GB2109467A - Fluid-pressure torque motor - Google Patents

Abstract

A vane-type torque motor 1 comprises a rotary piston 6 with radially-sliding vane elements, which engage with a fixed cam-ring, or "plate", 8, the pressure of the working fluid being transmitted to concentric annular pressure-balancing recesses 26, 27 in a fixed cheek-plate 25 by way of check valves 28, 30. The said pressure may be also transmitted to the inner edges of the vane elements from said recesses by way of bores 32, 33. <IMAGE>

Description

SPECIFICATION Vane-type torque motor The present invention relates to a vane-type torque motor with a rotary piston arranged in a housing and having vane elements radially slidably supported in it, with a cam plate providing cam curves co-operating with the vane element to form pressurisable working chambers with lateral housing flanges and an intermediate disc interposed between a lateral housing flange and the rotary piston, said intermediate disc including on its side remote from the rotary piston actuatable pressurised partial compensation surfaces.

Known vane-type torque motors are of the following principal design. A rotary piston located centrically in the motor possesses a plurality of slots in which vane elements are radially slidably arranged. Individual cells are formed in that the vane elements, while they are pressed with their heads radially against the cam curve of the encompassing cam plate seal in a circumferential direction, and in that laterally housing flanges are connected to the cam plate and provide for the sealing of the compartment in an axial direction.

Radially inwardly, the cells are bounded by the rotary piston which is rotatable and fitting between the lateral housing flanges with small clearance to obtain low leakage. During operation, the hydraulic pressure acting above and beneath the vane elements will be controlled such as to cause a resultant force in the phases in which the vane elements seal, which force urges the latter radially outwardiy against the cam plate. As in specific phases the pressure force and the centrifugal force do not suffice to urge the vane elements against the cam plate, additional springs are arranged to assist therein.

The cam track of the cam plate comprises normally two to six cam curves to attain a balancing of the hydraulic forces that act radially on the rotary piston and to utilise the mounting space. The movement and torque delivery of the rotary piston is effected by the pressure oil which flows into the increasing cell and acts on vaneelement surfaces of different size, thereby producing a resultant circumferential force. The cell adjacent to the working chamber that is subject to high pressure performs in each case the separating function with respect to the adjacent cell which decreases during action of the rotary piston and from which oil is displaced to the return passage. In this arrangement, fluid flow and return takes place in an axial direction mostly, the respective channels being accommodated in one or in both of the lateral housing flanges.

In the known vane-type motors, one of the housing flanges is conventionally designed as a retaining flange and the cther as a control flange.

The retaining flange seives to receive the motor and carries a roller bearing in which the hydraulically power-balanced rotary piston is radially guided: in an axial direction, the guiding is taken care of by the contact surfaces of an intenmediate disc and the control flange. The running clearance of the rotary piston necessary for functioning results from the latter piston being undersized in relation to the cam plate. Besides, this running clearance is adapted to the working pressure -- small clearance at high pressure to attain low leakage - in that interposed between rotary piston and retaining flange is the intermediate disc which has a pressurised annular compensation surface on its back side remote from the rotary piston.A system of channels and pockets in the control flange and in the intermediate disc, respectively, serves to control the oil flow to respectively from the working chambers and to respectively connect the rotary piston's under-vane chambers disposed beneath the vane elements to the feed or return pressure.

A separate pipe connection is provided for the discharge of the lubricating and leak oil that escapes from the lateral contact surfaces of the rotary piston. The motor delivers the torque via an involute-tooth system which is machined in the central bore of the rotary piston; in this design, said motor may be mounted in simple manner on the shaft providing centering of the machine to be driven.

When talking of vane-type motors, a difference is principally made between so-called constant motors, e.g. motors admitting only a substantially uniform rotational speed of the motor at constant oil flow, and torque motors, e.g. motors adapted to be switched stepwise to varying absorptive capacities and thus varying rotational speeds of the motor by virtue of directional control valves.

The known constant motors are reversible.

They may likewise be used to operate as pumps within the predeterminable performance characteristics; therefore, these motors may also be used for braking.

A vane-type torque motor of the type initially referred to is known from German printed and published patent application 22 28 506. In this motor, the control flange provided for in constant motors is substituted by a so-called switch flange.

The latter contains a three-position directional control valve enabling the inflowing oil to be supplied via corresponding annular chambers and channels optionally to a varying number of working chambers of different size. To this effect, the known motor comprises different cam curves in the cam plate, three of which being designed each with varying cams and varying partial absorption quantities V1 and V2 resulting therefrom. As a consequence, the following amounts of pressurisation can be attained by the three positions of the switching valve: Step I - partial absorption quantity V; Step II - partial absorption quantity V2; Step lli -- partial absorption quantity V1 + V2.

The respective unpressurised chambers generate an almost pressureless oil circulation in the motor from which ensues only a minor loss that is comparable approximately to the losses of the unloaded co-rotating wheei pairs of a toothed-wheel gearing. The changing over of the motor is done normally by manual actuation of the directional-control-valve slider, but can also be effected hydraulically or pneumatically. In the event of a variable torque motor, the back side of the intermediate disc can no longer be designed in only one undivided annular surface because, in this case, the running clearance of the rotary piston would be too much restricted in the area of the disconnected chambers and there would be the danger of seizing.It is therefore common practice to subdivide the compensation surfaces into partial surfaces corresponding to the numbers of chambers to be pressurised, and to pressurise accordingly. To this end, six reniform partial surfaces are arranged in the known torque motor containing six working chambers.

As is the case with all known vane-type variable torque motors, also the variable torque motor described herein is applicable for merely one direction of rotation. Admittedly, this is sufficient in many cases of application requiring to utilise only the general advantages of variable torque motors which consist in a loss-free variation of the driving speed and the driving torque by hydraulic means and in operation at varying operational speeds with constant capacity without being being the need for a variable displacement-pump. In many other cases of application, however, for instance in ground borers, torque motors providing two directions of rotation are required or desirable.In such reversible torque motors, the application of pressure to the partial surfaces would entail great effort, since there would be the necessity to provide for six partial surfaces twelve check valves enabling the connection of each partial surface to the respective pressure channel and closure relative to the respective return channel.

It is therefore an object of the present invention to provide a vane-type torque motor of the type initially referred to which affords a simple design and manufacture favourable with respect to costs, in particular by using a least possible number of check valves.

According to the present invention, there is provided a vane-type torque motor including a rotary piston arranged in a housing and having vane elements radially slidably supported in it, a cam plate providing cam curves co-operating with the vane elements to form pressurisable working chambers, lateral housing flanges and an intermediate disc interposed between a lateral housing flange and the rotary piston, said intermediate disc including on its side remote from the rotary piston actuatable pressurised partial compensation surfaces, characterised in that there are provided at least two partial compensation surfaces which are designed as undivided annular surfaces arranged concentrically one to the other.

If this solution incorporates for instance two partial compensation surfaces, a switch step lli in which position all working chambers are subject to pressure arranges for both partial compensation surfaces to be connected to the operating pressure, while the switch steps I and II provide for only one partial compensation surface each to communicate with said pressure. Therefore, considerably less effort is needed to apply pressure to the annular surfaces than is the case with the known reniform partial surfaces, because each annular surface necessitates the provision of only two check valves, respectively, to establish connection to the alternately pressure-supplying feed and return passages of the motor.

In an advantageous embodiment of the present invention, the partial compensation surfaces have differently sized effective surfaces.

In an improvement of the idea of the invention, the partial compensation surfaces are adapted to be pressurised individually or altogether in dependence upon the number of pressurised working chambers connected.

The present invention will be described in more detail in the following by way of one embodiment illustrated in the accompanying drawings, in which: Fig. 1 is a cross-section through a vane-type torque motor, with the intermediate disc being drawn out; Fig. 2 is a section of the vane-type torque motor according to Fig. 1 taken along the line Il-Il.

The vane-type torque motor 1 illustrated comprises a housing 2 with a pressure-medium inlet 3 and a pressure-medium outlet 4. In the interior of the housing 2 there is a rotary piston 6 connected to a shaft 5 in a torsionally secured manner with radially displaceable vane elements 7, 7', 7" etc., which latter slide along a cam curve provided at a cam plate 8.

The space created between the rotary piston 6 and the cam plate 8 is limited on one side by a retaining flange 9 and on the other side by a switch flange 1 0. Said switch flange 10 contains orifices 11 to 22 leading to the chamber established between rotary piston 6 and cam plate 8 and enabling the vane-type torque motor to be applied by pressure medium and serving as a pressure-medium exhaust. The vane-type torque motor 1 is so designed that several orifices 11 to 22 can be controlled by choice in order to obtain different torques or rotational speeds, respectively.

Thus it is possible, for instance, to pressurise three working chambers via the orifices 14, 18 and 22.

In this case, the orifices 15, 1 9 and 11 must be connected to the p-essure-medium outlet 4.

In order to cause variation in the rotational speed of such vane-type torque motors, a control device is provided in the form of a directional control valve 23 permitting, for example, the orifices 12, 16 and 20 to be pressurised in addition. Of course, it is also possible that the working chambers associated with these orifices have an absorptive capacity which is different from that of the working chambers associated with the orifices 14, 18 and 22, whereby a variation of the rotational speed would be achieved.

Interposed between the rotary piston 6 and the retaining flange 9 is an intermediate disc 25. On its side remote from the rotary pistion 6, said intermediate disc 25 contains two circumferential annular partial compensation surfaces 26 and 27 which are designed as grooves in the intermediate disc and are sealed relative to the opposite housing wall. The inner partial compensation surface 26 is pressurised via check valves 30 and 31 (Fig. 1), while the outer partial compensation surface 27 is pressurised via check valves 28 and 29. The check valves 29 and 31 are positioned opposite to the reniform orifices 1 5 and 13, the check valves 28 and 30 opposite to the reniform orifices 16 and 14.

Depending upon the position of the control slider 24 of the directional control valve 23 and upon the direction of rotation, the orifices 1 6 and/or 1 4 can be feed or return openings. The respective other orifice 1 5 and 13 will then be return or feed openings, respectively.

Thus, the partial compensation surfaces 26, 27 will be connected to the operating pressure each via the check valve that lies opposite to the reniform orifice. The other check valve which terminates in the same partial surface will then close to prevent return flow.

If the control slider 24 is positioned in the switch step I, the inner partial compensation surface 26 will be pressurised by the port 3 subjected to pressure via the ball retaining valve 30. The check valve 31 closes relative to the return orifice. Corresponding to the slider's position (switch step 1), the outer partial compensation surface 27 will not be acted upon by the operating pressure, since return flow level prevails at both orifices. The compensation of the axial gap amount will thus take place merely by virtue of the inner partial compensation surface.

Accordingly, the switch step II provides for pressurisation of the outer partial compensation surface 27, while the inner partial compensation surface 26 is unpressurised and has no compensating effect as a result. If the control slider is urged to assume the mid-position (switch step Ill), all working chambers will be acted upon by the operating pressure. The maximum compensating effect will be required in this switch step shown in Fig. 1. Consequently, the outer and the inner partial surface is supplied with pressure via the check valves 28 and 30. The check valves 29 and 31 close with relation to the respective return orifice. In the reverse direction of rotation which occurs merely in the switch step Ill in this vane-type torque motor, both partial compensation surfaces 26, 27 are subjected to the operating pressure via the check valves 29 and 31. The check valves 28 and 30 close relative to the control orifices which bear against the return passage in this stage.

The pressurised partial compensation surface 26, 27 serves to maintain through bores 32 and 33 the pressure prevailing beneath the vane element 7, 7', 7" etc., in the partition area.

Claims (4)

1. Vane-type torque motor including a rotary piston arranged in a housing and having vane elements radially slidably supported in it, a cam plate providing cam curves co-operating with the vane elements to form pressurisable working chambers, lateral housing flanges and an intermediate disc interposed between a lateral housing flange and the rotary piston, said intermediate disc including on its side remote from the rotary piston actuatable pressurised partial compensation surfaces, characterised in that there are provided at least two partial compensation surfaces which are designed as undivided annular surfaces arranged concentrically one to the other.

2. Vane-type torque motor as claimed in claim 1, characterised in that the partial compensation surfaces provide effective surfaces of different size.

3. Vane-type torque motor as claimed in claim 1 or 2, characterised in that means are provided to pressurise the partial compensation surfaces individually or altogether depending on the number of pressurised working chambers connected.

4. Vane-type torque motor substantially as described with reference to the accompanying drawings.