Patent Publication Number: US-2005126323-A1

Title: Hypoid geared motor and connection structure between motor pinion and hypoid pinion

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a hypoid geared motor, and in particular, to a hypoid geared motor having an advantage in a connection structure between a motor pinion which is formed on a motor shaft and a hypoid pinion.  
      2. Description of the Related Art  
      A hypoid gear set comprising a hypoid pinion and a hypoid gear is incorporated into a driving device as a so-called orthogonal transformation mechanism because it can change a direction of a rotating shaft to be at a right angle.  
      The orthogonal transformation mechanism constituted by the hypoid gear set is advantageous in that a device incorporating the gear set can be downsized. The orthogonal transformation mechanism is also more efficient than a worm gear set having similar functions and can be driven at a lower noise with a smaller vibration as compared with a bevel gear set. In addition, its only one-stage structure can ensure a high reduction ratio. Therefore, there is a strong need for the orthogonal transformation mechanism constituted by the hypoid gear set in a specific field.  
      On the other hand, in order to respond to production at a small amount for a variety of types in recent years, in each factory or the like such a structure that each machine can be independently driven on the spot is more and more desired so as to satisfy a request for driving a necessary machine only for necessary time. Therefore, there is an increasing need of a so-called “geared motor” constituted by integrally assembling a gear box housing a reduction mechanism therein and a motor so as to obtain an output whose torque and speed of rotation are regulated to be optimal by itself.  
      For gear boxes used as geared motors, gear mechanisms with parallel axes or bevel gear mechanisms are overwhelmingly dominating in terms of number for the reason of cost. Thus, in response to such a phenomenon, a large number of motors with pinions are shipped. In such a motor with a pinion, a spur pinion or a helical pinion is formed on a motor shaft in advance so that the motor shaft also serves for the functions of the first stage (an input shaft) of a reduction gear.  
      As described above, in the recent factories, “modification” is frequently carried out to realize the fabrication of various kinds of products at a small amount; for example, the mechanical facilities or the conveyance facilities in a factory are recombined, a torque or conveying speed is changed to be more appropriate, or the like. Therefore, for example, in a machine using a pair gear mechanism with parallel axes up to now, there quite often arises the need of transforming a direction of rotation of an output shaft to a direction at a right angle.  
      As a geared motor capable of transforming a direction of rotation of an output shaft to a direction at a right angle, for example, a hypoid geared motor as disclosed in Japanese Patent Laid-Open Publication No. 2001-74110 has been known. Therefore, in the case described above, a technique of replacing a geared motor with such a hypoid geared motor is used.  
      The “geared motor” is merely one component when, for example, the entire conveyance system is considered. Therefore, one of its great advantages is that the specifications of the entire device can be changed only by replacing the component. In this regard, it can be said that the geared motor has been positioned merely as the “minimum unit component” in the system.  
      The geared motors are roughly classified into parallel axis type and orthogonal axis type. Because of the above-described background, the parallel axis type and the orthogonal axis type are conventionally almost fully separated from each other for fabrication as well as for sales in the actual conditions. For example, a motor including a parallel axis type spur pinion or helical pinion formed on a tip of its motor shaft is always used in combination with a parallel axis type gear box. Thus, there was not idea of using it as an orthogonal axis type motor.  
     SUMMARY OF THE INVENTION  
      The present invention focuses attention on the potentially existing problems under the above-described background so as to solve the problem with an innovative idea. In view of the foregoing problems, various exemplary embodiments of this invention provide a hypoid geared motor allowing the use of a motor with a pinion, which should otherwise be used in combination with a parallel axis type gear box, as a motor of a geared motor having a hypoid gear set as well as the continuous use of the motor that is already in use as much as possible (without disposal thereof) at relocation or the like, for example, in an existing facility as described below.  
      In addition, various exemplary embodiments of this invention provide an efficient connection structure between a motor pinion and a hypoid pinion.  
      In order to achieve the above objects, a hypoid geared motor according to one of exemplary embodiments of the invention comprises: a motor having a motor shaft with a motor pinion formed on the motor shaft; a hypoid gear box having a hypoid pinion, the hypoid pinion being engageable with an outer circumference of the motor pinion at an end portion of a motor side thereof; and a friction clamp formed on the end potion, the friction clamp connecting the hypoid pinion and the motor pinion by friction clamping.  
      In the exemplary embodiments of the present invention, a “motor with a pinion” including a pinion formed on a tip of its motor shaft, which was never conventionally considered to be used as a motor of a hypoid geared motor, can be used as a motor of a hypoid geared motor. As a result, the present invention paves the way to more effectively use a large amount of motors with pinions which are stocked at a manufacturer, or motors with pinions which are actually working at each factory or the like (described below).  
      In the exemplary embodiments of the present invention, as a specific structure for realizing it, a friction clamp is formed on an end of the hypoid pinion on the motor side. The friction clamp connects the hypoid pinion and the motor pinion by friction clamping so that the motor pinion on the motor side and the hypoid pinion on the gear box side are directly connected with each other by friction clamping.  
      Since the connection is achieved by the friction clamping, the two members are connected while being perfectly in close contact with each other and secured. As a result, there is no possibility of generating an impact noise at the joint portion even if the amount of an axial load, which is inevitably generated in view of the nature of the hypoid pinion, varies or a direction in which the axial load is applied is reversed. Therefore, it is not fundamentally necessary to add a bonding step for assembly and fabrication. Moreover, detachment is also possible. This advantageous point will also be described below.  
      According to various exemplary embodiments of the present invention, a motor with a pinion, which is frequently used at an existing factory or the like (or a large number thereof are present at the market of geared motors) can still be used as a motor of a hypoid geared motor and can freely be detached at any time. Therefore, a compact hypoid geared motor, which prevents the waste and ensures a high degree of freedom of design or a high degree of freedom of design change, can be obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Various exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein:  
       FIG. 1  is a front sectional view of a hypoid geared motor according to an exemplary embodiment of the present invention;  
       FIG. 2  is a side view taken along the arrow II-II of a casing (gear box) of a hypoid reduction gear of the hypoid geared motor shown in  FIG. 1 ;  
       FIG. 3  is an enlarged view of the vicinity of a clamp ring of the hypoid geared motor;  
       FIG. 4  is an enlarged view of a principal part of  FIG. 3 ;  
       FIG. 5  is a partially exploded perspective view of the vicinity of an end of a hypoid pinion according to another exemplary embodiment of the present invention; and  
       FIG. 6  is a cross-sectional view showing a conventional example of the configuration of a hypoid geared motor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Various exemplary embodiments of this invention will be hereinafter described in detail with reference to the drawings.  
       FIG. 1  is a front sectional view of a hypoid geared motor according to an exemplary embodiment of the present invention,  FIG. 2  is a sectional view of an end face of a reduction gear viewed from the motor side (corresponding to a view taken along the arrow II-II in  FIG. 1 ), and  FIG. 3  is an enlarged sectional view of the vicinity of a friction clamping portion.  
      A hypoid geared motor HGM 1  is constituted by integrally connecting a motor M 1  and a hypoid reduction gear HG 1  with each other. The motor M 1  includes a helical pinion (motor pinion)  22  which is integrally formed on an end of its motor shaft  20 . Specifically, this exemplary embodiment corresponds to an example where the present invention is applied to the motor M 1  including a pinion that does not engage with a hypoid gear ( 25 ) to form a novel hypoid geared motor HGM 1 .  
      A hypoid reduction gear HG 1  includes a hypoid pinion  24  connected to the helical pinion  22  formed on the motor shaft  20  and the hypoid gear  25  engaging with the hypoid pinion  24 . A hypoid reduction mechanism  26  is constituted by the hypoid pinion  24  and the hypoid gear  25 . At the latter stage of the hypoid gear mechanism  26 , a first parallel axis gear reduction mechanism  28  and a second parallel axis gear reduction mechanism  29  are located so as to obtain the rotation of the hypoid gear  25  from an output shaft  30  after the speed of rotation is further reduced.  
      On the motor M 1  side of a casing (gear box)  32  of the hypoid reduction gear HG 1 , cylindrical parts  32 A and  32 B forming a double-layered structure are formed to extend in the axial direction. Bearings  34  are located inside the inner cylindrical part  32 B so as to rotatably support the hypoid pinion  24 . The reference numerals  36  and  37  denote snap rings for regulating the axial movement of the bearings  34  and the hypoid pinion  24 . A ring-shaped projection  24 T is formed on the hypoid pinion  24  so as to regulate the axial position of the hypoid pinion  24  between the bearings  34 .  
      As shown in  FIGS. 3 and 4  in an enlarged manner, the hypoid pinion  24  includes, on its end face  24 A on the motor M 1  side, a concave  24 H into which the helical pinion  22  formed on the motor shaft  20  is inserted.  
      The hypoid pinion  24  includes a slit  24 S extending from an outer circumferential side of the concave  24 H to its inner circumferential side along the axial direction. By variation of a gap of the slit  24 S, an inner diameter Do of the concave  24 H of the hypoid pinion  24  can also vary. An end  24 S 1  of the slit  24 S is rounded so as to prevent stress concentration.  
      A friction clamp FC is formed on an end of the hypoid pinion  24  on the motor side. The friction clamp FC connects the hypoid pinion  24  and the helical pinion  22  by friction clamping. The friction clamp FC comprises an engaging portion FC 1  and a clamp member FC 2  (a clamp ring  50 ). The engaging portion FC 1  is formed on the end of the hypoid pinion  24  on the motor side, and has the concave  24 H into which helical pinion  22  is inserted. The clamp member FC 2  (a clamp ring  50 ) clamps the engaging portion FC 1  from outside of the concave  24 H in a radial direction with the helical pinion  22  inserted in the concave  24 H.  
      On the outer circumference of the concave  24 H of the hypoid pinion  24 , a ring-shaped step portion  44  is formed in a circumferential direction. The step portion  44  comprises a smooth portion  44 A, a boundary portion  44 B, and a terminal portion  44 C. The bottom of the smooth portion  44 A is processed to have a smaller outer diameter d 2  than an outer diameter d 1  of the hypoid pinion  24 . The boundary portion  44 B forms a slight cut in a continuous manner from the smooth portion  44 A. The terminal portion  44 C is processed to rise from the boundary portion  44 B to have a slightly larger outer diameter d 3  than the outer diameter d 2  of the smooth portion  44 A. Specifically, the relation: d 2 &lt;d 3 &lt;d 1  is established.  
      The clamp ring  50  constituting the clamp member FC 2  of the friction clamp FC is placed so as to cover the step portion  44 . However, a step is formed in a portion  50 E of the clamp ring  50  corresponding to the terminal portion  44 C, and therefore, the clamp ring  50  is not in contact with the terminal portion  44 C. As a result, the clamp ring  50  and the hypoid pinion  24  can be in contact with each other mainly on the smooth portion  44 A. The boundary portion  44 B is not necessarily a cut as a shape. However, since it is difficult to process the boundary portion  44 B so that the outer diameter d 3  is slightly larger than the outer diameter d 2  in practice, it is preferred that the boundary portion  44 B have a notch shape so as to ease such difficulty.  
      As shown in  FIG. 2 , the clamp ring  50  has a slit  50 A whose gap can be reduced in the circumferential direction and has a C-shape as a whole. The clamp ring  50  has a notch  50 C formed in a part of its outer circumference  50 B, into which a bolt (not shown) is screwed. The screwed bolt allows the slit  50 A to be fastened. By fastening the slit  50 A, a state is formed, where the outer circumference  22 A of the helical pinion  22  is clamped from the outside of the concave  24 H of the hypoid pinion  24  in a radial direction. An elongated hole  32 B having an oval cross section is formed through the casing  32  so as to allow the bolt to be screwed therein.  
      An inner diameter D 1  of the clamp ring  50  in its free state (in a state where it is not clamped by screwing the bolt) is smaller than the outer diameter d 1  of the hypoid pinion  24  (D 1 &lt;d 1 ). Furthermore, the inner diameter D 1  is set smaller than the outer diameter d 3  of the terminal portion  44 C of the step portion  44  (D 1 &lt;d 3 ).  
      The functions of the hypoid geared motor HGM 1  according to this exemplary embodiment will now be described.  
      When the hypoid pinion  24  is connected to the helical pinion  22  on the motor shaft  20  of the motor M 1 , the helical pinion  22  is first inserted into the concave  24 H of the hypoid pinion  24 . It is preferred that the clamp ring  50  is engaged with the step portion  44  from the beginning.  
      Since the inner diameter D 1  of the clamp ring  50  in its free state (in a state where it is not clamped by screwing the bolt) is smaller than the outer diameter d 1  of the hypoid pinion  24 , the clamp ring  50  is easily positioned at the step portion  44 . Since the relation, the inner diameter D 1 &lt;the outer diameter d 3 , is established, the clamp ring  50  suitable for the hypoid pinion  24  can be prepared in advance so as to be attached to the hypoid reduction gear HG 1  side. Therefore, the attachment operation of the clamp ring  50  can be omitted at the place of installation (at a factory or the like). In addition, it is possible to always attach the most suitable clamp ring  50 . Moreover, since the relation, D 1 &lt;D 3 , is established, the clamp ring  50  can be prevented from coming off from the step portion  44  in the course of transport or the like even if the clamp ring  50  is attached in advance.  
      Since the inner diameter D 1  of the clamp ring  50  is set smaller than the outer diameter d 3  of the terminal portion  44 C of the step portion  44 , the clamp ring  50  is placed on the step portion  44  while the clamp ring  50  is being slightly expanded.  
      When the gap of the slit  50 A of the clamp ring  50  is reduced by screwing the bolt (not shown) of the clamp ring  50 , the outer circumference  22 A of the helical pinion  22  is clamped from the outside of the concave  24 H of the hypoid pinion  24  in a radial direction so as to frictionally clamp the helical pinion  22  and the hypoid pinion  24 .  
      In the uses of this kind of the hypoid geared motor HGM 1 , the acceleration, the deceleration, and the stop of the rotation of the motor shaft  20  are frequently repeated in many cases. In the connection structure according to this embodiment, the motor shaft  20  and the hypoid pinion  24  are fully integrated in the axial direction as well as in the direction of rotation. Therefore, the function of the helical pinion  22  is completely blocked. As a result, there is no possibility that inconvenience, which generally exists at a joint or the like (for example, the generation of a clattering noise in its reverse rotation, the generation of back-lash, and the like), may occur. Moreover, there is no possibility that fretting may occur in a contact portion. Furthermore, detachment after assembly is easy.  
      In the nature of the present invention, the shape of the motor pinion is not particularly limited. For example, even if the motor pinion is any one of a spur pinion, a helical pinion, and a worm pinion, the present invention is applicable without any problems. Moreover, the present invention can be applicable even to a bevel pinion depending on a change in the shape of an engaging portion or the structure of the friction clamp. As the case where the present invention is applied to a motor including a bevel pinion, the upgrading of an orthogonal transformation mechanism from a bevel gear set to a hypoid gear set is conceived, when the driving at a lower noise or with a smaller vibration is required. Even in such a case, an existing motor with a bevel pinion can still be used.  
      Moreover, the present invention can be effectively applied even if the motor pinion is a hypoid pinion in some cases. For example, in the case where, for some reason, there arises the need of changing a reduction ratio of a dedicated hypoid geared motor including a hypoid pinion formed on a motor shaft which has been used up to then, the application of the present invention allows a hypoid geared motor having a desired reduction ratio to be obtained with the continuous use of the existing motor (with the hypoid pinion).  
      The basically unlimited shape of the pinion formed on the motor shaft side is also an advantage obtained by connecting the motor pinion and the hypoid pinion with each other by “friction clamping” according to the present invention.  
      In the above-described exemplary embodiment, the concave  24 H is formed on the end face of the hypoid pinion  24  on the motor M 1  side so as to insert the tip of the motor shaft  20  therein. In the present invention, however, any structure of the engaging portion or the structure of the friction clamp may be used as long as it satisfies the conditions described above. For example, as shown in  FIG. 5 , an engaging portion of a friction clamp FC′ may have a plurality of axial projections  72  formed on an end of a hypoid pinion  70  on the motor (not shown) side along its outer circumference such that an end of a motor shaft  74  is inserted and placed in the midst of the plurality of projections  72  so as to be surrounded thereby. In this case, the plurality of projections  72  are clamped from the outside in the respective radial directions to frictionally clamp the hypoid pinion  70  and the end of the motor shaft  74 .  
      The present invention can be used in various situations.  
      First, as already described above, for example, if there arises the need of changing a direction of rotation of an output shaft of an existing system using a gear pair mechanism with parallel axes to a direction at a right angle, an existing motor with a pinion can still be used as is even if a spur pinion, a helical pinion, or the like is formed on a motor shaft of the motor.  
      Even if the direction of rotation of the output shaft of the system is desired to be changed to be at a right angle, the motor itself is not particularly required to be replaced. Nevertheless, in conventional cases, a geared motor including a motor with a pinion that had been used up to then was replaced by a completely new hypoid geared motor. This requires new and large investment. In addition, there arises a problem of disposal of the motor with a pinion that has been used. The disposal of the motor with a pinion that can still be used results in the waste of resources. On the other hand, the storage of the motors for the future use imposes a heavy burden on the stock of products.  
      On the other hand, if the rotation of a motor is received by a gear engaging with a pinion formed on a motor shaft so as to then transmit the motive power to a hypoid pinion in order to make use of the existing motor with a pinion, not only the cost is increased but also the space efficiency is degraded because an intermediate stage is present.  
      In this regard, the present invention allows an existing motor with a pinion to be still used. Therefore, a great advantage can be obtained in the first situation where the present invention is applied.  
      As the second situation where the present invention is applied, the “conversion” of the motor with a pinion is conceivable. For example, a manufacturer of geared motors or a large factory has a large amount of stock of new general (parallel axis) motors with a pinion in many cases. If the present invention is applied in such a situation, a hypoid geared motor can be realized merely by supplying a hypoid gear box. As a result, the delivery date can be greatly advanced and the cost can be remarkably reduced in some cases as compared with the case where a fully new hypoid geared motor is supplied.  
      It is apparent that the industrial applicability of the present invention is not limited to the above-described applicable situations. The present invention can be effectively used in various situations where a motor with a pinion (which cannot be used without the application of the present invention) is used as a motor of a hypoid geared motor in a broader way.  
      The disclosure of Japanese Patent Application No. 2003-418588 filed Dec. 16, 2003 and Japanese Patent Application No. 2004-030467 filed Feb. 6, 2004 including specifications, drawings and claims are incorporated herein by reference in their entireties.