TWO SPEED GEROTOR MOTOR WITH CENTRALLY LOCATED VALVE AND COMMUTATOR

The invention relates to gerotor-type motors.

Gerotor type pumps and motors are well known to those in the pump and motor art. They include a power element which has a lobed set of gears which, when rotating, form increasing and decreasing volume cavities therebetween. Gerotor type pumps and motors are shown in US Patent specification Nos. 4,501,536; 4,545,748; and 4,563,136.

Among the various gerotor-type motors are motors capable of operating at two speeds and torques at a given flow and pressure in the driving fluid. This allows both high speed, low torque and low speed, high torque motor operation. Generally these motors are constructed to operate at two speeds in one of two ways. In the first two speed construction the motor has a single power element with a commutator and valve capable of converting selected motor chambers to pumping chambers and vice versa. Examples of this type of two speed construction are shown in US Patent specifications Nos. 3,778,198; 4,480,971; and 4,715,798.

These motors suffer from cavitation problems in the high speed mode. In order for these motors to operate efficiently in the low speed mode, the power element must be designed in such a manner that the conversion of motor chambers to pumping chambers in the high speed mode causes the element to rotate fast enough that cavitation occurs in the fluid. This cavitation causes damage to the motor. In addition, this construction requires an external pilot valve and a pressurized fluid source for shifting between speeds.

The other two speed construction for gerotor-type motors requires two power elements and an external valve for shifting. In the low speed mode the power elements are connected in parallel while in the high speed mode the power elements are connected in series. While this construction does not suffer from the problem of cavitation, it does have a problem with pressure drop. In this construction, the valves which allow the power elements to be switched between parallel and series operation are located outside the motor and are connected to the motor by hoses. This arrangement results in a long travel path and narrow passages for the fluid which powers the power elements.

Patent specification US-A-4 875 841, on which the preamble of claim 1 is based, discloses a single speed gerotor device with two gerotor structures mounted back to back with a porting member between them.

Patent specification GB-A-2 140 872 discloses a gear pump or motor provided as two pairs of gears separated by an intermediate plate which contains a three position valve whereby the gears are connected in series, in parallel or as a short circuit.

Patent specification US-A-2 599 701 discloses a unit with two gerotor pump units axially separated by an intermediate porting plate which includes a spool flow control valve.

According to the invention there is provided a gerotor-type motor comprising:

• a first gerotor-type power element disposed along an axis;
• a second gerotor-type power element disposed along said axis and axially spaced therefrom;
• a first commutator plate disposed adjacent the first power element and disposed axially between the first and second power elements, the first commutator plate having commutator ports extending axially therein to direct fluid to and from the fist power element;
• a second commutator plate disposed adjacent the second power element and disposed axially between the first and second power elements, the second commutator plate having commutator ports extending axially therein to direct fluid to and from the second power element;
• a valve piece disposed adjacent and axially between the first and second commutator plates and structurally joining the first power element and respective commutator plate to the second power element and respective commutator plate;

• valve means is disposed in the valve piece and is effective to direct fluid flow to the first and second power elements selectively either in series for relatively high speed operation or in parallel for relatively low speed operation such that the motor can operate selectively at either speed with a single fluid flow rate and pressure;
• the valve means comprises:
• a spool valve including a spool valve cylinder disposed in the valve piece and having longitudinal segments therein, and a spool valve piston movable in the spool valve cylinder for sealing and selectively separating the longitudinal segments of the spool valve cylinder; and
• the motor further comprises
• first radially inner and first radially outer concentric fluid passage galleries disposed adjacent the spool valve and adjacent the first commutator plate, each of the galleries being connected to the spool valve by spool valve openings and connected to the commutator ports of the first commutator plate, and second inner and second outer concentric galleries disposed adjacent the spool valve and adjacent the second commutator plate, each of the galleries being connected to the spool valve by spool valve openings and connected to the commutator ports of the second commutator plate.

Such a two speed gerotor-type motor can have improved ability to operate efficiently at two speeds without cavitation or excess noise and with less pressure drop in the power fluid than in prior art constructions.

The system can use a motor drive fluid for all shifting in order to allow the use of solenoid, manual or automatic control.

The invention can provide a differential two speed motor option with two independent output shafts capable of independent operation while in parallel mode and locked by fluid pressure when in series mode.

The spool valve is connected to a fluid inlet and a fluid outlet of the motor as well as the galleries so that the movement of the spool valve piston in the spool valve cylinder directs the flow of fluid between the inlet and outlet and the galleries.

The location of the valve within the motor and directly between the power elements can result in a more compact motor and a much shorter flow path. It eliminates the external plumbing of the kind used in the prior art two element systems thereby reducing pressure drop and giving a motor which is sturdy, easy to construct, and reliable. The concentric galleries provide large connection openings between the spool valve and the commutator ports and this also reduces pressure drop.

The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:

• Figures 1 is a cross-sectional view of a motor according to the invention taken axially through the motor;
• Figure 2 is a cross-sectional view of the motor shown in Figure 1 taken along line 2-2 in Figure 1;
• Figure 3 is a cross-sectional view of the motor shown in Figure 1 taken along line 3-3 in Figure 1;
• Figure 4 is a cross-sectional view of the motor shown in Figure 1 taken along line 4-4 in figure 1;
• Figure 5 is a cross-sectional view of the motor shown in Figure 1 taken along line 5-5 in Figure 1;
• Figure 6 is a cross-sectional view of the motor shown in Figure 1 taken along line 6-6 in Figure 1;
• Figure 7 is a cross-sectional view of the motor shown in Figure 1 taken along line 7-7 in Figure 1;
• Figure 8 is a cross-sectional view of the motor shown in Figure 1 taken along line 8-8 in Figure 1; and
• Figure 9 is a cross-sectional view of the motor shown in Figure 1 taken along line 9-9 in Figure 1.

Referring to Figures 1 to 9, a motor 11 includes end pieces 13 and 15, power element section 17 and 19, commutator plates 21 and 23, and a valve piece 25. These portions of the motor are generally cylindrical and extend along an axis 27 so that the motor has a generally cylindrical shape. The motor parts 13 to 25 are held together by bolts 29 which are regularly spaced about the radially outer portion of the motor 11. The bolts extend through each of the parts 15 to 25 and are threaded into the end piece 13.

Extending through the motor 11 along the axis 27 is a shaft 31. The shaft 31 is connected by splines to rotate with radially inner pieces of the power element sections 17 and 19. Because the shaft 31 is a single piece, the power element sections 17 and 19 must, therefore, operate so as to rotate together. A splines end 33 of the shaft 31 is connected for rotation with an external shaft 35, also disposed along the axis 27 and extending out of the end piece 13. As the power element sections 17 and 19 are hydraulically driven, they rotate the shaft 31 which in turn rotates the external shaft 35. The shaft 35 can be connected to a device outside the motor to which rotational work is desired to be applied by the motor 11.

The power element sections 17 and 19 are mirror images of each other so that a description of the parts of one describes the corresponding parts of the other. However, it is best to position the rotational relation between the power element sections 17 and 19 so that they are out of phase with respect to each other. In other words, the power element timing is such that the power curve of one overlaps the power curve of the other in order to create a damping effect. This can be achieved by rotationally advancing the inner gerotor of one power element section one half lobe ahead of the other. This out of phase rotational relation achieves a smoother, quieter motor operation. The out of phase rotational relation is maintained because the shaft 31 is a single piece.

Although not shown, it is possible to form the shaft 31 of two pieces each having an output end, which is able to rotate separately in parallel (low speed, high torque) mode but each of which is locked by fluid pressure in the series (high speed, low torque) mode. This allows independent rotation in the parallel mode while maintaining the described advantages in the series mode. No gearing or special valving is required since, in series flow, the fluid flow itself will lock the rotation in tandem. A transverse cut through the shaft is all that is required for the separation.

The power element section 17 includes a valve plate 37, an inner gerotor 39, an outer gerotor 41 and a power element housing 43. The valve plate 37 and the inner gerotor 39 each have a splined inner radius which connects with the splined exterior of the shaft 31 so that they rotate together. Rolls 45 are provided on the radially outer portion of the inner gerotor 39 to mate with inwardly extending gerotor teeth 47 of the outer gerotor 41. Rollers 49 are provided on the radially inner portion of the power element housing 43 to mate with openings 51 provided on the radially outer portion of the outer gerotor 41 so that the outer gerotor 41 orbits as it moves between the rotating inner gerotor 39 and the stationary power element housing 43.

Located adjacent the valve plate of each power element section is the respective commutator plate 21,23. The plate 21 is adjacent the power element section 17 and the plate 23 is adjacent the power element section 19. The commutator plate 21 is a mirror image of the commutator plate 23 so that a description of the parts of one is a description of the corresponding parts of the other.

The commutator plate 21 has a set of regularly spaced ports 53 extending about the commutator plate 21 in a circle. Each port 53 extends axially through the plate to allow fluid to pass to and from the power element section 17 therethrough. Every other port extends therethrough, however, alternately radially inwardly and radially outwardly so that every other port connects with a radially inner concentric gallery 55 in the valve piece 25 and every other port connects with a radially outer concentric gallery 57 in the valve piece 25. For example a port 53A extends axially through the commutator plate 21 to connect to the radially outer concentric gallery 57 while a port 53B extends axially through the commutator plate 21 to connect to the radially inner concentric gallery 55.

A commutator plate of this construction is described in our copending European patent application no. 90912213.7 (0 485 473) and the details of its manufacture and the method in which fluid is conveyed to the power element therethrough are described therein. The manner in which orbiting outer gerotor motors function and the manner in which rotating valve plates selectively deliver the correct pressure fluid to the gerotor sets of such motors are well known in the art of gerotor-type pumps.

The present invention provides an improved means for selectively delivering fluid to the power elements 17 and 19 either in series or in parallel. By in series it is meant that the fluid flow path requires the powering fluid to pass first through one power element and then the other. By in parallel it is meant that the fluid flow path requires the powering fluid to be split into two flows one of which passes through the first power element and the other of which passes through the second power element. The improved means for this selective delivery of fluid to the power elements is disposed in a reliable, compact package; i.e., the valve piece 25.

Referring now particularly to Figures 1 to 5, the valve piece 25 has formed therein an inlet 59 and an outlet 61 for the powering fluid to enter and exit the motor 11. The inlet 59 and the outlet 61 extend into the valve piece through a raised portion 63 of the valve piece 25. The raised portion 63 of the valve piece extends outwardly from the generally cylindrical shape of the motor 11. Also extending into the raised portion 63 is a spool valve 65.

The concentric galleries 55 and 57 are provided in the valve piece 25 adjacent the commutator plate 21. In a mirror image fashion, a radially inner concentric gallery 67 and a radially outer concentric gallery 69 are provided in the valve piece adjacent the commutator plate 23. The galleries 67 and 69 function to direct fluid flow to and from the power element 19 through the commutator 23 in the same manner that the galleries 55 and 57 direct fluid flow to and from the power element 17 through the commutator 21, as described above.

The spool valve 65 extends into the valve piece 25 between and adjacent the concentric galleries 55 and 57 on one side and the concentric galleries 67 and 69 on the other side. By means of connections thereto, the spool valve 65 selectively connects the inlet 59, the outlet 61, and the galleries 55, 57, 67 and 69. In this way the spool valve directs the fluid flow to be either in series or in parallel.

The spool valve includes a spool valve cylinder 71 and a spool valve piston 73. The spool valve cylinder 71 extends longitudinally into the valve piece 25 beneath the inlet 59 and the outlet 61 and between the galleries 55, 57, 67 and 69. An opening 75 connects the inlet 59 to the cylinder 71. An opening 77 connects the outlet 61 to the cylinder 71. An opening 79 connects the gallery 57 to the cylinder 71. An opening 81 connects the gallery 55 to the cylinder 71. An opening 83 connects the gallery 69 to the cylinder 71. An opening 85 connects the gallery 67 to the cylinder 71.

As best seen in Figures 4 and 5, the cylinder 71 has lands 87, 89, 91, 93 and 95 which define longitudinal segments of the cylinder 71. Four piston heads 97, 99, 101, and 103 sealingly mate with the lands in order to direct flow through the cylinder 71 in such a manner that the power elements receive flow either in parallel or in series, depending on the position of the spool valve piston 73.

As shown in Figures 3, 4 and 5, the spool valve piston 73 is positioned for parallel flow to the power elements 17 and 19. The piston head 99 is aligned with the land 87, the piston head 101 is aligned with the land 91 and the piston head 103 is aligned with the land 95. In this manner, the cylinder 71 is divided into a first segment between the land 87 and the land 91 and a second segment between the land 91 and the land 95. Flow enter the inlet 59, flow into the second segment and into the openings in that segment; i.e., the openings 79 and 85. This divides the inlet flow into one path passing into the gallery 57 and one path passing into the gallery 67. From these galleries the flow passes through the commutator plates and into the pressure sides of the power elements in parallel. Fluid from the discharge sides of the power elements 17 and 19 pass through the commutator plate and into the galleries 55 and 69. From these galleries the fluid passes through the openings 83 and 81 into the first segment of the cylinder 71. The rejoined discharge flow then exits the motor through the outlet 61.

As is apparent from Figure 4, the piston 73 can be moved toward the blind end of the cylinder 71 to change the segmentation of the cylinder. This movement can be achieved by a manual or electrical or hydraulic devices connected to the piston (not shown). In this series position of the piston 73, the head 97 is aligned with the land 87, the head 99 is aligned with the land 89, the head 101 is aligned with the land 93 and the head 103 is aligned with the land 95. This divides the cylinder into a first segment between the land 87 and the land 89, a second segment between the land 89 and the land 93 and a third segment between the land 93 and the land 95. Fluid entering the inlet 59 enters the cylinder 71 and passes into the opening 79, the only opening in the third segment between the land 93 and the land 95. Fluid enters the gallery 57 and passes to the power element 17 through the commutator 21. Discharge fluid from the power element 17 passes into the gallery 55 through the commutator 21. This fluid enters the second cylinder segment between the land 89 and the land 93. Since the openings 81 and 85 are in this segment, fluid passes from the gallery 55 to the gallery 67 through the cylinder 71. Fluid then passes into the power element 19 through the commutator 23. Discharge fluid from the power element 19 passes through the commutator 23 into the gallery 69. From the gallery 69 the fluid passes into the first segment of the cylinder 71 between the land 87 and the land 89. The fluid then passes out of the motor 11 through the outlet 61. In this manner the fluid passes through the power elements 17 and 19 in series.

It can be seen that the operation of the spool valve 65 in its two positions allows the flow of power fluid in the motor to be easily directed in either series or parallel flow. Large openings and short flow paths are provided. These can be provided in the small valve piece 25 which is a structural part of the motor.