Hydraulic pump for a hydraulic system of a civil aircraft and method for controlling the same

Abstract

This invention relates to a hydraulic pump and its control method for a hydraulic system in a civil aircraft. The hydraulic pump for the civil aircraft hydraulic system includes a temperature switch, an unloading valve, and a shut-off valve. The temperature switch is located at the pressure outlet of the hydraulic pump. The unloading valve is connected to both the temperature switch and the shut-off valve to cause the shut-off valve to pop up or retract depending on the state of the temperature switch. The shut-off valve is also located at the pressure outlet of the hydraulic pump. When the hydraulic oil temperature in the hydraulic system is within the normal operating temperature range, the temperature switch is open, thus the unloading valve does not operate, the shut-off valve is retracted, and the hydraulic pump operates normally. When the hydraulic oil temperature in the hydraulic system is higher than a first temperature threshold, the temperature switch is closed, thus the unloading valve operates, the shut-off valve pops up, and the hydraulic pump power decreases. When the hydraulic oil temperature in the hydraulic system is lower than a second temperature threshold, the temperature switch is open, thus the unloading valve does not operate, the shut-off valve retracts, and the hydraulic pump operates normally.

Description

Technical Field

[0001] This invention relates to the field of hydraulic systems for aircraft, and more particularly to hydraulic pumps and control methods for use in hydraulic systems of civil aircraft. Background Technology

[0002] Hydraulic pumps used in civil aircraft hydraulic systems are mainly divided into two types: electrically driven and mechanically driven. Mechanically driven hydraulic pumps rely on the engine to provide mechanical energy input. When the hydraulic system reaches high temperatures, the continuous power input from the engine can cause the hydraulic system temperature to become uncontrollable and continue to rise until the temperature reaches the point where the hydraulic system's fire shut-off valve activates, cutting off the hydraulic pump's oil suction circuit. This causes internal damage to the hydraulic pump, leading to hydraulic system failure and resulting in significant economic losses and safety hazards.

[0003] To address the aforementioned issues, civil aircraft currently commonly employ a shut-off valve added to the hydraulic pump body, utilizing a manual shut-off function. This allows for manual shutdown when the hydraulic system reaches high temperatures, cutting off the hydraulic pump's hydraulic energy output to the load, thereby reducing the hydraulic system temperature and protecting the hydraulic pump body from damage.

[0004] However, existing technologies still have the following shortcomings: The flight process requires additional operational steps, and pilots must use high-temperature alarm information to determine whether the hydraulic pump needs to be manually shut down. Manually shutting off the hydraulic pump will directly result in no pressure output from the hydraulic system. When the temperature returns to the normal operating temperature of the hydraulic system, the hydraulic pump will not be able to restart automatically. The reliance on manual operation and the lack of automated control over the hydraulic pump's opening and closing hinders the aircraft's automatic control. Summary of the Invention

[0005] One objective of this invention is to provide a hydraulic pump and its control method for a hydraulic system of civil aircraft, which overcomes the shortcomings of the prior art and enables temperature adaptive control of the hydraulic pump. The temperature adaptive control process does not require additional operation by the pilot, avoids the problem that the hydraulic pump cannot be automatically restarted after the temperature returns to normal after being shut down due to high temperature, and enhances the reliability and advanced nature of the hydraulic pump.

[0006] The above-mentioned objective of the present invention is achieved by a hydraulic pump for a civil aircraft hydraulic system, the hydraulic pump for a civil aircraft hydraulic system including a temperature switch, an unloading valve, and a shut-off valve. The temperature switch is located at the pressure outlet of the hydraulic pump, and the unloading valve is connected to the temperature switch and the shut-off valve to cause the shut-off valve to pop out or retract according to the state of the temperature switch. The shut-off valve is also located at the pressure outlet of the hydraulic pump. When the temperature of the hydraulic oil in the hydraulic system is within the normal operating temperature range, the temperature switch is turned off, so the unloading valve does not work, the shut-off valve is in the retracted state, and the hydraulic pump is turned on normally. When the temperature of the hydraulic oil in the hydraulic system is higher than the first temperature threshold, the temperature switch closes, thereby the unloading valve operates, the shut-off valve pops out, and the power of the hydraulic pump is reduced. When the temperature of the hydraulic oil in the hydraulic system is lower than the second temperature threshold, the temperature switch is turned off, thereby the unloading valve stops working, the shut-off valve retracts, and the hydraulic pump starts normally.

[0007] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: it can realize the temperature adaptive control of the hydraulic pump, the temperature adaptive control process does not require additional operation by the pilot, avoids the problem that the hydraulic pump cannot be automatically restarted after the temperature returns to normal after being shut down due to high temperature, and enhances the reliability and advanced nature of the hydraulic pump.

[0008] Preferably, the second temperature threshold is lower than the first temperature threshold.

[0009] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: after the hydraulic pump is shut down due to high temperature, it can be automatically restarted after the temperature returns to normal, and a certain temperature margin is left (i.e., the difference between the first temperature threshold and the second temperature threshold), ensuring that the hydraulic pump will not be frequently shut down / restarted, further enhancing the reliability and advanced nature of the hydraulic pump.

[0010] Preferably, the first temperature threshold is 100 degrees Celsius, and the second temperature threshold is 40 to 60 degrees Celsius.

[0011] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by setting an appropriate first temperature threshold and a second temperature threshold, it can automatically cut off the hydraulic energy output of the hydraulic pump to the load in time when the hydraulic system is at high temperature, protecting the hydraulic pump body from damage. It can also automatically restart the hydraulic pump after the temperature returns to normal after the hydraulic pump is shut down due to high temperature. Moreover, a certain temperature margin is left to ensure that the hydraulic pump will not be frequently shut down / restarted, further enhancing the reliability and advanced nature of the hydraulic pump.

[0012] Preferably, the normal operating temperature range is -10 to 100 degrees Celsius.

[0013] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by setting a suitable normal operating temperature range of hydraulic oil, the hydraulic pump can operate within the normal operating temperature range of hydraulic oil as much as possible, and automatically cut off the hydraulic energy output of the hydraulic pump to the load in time when the hydraulic system is at high temperature, protecting the hydraulic pump body from damage, and further enhancing the reliability and advanced nature of the hydraulic pump.

[0014] Preferably, the temperature switch integrates a temperature sensor and a controller. The temperature sensor is used to sense the temperature of the hydraulic oil at the pressure outlet of the hydraulic pump and send the hydraulic oil temperature signal to the controller for controlling the opening or closing of the temperature switch.

[0015] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by integrating a temperature sensor and controller into the temperature switch, the system control architecture is simplified, the opening or closing of the temperature switch is controlled in a timely manner, and the retraction or ejection of the shut-off valve is controlled in a timely manner.

[0016] Preferably, the unloading valve is an electromagnetic unloading valve, which is energized when working and de-energized when not working.

[0017] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by using a suitable unloading valve (electromagnetic unloading valve), the shut-off valve can be accurately and quickly popped out or retracted.

[0018] Preferably, the shut-off valve is a mechanical shut-off valve.

[0019] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by using a suitable shut-off valve (mechanical shut-off valve), the shut-off valve can be accurately and quickly popped out or retracted, with high reliability and precise control.

[0020] Preferably, the shut-off valve is configured to be spaced apart from the temperature switch and located downstream of the temperature switch.

[0021] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: avoid mutual interference between the shut-off valve and the temperature switch, and avoid inaccurate temperature sensing of the temperature switch after the shut-off valve pops out.

[0022] Preferably, when the shut-off valve pops out, the hydraulic pump remains on, but its power is reduced, and the pump outlet pressure is reduced to less than 5% of the normal pump outlet pressure.

[0023] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: when the temperature of the hydraulic oil in the hydraulic system is higher than the first temperature threshold, the temperature switch is closed, the unloading valve is working, and the shut-off valve pops out, the hydraulic pump is not directly shut down, but is turned on with low power, so as to ensure that after the temperature returns to normal, the hydraulic pump can be automatically restarted to normal working state more quickly.

[0024] The above-mentioned objectives of the present invention are further achieved by a control method for a hydraulic pump in a civil aircraft hydraulic system, wherein the hydraulic pump in the civil aircraft hydraulic system is a hydraulic pump for a civil aircraft hydraulic system as described in any of the foregoing aspects, and the method includes: Monitor the temperature of the hydraulic oil within the hydraulic system; When the temperature of the hydraulic oil in the hydraulic system is within the normal operating temperature range, the temperature switch is turned off, so the unloading valve does not work, the shut-off valve is in the retracted state, and the hydraulic pump is turned on normally. When the temperature of the hydraulic oil in the hydraulic system is higher than the first temperature threshold, the temperature switch closes, thereby the unloading valve operates, the shut-off valve pops out, and the power of the hydraulic pump is reduced. When the temperature of the hydraulic oil in the hydraulic system is lower than the second temperature threshold, the temperature switch is turned off, thereby the unloading valve stops working, the shut-off valve retracts, and the hydraulic pump starts normally.

[0025] According to the above technical solution, the control method of the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: it can realize the temperature adaptive control of the hydraulic pump, the temperature adaptive control process does not require additional operation by the pilot, avoids the problem that the hydraulic pump cannot be automatically restarted after the temperature returns to normal after being shut down due to high temperature, and enhances the reliability and advanced nature of the hydraulic pump. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the working principle of a hydraulic pump for a civil aircraft hydraulic system according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the principle of a hydraulic pump for a civil aircraft hydraulic system at high temperature, according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the principle of a hydraulic pump for a civil aircraft hydraulic system after temperature recovery, according to an embodiment of the present invention.

[0029] List of reference numerals

[0030] 1: Temperature switch; 2: Unloading valve; 3: Shut-off valve. Detailed Implementation

[0031] The following describes specific embodiments of the present invention. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. It should be understood that, in the actual implementation of any embodiment, just as in any engineering or design project, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and this can change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, some design, manufacturing, or production modifications based on the technical content disclosed herein are merely conventional technical means and should not be construed as insufficient content of this disclosure.

[0032] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in the patent application description and claims of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the element or object preceding "comprising" or "including" encompasses the element or object listed following "comprising" or "including" and its equivalents, and do not exclude other elements or objects. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0033] In the following description, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0034] Figure 1 This is a schematic diagram of the working principle of a hydraulic pump for a civil aircraft hydraulic system according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the principle of a hydraulic pump for a civil aircraft hydraulic system at high temperature, according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the principle of a hydraulic pump for a civil aircraft hydraulic system after temperature recovery, according to an embodiment of the present invention.

[0035] like Figures 1 to 3 As shown, according to an embodiment of the present invention, a hydraulic pump for a civil aircraft hydraulic system includes a temperature switch 1, an unloading valve 2, and a shut-off valve 3. Among them, temperature switch 1 is set at the pressure outlet of hydraulic pump, unloading valve 2 is connected to temperature switch 1 and shut-off valve 3, so as to make shut-off valve 3 pop up or retract according to the state of temperature switch 1. Shut-off valve 3 is also set at the pressure outlet of hydraulic pump. When the temperature of the hydraulic oil in the hydraulic system is within the normal operating temperature range, such as Figure 1 As shown, temperature switch 1 is off, so unloading valve 2 does not work, shut-off valve 3 is in the retracted state, pressure outlet load flow is normal, and hydraulic pump is started normally. When the temperature of the hydraulic oil in the hydraulic system exceeds the first temperature threshold, such as Figure 2 As shown, when temperature switch 1 is closed, unloading valve 2 is activated, shut-off valve 3 pops out, cutting off the load flow at the pressure outlet, reducing the power of the hydraulic pump, and quickly lowering the temperature of the hydraulic system. When the temperature of the hydraulic oil in the hydraulic system is lower than the second temperature threshold, such as Figure 3 As shown, temperature switch 1 is disconnected, so unloading valve 2 does not work (reset), shut-off valve 3 retracts (reset), pressure outlet load flow is restored, hydraulic pump starts normally (restart), and hydraulic power is supplied to the user.

[0036] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: it can realize the temperature adaptive control of the hydraulic pump, the temperature adaptive control process does not require additional operation by the pilot, avoids the problem that the hydraulic pump cannot be automatically restarted after the temperature returns to normal after being shut down due to high temperature, and enhances the reliability and advanced nature of the hydraulic pump.

[0037] In some embodiments, such as Figures 1 to 3 As shown, the second temperature threshold is lower than the first temperature threshold.

[0038] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: after the hydraulic pump is shut down due to high temperature, it can be automatically restarted after the temperature returns to normal, and a certain temperature margin is left (i.e., the difference between the first temperature threshold and the second temperature threshold), ensuring that the hydraulic pump will not be frequently shut down / restarted, further enhancing the reliability and advanced nature of the hydraulic pump.

[0039] In some embodiments, such as Figures 1 to 3As shown, the first temperature threshold is 100 degrees Celsius, and the second temperature threshold is 40–60 degrees Celsius. Preferably, the second temperature threshold is 50 degrees Celsius. More preferably, the difference between the first and second temperature thresholds is approximately 50 degrees Celsius.

[0040] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by setting an appropriate first temperature threshold and a second temperature threshold, it can automatically cut off the hydraulic energy output of the hydraulic pump to the load in time when the hydraulic system is at high temperature, protecting the hydraulic pump body from damage. It can also automatically restart the hydraulic pump after the temperature returns to normal after the hydraulic pump is shut down due to high temperature. Moreover, a certain temperature margin is left to ensure that the hydraulic pump will not be frequently shut down / restarted, further enhancing the reliability and advanced nature of the hydraulic pump.

[0041] In some embodiments, such as Figures 1 to 3 As shown, the normal operating temperature range is -10 to 100 degrees Celsius. Preferably, the upper limit of the normal operating temperature range is equal to the first temperature threshold.

[0042] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by setting a suitable normal operating temperature range of hydraulic oil, the hydraulic pump can operate within the normal operating temperature range of hydraulic oil as much as possible, and automatically cut off the hydraulic energy output of the hydraulic pump to the load in time when the hydraulic system is at high temperature, protecting the hydraulic pump body from damage, and further enhancing the reliability and advanced nature of the hydraulic pump.

[0043] In some embodiments, such as Figures 1 to 3 As shown, temperature switch 1 integrates a temperature sensor and a controller. The temperature sensor is used to sense the temperature of the hydraulic oil at the pressure outlet of the hydraulic pump and sends the hydraulic oil temperature signal to the controller to control the opening or closing of temperature switch 1.

[0044] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by integrating a temperature sensor and controller into the temperature switch, the system control architecture is simplified, the opening or closing of the temperature switch is controlled in a timely manner, and the retraction or ejection of the shut-off valve is controlled in a timely manner.

[0045] In some embodiments, such as Figures 1 to 3 As shown, unloading valve 2 is an electromagnetic unloading valve. Unloading valve 2 is energized when it is working and is not energized when it is not working.

[0046] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by using a suitable unloading valve (electromagnetic unloading valve), the shut-off valve can be accurately and quickly popped out or retracted.

[0047] In some embodiments, such as Figures 1 to 3 As shown, shut-off valve 3 is a mechanical shut-off valve.

[0048] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: by using a suitable shut-off valve (mechanical shut-off valve), the shut-off valve can be accurately and quickly popped out or retracted, with high reliability and precise control.

[0049] In some embodiments, such as Figures 1 to 3 As shown, the shut-off valve 3 is configured to be separated from the temperature switch 1 by a certain distance and is located downstream of the temperature switch 1.

[0050] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: avoid mutual interference between the shut-off valve and the temperature switch, and avoid inaccurate temperature sensing of the temperature switch after the shut-off valve pops out.

[0051] In some embodiments, such as Figures 1 to 3 As shown, when shut-off valve 3 pops out, the hydraulic pump is still running, but the power is reduced, and the pump outlet pressure is reduced to less than 5% of the normal pump outlet pressure.

[0052] According to the above technical solution, the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: when the temperature of the hydraulic oil in the hydraulic system is higher than the first temperature threshold, the temperature switch is closed, the unloading valve is working, and the shut-off valve pops out, the hydraulic pump is not directly shut down, but is turned on with low power, so as to ensure that after the temperature returns to normal, the hydraulic pump can be automatically restarted to normal working state more quickly.

[0053] like Figures 1 to 3 As shown, according to an embodiment of the present invention, a control method for a hydraulic pump in a civil aircraft hydraulic system includes: Monitor the temperature of the hydraulic oil in the hydraulic system; When the temperature of the hydraulic oil in the hydraulic system is within the normal operating temperature range, such as Figure 1 As shown, temperature switch 1 is off, so unloading valve 2 does not work, shut-off valve 3 is in the retracted state, pressure outlet load flow is normal, and hydraulic pump is started normally. When the temperature of the hydraulic oil in the hydraulic system exceeds the first temperature threshold, such as Figure 2 As shown, when temperature switch 1 is closed, unloading valve 2 is activated, shut-off valve 3 pops out, cutting off the load flow at the pressure outlet, reducing the power of the hydraulic pump, and quickly lowering the temperature of the hydraulic system. When the temperature of the hydraulic oil in the hydraulic system is lower than the second temperature threshold, such as Figure 3As shown, temperature switch 1 is disconnected, so unloading valve 2 does not work (reset), shut-off valve 3 retracts (reset), pressure outlet load flow is restored, hydraulic pump starts normally (restart), and hydraulic power is supplied to the user.

[0054] According to the above technical solution, the control method of the hydraulic pump for the hydraulic system of civil aircraft of the present invention can achieve the following beneficial technical effects: it can realize the temperature adaptive control of the hydraulic pump, the temperature adaptive control process does not require additional operation by the pilot, avoids the problem that the hydraulic pump cannot be automatically restarted after the temperature returns to normal after being shut down due to high temperature, and enhances the reliability and advanced nature of the hydraulic pump.

[0055] The specific embodiments of the present invention have been described above. However, those skilled in the art will understand that the above specific embodiments do not constitute a limitation on the present invention. Those skilled in the art can make various modifications based on the above disclosure without exceeding the scope of the present invention.

Claims

1. A hydraulic pump for a civil aircraft hydraulic system, the hydraulic pump for a civil aircraft hydraulic system comprising a temperature switch, an unloading valve, and a shut-off valve; in, The temperature switch is located at the pressure outlet of the hydraulic pump. The unloading valve is connected to the temperature switch and the shut-off valve to cause the shut-off valve to pop out or retract according to the state of the temperature switch. The shut-off valve is also located at the pressure outlet of the hydraulic pump. When the temperature of the hydraulic oil in the hydraulic system is within the normal operating temperature range, the temperature switch is turned off, so the unloading valve does not work, the shut-off valve is in the retracted state, and the hydraulic pump is turned on normally. When the temperature of the hydraulic oil in the hydraulic system is higher than the first temperature threshold, the temperature switch closes, thereby the unloading valve operates, the shut-off valve pops out, and the power of the hydraulic pump is reduced. When the temperature of the hydraulic oil in the hydraulic system is lower than the second temperature threshold, the temperature switch is turned off, thereby the unloading valve stops working, the shut-off valve retracts, and the hydraulic pump starts normally.

2. The hydraulic pump for a civil aircraft hydraulic system as described in claim 1, characterized in that, The second temperature threshold is lower than the first temperature threshold.

3. The hydraulic pump for a civil aircraft hydraulic system as described in claim 2, characterized in that, The first temperature threshold is 100 degrees Celsius, and the second temperature threshold is 40 to 60 degrees Celsius.

4. The hydraulic pump for a civil aircraft hydraulic system as described in claim 1, characterized in that, The normal operating temperature range is -10 to 100 degrees Celsius.

5. The hydraulic pump for a civil aircraft hydraulic system as described in claim 1, characterized in that, The temperature switch integrates a temperature sensor and a controller. The temperature sensor is used to sense the temperature of the hydraulic oil at the pressure outlet of the hydraulic pump and sends the hydraulic oil temperature signal to the controller to control the opening or closing of the temperature switch.

6. The hydraulic pump for a civil aircraft hydraulic system as described in claim 1, characterized in that, The unloading valve is an electromagnetic unloading valve, which is energized when working and de-energized when not working.

7. The hydraulic pump for a civil aircraft hydraulic system as described in claim 1, characterized in that, The shut-off valve is a mechanical shut-off valve.

8. The hydraulic pump for a civil aircraft hydraulic system as described in claim 1, characterized in that, The shut-off valve is configured to be spaced apart from the temperature switch by a certain distance and is located downstream of the temperature switch.

9. The hydraulic pump for a civil aircraft hydraulic system as described in claim 1, characterized in that, When the shut-off valve pops out, the hydraulic pump remains on, but its power is reduced, and the pump outlet pressure drops to less than 5% of the normal pump outlet pressure.

10. A control method for a hydraulic pump in a civil aircraft hydraulic system, wherein the hydraulic pump in the civil aircraft hydraulic system is a hydraulic pump for a civil aircraft hydraulic system as described in any one of claims 1-9, the method comprising: Monitor the temperature of the hydraulic oil within the hydraulic system; When the temperature of the hydraulic oil in the hydraulic system is within the normal operating temperature range, the temperature switch is turned off, so the unloading valve does not work, the shut-off valve is in the retracted state, and the hydraulic pump is turned on normally. When the temperature of the hydraulic oil in the hydraulic system is higher than the first temperature threshold, the temperature switch closes, thereby the unloading valve operates, the shut-off valve pops out, and the power of the hydraulic pump is reduced. When the temperature of the hydraulic oil in the hydraulic system is lower than the second temperature threshold, the temperature switch is turned off, thereby the unloading valve stops working, the shut-off valve retracts, and the hydraulic pump starts normally.

Images