Hydraulic drive system with protection against incorrect operation

Abstract

The invention relates to a hydraulic drive system (10) having a first, a second and a third fluid line (11; 12) and a hydraulic motor (20), wherein the hydraulic motor (20) has a first and a second working connection (21; 22) and a leakage connection (23), wherein the leakage connection (23) is permanently connected to the third fluid line (13). According to the invention, a valve (30) is provided which has a first and a second switching position (31; 32), wherein in the first switching position (31) the first fluid line (11) is connected via the valve (30) to the first working connection (21), wherein in addition the second fluid line (12) is connected via the valve (30) to the second working connection (22), wherein in the second switching position (32) the first and the second fluid line (11; 12) are connected via the valve (30) to the first and the second working connection (21; 22) in such a way that when the fluid flow is via the first and / or the second fluid line (11;12) activated pressure fluid supply with simultaneously shut-off third fluid line (13) no damage can occur to the hydraulic motor (20), wherein the valve (30) is acted upon by a spring (33) in the direction of an adjustment to the first switching position (31), wherein the valve (30) is hydraulically adjustable in the direction of an adjustment to the second switching position (32) by the pressure at the leakage connection (23);

Description

[0001] The invention relates to a hydraulic drive system according to the preamble of claim 1.

[0002] Mobile work machines, such as agricultural tractors, often have a lifting gear to which interchangeable attachments can be mounted. The attachment can include hydraulic actuators, namely hydraulic cylinders or hydraulic motors. These are often supplied with pressurized fluid via fluid lines, especially hose lines, with the ends of the fluid lines facing away from the actuators each connected to the mobile work machine via a hydraulic quick-release coupling. If a hydraulic motor is used as the actuator, such as the one described in the data sheet "Axial Piston Fixed Motor A2FM / A2FE Series 70" from Bosch Rexroth AG (RD91071 dated October 21, 2022), one fluid line, namely the third fluid line, serves to drain leaks.Since a comparable third fluid line is not required for hydraulic cylinders, it can happen that the operator forgets to connect the third fluid line to the mobile work machine. As a result, pressure can build up in third fluid lines. This is particularly the case when the quick coupling is designed according to US 4 373 551 A, i.e. when a seat valve is arranged in both the coupling part and the mating coupling part, which prevents pressurized fluid from escaping from the associated fluid lines when the quick coupling is not connected. This has the effect of increasing pressure in the interior of the housing of the hydraulic motor, although this interior of the housing is usually essentially pressureless. As a result, for example, the seal on the motor shaft can be overloaded and subsequently must be replaced.

[0003] The object of the invention is to design the hydraulic drive system in such a way that no damage occurs to the hydraulic motor when it is operated with the third fluid line disconnected, or when the pressure fluid supply is activated via the first and / or second fluid line with the third fluid line disconnected. The drive system should be universally usable for all conceivable hydraulic controls within the mobile work machine. This means that it should operate without control intervention by the mobile work machine. Furthermore, no electrical power supply from the mobile work machine should be required.

[0004] According to claim 1, it is proposed that a valve is provided which has a first and a second switching position, wherein in the first switching position the first fluid line is connected via the valve to the first working connection, wherein in addition the second fluid line is connected via the valve to the second working connection, wherein in the second switching position the first and the second fluid line are connected via the valve to the first and the second working connection in such a way that when the pressure fluid supply is activated via the first and / or the second fluid line and the third fluid line is simultaneously blocked off, no damage can occur to the hydraulic motor, wherein the valve is acted upon by a spring in the direction of an adjustment towards the first switching position, wherein the valve is hydraulically adjustable in the direction of an adjustment towards the second switching position by the pressure at the leakage connection.

[0005] It is conceivable that the pressure at the leakage port actuates a pilot valve, which in turn actuates the valve according to the invention, thus providing indirect hydraulic adjustment. However, direct hydraulic adjustment is also conceivable. The valve is preferably designed as a slide valve. It preferably comprises a cartridge valve that is mounted, in particular screwed, in a separate housing.

[0006] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0007] It can be provided that a coupling part of a hydraulic quick-action coupling is arranged at an end of the first, second and / or third fluid line facing away from the hydraulic motor, wherein the coupling part in each case has a seat valve which is open when the coupling part is coupled to a mating coupling part of said quick-action coupling, and closed when said coupling does not exist. In this case in particular, in the event of incorrect operation, i.e. when the third fluid line is not connected during operation, the third fluid line is blocked, which can cause the damage to the hydraulic motor explained above. The quick-action coupling can be designed according to US 4 373 551 A. The mating coupling part is preferably the female coupling part, which is also referred to as a coupling socket, wherein the coupling part is the male coupling part, which is also referred to as a coupling plug.Within the scope of the present invention, however, the reverse assignment can also be used. It should be noted that both coupling parts are usually equipped with the aforementioned seat valve.

[0008] It can be provided that the valve has a locking device that holds the valve in the second switching position against the force of the spring when there is essentially no pressure at the leakage connection, wherein the valve can be switched manually from the second to the first switching position. Without the locking device, the valve could move back and forth between the first and second switching positions as a result of the incorrect operation explained above, because the second switching position causes the pressure in the third fluid line or at the leakage connection to drop. With the proposed locking device, the second switching position remains set once it has been set as a result of incorrect operation. A suitable locking device is known, for example, from DE 26 32 800 A1. There, radially displaceable balls are used which engage in an associated annular groove.The locking mechanism there is designed to support almost any force. Within the scope of the present invention, however, a simpler locking mechanism can also be used, in which the aforementioned balls are preloaded radially by a spring mechanism such that the locking mechanism can only support a limited force, which can be overcome by manual actuation of the valve. When applying the locking mechanism according to DE 26 32 800 A1 to the present invention, a manually operated hydraulic valve is preferably used for manual actuation, which unlocks the locking mechanism.

[0009] It can be provided that, in the second switching position, the first and second fluid lines are blocked by the valve, with the first and second working ports being connected to each other by the valve. This valve design is suitable if the hydraulic motor is to run down slowly after briefly starting up after the above-mentioned incorrect operation.

[0010] It can be provided that in the second switching position, the first and second fluid lines are blocked by the valve, whereby the first and second working ports are blocked by the valve. This valve design is considered if the hydraulic motor is to stop abruptly after having started briefly following the above-mentioned incorrect operation. Furthermore, please refer to the explanations regarding Fig. 2.

[0011] It can be provided that in the second switching position, the second fluid line and the first and second working connections are connected to each other by the valve, wherein the first fluid line is blocked by the valve. This design of the valve is considered when a high pressure is permanently assigned to the first fluid line, wherein a low pressure is permanently assigned to the second fluid line, wherein the hydraulic motor is to run down slowly after having started briefly after the above-mentioned incorrect operation. Furthermore, reference is made to the explanations regarding Fig. 3.

[0012] It can be provided that, in the second switching position, the first and second fluid lines and the first and second working ports are connected to each other by the valve. This valve design is suitable if, after the incorrect operation described above, the pressure in the third fluid line or at the leakage port is to drop quickly, with the hydraulic motor being allowed to decelerate slowly after briefly starting up.

[0013] The valve may be provided with an indicator that shows whether the valve is in the second switching position. Preferably, the indicator comprises a color marking, which is particularly red. This indicator is intended to clearly indicate to the user that the incorrect operation has occurred, allowing them to quickly correct the problem.

[0014] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0015] The invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 shows a hydraulic circuit diagram of a hydraulic drive system according to the invention, which is mounted on a mobile work machine; Fig. 2 a circuit symbol of a second embodiment of the valve; Fig. 3 a circuit symbol of a third embodiment of the valve; and Fig. 4 a circuit symbol of a fourth embodiment of the valve.

[0016] Fig. 1 shows a hydraulic circuit diagram of a hydraulic drive system 10 according to the invention, which is mounted on a mobile work machine 50. The mobile work machine 50 can be, for example, an agricultural tractor 50, which comprises a lifting gear at the rear or at the front, which is intended to accommodate an interchangeable attachment 51. The present attachment 51 comprises the hydraulic drive system 10 according to the invention, which in turn comprises a hydraulic motor 20. The hydraulic motor 20 can be designed, for example, according to the data sheet "Axial Piston Constant Displacement Motor A2FM / A2FE Series 70" from Bosch Rexroth AG (RD91071 dated October 21, 2022). This is an axial piston motor in a bent-axis design with a constant displacement volume. The hydraulic motor 20 has a first and a second working connection 21, 22, via which the pressure fluid for driving the hydraulic motor 20 is supplied or discharged.The pressurized fluid is preferably a liquid, in particular hydraulic oil. The leaks occurring inside the hydraulic motor 20 are diverted to the mobile work machine 50 via the leakage port 23, where they are collected in a tank. These internal leaks accumulate in the interior of the hydraulic motor housing, regardless of where they occur, with the leakage port being arranged on the housing in such a way that the leaks can flow out of the interior.

[0017] The hydraulic machine 20 is connected to the hydraulic system of the mobile work machine 50 via a first, a second, and a third fluid line 11; 12; 13, so that it can be supplied with pressurized fluid from there. The corresponding connection is designed with a quick-coupling device 40, so that the attachment 51 can be changed quickly and easily. Each of the three quick-coupling devices 40 can be designed, for example, according to US Pat. No. 4,373,551 A, the entire scope of which is incorporated by reference and made part of the present application. Each fluid line 11; 12; 13 is provided at the end facing away from the hydraulic motor 20 with a coupling part 41, which can be inserted into an associated mating coupling part 42 on the mobile work machine 50 and locked there. The coupling part 41 and the mating coupling part 42 each comprise a seat valve. This seat valve is open when the coupling part is coupled to the mating coupling part.Furthermore, both seat valves are closed. This is intended to ensure that no pressurized fluid can escape from the hydraulic drive system 10 when the attachment is not mounted on the mobile work machine 50 or when the quick-release couplings are not connected.

[0018] The coupling part 41 is preferably designed as a male coupling plug, with the mating coupling part being designed as a female coupling socket. The reverse arrangement is also possible. Directly adjacent to the coupling part 41, the three fluid lines 11; 12; 13 are preferably each designed as a flexible hose, although they may also be designed as rigid pipes further down, with sections extending within a solid valve block. The valve 30 according to the invention can be mounted directly on the hydraulic motor 20, and it can also be connected to it via rigid pipes or flexible hoses.

[0019] When attaching the attachment 51 to the mobile work machine 50, it may happen that the operator forgets to connect the third fluid line 13 to the mobile work machine 50 because this is not present in typical attachments that exclusively comprise hydraulic cylinders. If the hydraulic motor 20 is then operated solely using the first and second fluid lines 11; 12 with a conventional hydraulic drive system, the aforementioned leaks accumulate inside the hydraulic motor until it is completely filled with pressurized fluid. Subsequently, the pressure in the normally largely pressure-free interior of the hydraulic motor 20 increases. As a result, the pressure may become so high that, for example, the seal on the shaft of the hydraulic motor 20 is damaged. The present invention is intended to prevent such damage caused by the aforementioned incorrect operation.

[0020] For this purpose, the valve 30 is connected between the first and second fluid lines 11; 12 and the first and second working connections 21; 22. The valve 30 has a first and a second switching position 31; 32, and is preferably designed as a slide valve. In the direction of adjustment towards the first switching position, it is preferably acted upon by a preloaded spring 33, so that the first switching position 31 is normally set. In the first switching position 31, the first fluid line 11 is connected exclusively to the first working connection 21, and the second fluid line 12 is connected exclusively to the second working connection 22. In the first switching position 31, the hydraulic drive system 10 therefore behaves like a known hydraulic drive system in which the valve 30 is not provided.

[0021] In the second switching position 32 of the valve 30, the first and second fluid lines 11; 12 are blocked, with the first and second working ports 21; 22 connected to one another. The first and second fluid lines 11; 12 can be pressurized in the second switching position 32 without fear of damage to the hydraulic motor 20 if the third fluid line 13 is not connected. The operator immediately notices that something is wrong because the hydraulic motor 20 does not rotate as expected or comes to a standstill after an initial rotational movement.

[0022] The switching from the first to the second switching position is effected by the pressure at the leakage port 23. This directly acts on the valve 30 in the direction of adjustment to the second switching position 30. It should be noted that instead of the direct hydraulic adjustment shown, a pilot control can also be provided. The pressure at the leakage port 23 then adjusts a pilot valve, which in turn hydraulically adjusts the valve 30. In both cases, the adjustment, in particular the preload of the spring 33 during direct hydraulic actuation, is designed such that the low pressure usually present at the leakage port 23 is not sufficient to bring about an adjustment from the first to the second switching position 31; 32.

[0023] The valve 30 is preferably equipped with a locking device 34, which ensures that the second switching position 32 remains set, even if the pressure at the leakage connection 23 drops again after switching from the first to the second switching position 31; 32. It should be noted that the Fig. The first embodiment of the valve 30 shown in Figure 1 causes the pressure at the leakage port 23 to drop again due to unavoidable leaks when the second switching position 32 is set. The locking device gives the user time to detect the malfunction and correct it by connecting the third fluid line to the mobile work machine 50. The locking device 34 is preferably manually overridable, so that the user can manually switch the valve 30 from the second to the first switching position 32; 31 in order to be able to use the attachment 51 normally again.

[0024] Fig. 2 shows a circuit symbol of a second embodiment of the valve 30'. The second embodiment of the valve 30' replaces the first embodiment according to Fig. 1, whereby the actuation of the valves 30'; 30 remains unchanged. Except for the differences explained below, the second embodiment is identical to the first embodiment, so that in this regard, reference is made to the explanations for Fig. 1 is referred to.

[0025] In the second embodiment of the valve 30', the first and second working ports 21; 22 of the hydraulic motor (No. 20 in Fig. 1) is blocked when the valve 30' is in the second switching position 32. As a result, the hydraulic motor is hydraulically clamped so that it can no longer rotate. In the first embodiment, however, the hydraulic motor can rotate freely with little resistance in the second switching position. In the second embodiment, the attachment comes to an abrupt stop when the second switching position 32 is set, whereas in the first embodiment, a started rotational movement slowly comes to an end. Which of the two variants is to be preferred depends on the type of attachment (No. 51 in Fig. 1) off.

[0026] Fig. 3 shows a circuit symbol of a third embodiment of the valve 30". The third embodiment of the valve 30" replaces the first embodiment according to Fig. 1, whereby the actuation of the valves 30"; 30 remains unchanged. Except for the differences explained below, the third embodiment is identical to the first embodiment, so that in this regard, reference is made to the explanations for Fig. 1 is referred to.

[0027] The third embodiment of the valve 30" is intended for applications in which it is specified that the first fluid line 11 carries high pressure, while the second fluid line 12 carries low pressure or is connected to a tank. As a result, the direction of rotation of the hydraulic motor (No. 20 in Fig. 1) is fixed. In the second position 32, the first and second working ports 21; 22 are therefore connected to the low-pressure second fluid line 12, while the high-pressure first fluid line 11 is blocked. As a result, the pressure in the hydraulic motor (No. 20 in Fig. 1) The excess pressure resulting from the described operating error dissipates more quickly when the second switching position 32 is set, because the aforementioned internal leaks can flow to the tank in the mobile work machine. In the first and second embodiments, however, no fixed assignment of high and low pressure to the first and second fluid lines, respectively, is necessary.

[0028] Fig. 4 shows a circuit symbol of a fourth embodiment of the valve 30'''. The fourth embodiment of the valve 30''' replaces the first embodiment according to Fig. 1, whereby the actuation of the valves 30'''; 30 remains unchanged. Except for the differences explained below, the fourth embodiment is identical to the first embodiment, so that in this regard, reference is made to the explanations for Fig. 1 is referred to.

[0029] In the fourth embodiment of the valve 30''', the first and second fluid lines 11; 12 and the first and second working ports 21; 22 are connected to each other in the second switching position 32. As a result, no pressure can build up in the fluid lines 11; 12 because there is a hydraulic short circuit between the high and low pressure sides. Inside the hydraulic motor (No. 20 in Fig. 1) pressure cannot build up. The hydraulic motor (No. 20 in Fig. 1) can rotate freely with little resistance.

[0030] It is understood that, depending on the application, further connections in the second switching position 32 are possible. Reference symbol 10 hydraulic drive system 11 first fluid line 12 second fluid line 13 third fluid line 20 hydraulic motor 21 first working connection 22 second working connection 23 Leakage connection 30 Valve (first embodiment) 30' valve (second embodiment) 30" valve (third version) 30''' valve (fourth embodiment) 31 first switching position 32 second switching position 33 spring 34 locking device 35 Pressurization towards the second switching position 40 quick coupling 41 Coupling part 42 Counter coupling part 50 mobile work machines 51 attachment QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 4 373 551 A [0002, 0007, 0017] DE 26 32 800 A1

[0008]

Claims

[1] Hydraulic drive system (10) with a first, a second and a third fluid line (11; 12; 13) and a hydraulic motor (20), wherein the hydraulic motor (20) has a first and a second working connection (21; 22) and a leakage connection (23), wherein the leakage connection (23) is permanently connected to the third fluid line (13), characterized bythat a valve (30; 30'; 30''; 30''') is provided, which has a first and a second switching position (31; 32), wherein in the first switching position (31) the first fluid line (11) is connected via the valve (30; 30'; 30''; 30''') to the first working connection (21), wherein in addition the second fluid line (12) is connected via the valve (30; 30'; 30''; 30''') to the second working connection (22), wherein in the second switching position (32) the first and the second fluid line (11; 12) are connected via the valve (30; 30'; 30''; 30''') to the first and the second working connection (21; 22) in such a way that when the pressure fluid supply is activated via the first and / or the second fluid line (11; 12) and simultaneously blocked third fluid line (13) no damage can occur to the hydraulic motor (20), wherein the valve (30; 30'; 30''; 30''') is acted upon by a spring (33) in the direction of an adjustment to the first switching position (31), wherein the valve (30; 30';30''; 30''') is hydraulically adjustable in the direction of adjustment to the second switching position (32) by the pressure at the leakage connection (23). [2] Hydraulic drive system (10) according to claim 1, wherein a coupling part (41) of a hydraulic quick coupling (40) is arranged at an end of the first, the second and / or the third fluid line facing away from the hydraulic motor (10), wherein the coupling part (41) in each case has a seat valve which is open when the coupling part (41) is coupled to a counter-coupling part (42) of said quick coupling (40), wherein it is closed when said coupling does not exist. [3] Hydraulic drive system (10) according to one of the preceding claims, wherein the valve (30; 30'; 30''; 30''') has a locking device (34) which holds the valve in the second switching position (32) against the force of the (33) spring when there is substantially no pressure at the leakage connection (23), wherein the valve (30; 30'; 30''; 30''') is manually switchable from the second (32) to the first switching position (31). [4] Hydraulic drive system (10) according to one of the preceding claims, wherein in the second switching position (32) the first and the second fluid line (11; 12) are blocked by the valve (30), wherein the first and the second working connection are connected to one another by the valve (30). [5] Hydraulic drive system (10) according to one of claims 1 to 3, wherein in the second switching position (32) the first and the second fluid line (11; 12) are blocked by the valve (30'), wherein the first and the second working connection (21; 22) are blocked by the valve (30'). [6] Hydraulic drive system (10) according to one of claims 1 to 3, wherein in the second switching position (32) the second fluid line (12) and the first and second working ports (21; 22) are connected to one another by the valve (30''), wherein the first fluid line (11) is blocked by the valve (30''). [7] Hydraulic drive system (10) according to one of claims 1 to 3, wherein in the second switching position (32) the first and second fluid lines (11; 12) and the first and second working ports (21; 22) are connected to one another by the valve (30'''). [8] Hydraulic drive system (10) according to one of the preceding claims, wherein the valve (30; 30'; 30''; 30''') has an indicator that indicates whether the valve is in the second switching position (32).

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