GB2112862A

GB2112862A - Rotary hydraulic motor

Info

Publication number: GB2112862A
Application number: GB08300048A
Authority: GB
Inventors: Eric Thomas Percival
Original assignee: ADAN Ltd
Current assignee: ADAN Ltd
Priority date: 1982-01-08
Filing date: 1983-01-04
Publication date: 1983-07-27
Also published as: GB2112862B; GB8300048D0

Abstract

A gerotor-type motor comprises a toothed stator (2), a toothed rotor (4), a commutator valve (8, 9) operated by the rotor, and auxiliary ports (22) that communicate with the inter-tooth chambers (6a-g) when the latter are at maximum or substantially maximum volume to relieve the pressure of working fluid trapped therein. The auxiliary ports may be in the housing, as shown, or in the rotor at 22'. Alternatively, said ports may be in a pivoted plate next to the rotor to facilitate reversal. Fig. 4 (not shown). <IMAGE>

Description

SPECIFICATION Hydraulic motor This invention relates to an hydraulic motor and more particularly concerns an hydraulic motor of the "orbiting gerotor" kind which comprises a toothed stator, a toothed rotor having one less tooth than the stator, a commutator valve operable by the rotor and being for sequentially connecting fluid chambers defined between the rotor and stator teeth with a hydraulic fluid source and drain via main ports in the motor body. Such a motor will be referred to hereinafter as an hydraulic motor of the kind described.

These hydraulic motors are high torque slow speed motors which are relatively small and yet capable of providing considerable power over a wide speed range and are instantly reversible by simply reversing the direction of the hydraulic fluid flow.

As each chamber in turn goes through a transition stage between pressure and drain, any timing error between the rotor and the commutator valve results in fluid being trapped in the chamber, the chamber traverses a state of maximum volume and hence undergoes a volume reduction after passing through maximum volume before it communicates with drain via a main port.

During this volume reduction the hydraulic fluid trapped in the chamber acts to reduce the torque of the motor and it may also subject the motor to undue wear and/or distortion.

It is an object of the present invention to remove or ameliorate this drawback.

According to the invention, an hydraulic motor of the kind described is provided with auxiliary ports to relieve pressure in the chambers only when the latter are at maximum or substantially maximum volume.

The auxiliary ports have the effect of increasing the torque and hence the efficiency of the motor possibly accompanied by a reduction in the operating noise level of the motor.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a sectional view of one embodiment of an hydraulic motor according to the invention, Figure 2 is a section taken along Il-Il of Figure 1, Figure 3 shows schematically the manner in which the commutator valve connects the chambers between the rotor and stator teeth with a source of fluid pressure and drain, and Figure 4 is a sectional view of part of another embodiment of an hydraulic motor according to the invention.

Referring to Figures 1-3, the hydraulic motor shown therein, comprises a motor body 1, a stator 2 having seven teeth 3, and a rotor 4 within the stator and having six teeth 5, i.e. one less tooth than the stator. Chambers 6a - g are defined between the teeth 3 and the teeth 5. The chambers 6a -g are in constant communication with a respective one of seven main ports 7 provided in the motor body 1.

The motor also has a commutator valve comprising a rotating distributor valve member 8 and a stationary outer valve member 9 provided in the motor body 1. The distributor valve member 8 is rotated with the rotor by means of a drive shaft 10 provided at opposite ends with involute splines 11 and 12 which engage respective internal splines 13 and 14 on the rotor and on the distributor valve member. The outer valve member 9 comprises seven longitudinally extending circumferentially spaced passages 1 5 which communicates at one end with the ports 7 respectively and which have elongate radially inwardly facing openings 1 6 adjacent their opposite ends. The distributor valve member has two sets each comprising six longitudinally extending passages 1 7 and 1 8 respectively.The passages 1 7 are interdigitated with the passages 1 8 so that they alternate with one another around the circumference of the distributor valve member 8. The passages 1 7 each communicate with an annular groove 19 in the valve member 8 and the passage 18 each communicate with an annular groove 20 in the valve member 8. In operation hydraulic fluid under pressure is fed to one of the grooves 1 9 and 20, in the example shown groove 1 9 and the other groove is connected to a fluid reservoir.As the distributor valve member 8 rotates, each passage 1 5 communicates through its opening 1 6 with a passage 1 7 to supply hydraulic fluid to a respective chamber 6, then its opening 16 is closed off by a land 21 between the passage 17 and an adjacent passage 18 in the valve member 8 and then opening 16 communicates with a passage 1 8 to connect the respective chamber 6 to drain, i.e. to the fluid reservoir. As shown in Figure 2, chambers 6a, 6b and 6c are connected to hydraulic fluid under pressure and chambers 6e, 6f and 6g are connected to drain.Chamber 6d is shown in a transitional stage and at maximum volume and communicates with neither a passage 1 7 nor a passage 18 in the valve member 8 because its associated opening 1 6 is closed off by a land 21.

Moreover, it will be appreciated that further clockwise movement of the rotor 4 will have to take place before the chamber 6d is connected to drain through its associated passage 1 5 and during this clockwise movement the volume of the chamber 6dwill reduce. In order to relieve the pressure in the chamber 6d and indeed in the other chambers when in a transitional stage, the motor body is provided with seven auxiliary ports 22 located on or close to a radial plane 23 which bisects the angle between adjacent stator teeth 3.

The auxiliary ports 22 are located so that they communicate with respective chambers 6 only when each chamber 6 is at maximum volume or at substantially maximum volume. The auxiliary ports communicate with the interior of the distributor valve member 8 and in order that fluid discharged through the auxiliary ports may be returned to the fluid reservoir, the interior of the valve member 8 is connected via a check valve 24 to the annular groove 20 i.e. the groove connected to the fluid reservoir. The motor can be reversed simply by reversing the direction of hydraulic fluid (flow i.e.

by connecting groove 20 to hydraulic fluid under pressure and groove 19 to the fluid reservoir. In order to cater for this, the interior of the valve member 8 is connected via a second check valve 25 to the annular groove 19.

Instead of check valves 24 and 25, the ports 22 may be connected by a separate line to drain.

As shown in Figure 2, the auxiliary ports 22 are centrally disposed with respect to respective radial planes 23, but it is possible that the overall performance of the motor may be improved yet further by moving each of the ports 22 by a small angle relative to its associated radial plane 23. In this case, it will be necessary for the ports 22 to be displaced angularly when the motor is reversed in order that performance to the motor is uniform in both directions. To achieve this the ports 22 may be provided in a disc 26 (see Figure 4). The disc 26 is mounted in the motor body for limited angular movement defined by a fixed pin 27 which projects into an arcuate groove 28 in the disc. The disc 26 is moved angularly by frictional engagement with an end of the rotor 4 between its two extreme positions when the direction of rotation of the motor is reversed.

The output drive of the motor is taken from a drive member integral with or secured to the distribution valve member 8.

Instead of or in addition to providing the auxiliary ports 22 in the motor body or the disc 26, auxiliary ports could be provided in the rotor itself, one of which is shown in dotted lines in Figure 1 and designated reference numeral 22'.

Claims

1. An hydraulic motor comprising a toothed stator, a toothed rotor having one less tooth than the stator, a commutator valve operable by the rotor and being for sequentially connecting fluid chambers defined between the rotor and stator teeth with a hydraulic fluid source and drain via main ports in the motor body, and auxiliary ports to relieve fluid pressure in the chambers only when the latter are at maximum or substantially maximum volume.

2. The motor of claim 1, wherein the auxiliary ports are fixed in space relative to the motor body and are centrally or substantially centrally disposed with respect to respective radial planes bisecting the angle between respective pairs of stator teeth.

3. The motor of claim 1, wherein the auxiliary ports are provided in a member mounted in the motor body for limited angular movement between two extreme positions in which each of the auxiliary ports is equi-angularly or substantially equi-angularly displaced on opposite sides of its said respective radial plane.

4. The motor of claim 3, wherein the member is arranged such that it is moved from one extreme position to the other when the direction of rotation of the motor is reversed.

5. The motor of Claims 4, wherein the member frictionally engages an end of the rotor.

6. The motor of any one of the preceding claims, wherein the commutator valve includes a rotating distributor valve and a stationary outer valve member.

7. The motor of claim 6, wherein the auxiliary ports are connected to drain via the interior of the rotating distributor valve.

8. The motor of Claim 1 , wherein the auxiliary ports are provided in the rotor.

9. The motor of any one of Claims 2-5, wherein auxiliary ports are also provided in the rotor.

10. An hydraulic motor substantially as hereinbefore described with reference to, and as shown in, Figures 1-3 or Figures 1-3 as modified by Figure 4 of the accompanying drawings.