Closed hydraulic system and operation instrument

Abstract

The utility model belongs to the technical field of operation machinery and provides a closed hydraulic system and an operation instrument, the closed hydraulic system comprises a closed hydraulic loop, an oil recharging unit, a DA control unit and a switching unit, the closed hydraulic loop comprises a variable pump, the displacement of the variable pump is controlled through a pump control oil way, the oil recharging oil way is used for recharging oil to the closed hydraulic loop, and the switching unit is used for switching the oil recharging oil way to the closed hydraulic loop. The DA control unit is arranged on the oil supplementing oil way and provided with a DA output oil port and a throttling oil supplementing port, the throttling oil supplementing port is hydraulically connected to the closed hydraulic loop, and the switching unit is used for controlling the pump control oil way to select hydraulic oil of the oil supplementing oil way or the DA output oil port as control input oil. The switching unit is arranged to control the DA control unit to be switched between the working state and the failure state, and the closed hydraulic system can have the flameout prevention function and the low-speed operation function.

Description

Technical Field

[0001] The utility model belongs to the technical field of working equipment, and in particular relates to a closed hydraulic system and a working equipment. Background Art

[0002] Closed hydraulic systems have been used in many work equipment, such as skid steer loaders, aerial work platforms, etc. Taking skid steer loaders as an example, skid steer loaders are generally driven by closed hydraulic systems, and the travel drive pump in the hydraulic system is generally driven by the engine. During the operation of the skid steer loader, the engine speed will decrease due to the impact of shoveling resistance. At this time, if the travel drive pump is still running at a large displacement, it is likely to cause the engine to stall.

[0003] In order to avoid engine stalling, the prior art generally sets a DA valve. When the engine slows down, the oil pressure output by the DA valve to the flow control oil circuit will decrease, so that the displacement of the travel drive pump will be adaptively reduced, thereby achieving the purpose of matching the engine operating condition with the displacement of the travel drive pump.

[0004] However, when the skid loader is traveling at a low speed, the engine will also run at a low speed. At this time, if the DA valve works normally, the displacement of the travel drive pump will be very small, and the whole machine may easily fail to move or move slowly. Utility Model Content

[0005] In view of the above-mentioned defects or shortcomings, the utility model provides a closed hydraulic system and an operating device, aiming to solve the technical problem that the engine anti-stall function and the low-speed operation function of the existing closed hydraulic system are in conflict.

[0006] To achieve the above-mentioned purpose, the utility model provides a closed hydraulic system, including a closed hydraulic circuit, an oil replenishment unit, a DA control unit and a switching unit. The closed hydraulic circuit includes a variable pump. The displacement of the variable pump is controlled by a pump control oil circuit. The oil replenishment oil circuit is used to replenish oil to the closed hydraulic circuit. The DA control unit is arranged on the oil replenishment oil circuit and has a DA output oil port and a throttling oil replenishment port. The throttling oil replenishment port is hydraulically connected to the closed hydraulic circuit. The switching unit is used to control the pump control oil circuit to select the hydraulic oil in the oil replenishment oil circuit or the DA output oil port as the control input oil.

[0007] In an embodiment of the utility model, the switching unit includes a first selection oil circuit, a second selection oil circuit and a first reversing valve. One end of the first selection oil circuit and the second selection oil circuit are hydraulically connected to the oil replenishing circuit and the DA output oil port respectively. The other end of the first selection oil circuit and the second selection oil circuit are connected to the pump control oil circuit through the first reversing valve. The first reversing valve is used to selectively control at least one of the first selection oil circuit and the second selection oil circuit to conduct the pump control oil circuit.

[0008] In an embodiment of the utility model, the first reversing valve is a two-position three-way valve and has a first valve position and a second valve position. In the first valve position, the first selection oil circuit is connected to the pump control oil circuit and the second selection oil circuit is cut off. In the second valve position, the second selection oil circuit is connected to the pump control oil circuit and the first selection oil circuit is cut off.

[0009] In an embodiment of the utility model, the switching unit includes a first selection oil circuit, a second selection oil circuit and a second reversing valve. One end of the first selection oil circuit is hydraulically connected to the oil replenishing circuit, and the other end is connected to the pump control oil circuit through the second reversing valve. The second selection oil circuit is connected between the DA output oil port and the pump control oil circuit. The second reversing valve is used to control the conduction or cutoff of the first selection oil circuit and the pump control oil circuit.

[0010] In an embodiment of the utility model, the second reversing valve is a two-position two-way valve having an on valve position and a shut-off valve position.

[0011] In an embodiment of the utility model, a one-way valve is provided on the second selection oil circuit, and the one-way valve is configured to be conductive when the hydraulic oil flows to the pump control oil circuit and to be blocked in the reverse direction.

[0012] In an embodiment of the present invention, the DA control unit is a DA valve.

[0013] In an embodiment of the utility model, the variable pump is a swash plate piston pump, the pilot oil port of the swash plate piston pump is hydraulically connected to the pump control oil circuit, and the pump control oil circuit is used to control the inclination angle of the swash plate in the swash plate piston pump according to the size of the input oil pressure.

[0014] In an embodiment of the utility model, the closed hydraulic circuit further includes a travel motor, the oil outlet of the travel motor is connected to the oil inlet of the variable pump, and the oil outlet of the variable pump is connected to the oil inlet of the travel motor.

[0015] In order to achieve the above-mentioned purpose, the utility model also provides a working device, wherein the working device includes the closed hydraulic system according to the above-mentioned, and the working device also includes an engine, and the engine can be connected to the variable pump by transmission.

[0016] Through the above technical solution, the closed hydraulic system provided by the embodiment of the utility model has the following beneficial effects:

[0017] The closed hydraulic system in the utility model controls the DA control unit to switch between the working state and the failure state by setting a switching unit, so that the working equipment with the closed hydraulic system can have the anti-stall function and the low-speed working function.

[0018] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide an understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation to the present invention. In the accompanying drawings:

[0020] Figure 1 It is a connection diagram of a first embodiment of a closed hydraulic system in an embodiment of the utility model;

[0021] Figure 2 It is a connection diagram of a second embodiment of the closed hydraulic system in the embodiment of the utility model;

[0022] Figure 3 It is a schematic diagram of the structure of a DA valve according to an embodiment of the utility model.

[0023] Description of Reference Numerals

[0024] 11. Variable pump; 12. Travel motor; 13. Pump control oil circuit; 21. Oil replenishment oil circuit; 22. Oil replenishment pump; 3. DA control unit; 31. DA valve; 311. DA output oil port; 312. Throttling oil replenishment port; 313. Detection access port; 4. Switching unit; 41. First selection oil circuit; 42. Second selection oil circuit; 43. First reversing valve; 44. Second reversing valve. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0026] The closed hydraulic system of the present utility model is described below with reference to the accompanying drawings.

[0027] A closed hydraulic system refers to a hydraulic system that consists of a variable pump 11 and a drive motor forming a closed hydraulic circuit. In the closed hydraulic circuit, the oil outlet of the drive pump is directly connected to the oil inlet of the motor, and the oil outlet of the motor is directly connected to the oil inlet of the drive pump. Closed hydraulic systems are used in many working equipment, such as skid loaders, aerial work platforms, tractors, etc. Closed hydraulic systems can be used to drive equipment to travel and work.

[0028] DA control is a control method related to the engine speed. When the engine speed changes, the control oil pressure sent by the DA valve to the drive pump will also change, thereby changing the displacement of the hydraulic pump.

[0029] In order to solve the technical problem that the engine flameout prevention function and the low-speed operation function of the existing closed hydraulic system are in conflict, the utility model provides a closed hydraulic system, such as Figure 1 and Figure 2As shown, the closed hydraulic system in the utility model includes:

[0030] A closed hydraulic circuit includes a variable pump 11 and an actuator. The displacement of the variable pump 11 is controlled by a pump control oil circuit 13. The actuator can be a cylinder, a motor, etc. For example, when the actuator is a motor, the closed hydraulic circuit can be used to drive the equipment to move, or when the actuator is a cylinder, the closed hydraulic circuit can be used to drive the equipment to operate;

[0031] The oil replenishment circuit 21 is used to replenish oil to the closed hydraulic circuit;

[0032] A DA control unit 3, which is disposed on the oil replenishment circuit 21 and has a DA output oil port 311 and a throttle oil replenishment port 312, and the throttle oil replenishment port 312 is hydraulically connected to the closed hydraulic circuit; and

[0033] The switching unit 4 is used to control the pump control oil circuit 13 to select the hydraulic oil in the oil replenishment oil circuit 21 or the DA output oil port 311 as the control input oil.

[0034] Furthermore, if Figure 3 As shown, the DA control unit 3 has a detection access port 313, a throttling oil replenishing port 312 and a DA output oil port 311. The detection access port 313 is used to receive the hydraulic oil from the oil replenishing circuit 21, and throttle a part of the hydraulic oil and then lead it out from the throttling oil replenishing port 312 and output it to the closed hydraulic circuit. The oil pressure of the DA output oil port 311 is positively correlated with the oil pressure difference between the detection access port 313 and the throttling oil replenishing port 312.

[0035] When the switching unit 4 controls the hydraulic oil of the DA output oil port 311 to flow to the pump control oil circuit 13, if the engine speed decreases due to the increase in load, the closed hydraulic system will be manifested in that the resistance of the actuator increases and the oil pressure of the closed hydraulic circuit increases. The increase in the oil pressure of the closed hydraulic circuit will cause the oil pressure difference between the detection access port 313 and the throttle oil replenishment port 312 to decrease, that is, the oil pressure from the DA output oil port 311 to the pump control oil circuit 13 decreases, and the variable pump 11 will operate with reduced displacement, so that the displacement of the variable pump 11 matches the working condition of the engine, avoiding the situation where the engine is overloaded and stalled.

[0036] When the switching unit 4 controls the hydraulic oil in the oil replenishment circuit 21 to flow to the pump control circuit 13, the DA control unit 3 is in a failed state, and the DA output oil port 311 will not affect the pressure of the pump control circuit 13. The oil pressure of the pump control circuit 13 is always equal to that of the oil supply circuit, and the variable pump 11 operates at a fixed displacement. In this mode, the equipment can be ensured to operate or travel at a low speed even when the engine is running at a low speed, thereby achieving a fuel-saving effect.

[0037] In summary, the closed hydraulic system in the present invention controls the DA control unit 3 to switch between the working state and the failure state by setting the switching unit 4, so that the working equipment with the closed hydraulic system can have the anti-stall function and the low-speed operation function.

[0038] In an embodiment of the utility model, the switching unit 4 controls the pump-controlled oil circuit 13 to select the hydraulic oil in the oil replenishing circuit 21 or the DA output oil port 311 as the control input oil, which may include controlling one of the hydraulic oil in the oil replenishing circuit 21 or the DA output oil port 311 to flow to the pump-controlled oil circuit 13, or may also include controlling the hydraulic oil in the oil replenishing circuit 21 and the DA output oil port 311 to flow to the pump-controlled oil circuit 13 at the same time. In this state, since the oil pressure in the oil replenishing circuit 21 is greater than the oil pressure in the DA output oil port 311, the DA output oil port 311 will not affect the pressure of the pump-controlled oil circuit 13. In essence, the DA control unit 3 is in a failed state, and the control input oil of the pump-controlled oil circuit 13 only comes from the oil replenishing circuit 21.

[0039] There are many specific configuration methods for the switching unit 4, such as Figure 1 and Figure 3 As shown, the utility model provides an embodiment, in which the switching unit 4 may include a first selection oil circuit 41, a second selection oil circuit 42 and a first reversing valve 43, one end of the first selection oil circuit 41 and the second selection oil circuit 42 are respectively hydraulically connected to the oil replenishment oil circuit 21 and the DA output oil port 311, and the other end of the first selection oil circuit 41 and the second selection oil circuit 42 is connected to the pump control oil circuit 13 through the first reversing valve 43, and the first reversing valve 43 is used to control at least one of the first selection oil circuit 41 and the second selection oil circuit 42 to be connected to the pump control oil circuit 13. At least one of the first selection oil circuit 41 and the second selection oil circuit 42 is connected to the pump control oil circuit 13, or it also includes that both the first selection oil circuit 41 and the second selection oil circuit 42 are connected to the pump control oil circuit 13. By controlling the first reversing valve 43 to switch, at least one of the first selection oil circuit 41 and the second selection oil circuit 42 can be connected to the pump control oil circuit 13, so that the DA control unit 3 can be switched between the failure state and the normal working state.

[0040] Furthermore, if Figure 1 As shown, the first reversing valve 43 may be a two-position three-way valve having a first valve position and a second valve position, and the first valve position may be configured to connect the first selection oil circuit 41 with the pump control oil circuit 13 and cut off the second selection oil circuit 42, or the first valve position may be configured to connect the first selection oil circuit 41 and the second selection oil circuit 42 with the pump control oil circuit 13. The second valve position may be configured to connect the second selection oil circuit 42 with the pump control oil circuit 13 and cut off the first selection oil circuit 41. Of course, the first reversing valve 43 may also be other types of reversing valves.

[0041] The utility model also provides another embodiment, such as Figure 2 and Figure 3 As shown, in this embodiment, the switching unit 4 includes a first selection oil circuit 41, a second selection oil circuit 42 and a second reversing valve 44. One end of the first selection oil circuit 41 is hydraulically connected to the oil replenishment oil circuit 21, and the other end is connected to the pump control oil circuit 13 through the second reversing valve 44. The second selection oil circuit 42 is connected between the DA output oil port 311 and the pump control oil circuit 13. The second reversing valve 44 is used to control the first selection oil circuit 41 to be connected or cut off with the pump control oil circuit 13. In this connection mode, the DA control unit 3 can be switched between the failure state and the normal working state only by controlling the first selection oil circuit 41 to be connected or cut off with the pump control oil circuit 13.

[0042] like Figure 2 As shown, in this embodiment, the second reversing valve 44 can be a two-position two-way valve having an on valve position and a off valve position. Alternatively, the second reversing valve 44 can also be a reversing valve of other types with on and off functions.

[0043] like Figure 2 As shown, in this embodiment, a one-way valve is provided on the second selection oil circuit 42, and the one-way valve is configured to be open when the hydraulic oil flows to the pump control oil circuit 13 and closed in the reverse direction. By providing a one-way valve, the hydraulic oil in the first selection oil circuit 41 can be prevented from flowing back to the DA output oil port 311 through the second selection oil circuit 42.

[0044] The utility model also provides another embodiment, in which the switching unit 4 includes a first selection oil circuit 41 and a second selection oil circuit 42, the first selection oil circuit 41 is connected between the oil replenishment oil circuit 21 and the pump control oil circuit 13, and the second selection oil circuit 42 is connected between the DA output oil port 311 and the pump control oil circuit 13, and the on-off of the first selection oil circuit 41 and the second selection oil circuit 42 can be controlled by two reversing valves respectively. By controlling the on-off of the first selection oil circuit 41 and the second selection oil circuit 42, the DA control unit 3 can also be switched between the failure state and the normal working state.

[0045] like Figure 1 and Figure 3 As shown, in the embodiment of the present utility model, the DA control unit 3 may be a DA valve 31 .

[0046] like Figure 1 and Figure 2 As shown, in an embodiment of the present utility model, the closed hydraulic system may further include an oil replenishment pump 22, and the oil replenishment pump 22 is used to supply oil to the oil replenishment oil circuit 21, and the oil replenishment pump 22 may be directly connected to the engine transmission.

[0047] In the embodiment of the utility model, the variable pump 11 can be a swash plate piston pump, the pilot oil port of the swash plate piston pump is hydraulically connected to the pump control oil circuit 13, and the pump control oil circuit 13 is used to control the inclination angle of the swash plate in the swash plate piston pump according to the oil pressure of the control input oil, so as to achieve displacement adjustment of the variable pump 11. Of course, the variable pump 11 can also be in other forms.

[0048] like Figure 1 and Figure 2 As shown, in an embodiment of the utility model, when a closed hydraulic circuit is used to drive the equipment to move, the number of closed hydraulic circuits can be two groups, and each group of closed hydraulic circuits can include a travel motor 12, the oil outlet of the travel motor 12 is connected to the oil inlet of the variable pump 11, and the oil outlet of the variable pump 11 is connected to the oil inlet of the travel motor 12.

[0049] In the embodiment of the utility model, the closed hydraulic circuit can also be applied to the lifting drive of the aerial work platform.

[0050] To achieve the above-mentioned purpose, the utility model also provides a working device, wherein the working device includes the closed hydraulic system described above. Since the working device adopts all the technical solutions of the above-mentioned embodiments, it at least has the beneficial effects brought by the above-mentioned embodiments, which will not be repeated here.

[0051] In an embodiment of the present utility model, the working device further comprises an engine, and the engine can be transmission-connected to the variable displacement pump 11 .

[0052] In the embodiments of the present invention, the working machine may be a skid loader, an aerial work platform, a tractor or other equipment.

[0053] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0054] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0056] Although the embodiments of the present invention have been described above, it is understandable that the above embodiments are exemplary and cannot be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A closed hydraulic system, characterized in that: The closed hydraulic system comprises: A closed hydraulic circuit comprises a variable displacement pump (11), wherein the displacement of the variable displacement pump (11) is controlled by a pump control oil circuit (13); An oil replenishment circuit (21) for replenishing oil to the closed hydraulic circuit; A DA control unit (3), which is arranged on the oil replenishment circuit (21) and has a DA output oil port (311) and a throttle oil replenishment port (312), wherein the throttle oil replenishment port (312) is hydraulically connected to the closed hydraulic circuit; and The switching unit (4) is used to control the pump control oil circuit (13) to select the hydraulic oil in the oil replenishment oil circuit (21) or the DA output oil port (311) as the control input oil.

2. The closed hydraulic system according to claim 1, characterized in that: The switching unit (4) comprises a first selection oil circuit (41), a second selection oil circuit (42) and a first reversing valve (43); one end of the first selection oil circuit (41) and the second selection oil circuit (42) are hydraulically connected to the oil replenishment oil circuit (21) and the DA output oil port (311) respectively; the other end of the first selection oil circuit (41) and the second selection oil circuit (42) are connected to the pump control oil circuit (13) through the first reversing valve (43); the first reversing valve (43) is used to selectively control at least one of the first selection oil circuit (41) and the second selection oil circuit (42) to conduct to the pump control oil circuit (13).

3. The closed hydraulic system according to claim 2, characterized in that: The first reversing valve (43) is a two-position three-way valve and has a first valve position and a second valve position. In the first valve position, the first selection oil circuit (41) is connected to the pump control oil circuit (13) and the second selection oil circuit (42) is blocked. In the second valve position, the second selection oil circuit (42) is connected to the pump control oil circuit (13) and the first selection oil circuit (41) is blocked.

4. The closed hydraulic system according to claim 1, characterized in that: The switching unit (4) comprises a first selection oil circuit (41), a second selection oil circuit (42) and a second reversing valve (44); one end of the first selection oil circuit (41) is hydraulically connected to the oil replenishment oil circuit (21), and the other end is connected to the pump control oil circuit (13) through the second reversing valve (44); the second selection oil circuit (42) is connected between the DA output oil port (311) and the pump control oil circuit (13); the second reversing valve (44) is used to control the first selection oil circuit (41) and the pump control oil circuit (13) to be connected or cut off.

5. The closed hydraulic system according to claim 4, characterized in that: The second reversing valve (44) is a two-position, two-way valve having an on valve position and a shutoff valve position.

6. The closed hydraulic system according to claim 4, characterized in that: The second selection oil circuit (42) is provided with a one-way valve, and the one-way valve is configured to be conductive when the hydraulic oil flows toward the pump control oil circuit (13) and to be blocked in the reverse direction.

7. The closed hydraulic system according to any one of claims 1 to 6, characterized in that: The DA control unit (3) is a DA valve (31).

8. The closed hydraulic system according to any one of claims 1 to 6, characterized in that: The variable pump (11) is a swash plate piston pump, the pilot oil port of which is hydraulically connected to the pump control oil circuit (13), and the pump control oil circuit (13) is used to control the inclination angle of the swash plate in the swash plate piston pump according to the magnitude of the input oil pressure.

9. The closed hydraulic system according to any one of claims 1 to 6, characterized in that: The closed hydraulic circuit also includes a travel motor (12), the oil outlet of the travel motor (12) is connected to the oil inlet of the variable pump (11), and the oil outlet of the variable pump (11) is connected to the oil inlet of the travel motor (12).

10. A working machine, characterized in that: The working tool comprises a closed hydraulic system according to any one of claims 1 to 9, and the working tool comprises an engine, which is transmission-connected to the variable displacement pump (11).

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