JP2001082571A - Action force conversion mechanism and driving force transmission device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate play between balls and ball grooves in ball-screw- structure action force conversion mechanisms by giving pre-loads among the balls, screw members and nut members. SOLUTION: The ball-screw-structure action force conversion mechanism uses a screw member 31 and a nut member 32 respectively provided with pluralities of ball grooves 31c to 31f and 32c to 32f. The lead angle or track centerline of the ball grooves 31c to 31f of the screw member 31 and the lead angle or track centerline of the ball grooves 32c to 32f of the nut member 32 are set different from each other, which applies pre-loads among balls 33, the screw member 31 and the nut member 32 to thus eliminate play between the balls 33 and ball grooves 31c to 31f and 32c to 32f.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acting force conversion mechanism and a driving force transmitting device using the same.

[0002]

2. Description of the Related Art A screw member having a ball groove extending in a circumferential direction on an outer periphery as one type of an acting force converting mechanism,
A nut member having a ball groove extending obliquely in the circumferential direction on the inner periphery and having a nut member fitted concentrically and relatively rotatably to the outer periphery of the screw member; and a ball interposed between the ball grooves of the nut member and the screw member. There is an action force conversion mechanism that converts a rotational force for relatively rotating these two members and an axial force for relatively moving these two members in the axial direction by the action of the ball and the ball groove.

The acting force conversion mechanism is structurally known as a ball screw mechanism, and is registered in Utility Model Registration No. 2519.
As shown in Japanese Patent Application Laid-Open No. 936, the rotational force as an input from the pilot mechanism is output as an axial force to the clutch mechanism side and provided between the clutch mechanism and the pilot mechanism constituting the driving force transmission device. It functions to control the operation of the clutch mechanism.

[0004]

The ball screw mechanism (operating force conversion mechanism) has a single thread structure, and the ball is removed from both grooves (ball grooves) forming the screw structure. In order to prevent the ball from coming out, a circulation mechanism for circulating the ball is provided, and the ball groove is lengthened. For this reason, the structure of the ball screw mechanism becomes complicated, and it becomes longer in the axial direction and becomes larger.

In order to shorten the axial length of the ball screw mechanism, the lead angle of the ball groove may be reduced. However, when the lead angle of the ball groove is reduced, the screw member and the nut member are relatively moved in the axial direction. The output to be moved becomes small, and the operation responsiveness of a device using the output as a drive source is reduced.

In order to address such a problem, the present applicant has proposed a ball screw mechanism having a plurality of thread structures in Japanese Patent Application No. 11-096908. In the ball screw mechanism, even if the number of balls interposed in each ball groove is one or a small number, the state between the screw member and the nut member is stable. For this reason, according to the ball screw mechanism, the number of balls interposed in each ball groove can be reduced, the length in the axial direction can be reduced, the size can be reduced, and the ball interposed in each ball groove can be reduced. A circulation mechanism is not required, and a simpler structure can be achieved.

The present inventor has studied the ball screw mechanism according to the above-mentioned prior application in more detail. In the ball screw mechanism, in the ball screw mechanism, each ball groove does not rotate once around the outer circumference of the screw member or the inner circumference of the nut member. Therefore, it was not possible to apply pressurization, and therefore, it was found that there were the following problems.

That is, since the pressurizing cannot be applied in the ball screw mechanism, a gap is generated between the ball and the ball groove when the relative rotation between the screw member and the nut member is changed between the normal rotation and the reverse rotation. Responsiveness is reduced, and the position of the ball when torque is not loaded cannot be fixed, causing noise.Furthermore, the number of balls is limited to cope with noise reduction, and the screw member and The axial thickness of the nut member is limited.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems by providing a structure capable of applying a pressurization in a working force conversion mechanism having the ball screw mechanism as a structure. .

[0010]

SUMMARY OF THE INVENTION The present invention relates to an operating force converting mechanism. The operating force converting mechanism includes a screw member having a ball groove extending on the outer periphery and inclined in the circumferential direction, and a thread member inclined on the inner periphery in the circumferential direction. A nut member concentrically and relatively rotatably fitted to the outer periphery of the screw member having a ball groove extending therethrough, and a ball interposed between both ball grooves of the nut member and the screw member. This is an acting force conversion mechanism for converting a rotational force for relatively rotating the two members and an axial force for relatively moving the two members in the axial direction by the action of the ball groove.

Thus, in the acting force conversion mechanism according to the present invention, the screw member and the nut member have a plurality of ball grooves, and the lead angle of the ball groove in the screw member is equal to the track center line. The lead angle of the ball groove in the nut member and the track center line are set to different angles from each other.

Each of the ball grooves may be formed by forming each of the ball grooves of the screw member and the nut member with a part of a spiral groove, or by forming one of the ball members of the screw member and the nut member. The groove is formed by a part of a spiral groove, and the other one of the screw member and the nut member is formed by a part of a torus groove.

Further, the present invention is a driving force transmitting device using the above-mentioned acting force converting mechanism according to the present invention, wherein the driving force transmitting device comprises an outer rotating member and an inner rotating member which are coaxially and relatively rotatably positioned. A clutch mechanism disposed between rotating members and a pilot mechanism, wherein the acting force conversion mechanism is provided, and a rotational force as an input from the pilot mechanism is output as an axial force to the clutch mechanism side to output the clutch mechanism; Characterized in that the operation is controlled.

[0014]

In the acting force conversion mechanism according to the present invention, the track center line of the lead angle of each ball groove of the screw member and the track center line of the lead angle of each ball groove of the nut member are aligned. Since the angles are set to be different from each other, a pressure corresponding to a different angle difference acts on the balls in which the track center lines of the lead angles are interposed between the two ball grooves having different angles.

Therefore, according to the acting force conversion mechanism of the present invention, a gap is not generated between the ball and the ball groove even when the relative rotation between the screw member and the nut member is changed in the forward or reverse rotation direction. As a result, the responsiveness of the operation is good, and the position of the ball when the torque is not loaded is fixed, thereby preventing generation of noise. In addition, since it is not necessary to take any special means for preventing the generation of noise, the number of balls employed is not limited, and the axial thickness of the screw member and the nut member is limited. Not even.

In the working force conversion mechanism according to the present invention,
The track center line of the ball groove in the screw member and the track center line of the ball groove in the nut member can be configured to intersect at the axial center of the screw member and the nut member. Thus, when no load is applied to the acting force conversion mechanism, the ball is automatically centered and its position is fixed, the responsiveness of operation is further improved, and the generation of noise can be more effectively prevented. Further, with such a configuration, the operating force conversion mechanism can be made into a sub-assembly, and the assemblability to various devices such as a driving force transmitting device can be improved. In this case, it is preferable that the screw member and the nut member have the same dimension in the axial direction.

Further, according to the driving force transmission device of the present invention, due to the action force conversion mechanism, the responsiveness of the operation is good and the generation of noise is prevented. Further, since the acting force converting mechanism can be formed smaller in the axial direction and / or the radial direction than the cam mechanism employed as the acting force converting mechanism of the conventional driving force transmission device, the driving force can be reduced. The size of the transmission device can be reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 shows a driving force transmission device A according to an example of the present invention. The driving force transmission device A employs an operating force conversion mechanism B according to an example of the present invention, and FIG. 2 shows the operating force conversion mechanism B. As shown in FIG. 5, the driving force transmission device A is disposed in a driving force transmission path to the rear wheel side in a four-wheel drive vehicle based on front wheel driving, and transmits the driving force to the rear wheel side. Control.

In the four-wheel drive vehicle, the torrance axle 12 integrally includes a transmission, a transfer, and a front differential, and the driving force of the engine 11 is transmitted through the front differential 13 of the trans axle 12 to both axle shafts 1.
4a, 14a to drive the left and right front wheels 14b, 14b, and to the first propeller shaft 15 side. The first propeller shaft 15 is connected to the second propeller shaft 16 via the driving force transmission device A. When the first propeller shaft 15 and the second propeller shaft 16 are connected to transmit torque, the first propeller shaft 15 is driven. The force is transmitted to the rear differential 17, and from the rear differential 17, both axle shafts 18a, 18a
To drive the left and right rear wheels 18b, 18b.

The driving force transmitting device A is disposed between the first propeller shaft 15 and the second propeller shaft 16, and as shown in FIG. 1, the outer case 20a, the inner shaft 20b, and the main clutch mechanism 20c. , And a pilot clutch mechanism 20d, and an acting force conversion mechanism B according to an example of the present invention.

The outer case 20a constituting the driving force transmission device A is composed of a bottomed cylindrical housing 21a and a rear cover 21b screwed into the rear end opening of the housing 21a to cover the opening. I have. Housing 2
1a is formed of an aluminum alloy which is a non-magnetic material. The rear cover 21b is made of a magnetic material such as inner and outer cylindrical portions 21b1, 21b2 made of iron and both cylindrical portions 21b1, 21b2.
It is formed of a stainless steel intermediate cylinder portion 21b3 which is a non-magnetic material and is interposed and fixed by welding or the like.

The inner shaft 20b is connected to the rear cover 21
b is coaxially inserted into the housing 21a of the outer case 20a through the center portion of the housing 21a in a liquid-tight manner, and the housing 21a and the rear cover 21 are axially regulated.
b is rotatably supported. Inner shaft 20b
, The distal end of the second propeller shaft 16 is inserted and connected so as to transmit torque. The first end of the housing 21a constituting the outer case 20a is
The propeller shaft 15 is connected so as to be able to transmit torque.

The main clutch mechanism 20c is a wet-type multi-plate type friction clutch, and includes a large number of clutch plates (an inner clutch plate 22a, an outer clutch plate 22).
b) and is disposed on the inner wall side in the housing 21a. Each inner clutch plate 22a constituting the friction clutch is spline-fitted to the outer periphery of the inner shaft 20b and is assembled so as to be movable in the axial direction, and each outer clutch plate 22b is spline-fitted to the inner periphery of the housing 21a. It is mounted so as to be movable in the axial direction. The respective inner clutch plates 22a and the respective outer clutch plates 22b are alternately positioned, contact each other and frictionally engage with each other, and are separated from each other to be in a free state.

The pilot clutch mechanism 20d is an electromagnetic clutch, and includes an electromagnet 23, a friction clutch 24, an armature 25, and a yoke 26. The electromagnet 23 has an annular shape, and is fitted to the annular recess 21c of the rear cover 21b while being fitted to the yoke 26. The yoke 26 is rotatably mounted while maintaining a slight gap from the rear cover 21b.

The friction clutch 24 is a wet-type, multi-plate friction clutch composed of a plurality of outer clutch plates 24a and inner plates 24b. Each outer clutch plate 24a is spline-fitted to the inner periphery of the housing 21a and axially extends. The inner clutch plates 24b are movably mounted, and are spline-fitted to the outer periphery of a nut member 32 constituting an operating force conversion mechanism B described later, and are movably mounted in the axial direction.

The armature 25 has a ring shape, is spline-fitted to the inner periphery of the housing 21a, and is mounted so as to be movable in the axial direction.

The operating force conversion mechanism B is disposed between the main clutch mechanism 20c and the pilot clutch mechanism 20d, and is structurally a ball screw mechanism.
2, a screw member 31, a nut member 32, and a plurality of balls 33 are provided. Screw member 31
Has a spline 31b on the inner periphery of the ring-shaped main body 31a and four ball grooves 31c, 31d, 31 on the outer periphery of the ring-shaped main body 31a.
e, 31f. The nut member 32 has a ring shape, and has a spline 32b on the outer periphery of the ring-shaped main body 32a and four ball grooves 32c, 32d, 32e, 32f on the inner periphery of the ring-shaped main body 32a.

In the operating force conversion mechanism B, the screw member 31, the nut member 32, and the plurality of balls 33 are spline-fitted on the inner shaft 20b in a sub-assembly state in which they are assembled together. And is located on the rear side of the piston 27 that is spline-fitted on the inner shaft 20b behind the main clutch mechanism 20c. The inner clutch plate 24b of the friction clutch 24 that constitutes the pilot clutch mechanism 20d is spline-fitted to the spline 32b of the nut member 32.

In the driving force transmission device A thus configured, when the electromagnetic coil of the electromagnet 23 constituting the pilot clutch mechanism 20d is in a non-energized state, no magnetic path is formed, and the friction clutch 24 is not engaged. Are in a state of agreement. Therefore, the pilot clutch mechanism 20d is in a non-operating state, and in the operating force conversion mechanism B, the nut member 3
2 can rotate integrally with the screw member 31 via the ball 33, and the main clutch mechanism 20c is in a non-operating state. For this reason, the vehicle constitutes a first drive mode that is a two-wheel drive.

On the other hand, when power is supplied to the electromagnetic coil of the electromagnet 23, a magnetic path circulating around the electromagnet 23 is formed in the pilot clutch mechanism 20d, and
3 sucks the armature 25. For this reason, the armature 25 presses the friction clutch 24 to frictionally engage. As a result, pilot torque is generated in the pilot clutch mechanism 20d, and in the operating force conversion mechanism B, relative rotation occurs between the screw member 31 and the nut member 32, and the ball 33 and the ball grooves 31c, 32c, Ball grooves 31d and 32d, ball 33 and ball grooves 31e and 32
e, the screw member 31 and the nut member 32 are relatively moved in the axial direction by the action of the ball 33 and the ball grooves 31f and 32f.

By the relative movement of the screw member 31 and the nut member 32 in the axial direction, the piston 27 is pushed by one of the screw member 31 and the nut member 32, and the main clutch mechanism 20c is moved by the frictional engagement force of the friction clutch 24. , And the torque is generated between the outer case 20a and the inner shaft 20b. This allows
The vehicle constitutes a second drive mode in which the first propeller shaft 15 and the second propeller shaft 16 are four-wheel drive between the non-directly connected state and the directly connected state. In this driving mode, the driving force distribution ratio between the front and rear wheels is set to 10 in accordance with the running state of the vehicle.
Control can be performed in a range of 0: 0 (two-wheel drive state) to 50:50 (direct connection state).

When the current flowing through the electromagnetic coil of the electromagnet 23 is increased to a predetermined value, the attraction force of the electromagnet 23 to the armature 25 increases, and the armature 25 is strongly attracted to increase the frictional engagement force of the friction clutch 24. , The relative movement between the nut member 32 and the screw member 31 is increased.
As a result, the pressing force on one of the piston 27 of the screw member 31 and the nut member 32 is increased, and the main clutch mechanism 20c is brought into the coupled state. For this reason,
The vehicle constitutes a third drive mode in which the first propeller shaft 15 and the second propeller shaft 16 are four-wheel drive in a directly connected state.

The pressing member against the piston 27 when the operation force conversion mechanism B is operated is either the screw member 31 or the nut member 32. The pressing member differs depending on the rotation direction of the relative rotation between the screw member 31 and the nut member 32. ,
For example, when the relative rotation of the two members 31 and 32 is in the forward direction, the screw member 31 moves toward the piston 27 and presses the piston 27, and the relative rotation of the two members 31 and 32 is in the reverse direction. In some cases, the nut member 32 is
7 to push the piston 27.

In the working force conversion mechanism B,
Each ball groove 31c of the screw member 31 and the nut member 32
To 31f and each of the ball grooves 32c to 32f are formed by a part of a spiral groove, and the two ball grooves 3 opposed to each other are formed.
1c, 32c, both ball grooves 31d, 32d, both ball grooves 31e, 32e, and both ball grooves 31f, 32f form a pair. As shown in FIG. 2 and FIG. 3, three balls 33 are interposed in both ball grooves of each pair.
The three balls 33 forming a pair are interposed in both ball grooves of the same pair, and the group of balls 33 of each pair is interposed in both ball grooves of a different pair.

FIGS. 3A and 3B schematically show a part (part of the pair of ball grooves 31c and 32c) of the acting force conversion mechanism B. FIG. 3A is a schematic partial plan view, and FIG. ) Is the figure (a)
Is a schematic cross-sectional view in the direction of arrow bb, and FIG. 4C is a schematic cross-sectional view in the direction of arrow cc in FIG. 3A. The preload generation mechanism will be described based on these drawings. .

In FIG. 3, L1 is a center line passing through the centers of the three balls 33 (lead angle θ: referred to as a reference track center line), whereas L1 is a track center of the ball groove 31c in the screw member 31. Line L2 is the lead angle (θ-
α), and the track center line L3 of the ball groove 32c in the nut member 32 is set to the lead angle (θ + α). Thereby, both ball grooves 31c, 32
Each ball groove 31c, 3
A force in the direction of the arrow to be pushed to the center of 2c acts, and this force acts as a preload on the ball 33 in total.
This preload generation mechanism is based on the other ball groove pairs 31d, 3
The same applies to 2d, 31e, 32e, 31f, and 32f, and a preload is applied to the balls 33 interposed in all the ball groove pairs.

In the acting force conversion mechanism B thus configured, each of the ball grooves 31c to 31c of the screw member 31 is provided.
Since the track center line L2 of f and the track center line L3 of each of the ball grooves 32c to 32f of the nut member 32 are set to different lead angles (θ−α) and (θ + α), each ball groove pair 31c, 32c to 31f, 32
Is applied to the ball 33 interposed between the balls 33 according to different angle differences.

For this reason, according to the acting force conversion mechanism B, even when the relative rotation between the screw member 31 and the nut member 32 is changed to the normal rotation or the reverse rotation, the ball 33 and each of the ball groove pairs 31c, 32c to 31f are changed. , 32f, and the response of the operation is good, and the position of the ball 33 when no torque is applied is fixed, thereby preventing generation of noise. In addition, since it is not necessary to take any special means for preventing the generation of noise, the number of balls 33 to be employed is not limited, and the axial thickness of the screw member 31 and the nut member 32 is limited. There is no such thing.

In the acting force conversion mechanism B,
Track center line L2 of ball grooves 31c to 31f in screw member 31 and ball groove 32c in nut member 32
Since the center line L3 of the track member 32 to 32f intersects at the axial center of the screw member 31 and the nut member 32, when the acting force conversion mechanism B is not loaded,
The ball 33 is automatically centered and the position is fixed, the responsiveness of the operation is further improved, and the generation of noise can be more effectively prevented. Further, with such a configuration, the operating force conversion mechanism B can be made into a sub-assembly, and the assembling property to various devices such as the driving force transmitting device A is improved.

In the acting force conversion mechanism B, each ball 33 and each ball groove pair 31c, 32c to 31f, 32f
In consideration of the reaction force generated by the pressurization between the ball groove pairs, it is preferable that each ball groove pair 31c, 32c to 31f, 32f be an even number of four or more lines. 31c, 32c to 31f, 32f are set to four.

FIG. 4 shows that the acting force conversion mechanism B is
5 schematically shows a state in which a preload applying means different from the preload applying means shown in FIG. In the preload applying means, the relationship between the track center line L2 of the ball grooves 31c to 31f in the screw member 31 and the track center line L3 of the ball grooves 32c to 32f in the nut member 32 paired with the ball grooves 31c to 31f. , The first pair of both ball grooves 31
c, 32c (c), one of the track center lines L1
, The other track center line L2 is deviated toward the increasing side (counterclockwise arrow +), and in the second pair of ball grooves 31d and 32d (d) adjacent thereto, one of the track center lines L2 is As a reference, the other track center line L3 is deviated toward the decreasing side (clockwise arrow-), and in the third pair of both ball grooves 31e and 32e (e) adjacent thereto, one of the track center lines L2 is used as a reference. The other track center line L3
Is deviated to the increasing side (counterclockwise arrow +), and the fourth pair of ball grooves 31f and 32f (f) adjacent to the fourth pair of the ball grooves 31f and 32f (f) have the other with respect to the track center line L2 at any lead angle Of the track center line L3 is deviated to the decreasing side (clockwise arrow-).

In the acting force conversion mechanism B thus configured, the ball grooves 31c to 31c of the screw member 31 are provided.
Since the track center line L2 of f and the track center line L3 of each of the ball grooves 32c to 32f of the nut member 32 are set to different lead angles, the pair of ball grooves 31c, 32c to 31f, having different lead angles. A pressurization according to the lead angle difference is applied to the ball 33 interposed between 32f. For this reason, the same operation and effect as when the preload applying means shown in FIG. 3 is employed, but also the following operation and effect are obtained.

That is, in the acting force conversion mechanism B, as schematically shown in FIG. 4, a pressurization is applied to each ball 33 as shown by a thin arrow, and a pressure is applied between each ball 33 group. Then, opposing reaction forces are generated as indicated by thick arrows. In this case, in the acting force conversion mechanism B, the track center line L2 of the ball grooves 31c to 31f in the screw member 31 and the track center line of the ball grooves 32c to 32f in the nut member 32 paired with the ball grooves 31c to 31f. The relationship between L3 and the first pair of ball grooves 31
c, 32c (c), one of the track center lines L2
, The other track center line L3 is deviated toward the increasing side (counterclockwise arrow), and the second pair of ball grooves 31d and 32d (d) adjacent to the other track center line L3 is referenced to one of the track center lines L2. The other track center line L3 is deviated toward the decreasing side (clockwise arrow), and the third pair of ball grooves 31e and 32e (e) adjacent to the other track center line L3 is deviated based on one of the track center lines L2. The track center line L3 is deviated to the increasing side (counterclockwise arrow), and the fourth pair of ball grooves 31f, 32f (f) adjacent to the track center line L3 has the other one based on one of the track center lines L2. The track center line L3 is deviated toward the decreasing side (clockwise arrow).

Therefore, between the groups of adjacent pairs of balls 33, a small reaction force opposing each other between (c) and (d), and a large reaction force opposing each other between (d) and (e) becomes ( e) and (f) have small reaction forces opposite to each other,
A large reaction force opposing each other is generated between (f) and (c), and there is an advantage that the binding force of the ball 33 group as a whole increases.

In the operating force conversion mechanism B,
One ball groove of the screw member 31 and the nut member 32 is constituted by a part of a spiral groove, and the other ball groove of the screw member 31 and the nut member 32 is constituted by a part of a torus groove. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view of a driving force transmission device according to an example of the present invention.

FIG. 2 is a partially cutaway perspective view of an operating force conversion mechanism according to an example of the present invention, which constitutes the driving force transmission device.

FIG. 3 is a schematic diagram for explaining a mechanism of generating a pressurization applied to a ball when one pressurizing application means is employed in the operating force conversion mechanism, and FIG. FIG. 2B is a partial plan view, FIG. 2B is a schematic cross-sectional view in the direction of arrow bb in FIG. 2A, and FIG.
It is a typical sectional view of the c direction.

FIG. 4 is a schematic side view for explaining the generation of pressurization applied to a ball when another pressurizing means is employed in the operating force conversion mechanism, and a mechanism of reaction force generation caused by the pressurization. FIG.

FIG. 5 is a schematic configuration diagram of a vehicle equipped with the driving force transmission device.

[Explanation of symbols]

A: drive power transmission device, B: operating force conversion mechanism, L1: track reference line, L2, L3: track center line, 11: engine, 12: torrance axle, 13: front differential, 14a: axle shaft, 14b ... Front wheel, 15 First propeller shaft, 16 Second propeller shaft, 17 Rear differential, 18a Axle shaft, 18b Rear wheel, 20a Outer case, 20b Inner shaft, 20c Main clutch mechanism, 20d Pilot Clutch mechanism, 21a ... housing, 21b ... rear cover, 21b1 ... inner cylinder part, 2
1b2: outer cylindrical portion, 21b3: intermediate cylindrical portion, 21c: annular recess, 22a: inner clutch plate, 22b: outer clutch plate, 23: electromagnet, 24: friction clutch, 24a: outer clutch plate, 24b: inner plate, 25 ... armature, 26 ... yoke, 27 ... piston, 31 ... screw member, 31a ... ring-shaped main body, 31
b ... spline, 31c, 31d, 31e, 31f ... ball groove, 32 ..., nut member, 32a ... ring-shaped body,
32b: Spline, 32c, 32d, 32e, 32f
... ball groove, 33 ... ball.

Claims (6)

[Claims] 1. A screw member having a ball groove extending in a circumferential direction on an outer periphery and a ball groove extending in a circumferential direction on an inner periphery so as to be concentric and relatively rotatable around the outer periphery of the screw member. A nut member to be fitted, a ball interposed between the ball grooves of the nut member and the screw member, and a rotational force for relatively rotating the two members by the action of the ball and the ball groove; The screw member and the nut member have a plurality of ball grooves, and a track of the lead angle of the ball groove in the screw member. An acting force conversion mechanism, wherein a center line and a track center line of a lead angle of a ball groove in the nut member are set at mutually different angles. 2. The force conversion mechanism according to claim 1, wherein the track center line of the ball groove in the screw member and the track center line of the ball groove in the nut member are in the axial direction of the screw member and the nut member. A force conversion mechanism characterized by intersecting at the center of the body. 3. The force conversion mechanism according to claim 1, wherein each ball groove of said screw member and said nut member is constituted by a part of a spiral groove. Alternatively, an action force conversion mechanism characterized by a plurality of balls interposed. 4. The force conversion mechanism according to claim 1, wherein one of the ball grooves of the screw member and the nut member is formed of a part of a spiral groove, and
The ball groove of the other of the screw member and the nut member is constituted by a part of a torus-shaped groove, and one or more balls are interposed in each of the ball grooves. Conversion mechanism. 5. The acting force conversion mechanism according to claim 1, wherein said screw member and said nut member have the same axial dimension. 6. An outer rotary member and an inner rotary member which are coaxial and relatively rotatable relative to each other in a driving force transmitting device using the acting force converting mechanism according to claim 1, 2, 3 or 4. The acting force conversion mechanism is disposed between a clutch mechanism and a pilot mechanism disposed therebetween, and a rotational force as an input from the pilot mechanism is output as an axial force to the clutch mechanism side to operate the clutch mechanism. A driving force transmission device characterized in that the driving force transmission device is configured to control the driving force.