GB2269207A

GB2269207A - Pressurized fluid motors and drive units.

Info

Publication number: GB2269207A
Application number: GB9314521A
Authority: GB
Inventors: Gilles G Lemaire
Original assignee: Poclain Hydraulics France SA
Current assignee: Poclain Hydraulics France SA
Priority date: 1992-07-28
Filing date: 1993-07-13
Publication date: 1994-02-02
Anticipated expiration: 2013-07-13
Also published as: GB2269207B; JPH06213135A; FR2694342A1; DE4325315C2; DE4325315A1; FR2694342B1; GB9314521D0

Abstract

A pressurized fluid motor comprises a stator (1A-1B-1C) provided with two main external couplings (63, 64) for admission and for exhaust; a rotor (8-3) rotatable relative to the stator; two main internal ducts (55, 56) disposed inside the stator for the admission to and the exhaust from working chambers (14) in the rotor; a two-position valve (45) having a first position which establishes communication between the admission external coupling (63) and the admission internal duct (55), and between the exhaust external coupling (64) and the exhaust internal duct (56). In the second valve position, reached by exhausting a chamber (47), the main internal ducts are isolated from the main external couplings and the main internal ducts (55, 56) are put into communication with each other via a constricted secondary internal duct (66). The motor includes a locking member (42-43) for locking the rotor (8-3) relative to the stator (1A-1B-1C), the locking member being engaged when pressure is removed from a chamber (41) connected to the chamber (47). Movement of the valve to its second position initially results in hydrostatic braking until the speed of rotation of the rotor relative to the stator is less than a limiting speed of rotation at which speed a spring (32) operates the locking member (42, 43). <IMAGE>

Description

2-269207 PRESSURIZED FLUID MOTORS AND DRIVE UNITS Hydraulic circuits for

controlling hydraulic motors are already known. Such motors have multiple applications. Thus, certain hydraulic motors drive moving equipment in displacement at a maximum speed of about 30 kilometers per hour. It is often necessary to Provide braking for said motors and for the members they drive.

Also In known manner, such braking is provided by two distinct means: firstly by cutting off the feed of fluid under pressure to the motors, so that they operate as pumps and perform functional hydrostatic braking which Is effective but only insofar as the circuit is not damaged and in particular Insofar as the feed and exhaust ducts of the motors are not interrupted. To mitigate this risk, a safety brake is provided that is independent of the feed circuit and that is suitable for providing braking which, under certain circumstances, the motor can no longer provide.

The object of the invention is to provide a novel disposition which, when adopted, ensures that operation of the motor remains satisfactory with respect to the effective hydrostatic braking it may need to provide, even in the event of damage caused to the circuit itself. TO this end, the motor has been modified so that when isolated from the circuit It is Indeed capable of producing said hydrostatic braking. 30 Advantageously, a locking member that Is independent of motor operation Is added to the circuit, which member may be small in size since main braking is provided by the motor-itself. The invention thus provides firstly a stator provided with two main external couplings, respectively for fluid admission and for fluid exhaust; a rotor mounted to rotate relative to the stator; two main 2 internal ducts disposed inside said stator, respectively for fluid admission and for fluid exhaust; and a twoposition valve contained in the stator, the valve having a first position in which it establishes communication between the main external coupling and the main internal duct for fluid admission, and between the main external coupling and the main internal duct for fluid exhaust.

According to the invention, said two-position valve has a second position in which it isolates the main internal ducts from the main external couplings and puts the main internal ducts into communication with each other via a secondary internal duct included in the valve, and containing a constriction.

Preferably, said two-position valve includes a pressurized fluid member for selecting its position, and the stator is provided with a third external coupling, and an internal pilot duct connects said pressurized fluid member to said third external coupling.

The invention also provides a drive unit comprising a pressurized fluid motor according to one of the above definitions and further including a locking member for locking the rotor relative to the stator, the locking member being Interposed between said rotor and stator and being suitable for locking the rotor relative to the stator in any operating configuration in which the speed of rotation of the rotor relative to the stator is not more than a limiting speed of rotation. The following advantageous dispositions are also preferably adopted: 30 the two-position valve of the pressurized fluid motor includes a pressurized fluid member for selecting Its position, the stator being provided with a third external coupling and with a pilot internal duct connecting said pressurized fluid member of the two- position valve to the third external coupling, said locking member being coupled to a pressurized fluid control device which is connected via an internal control 3 duct to said third external coupling, the third external coupling being selectively put into communication with a source of fluid under pressure which corresponds to selecting the first position of the two-position valve, and to removing the locking of the rotor relative to the stator by the locking member; and the locking member either includes locking means constituted by two groups of teeth constrained to rotate respectively with the rotor and with the stator, or else It is a friction brake.

The main advantage of a motor of the Invention lies in its suitability for constituting an effective hydrostatic brake even if the ducts that normally feed It are interrupted. This is achieved by adopting the twoposition valve and by integrating it In the stator Itself of the motor, thereby eliminating external ducts connected to said valve and ensuring that hydrostatic brake operation will continue. Associating a locking member with the two-position valve gives rise to an elegant and effective embodiment of a safe drive unit.

The invention will be better understood and secondary characteristics and advantages will appear on reading the following description given by way of example.

The description and the drawings are naturally given merely as an indication and they are not limiting.

Reference is made to the accompanying drawings, in which:

Figure 1 is an axial section through a hydraulic motor of the Invention associated with a brake; and Figure 2 shows a hydraulic control circuit for the motor and brake of Figure 1.

The assembly shown in Figure 1 comprises a hydraulic motor and a brake with teeth that is Independent of the motor even though it is integrated therein.

Before describing this assembly, it should be observed that the solution proposed by the invention and 4 described as applied to a hydraulic motor extends more generally to application to any pressurized fluid motor. The assembly shown comprises: a hydraulic motor case comprising three portions 1A, 1B, and 1C that are assembled together by screws 2; a drive shaft 3 rotatably mounted relative to the case by means of conical roller bearings 4 disposed between the drive shaft and portion 1A of the case, the drive shaft 3 being provided with splines 5 inside the motor and with a flange 6 outside the motor for imparting rotary drive to an external body, e.g. a vehicle wheel, with the axis of rotation being the axis 7; a cylinder block 8 having a central bore provided with splines 9 that co-operate with the splines 5 on the drive shaft 3 to constrain the drive shaft 3 to rotate with the cylinder block 8; cylinders 10 formed in the cylinder block 8, disposed radially relative to the axis of rotation 7 and regularly spaced apart angularly around the axis of rotation 7; pistons 11 slidably mounted in the cylinders, one piston per cylinder, each piston carrying a roller 12 at its outer end that Is mounted on said piston to rotate about an axis parallel to the axis of rotation 7 and that is suitable for bearing against the inside face of portion 1B of the case, which is shaped as a cam 13 having a plurality of undulations; working fluid chambers 14 delimited inside the cylinders 10 by the pistons 11; 30 a communication face 15 provided on the cylinder block 8, which face is plane and perpendicular to the axis of rotation 7; cylinder ducts 16 formed in the cylinder block 8 and connecting each working fluid chamber 14 to said ' communication face 15 and opening out in said face via orifices centered on a circle about the axis 7 and regularly spaced apart angularly; a stepped recess 17 formed in portion 1C of the case and circularly symmetrical about the axis 7; an internal fluid distributor valve 18 having a stepped cylindrical outer face 19 that is complementary in shape to the recess 17, and having a plane distribution face 20 that is substantially perpendicular to the axis 7 and that is held pressed against the communication face 15; distribution ducts 21 and 22 formed in the internal fluid distributor valve 18 and constituting two groups of ducts, the distribution ducts 21 communicating with an annular groove 23 formed between the cylindrical face 19 and the recess 17, and the distribution ducts 22 communicating with an annular groove 24 formed between the cylindrical face 19 and the recess 17, the distribution ducts 21 and 22 also opening out Into the distribution face 20, being centered on the same circle as the cylinder duct orifices 16, being regularly spaced apart angularly, and being disposed In an alternating configuration, with each orifice of a distribution duct 21 being disposed between two orifices of distribution ducts 22, and vice versa; a bore 25 of the internal distributor valve 18 and a bore 26 of portion 1C of the case, both serving to receive a cylindrical shaft 27 having splines 28 on one of its ends suitable for co-operating with the splines 9 of the cylinder block 8 to constrain said shaft 27 and cylinder block 8 to rotate together about the axis 7, while allowing the shaft 27 to slide freely in an axial direction relative to the cylinder block 8 parallel to the axis 7, the shaft 27 also having a blind axial recess 29 whose sole opening 30 opens out facing the solid transverse end 31 of the drive shaft 3 inside the motor, a compression spring 32 being contained in the recess 29 and bearing against said transverse end 31, urging the shaft 27 away from the drive shaft 3; 6 a bore 33 in portion 1C of the case which receives, with radial clearance J, a piston 34 secured to the cylindrical shaft 27, an outer cylindrical face 35 of said shaft 27 passing through another bore 38 of portion 1C of the case with a sealing ring 36 being interposed, and also being guided in axial sliding parallel to the axis 7 by a bearing-forming bush 37 interposed between Itself and portion 1C of the case; a case cover 39 fixed to portion 1C of the case by screws 40 and defining a chamber 41 between itself, the bore 33, and the piston 34; and a plurality of teeth 42 secured to the cover 39 and suitable for receiving in the gaps between one tooth and the next, teeth 43 secured to the piston 34 and disposed facing the teeth 42, penetration of the teeth 42 between the teeth 43 and of the teeth 43 between the teeth 42 being achieved automatically under drive from the spring 32 which urges the piston 34 towards the cover 39 and which therefore also urges the teeth 43 towards the teeth 42 and towards the gaps between them, with penetration happening as soon as the relative speed of rotation of the piston 34 is less than or equal to a limiting speed of rotation that is a constant for any given set of teeth 42, 43. By way of example, teeth 42 and 43 have been caused to Interpenetrate using mechanisms manufactured and tested for speeds of rotation less than or equal to revolutions per minute. The manufacture of such teeth 42 and 43 is known and does not form part of the present Invention.

The assembly shown further includes:

a bore 44 formed in portion 1C of the case, and in the example described, having an axis parallel to the axis 7; a slide 45 mounted to slide axially inside the bore 44 and prevented from rotating relative to the bore 44 (and portion 1C of the case); 7 a threaded plug 46 for closing the bore 44 after the slide 45 has been installed; two chambers 47 and 48 formed between the slide 45 and the bore 44, at respective axial ends thereof; two annular grooves 49 and 50 formed In an axial face 51 of the slide 45; a spring 52 contained in the chamber 48 and urging the slide 45 in the direction that tends to reduce the volume of the chamber 47; and the following ducts which are formed in portion 1C of the case:

a duct 53 establishing communication between the chamber 48 and an enclosure 54 defined by the case 1A-1B-1C. thus enabling leaks due to operation of the hydraulic motor to be evacuated from the enclosure 54 via the chamber 48; ducts 55 and 56 providing communication between the annular grooves 23 and 24 and the bore 44, and also communicating with grooves 49 and 50 respectively when the volume of the chamber 47 is at a maximum; a duct 57 establishing communication between the chamber 47 and the chamber 41; ducts 58, 59, 60, and 61 connected to external couplings 62, 63, 64, and 65 on portion 1C of the case, duct 58 communicating with the chamber 48 and enabling fluid leaks contained in the chamber 48 (and in the enclosure 54) to be evacuated from the chamber 48, the duct 61 communicating with the chamber 47, and the ducts 59 and 60 communicating with the grooves 49 and 50 when the volume of the chamber 47 is at a maximum, and thus also communicating under such circumstances with the ducts 55 and 56 respectively; and ---aduct 66 of small section designed so that the duct 66 constitutes a hydraulic constriction, which duct is formed in the slide 45 and opens out into Its cylindrical face 51, communicating with the ducts 55 and 56 when the volume of the chamber 47 is at a minimum.

8 It should be observed firstly that when the volume of the chamber 47 is at a maximum., the ends of the duct 66 that open out in the cylindrical face 51 of the'slide 45 are closed by the bore 44, and secondly that when the volume of the chamber 47 is at a minimum, the ducts 59 and 60 are closed by the cylindrical face 51 of the slide 45, and are therefore isolated from the ducts 55 and 56, respectively.

External ducts 67, 68, 69, and 70 are connected to the couplings 62, 63, 64, and 65 respectively.

In addition to the assembly of Figure 1, given overall reference 71, the circuit shown in Figure 2 comprises:

a variable flow rate main pump 72 provided with two main couplings 73 and 74 suitable respectively for constituting either a suction coupling and a delivery coupling or else conversely a delivery coupling and a suction coupling, the pump also having a member 75 for controlling the delivered flow rate; a secondary pump 76; a two-position fluid distribution valve 77; a pressure relief valve 78 for providing protection against excess pressure; two check valves 79 and 80; a fluid tank 81 that Is not under pressure; and the following ducts:

above-mentioned ducts 68 and 69 connected to couplings 73 and 74 respectively; duct 67 connected to the fluid tank 81; duct 70 connected to fluid distribution valve 77; suction and exhaust ducts 82 and 83 associated with the secondary pump 76 and respectively connected to the fluid tank 81 and to the fluid distributor valve 77; two ducts 84 and 85 firstly connected respectively to the ducts 68 and 69 and secondly connected in common to a duct 86 which is itself a branch 9 connection on the delivery duct 83, the check valve 79 being disposed in the duct 84 and allowing fluid to flow from the duct 86 towards the duct 68, and the check valve 80 being disposed in the duct 85 and allowing fluid to flow from the duct 86 towards the duct 69; a duct 87 branching from the duct 86 and connected to the fluid tank 81 via the pressure relief valve 78; and a duct 88 connecting the fluid distributor valve 77 to the fluid tank 81.

The two positions of the fluid distributor valve 77 correspond:

firstly to putting ducts 83 and 70 into communication and closing of f duct 88, thereby putting the chamber 47 in its maximum volume position, thereby establishing the following connections: ducts 68-63-55; ducts 69-60-56; and the chamber 41 to its maximum volume so that the teeth 43 are disengaged from the teeth 42 and vice versa, thus ensuring that the drive shaft 3 is not prevented from rotating relative to the case IA-1B-1C; and secondly to putting the ducts 70 and 88 into communication and closing off the duct 83 in the fluid distributor valve 77, thereby causing the chamber 47 to take up its minimum volume position and thus closing the ducts 59 and 60, putting the ducts 55 and 56 into communication with each other via the duct 66 that forms a hydraulic constriction, removing pressure from the chamber 41 so that the spring 32 has a preponderant effect tending to cause the teeth 42 and 43 to engage mutually; and finally, once the speed of rotation of the shaft 27 relative to the case IA-1B-1C becomes less than or equal to the limiting speed of rotation at which mutual engagement of the teeth 42 and 43 is possible, locking the shaft 27 and thus the drive shaft 3 relative to the case 1A1B-1C.

The operation that is obtained is described below, assuming that the member 75 for adjusting the flow rate of the main pump 72 is disposed in such a manner that coupling 73 constitutes the delivery coupling of said main pump. Naturally, displacing the adjustment member would cause the coupling 74 to become the delivery coupling with the sole effect of reversing the direction of rotation of the drive shaft 3 of the motor 71.

Also in known manner, the secondary pump 76 delivers fluid under pressure to the ducts 83 and 86, thereby boosting pressure In the ducts 84-68 and 85-69 and thus avoiding any risk of cavitation in the main pump 72.

When the fluid distributor valve 77 Is placed in Its first position, the fluid under pressure delivered by the main pump 72 to the duct 68 penetrates into the groove 23 and feeds the distribution ducts 21. Since the teeth 42 and 43 are then not in mutual engagement, the drive shaft 3 is normally driven in rotation relative to the case 1A 1B-1C.

When the user places the fluid distributor valve 77 in its second position, the slide 45 causes the ducts 59 and 60, and consequently the ducts 68 and 69 to be closed. The motor 71 Is thus Isolated from its feed of fluid under pressure. In addition, because the ducts 55 and 56 are put into communication via the duct 66 that forms a hydraulic constriction, powerful hydrostatic braking Is obtained of the cylinder block 8 and thus of the drive shaft 3 relative to the case 1A-1B-1C. This braking causes the rotation of the drive shaft 3 to be slowed down relative to the case until the limiting speed is reached at which the teeth 42 and 43 engage mutually, thereby locking the drive shaft 3 relative to the case 1A-1B-1C.

The user may also have placed the fluid distributor valve 77 in its first position, while due to an unexpected accident, the duct 70 may be ruptured. Under such circumstances, the pressure in the duct 70 drops 11 suddenly, and although the fluid distributor valve Is still in its first position, the slide 45 moves under drive from the spring 52 and braking then takes place as though the fluid distributor valve 77 had been placed in 5 its second position.

Thus, the drive shaft 3 is initially slowed down by hydrostatic braking, and the drive shaft 3 is subsequently locked as described above when describing operation corresponding to the fluid distributor valve 77 being in its second position. It can thus be seen that In the event of an accident, safety braking and locking are obtained automatically. This advantageous configuration is obtained because of the fact that the slide 45 is contained in the case 1A-1B-1C and therefore continues to operate normally, even after the duct 70 or the duct 83 has ruptured.

The system described uses a locking member having teeth. By way of equivalent, the locking member with teeth 42, 43 could be replaced by a disk brake which is released under the control of fluid under pressure, and which brakes in response to preponderant force from a spring acting on a stack of disks. Several known embodiments of such a brake are described in FR-A-2 529 978. Naturally, depending on the dimensions selected for such a disk brake, locking may be obtained either suddenly from a non-zero limiting speed, or else after slowing down progressively to zero speed. Under such circumstances, the above- mentioned limiting speed is zero.

A first application of the invention lies in driving a roller compacter at a maximum speed of about 15 kIlometers per hour, with the hydraulic motor having a corresponding maximum speed of rotation of about 100 revolutions per minute. The maximum pressure of the hydraulic fluid is about 450 bars. In conventional manner, the hydraulic motor is mounted on the equipment by means of resilient lugs whose main function is to 12 filter compacting vibration, but whose resilience also makes it possible to absorb the Jolts or shocks that may be caused by the rotor being locked relative to the stator.

Another application lies in making a moving agricultural machine mounted on wheels provided with tires, and having a maximum speed of 25 kilometers per hour, which corresponds to a maximum speed of rotation of the hydraulic motor of about 200 revolutions per minute.

The maximum pressure is about 450 bars. Under such circumstances, jolts or shocks that may be caused by the rotor locking relative to the stator are absorbed by the 'resilience of the tires.

13

Claims

1/ A pressurized fluid motor comprising:

a stator (1A-1B-1C) provided with two main external couplings (63, 64), respectively for fluid admission and for fluid exhaust; a rotor (8-3) mounted to rotate relative to the stator; two main internal ducts (55, 56) disposed inside said stator, respectively for fluid admission and for fluid exhaust; and a two-position valve (45) contained In the stator (1A-1B-1C), the valve having a first position in which it establishes communication between the main external coupling (63) and the main internal duct (55), for fluid admission and between the main external coupling (64) and the main internal duct (56) for fluid exhaust, characterized in that said two-position valve (45) has a second position in which it isolates the main internal ducts (55, 56) from the main external couplings (63, 64) and puts the main internal ducts (55, 56) into communication with each other via a secondary internal duct (66) included in the valve (45), and containing a constriction (66).

2/ A pressurized fluid motor according to claim 1, characterized in that said two-position valve includes a pressurized fluid member (47) for selecting its position, and the stator (1A-1B-1C) is provided with a third external coupling (65), and an internal pilot duct (61) connects said pressurized fluid member (47) to said third external coupling (65).

3/ A drive.unit including a pressurized fluid motor according to claim 1 or 2, and characterized in that it further Includes a locking member (42-43) for locking the rotor (8-3) relative to the stator (1A-1B-1C), the locking member being interposed between said rotor and 14 stator and being suitable for locking the rotor relative to the stator in any operating configuration in which the speed of rotation of the rotor relative to the stator is not more than a limiting speed of rotation. 5 4/ A drive unit according to claim 3, characterized in that the two- position valve (45) of the pressurized fluid motor includes a pressurized fluid member (47) for selecting its position, the stator being provided with a third external coupling (65) and with a pilot internal duct (61) connecting said pressurized fluid member (47) of the two-position valve to the third external coupling (65), said locking member (42-43) being coupled to a pressurized fluid control device (41) which is connected via an internal control duct (57-47-61) to said third external coupling (65), the third external coupling (65) being selectively put into communication (77) with a source of fluid under pressure (76) which corresponds to selecting the first position of the two-position valve (45), and to removing the locking of the rotor (8-3) relative to the stator (1A-1B-1C) by the locking member (42-43).

5/ A drive unit according to claim 3 or 4, characterized in that the locking member includes locking means constituted by two groups of teeth (42, 43) constrained to rotate respectively with the rotor and with the stator.

6/ A drive unit according to claim 3 or 4, characterized in that the locking member Is a friction brake.

7/ A drive unit including a pressurized fluid motor and substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.