 1, characterized in that a recess recessed radially inward is formed on the outer peripheral surface of the counterweight, and the protrusion is formed in a convex shape facing toward the inside of the recess.

3. A balancer device as described in claim 2, characterized in that the protrusion is formed to protrude into the recess of the counterweight and is positioned so as to overlap the counterweight in the axial direction.

4. A balancer device according to claim 1, wherein the protrusion is formed in a convex shape that is approximately triangular in plan view.

5. A balancer device according to claim 1, characterized in that a plurality of fixing bosses for fixing the balancer housing to the internal combustion engine with bolts are provided intermittently in the longitudinal direction of the balancer housing on the outer surfaces of both side walls, and the protrusion is disposed between two adjacent fixing bosses.

6. A balancer device as described in claim 5, wherein each of the cylindrical fixing boss portions has a connecting portion on each side thereof that connects to the balancer housing, and the two adjacent fixing boss portions and the protrusions located between the two fixing boss portions are connected via each connecting portion in a substantially V-shape in plan view.

7. A balancer device according to claim 2, characterized in that the recess formed on the outer peripheral surface of the counterweight is formed in a substantially V-shaped vertical cross section with the maximum recession occurring at approximately the center position in the axial direction, and that a portion of the crankshaft of the internal combustion engine is able to fit into the recess while it is rotating.

8. A balancer device according to claim 1, wherein the balancer housing is composed of an upper housing arranged below the internal combustion engine and a lower housing connected to the lower part of the upper housing, the upper housing has the protrusions on the opposing inner surfaces of both side walls, and the lower housing has convex side walls that protrude towards the counterweight at positions on the opposing inner surfaces of both side walls that correspond to the protrusions on the upper housing.

9. A balancer device according to claim 8, wherein the protrusion is formed with a solid built-up interior, and the convex side walls are formed with a hollow interior by deforming both side walls of the lower housing to bulge inward.

10. A balancer device according to claim 8, wherein an oil passage is formed between the upper and lower abutting surfaces of the upper and lower housings.

11. A balancer device as described in claim 10, wherein an oil groove forming the oil passage is formed on the contact surface of the lower housing, the contact surface of the upper housing is formed as a flat sealing surface that covers the oil groove, and the protrusions of the upper housing and each of the fixing bosses are connected across the sealing surface, and a truss structure is formed by the both side walls, the protrusions, and both fixing bosses.