JP2871243B2 - Scissor gears for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scissors gear for an internal combustion engine, and is capable of suppressing noise at a meshing portion regardless of the rotational speed of the internal combustion engine.

[0002]

2. Description of the Related Art In a drive mechanism of an internal combustion engine, a scissor gear is used for a gear engaging portion so that noise due to backlash is not generated regardless of rotation fluctuation of the internal combustion engine. The scissors gear has a main gear fixed on a rotating shaft, a sub gear rotatable relative to the main gear,
It consists of a scissor spring that urges the sub gear against the main gear in the rotation direction.The elastic force obtained by the scissor spring causes the sub gear to engage the gear tooth surface on the other side in the opposite direction to the main gear, eliminating backlash Is trying to suppress the noise.

As another method for suppressing backlash, a weight body receiving a centrifugal force is provided as shown in Japanese Patent Application Laid-Open No. 62-20964, and the weight body is moved in the radial direction according to the centrifugal force. It discloses a structure in which the main gear and the auxiliary gear are caused to rotate relative to each other, and the biasing force is changed according to the rotation speed of the internal combustion engine.

[0004]

In an internal combustion engine, in particular, in a balance shaft driven by a gear directly from a crankshaft, noise at the meshing portion of the gear between the crankshaft and the balance shaft is (a) near the idling rotation ( For example, 75
Backlash at 0 rpm) and (b) 20 from 1000 rpm
There is meshing noise at 00 rpm (noise generated based on gear meshing) and (c) rattling at 3000 rpm or more. That is, idling rotation and 3000 rpm
Above, noise is generated due to backlash (that is, backlash), but from 1000 rpm to 2000 rpm, noise generated when the tooth surfaces of the gear mesh with each other is mainly caused by noise caused by backlash. The rattle near idling in (a) can be suppressed by applying a pinching torque of about 1 N × m between the main gear and the auxiliary gear. Also, the noise in (b) is not generated by backlash, but rather is generated when the gears are strongly engaged.
In the range of 2,000 rpm to 2,000 rpm, it can be dealt with by setting the pinching torque so that the engaging force does not become excessive. However, in the case of a rattling sound of 3000 rpm or more, it cannot be dealt with unless a strong pinching force of 10 N × m is applied. However, under a strong meshing torque of 10 N × m, the gear meshes from 1000 rpm to 2000 rpm, so that a large noise is generated due to meshing between the tooth surfaces. That is, it was not possible to suppress noise in a wide rotation speed range by using a scissors gear or a mechanism for applying a pinching torque by centrifugal force alone in the related art.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress noise of different causes which occurs over a wide rotation range used in an internal combustion engine.

[0006]

According to the present invention, a main gear which is used for one of gears meshing with each other of an internal combustion engine and is fixed on a rotating shaft, and which is rotatable relative to the main gear. In the scissors gear consisting of a sub gear and a scissors spring that urges the sub gear in the rotational direction with respect to the main gear, the scissor spring has an annular shape cut off at one place, and its opposite end is
The relative rotation between the main gear and the auxiliary gear is obtained by being engaged with pins fixed respectively to the main gear and the sub gear, and the weight that can move in the radial direction of the gear by centrifugal force is interposed between the pins. And the side surface of the weight that is in contact with each pin is formed so as to exert a rotational urging force in a direction opposite to the urging direction of the scissors spring due to the radial movement of the weight due to centrifugal force. There is provided a scissors gear.

[0007]

[Function] The scissor spring exerts a torque that causes the main gear and the sub gear to rotate in one direction with respect to each other. On the other hand, the centrifugal force generated by the rotation of the engine causes the weight body to move outward in a radial direction. , A torque in a direction opposite to the elastic torque by the scissors gear is applied between the main gear and the sub gear. Therefore, the backlash is suppressed by the elastic torque of the scissors gear in the low engine speed state, and the noise is suppressed by the backlash by the torque in the opposite direction to the elasticity by the centrifugal force in the high engine speed state. In the intermediate rotational speed range, the elastic torque of the scissors gear and the opposite torque due to the centrifugal force cancel each other out, the torque becomes zero or weak, and the surface pressure of the engaging portion of the teeth can be reduced, and the noise due to the surface pressure Can be suppressed.

[0008]

1 to 5 show a scissor gear according to the present invention. A scissor gear 10 has a main gear 11 and a sub gear 12 divided along its axis, and the main gear 11 and the sub gear 12 have central holes 14 and 16 respectively. And a rotating shaft (not shown) is inserted. The main gear 11 and the sub-gear 12 have teeth 11a, 12a of equal pitch on the outer circumference.
It is larger than a. The main gear 11 is fixed to the rotation shaft by a key or the like (not shown), but the sub gear 12 is simply fixed to the rotation shaft and is not fixed, and the sub gear 12 can rotate relative to the main gear 11. I have. The main gear 11 and the sub-gear 12 have annular recesses 18 and 20 on opposite side surfaces, and the recesses 18 and 20 form an annular space. A scissors spring 22 is arranged in this annular space. The scissor spring 22 has an annular shape cut at one point, and pins 24 and 26 are engaged with the opposite ends of the scissor spring 22. One pin 24 is implanted in a pin hole formed in the main gear 11, and the other is The pin 26 is implanted in a pin hole formed in the sub gear 12. The scissors spring 22 exhibits an elastic force such that the opposing pins 24 and 26 approach,
As a result, the main gear 11 connected to the pins 24 and 26
The sub gear 12 receives a biasing force from the scissors spring 22 such that the sub gear 12 rotates in one direction.

[0009] The main gear 11 and the sub gear 12 are
The bosses 28 and 30 are provided inside the radii of the bosses 8 and 20 and one boss, for example, the boss 2 of the main gear 11
8 as a centrifugal force sensitive moving member in a groove formed in
2 are arranged slidably in the radial direction. The weight 32 is shown in FIG.
As shown in the figure, the base 32a includes an arch-shaped base 32a extending in the circumferential direction and a protrusion 32b extending in the radial direction from the base 32a and having a smaller width in the circumferential direction than the base 32a. The connection is made by a side surface 32c which is vertical but gradually becomes less inclined thereafter. As shown in FIG. 6, when the scissors spring 22 is mounted, the pins 24 and 26
It exerts an elastic force such as pressing against c.

FIG. 8 shows a scissors gear 1 in a drive system of an internal combustion engine (for example, a drive connection between a crankshaft and a camshaft).
The operation of the present invention when 0 is used will be described. Figure
At 8, the arrow A indicates the direction of rotation. In FIG. 8A, the scissors gear 10 has a counterpart meshed with the gear 40.
The main gear 11 and the sub gear 12 are relatively rotated within the range of the backlash in the direction in which the gears contract (direction c in FIG. 6), and the teeth 11a of the main gear 11 engage with one surface of the tooth groove of the mating gear 40. The sub gear 12 is provided on the other surface of the tooth space.
Are engaged. In this state, since the centrifugal force (direction a in FIG. 6) applied to the weight 32 is small, the elastic force itself of the scissor spring 22 becomes the scissor torque between the main gear 11 and the sub gear 12, and this is the scissor gear 10
That is, the backlash between the gear and the counter gear 40 is suppressed. FIG. 6 assumes an idling state of the internal combustion engine (engine speed = about 750 rpm), and is based on the backlash at the time of idling with a relatively weak scissor torque C (for example, about 2 N × m) only by the elasticity of the scissors gear 10. The rattling noise can be suppressed.

As the engine speed increases, the centrifugal force (FIG. 6)
The weight 32 moves radially outward according to the direction a).
Therefore, the pins 24 at both ends of the scissor spring 22
26, when the inclination of the side surface 32c of the weight body 32 gradually comes in contact with the portion gradually loosened (arrow b in FIG. 6), the opposite ends of the scissors spring 22 are expanded, and the elastic scissors torque applied from the scissors spring 22 is It becomes weaker by the torque B based on the centrifugal force. Scissors Torque N _n against engine speed n is expressed by _{N n = C-B = C} -k × n 2. Here, k is a constant, and is set so that the scissor torque C based on the elastic force is almost offset with the scissor torque B based on the centrifugal force in a region where the engine speed is not so high, for example, less than 3000 rpm. for that reason,
In the rotation speed region below 3000 rpm, the scissor gear 10
Is zero or a small value (for example, 2000
The rotation is set to -2.8 N x m (the-sign means that the scissors torque is in the opposite direction to that due to elasticity). Accordingly, rattling due to backlash may occur, but in this rotational speed region, noise due to surface pressure between the teeth 11a and 12a engaged between the gears 10 and 40 is more important than rattling due to backlash. Therefore, by suppressing the scissors torque obtained by the scissors spring 22, the surface pressure between the engaging teeth 11a and 12a, which is a main noise generation factor, can be suppressed, and the noise can be suppressed as a whole.

In the region where the engine speed is higher than the intermediate region, for example, 3000 rpm or more, the scissor torque B in the rear direction based on the centrifugal force becomes considerably larger than the scissor torque C based on the elastic force, and FIG. As shown in FIG. 6, the positional relationship between the main gear 11 and the sub gear 12 is opposite to that in FIG. 6, and in this case, the backlash is suppressed by scissor torque due to centrifugal force. In this case, the scissors torque required for rattling suppression is −10 N × m or more.

[0013] The torque transmitting surface of the scissors gear 10 may be a main gear or a sub gear at idling when the backlash is suppressed by elasticity and at 3000 rpm or more when the backlash is suppressed by the centrifugal force.
Assuming the rotation direction of FIG. 8, idling (FIG. 8)
In (a)), the tooth surface P of the sub gear 12 becomes a torque transmitting surface,
At 3000 rpm or more (FIG. 8B), the tooth surface P 'of the main gear 11 becomes the torque transmitting surface. This is the main gear 11
Since the width of the teeth is larger, consideration is given to receiving the surface pressure by the main gear 11 at the time of high rotation in which a large surface pressure is applied.

[0014]

According to the present invention, the backlash is suppressed by the elastic torque of the scissor spring at low rotation, the backlash is suppressed by the torque in the opposite direction due to the centrifugal force at high rotation, and the torque is suppressed in the intermediate rotation speed region. Therefore, the surface pressure at the engaging tooth portion can be reduced, and noise due to the surface pressure can be suppressed. Therefore, there is an effect that noise can be suppressed over the entire rotation speed range of the engine.

[Brief description of the drawings]

FIG. 1 is a side view (FIG. 2) of a scissor gear according to the present invention;
(Shown as viewed from the line II).

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a cross-sectional view taken along the line VI-VI of FIG. 1;

FIG. 5 is a sectional view taken along line VV of FIG. 1;

FIG. 6 is a partially enlarged view of FIG. 1;

FIG. 7 is a perspective view showing a single weight body.

FIG. 8 is a diagram illustrating a meshing state between a scissors gear and a counterpart gear.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Scissors gear 11 ... Main gear 12 ... Sub gear 22 ... Scissors spring 24,26 ... Pin 32 ... Plummet 40 ... Counter gear

Claims (1)

(57) [Claims] 1. A main gear, which is used for one of gears meshing with each other of an internal combustion engine and is fixed on a rotating shaft, and a sub gear that can rotate relative to the main gear;
In a scissor gear including a scissor spring that urges the sub gear in the rotation direction with respect to the main gear, the scissor spring has an annular shape cut off at one place,
The opposite ends are engaged with pins fixed to the main gear and the sub gear, respectively, to obtain the relative rotation between the main gear and the sub gear, and to be movable in the radial direction of the gear by centrifugal force. The weight is sandwiched between the pins, and the side surface of the weight that comes into contact with each pin exerts a rotational urging force in a direction opposite to the urging direction of the scissors spring due to the radial movement of the weight due to centrifugal force. A scissors gear formed as described above.