Patent Publication Number: US-2005115347-A1

Title: Speed reducer having hypoid gear

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a speed reducer having a hypoid gear.  
      2. Description of the Related Art  
      A hypoid gear set comprising a hypoid pinion and a hypoid gear has the advantages that A) an extending direction of an output shaft is changeable to a direction orthogonal to an input shaft, B) a dimension in the axial direction of the output shaft is shortened, C) a certain speed reduction ratio is obtained only by the hypoid gear set, D) noise and vibration are lowered, and the like.  
      Conventionally, the publication of Japanese Patent No. 2760677 (hereinafter, referred to as “patent document 1”) discloses an example in which the hypoid gear set is applied to a speed reducer for a self-propelled carrier with the use of these advantages.  
      Briefly explaining about this speed reducer with reference to  FIGS. 3 and 4 , a speed reducer  10  used in a self-propelled carrier (an illustration of the whole carrier is omitted) comprises a hypoid reduction gear  12  and a DC motor  14  (only part of the motor is illustrated).  
      A hypoid pinion  16  is formed at an end of a motor shaft  14 A of the DC motor  14  by cutting. The hypoid pinion  16  facing into the hypoid reduction gear  12  is engaged with a hypoid gear  18 .  
      An intermediate pinion  22  is slidably integrated with a hypoid shaft  20 , to which the hypoid gear  18  is attached. The intermediate pinion  22  is engaged with an output gear  24 , which is integrated with an output shaft  23 .  
      In the drawings, the reference numeral  25  refers to a clutch device. When an operator operates a handle  26 , the intermediate pinion  22  is moved along the hypoid shaft  20  through the engagement between a pin  21  and a recessed section  22 A to enable the connection and disconnection of power transmission between the hypoid shaft  20  and the intermediate pinion  22  by the disengagement and engagement of splines  22 B.  
      Thus, when the self-propelled carrier is manually driven especially in the event of a power failure, breakdown in a motor, or the like, it is possible to reduce a traction load.  
      By the way, this self-propelled carrier itself moves in predetermined orbit by the rotation of not-illustrated wheels, in a state that an object to be carried is mounted or suspended thereon. Thus, from the viewpoint of its property, it is necessary to secure “space without any obstruction” on the periphery of the orbit spreading the whole section of the orbit. The “space without any obstruction” has to be larger than a projected area in a traveling direction of the carrier (an outermost outline of a figure illustrated in  FIG. 4 ). Therefore, when the projected area in the traveling direction of the speed reducer  10  is large, the self-propelled carrier itself cannot be installed. Also, it becomes impossible to take advantage of space around the orbit for another object.  
      Accordingly, in the speed reducer  10  for the self-propelled carrier, which is disclosed in the foregoing patent document 1, the hypoid gear set comprising the hypoid pinion  16  and the hypoid gear  18  is installed in part of a speed reduction mechanism. The direction of the motor shaft  14 A of the motor  14  is turned 90 degrees, and the motor  14  extended in the axial direction is installed in a direction along a traveling direction X so as to prevent the projected area in the traveling direction of the carrier from enlarging due to the motor  14 .  
      By using the function of the hypoid gear set, that is, “a dimension in the axial direction of the output shaft can be shortened,” a dimension S in a horizontal direction of the projected area of a reduction gear section is particularly downsized. At the same time, by using the function that “the hypoid gear set can secure a certain speed reduction ratio by itself,” the hypoid gear set is actively used for securing the speed reduction ratio. Furthermore, low noise and low vibration properties make it possible to quietly carry the object to be carried without damage.  
      As described in this application example, since the hypoid gear set has many advantages that a general gear pair mechanism with parallel axes, a bevel gear mechanism, and the like cannot obtain, there are deep-seated needs of the hypoid gear set particularly in the field requiring miniaturization, weight reduction, low noise, low vibration, and the like.  
      According to the technology disclosed in the patent document 1, however, the intermediate pinion  22  moves along the hypoid shaft  20  (a shaft to which the hypoid gear is attached) to structure the clutch device  25 .  
      Thus, the intermediate pinion  22  has to be provided with the recessed section  22 A and the spline  22 B while securing a certain degree of strength, so that a pitch circle diameter cannot help suitably enlarging. Therefore, a speed reduction ratio obtained between the intermediate pinion  22  and the output gear  24  becomes small. As a result, there is a problem that a total speed reduction ratio of the reduction gear  12  cannot help lowering.  
      Accordingly, in the case of an application requiring a higher speed reduction ratio, another stage of gear pair mechanism with parallel axes has to be installed in the reduction gear, or the distance between the center of the hypoid shaft  20  and the center of the output shaft  23  has to be enlarged to enlarge the diameter of the output gear  24 . The reduction gear becomes large and heavy in any method so that there is a problem that the miniaturization and weight reduction of the reduction gear are impaired irrespective of “the introduction of the hypoid gear set.” 
      In the clutch device  25  disclosed in the foregoing patent document 1, the intermediate pinion  22  is manually driven in both of the axial directions. In regard to, for example, the operation of returning the clutch, if spring force or the like is used to return the clutch with light force, convenience is further improved. In this case, however, it is difficult to install such energizing member in the hypoid shaft  22  without increasing a dimension in the axial direction of the output shaft.  
     SUMMARY OF THE INVENTION  
      In view of the foregoing problems, various exemplary embodiments of this invention provide a speed reducer with a hypoid gear, in which a clutch device is installed without impairing the conventional functions of the hypoid gear as possible as it can, and which realizes a certain level of a high speed reduction ratio without increasing the number of speed reduction stages. Furthermore, even when energizing member is installed in the speed reducer to ease the return of a clutch as necessary, a dimension in the direction of an output shaft is not increased.  
      To achieve the foregoing object, according to one of the various exemplary embodiments of the present invention, a speed reducer with a hypoid gear comprises: a hypoid shaft with which the hypoid gear is integrated; an intermediate pinion integrated with the hypoid shaft; an output shaft disposed in parallel with the hypoid shaft; an output gear slidably integrated with the output shaft and being engageable with the intermediate pinion; a clutch shaft disposed in parallel with the hypoid shaft and the output shaft; and a clutch device having a slide member slidably disposed on the clutch shaft, the clutch device being capable of driving the output gear on the output shaft together with a slide of the slide member and of connecting and disconnecting power transmission between the output gear and the output shaft or between the output gear and the intermediate pinion.  
      The present invention focuses attention on the fact that miniaturization is the most required in the axial direction of the output shaft, as described in the foregoing example, in an application to which the speed reducer with the hypoid gear is applied. As the clutch device is installed in the speed reducer with the hypoid gear, the clutch shaft, which is disposed in parallel with the hypoid shaft and the output shaft, is newly provided.  
      Thus, the intermediate pinion (composing part of a gear pair mechanism with parallel axes in the latter stage), which is attached to the hypoid shaft, does not need to have any function related to the clutch device (a recessed section  22 A, a spline  22 B, and the like) so that it becomes possible to reduce a pitch circle diameter of the intermediate pinion. Thus, it becomes possible to secure a high speed reduction ratio of the gear pair mechanism with parallel axes, which is composed of the intermediate pinion and the output gear, without enlarging the pitch circle diameter of the output gear. As a result, it is possible to secure a higher speed reduction ratio while keeping the number of speed reduction stages at two.  
      Since the clutch shaft is newly provided in the present invention, increase in the number of shafts similarly means increase in the number of the speed reduction stages. In adding an intermediate shaft belonging to a power transmission system, however, the intermediate shaft deals with torque much more than torque which the clutch shaft deals with. Thus, bearings corresponding to the high torque have to be disposed when the intermediate shaft is added, and hence a degree of increase in cost is totally different. The effect of not needing to increase another speed reduction stage for securing the speed reduction ratio according to the present invention is extremely beneficial realistically.  
      In the present invention, such energizing member as to easily return the clutch, as described later on, is not always necessary. If such member is provided, however, the energizing member can be attached to the clutch shaft with allowance so that it is possible to certainly prevent a dimension in the axial direction of the output shaft from increasing.  
      Furthermore, in this relation (relating to the fact that the clutch shaft deals with little torque because the clutch shaft does not contribute to power transmission), it is possible to easily dispose the clutch shaft in any position of the speed reducer. Therefore, particularly considering the ease of clutch operation by an operator, the clutch device can be easily disposed in the most appropriate position of the speed reducer.  
      According to the various exemplary embodiments of the present invention, it is possible to easily provide the clutch device in an approximately arbitrary position while preventing increase in length in the axial direction of the output shaft, on which prime importance is placed in the speed reducer with the hypoid gear. At the same time, it becomes possible to secure the high speed reduction ratio of the whole speed reducer. 
    
    
     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 partly broken front view of an exemplary embodiment of a hypoid speed reducer, to which the present invention is applied;  
       FIG. 2  is a sectional view taken along the line II-II in  FIG. 1 ;  
       FIG. 3  is a front sectional view showing an example of the configuration of a conventional hypoid speed reducer; and  
       FIG. 4  is a sectional view taken along the line IV-IV in  FIG. 3 . 
    
    
     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 partly broken front view of a speed reducer having a hypoid gear to which the present invention is applied, and  FIG. 2  is a longitudinal sectional view of  FIG. 1 .  
      Referring to  FIGS. 1 and 2 , a hypoid speed reducer  30  comprises a DC motor  26  and a hypoid reduction gear  28 . The center O 1  of a motor shaft  26 A of the DC motor  26  is disposed in a direction orthogonal (not intersecting) to the center O 2  of an output shaft  45 , and the hypoid reduction gear  28  changes the rotation direction of the DC motor  26  by 90 degrees.  
      A hypoid pinion  34  is formed at an end of the motor shaft  26 A of the DC motor  26  by cutting. The hypoid pinion  34  facing into a casing  36  of the hypoid reduction gear  28  is engaged with a hypoid gear  40 . In other words, the motor shaft  26 A of the DC motor  26  also functions as an input shaft of the hypoid reduction gear  28  in this exemplary embodiment. In a plan view, the center O 1  of the hypoid pinion  34  (that is, the center of the motor shaft  26 A) is orthogonal to the center O 3  of an intermediate shaft (hypoid shaft)  42 , to which the hypoid gear  40  is attached, at a shift amount E 1  away.  
      A second stage pinion (intermediate pinion)  44  is formed in the intermediate shaft  42 . The second stage pinion  44  is engaged with an output gear  46 , which is slidably attached to the output shaft  45 . The output shaft  45  is disposed in parallel with the intermediate shaft  42  (namely, orthogonally to the motor shaft  26 A) through bearings  47  and  49 . A male spline (external gear)  45 A is formed in a part of the outer periphery of the output shaft  45 . On the other hand, a female spline  46 A, which is engageable with the male spline  45 A, is formed in the inner periphery of the output gear  46 . In other words, the output gear  46  is an internal gear engaged with the male spline  45 A, while it is the external gear engaged with the second stage pinion  44 . The output shaft  45  is coupled to an input shaft of a not-illustrated driven member to drive the driven member.  
      Next, a clutch mechanism (clutch device) CL will be described.  
      The output gear  46  has a ring-shaped recessed section  46 B in a part of its outer periphery. An engagement section  48 A of a slide member  48  is engaged in the recessed section  46 B. The slide member  48  is slidable along a slide pin (clutch shaft)  50 , which is separately disposed in parallel with the output shaft  45 . This slide member  48  has a pin  48 B on the opposite side of the engagement section  48 A (an upper side in  FIG. 2 ).  
      A handle (knob)  52  is provided with an eccentric cam  54 , which rotates integrally with the handle  52  about the central axis H 1  of the handle  52 . This eccentric cam  54  has a cam surface  54 A. The cam surface  54 A can rotate about the central axis H 1  in accordance with the rotation of the handle  52 , and the pin  48 B of the slide member  48  is pushed by the rotation of the cam surface  54 A. The slide member  48  is movable only along the slide pin  50 , so that propulsive force (a component of force) of the slide member  48  in the direction of the slide pin  50  is obtained by pushing force from the pin  48 B. The slide member  48  is always biased toward a left direction in  FIG. 2  (the direction of engaging the female spline  46 A of the output gear  46  with the male spline  45 A of the output shaft  45 ) by a spring (energizing member)  60  attached to the slide pin  50 .  
      The clutch mechanism CL, which can connect and disconnect the power transmission between the output gear  46  and the output shaft  45 , comprises the slide pin (clutch shaft)  50  as a center, the handle  52 , the eccentric cam  54 , the spring  60 , the slide member  48 , the female spline  46 A of the output gear  46 , and the male spline  45 A of the output shaft  45 .  
      The casing  36  of the hypoid reduction gear  28 , on the other hand, mainly comprises a main body  36 A and a cover  36 B, which are integrated with bolts  66  through a seal ring  64 . The cover  36 B has support holes  70 ,  72 , and  74 , which support respective shafts in the hypoid reduction gear  28 , that is, the intermediate shaft  42 , the output shaft  45 , and the slide pin  50 . The main body  36 A of the casing  36  has support holes  76 ,  78 , and  80 , which correspond to the support holes  70 ,  72 , and  74 . The intermediate shaft  42  is rotatably supported by the support holes  70  and  76  through bearings  82  and  83 . The output shaft  45  is rotatably supported by the support holes  72  and  78  through the bearings  47  and  49 . The slide pin  50  is rotatably supported by the support holes  74  and  80  directly, because large torque is not applied to the slide pin  50 .  
      The reference numeral  81  refers to an alignment mechanism of the eccentric cam  54 , which comprises a bolt  81 A, a spring  81 B, and a ball  81 C. The alignment mechanism  81  restrains the movement of the eccentric cam  54  in the direction of the central axis H 1 .  
      Then, the operation of the hypoid speed reducer  30  according to this exemplary embodiment will be described.  
      When the motor shaft  26 A of the DC motor  26  rotates, the hypoid pinion  34  formed at the end of the motor shaft  26 A integrally rotates. When the hypoid pinion  34  rotates, the hypoid gear  40  engaged with the hypoid pinion  34  rotates, and the second stage pinion  44  formed in the intermediate shaft  42  rotates. The rotation of the second stage pinion  44  is transmitted to the output gear  46 .  
      During normal use, the position of the handle (knob)  52  fixes the slide member  48  in a position shown by solid lines in  FIG. 2  by use of the function of the spring  60 . Thus, the female spline  46 A of the output gear  46  is engaged with the male spline  45 A of the output shaft  45 , and therefore, the rotation of the output gear  46  becomes the rotation of the output shaft  45  as is.  
      On the other hand, when it becomes necessary to manually drive the driven member for some reason, namely, when torque is inputted from the output shaft  45 , large drive resistance occurs if the output shaft  45  is coupled to the motor shaft  26 A through the second stage pinion  44 , the hypoid gear  40 , and the hypoid pinion  34 . Therefore, in this case, the handle  52  is rotated to rotate the cam surface  54 A of the eccentric cam  54  about the central axis H 1 . Since this rotation gives a component of force in the axial direction of the slide pin  50  via the pin  48 B of the slide member  48 , the slide member  48  slides in a right direction in  FIG. 2  against a biasing force of the spring  60 , and the output gear  46  is moved together in the right direction in  FIG. 2  via the engagement section  48 A. As a result, the engagement between the female spline  46 A of the output gear  46  and the male spline  45 A of the output shaft  45  is released, and the output shaft  45  gets out of a power transmission system from the DC motor  26 . Therefore, an operator can easily drive or move the driven member due to the existence of the clutch mechanism CL.  
      In this exemplary embodiment, the clutch mechanism CL is configured such that the output gear  46  having the female spline  46 A slides along the output shaft  45  with respect to the male spline  45 A formed in the output shaft  45 , to engage and disengage the male spline  45 A and the female spline  46 A. Therefore, the structure of the clutch mechanism CL itself is simple so that it is possible to realize cost reduction of the entire speed reducer.  
      Furthermore, the slide of the output gear  46  along the output shaft  45  is realized by the slide member  48 , which is slidable on the slide pin (clutch shaft)  50  disposed in parallel with the intermediate shaft (hypoid shaft)  42  and the output shaft  45 . Thus, it is possible to effectively use space with more allowance, and it is possible to prevent increase in a dimension S 1  in the axial direction of the output shaft even when the clutch device CL with a return mechanism is provided.  
      Since the clutch device CL is not provided on the side of the intermediate shaft  42 , it is possible to minimize the pitch circle diameter of the second stage pinion (intermediate pinion)  44  to approximately its limit, which is desired to be as small as possible for obtaining a high speed reduction ratio. Therefore, it is possible to easily adapt to the high speed reduction ratio without adding another speed reduction stage or without further enlarging the output gear  46 , the diameter of which is originally large.  
      In the foregoing exemplary embodiment, the power transmission between the output shaft  45  and the output gear  46  is connected and disconnected by moving the output gear  46 . However, by releasing the engagement between the output gear and the intermediate pinion, the power transmission between the output gear and the intermediate pinion may be connected and disconnected.  
      In the foregoing exemplary embodiment, the hypoid pinion is directly formed in the motor shaft, and the motor shaft also functions as the input shaft of the reduction gear. The present invention, however, is applicable to a case where an independent input shaft is provided in a reduction gear and a hypoid pinion is disposed on the input shaft, as a matter of course.  
      Furthermore, energizing member for returning a clutch is not always necessary in the present invention. The operator may manually drive the clutch in both of a connection direction and a disconnection direction.  
      The speed reducer is beneficial in an application requiring the functions of the hypoid reduction gear, as a speed reducer which especially needs the installation of the clutch device, and is expected to prevent increase in dimension in the axial direction of the output shaft and to secure the high speed reduction ratio.  
      The disclosure of Japanese Patent Application No. 2003-400609 filed Nov. 28, 2003 including specification, drawing and claim are incorporated herein by reference in its entirety.