Stepping motor drive apparatus, gear pump, and stepping motor-driven gear pump system

Abstract

A stepping motor-driven system includes a stepping motor, an output device, and a belt and pulley system operably coupling the stepping motor with the output device to impart rotation therebetween. The belt and pulley system includes an input pinion engaged with the stepping motor, an output pinion engaged with the output device, and a timing belt. The timing belt is disposed about the input and output pinions, inhibits elongation, and defines a plurality of spaced-apart grooves on an inwardly-facing surface thereof that are wider than the teeth of the pinions and are configured to receive the teeth of the pinions in meshed engagement therewith. As a result, a gap is defined within each groove. The gaps permit backlash of the timing belt in response to changes in a rotational speed input to the belt and pulley system from the stepping motor, thereby inhibiting loss of control.

What is claimed is: 
     
         1 . A gear pump system, comprising:
 a gear pump configured to receive a rotational input, the gear pump including:
 a drive shaft defining a first end portion and a second end portion, wherein the first end portion of the drive shaft is configured to receive the rotational input to rotate the drive shaft; 
 an enclosure defining a chamber and including a fluid input and a fluid output, wherein the second end portion of the drive shaft extends through the enclosure into the chamber; 
 a drive gear engaged about the second end portion of the drive shaft within the chamber; 
 a passive shaft rotatably mounted within the chamber; and 
 a passive gear engaged about the passive shaft within the chamber and disposed in meshed engagement with the drive gear, wherein rotation of the drive gear rotates the passive gear to urge fluid from the fluid input towards the fluid output, 
 wherein the second end portion of drive shaft is rotatably and sealingly engaged with the enclosure at first and second locations via first and second ball bearing assemblies. 
   
     
     
         2 . The gear pump system according to  claim 1 , wherein the first location is disposed at an end of the drive shaft and the second location is disposed at a position spaced-apart from the end of the drive shaft. 
     
     
         3 . The gear pump system according to  claim 1 , wherein the passive shaft is rotatably and sealingly engaged with the enclosure at third and fourth locations via third and fourth ball bearing assemblies, respectively. 
     
     
         4 . The gear pump system according to  claim 3 , wherein the third and fourth locations are disposed at opposing ends of the passive shaft. 
     
     
         5 . The gear pump system according to  claim 1 , wherein the enclosure includes a tubular body and first and second end covers sealingly engaged with the tubular body. 
     
     
         6 . The gear pump system according to  claim 5 , wherein the first and second locations are disposed at the first and second end covers, respectively. 
     
     
         7 . The gear pump system according to  claim 6 , wherein the first and second ball bearing assemblies are pressed into the respective first and second end covers at the first and second locations, respectively. 
     
     
         8 . The gear pump system according to  claim 5 , wherein the fluid input and the fluid output are defined through the tubular body. 
     
     
         9 . The gear pump system according to  claim 5 , wherein a plurality of bolts sealingly engage the first and second end covers with the tubular body. 
     
     
         10 . The gear pump system according to  claim 1 , wherein each of the first and second ball bearing assemblies includes an inner ring, an outer ring, and a plurality of ball bearings disposed between the inner and outer rings to permit relative rotation between the inner and outer rings. 
     
     
         11 . The gear pump system according to  claim 10 , wherein the inner ring of each of the first and second ball bearing assemblies defines a bore, and wherein each bore is plugged by an inner tube, the inner tubes sealingly engaged with the second end portion of the drive shaft at the first and second locations, respectively. 
     
     
         12 . The gear pump system according to  claim 1 , further comprising:
 a stepping motor including a rotor configured to rotate in response to driving of the stepping motor; and   a belt and pulley system including an input pinion engaged with the rotor, an output pinion engaged with the first end portion of the drive shaft, and a timing belt disposed about the input pinion at a first end portion of the timing belt and disposed about the output pinion at a second end portion of the timing belt such that rotation of the rotor provides the rotational input to the drive shaft.   
     
     
         13 . The gear pump system according to  claim 12 , wherein the stepping motor, the belt and pulley system, and the gear pump are configured such that a moment of inertia defined by the stepping motor is equal to a moment of inertia defined collectively by the belt and pulley system and the gear pump. 
     
     
         14 . The gear pump system according to  claim 12 , wherein the timing belt is configured to permit backlash to dissipate energy from the timing belt to inhibit loss of control. 
     
     
         15 . The gear pump system according to  claim 14 , wherein energy is built up in the timing belt in response to acceleration of the stepping motor, and wherein, the built up energy is dissipated from the timing belt via the backlash of the timing belt. 
     
     
         16 . The gear pump system according to  claim 12 , wherein the stepping motor is configured to switch from an accelerating mode to a constant-speed mode to inhibit loss of control. 
     
     
         17 . The gear pump system according to  claim 16 , wherein backlash of the timing belt occurs upon switching of the stepping motor from the accelerating mode to the constant-speed mode. 
     
     
         18 . The gear pump system according to  claim 16 , wherein the stepping motor is configured to switch from the accelerating mode to the constant-speed mode according to a start/stop profile of the stepping motor. 
     
     
         19 . The gear pump system according to  claim 12 , wherein the belt and pulley system further comprises a set of rollers positioned adjacent the timing belt, the set of rollers configured to inhibit transverse motion of the timing belt in response to the transverse waves such that energy is dissipated from the timing belt via backlash of the timing belt.