JP2002357258A - Ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw capable of being appropriately lubricated for a long time of period without increasing the driving torque. SOLUTION: A plurality of balls 4 are housed to be freely rotatable in the spiral circulative passage 9 formed between screw grooves 7, 8 of the screw shaft 2 and a nut 3. An oiler 5 supplying a lubricant to the circulative passage 9 is arranged at the end of the nut 3. The oiler 5 is formed of an oil reservoir 11, a recession 12, and an oil transfer ball 14. The oil reservoir 11 is loosely fitted on the outer periphery of the screw shaft 2 with a specified radial gap. The recession 12 is formed in the inner diameter part of the oil reservoir 11 to communicate with the oil reservoir. The oil transfer ball 14 is housed to be freely rotatable between the recession 12 and the screw groove 7 of the screw shaft 2 and the lubricant of the oil reservoir 11 is transferred to the screw groove 7 through the ball 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw used for various devices.

[0002]

2. Description of the Related Art A ball screw is used as a device for converting a rotary motion into a linear motion, as a table feed of a machine tool, a transfer device, or a replacement part of a hydraulic or pneumatic actuator. In the ball screw structure, an infinitely circulating ball is interposed between the screw shaft and the thread groove of the nut, one is rotatably supported, the other is not rotatable, and the rotatable part is rotated to interpose. This is a linear motion device in which an infinitely circulating ball revolves and a non-rotatable portion moves linearly. In this ball screw, lubrication such as oil and grease is regularly supplied to the thread groove formed on the shaft and nut and the revolving ball, so that wear is reduced and smooth operation with less friction loss is achieved. Will be possible. Failure to do so will result in abnormal heat and wear, which will lead to early damage to the ball screw. Therefore, it is usually necessary to perform maintenance such as installing an automatic lubrication / lubrication device, or wiping old grease and enclosing new grease.

Further, lubrication of a screw shaft by applying a lubricant supply component directly to the screw shaft and applying the lubricant is described as follows.
JP-B-58-33325, JP-A-8-12147
4, JP-A-11-303866, JP-A-20
There is one disclosed in, for example, JP-A-00-249209.
In any of these, a coating material formed of a porous material such as a sponge or a material in which a large number of fibers such as felt are entangled and solidified is directly brought into sliding contact with a screw shaft.

However, in such a lubricating structure, there are concerns about the following problems. i) The lubricant is applied to the uncoated body more than necessary. ii) When the rotation speed of the screw shaft increases, the amount of coating becomes insufficient. iii) Since the applied body and the non-applied body are in sliding frictional contact, the applied body contact portion is worn, and proper lubrication cannot be performed. iv) Since the application body is in sliding contact and surface contact with the screw shaft, the frictional resistance increases and the driving torque of the ball screw increases.

An object of the present invention is to provide a ball screw capable of performing proper lubrication for a long period of time without increasing the driving torque.

[0006]

A ball screw according to the present invention has a screw shaft having a spiral screw groove formed on an outer diameter surface, and a spiral screw which is loosely fitted on the outer periphery of the screw shaft and faces the screw groove. A nut having a threaded groove formed on the inner diameter surface thereof; a plurality of balls rotatably accommodated in a helical circulation path formed between the screw shaft and the threaded groove of the nut; and an end of the nut. A ball screw provided with an oil supply unit for supplying a lubricant to the circulation path, wherein the oil supply unit is loosely fitted to the outer periphery of the screw shaft with a predetermined radial clearance, An oil storage portion attached to the end of the nut to store the lubricant, a recess provided in the inner diameter portion of the oil storage portion and communicating with the oil storage portion, and a gap between the recess and the thread groove of the screw shaft. And a ball which is rotatably accommodated in the oil reservoir through the ball. Lubricant is characterized in that so as to be transferred to the screw groove. According to this configuration, the lubricant contained in the oil storage portion is transferred to the ball by the ball accommodated in the recess communicating with the oil storage portion rotating with the rotation of the screw shaft, and further transferred from the ball to the screw shaft. Is done. As described above, since the ball to which the lubricant is transferred rotates by itself, wear due to sliding friction does not occur. Since this ball is in rolling contact with the screw axis and in point contact,
The frictional resistance is smaller than in the sliding contact, so that an increase in the driving torque of the ball screw can be suppressed. In addition, since the ball rotates by the rotation of the screw shaft, the relative speed at the contact portion is reduced, and stable transfer of the lubricant can be performed even at high speed rotation. Since the lubricant is transferred by the ball rolling into the thread groove, the transfer position of the lubricant in the thread groove is almost the same as the position where the circulating ball for driving transmission contacts the thread groove. Is not transferred. Further, since the lubricant can be stored in the oil storage portion different from the member that is in contact with the screw shaft, the storage amount of the lubricant can be increased. Therefore, appropriate lubrication can be stably performed over a long period of time. Therefore, long-term lubrication-free maintenance of the ball screw is achieved.

In the present invention, a ball holding member made of an oil-impregnated body having elasticity may be accommodated in the recess, and the ball may be pressed against the thread groove by the ball holding member. In such a configuration, the interposition of the oil-impregnated ball holding member makes it possible to stabilize the supply, make the supply of the lubricant stable, and reduce Supply becomes possible. In addition, since the ball accommodated in the recess is pressed by the elasticity of the ball holding member and constantly comes into contact with the ball groove of the screw shaft, there is no problem such as generation of vibration, and the transfer of the lubricant from the ball to the screw groove is also prevented. It will be done reliably.

In the present invention, the oil reservoir may be formed of an oil-containing body. When the oil storage section is an oil-containing body, handleability such as supply of a lubricant to the oil storage section is better than that of the oil storage section of the hollow container.

In the present invention, the ball may be held in the recess by point contact. In the case of the point contact, the frictional resistance of the ball against the inner surface of the recess is reduced, and the increase in the driving torque is further suppressed.

[0010] In the present invention, the recess and the oil reservoir may be communicated with each other through a plurality of slits. Providing a plurality of slits in this way improves the transfer efficiency of the lubricant from the oil reservoir to the ball.

[0011]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. As shown in a perspective view in FIG. 1, the ball screw 1 has a screw shaft 2 having a spiral screw groove 7 formed on an outer diameter surface, and is loosely fitted on the outer periphery of the screw shaft 2, and is fitted into the screw groove 7. A nut 3 having a helical screw groove 8 (FIG. 2) facing the inner surface of the nut 3, the screw shaft 2 and the nut 3
And a plurality of balls 4 rotatably accommodated in a spiral circulation path 9 (FIG. 2) formed between the screw grooves 7 and 8. The nut 3 is provided with a ball reversing section 6, and by connecting the ball reversing section 6 to the spiral circulation path 9, a series of infinitely circulating ball tracks is formed. In this example, the ball reversing section 6 uses a return tube 13 through which the ball 4 can pass. However, the ball reversing section 6 may be of a top type or an end plate type. In the ball screw having such a basic configuration, an oil supply unit 5 that supplies a lubricant to the circulation path 9 is provided at an end of the nut 3. The oil supply units 5 are provided at both ends of the nut 3.

As shown in FIG. 2, the oil supply section 4 is provided at an oil storage section 11 which is loosely fitted to the outer periphery of the screw shaft 2 with a predetermined radial clearance, and is provided at an inner diameter section of the oil storage section 11. A recess 12 communicating with the oil reservoir 11, and the recess 12 and the screw shaft 2
And an oil transfer ball 14 rotatably accommodated between the thread grooves 7. Through this ball 14, the oil reservoir 1
One lubricant is transferred to the thread groove 7 of the screw shaft 2. The oil storage section 11 is provided at the end of the nut 3 with a fixing tool 10 such as a bolt (FIG. 3).
(A)).

The oil storage section 11 is formed of a ring-shaped hollow container concentric with the nut 3, and has a lubricant storage space 11a provided in a part in the circumferential direction. In this embodiment, the screw shaft 2 is used in a horizontal posture as a member on the rotation side, and the storage space 11a is disposed at a position above the screw shaft 2. A recess 12 for accommodating the ball 14 is provided below the storage space 11a. The lubricant storage space 11a and the recess 12
The balls 14 communicate with each other through a communication path 15 having a hole diameter sufficiently smaller than the diameter of the balls 14. As the lubricant, grease having high fluidity may be used in addition to the lubricating oil. The recess 12 in which the ball 14 is housed is formed in a conical shape that opens downward, and is in line contact with the ball 14.
Therefore, as a member forming the recess 12, the ball 1
It is desirable to use a material different from that of No. 4, especially a member excellent in self-sliding action.

According to the ball screw 1 having this configuration, the ball 14 housed in the recess 12 rotates in the oil supply unit 5 so as not to deviate from the screw groove orbit in accordance with the rotation of the screw shaft 2. The recess 12 is in communication with the oil reservoir 11, and the lubricant of the oil reservoir 11 is transferred to the ball 14 by the rotation of the ball 14, and further transferred from the ball 14 to the thread groove 7 of the screw shaft 2. Thereby, the lubricant in the oil storage section 11 is transferred to the thread groove 7 of the screw shaft 2. In this case, the ball 14 is kept in a state of being constantly in contact with the screw groove 7 of the screw shaft 2 by its own weight, so that the ball 14 surely rotates with the rotation of the screw shaft 2. Since the oil storage section 11 is not open to the atmosphere except for the communication path 15 of the recess 12 in which the ball 14 is accommodated, the lubricant does not drop from the communication path 15 by its own weight, and Will be retained. Then, as the ball 14 rotates, a small amount of the lubricant present on the hole surface is transferred to the inner surface of the thread groove 7 via the rotation ball 14.

A ball 4 circulating through a series of infinitely circulating ball trajectories in the ball screw 1 and a ball 14 for oil transfer
Means that the lubricant is in contact with the thread groove 7 of the screw shaft 2 in almost the same arrangement, so that more lubricant than necessary is not transferred. Further, since the ball 14 rotates by the rotation of the screw shaft 2, the relative speed between the ball 14 and the screw groove 7 at the contact portion with the screw groove 7 is reduced, and stable transfer of the lubricant can be performed even at high speed rotation. Further, since the ball 14 is rotating (rolling), wear due to sliding friction does not occur. Furthermore, since the contact portion of the ball 14 with the thread groove 7 is in rolling contact and point contact, the frictional resistance is smaller than in sliding contact, and the driving torque of the ball screw 1 does not increase. Thus, according to the ball screw 1, appropriate lubrication can be performed for a long period of time without increasing the driving torque.

In the first embodiment, the communication path 15 for communicating the recess 12 and the oil storage section 11 is
Instead of the round hole, a plurality of slits 30 may be provided as shown in FIG. The slits 30 are provided radially, for example. In this way, the plurality of slits 3
By providing 0, the opening of the communication path 15 can be opposed to a wide range of the outer surface of the ball 14 without increasing the opening area in the recess 12. As a result, the transfer of the lubricant from the recess 12 to the ball 14 can be performed without bias.

In the first embodiment, FIG.
One or more slits 31 extending radially from the opening of the communication path 15 may be formed on the surface of the recess 12 as shown in FIG. The slit 31 may have a bottomed shape, that is, a groove shape. When the slit 31 is provided in this manner, the lubricant held at the opening of the communication path 15 of the recess 12 is held over the slit 31, and the lubricant from the recess 12 to the ball 14 is Transferability is improved.

FIGS. 4 and 5 show another embodiment of the present invention. The ball screw 1 of this embodiment accommodates a ball holding member 16 made of an elastic oil-impregnated body in the recess 12 of the first embodiment.
The ball 14 is screwed into the thread groove 7 of the screw shaft 2 by the elastic restoring force of
Pressed against. The recess 12 is a through hole that opens directly into the storage space 11a of the oil storage unit 11 without passing through the small-diameter communication passage 15 in the first embodiment. The ball holding member 16 forms the bottom surface of the recess 12 by being housed in the recess 12. In addition, the bottom surface of the recess 12 referred to here is the ceiling surface of the recess 12 when the vertical relationship is distinguished. The ball 14 is held in a state of point contact with the recess 12. Strictly speaking, this contact point is a contact surface having a certain area due to the elastic deformation of the concave shape accompanying the pressing of the ball 14 by the ball holding member 16. The ball holding member 16 may simply form only the bottom surface of the concave portion 12, but in this example, the ball holding member 1
Reference numeral 6 denotes a cup in which the ball 14 fits.
The cylindrical peripheral wall portion 16a of the ball holding member 16
Is fitted to the inner peripheral surface of the recess 12. Ball holding member 16
Is preferably formed of a porous elastic member such as a sponge, or a fiber entangled elastic material such as a felt.
Other configurations in this embodiment are shown in FIGS.
This is the same as the first embodiment shown in FIG.

In the case of this embodiment, the lubricant in the oil reservoir 11 penetrates and is held by the ball holding member 16 accommodated in the recess 12. Therefore, the lubricant held by the ball holding member 16 is transferred to the ball 14 by the rotation of the ball 14 accompanying the rotation of the screw shaft 2, and further transferred from the ball 14 to the thread groove 7 of the screw shaft 2. . In this case, when the screw shaft 2 rotates clockwise as shown in FIG. 6A, the ball 14 rotates counterclockwise and the screw shaft 2 rotates.
The ball 14 moves in the direction of rotation,
Since the lubricant is pressed against the peripheral wall portion 16 a of the ball holding member 16, the lubricant of the ball holding member 16 is reliably transferred to the ball 14. When the screw shaft 2 rotates counterclockwise as shown in FIG. 6B, the ball 14 rotates clockwise and the ball 14 moves in the direction of rotation by the rotation of the screw shaft 2. Is pressed against the peripheral wall portion 16 a on the opposite side of the ball holding member 16, so that the lubricant of the ball holding member 16 is reliably transferred to the ball 14. This allows
Transferability of lubricant is increased.

In this embodiment, since the ball 14 is always kept elastically pressed against the thread groove 7 of the screw shaft 2 by the ball holding member 16, the ball 14 is rotated with the rotation of the screw shaft 2. Will surely rotate, and the transfer of the lubricant from the ball 14 to the thread groove 7 will be surely performed, and more appropriate lubrication can be performed. Also, since the ball 14 is held in the recess 12 by point contact,
The frictional resistance of the ball 14 with respect to the recess 12 is reduced, so that the ball 14 rotates smoothly, and the effect of suppressing an increase in driving torque and the effect of transferring the lubricant are improved.

FIG. 7 and FIG. 8 show still another embodiment of the present invention. The ball screw 1 according to this embodiment has a structure shown in FIG.
The oil storage section 11 in the first embodiment shown in FIGS. Specifically, the oil storage unit 11
Are filled with the oil-containing body 11b in the storage space 11a. The recess 12 for holding the ball 14 is also integrally formed in the oil impregnated body 11b. In this embodiment, the storage space 11a filled with the oil-containing body 11b is the same as that shown in FIG.
Are provided over the entire circumference surrounding the screw shaft 2 as shown in FIG. The oil impregnated body 11b is desirably formed of a porous elastic member such as sponge, or a fiber entangled elastic material such as felt. The fact that the recess 12 is provided at a position above the screw shaft 2 and other configurations are described in FIG.
3 to the first embodiment shown in FIG.

In this embodiment, since the oil storage section 11 is formed by the oil-containing body 11b, excessive lubricant is not supplied from the oil storage section 11 to the thread groove 7 through the ball 14, and furthermore, Easy to perform micro lubrication. Further, since the recess 12 for holding the ball 14 is formed integrally with the oil-containing body 11b, the function of holding and supplying the lubricant can be performed by one member, and the configuration of the oil supply unit 5 is simplified. it can.

In each of the above embodiments, the ball 14 for transferring the lubricating oil and the recess 12 for holding the lubricating oil are provided at one place in the circumferential direction. However, the ball 14 and the recess 12 are arranged in the circumferential direction. It may be arranged at a plurality of distant places. Further, the oil storage section 11 is not limited to one provided in one circumferential position as in the first embodiment, or one provided in the entire circumference as in the example of FIG. When installing, nut 3
Can be of various shapes and arrangements according to various installation forms, such as when the is used as a rotating member.

[0024]

According to the ball screw of the present invention, an oil supply portion for supplying a lubricant to a ball circulation path formed between a screw shaft and a thread groove of a nut is provided at an end of the nut. A part is loosely fitted to the outer periphery of the screw shaft with a predetermined radial clearance, is attached to an end of the nut and stores a lubricant, and is provided at an inner diameter part of the oil storage part. A recess communicating with the oil reservoir, and a ball rotatably accommodated between the recess and the thread groove of the screw shaft. The lubricant of the oil reservoir is threaded through the ball through the recess. Therefore, appropriate lubrication can be performed for a long period of time without increasing the driving torque. In the recess, a ball holding member made of an oil-impregnated body having elasticity is housed, and by this ball holding member,
When the ball is pressed against the thread groove, the lubricant can be supplied more stably. When the oil storage section is formed of an oil-containing body, the handling property such as the supply of a lubricant is improved. When it is assumed that the ball is held in the recess by point contact, the frictional resistance of the ball to the recess is reduced, and the effect of suppressing an increase in driving torque is improved. When the recess and the oil reservoir communicate with each other through a plurality of slits, the transfer efficiency of the lubricant from the oil reservoir to the ball is improved, and uneven lubrication can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a ball screw according to a first embodiment of the present invention.

FIG. 2 is a half sectional view of the ball screw.

FIG. 3A is a side view of the ball screw, and FIGS.
(C) is a partial enlarged side view which shows the modification of the vicinity of the recessed part in the same ball screw.

FIG. 4 is a half sectional view of a ball screw according to another embodiment of the present invention.

FIG. 5 is a side view of the ball screw.

FIG. 6 is an explanatory diagram of an operation of an oil supply unit in the ball screw.

FIG. 7 is a half sectional view of a ball screw according to still another embodiment of the present invention.

FIG. 8 is a side view of the ball screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 ... Screw shaft 3 ... Nut 4 ... Ball 5 ... Oil supply part 7,8 ... Screw groove 9 ... Circulation path 11 ... Oil storage part 11b ... Oil-containing body 12 ... Concave part 14 ... Oil transfer ball 15 ... Communication path 16 ... Ball holding member

Claims (5)

[Claims] 1. A screw shaft having a spiral screw groove formed on an outer diameter surface thereof, and a spiral screw groove which is loosely fitted on an outer periphery of the screw shaft and faces the screw groove is formed on an inner diameter surface. A nut, a plurality of balls rotatably housed in a helical circulation path formed between the screw shaft and the thread groove of the nut, and a ball disposed at an end of the nut; The oil supply section is loosely fitted to the outer circumference of the screw shaft with a predetermined radial clearance, and is attached to an end of the nut to supply a lubricant. An oil storage portion to be stored, a recess provided in the inner diameter portion of the oil storage portion and communicating with the oil storage portion, and a ball rotatably housed between the recess and the screw groove of the screw shaft. The lubricant in the oil reservoir is transferred to the thread groove via this ball. Ball screw and said. 2. The ball screw according to claim 1, wherein a ball holding member made of an oil-impregnated body having elasticity is accommodated in the recess, and the ball is pressed against the thread groove by the ball holding member. 3. The ball screw according to claim 1, wherein the oil reservoir is formed of an oil-containing body. 4. The ball screw according to claim 1, wherein the ball is held in the recess by point contact. 5. The ball screw according to claim 1, wherein the recess and the oil reservoir communicate with each other through a plurality of slits.