Abstract:
An electric pump apparatus includes a bracket, a pump and a motor. The pump includes a pump flange at a front side thereof. The pump flange is attached to the bracket. The motor includes a motor flange at a front side thereof, and the motor flange is attached to the bracket. The bracket ensures a gap between the pump and a machine base to allow for disposition of tubes in the gap. The bracket also ensures a gap between the motor and the machine base to allow for disposition of tubes in the gap. The pump and the tubes overlap and the motor and the tubes overlap, as viewed in plan, such that the electric pump apparatus and the tubes occupy a small floor area.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an electric pump apparatus including, primarily, a pump for generating an oil pressure, and a motor for driving the pump. 
       BACKGROUND OF THE INVENTION 
       [0002]      FIG. 7  hereof illustrates a basic structure of a prior art electric pump apparatus  100  disclosed in JP-A-2006-2569. As shown in  FIG. 7 , the electric pump apparatus  100  includes basic elements, i.e., a vane pump  101  and an electric motor  102  for driving the vane pump  101 . More specifically, a mounting bracket  105  is carried on a machine base  103  through an anti-vibration member  104 , and an electric motor  102  is secured to the bracket  105 . The electric motor  102  has a flange portion  106  mounted to a bell housing  107 , and the vane pump  101  is mounted to the bell housing  107  through a damper ring  108 . 
         [0003]    The vane pump  101  is driven by the electric motor  102  acting as a drive source to pump out liquid. A coupling  112  mechanically interconnecting a motor shaft  109  and the pump shaft  111  is accommodated in the bell housing  107 . Although meshing noise is made from the coupling  112  due to rotation of the motor shaft  109 , a soundproof effect of the bell housing  107  prevents transmission of the noise to the outside of the apparatus  100 , thereby keeping silence of the outside. 
         [0004]    The electric pump apparatus  100  shown in  FIG. 7  has the following problem. Tubes (oil drawing tubes, oil discharging tubes and electric wirings etc.) are disposed around the electric pump apparatus  100 . It is desirable for parts of such tubes to pass under the electric motor  102 . However, the electric motor  102  is placed on the installed bracket  105  and hence no tubes can pass under the electric motor  102 . As a result, the tubes are disposed in such a manner as to bypass the electric motor  102 . This results in an increased floor area occupied by the electric motor and the tubes. 
         [0005]    While there is the demand for effective use of the floor area, it is desirable to reduce the floor area occupied by the electric motor and the tubes. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide a structure designed such that an electric pump apparatus and tubes occupy a small floor area. 
         [0007]    According to an aspect of the present invention, there is provided an electric pump apparatus to be mounted on a machine base having a horizontal mounting surface, the apparatus including a pump for generating an oil pressure, a motor for driving the pump, and a bracket supporting the pump and the motor, wherein the motor is a servo motor with a cooling fan, and the motor comprises: a motor flange connected to the bracket by bolts; a motor shaft disposed horizontally and extending through the motor flange; a rotor mounted on the motor shaft; a stator surrounding the rotor; a motor frame accommodating the rotor and the stator together; a sensor connected to a rear end of the motor shaft; and a fan cover enclosing at least the sensor, the cooling fan being accommodated in the fan cover for air-cooling the motor frame, wherein the bracket comprises: a base portion to be secured to the machine base; and a support plate extending upwardly from the base portion to ensure a gap of a predetermined size between the pump and the mounting surface and a gap of a predetermined size between the motor and the mounting surface, the support plate comprising a pump-side support plate and a motor-side support plate disposed a predetermined distance away from the pump-side support plate. 
         [0008]    The pump and tubes overlap and the motor and tubes overlap, as viewed in plan, and hence the electric pump apparatus and the tubes occupy a small floor area. 
         [0009]    Further, the support plate comprises the pump-side support plate and the motor-side support plate disposed the predetermined distance away from the pump-side support plate. The pump-side support plate and the motor-side support plate extend upwardly from the base portion. Vibration on a side of the pump is transmitted through the base portion to the motor-side support plate, but is lessened by the base portion because the base portion is secured to the machine base. As a result, the damped vibration is transmitted to a side of the motor. 
         [0010]    Preferably, the pump is a flanged axial piston pump, and the pump comprises: a pump flange connected to the bracket by bolts; a pump shaft disposed horizontally and extending through the pump flange; and axial pistons movable in parallel to the pump shaft. The apparatus further comprises a vibration absorbing ring interposed between the support plate and the pump flange for absorbing vibration. 
         [0011]    The pump is the axial piston pump. The axial piston pump unavoidably generates vibration in an axial direction of the pump shaft. To address this, the vibration absorbing ring is interposed between the pump flange and the support plate supporting the pump. The vibration absorbing ring eliminates influence of the vibration of the axial piston pump on the motor. 
         [0012]    Preferably, the apparatus further comprises a flexible coupling interconnecting the pump shaft and the motor shaft. 
         [0013]    The flexible coupling damps the vibration of the pump shaft, and the damped vibration is transmitted to the side of the motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
           [0015]      FIG. 1  is a side elevation view of an electric pump apparatus according to the present invention; 
           [0016]      FIG. 2  is a cross-sectional view of another electric pump apparatus; 
           [0017]      FIG. 3  is an enlarged view of a region  3  of  FIG. 2 ; 
           [0018]      FIG. 4  is a perspective view of a flexible coupling; 
           [0019]      FIG. 5  is an exploded view of the flexible coupling; 
           [0020]      FIG. 6  is a cross-sectional view of the flexible coupling; and 
           [0021]      FIG. 7  is a view illustrating a basic structure of a prior art electric pump apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    As shown in  FIG. 1 , an electric pump apparatus  10  includes a pump  20  for generating an oil pressure, a motor  30  for driving the pump  20 , a coupling  40  mechanically interconnecting a pump shaft  21  and a motor shaft  31 , a bracket  50  supporting the pump  20  and the motor  30 . The electric pump apparatus  10  is mounted on a machine base  60  having a horizontal mounting surface  61 . The machine base  60  may be any kind of base such as a steel base and a concrete foundation or floor. 
         [0023]    The electric pump apparatus  10  is suitable for a hydraulic injection molding machine. That is, the electric pump apparatus  10  supplies oil under high pressure to a clamping cylinder, an injection cylinder and an injector moving cylinder. The single electric pump apparatus supplies oil to the many cylinders. An amount of oil discharged from the pump greatly varies because the many cylinders operate at different timings. The motor  30  is a servo motor to change a speed of the pump to vary the amount of oil discharged from the pump. The servo motor  30  has an inner structure as will be discussed with reference to  FIG. 2 . 
         [0024]    The pump  20  is a hydraulic pump which can be a rotary pump such as a vane pump, a gear pump and a Roots pump. The rotary pump less vibrates in an axial direction of the pump shaft  21 . 
         [0025]    The motor  30  is the servo motor including a motor flange  33  at a front side thereof, and the motor flange  33  is connected to the bracket  50  by bolts  32 . The servo motor also includes the motor shaft  31  disposed horizontally and extending through the motor flange  33 . 
         [0026]    A general-purpose motor operates continuously at a constant speed during a period of time between activation of the motor and stop of the motor. In contrast, the servo motor  30  is also called a control motor which frequently repeats activation, stop and speed change. An accelerated energy required to accelerate a rotor is mostly consumed by a frictional resistance on a bearing. The same goes for deceleration of the rotor. Thus, the servo motor  30  which is used at a high duty (a high frequency and high load) is desired to have a high cooling performance. 
         [0027]    To this end, a fan cover  34  is mounted to the motor with a fan  35  accommodated in the fan cover  34  to perform a forced cooling. 
         [0028]    Although various kinds of structures of fans are well-known, the fan  35  preferably employs a fan motor having a structure providing the small overall length of the fan. 
         [0029]    That is, the fan motor employed by the fan  35  includes a fan motor frame  35   a  having impellers  35   b  mounted thereon, and a fan motor shaft  35   c  mounted to a stay  36 . 
         [0030]    More specifically, the stay  36  is disposed in an upright position on the fan cover  34 . The fan motor shaft  35   c  is secured to the stay  36 . The fan motor frame  35   a  and the impellers  35   b  rotate on the fan motor shaft  35   c.    
         [0031]    A pair of bearings rotatably supporting the fan motor shaft  35   c  is incorporated in the fan motor frame  35   a.    
         [0032]    The bracket  50  is comprised of a base portion  52  secured to the machine base  60  by bolts  51 , and a support plate  53  disposed in an upright position on the base portion  52 . The support plate  53  has a height dimension set to ensure a gap having a height Hp between the mounting surface  61  and the pump  20  and a gap having a height Hm between the mounting surface  61  and the motor  30 . 
         [0033]    For example, an oil drawing tube  63  and an oil discharging tube  64  can pass in the gap Hp. A pneumatic pipe  65  and an electric wiring  68  can pass in the gap Hm. 
         [0034]    Next, a preferred modification is discussed below with reference to the drawings. 
         [0035]    As shown in  FIG. 2 , the servo motor  30  with the cooling fan includes a motor frame  39  accommodating a rotor  37  and a stator  38  together. The rotor  37  is mounted on the motor shaft  31  and the stator  38  surrounds the rotor  37 . The servo motor  30  also includes a sensor  69  connected to a rear end of the motor shaft  31 , and the fan cover  34  enclosing at least this sensor  69 . The servo motor  30  further includes the fan  35  accommodated in the fan cover  34  for air-cooling the motor frame  39 . 
         [0036]    The pump  20  is a flanged axial piston pump. That is, the pump includes a pump flange  23  at a front side thereof and the pump flange  23  is connected to the bracket  50  by bolts  22 . The pump  20  also includes the pump shaft  21  disposed horizontally and extending through the pump flange  23 , axial pistons  24 ,  24  movable in parallel to the pump shaft  21 , a swash plate  25  for actuating the axial pistons  24 ,  24 , and a pump case  26  accommodating these elements together. 
         [0037]    The axial pistons  24 ,  24  are provided in a pump rotor  27  and rotated by the pump shaft  21  such that the axial pistons  24 ,  24  are axially moved by the swash plate  25  to generate an oil pressure. The pump is a reciprocating pump and hence provides a higher oil pressure than that provided by a rotary pump. The axial piston pump is employed depending on an intended purpose. 
         [0038]    The reciprocating pump vibrates in the axial direction of the pump shaft  21  much more than the rotary pump does. When this vibration is transmitted to the motor shaft  31 , the motor frame  39  vibrates to thereby vibrate the fan cover  34  attached to the motor frame  39 , such that the fan motor shaft  35   c  is vibrated through the stay  36 . 
         [0039]    As is clear from the figure, the servo motor  30  is supported by the bracket  50  in a cantilever fashion and hence even a small amplitude of the motor flange  33  causes a large amplitude of the fan motor shaft  35   c  disposed far from the bracket  50 . The pair of bearings supporting the fan motor shaft  35   c  is small in size and thus inferior in durability, and hence, if the bearings are subjected to the large amplitude, the bearings would reach the end of its useful life in a relatively short period of time. 
         [0040]    If large-sized bearings having a prolonged useful life are used, the entire size of the fan  35  would be large, in which case it would be difficult to provide the compact size of the electric pump apparatus  10  and the manufacturing cost of the apparatus would increase. 
         [0041]    To meets the need for the compact size of the electric pump apparatus  10  and reduction in the manufacturing cost of the apparatus, the present invention exercises ingenuities discussed below. 
         [0042]    First, a structure of the bracket  50  is improved such that vibration on a side of the pump  20  is less likely to be transmitted to a side of the motor  30 . 
         [0043]    Second, a vibration absorbing ring  70  is interposed between the bracket  50  and the pump  20 , such that vibration on the side of the pump  20  is far less likely to be transmitted to the side of the motor  30 . 
         [0044]    Third, a structure of the coupling  40  is improved. 
         [0045]    The three improvements above are discussed in order. 
         [0046]    First Improvement: As shown in  FIG. 2 , the support plate  53  is not a single block, but is formed by a pump-side support plate  53 P and a motor-side support plate  53 M disposed a predetermined distance L away from the pump-side support plate  53 P. Vibration on the side of the pump is transmitted to the pump-side support plate  53 P and then to the base portion  52 . Since the base portion  52  is secured to the machine base  60 , the base portion  52  almost never vibrates. That is, the base portion  52  performs a damping function. The damped vibration is subsequently transmitted to the motor-side support plate  53 M. Consequently, the vibration and its amplitude transmitted to the fan  35  are small. 
         [0047]    Second Improvement: As shown in  FIG. 3 , the enlarged view of the region  3  of  FIG. 2 , the vibration absorbing ring  70  made primarily of rubber which absorbs vibration is interposed between the pump-side support plate  53 P and the pump flange  23 . The pump flange  23  is connected to the vibration absorbing ring  70  by the bolt  22 . The pump-side support plate  53 P is connected to the vibration absorbing ring  70  by another bolt  71 . The vibration on the side of the pump vibrates the bolt  22 , but is absorbed by the vibration absorbing ring  70 . Since the vibration is damped by the vibration absorbing ring  70 , the bolt  71  slightly vibrates. 
         [0048]    The provision of the vibration absorbing ring  70  allows provision of bridges  55 ,  56  shown by phantom lines. The provision of the bridges  55 ,  56  increases rigidity of the bracket  50 . In  FIG. 1 , preferably, the vibration absorbing ring  70  is interposed between the bracket  50  and the pump flange  23 . 
         [0049]    Third Improvement: The coupling  40  is a flexible coupling  40  as shown in  FIG. 4 . 
         [0050]    As shown in  FIG. 5 , the flexible coupling  40  is comprised of a first boss  41 , a first flange  42  formed integrally with the first boss  41 , a second boss  43 , a second flange  44  formed integrally with the second boss  43 , (three) spring leaves  45  sandwiched between the first and second flanges  42 ,  44 , first (three) bolts  46  attaching the spring leaves  45  to the first flange  42 , and second (three) bolts  47  attaching the spring leaves  45  to the second flange  44 . 
         [0051]    The first boss  41  is cut in a direction perpendicular to an axis of the boss to form slits  48 , such that a diameter of an axial hole of the first boss  41  is reduced by fastening a first lock bolt  49 . The same goes for the second boss  43 . 
         [0052]    The assembled flexible coupling is shown in cross-section in  FIG. 6 . 
         [0053]    As shown in  FIG. 6 , the leaf spring  45  is attached to the first flange  42  by the first bolts  46  and washers  73 ,  74 . The leaf spring  45  is attached to the second flange  44  by the second bolts  47  and washers  73 ,  74 . The second bolts  47  are finally fastened by a hexagonal wrench inserted into a hole  75  formed through the first flange  42 . 
         [0054]    A motor torque is transmitted from the motor shaft  31  through the first flange  42 , the first bolts  46 , the leaf spring  45 , the second bolts  47  and the second flange  44  to the pump shaft  21  (as indicated by an arrow ( 1 )). In contrast, vibration of the pump shaft  21  is transmitted toward the motor shaft  31  in a reverse route opposite to the route indicated by the arrow ( 1 ). Since the flexible leaf spring  45  has a damping performance, the vibration of the pump shaft  21  is damped and transmitted to the motor shaft  31 . 
         [0055]    Provision of at least one of the foregoing three improvements can address vibration of the fan  35  shown in  FIG. 2 , thereby prolonging the life of the fan  35 . 
         [0056]    Turning to  FIG. 2 , where one lock bolt  49  of two lock bolts of the flexible coupling  40  is located within a range of the distance L and operable from the outside to rotate, no problems arise even if the other lock bolt  76  is hidden by the pump-side support plate  53 P. Thus, the distance L can be freely set. 
         [0057]    Although the electric pump apparatus  10  is suitable for the hydraulic injection molding machine, the apparatus  10  can be arranged in other hydraulic circuits. 
         [0058]    The flexible coupling  40  may be of any type such as a rubber coupling using rubber in place of the leaf spring. 
         [0059]    The electric pump apparatus of the present invention is suitable for the hydraulic injection molding machine. 
         [0060]    Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.