JP2878010B2 - Pressure regulation mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conversion mechanism for converting a rotational force into a moving force in an axial direction, that is, a pressure adjusting mechanism of a climbing cam type.

[0002]

2. Description of the Related Art As a pressure adjusting mechanism of this type, for example, an automatic pressure adjusting mechanism provided in a transmission device disclosed in Japanese Utility Model Laid-Open Publication No. 3-81443 has both a driving and driven side rotating body. A ball is interposed between the recessed cam grooves respected by the ball, and the balls are climbed onto the cam surface by the relative rotation of the two rotating bodies so that the two rotating bodies are pressed in a direction away from each other in the axial direction. Is known.

[0003]

In the pressure regulating mechanism, a retainer for determining the position of the ball is provided between the driving rotating body and the driven rotating body. That is, as shown in FIG. 9, the concave cam portions 2 of the rotating bodies 19 and 29 are radial grooves formed by the two cam planes 2a and 2b inclined in the circumferential direction. A pressure adjusting mechanism 21 is provided with a retainer 3 for positioning in the circumferential direction and for positioning so that the ball 1 does not move freely in the radial direction.
Is configured.

However, in the pressure adjusting mechanism 21 having the above structure, the radial moving force of the ball 1 is received only by the retainer 3, so that a large load acts instantaneously on the pressure adjusting mechanism 21. If the relative rotational force of the pressure adjusting mechanism 21 increases, the retainer 3 may be deformed in some cases. SUMMARY OF THE INVENTION It is an object of the present invention to avoid the above-mentioned fear by preventing the excessive radial force from acting on the retainer by reviewing the structure of the concave cam portion.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a drive-side rotating body and a driven-side rotating body which are externally fitted to a support shaft and are arranged to face each other via a plurality of balls. A recessed cam portion for engaging a ball is formed on one of the ball contact surfaces of the two rotating bodies, so that the two rotating bodies are relatively separated from each other in the axial direction of the support shaft by the relative rotation of the two rotating bodies. In a certain rising cam type pressure adjusting mechanism, the ball engagement depth of the concave cam portion gradually changes in the circumferential direction, and the movement locus of the ball center at the concave cam portion is centered on the axis of the support shaft. The concave cam portion is characterized in that a wall portion for constantly restricting the ball in the concave cam portion from moving in the radial direction of the axis is formed in the concave cam portion so as to coincide with the circular arc locus.

[0006]

When the rotating body on the driving side and the rotating body on the driven side relatively rotate and the ball moves in the circumferential direction, the above-mentioned characteristic structure has a wall for restricting the ball from moving in the radial direction of the axis. Since the recessed cam portion is formed, even if a radial force is applied to the ball with respect to the axial center, the force is always covered by the wall portion and does not act on the retainer.

That is, the movement locus of the center of the ball accompanying the operation of the pressure adjusting mechanism coincides with the arc locus centered on the axis of the support shaft, that is, the ball whose position in the radial direction does not physically change. Therefore, the ball does not move in the radial direction regardless of the magnitude of the input, such as an excessive input or a small input.

[0008] Therefore, the radial force is prevented from acting on the retainer as in the prior art, and the function of simply positioning a plurality of balls in the circumferential direction, that is, the simple holding function with little applied stress is applied to the retainer. Just have it.

[0009]

As a result, an excessive stress does not act on the retainer, so that the durability can be improved, or the retainer can be made of a low-strength member such as a resin. The pressure regulating mechanism which can contribute to the improvement of the performance can be provided.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 4 to 6 show a power transmission device A mounted on a lawn mower. The power transmission device A includes a power input unit 9 for inputting the power of an engine (not shown) by a belt transmission mechanism 7, a friction type continuously variable transmission mechanism 11 using a taper cone 10 for continuously changing the input power, and a friction type transmission. The transmission includes a forward / reverse switching mechanism 12 capable of switching the rotation direction of the output of the step transmission mechanism 11, a differential mechanism 13, and the like, and the friction type continuously variable transmission mechanism 11, the forward / reverse switching mechanism 12, and the differential mechanism 13 , In one case 14.

The power input unit 9 includes a longitudinal axis 16 having an input pulley 15 and an input rotating body 17 of the friction type continuously variable transmission mechanism 11.
Are linked by a bevel gear mechanism.
The friction type continuously variable transmission mechanism 11 revolves around an axis of the main shaft 18 around an axis of rotation of a main shaft 18 rotatably supported by a case 14 by an input rotating body 17 arranged concentrically with the main shaft 18. A plurality of self-rotating taper cones 1 to be driven
0, and an output rotating body 19 that is driven and rotated in contact with these taper cones 10 is attached to the main shaft 18.
The transmission member 20 is provided so as to be able to shift in the axial direction in a contact state over the taper cones 10.

The tapered cone 10 comes into pressure contact with the output rotating body 19 which is pressed and urged in the axial direction by the pressure adjusting mechanism 21, receives the reaction force thereof by the disk-shaped cone support 22, and applies the reaction force to the input rotating body 17. A carrier 25 is formed by the attached outer frame 23 and the inner frame 24 connected to the outer frame 23, and the taper cone 10 is rotatably supported on a support shaft 26 provided between the outer frame 23 and the inner frame 24. ing.

The forward / reverse switching mechanism 12 includes a main shaft 18 and an intermediate shaft 28 having a brake device 27 at one end. More specifically, a drive gear 29 of the main shaft 18 and a driven shaft of the intermediate shaft 28 are driven. The drive sprocket 31 of the main shaft 18 and the driven sprocket 32 of the intermediate shaft 28
The transmission is set so as to transmit the rotation in the forward direction by a chain 33 that is stretched between the gears and the rotation direction of the intermediate shaft 28 can be selected by selectively engaging the driven gear 30 and the driven sprocket 32 of the shift rotating tool 34. I have.

The transmission member 2 of the friction type continuously variable transmission mechanism 11
As shown in FIG. 1, the operation unit 5 for performing the shift operation of the front and rear 0 and the operation unit 6 for performing the shift operation of the shift rotating tool 34 of the forward / reverse switching mechanism 12 are provided on the upper surface portion and the rear surface portion of the case 14. Each of the operating units 5 and 6 is associated with a shift and forward / reverse lever (not shown).

As shown in FIGS. 1 to 3, the pressure regulating mechanism 21 includes an output rotator 19 as a driving rotator and a driving gear 29 as a driven rotator via a plurality of balls 1. The output rotator 1
The relative rotation of the output rotating body 19 and the driving gear 29 on the ball contact surfaces of both the driving gear 9 and the driving gear 29 causes the output rotating body 19 and the driving gear 29 to relatively separate in the axial direction of the main shaft 18. Is formed as a climbing cam type in which concave cam portions 2 and 2 are formed.

The concave cam portion 2 is formed, for example, by milling using an end mill having a spherical lower end, and its circumferential cross section in which the ball engagement depth h gradually increases and decreases in the circumferential direction is circular. The shape is an arc shape (see FIG. 3), and the cross section in the radial direction is also set to a shape exhibiting a circular arc shape (see FIG. 2). That is, the inner and outer wall portions 2a, 2a for restricting the movement of the ball 1 in the recessed cam portion 2 in the radial direction of the axis P are formed in the recessed cam portion 2.
Regardless of the relative position of the output rotator 19 and the drive gear 29 in the circumferential direction, the movement trajectory L of the ball center Q in the state of being engaged with the concave cam portion 2 is represented by the axis P of the main shaft 18. Always coincides with the arc locus around.

That is, even if the pressure adjusting mechanism 21 is actuated, the position of the ball 1 in the radial direction does not change, and the resin retainer 3 straddling the six balls 1 has a ball moving force in the radial direction. First, it does not work.

As shown in FIG. 7, the forward / reverse switching mechanism 12 is of a dog dog clutch type. The passive gear 30, the passive sprocket 32, and the clutch pawls 30a, 32a, 34a of the shift rotating tool 34 are configured to have a shallow axial depth and a wide radial width.
Each of the clutch claws 30a, 32a, and 34a is formed integrally with the ring-shaped continuous surface portion 4 that protrudes toward the inner diameter side or the outer diameter side, and compensates for the strength of the clutch claws 30a, 32a, and 34a. It is convenient when the shift rotating tool 34 is made of a sintered alloy.

[Alternative Embodiment] As shown in FIG. 2, the concave cam portion 2 has a V-shaped cross section in the radial direction.
It may be formed so as to form a groove. Even in this case, the movement locus L of the ball center Q in a state of being engaged with the concave cam portion 2
Corresponds to an arc locus centered on the axis P of the support shaft 18.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a side view of a rotating body showing a shape of a cam portion.

FIG. 2 is a sectional view of a pressure regulating mechanism showing a sectional shape in a radial direction of a cam portion.

FIG. 3 is a cross-sectional view of a pressure adjusting mechanism showing a cross-sectional shape of a cam portion in a circumferential direction.

FIG. 4 is an expanded sectional view showing an input side structure of the power transmission device.

FIG. 5 is an expanded sectional view showing the output side structure of the power transmission device.

FIG. 6 is a side view showing the appearance of the power transmission device.

FIG. 7 is an exploded perspective view showing the structure of a forward / reverse rotation mechanism.

FIG. 8 is a cross-sectional view of a pressure adjusting mechanism showing another shape of the cam portion.

FIG. 9 is an exploded perspective view showing the structure of a conventional pressure adjusting mechanism.

[Explanation of symbols]

 Reference Signs List 1 ball 2 concave cam portion 2a wall portion 18 support shaft 19 driving-side rotating body 29 driven-side rotating body P axis Q ball center L movement locus

Claims (1)

(57) [Claims] 1. A drive-side rotating body (19) and a driven-side rotating body (29), which are externally fitted to a support shaft (18), are arranged to face each other via a plurality of balls (1), and the two rotations are performed. One of the ball contact surfaces of the bodies (19) and (29)
A ball engaging recess for causing the two rotating bodies (19) and (29) to move away from each other in the axial direction of the support shaft (18) by the relative rotation of the two rotating bodies (19) and (29). A climbing cam type pressure adjusting mechanism having a cam portion (2), wherein a ball engagement depth of the recessed cam portion (2) gradually changes in a circumferential direction and the recessed cam portion. as the ball (2) (1) moving locus of the center (L) coincides with an arc locus around the axis (P) is of the support shaft (18), said concave
The ball (1) in the input cam portion (2) is the shaft center.
The wall part (2) which always restricts the movement in the radial direction of (P)
a) and (2a) are formed in the concave cam portion (2) .