JP2001336610A - Gear device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear device having expected elasticity and durability with a simple and compact structure. SOLUTION: Cushion gears (shock absorbing gears) 9a and 9b meashing both with a driven gear (a main gear) 5 and a drive gear a mating gear) and the driven gear 5 are fixed in the shaft rotating direction. A tooth surface of the cushion gears 9a and 9b is projected to the tooth groove side more than a tooth surface of the driven gear 5. The height of a tooth root of the cushion gears 9a and 9b is set longer than the height of a tooth root of the main gear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear device suitably applied to, for example, a driving force transmission system of a vehicular internal combustion engine, and more particularly to a vibration device and a rattling noise caused by backlash between gears meshing with each other. Related to prevention technology.

[0002]

2. Description of the Related Art As is well known, in a gear device that meshes with each other, the back surface of the tooth of one gear and the gear next to the mating gear do not interfere with the meshing due to dimensional errors, assembly errors or thermal expansion. A predetermined gap, that is, a backlash, is set between the tooth and the other tooth. In order to prevent vibration and rattle (noise) caused by such backlash,
Scissor gears are known. To briefly explain the structure of such a scissors gear, a buffer gear adjacent to the main gear is configured to mesh with a mating gear together with the main gear, and the phase of the two is shifted between the main gear and the buffer gear. A spring element, such as a spring, which keeps the spring in a closed state is interposed.

In the gear device described in Japanese Patent Application Laid-Open No. H11-153211, the phase with respect to the main gear is shifted in opposite directions to suppress vibration and noise caused by backlash regardless of the direction of load transmission. A technique is described in which the two shock-absorbing gears are arranged on both axial sides of the main gear. In addition, the second embodiment of this publication has a structure in which both shock-absorbing gears formed of an elastic body such as hard rubber are fixed to the side surfaces of the main gear with bolts, and the shock is absorbed by the elastic deformation of the shock-absorbing gears themselves. ing. Such a gear device is effective when the amplitude and frequency of fluctuation of the transmitted torque are small.

[0004]

However, such a gear device is provided with a large variation in the transmitted torque, such as a driving force transmission system from a crankshaft to a camshaft of an internal combustion engine, and with a layout and the like. In the case where the gears need to be miniaturized, there is a problem that a shock absorbing gear made of a hard rubber or a resin cannot sufficiently receive the impact, and the rattling noise cannot be sufficiently reduced. Improvement is also desired from the viewpoint of productivity and durability.

[0005] Therefore, if the rubber shock absorbing gear described above is simply made of steel, it is necessary to reduce the tooth width (plate thickness) of the shock absorbing gear in order to impart sufficient elasticity to absorb an impact. However, the strength and durability may be reduced. That is, it is difficult to ensure both elasticity that can suppress rattling noise and the like and high durability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a high level of desired elasticity and durability while using a steel shock-absorbing gear which is particularly suitable when the transmitted driving torque is large. It is an object of the present invention to provide a new gear device compatible with the above.

[0007]

According to the present invention, there is provided a gear device comprising: a main gear; a thin steel buffer gear coaxially disposed adjacent to one side of the main gear in the axial direction; Fixing means for fixing the buffer gear in the axial rotation direction, at least one tooth surface of the buffer gear protrudes more toward the tooth space than one tooth surface of the main gear.

Accordingly, first, when one of the tooth surfaces of the shock-absorbing gear comes into contact with the tooth surface of the mating gear, and the torque applied thereto is very large, the tooth of the shock-absorbing gear is mainly deformed by elastic deformation of the shock-absorbing gear itself. The surface retreats from the tooth space side to absorb the impact, and eventually one tooth surface of the main gear and the tooth surface of the mating gear come into contact.

As described above, the present invention has a structure in which the steel shock absorbing gear is fixed to the main gear in the axial direction and the shock is absorbed mainly by the elastic deformation of the shock absorbing gear itself. The method is suitably applied to a motor having a high transmission torque and a large fluctuation in transmission torque, such as a power transmission system of an internal combustion engine.

According to the first aspect of the present invention, in order to obtain the desired elasticity, the tooth gear of the buffer gear is made longer than the tooth gear of the main gear. For this reason, the length of the teeth of the buffering gear becomes relatively long, and in particular, at the tip of the outer peripheral side that comes into contact with and meshes with the mating gear, it is likely to be elastically deformed in the circumferential direction. Therefore, in order to reduce the spring constant of the shock-absorbing gear, the durability and rigidity of the shock-absorbing gear can be sufficiently reduced as compared with the case where the tooth width of the shock-absorbing gear is reduced. That is, the desired elasticity and durability can be compatible at a high level.

According to the second aspect of the present invention, in order to obtain a desired elasticity, a slit extending radially inward from the tooth tip is formed in the buffer gear so as to divide the tooth thickness in the tooth trace direction. Have been. Therefore, similarly to the first aspect of the invention, the buffer gear has a structure that is easily deformed in the circumferential direction. Therefore, compared with the case where the tooth width of the shock-absorbing gear is reduced, the reduction in durability and rigidity of the shock-absorbing gear is sufficiently suppressed. In other words, it is possible to secure the elasticity and the durability at a high level.

According to the third aspect of the present invention, as described above, the tooth thickness of the buffer gear is set so that the tooth thickness of the buffer gear protrudes more toward the tooth space than the one tooth surface of the main gear. Is set to be larger than the tooth thickness. In this case, the tooth thickness difference between the two is set to be equal to or less than the backlash so as not to hinder the meshing with the mating gear.

In the case of a configuration having a circular plate (that is, a washer) disposed in the axial direction on the side opposite to the main gear side of the buffering gear and fixing the main gear and the buffering gear in the axial direction, it is preferable. The outer diameter of the circular plate is larger than the root diameter of the buffer gear and smaller than the root diameter of the main gear. In this case, the circular plate effectively suppresses the tilting and wobbling of the shock absorbing gear in the axial direction. In addition, since the buffer gear is smaller than the root diameter of the main gear, there is no possibility of interference with the teeth of the mating gear.

Further, when the main gear (and the mating gear) is a helical gear, the circular plate can also have a function of a shim for managing the axial clearance of the main gear.

According to a sixth aspect of the present invention, in the protrusion amount of the tooth surface of the buffer gear with respect to the tooth surface of the main gear to the tooth space side, the protrusion amount on the tooth surface side which comes into contact at the time of driving is the other tooth surface. It is characterized in that it is set to be larger than the amount of protrusion on the side.

[0016]

According to the present invention, it is possible to secure a higher spring constant and durability compared with a shock absorbing gear using hard rubber or the like as described in the above-mentioned publication, while having a simple and compact structure. Even if the input fluctuation is large, the impact can be effectively reduced, and the vibration and rattle caused by the backlash can be effectively reduced. In addition, in order to appropriately reduce the spring constant, the height of the tooth root of the shock-absorbing gear is made longer than that of the tooth root of the main gear, or a radially extending slit is formed in the shock-absorbing gear. A reduction in rigidity and durability due to a reduction in the spring constant is suppressed to a minimum.

In addition, according to the invention according to claim 4, a circular plate (so-called washer) for fixing the buffering gear and the main gear in the axial direction can effectively prevent wobble in the out-of-plane direction of the buffering gear. Since it is possible to suppress the three-dimensional deformation such as the turning of the tooth tip side, it is possible to more reliably prevent the reduction of the buffer function and the generation of noise.

Further, according to the fifth aspect of the present invention, since the circular plate has a function of a shim for managing the axial clearance of the main gear, the axial clearance of the gear device has a simple structure. Can be maintained at a sufficiently small value, and even when the axial excitation force generated accompanying the transmission of torque by the helical gear acts, noise generation due to axial rattling etc. is minimized. Can be.

According to the sixth aspect of the invention, even when the torque fluctuation during driving is large and a large buffering function is required, a sufficient buffering function for a large input is ensured.
Toothing noise can be reliably suppressed.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a gear device according to the present invention will be described.
An embodiment applied between a crankshaft and a camshaft as a driving force transmission system of an internal combustion engine will be described in detail with reference to the drawings.

1 to 5 show a first embodiment. As shown in FIG. 1, two camshafts 2a and 2b are arranged in parallel in the cylinder row direction above the cylinder head 1. A drive cam 2 for driving an intake valve or an exhaust valve (not shown) is provided on each of the camshafts 2a and 2b.
c is provided for each cylinder, and each camshaft 2a,
2b is rotatably supported around the axis between the cam caps 3a, 3b, 3c and the cylinder head 1.

At the front end (left end in FIG. 1) of each camshaft 2a, 2b, a hard steel drive gear (counter gear) is provided.
4, a driven gear (main gear) 5 is attached. A chain sprocket 6 is provided at the front end of the drive gear 4, and the chain sprocket 6 is provided with a chain mechanism (not shown) from a crankshaft (not shown).
The driving force is transmitted via the. These drive gears 4
The chain sprocket 6 and the chain sprocket 6 are axially fastened and fixed to the front end of one camshaft 2a by bolts 8a via washers 7a.

On the other hand, cushion gears (buffer gears) 9a, 9b) are arranged on both sides in the axial direction of the driven gear 5 so as to sandwich the driven gear 5. These cushion gears 9a and 9b are made of the same hard steel as the gears 4 and 5, and are coaxially fixed to the front end of the camshaft 2b by bolts 8b via washers 7b. Here, the total tooth width of the gears 9a, 5 and 9b arranged coaxially next to each other is such that the cushion gears 9a and 9b mesh with the drive gear 4 together with the driven gear 5.
Is set to be equal to or less than the tooth width.

The drive gear 4 and the driven gears 5, 9a, 9b are provided with, for example, a dowel pin (not shown) provided on a flange 2d at the front end of the camshafts 2a, 2b.
Is positioned and fixed around the axis,
The camshafts 2a and 2b are configured to rotate integrally with the camshafts 2a and 2b.

Therefore, when the crankshaft rotates,
The chain sprocket 6 rotates around the axis via the chain mechanism, and the drive gear 4 and the camshaft 2a rotate integrally with the chain sprocket 6,
The driven gear 5 meshing with the drive gear 4 rotates, and the camshaft 2b rotates integrally with the driven gear 5.

FIG. 2 is an exploded explanatory view showing details of the structure of the driven gear 5 side. Cushion gears 9a, 9b
Are axially coupled with each other so as to sandwich the driven gear 5. In this embodiment, the positioning and fixing of the cushion gears 9 a and 9 b in the rotational direction with respect to the driven gear 5 are performed by a pin 10 protruding from the side surface of the driven gear 5. And holes 11 formed in the cushion gears 9a and 9b.
a and 11b (fitting means). The positioning and fixing of the driven gear 5 (and the cushion gears 9a and 9b) and the camshaft 2b in the direction around the axis are performed by using the dowel pins provided on the flange portion 2d of the camshaft 2b by the driven gear 5 and the cushion gears 9a and 9b. Hole 1 formed in
This is carried out by fitting them into 2 and 13. In order to absorb a dimensional error or the like, the hole 13 is not a fitting but a relief hole for the dowel pin, and is formed to have a relatively larger diameter than the hole 12.

The washer 7b is a hard thin circular plate, which receives the bearing surface of the head of the bolt 8b, and the gears 9a, 5 and 5 between the washer 7b and the flange 2d of the camshaft 2b.
It has a function of fastening and fixing in the axial direction so as to sandwich 9b. Here, the outer diameter of the washer 7b is set to be larger than at least the root diameter of the adjacent cushion gear 9a, as shown by the one-dot chain line in FIGS. It also has the function of suppressing deformation of the portion in the out-of-plane direction. The outer diameter of the washer 7b is set to be smaller than the root diameter of the driven gear 5 so as not to buffer the teeth of the drive gear 4 by any chance.

FIG. 3 is an enlarged view of the tooth tips of the driven gear 5 and the cushion gear 9 (9a, 9b).
The tooth thickness 9c of the cushion gear 9 is formed to be larger by a predetermined amount than the tooth thickness of the driven gear 5, and the difference between the tooth thicknesses is preferably equal to or less than the backlash between the gears 4 and 5, more preferably substantially the backlash. Is set equal to As a result, both tooth surfaces of the cushion gear 9 protrude toward the tooth space with respect to both tooth surfaces of the driven gear 5. The protrusion amount of the tooth surface of the cushion gear 9 is set to the same value (Δt) on both tooth surface sides, for example.

The tooth grooves of the cushion gear 9 are set deeper than the tooth grooves of the driven gear 5. That is, as shown in FIG. 4, the radial distance from the tooth bottom of the cushion gear 9 to the pitch circle P1, that is, the root height H1
However, it is set larger than the root height H2 from the tooth bottom of the driven gear 5 to the pitch circle P1.

In this embodiment, the cushion gear 9 is used.
Although a and 9b are set to have the same shape, they may have different shapes.

Next, the operation of the present embodiment will be described with reference to FIGS. Note that arrows A1 and A2 indicate the rotation directions of the gears 4 and 5, respectively. When the drive gear 4 bites into the driven gear 5, the tooth thickness of the cushion gear 9 is larger than that of the driven gear 5, and the cushion gear 9
Of the drive gear 4
First comes into contact with the cushion gear 9 (FIG. 4). When the input from the drive gear 4 is very large, the impact is reduced by mainly elastically deforming the tooth tip portion of the cushion gear 9 in the circumferential direction, and finally the drive gear 4 is connected to the driven gear 5. Contact (FIG. 5).

As described above, in the present embodiment, the shock is reduced and absorbed by the elastic deformation of the steel cushion gears 9a and 9b fixed to the driven gear 5. For this reason, a spring element such as a spring is unnecessary as in the above-described conventional example, and a simple and compact configuration can be achieved. Further, even when applied to a portion where torque fluctuation is large and downsizing is required due to a layout or the like, such as a gear of a valve train of an internal combustion engine or a crank gear, a sufficient spring constant can be secured. In addition, vibration and rattling noise due to backlash can be reliably reduced.

In particular, in the present embodiment, the cushion gear 9
By setting the root height H1 of the roots a and 9b to be larger than the root height H2 of the driven gear 5, the cushion gear 9 is provided.
The spring constants of the cushion gears 9a and 9b can be effectively suppressed without lowering the rigidity and durability of the cushions 9a and 9b, and the desired elasticity and durability can be compatible at a high level.

The rigidity (elasticity, in other words) of the tooth tips of the cushion gears 9a and 9b can be adjusted by their tooth width and tooth groove depth. Therefore, by setting the tooth stiffness in accordance with the value of the torque fluctuation on the drive gear 4 side and the value of the inertia moment on the driven gear 5 side, it is possible to obtain an appropriate rattling noise reduction effect according to the load condition.

FIG. 6 is an enlarged view of the tooth tips of the driven gear 5 and the cushion gear 15 according to the second embodiment. In the following description, the overall structure is shown in FIG.
The third embodiment is the same as the first embodiment shown in FIGS. 1 to 3, and the same portions are denoted by the same reference characters and overlapping description will be appropriately omitted.

In an internal combustion engine, torque fluctuation during driving is generally large, and a larger cushioning function is required on the contact tooth surface side during driving. Therefore, in the second embodiment, the cushion gear 15 with respect to the tooth surface of the driven gear 5 is used.
Of the protruding amount (difference in tooth thickness) of the driven gear 5
The tooth thickness difference Δt1 on the tooth surface side contacting the drive gear 4 when driven, ie, the lower tooth surface side in FIG. 6, is the tooth thickness difference on the tooth surface side not contacting during driving, ie, the upper tooth surface side in FIG. It is set larger than Δt2. As a result, even when a large input acts on the contact tooth surface during driving, a sufficient cushioning function is ensured, and it is possible to reliably suppress the rattling noise.

The tooth surfaces on the side that does not come into contact during driving (upper side in FIG. 6) collide with each other because the negative value of the drive torque fluctuation is small, or the driven gear 5 is constantly provided with rotational resistance. When the possibility of rattling noise is low, the cushioning function on the tooth surface side is substantially unnecessary, and thus the tooth thickness difference Δt2 may be set to approximately 0 (zero).

Alternatively, as shown in FIG. 7, the tooth profile (teeth thickness) of the tip of the cushion gear 15 'is made the same as that of the driven gear 5, and the driven gear 5 of the cushion gear 15' is formed.
The same effect can be obtained by fixing the cushion gear 15 'and the driven gear 5 in the axial direction while the phase with respect to is shifted by the tooth thickness difference Δt1. In this case, the tooth surface of the driven gear 5 on the tooth surface that does not contact during driving is Δt toward the tooth space from the tooth surface of the cushion gear 15 ′.
It will protrude by one.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 8 is an enlarged view of the tooth tips of the driven gear 5 and the cushion gear 16 (16a, 16b) in the present embodiment. As in the first embodiment, the tooth thickness of the cushion gear 16 is formed larger than the tooth thickness of the driven gear 5, and the difference between the tooth thicknesses is preferably equal to or less than the backlash between the gears 4 and 5, and more preferably approximately. It is set equal to the backlash.

A single slit 17 extending radially inward from the tooth tip is formed in the tooth tip portion of each cushion gear 16 so as to divide the tooth thickness into two in the tooth trace direction. Note that a plurality of slits 17 may be provided intermittently.

In this embodiment, the roots of the cushion gear 16 and the driven gear 5 are set to be the same. However, in order to further reduce the spring constant, the tooth height of the cushion gear may be relatively increased as in the first and second embodiments.

As described above, in the third embodiment, the slit 17 extending in the radial direction is formed in the cushion gear 16, so that, for example, the tooth width is reduced in order to suppress the spring constant. Rigidity of the cushion gear 16,
A decrease in durability can be suppressed. Therefore, the desired elasticity and durability of the cushion gear 16 can be compatible at a high level.

The present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the gist of the present invention. For example, in the first to third embodiments, cushion gears are provided on both sides of the driven gear 5 in the axial direction, but a cushion gear may be provided on the drive gear 4 side. It is good also as a structure provided with a cushion gear only in.

The drive gear 4 and the driven gear 5
May be a helical gear. In this case, the washer (circular plate) 7 preferably has a function of a shim for managing the axial clearance of the driven gear 5.

[Brief description of the drawings]

FIG. 1 is a top view corresponding to an internal combustion engine to which a gear device according to a first embodiment of the present invention is applied.

FIG. 2 is an exploded perspective view of the gear device according to the first embodiment.

FIG. 3 is a perspective view illustrating a main part of the first embodiment.

FIG. 4 is an operation explanatory view of the first embodiment.

FIG. 5 is an operation explanatory view of the first embodiment.

FIG. 6 is a configuration diagram of a second embodiment.

FIG. 7 is a configuration diagram showing another example of the second embodiment.

FIG. 8 is a perspective view showing a main part of a third embodiment.

FIG. 9 is an operation explanatory view of the third embodiment.

FIG. 10 is an operation explanatory view of the third embodiment.

[Explanation of symbols]

 4 Drive gear (mating gear) 5 Driven gear (main gear) 7b Washer (circular plate) 9a, 9b Cushion gear (buffer gear) 10 Pin (fixing means) 11 Hole (fixing means) 15, 15 ' , 16 ... cushion gear (buffer gear) 17 ... slit

Claims (6)

[Claims] 1. A main gear, a thin steel buffer gear coaxially disposed adjacent to one side in the axial direction of the main gear, and fixing means for fixing the main gear and the buffer gear in the axial rotation direction. ,
Wherein at least one tooth surface of the buffer gear protrudes toward the tooth space more than one tooth surface of the main gear, and the gear root of the buffer gear is smaller than the gear root of the main gear. A gear device characterized in that it is also long. 2. A main gear, a thin steel buffer gear disposed coaxially adjacent to one axial side of the main gear, and fixing means for fixing the main gear and the buffer gear in the axial rotation direction. ,
At least one tooth surface of the buffering gear projects to the tooth space side than one tooth surface of the main gear, and the buffering gear has teeth so as to divide the tooth thickness in the tooth trace direction. A gear device, wherein a slit extending radially inward from the tip is formed. 3. The gear according to claim 1, wherein the tooth thickness of the buffer gear is larger than the tooth thickness of the main gear, and the difference between the tooth thicknesses is set to be less than the backlash. apparatus. 4. A circular plate is provided adjacent to the buffer gear in a direction opposite to the main gear in the axial direction, and has a circular plate for fixing the main gear and the buffer gear in the axial direction. The gear device according to any one of claims 1 to 3, wherein the root diameter is larger than the root diameter of the buffer gear and smaller than the root diameter of the main gear. 5. The gear device according to claim 4, wherein the main gear is a helical gear, and the circular plate also has a function of a shim for managing an axial clearance of the main gear. 6. The protruding amount of the tooth surface side of the buffer gear, which is in contact with the driving gear, on the tooth surface side of the buffer gear relative to the tooth surface of the main gear is smaller than the protruding amount on the other tooth surface side. The gear device according to any one of claims 1 to 5, wherein the gear device is set large.