Patent Publication Number: US-9885355-B2

Title: Pump apparatus and marine vessel propelling machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-049717, filed Mar. 12, 2015. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a pump apparatus and a marine vessel propelling machine. 
     Discussion of the Background 
     Japanese Unexamined Patent Application Publication No. 2010-038015 discloses a pump apparatus that adjusts tilt and trim angles of an outboard engine. 
     The pump apparatus is a gear pump apparatus and includes a pump case and a pair of pump gears. The pump case defines a shell. The pair of pump gears are inserted in a pump chamber inside the pump case. The pump gears fit with each other turnably on mutually parallel axes. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a pump apparatus includes a shaft, a first pump, and a second pump. The first pump includes a first driving gear disposed on the shaft in a first phase and rotatable with the shaft to feed a first operating fluid. The second pump includes a second driving gear disposed on the shaft in a second phase shifted from the first phase. The second driving gear is coaxial with the first driving gear and rotatable with the shaft to feed a second operating fluid. 
     According to another aspect of the present invention, a pump apparatus includes a shaft, a first pump, and a second pump. The first pump includes a first pair of gears. The first pair of gears include a first driving gear and a first driven gear. The first driving gear is disposed on the shaft and rotatable with the shaft, and includes first teeth. The first driven gear is engaged with the first driving gear to be driven by the first driving gear so as to feed a first operating fluid. The first driven gear includes second teeth engageable with the first teeth at a first timing when the shaft rotates. The second pump includes a second pair of gears. The second pair of gears include a second driving gear and a second driven gear. The second driving gear is disposed on the shaft and is coaxial with the first driving gear and rotatable with the shaft, and includes third teeth. The second driven gear is engaged with the second driving gear to be driven by the second driving gear so as to feed a second operating fluid. The second driven gear includes fourth teeth engageable with the third teeth at a second timing different from the first timing when the shaft rotates. 
     According to the other aspect of the present invention, a vessel propelling machine includes a marine-vessel-propelling-machine body and a tilt-and-trim apparatus. The marine-vessel-propelling-machine body includes a propeller. The tilt-and-trim apparatus includes a cylinder apparatus and a pump apparatus. The cylinder apparatus includes a cylinder, a piston, and a piston rod. The piston partitions an inside of the cylinder into a first chamber and a second chamber. The piston rod has an end fixed to the piston and extends from the cylinder. The pump apparatus is configured to supply an operating fluid into an inside of the cylinder apparatus so as to extend and retract the cylinder apparatus. The pump apparatus includes a shaft, a first pump, a second pump, and a passage. The first pump includes a first pair of gears. The first pair of gears include a first driving gear and a first driven gear. The first driving gear is disposed on the shaft and rotatable with the shaft. The first driven gear is driven by the first driving gear so as to feed a first operating fluid. The second pump includes a second pair of gears. The second pair of gears include a second driving gear and a second driven gear. The second driving gear is disposed on the shaft and coaxial with the first driving gear and rotatable with the shaft. The second driven gear is engaged with the second driving gear to be driven by the second driving gear so as to feed a second operating fluid. The first operating fluid flows into the passage at a first timing, and the second operating fluid flows into the passage at a second timing shifted from the first timing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a view of a tilt-and-trim apparatus according to an embodiment schematically illustrating a configuration of the tilt-and-trim apparatus; 
         FIG. 2  is an external view of the tilt-and-trim apparatus; 
         FIG. 3  is a partial sectional view of the tilt-and-trim apparatus; 
         FIG. 4  is a circuit diagram illustrating a hydraulic circuit of the pump apparatus; 
         FIG. 5  is a perspective external view of a pump; 
         FIG. 6  is a perspective exploded view of the pump; 
         FIG. 7  is a cross-sectional view of the section taken along the line VII-VII of  FIG. 5 ; 
         FIG. 8  is a cross-sectional view of the section taken along the line VIII-VIII of  FIG. 5 ; 
         FIGS. 9A and 9B  are cross-sectional views of the pump illustrating a flow of oil in the pump; 
         FIG. 10  is a table illustrating a phase of a first pump and a phase of a second pump; and 
         FIG. 11  is a graph illustrating noises generated in the rotation of the first pump and the rotation of the second pump; 
     
    
    
     DESCRIPTION OF THE EMBODIMENT 
     The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. 
       FIG. 1  is a view of an outboard engine  5 , to which a tilt-and-trim apparatus  1  according to the embodiment is applied. 
     The outboard engine  5  is an example of the marine vessel propelling machine. The outboard engine  5  includes an engine body  5   a  and the tilt-and-trim apparatus  1 . The engine body  5   a  generates a propulsive force to a vessel body  2 . The tilt-and-trim apparatus  1  adjusts the inclination angle, θ, of the engine body  5   a  with respect to the vessel body  2 . 
     Schematic Configuration of Engine Body 
     The engine body  5   a  is an example of the marine-vessel-propelling-machine body. The engine body  5   a  includes an engine and a drive shaft (not illustrated). The engine has its crankshaft (not illustrated) oriented in a direction approximately perpendicular (in the longitudinal direction in  FIG. 1 ) to the water surface. The drive shaft is coupled to a lower end of the crankshaft and thus is rotatable with the crankshaft. The drive shaft extends vertically downward. The engine body  5   a  also includes a propeller shaft  11  and a propeller  12 . The propeller shaft  11  is coupled to the drive shaft through a bevel gear mechanism. The propeller  12  mounted on a rear end of the propeller shaft  11 . 
     The engine body  5   a  includes a swivel shaft (not illustrated) and a swivel case  15 . The swivel shaft is oriented in a direction approximately perpendicular (in the longitudinal direction in  FIG. 1 ) to the water surface. The horizontal shaft  14  is oriented in a direction approximately parallel to the water surface, and a swivel case  15  in which the swivel shaft is rotatably accommodated. The swivel case  15  is coupled by a pin (not illustrated) to a pin hole  53   a  (not illustrated) of a piston rod  53  of a cylinder apparatus  50 , described later, of the tilt-and-trim apparatus  1 . 
     Schematic Configuration of Tilt-and-Trim Apparatus  1   
       FIG. 2  is an exterior view of the tilt-and-trim apparatus  1 . 
       FIG. 3  is a partial sectional view of the tilt-and-trim apparatus  1 . 
     As illustrated in  FIGS. 2 and 3 , the tilt-and-trim apparatus  1  includes the cylinder apparatus  50 , a pump apparatus  10 , and a motor  70 . The cylinder apparatus  50  extends and contracts in accordance with oil discharged from and supplied to the cylinder apparatus  50 . The pump apparatus  10  discharges the oil. The motor  70  drives the pump apparatus  10 . 
     The tilt-and-trim apparatus  1  includes a stern bracket  16  (see  FIG. 1 ). The stern bracket  16  couples the swivel case  15  of the engine body  5   a  to the vessel body  2 . The stern bracket  16  is coupled to a pin hole  51   b  of a cylinder  51 , described later, by a pin (not illustrated). 
     Cylinder Apparatus  50   
     As illustrated in  FIG. 3 , the cylinder apparatus  50  includes the cylinder  51  and a piston  52 . The cylinder  51  extends in a shaft center direction CL. The piston  52  is disposed inside the cylinder  51  and partitions the internal space of the cylinder  51  into a first chamber Y 1  and a second chamber Y 2 . The cylinder apparatus  50  also includes a piston rod  53 . The piston rod  53  holds the piston  52  at one end of the piston rod  53  in the shaft center direction CL, and moves in the shaft center direction CL with respect to the shaft center direction CL together with the piston  52 . 
     In the following description referring to the shaft center direction CL of the cylinder  51 , the bottom side of  FIG. 3  will occasionally be referred to as “bottom”, and the upper side of  FIG. 3  will occasionally be referred to as “top”. 
     The cylinder apparatus  50  contracts in accordance with oil supplied to the first chamber Y 1 , and extends in accordance with oil supplied to the second chamber Y 2 . When the cylinder apparatus  50  extends, the oil is discharged from the first chamber Y 1 . When the cylinder apparatus  50  contracts, the oil is discharged from the second chamber Y 2 . 
     The cylinder apparatus  50  includes a projection  51   a  on the bottom of the cylinder  51 . In the projection  51   a , a pin hole  51   b  is formed. The pin hole  51   b  receives a pin (not illustrated) that is to be coupled to the stern bracket  16  (see  FIG. 1 ) of the engine body  5   a . At the top end of the piston rod  53 , a pin hole  53   a  is formed. The pin hole  53   a  receives a pin (not illustrated) that is to be coupled to the swivel case  15  (see  FIG. 1 ) of the engine body  5   a.    
     The cylinder apparatus  50  extends and contracts with the cylinder apparatus  50  coupled to the stern bracket  16  through the pin hole  51   b , which is at the bottom of the cylinder  51 , and with the cylinder apparatus  50  coupled to the swivel case  15  through the pin hole  53   a  of the piston rod  53 , which is at the top end of the piston rod  53 . The extension and contraction of the cylinder apparatus  50  change the distance between the stem bracket  16  and the swivel case  15 . The change in the distance between the stem bracket  16  and the swivel case  15  changes the inclination angle θ of the engine body  5   a  with respect to the vessel body  2 . 
     Pump Apparatus  10   
     The pump apparatus  10  includes a tank  180  and a pump  200 . The tank  180  stores oil. The pump  200  is disposed in the tank  180  to discharge the oil stored in the tank  180 . 
     Tank  180   
     As illustrated in  FIG. 3 , the tank  180  includes a housing  181  and a tank chamber  182 . The tank chamber  182  is a space defined by the housing  181  and the motor  70 . 
     In the example illustrated in  FIG. 3 , the housing  181  has a cylindrical shape that is open at the top of the housing  181  and closed at the bottom of the housing  181 . The housing  181  is integral to the cylinder  51  of the cylinder apparatus  50 . Between the cylinder  51  and the housing  181 , holes (not illustrated) are formed. The holes define a first passage  111  and a second passage  112 . 
     As illustrated in  FIG. 3 , the motor  70  is secured to the top of the housing  181  to keep the top opening of the housing  181  liquid tight. In the motor  70 , its driving shaft  71  is coupled to the pump  200 , which is disposed in the tank chamber  182 . The driving shaft  71  is rotationally driven to rotationally drive the pump  200 . 
       FIG. 4  is a hydraulic circuit of the pump apparatus  10 . 
     Pump  200   
     As illustrated in  FIG. 4 , the pump  200  includes a first pump  201  and a second pump  203 . The first pump  201  includes a first discharge outlet  201   a  and a second discharge outlet  201   b . The first discharge outlet  201   a  and the second discharge outlet  201   b  each discharge the oil stored in the tank  180 . The second pump  203  includes a third discharge outlet  203   a  and a fourth discharge outlet  203   b.    
     In the pump  200 , normal rotation of the motor  70  causes the first discharge outlet  201   a  of the first pump  201  and the third discharge outlet  203   a  of the second pump  203  to discharge the oil. Also in the pump  200 , reverse rotation of the motor  70  causes the second discharge outlet  201   b  of the first pump  201  and the fourth discharge outlet  203   b  of the second pump  203  to discharge the oil. 
     Passage of Pump Apparatus  10  and Valve Arrangement 
     As illustrated in  FIG. 4 , the pump apparatus  10  includes a first passage  111  and a second passage  112 . The first passage  111  couples the first chamber Y 1  of the cylinder apparatus  50  and the first discharge outlet  201   a  of the first pump  201  to each other. The second passage  112  couples the second chamber Y 2  of the cylinder apparatus  50  and the second discharge outlet  201   b  of the first pump  201  to each other. 
     The pump apparatus  10  also includes a third passage  113  and a fourth passage  114 . The third passage  113  couples the first chamber Y 1  of the cylinder apparatus  50  and the third discharge outlet  203   a  of the second pump  203  to each other. The fourth passage  114  couples the second chamber Y 2  of the cylinder apparatus  50  and the fourth discharge outlet  203   b  of the second pump  203  to each other. 
     In the example illustrated in  FIG. 4 , the third passage  113  is coupled to the first chamber Y 1  of the cylinder apparatus  50  through the first passage  111 , and the fourth passage  114  is coupled to the second chamber Y 2  of the cylinder apparatus  50  through the second passage  112 . 
     In the third passage  113 , the pump apparatus  10  includes a first check valve  131 . The first check valve  131  allows the oil to flow from the third discharge outlet  203   a  of the second pump  203  to the first passage  111 , and prevents the oil from flowing from the first passage  111  to the third discharge outlet  203   a.    
     In the fourth passage  114 , the pump apparatus  10  includes a second check valve  132 . The second check valve  132  allows the oil to flow from the fourth discharge outlet  203   b  of the second pump  203  to the second passage  112 , and prevents the oil from flowing from the second passage  112  to the fourth discharge outlet  203   b.    
     The pump apparatus  10  includes a first intake passage  121 . The first intake passage  121  couples the third passage  113  and the tank  180  to each other, and feeds the oil stored in the tank  180  to the third discharge outlet  203   a.    
     The pump apparatus  10  includes a second intake passage  122 . The second intake passage  122  couples the fourth passage  114  and the tank  180  to each other, and feeds the oil stored in the tank  180  to the fourth discharge outlet  203   b.    
     In the first intake passage  121 , the pump apparatus  10  includes a third check valve  133 . The third check valve  133  allows the oil to flow from the tank  180  to the third discharge outlet  203   a , and prevents the oil from flowing from the third discharge outlet  203   a  to the tank  180 . 
     In the second intake passage  122 , the pump apparatus  10  includes a fourth check valve  134 . The fourth check valve  134  allows the oil to flow from the tank  180  to the fourth discharge outlet  203   b  of the second pump  203 , and prevents the oil from flowing from the fourth discharge outlet  203   b  to the tank  180 . 
     The pump apparatus  10  includes a fifth passage  115  and a fifth passage switch valve  141 . The fifth passage  115  branches off from the first passage  111  and is coupled to the tank  180 . The fifth passage switch valve  141  is disposed in the fifth passage  115  and receives pressure from a sixth passage  116  (described below) to open the fifth passage  115 . 
     The pump apparatus  10  includes the sixth passage  116  and a sixth passage switch valve  142 . The sixth passage  116  branches off from the second passage  112  and is coupled to the tank  180 . The sixth passage switch valve  142  receives pressure from the fifth passage  115  to open the sixth passage  116 . 
     The pump apparatus  10  includes a seventh passage  117  and an eighth passage  118 . The seventh passage  117  branches off from the first passage  111  and is coupled to the tank  180 . The eighth passage  118  branches off from the second passage  112  and is coupled to the tank  180 . 
     The pump apparatus  10  includes a seventh passage switch valve  143  in the seventh passage  117 . When the pressure of oil in the seventh passage  117  is higher than a seventh predetermined value of pressure, the seventh passage switch valve  143  is opened to release the oil in the first passage  111  into the tank  180  through the seventh passage  117 . 
     The pump apparatus  10  includes an eighth passage switch valve  144 . The eighth passage switch valve  144  is disposed in the eighth passage  118 . When the pressure of oil in the eighth passage  118  is higher than an eighth predetermined value of pressure, the eighth passage switch valve  144  is opened to release the oil in the second passage  112  into the tank  180  through the eighth passage  118 . 
     The pump apparatus  10  includes a ninth passage  119  and a ninth passage switch valve  145 . The ninth passage  119  branches off from the third passage  113  and is coupled to the tank  180 . The ninth passage switch valve  145  is disposed in the ninth passage  119  and receives the pressure of the second passage  112  to open the ninth passage  119 . 
     The pump apparatus  10  includes a tenth passage  120  and a tenth passage switch valve  146 . The tenth passage  120  branches off from the fourth passage  114  and is coupled to the tank  180 . The tenth passage switch valve  146  is disposed in the tenth passage  120 . When the pressure of oil in the tenth passage  120  is higher than a tenth predetermined value of pressure, the tenth passage switch valve  146  is opened to release the oil in the tenth passage  120  into the tank  180 . 
     The pump apparatus  10  includes a switch valve  150 . The switch valve  150  is coupled to the first passage  111  and the second passage  112 , and switches between discharge and return of oil. 
     The switch valve  150  includes a first switch valve  160  and a second switch valve  170 . The first switch valve  160  is disposed in the first passage  111 . The second switch valve  170  is disposed in the second passage  112 . 
     In the switch valve  150 , a communication passage  151  is formed. The communication passage  151  communicates the first switch valve  160  and the second switch valve  170  with each other. 
     Pump  200   
       FIG. 5  is an exterior view of the pump  200 . 
       FIG. 6  is an exploded perspective view of the pump  200 . 
     As illustrated in  FIG. 5 , the pump  200  includes a pump casing  210 , a first pump  201 , and a second pump  203 . The first pump  201  includes a first driving gear  211  and a first driven gear  213 . The second pump  203  includes a second driving gear  251  and a second driven gear  253 . 
     The pump  200  also includes a driving shaft  207  and a support pin  209 . The driving shaft  207  drives the first driving gear  211  and the second driving gear  251 . The support pin  209  supports the first driven gear  213  and the second driven gear  253 . 
     The pump  200  also includes a first fixing member  281  (illustrated in  FIG. 6 ), a second fixing member  283  (illustrated in  FIG. 6 ), and the first to fourth check valves  131  to  134  (illustrated in  FIG. 6 ). The first fixing member  281  and the second fixing member  283  respectively fix the first driving gear  211  and the second driving gear  251  to the driving shaft  207 . 
     Pump Casing  210   
       FIG. 7  is a cross-sectional view of the section taken along the line VII-VII of  FIG. 5 . 
     Next, a pump casing  210  will be described below by referring to  FIGS. 6 and 7 . 
     As illustrated in  FIG. 6 , the pump casing  210  has what is called a “three-layer structure” in which a first casing  215 , a second casing  217 , and a third casing  219  are stacked atop each other in this order from bottom to top in  FIG. 6 . The pump casing  210  is fixed to the housing  181  (see  FIG. 2 ) by a bolt (not illustrated). 
     In the first casing  215 , a first pump chamber  215   a , a first groove  215   b , and a second groove  215   c  are formed. The first pump chamber  215   a  accommodates the first pump  201 . The first groove  215   b  communicates with the first pump chamber  215   a . The second groove  215   c  communicates with the first pump chamber  215   a  on the opposite side of the first groove  215   b . As illustrated in  FIG. 7 , the first groove  215   b  is included in the first passage  111 , and the second groove  215   c  is included in the second passage  112 . 
     As illustrated in  FIG. 7 , also in the first casing  215 , a first through hole  215   d , a second through hole  215   e , a third through hole  215   f , and a fourth through hole  215   g  are formed. The first through hole  215   d  is included in the first passage  111 . The second through hole  215   e  is included in the second passage  112 . The third through hole  215   f  is included in the ninth passage  119 . The fourth through hole  215   g  is included in the tenth passage  120 . The first to fourth through holes  215   d  to  215   g  penetrate the first casing  215  in its thickness direction. 
     As illustrated in  FIG. 6 , also in the first casing  215 , a first support hole  215   h  and a second support hole  215   i  are formed. The first support hole  215   h  receives the driving shaft  207 . The second support hole  215   i  receives the support pin  209 . The first support hole  215   h  and the second support hole  215   i  penetrate the first casing  215  in its thickness direction. 
     In the second casing  217 , a second pump chamber  217   a , a third groove  217   b , and a fourth groove  217   c  are formed. The second pump chamber  217   a  accommodates the second pump  203 . The third groove  217   b  communicates with the second pump chamber  217   a . The fourth groove  217   c  communicates with the second pump chamber  217   a  on the opposite side of the third groove  217   b . As illustrated in  FIG. 7 , the third groove  217   b  is included in the ninth passage  119 , and the fourth groove  217   c  is included in the tenth passage  120 . 
     As illustrated in  FIG. 7 , also in the second casing  217 , a fifth through hole  217   d , a sixth through hole  217   e , a first check valve chamber  217   f , and a second check valve chamber  217   g  are formed. The fifth through hole  217   d  is included in the ninth passage  119 . The sixth through hole  217   e  is included in the tenth passage  120 . The first check valve chamber  217   f  is included in the third passage  113  and accommodates the first check valve  131 . The second check valve chamber  217   g  is included in the fourth passage  114  and accommodates the second check valve  132 . The fifth through hole  217   d , the sixth through hole  217   e , the first check value chamber  217   f , and the second check valve chamber  217   g  penetrate the second casing  217  in its thickness direction. 
     As illustrated in  FIG. 6 , also in the second casing  217 , a third support hole  217   h  and a fourth support hole  217   i  are formed. The third support hole  217   h  receives the driving shaft  207 . The fourth support hole  217   i  receives the support pin  209 . The third support hole  217   h  and the fourth support hole  217   i  penetrate the second casing  217  in its thickness direction. 
     As illustrated in  FIG. 7 , in the third casing  219 , a third check valve chamber  219   a  and a fourth check valve chamber  219   b  are formed. The third check valve chamber  219   a  is included in the first intake passage  121  and accommodates the third check valve  133 . The fourth check valve chamber  219   b  is included in the second intake passage  122  and accommodates the fourth check valve  134 . The third check valve chamber  219   a  and the fourth check valve chamber  219   b  penetrate the third casing  219  in its thickness direction. 
     As illustrated in  FIG. 6 , also in the third casing  219 , a fifth support hole  219   c  and a sixth support hole  219   d  are formed. The fifth support hole  219   c  receives the driving shaft  207 . The sixth support hole  219   d  receives the support pin  209 . The fifth support hole  219   c  and the sixth support hole  219   d  penetrate the third casing  219  in its thickness direction. 
     First Pump  201  and Second Pump  203   
     Next, the first pump  201  and the second pump  203  will be described below by referring to  FIG. 6 . 
     As described above, the first pump  201  includes the first driving gear  211  and the first driven gear  213 . The second pump  203  includes the second driving gear  251  and the second driven gear  253 . 
     The first driving gear  211 , the first driven gear  213 , the second driving gear  251 , and the second driven gear  253  have identical shapes. That is, a common gear structure can be used in the first driving gear  211 , the first driven gear  213 , the second driving gear  251 , and the second driven gear  253 . The first driving gear  211  and the first driven gear  213  form a first pair of gears, and the second driving gear  251  and the second driven gear  253  form a second pair of gears. 
     Specifically, the first driving gear  211  has the through hole  211   a , and the second driving gear  251  has the through hole  251   a . The through hole  211   a  and the through hole  251   a  receive the driving shaft  207 . A fixing groove  211   b  is formed on one surface of the first driving gear  211 , and a fixing groove  251   b  is formed on one surface of the second driving gear  251 . The fixing groove  211   b  and the fixing groove  251   b  extend radially. In the example illustrated in  FIG. 6 , the fixing grooves  211   b  and  251   b  radially extend respectively across the through holes  211   a  and  251   a.    
     The first driven gear  213  has a through hole  213   a , and the second driven gear  253  has a through hole  253   a . The through hole  213   a  and the through hole  253   a  receive the support pin  209 . A fixing groove  213   b  is formed on one surface of the first driven gear  213 , and a fixing groove  253   b  is formed on one surface of the second driven gear  253 . In the example illustrated in  FIG. 6 , the fixing grooves  211   b  and  253   b  radially extend respectively across the through holes  213   a  and  253   a.    
     The first driving gear  211 , the first driven gear  213 , the second driving gear  251 , and the second driven gear  253  have equal numbers of teeth and have identical tooth shapes. The first driving gear  211 , the first driven gear  213 , the second driving gear  251 , and the second driven gear  253  are each made of a material such as metal or resin highly resistant to abrasion. A non-limiting example is a sintered metal. 
     Driving Shaft  207   
     Next, the driving shaft  207  will be described below by referring to  FIG. 6 . 
     The driving shaft  207 , which is an example of the shaft, is an approximately cylindrical member. In the driving shaft  207 , a flat surface  207   a  and shaft holes  207   b  and  207   c  are formed. The flat surface  207   a  is formed on the outer surface of the driving shaft  207  at its one axial end, and is coupled to the motor  70  (see  FIG. 2 ). The shaft holes  207   b  and  207   c  radially penetrate the driving shaft  207 . 
     The driving shaft  207  through the pump casing  210  has a length that extends over the first casing  215 , the second casing  217 , and the third casing  219  with the flat surface  207   a  protruding from the pump casing  210 . The driving shaft  207  has an outer diameter that allows the driving shaft  207  to be inserted into the through hole  211   a  of the first driving gear  211  and the through hole  251   a  of the second driving gear  251 . 
     The shaft holes  207   b  and  207   c  are formed at different positions in the axial direction of the driving shaft  207 . The shaft holes  207   b  and  207   c  differ from each other in orientation. Specifically, the shaft holes  207   b  and  207   c  have different angles (mounting angles) with respect to the central axis of the driving shaft  207  on a surface orthogonal to the central axis of the driving shaft  207 . In the example illustrated in  FIG. 6 , the shaft holes  207   b  and  207   c  differ from each other by 45 degrees. 
     Support Pin  209   
     Next, the support pin  209  will be described below by referring to  FIG. 6 . 
     The support pin  209  is an approximately cylindrical member. 
     The support pin  209  through the pump casing  210  has a length that extends over the first casing  215 , the second casing  217 , and the third casing  219 . In the example illustrated in  FIG. 6 , the support pin  209  through the pump casing  210  has a length that keeps the support pin  209  within the pump casing  210 . 
     The support pin  209  has an outer diameter that allows the support pin  209  to be inserted into the through hole  213   a  of the first driven gear  213  and the through hole  253   a  of the second driven gear  253 . In the example illustrated in  FIG. 6 , the outer diameter of the support pin  209  is less than the outer diameter of the driving shaft  207 . 
     As illustrated in  FIG. 6 , the support pin  209  is different from the driving shaft  207  in that no shaft holes  207   b  or  207   c  are formed. 
     First Fixing Member  281  and Second Fixing Member  283   
     Next, the first fixing member  281  and the second fixing member  283  will be described below by referring to  FIG. 6 . 
     The first fixing member  281  and the second fixing member  283  are elongate members. In the example illustrated in  FIG. 6 , the first fixing member  281  and the second fixing member  283  have approximately cylindrical shapes. The first fixing member  281  and the second fixing member  283  each are dimensioned to be insertable respectively into the shaft holes  207   b  and  207   c  of the driving shaft  207 . The first fixing member  281  and the second fixing member  283  each are also dimensioned to make the opposite ends of each of the members  281  and  283  protrude beyond the driving shaft  207  when the members  281  and  283  are respectively inserted through the shaft holes  207   b  and  207   c , and make the opposite ends of each of the members  281  and  283  respectively engaged in the fixing grooves  211   b  and  251   b.    
     Arrangement and Movement of Components 
       FIG. 8  is a cross-sectional view of the section taken along the line VIII-VIII of  FIG. 5 . 
     Next, by referring to  FIGS. 6 to 8 , description will be made with regard to how the components of the assembly of the pump  200  are arranged and move. 
     First, description will be made with regard to how the driving shaft  207  is arranged and moves. 
     The driving shaft  207  penetrates the pump casing  210 . The driving shaft  207  is rotatably supported by the first casing  215 , the second casing  217 , and the third casing  219 . The flat surface  207   a  of the driving shaft  207  protrudes from the first casing  215  and is coupled to the motor  70  (see  FIG. 2 ). 
     The driving shaft  207  penetrates the first driving gear  211  and the second driving gear  251 . That is, the first driving gear  211  and the second driving gear  251  are coaxial gears. 
     The first fixing member  281  and the second fixing member  283  are disposed through the shaft holes  207   b  and  207   c  of the driving shaft  207 . The first fixing member  281  and the second fixing member  283 , which are respectively inserted into the shaft holes  207   b  and  207   c , protrude from the outer surface of the driving shaft  207 , and are respectively disposed in the fixing groove  211   b  of the first driving gear  211  and the fixing groove  251   b  of the second driving gear  251 . The first fixing member  281  and the second fixing member  283  prevent a shift in relative positions of the first driving gear  211 , the second driving gear  251 , and the driving shaft  207 . 
     This arrangement ensures that when the driving shaft  207  rotates in response to the driving of the motor  70 , the first driving gear  211  and the second driving gear  251  rotate together with the driving shaft  207 . 
     Next, description will be made with regard to how the support pin  209  is arranged and moves. 
     The support pin  209  penetrates the pump casing  210 . The support pin  209  is fixed by the first casing  215 , the second casing  217 , and the third casing  219 . That is, the support pin  209  is supported by the pump casing  210 , and is restricted in making circumferential and axial movements. Specifically, the support pin  209  is engaged with the first casing  215 , the second casing  217 , and the third casing  219 . More specifically, the support pin  209  is inserted under pressure in the first casing  215 , the second casing  217 , and the third casing  219 . 
     The support pin  209  penetrates the first driven gear  213  and the second driven gear  253 . That is, the first driven gear  213  and the second driven gear  253  are coaxial gears. The first driven gear  213  and the second driven gear  253  are rotatable around the outer circumference of the support pin  209 . The first driven gear  213  and the second driven gear  253  are respectively engaged with the first driving gear  211  and the second driving gear  251 . 
     The arrangement described hereinbefore ensures that in response to the rotation of the motor  70 , the first driving gear  211  and the second driving gear  251  rotate to cause the first driven gear  213  and the second driven gear  253  to rotate around the outer circumference of the support pin  209 . Here, the first driven gear  213  and the second driven gear  253  are different from the driving shaft  207  in that the first driven gear  213  and the second driven gear  253  rotate around the outer circumference of the fixed support pin  209 , instead of rotating together with the support pin  209 . 
     As described above, the fixing grooves  213   b  and  253   b  are respectively formed in the first driven gear  213  and the second driven gear  253 . The fixing grooves  213   b  and  253   b  function as oil storages when oil enters the fixing grooves  213   b  and  253   b.    
     Specifically, in the first driven gear  213 , oil enters the fixing groove  213   b  and then enters the space between the inner surface of the through hole  213   a  of the first driven gear  213  and the outer surface of the support pin  209 . In the second driven gear  253 , the oil in the fixing groove  253   b  enters the space between the inner surface of the through hole  253   a  of the second driven gear  253  and the outer surface of the support pin  209 . This configuration improves slidability in each of the first driven gear  213  and the second driven gear  253  when the gears  213  and  253  rotate around the outer surface of the support pin  209 . 
     As described above, the support pin  209  is engaged with the first casing  215 , the second casing  217 , and the third casing  219 . That is, the support pin  209  determines the position of the support pin  209  in relation to each of the first casing  215 , the second casing  217 , and the third casing  219 . 
     Thus, in the assembling work of the pump  200 , the support pin  209  is usable as a positioning member. A non-limiting example is to engage the support pin  209  with the first casing  215 , and combine the second casing  217 , the third casing  219 , and other components with the support pin  209 . This configuration eliminates or minimizes a shift in the relative positions of the first casing  215 , the second casing  217 , and the third casing  219 . 
     In the example illustrated in  FIG. 6 , the fastening members  311 ,  313 ,  315 , and  317  function to fasten the first casing  215 , the second casing  217 , and the third casing  219 . 
     This embodiment will be further described in comparison with a configuration different from this embodiment. 
     In the different configuration, the support pin  209  rotates together with the first driven gear  213  and the second driven gear  253 . In this case, the support pin  209  is rotatably supported by the first casing  215 , the second casing  217 , and the third casing  219 . 
     This necessitates a reduction in the contact pressure applied to the support pin  209  in order to prevent seizure of the support pin  209 . In order to reduce the contact pressure, it is necessary to employ a configuration that increases the dimensions of the pump  200 . Examples of such configuration include a configuration in which the support pin  209  has an increased axial length at the portion of the support pin  209  supported by the first casing  215 , and a configuration with an additional bearing to receive the support pin  209 . 
     In contrast, in the embodiment, the support pin  209  is fixed to the first casing  215  and other components. Fixing the support pin  209  eliminates the need for increasing the dimensions of the pump  200 , as described above. Also in the embodiment, the fixing grooves  213   b  and  253   b  are respectively formed in the first driven gear  213  and the second driven gear  253 . This ensures lubricity in the support pin  209  without using any bearings. 
     Flow of Oil 
       FIGS. 9A and 9B  are cross-sectional views of the pump  200  illustrating the flow of oil in the pump  200 . Specifically,  FIG. 9A  illustrates the flow of oil in the second pump  203 , and  FIG. 9B  illustrates the flow of oil in the first pump  201 . 
     Next, the flow of the oil in the pump  200  will be described below by referring to  FIGS. 9A and 9B .  FIGS. 9A and 9B  illustrate a case where the driving shaft  207  rotates anticlockwise in  FIGS. 9A and 9B . More specifically, in  FIG. 9A , the second driving gear  251  rotates anticlockwise, and the second driven gear  253  rotates clockwise. In  FIG. 9B , the first driving gear  211  rotates anticlockwise, and the first driven gear  213  rotates clockwise. 
     The second pump  203  will be described by referring to  FIG. 9A . When the second driving gear  251  and the second driven gear  253  rotate in response to the driving of the driving shaft  207 , the oil flows from the second intake passage  122  (see  FIG. 4 ) in a direction (indicated by the outlined arrows in  FIG. 9A ) toward the third passage  113  through the second pump  203 . 
     Specifically, in the second driving gear  251 , the oil flowing from the second intake passage  122  (see  FIG. 4 ) into the second driving gear  251  passes through a confinement region R 1 , an outer region R 2 , and a discharge region R 3 . The confinement region R 1  is defined by the engagement between the second driving gear  251  and the second driven gear  253 , and confines the oil. The outer region R 2  is on the opposite side of the confinement region R 1  across the driving shaft  207 . The discharge region R 3  is where the oil is discharged to a third groove  217   b  (third passage  113 ). The discharge region R 3  is also at a position where the rotation of the second driving gear  251  releases the oil confined between the second driving gear  251  and the inner surface,  217   j , of the second pump chamber  217   a.    
     Similarly, in the second driven gear  253 , the oil flowing from the fourth passage  114  (see  FIG. 4 ) into the second driven gear  253  passes through an outer region R 4  and a discharge region R 5 . The outer region R 4  is on the opposite side of the confinement region R 1  across the support pin  209 . The discharge region R 5  is where the oil is discharged to the third groove  217   b  (third passage  113 ). The discharge region R 5  is also at a position where the rotation of the second driven gear  253  releases the oil confined between the second driven gear  253  and the inner surface,  217   j , of the second pump chamber  217   a.    
     The oil conveyed by the second driving gear  251  and the second driven gear  253  joins the oil in the third groove  217   b  (third passage  113 ) in the discharge regions R 3  and R 5 . 
     Next, the first pump  201  will be described by referring to  FIG. 9B . When the first driving gear  211  and the first driven gear  213  rotate in response to the driving of the driving shaft  207 , the oil flows from the fourth passage  114  (see  FIG. 4 ) in a direction (indicated by the outlined arrows in  FIG. 9B ) toward the first passage  111  through the first pump  201 . 
     At the periphery of the first driving gear  211 , the oil passes through a confinement region R 6 , an outer region R 7 , and a discharge region R 8 . This configuration is similar to the configuration of the second pump  203  and will not be further elaborated. At the periphery of the first driven gear  213 , the oil passes through the confinement region R 6 , an outer region R 9 , and a discharge region R 10 . 
     The discharge region R 8  is at a position where the rotation of the first driving gear  211  releases the oil confined between the first driving gear  211  and the inner surface,  215   j , of the first pump chamber  215   a . The discharge region R 10  is at a position where the rotation of the first driven gear  213  releases the oil confined between the first driven gear  213  and the inner surface,  215   j , of the first pump chamber  215   a.    
     The oil conveyed by the first driving gear  211  and the first driven gear  213  joins the oil in the first groove  215   b  (first passage  111 ) in the discharge regions R 8  and R 10 . The oil conveyed by the first driving gear  211  and the first driven gear  213 , and the oil conveyed by the second driving gear  251  and the second driven gear  253  joins the oil in the first groove  215   b  (first passage  111 ). The first passage  111  and the third passage  113  are examples of the passage. 
     Noises in First Pump  201  and Second Pump  203   
       FIG. 10  is a table illustrating a phase of the first pump  201  and a phase of the second pump  203 . 
       FIG. 11  is a graph illustrating noises generated in the rotation of the first pump  201  and the rotation of the second pump  203 . In the graph illustrated in  FIG. 11 , the horizontal axis represents the degrees by which the gears of the first pump  201  and the second pump  203  rotate, and the vertical axis represents the volume of noise generated. 
     Next, noises are generated in the driving of the first pump  201  and the second pump  203  will be described below by referring to  FIGS. 10 and 11 . 
     When the first pump  201  and the second pump  203  are driven, noises occur due to various causes such as a pulsation involved in the discharge of oil, the confinement of oil by engagement of the gears, and the sliding movement of the gears. In particular, as illustrated in  FIGS. 10 and 11 , where a plurality of pumps (namely, first pump  201  and second pump  203 ) are used with the common motor  70 , the pulsation involved in the discharge of oil may coincide in timing with the confinement of oil. The coincidence in timing may cause the noises to synchronize with each other into a louder noise. 
     In view of noise considerations, in the embodiment, the first pump  201  and the second pump  203  have phases shifted from each other. In the example illustrated in  FIGS. 10 and 11 , the first driving gear  211  and the second driving gear  251  have different angles at which the first driving gear  211  and the second driving gear  251  are fixed to the driving shaft  207 . This configuration eliminates or minimizes the noises generated in the driving of the first pump  201  and the second pump  203 . 
     More specifically, as illustrated in  FIG. 10 , in the confinement regions R 1  and R 6 , the first driving gear  211  and first driven gear  213  are engaged with each other at a timing shifted from the timing at which the second driving gear  251  and the second driven gear  253  are engaged with each other. For example, the timing at which the first driving gear  211  and the first driven gear  213  are not engaged with each other in the first pump  201  will be referred to as “open” state timing. At the “open” state timing, the second driving gear  251  and the second driven gear  253  are engaged with each other in the second pump  203 , which will be referred to as “closed” state timing. 
     When the confinement region R 6  of the first pump  201  is at the “closed” state timing, the confinement region R 1  of the second pump  203  is at the “open” state timing. 
     In the discharge regions R 5  and R 10 , the confinement state implemented between the first driven gear  213  and the inner surface  215   j  is released at a timing shifted from the timing at which the confinement state implemented between the second driven gear  253  and the inner surface  217   j  is released. That is, the oil fed from the first pump  201  joins the oil in the first groove  215   b  (first passage  111 ) at a timing shifted from the timing at which the oil fed from the second pump  203  joins the oil in the third groove  217   b  (third passage  113 ). 
     For example, as illustrated in  FIG. 10 , when a confinement state is implemented between the first driven gear  213  and the inner surface  215   j  in the first pump  201 , that is, at the “closed” state timing, no confinement state is implemented between the second driven gear  253  and the inner surface  217   j  in the second pump  203 , that is, the second pump  203  is at the “open” state timing. 
     When the confinement region R 10  of the first pump  201  is at the “open” state timing, the discharge region R 5  of the second pump  203  is at the “closed” state timing, which is not illustrated in  FIG. 10 . 
     By referring to  FIG. 11 , description will be made with regard to noise generated in shifting the phases of the first pump  201  and the second pump  203 . In the example illustrated in  FIG. 11 , the degrees by which the gears of the first pump  201  and the second pump  203  rotate are shifted from each other in phase by half the cycles of the noises generated. 
     In the configuration illustrated in  FIG. 11 , where the phases of the first pump  201  and the second pump  203  are shifted from each other, the noises generated in the first pump  201  and the second pump  203  will be compared with a composite noise (indicated by “Noise” in  FIG. 11 ) obtained by combining together the noises generated in the first pump  201  and the second pump  203 . The comparison indicates that the composite noise is smaller in maximum noise volume. That is, the comparison indicates that shifting the phases of the first pump  201  and the second pump  203  from each other causes the generated noises to cancel each other, resulting in a reduced composite noise. 
     Modifications 
     In the embodiment described above, the first fixing member  281  and the second fixing member  283  are used to shift the position at which the first driving gear  211  is fixed to the driving shaft  207  from the position at which the second driving gear  251  is fixed to the driving shaft  207 . This configuration, however, should not be construed in a limiting sense. Any other configuration is possible insofar as the angles of the first driving gear  211  and the second driving gear  251  with respect to the driving shaft  207  are unambiguously determined upon mounting of the first driving gear  211  and the second driving gear  251  to the driving shaft  207 . A non-limiting example is to form flat surfaces of mutually different angles with respect to the driving shaft  207  at a plurality of positions on the outer surface of the driving shaft  207 . 
     In the embodiment described above, the first casing  215 , the second casing  217 , and the third casing  219  make up a three-layer structure, and the support pin  209  is used as a positioning member in the three-layer structure. This configuration, however, should not be construed in a limiting sense. It is also possible to use the support pin  209  as a positioning member in a two-layer structure, a four-layer structure, or a more-than-four-layer structure. 
     It is also possible to use the support pin  209  as the only positioning member or as one of a plurality of positioning members. 
     In the embodiment described above, the confinement regions R 1  and R 6  have open and closed timings shifted from each other, and the discharge regions R 5  and R 10  have their open and closed timings shifted from each other. Another possible embodiment is to implement a shift in the open and closed timings only in the confinement regions R 1  and R 6  or in the discharge regions R 5  and R 10 . Another possible embodiment is to synchronize the open and closed timings of the confinement regions R 1  and R 6  with the open and closed timings of the discharge regions R 5  and R 10 , or shift the open and closed timings of the confinement regions R 1  and R 6  from the open and closed timings of the discharge regions R 5  and R 10 . 
     A pump apparatus may include a plurality of pumps in the pump apparatus. This configuration may cause the entirety of the pump apparatus to generate large noise since noises generated by the pumps synchronize with one another. 
     In a non-limiting embodiment, the first driving gear may be disposed on the shaft at a first angle, and the second driving gear may be disposed on the shaft at a second angle different from the first angle. 
     In a non-limiting embodiment, the first driving gear and the second driving gear may have equal numbers of teeth. 
     In a non-limiting embodiment, the first teeth, the second teeth, the third teeth, and the fourth teeth may have equal numbers of teeth. 
     The embodiments eliminate or minimize noise generated in the driving of a pump apparatus including a plurality of pumps can be reduced. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.