Hydraulic pressure and spring coupled driving system and control method thereof

Abstract

The invention discloses a hydraulic and spring coupled driving system and a control method thereof. The hydraulic and spring coupled driving system comprises a cylinder body; the piston divides the internal space of the cylinder body into a first driving cavity and a second driving cavity, one of the first driving cavity and the second driving cavity is a hydraulic driving cavity, and the other one of the first driving cavity and the second driving cavity is a spring driving cavity; the driving spring is arranged in the spring driving cavity, one end of the driving spring abuts against the piston, and the other end of the driving spring abuts against the inner wall of the spring driving cavity; the piston valve comprises a valve seat arranged on the piston and a valve rod arranged in the valve seat; according to the scheme, energy consumption can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of liquid hydrogen pump driving, and in particular to a hydraulic and spring coupled driving system and a control method thereof. Background Art

[0002] Liquefied hydrogen is stored in tanks, which are usually made of steel and have an ultra-low temperature (20K). Hydrogen refueling stations require high-pressure gaseous hydrogen to refuel vehicles loaded with compressed hydrogen. Therefore, a high-pressure liquid hydrogen pump is needed to compress the liquid hydrogen to a high pressure, and then vaporize it into high-pressure gaseous hydrogen for use by the hydrogen refueling machine.

[0003] Usually, the driving system of high-pressure liquid hydrogen pump is a bidirectional hydraulic driving system, that is, the extension stroke and retraction stroke of the piston are driven by hydraulic means. However, there is a certain pressure in the liquid hydrogen storage tank itself, which makes the hydraulic driving system use part of the pressure in the liquid hydrogen storage tank during the suction stroke. In this case, the hydraulic driving method is still selected to generate a large pressure, which invisibly causes a waste of energy. Summary of the invention

[0004] The technical problem to be solved by the present application is the problem of low energy utilization and waste caused by the application of the existing bidirectional hydraulic drive system in a high-pressure liquid hydrogen pump. To this end, the present application proposes a hydraulic and spring coupled drive system and a control method thereof.

[0005] In response to the above technical problems, this application provides the following technical solutions:

[0006] In a first aspect, the technical solution of the present application provides a hydraulic and spring coupled drive system, which is applied to a high-pressure liquid hydrogen pump, comprising:

[0007] Cylinder body;

[0008] A piston is disposed in the cylinder body, wherein the piston divides the internal space of the cylinder body into a first driving chamber and a second driving chamber, wherein one of the first driving chamber and the second driving chamber is a hydraulic driving chamber, and the other is a spring driving chamber;

[0009] A driving spring is disposed in the spring driving chamber, one end of the driving spring abuts against the piston, and the other end of the driving spring abuts against the inner wall of the spring driving chamber;

[0010] A piston valve comprises a valve seat formed on the piston and a valve core arranged in the valve seat; the valve core comprises an umbrella-shaped head and a valve stem connected to the umbrella-shaped head; when the umbrella-shaped head is sealed with the valve seat, the end of the valve stem extends to the outside of the piston; when the sealing connection between the umbrella-shaped head and the valve seat is released, the through hole formed in the valve seat connects the first drive chamber and the second drive chamber.

[0011] In some embodiments of the hydraulic and spring coupled drive system, the movement of the piston toward the second drive chamber corresponds to a compression stroke, and the movement of the piston toward the first drive chamber corresponds to a suction stroke; when the drive spring is arranged in the second drive chamber, the drive spring is a compression spring.

[0012] In some embodiments of the hydraulic and spring coupled drive system, when the piston moves toward the second drive chamber, it corresponds to a compression stroke, and when the piston moves toward the first drive chamber, it corresponds to an intake stroke; when the drive spring is arranged in the first drive chamber, the drive spring is a tension spring.

[0013] The hydraulic and spring coupled drive system of some embodiments further comprises:

[0014] An electrically controlled reversing valve, wherein the first port is connected to the first driving chamber, the second port is connected to the second driving chamber, the third port is connected to the oil tank via a hydraulic pump, and the fourth port is connected to the oil tank;

[0015] A controller is connected to the electronically controlled reversing valve and the hydraulic pump; the controller controls the state of the electronically controlled reversing valve to make the first drive chamber and / or the second drive chamber connected to the oil tank; the controller controls the hydraulic pump to start when the piston performs a compression stroke, and the controller controls the hydraulic pump to stop working when the piston performs a suction stroke.

[0016] The hydraulic and spring coupled drive system of some embodiments further comprises:

[0017] A pressure sensor is arranged on the passage between the first driving chamber and the electrically controlled reversing valve;

[0018] The pressure sensor is used to detect the hydraulic oil pressure value of the first driving chamber and send the hydraulic oil pressure value to the controller.

[0019] The hydraulic and spring coupled drive system of some embodiments further comprises:

[0020] A flow sensor is arranged on the passage between the first driving chamber and the electric-controlled reversing valve;

[0021] The flow sensor is used to detect the flow value of the hydraulic oil flowing into or out of the first driving chamber, and send the hydraulic oil flow value to the controller.

[0022] In some embodiments of the hydraulic and spring coupled drive system, a buffer cavity is formed on the inner wall of the first drive cavity; a buffer boss is formed on the surface of the piston located on one side of the first drive cavity; and the buffer cavity matches the buffer boss.

[0023] In some embodiments of the hydraulic and spring coupled drive system, a buffer boss is formed on the inner wall of the second drive chamber, and a concave cavity is formed on the surface of the piston located on one side of the second drive chamber; the buffer boss matches the concave cavity.

[0024] In a second aspect, the technical solution of the present application provides a control method for a hydraulic and spring coupled drive system, which is used in the hydraulic and spring coupled drive system of any one of the solutions in the first aspect, with the second drive chamber as the spring drive chamber, comprising:

[0025] Control the start-up of the hydraulic pump and the action of the electronically controlled reversing valve to make the passage between the first driving chamber and the hydraulic pump communicate in a positive direction;

[0026] The hydraulic oil in the oil tank is transported to the first driving chamber, and after the hydraulic oil enters the first driving chamber, the piston is driven to move toward the second driving chamber; the driving spring is deformed and stores energy;

[0027] After the piston moves to the end of the stroke of the second drive chamber, the piston valve is actuated to connect the first drive chamber with the second drive chamber, and the hydraulic oil in the first drive chamber is released to the second drive chamber;

[0028] The electrically controlled reversing valve is controlled to operate again, so that the first driving chamber is connected to the passage between the oil tank in reverse, the stored energy of the driving spring is released, and the piston is pushed to move in the direction of the first driving chamber, and the hydraulic oil in the first driving chamber flows into the oil tank and the second driving chamber through the reversely connected passage;

[0029] After the piston moves to the end of the stroke of the first drive chamber, the process returns to the step of starting the control hydraulic pump and operating the electronically controlled reversing valve to connect the passage between the first drive chamber and the hydraulic pump in the forward direction.

[0030] The control method of the hydraulic and spring coupled drive system described in some schemes controls the flow rate of the hydraulic oil delivered by the hydraulic pump to the first drive chamber when controlling the piston to move in the direction of the second drive chamber, so as to control the movement speed of the piston to a preset speed.

[0031] The control method of the hydraulic and spring coupled drive system described in some embodiments further includes:

[0032] in response to a stop position determination signal;

[0033] The state of the electrically controlled reversing valve is controlled to the stop position state, and all passages connected to the oil tank are in a disconnected state; in the stop position state, the first drive chamber and the second drive chamber on both sides of the piston apply the same pressure value to the piston.

[0034] The technical solution of this application has the following technical effects compared with the prior art:

[0035] The application provides a hydraulic and spring coupled drive system and a control method thereof. The drive system adopts two drive modes: hydraulic drive and spring drive. For a high-pressure liquid hydrogen pump, one side of the spring drive can be used to cooperate with the liquid hydrogen storage tank. The superposition of the spring force and the pressure in the liquid hydrogen storage tank is sufficient to push the piston. There is no need to use a high-pressure hydraulic drive method, which can reduce energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, which will help to understand the purpose and advantages of the present application, wherein:

[0037] Figure 1a and Figure 1b Schematic diagrams of different structures of the hydraulic and spring coupled drive system described in the embodiments of the present application;

[0038] Figure 2 This is a schematic diagram of the structure of the hydraulic and spring coupled drive system described in an embodiment of the present application;

[0039] Figure 3 This is a schematic diagram of the structure of the piston valve described in the embodiment of the present application;

[0040] Figure 4 This is a schematic structural diagram of the valve stem and valve seat of the piston valve according to the embodiment of the present application when the sealing connection is released;

[0041] Figure 5 This is a cross-sectional schematic diagram of a valve stem and a valve seat of a piston valve according to an embodiment of the present application;

[0042] Figure 6 This is a flow chart of a control method of a hydraulic and spring coupled drive system according to an embodiment of the present application;

[0043] Figure 7 This is a schematic structural diagram of an electrically controlled reversing valve with an intermediate stop position according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0045] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0046] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0047] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0048] Hydraulic drive systems are often used as a power source for reciprocating pistons. The piston moves together with the piston rod, and the other end of the piston rod is connected to the work-producing machine to achieve the desired mechanical work. Generally, the output force driven by the hydraulic system is relatively large, and small output forces are generally driven by simpler pneumatic pressure. Most hydraulic drives are double-acting hydraulic cylinders, that is, both the extension stroke and the retraction stroke are driven by hydraulic means. This is because the positive and reverse forces (or resistance) of the machine connected to the rear end of the piston rod are often always present and relatively large.

[0049] The application scenario for each scheme in the following embodiments of the present application is a high-pressure liquid hydrogen pump. The high-pressure liquid hydrogen pump is used to compress liquid hydrogen to a high pressure, and then vaporize it into high-pressure gas hydrogen for use in a hydrogenation machine. The high-pressure liquid hydrogen pump compresses the liquid. When hydraulic drive is used, the hydraulic fluid can flow through the hydraulic pipeline to a certain distance and transmit the pressure to the hydraulic piston. High-current electrical equipment such as motors can be kept away from liquid hydrogen and operated at a safe distance, which can more reliably achieve safety and explosion protection. The high-pressure liquid hydrogen pump is a submerged design, that is, the liquid hydrogen pump is placed in a liquid hydrogen storage tank, the drive end leaks out, and the cold end is immersed in liquid hydrogen. The submerged liquid hydrogen pump eliminates the thermal cycle step of the cold end, greatly reducing the equipment failure rate and the total evaporation loss of hydrogen. The submerged liquid hydrogen pump can also be hydrogenated instantly as needed, which is very suitable for cyclic operations that are frequently started and stopped within an hour. In this case, it is more advantageous to use a hydraulic drive rather than a direct electric drive liquid hydrogen pump. The hydraulic drive allows the physical separation between the drive motor and the liquid hydrogen pump, so that the liquid hydrogen pump can be placed directly in the liquid storage tank. This feature allows the pump to operate for a long period of time and can significantly reduce the maintenance cost of the pump.

[0050] This embodiment provides a hydraulic and spring coupled drive system, which is applied to a high-pressure liquid hydrogen pump, such as Figure 1a and Figure 1b As shown, it includes a cylinder body 10; a piston 20, which is arranged in the cylinder body 10, and the piston 20 divides the internal space of the cylinder body 10 into a first driving chamber 11 and a second driving chamber 12, one of the first driving chamber 11 and the second driving chamber 12 is a hydraulic driving chamber, and the other is a spring driving chamber. It also includes a driving spring 13, which is arranged in the spring driving chamber, one end of the driving spring abuts against the piston 20, and the other end of the driving spring abuts against the inner wall of the spring driving chamber. A piston valve comprises a valve seat 201 formed on the piston 20 and a valve core arranged in the valve seat, wherein the valve core comprises an umbrella-shaped head 203 and a valve stem 202 connected to the umbrella-shaped head 203; in a specific implementation, the cross-sectional shape of the umbrella-shaped head 203 comprises a circle, a quadrilateral or a polygon; when the umbrella-shaped head 203 is sealed and connected to the valve seat 201, the end of the valve stem 202 extends to the outside of the piston; when the sealing connection between the umbrella-shaped head 203 and the valve seat 201 is released, the through hole formed in the valve seat 201 connects the first drive chamber 11 and the second drive chamber 12.

[0051] Combination Figure 1a and Figure 1b It can be determined that there are multiple ways to set the first drive chamber 11 and the second drive chamber 12. In specific applications, the working state of the drive system can be divided according to the two strokes of the piston rod extending and the piston rod retracting. Figure 1a In the embodiment, the drive spring 13 is compressed when the piston rod is extended. Figure 1bIn the embodiment, the drive spring 13 is compressed when the piston rod retracts.

[0052] In addition, hydraulic oil through holes are provided in both the first driving chamber 11 and the second driving chamber 12, through which hydraulic oil can be sucked in or discharged.

[0053] Combination Figure 1a and Figure 1b , it can be determined that the drive spring 13 can be a compression spring or a tension spring. When the piston 20 moves toward the second drive chamber 12, it corresponds to the suction stroke, and when the piston 20 moves toward the first drive chamber 11, it corresponds to the compression stroke; when the drive spring 13 is arranged in the second drive chamber 12, the drive spring 13 is a compression spring. When the piston 20 moves toward the second drive chamber 12, it corresponds to the compression stroke, and when the piston 20 moves toward the first drive chamber 11, it corresponds to the suction stroke; when the drive spring 13 is arranged in the first drive chamber 11, the drive spring 13 is a tension spring. Furthermore, the drive spring 13 can also be divided into many types according to its shape, such as a cylindrical spring, a conical spring, etc. According to the medium, it can be divided into a spiral steel spring, an air spring, a combination spring, etc. The drive spring 13 in the present application can be selected from any of the above types.

[0054] Preferably, if Figure 2 As shown, the system in the above scheme also includes a controller 30 and an electrically controlled reversing valve 40, wherein the first port of the electrically controlled reversing valve 40 is connected to the first drive chamber 11, the second port is connected to the second drive chamber 12, the third port is connected to the oil tank 50 via the hydraulic pump 60, and the fourth port is connected to the oil tank 50; the controller 20 is connected to the electrically controlled reversing valve 40 and the hydraulic pump 60; the controller 30 controls the state of the electrically controlled reversing valve 40 to make the first drive chamber 11 and / or the second drive chamber 12 communicate with the oil tank 50; the controller 30 controls the hydraulic pump 60 to start when the piston 20 performs a compression stroke, and the controller 30 controls the hydraulic pump to stop working when the piston performs an intake stroke, that is, the hydraulic pump 60 idles. In this way, the problem of wasting time when the hydraulic pump 60 is turned off and then turned on can be avoided by setting it to idle. There is no need to frequently start and stop the hydraulic pump when the intake-compression-re-intake cycle is continuously performed.

[0055] The electronically controlled reversing valve 40 can be selected according to the passage requirements, and different ports of different electronically controlled reversing valves have different conduction modes, such as linear conduction, cross conduction, etc.

[0056] Furthermore, if Figure 2As shown, the system further includes a pressure sensor 70, which is disposed on the passage between the first drive chamber 11 and the hydraulic pump 60; the pressure sensor 70 is used to detect the hydraulic oil pressure value of the first drive chamber 11 and send the hydraulic oil pressure value to the controller 30. The piston stroke can be monitored by the pressure sensor. Specifically, Figure 2 , Figure 3 , Figure 4 and Figure 5 Taking the structure shown as an example, the hydraulic pump 60, the electrically controlled reversing valve 40 and the pressure sensor 70 are all connected to the controller 30, and the hydraulic pump 60 is connected between the oil tank 50 and the first drive chamber 11, and the hydraulic pump 60 delivers the hydraulic oil in the oil tank 50 to the first drive chamber 11. As can be seen from the figure, the valve stem 201 moves in the valve chamber 20, and when the first drive chamber 11 on the left side of the piston 20 is injected with high-pressure hydraulic oil, its umbrella-shaped head 203 is pushed to the right against the valve seat 201 under the push of the hydraulic oil, and the piston valve is closed. As shown in the figure, because the right side of the piston is the spring drive chamber, which is connected to the oil tank 50 and has a very low pressure, the pressure difference on both sides of the piston 20 is very large, and the piston 20 is subjected to a large rightward thrust under the action of the large pressure difference, and the piston 20 moves to the right. When the piston 20 reaches the end of the stroke, the valve stem 202 extends a small portion of the piston, and the valve stem 202 will first contact the inner wall of the cavity to stop moving. At this time, when the piston continues to move to the right, the sealing surface on the umbrella-shaped head 203 will separate from the valve seat 201 on the piston, and the valve will open. The hydraulic oil on the left side of the piston 20 flows to the right side of the piston through the flow channel 204 opened by the piston valve stem. The pressure on both sides of the piston is balanced, and the piston 20 loses the thrust under the differential pressure, and the piston 20 stops.

[0057] In the hydraulic driving stroke of the above-mentioned compressed liquid hydrogen, the pressure signal of the hydraulic oil in the first driving chamber 11 is input into the controller 30 in real time through the pressure sensor 106. Since the driving spring 13 in the right spring chamber is squeezed, the reaction force of the driving spring 13 continues to increase, and the pressure signal of the hydraulic oil also continues to increase. When the piston reaches the end point, the umbrella-shaped head 203 opens, the hydraulic oil flows to the right side of the piston, the pressure on the left side is transmitted to the right side, the pressure on the right side increases, the pressure on the left side is relieved, the pressure difference on both sides of the piston decreases suddenly, and the piston movement stops. By monitoring the pressure change, the peak moment of the hydraulic oil pressure value in the first driving chamber 11 can be clearly judged, which is the last moment before the umbrella-shaped head 203 opens. Subsequently, the pressure of the hydraulic oil in the first driving chamber 11 decreases rapidly, showing the pressure relief after the umbrella-shaped head 203 is opened. Therefore, the controller can judge the stop of the stroke of the compressed liquid hydrogen of the piston movement based on this principle.

[0058] The controller 30 cuts off the passage between the hydraulic pump 60 and the first drive chamber 11 through the electrically controlled reversing valve 40, and connects the first drive chamber 11 to the oil tank 50 with a normal pressure value, and the high pressure in the hydraulic oil in the first drive chamber 11 is released. The piston then moves to the left under the elastic force of the drive spring 13. At this time, the hydraulic oil in the first drive chamber 11 begins to flow to the oil tank 50 under the push of the piston, and its flow rate is determined by the pressure acting on the hydraulic oil after the elastic force of the drive spring 13 is transmitted to the piston. Since the flow resistance of the hydraulic oil is very small, the pressure of the hydraulic oil is much smaller than the high pressure of the hydraulic drive stroke. In this process, the pressure of the hydraulic oil in the first drive chamber also continues to decrease, and the flow rate of the hydraulic oil also continues to decrease. As the piston stops moving, the pressure reaches a static pressure in the oil tank 50, that is, the pressure value of the hydraulic oil is consistent with the normal pressure value of the oil tank. At the same time, since there is no more hydraulic oil flowing in the hydraulic chamber, the pressure value can be selected to judge the end of the stroke. The present application judges that the piston stops inhaling liquid hydrogen based on this feature.

[0059] Furthermore, the hydraulic and spring coupled drive system may further include: a flow sensor, disposed on the passage between the first drive chamber 11 and the hydraulic pump 60; the flow sensor is used to detect the flow value of the hydraulic oil flowing into or out of the first drive chamber 11, and send the hydraulic oil flow value to the controller 30. Figure 1a As shown, when the piston 20 moves to the left side in the figure to the end point, the hydraulic oil in the first driving chamber 11 is emptied and the flow rate is zero. Therefore, the flow rate can also be used to determine the moment of switching the movement of the piston.

[0060] Preferably, if Figure 1a-1b As shown, the inner wall of the first driving cavity 11 is formed with a buffer cavity; the surface of the piston 20 located on the side of the first driving cavity is formed with a buffer boss; the buffer cavity matches the buffer boss. Alternatively, the inner wall of the second driving cavity 12 is formed with a buffer boss, and the surface of the piston located on the side of the second driving cavity is formed with a cavity; the buffer boss matches the cavity. That is, a buffer structure can be set in the first driving cavity and the second driving cavity to avoid collision caused by excessive speed during the movement of the piston.

[0061] In the drive system of the above scheme, the compression stroke (extension) is achieved by controlling the electronically controlled reversing valve 40 to introduce the high-pressure hydraulic oil at the outlet of the hydraulic pump 60 into the first driving chamber 11 (left side of the piston). At the beginning, the electronically controlled reversing valve 40 is in the left position, and the hydraulic piston is pushed by the hydraulic oil pressure in the hydraulic cylinder body, resulting in a displacement to the right. The long shaft drives the cold end piston to compress the liquid hydrogen to do work, thereby achieving high-pressure liquid hydrogen output, and compressing the spring to store energy. When the piston 20 reaches the end point, the valve stem 202 of the piston valve contacts the cylinder wall, the piston valve opens, the pressure on both sides of the piston is balanced, and the piston stops. The suction stroke (retraction) is driven by the spring to return quickly. By controlling the electromagnetic reversing valve 40, the electromagnetic reversing valve 40 is in the right position. At this time, the hydraulic pipeline connection will cause the oil pressure on the left side of the piston 20 to be released, so that the left side of the piston 20 loses the pressure of the hydraulic oil. The piston 20 moves to the left to the end point under the action of the spring rigidity force, thereby achieving reversal and completing the suction stroke. When the suction stroke (retraction) is about to reach the end point under the action of the spring, the force of the spring is constantly weakened and the piston speed is reduced. After the boss on the piston contacts the cavity, the buffer starts to work. The boss moves into the cavity, squeezing the hydraulic oil in the cavity. Under the squeezing, the hydraulic oil is squeezed out from the gap between the boss and the cavity, generating a large reaction force. The reaction force continues to increase with the movement of the relative position between the boss and the cavity, and finally balances with the decreasing elastic force of the spring, and the piston stops moving smoothly. It can be understood that the suction stroke (retraction) is achieved by the spring force. During the suction stroke (retraction), the hydraulic oil is directly connected to the oil storage tank, and the high pressure of the hydraulic oil has been released. The work done by the elastic force of the spring is used to: overcome the dynamic and static friction of the system, including the dynamic and static friction acting on the piston rod and the piston; the resistance brought by the rear system driven by the piston rod; the flow resistance that pushes the hydraulic oil to circulate back to the oil storage tank; and push the piston to move at a certain speed. The spring stiffness in this solution can be customized as needed, and there are suitable working force values ​​at both the compressed position and the relaxed position, so that the spring driving effect is ideal.

[0062] The embodiment of the present application also provides a control method for a hydraulic and spring coupled drive system, which is used in any of the hydraulic and spring coupled drive systems described above, with the second drive chamber being used as the spring drive chamber, such as Figure 6 As shown, including:

[0063] S10: Control the hydraulic pump to start and the electronically controlled reversing valve to operate, so that the passage between the first driving chamber and the electronically controlled reversing valve is connected in a positive direction.

[0064] S20: Control the hydraulic pump to start, and deliver the hydraulic oil in the oil tank to the first driving chamber. After the hydraulic oil enters the first driving chamber, it drives the piston to move toward the second driving chamber; and the driving spring is deformed and stores energy.

[0065] S30: After the piston moves to the end of the stroke of the second driving chamber, the piston valve is actuated to connect the first driving chamber with the second driving chamber, and the hydraulic oil in the first driving chamber is released to the second driving chamber.

[0066] S40: Control the electrically controlled reversing valve to operate again, so that the first drive chamber is connected to the passage between the oil tank in reverse, the stored energy of the drive spring is released, pushing the piston to move in the direction of the first drive chamber, and the hydraulic oil in the first drive chamber flows into the oil tank and the second drive chamber through the reversely connected passage.

[0067] S50: After the piston moves to the end of the stroke of the first drive chamber, return to S10 to start the control hydraulic pump and actuate the electronically controlled reversing valve to connect the passage between the first drive chamber and the hydraulic pump in the forward direction.

[0068] When the piston is controlled to move toward the second drive chamber, the flow rate of the hydraulic oil delivered to the first drive chamber by the hydraulic pump is controlled to control the movement speed of the piston to a preset speed. The speed of the compression stroke (extension) is a design value, for example: a preset speed of 30 mm / s and a peak speed of 250 mm / s.

[0069] Through the above scheme provided by the present application, the suction stroke (retraction) is a quick return of the spring by using the combination of spring drive and hydraulic drive. The speed of spring return is generally higher than the speed of hydraulic pressure, because the hydraulic pressure is limited by the displacement of the hydraulic oil pump and will not be too high, while the spring drives the piston to move with the maximum elastic force in the compressed state, and the resistance is very small, so the speed is faster. The increase in the retraction speed can speed up the working cycle of the pump, thereby increasing the displacement of the pump per unit time. In addition, the speed of quick return should not be too high, which can be controlled and selected during the spring selection and design, and controlled by changing the stiffness (force value) of the spring and changing the resistance. In fact, the circulation of hydraulic oil in the hydraulic pipeline naturally plays a certain damping role on the quick return of the piston. If greater damping is required, methods such as adding a flow limiting resistance member can be considered. When the stroke driven by the spring force is about to reach the end point, a boss cavity buffer is used for buffering. The buffer controls the piston speed when reaching the end point, which can effectively avoid noise and vibration and achieve a smooth stop of the piston.

[0070] Furthermore, the above method also includes:

[0071] S60: responding to a stop bit determination signal.

[0072] S70: Control the state of the electrically controlled reversing valve to the stop position state, and all passages connected to the oil tank are in a disconnected state; in the stop position state, the first drive chamber and the second drive chamber on both sides of the piston apply the same pressure value to the piston.

[0073] The natural stop position is the relative position of the piston in the natural state when the hydraulic oil is removed, that is, the final stop position under the action of the spring force. This is a unique feature of this case. The innovative design of spring return can have two different stop positions, one piston stop position is the piston stops on the left side of the hydraulic cylinder, and the other stop position is the piston stops on the right side. The two stop positions correspond to different stop positions of the cold end piston at the cold end. It can be selected according to user needs. Unlike the natural stop position, under normal conditions, if necessary, the piston can stop at any position under the control of the control system. Figure 7 The structure of an electrically controlled reversing valve with a stop position is shown. For example, when the spring drive is used for compressing liquid hydrogen, if a short stroke or a partial stroke is required, the control system can intervene to switch the reversing valve to an intermediate stop position.

[0074] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A hydraulic and spring coupled drive system, used in a high-pressure liquid hydrogen pump, characterized in that: include: Cylinder body; A piston is disposed in the cylinder body, wherein the piston divides the internal space of the cylinder body into a first driving chamber and a second driving chamber, wherein one of the first driving chamber and the second driving chamber is a hydraulic driving chamber, and the other is a spring driving chamber; A driving spring is disposed in the spring driving chamber, one end of the driving spring abuts against the piston, and the other end of the driving spring abuts against the inner wall of the spring driving chamber; A piston valve comprises a valve seat formed on the piston and a valve core arranged in the valve seat; the valve core comprises an umbrella-shaped head and a valve stem connected to the umbrella-shaped head; when the umbrella-shaped head is sealed with the valve seat, the end of the valve stem extends to the outside of the piston; when the sealing connection between the umbrella-shaped head and the valve seat is released, the through hole formed in the valve seat connects the first drive chamber and the second drive chamber.

2. The hydraulic and spring coupled drive system according to claim 1, characterized in that: When the piston moves toward the second driving chamber, it corresponds to a compression stroke, and when the piston moves toward the first driving chamber, it corresponds to a suction stroke; when the driving spring is arranged in the second driving chamber, the driving spring is a compression spring.

3. The hydraulic and spring coupled drive system according to claim 1, characterized in that: When the piston moves toward the second driving chamber, it corresponds to a compression stroke, and when the piston moves toward the first driving chamber, it corresponds to a suction stroke; when the driving spring is arranged in the first driving chamber, the driving spring is a tension spring.

4. The hydraulic and spring coupled drive system according to any one of claims 1 to 3, characterized in that: Also includes: An electrically controlled reversing valve, wherein the first port is connected to the first driving chamber, the second port is connected to the second driving chamber, the third port is connected to the oil tank via a hydraulic pump, and the fourth port is connected to the oil tank; A controller is connected to the electronically controlled reversing valve and the hydraulic pump; the controller controls the state of the electronically controlled reversing valve to make the first drive chamber and / or the second drive chamber connected to the oil tank; the controller controls the hydraulic pump to start when the piston performs a compression stroke, and the controller controls the hydraulic pump to stop working when the piston performs a suction stroke.

5. The hydraulic and spring coupled drive system according to claim 4, characterized in that: Also includes: A pressure sensor is arranged on the passage between the first driving chamber and the electrically controlled reversing valve; The pressure sensor is used to detect the hydraulic oil pressure value of the first driving chamber and send the hydraulic oil pressure value to the controller.

6. The hydraulic and spring coupled drive system according to claim 5, characterized in that: Also includes: A flow sensor is arranged on the passage between the first driving chamber and the electric-controlled reversing valve; The flow sensor is used to detect the flow value of the hydraulic oil flowing into or out of the first driving chamber, and send the hydraulic oil flow value to the controller.

7. The hydraulic and spring coupled drive system according to any one of claims 1 to 3, characterized in that: The inner wall of the first driving cavity is formed with a buffer cavity; the surface of the piston located at one side of the first driving cavity is formed with a buffer boss; the buffer cavity matches the buffer boss.

8. The hydraulic and spring coupled drive system according to any one of claims 1 to 3, characterized in that: The inner wall of the second driving cavity is formed with a buffer boss, and the surface of the piston located at one side of the second driving cavity is formed with a concave cavity; the buffer boss matches the concave cavity.

9. A control method for a hydraulic and spring coupled drive system, used for the hydraulic and spring coupled drive system according to any one of claims 1 to 7, characterized in that: The second driving chamber is used as a spring driving chamber, comprising: Control the start-up of the hydraulic pump and the action of the electronically controlled reversing valve to make the passage between the first driving chamber and the hydraulic pump communicate in a positive direction; The hydraulic oil in the oil tank is transported to the first driving chamber, and after the hydraulic oil enters the first driving chamber, the piston is driven to move toward the second driving chamber; the driving spring is deformed and stores energy; After the piston moves to the end of the stroke of the second drive chamber, the piston valve is actuated to connect the first drive chamber with the second drive chamber, and the hydraulic oil in the first drive chamber is released to the second drive chamber; The electrically controlled reversing valve is controlled to operate again, so that the first driving chamber is connected to the passage between the oil tank in reverse, the stored energy of the driving spring is released, and the piston is pushed to move in the direction of the first driving chamber, and the hydraulic oil in the first driving chamber flows into the oil tank and the second driving chamber through the reversely connected passage; After the piston moves to the end of the stroke of the first drive chamber, the step of controlling the hydraulic pump to start and the electric control reversing valve to operate is returned to make the passage between the first drive chamber and the hydraulic pump communicate in the positive direction.

10. The control method of the hydraulic and spring coupled drive system according to claim 9, characterized in that: When the piston is controlled to move toward the second driving chamber, the flow rate of the hydraulic oil delivered to the first driving chamber by the hydraulic pump is controlled to control the moving speed of the piston to be a preset speed.

11. The control method of the hydraulic and spring coupled drive system according to claim 10, characterized in that: Also includes: in response to a stop position determination signal; Controlling the state of the electronically controlled reversing valve to a stop position, and all passages connected to the oil tank are in a disconnected state; In the stop position state, the first driving chamber and the second driving chamber on both sides of the piston apply the same pressure value to the piston.

Images