GB2252799A

GB2252799A - Radial piston motor having a mechanical brake assembly

Info

Publication number: GB2252799A
Application number: GB9203231A
Authority: GB
Inventors: Sinclair Cunningham; Peter Wusthof
Original assignee: Mannesmann Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 1991-02-15
Filing date: 1992-02-14
Publication date: 1992-08-19
Anticipated expiration: 2012-02-14
Also published as: FR2672940B1; FR2672940A1; GB2252799B; GB9203231D0; DE4104712C2; DE4104712A1

Abstract

A radial piston motor for operation together with a mechanical brake assembly. For the release of the brake assembly pressure medium is derived from the radial piston motor itself and is supplied to the brake assembly. The pressure medium is supplied to a brake chamber 35 via a ring gap 41. Pressure medium reaches the gap 41 either through internal leakage (Fig. 6 not shown) or via a valve 40 from whichever of the two ports A, B is at the lowest pressure. In use a booster pump (65, Fig. 4) may supply the lower pressure port A or B from which the pressure medium is directed to release the brake. <IMAGE>

Description

1 2252799 RADIAL PISTON ENGINE HAVING A NECHMICAI, BRAXE ASSEMBLY The

present invention relates to radial piston engine, and preferably to a radial piston motor.

More specifically, the present invention relates to a radial piston motor which can be operated as a pump for the purposed of braking. Moreover, said radial piston motor may be equipped with a mechanical brake assembly which, for instance, is adapted to brake the shaft of the radial piston motor if no hydraulic pressure is available. More specifically, the present invention relates to a radial piston motor used for driving a construction vehicle, for instance, a levelling roller. In this instance, the hydraulic piston motor is arranged in a closed circuit together with a main pump as well as a booster pump.

Many types of radial piston engines are known. Such engines are frequently used together with a mechanical brake assembly, typically a brake assembly of the lamella or disc type.

F Frequently, the brake discs are forced against each other by means of a spring, such that the brake is in its applied condition. when no pressure medium is supplied to the brake assembly. For the release of the brake assembly pressure medium, preferably hydraulic oil, is supplied to a brake chamber with the consequence, that a brake piston is moved and acts against the force of said spring so as to release the brake assembly. The present invention specifically relates to a radial piston engine used together with such a brake assembly.

When using a radial piston motor together with a mechanical brake assembly and a hydraulic main pump together with a booster pump for operating said radial piston motor, then the pressure medium required for the release of the brake is frequently taken from the booster pump and supplied to the brake chamber. An inner seal ring is generally required in such a case between the brake chamber and the radial piston motor. However, such a 2 design is disadvantageous in sofar as due to the existing dynamic forces leakages may occur.

It is an object of the present invention to design a radial piston engine, specifically a radial piston motor operated together with a mechanical brake assembly. such that the. disadvantages of the prior art are avoided. Also, the radial piston motor and its brake assembly should be of a simple and low cost design providing high operating security.

According to the present invention it is provided that the pressure medium required for actuating, preferably releasing, the brake assembly is taken directly from the radial piston engine and not from the booster pump. Preferably, the pressure medium is taken from the inside of the radial piston engine and is immediately supplied to the brake assembly which is flanged directly to the radial piston engine. Preferably, the radial piston engine and the brake assembly form an integrated unit. In this manner short and protected paths for the pressure medium flowing to the brake assembly are obtained.

Preferably, the supply of the pressure medium from the radial piston engine to the brake assembly is automatically controlled by means of a valve. It is preferred to integrate said valve into the radial piston engine, specifically into the commutator of the radial piston engine.

In a first aspect of the invention the pressure medium required for the actuation of the brake assembly is taken from the control chambers of the engine and supplied to the brake assembly. Specifically, the control chambers are designed as annular grooves adapted to be connected to user ports of the engine.

Ina second aspect of the invention, leakage oil can be used for actuating the brake assembly. In the radially inner area of the radial Piston engine located between the rotor and the commutator, leakage oil exits adjacent to the shaft supporting 3 the rotor and flows in a direction towards the inside. This leakage oil can be used, after a certain pressure has built up, for actuating. specifically for releasing, the brake assembly. Preferably. said leakage oil is guided to the brake assembly along an annular gap extending between the shaft and the commutator. There,, the leakage oil is supplied to the brake chamber. Preferably. the brake chamber is connected via a valve to the tank. said valve being adjusted to the brake release pressure.

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

Fig. 1 is a longitudinal sectional view of a first preferred embodiment of a radial piston motor with a brake assembly connected thereto, exemplifying the first aspect of the invention as shown in Fig. 4; Fig. 2 is a detail of Fig. 1; Fig. 3 is a detail of Fig. 2; Fig. 4 shows schematically a first aspect of the invention which is realized by the embodiment of Fig. 1 to 3; Fig. 5 shows schematically a second aspect of the invention; Fig. 6 is a longitudinal sectional view similar to Fig. 1 illustrating the second aspect of the invention; Fig. 7 is a longitudinal Sectional view of a hydraulic motor with the brake assembly being enclosed by the motor housing, said design again realizing the second aspect of the invention.

In the following description reference will be made to a radial piston motor. However. this term should be interpreted more generally also as a radial piston engine, particularly in few of

4 the fact that in a preferred embodiment the radial piston motor does operate as a radial piston pump for the purposes of hydraulic braking.

As shown in Fig. 1 a radial piston engine (radial piston motor) 100 comprises a housing consisting of a first housing half 1 and a second housing half 2. Between said two housing halves 1 and 2 a cam disc 3 is located. By means of mounting bolts 4 said two housing halves and said cam disc 3 are mounted together to form a fixed and compact unit.

In said housing half I a shaft 5 is rotatably mounted by means of ball bearings 6, 7. A rotor 10 is mounted on the shaft 5. For the fixed support of the rotor 10 the shaft 5 is provided with splines in the area where the rotor 10 is mounted. The rotor 10 is designed as a cylinder block and comprises around its circumference equally spaced bores 11 which are adapted to receive pistons 12. Each piston 12 comprises in its radially outer area a recess adapted to receive a bearing dish 13 and a cylindrical roller 14. Said rollers 14 are supported by a cam path 17 of the cam disc 3.

In the radially lower area of each piston 12 a circumferential groove is provided adapted to receive the piston ring. The piston chambers formed by said bores are connected via axially extending bores 21 to axially extending control bores 22. The control bores 22 are located in a control sleeve or commutator 24 fixedly mounted in said second housing half 2. Bores 21 are operatively connected with said control bores 22. The commutator 24 borders circumferential annular grooves or control chambers 25, 26 which are connected in a manner not shown with customary ports for supplying and removing the pressure medium. Preferably, two such ports (A and B in Fig. 4) are provided. Depending on the position of said bores 11 with respect to the control bores 22, said bores or piston chambers 11 are either connected with a pressure source or with tank, so as to impart a rotory moment onto the rotor 10 (operation of a motor) - Preferably, the two ports of the radial piston motor, which are connected with the control chambers 25 and 26. are further connected as it is shown in Fig. 4 with a pump, as it will be explained below in more detail.

Referring again to Fig. 1 it can be noted that a brake assembly 30 is fixedly mounted to the second housing half 2 by means of bolts 29. The brake assembly 30 comprises a cup-shaped housing 31 into which a shaft extension 32 of the shaft 5 extends. Said shaft extension 32 supports brake discs or lamellas. Further, the housing 31 supports in a well known manner additional brake discs or lamellas adapted for cooperation with said first mentioned disks. Within said housing 31 a brake piston 33 is reciprocally mounted. If no pressure medium is applied a spring 34 (in Fig. 1) forces the brake piston 33 leftwardly so that the discs or brake discs are in engagement with the result that the shaft 5 is braked. Between the housing 31 and brake piston 33 a brake chamber 35 is formed. The brake chamber 35 is connected via a conduit 36 and a pressure relief valve 37 to tank 38. The brake piston 33 is guided in said shaft extension 32.

In the embodiment shown in Fig. 1 a switching valve 40 is located in the commutator. Said switching valve 40 is adapted to connect either the control chamber 25 (connected to port A) or the control chamber 26 (connected to port B) to the brake chamber 35. The connection between the switching valve 40 and the brake chamber 34 is preferably provided by a ring gap 41. The ring gap 41 is located between the commutator 40 and the housing half 2 on the one hand. and the shaft 5 on the other hand. The connection between the switching valve 40 and the brake chamber 34 continues from the ring gap 41 via a radial gap 42 and further via the disc area 43 to the brake chamber 35.

As it is shown. and as it was already mentioned. the switching valve 40 is preferably located in the commutator 24. It is also conceivable to locate the switching valve 40 in the housing, for instance directly in the housing half 2 and to provide possibly a different connection to the brake chamber 35.

6 Referring now to Fig. 2 and 3 the design of the switching valve 40 will be explained. The switching valve 40 is located in the annular-shaped commutator 24 which is, at its outer circumference, of a stepped design. The commutator 24 is located in a correspondingly stepped bore in the housing half 2 with seals being provided in the manner as shown in Fig. 1. A boro 47 in said commutator 24 extends in parallel with respect to the longitudinal axis 46 of the radial piston motor 100. In said bore 47 a valve spool 48 is reciprocally mounted. Three radially extending channels 49, 50 and 51 end in said bore 47 in the area of broadend annular recesses 52, 53 and 54 which are adapted to form control edges. The radial channels 49, and 50 extend to said control chambers 25 and 26. Said control chambers 25 and 26, in turn, are connected with ports A, B. The annular channel 51 ends in the ring gap 41.

The valve spool 48 comprises two end faces 55, 56. Each one longitudinal bore 57 and 58, respectively, extends from said end faces 55 and 56, respectively. inwardly. so as to provide the connection to the respective more distantly located annular recess 59 and 60, respectively.

The function of the switching valve 40 is obvious for a skilled person. Fig. 2 discloses the switching valve 40 in the position for which the pressure at A is larger than the pressure at B. In this manner the lower pressure at B (which is normally increased by a booster pump yet to be described) is provided at the radial channel 51 and thus-in the annular gap 41.

Fig. 4 is a circuit diagramm. of the radial piston engine loo of the invention together with a main pump 64 and a booster pump 65 arranged in a closed hydraulic circuit 66. The schematically shown brake assembly 30 can be seen as well as the motor shaft 5,, the switchig valve 40 as well as the two ports A and B. The main pump has two ports A' and B1, while the ports of the booster pump 65 are referred to by P and T. The two ports A and A' are connected by a line 67 and the ports B and BI are 0 7 connected by a line 68. Two check valves 69 and 70 are arranged in parallel to the ports A' and B1. Starting at the connecting point 71 a line 72 leads to the port P of the booster pump 65. The pump port or pump outlet P is further connected to tank via a pressure relief valve 75. Line 151 shown in Fig. 4 leads to the brake assembly 30. In case the line 151 is supplied with pressure medium, the brake can be released against the force exerted by the schematically shown spring.

The operation of the design of Fig. 4 should be clear based on the above description to a skilled person. Typically, the pressure increased by the booster pump (a pressure which will be further increased by the main pump 64) is tapped to be used for the release of the brake assembly 30. In the radial piston engine 100 of Fig. 1 to 4 the pressure required to release the brake assembly 30 is taken from the port A and B, respectively, of the engine 100 by means of the switching valve 40. Inasmuch as the switching valve 40 carries out the respective selection, the respective lower pressure existing at port A or at port B is used.

Fig. 5 shows schematically another possibility to provide the pressure medium with a sufficient pressure as it is required for the actuation of the brake assembly 30. The dotted line 77 in Fig. 5 shows that leakage oil exitting from the motor 100 is guided or supplied to the brake chamber 35 of the brake assembly 30 by means of a channel 78. The connecting point 79 of line 77 and line 78 is connected via a line 80 to a pressure relief valve 81 which is adjusted to the brake relief pressure. After a respective presssure build up has taken place in the braking chamber 35, the brake assembly is released.

Fig. 6 is an embodiment of the second aspect of the invention as shown in Fig. 5. Fig. 6 shows a longitudinal sectional view of a radial piston engine 102 which is of similar design as the engine shown in Fig. 1. However. in the embodiment of Fig. 6 the leakage oil flowing out of the area 81 is guided or supplied to the braking chamber 35. This is done by means of a gap 83, 8 initially along the arrow also referred by reference numeral 83 and thereupon along the path referred to ' by the arrow 84. Again, the pressure relief valve 81 connected to the braking chamber 35 serves for the adjustment of the brake release pressure.

Fig. 7 is a longitudinal section of a radial piston engine 103 which differs from the radial piston engine 101 and 102 in sofar as the brake assembly 130 is integrated into the housing hal 2. Again, for this embodiment leakage oil from an area corresponding to the area 82 in Fig. 6 is guided to the braking chamber 135. This occurs along a gap 141. The gap 141 is connected on the one hand side to the brake chamber 135 and on the other side to the area where the leakage oil is generated. This leakage oil has again an increased pressure which can be used for the release of the brake. Arrow 132 refers to the leakage oil flow towards the gap 141.

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Claims

1. A radial piston motor for operation together with a mechanical brake assembly and operated together with a pump assembly comprising a main pump and a booster pump, said radial piston motor comprising: a housing, at least two ports (A. B) formed in said housing for the pressure medium, a shaft rotatably mounted in said housing, a rotor fixedly mounted to said shaft, pistons arranged in radial bores of said rotor, a stationary cam path for cooperation with rollers assigned to said pistons, a commutator (24) fixedly mounted in said housing and adapted to connect/separate said ports (A, B) tolfrom said radial bores depending on the position of said rotor, characterized in that the pressure medium required for the actuation of said brake assembly is derived from said motor housing.

2. The motor of claim 1, wherein the pressure medium is supplied to said brake assembly by channels located in said motor housing.

3. The motor of claim 2. wherein the pressure medium is guided along an annular gap (41) within said commutator (24).

4. The motor of claim 3, wherein the annular gap (41) extends from the rotor to the axial end of said radial piston motor. where the brake assembly is located.

5. The motor of one of the preceeding claims, wherein the pressure medium used for the actuation of the brake is taken via a valve from one port or from the other port (A, B).

6. The motor of claim 5, wherein the pressure medium is taken from the control chambers (25. 26) in the motor housing.

7. The motor of one of the preceeding claims, wherein the pressure medium is the leakage pressure medium and is taken from a location (82 in Fig. 6) radially inwardly with respect to the connecting area between the rotor and the commutator.

8. The motor of one of the preceeding claims, wherein a switching valve (40) is located in the commutator (24) such t hat automatically one port or the other is connected with the brake assembly, said port connected with the brake assembly being preferably the one with the lower pressure.

9. The motor of claim 8, wherein the switching valve (40) is connected on the one hand side to the annular control chambers (25. and 26) and an the other hand to an annular gap (41) formed between the shaft (5) and the inner circumference of the commutator or the housing half (2), wherein the pressure medium is supplied from said annular gap through a radial gap between the housing half (2) and the shaft (5) to the brake chamber (37) of the brake assembly.

10. A radial piston engine in particular for use with a mechanical brake assembly characterized in that the pressure medium used for the actuation of the brake assembly is taken from the radial piston engine and is then supplied to the brake assembly.

11. The engine of claim 10. wherein the supply of the pressure medium to the brake-assembly is controlled by a valve.

12. The engine of claim 11, wherein the valve is built into said radial piston engine.

13. The engine of claim 10. wherein the valve is a switching valve (40) connected with both ports of the engine.

14. The engine of claim 11, wherein the valve is built into the commutator or a housing member.

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15. The engine of one of claims 1 to 14. wherein the valve is connected to the brake asssembly via channel means provided in the housing of the engine.

16. The engine of claim 10, wherein pressure medium provided in the radially inner area of the rotor and commutator is supplied via channel means, in particular via an annular channel between the shaft and the inner side of the commutator to a brake chamber (35) of the brake assembly, and wherein a pressure relief valve is provided for the adjustment of the brake relief pressure for the brake chamber.

17. Radial piston motors as herein described with reference to, and as shown in, the accompanying drawings.

18. Radial piston motors as claimed in claim 1 and as herein described.

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