Hydraulic soft switching voltage transformation loop based on zero-voltage resonance principle and working method of hydraulic soft switching voltage transformation loop

Abstract

The invention provides a hydraulic soft switching voltage transformation loop based on a zero-voltage resonance principle and a working method thereof. The voltage transformation loop comprises a main voltage transformation system and an auxiliary soft switching system connected with the main voltage transformation system. The main transformation system comprises a pressure source assembly comprising a switch element, and further comprises a liquid sensing element, a one-way valve, a liquid containing element and a load end; the auxiliary soft switching system comprises a resonance unit and a one-way valve; the pressure source assembly is a high-low-pressure constant-pressure network oil source system; the switch element is a high-speed switch valve A1; the liquid sensing element is composed of a hydraulic motor B1 and an inertia flywheel B2. The liquid containing element is a bag type energy accumulator D; equipment at the load end comprises a hydraulic cylinder and a hydraulic motor, and a throttle valve E can be used as temporary replacement equipment; the resonance unit is composed of a liquid sensing element and a compression containing cavity Ch1. The circuit is simple in structure, and facilitates the improvement of the system efficiency and the improvement of the reliability of the soft switching function.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic switch voltage transformation technology (digital switch hydraulics), in particular to a hydraulic soft switch voltage transformation circuit based on the zero-pressure resonance principle and a working method thereof. Background Art

[0002] The theory behind hydraulic switching transformer technology originates from the DC / DC conversion theory within power electronics. By frequently switching on and off high-speed switching valves, it enables cyclic charging and discharging of fluid-sensing elements (inertia tubes, motors) and fluid-capacitive elements (accumulators), regulating the system's output pressure. This regulation method avoids significant throttling losses. Hydraulic switching transformers utilize modular combinations of standardized components to form circuits with various functions. Theoretically, this technology can achieve 100% transformation efficiency. Using electrical signals as switching element control signals, it can be combined with PWM and PFM control methods to facilitate more precise and diverse digital control. This technology conforms to the trend of digital intelligent control and further promotes the modernization of the hydraulic industry.

[0003] To improve the practicality of hydraulic switching conversion technology, researchers have proposed hydraulic transformer circuits and soft switching circuits by drawing on various structures of power electronics technology. For example, Chinese invention patent CN202110557022.8 discloses a hydraulic soft switching transformer for achieving pressure rise and fall and its working method. By comparing the circuit's four-switch topology, a hydraulic four-valve transformer circuit is designed to achieve the transformer function in hydraulics, and a multi-valve conduction sequence for soft switching is designed. Chinese invention patent CN202211616170.3 discloses a high-efficiency hydraulic soft switching transformer circuit based on a high-speed switching valve. Drawing on the power electronics zero-flow soft switching circuit, a hydraulic boost soft switching circuit containing an auxiliary system is designed. The conduction of the auxiliary system switch valve controls the conduction of the hydraulically controlled one-way valve to achieve the zero-flow opening condition of the main switch valve. Although the feasibility of the transformer and soft switching schemes has been verified through theoretical analysis, the existing hydraulic switch transformer schemes still have some shortcomings or other limitations, mainly manifested as follows:

[0004] (1) The realization of the voltage transformation and soft switching functions of the existing four-valve hydraulic soft-switching transformer depends on the coordination of multiple valves, which requires the design of complex valve conduction timing. Due to the interference of transient fluid power and pressure wave transmission in the hydraulic system, it is difficult for the valves to open and close in coordination according to the expected signal, which affects the voltage transformation function. In addition, the working state of the spring accumulator required is difficult to ensure.

[0005] (2) The existing soft-switching boost circuit based on adding an auxiliary circuit can improve the throttling loss caused by the switching process of the on-off valve to a certain extent, but this form of hydraulic soft switching has limitations: the auxiliary circuit requires the introduction of many additional components, and the viscous friction of the hydraulic oil plus the friction pair of the component itself causes the circuit to generate more additional losses.

[0006] (3) In the existing research on soft switching circuits, even if the switching loss problem is solved, the parameter configuration problem of soft switching implementation has not been solved. This means that when the working conditions change, it is necessary to constantly try to find the appropriate component parameters, which is not very practical in engineering. Summary of the Invention

[0007] The present invention proposes a hydraulic soft-switching voltage transformer circuit based on the zero-voltage resonance principle and a working method thereof. The circuit structure is simpler and helps to improve system efficiency and enhance the reliability of the soft-switching function.

[0008] The present invention adopts the following technical solutions.

[0009] A hydraulic soft-switching transformer circuit based on the zero-pressure resonance principle comprises a main transformer system and an auxiliary soft-switching system connected thereto; the main transformer system comprises a pressure source assembly including a switch element, a liquid sensing element, a one-way valve, a liquid capacitance element, and a load terminal;

[0010] The auxiliary soft switching system includes a resonance unit and a one-way valve;

[0011] The pressure source component is a high-low pressure constant pressure network oil source system; the switching element is a high-speed switching valve A1; the liquid sensing element is composed of a hydraulic motor B1 and an inertial flywheel B2; the liquid capacity element is a bladder accumulator D; the equipment on the load end includes a hydraulic cylinder and a hydraulic motor, and a throttle valve E can be used as a temporary replacement device; the resonance unit is composed of a liquid sensing element and a compression chamber Ch1.

[0012] The constant high-pressure source P of the high-low pressure constant-pressure network oil source system H The oil inlet of the high-speed switching valve A1 is connected, and the oil outlet of the high-speed switching valve A1 is respectively connected to the compression chamber Ch1, the oil inlet of the hydraulic motor B1 and the oil outlet of the one-way valve C1. The oil outlet of the hydraulic motor B1 is connected to the low-pressure source and one end of the load throttle valve E. When the throttle valve is used at the load end, the other end of the throttle valve E is connected to the filter accumulator D and the oil inlet of the one-way valve C1. The one-way valve C2 is anti-parallel to the high-speed switching valve A1.

[0013] The voltage conversion circuit performs cyclic charging and discharging operations of the system's energy storage liquid sensing element motor inertia flywheel combination and liquid capacitance element accumulator through frequent switching of the high-speed switching valve A1. When performing the voltage conversion function of the hydraulic constant pressure network, the maximum energy storage of the liquid sensing element is increased by changing the periodic conduction time of the high-speed switching valve A1, that is, the duty cycle of the switching valve, thereby achieving adjustment of the output pressure for different loads.

[0014] The combination of the hydraulic motor B1 and the inertial flywheel B2 reverses after fully releasing energy in a single cycle. A compression chamber Ch1 is provided in the middle of the oil circuit between the high-speed switching valve A1 and the motor B1, so that the reversed hydraulic motor B1 resonates with the chamber Ch1, driving the pressure of the chamber Ch1 to rise rapidly to balance the valve pressure difference.

[0015] The high-speed switching valve A1 is anti-parallel-connected with a one-way valve C2 for preventing excessive pressure rise in the compression chamber Ch1. The one-way valve C2 is turned on when the pressure in the chamber Ch1 is higher than the high-pressure source, thereby clamping the pressure before and after the high-speed switching valve, continuously maintaining the pressure difference at 0, eliminating the pressure-flow overlap area when the high-speed switching valve A1 is turned on, and thus achieving zero-pressure conduction of the high-speed switching valve A1.

[0016] The soft-switching voltage-transformation circuit includes three different working processes within a switching cycle T: the hydraulic motor acceleration process, the deceleration process, and the reversal process. The acceleration and deceleration processes of the hydraulic motor are used to realize the circuit voltage-transformation function, while the reversal stage of the hydraulic motor is used to solve the switching loss of the switching valve and improve the circuit voltage-transformation efficiency.

[0017] The specific actions of the soft switching transformer circuit within one switching cycle are:

[0018] Step A1: The high-speed switching valve A1 receives the PWM signal and remains on, while the one-way valves C1 and C2 remain closed. At this time, the hydraulic motor inertia flywheel B1 begins to accelerate and store energy under the action of the high and low pressure differential, and the low-pressure source PL continuously supplies pressure to the load throttle valve E.

[0019] Step A2: High-speed switching valve A1 remains closed. At this time, hydraulic motor B1 draws oil from accumulator D at the load end through check valve C1, causing the pressure difference at both ends to decelerate and release energy. Hydraulic motor B1 forms a passage with load throttle valve E and check valve C1 to supply energy to the load. Check valve C1 remains closed.

[0020] In step A3, the high-speed on-off valve A1 and the one-way valve C1 remain closed. Since the motor flywheel B1 decelerated in step A2 to supply energy to the load, the high-speed on-off valve has not yet received the on-PWM signal when it decelerates to zero. At this time, the low-pressure source PL supplies oil to the motor flywheel B1, causing it to reverse. Due to the arrangement of the rear-valve cavity Ch1, the motor flywheel B1 and the cavity Ch1 inherently resonate, causing the pressure in cavity Ch1 to rise above that of the high-pressure source. This allows the anti-parallel one-way valve of the high-speed on-off valve to maintain the pressure differential across the high-speed on-off valve A1 at zero, paving the way for the zero-pressure opening of the on-off valve in a new working cycle. This completes a full working cycle.

[0021] A working method for a hydraulic soft-switching transformer circuit based on the zero-pressure resonance principle is used for the hydraulic soft-switching transformer circuit based on the zero-pressure resonance principle described above, and is characterized in that: in the method, the minimum equivalent liquid induction value for continuous energy supply of the motor inertia flywheel combination B1, that is, the relationship between displacement and rotational inertia, is determined based on the required maximum load condition, so that the continuous energy supply state only has two stages: acceleration energy storage and deceleration energy release of the motor inertia flywheel combination B1, thereby realizing the reversal process of the hydraulic motor, that is, the intermittent energy supply state of the circuit.

[0022] The working method specifically includes the following steps:

[0023] Step S1: According to the relationship between the motor inertia flywheel combination B1 and the pressure flow of the accumulator D, determine the hydraulic pressure, flow, and accumulator flow of the high-speed switch valve during the conduction phase, and then determine the motor flow increment Δq during the charging phase. Lm1 :

[0024]

[0025]

[0026] Where, P m is the pressure on the motor, q m (t) is the change relationship of motor flow, q c (t) is the accumulator flow relationship, P H is the high pressure source pressure, P L is the low pressure source pressure, D is the duty cycle of the switch valve, T S is the valve switching cycle, L m is the equivalent fluid induction value of the motor-flywheel combination;

[0027] Step S2: According to the hydraulic motor inertia flywheel combination B1 and the pressure-flow relationship of the accumulator D, determine the hydraulic pressure, flow, and accumulator flow of the high-speed switch valve during the closing phase, and then determine the motor flow increment during the discharge phase.

[0028]

[0029] Where, P o is the output pressure, D is the duty cycle of the switch valve, T S is the valve switching cycle, L m It is the equivalent liquid sense of the motor inertia flywheel combination;

[0030] Assume that the change of the liquid flow rate in a single cycle under steady state is 0, and calculate the average value of the liquid pressure in the cycle according to steps S1 and S2:

[0031]

[0032] Obtain the steady-state output pressure of the transformer circuit in continuous working mode

[0033]

[0034] Step S3: Calculate the motor flow cycle average value based on the flow average value of the accumulator D during the switching cycle

[0035]

[0036] Where q c (t) is the accumulator flow relationship, Po is the output pressure, D is the duty cycle of the switch valve, and R is the load equivalent fluid resistance;

[0037] Step S4: The average motor flow rate obtained from Steps S1 to S3 and flow rate increase Determine the continuous / intermittent power supply mode according to the following Figure 3 The flow rate change diagram of the motor in a steady state single cycle is shown. When , it is continuous mode, otherwise it is discontinuous mode, that is:

[0038]

[0039] have to

[0040]

[0041] The working method determines the size of the compression chamber to ensure that the chamber pressure can fully resonate and rise to the high-pressure source pressure during the off-state of the switch valve. The method includes the following specific steps:

[0042] Step B1: Determine the acceleration time T within a single cycle of the motor D1 , deceleration time T D2 and reversal time T D3 :

[0043] Step B2: Determine the resonance relationship between the motor and the compression chamber and obtain the resonance time T res ;

[0044]

[0045] Among them, L m is the equivalent fluid sense of the motor inertia flywheel, C v is the equivalent liquid capacity of the compression chamber, J t is the moment of inertia, D m is the motor displacement, V volis the volume of the compression chamber, and β is the elastic modulus of the oil.

[0046] Step B3: Determine the resonance time and the motor reversal time to determine the size of the compression chamber;

[0047] Assuming that the cavity will resonate to the maximum pressure within 1 / 4 cycle, in order to achieve the conduction of the anti-parallel one-way valve, it is necessary to ensure that 1 / 4 of the resonance process can be completed within the reversal time, that is:

[0048]

[0049] Therefore, the formula for determining the size of the compression cavity is:

[0050]

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) Compared with the original multi-valve soft switching circuit that requires complex conduction timing, the present invention adopts a simpler circuit structure, realizes the voltage transformation function of the constant pressure network by switching a single valve, and introduces the resonant relationship of kinetic energy / pressure energy conversion between the liquid sensing element (motor inertia flywheel combination) and the liquid capacity element (cavity), arranges a compression cavity structure between the high-speed switching valve and the liquid sensing element, and makes the pressure of the compression cavity rise in a resonant manner during the motor reversal process, creating the opening condition of zero pressure difference before and after the valve, without considering the timing control problem of multiple components.

[0053] (2) Under the premise of introducing the resonant relationship between liquid induction and liquid capacitance elements to realize the soft switching function, the present invention utilizes the passive conduction characteristic of the one-way valve to realize the soft switching function. Since the pressure of the compression chamber rises rapidly, in order to prevent the pressure from being too high before the switch valve is turned on, resulting in a pressure difference with the high-pressure source, the one-way valve is connected in anti-parallel at the switch valve. When the chamber pressure is higher than the high-pressure source, the one-way valve is passively turned on, which clamps the zero pressure difference, ensures the zero-pressure conduction of the switch valve, and improves the system efficiency.

[0054] (3) In order to enable the circuit to achieve motor reversal under different load pressure requirements, the present invention solves the analytical expression of the liquid induction value that the motor inertia flywheel combination can achieve reversal, that is, the relationship between the motor displacement and the moment of inertia and the parameters of each component of the circuit. In addition, in order to ensure that the pressure of the compression chamber can fully resonate and rise to the high-pressure source pressure during the closing stage of the switch valve, a method for determining the size of the compression chamber is given to provide a guarantee for realizing the soft switching function. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0056] Attachment Figure 1 This is a schematic diagram of the topological structure principle of the hydraulic soft switch voltage conversion circuit according to an embodiment of the present invention;

[0057] Attachment Figure 2 Schematic diagram of different circuit working states and motor states according to an embodiment of the present invention;

[0058] Attachment Figure 3 Schematic diagram of flow rate variation in a single steady-state cycle of a continuous / intermittent motor according to an embodiment of the present invention;

[0059] Attachment Figure 4 Schematic diagram of output characteristics under different duty cycle conditions of an embodiment of the present invention;

[0060] Attachment Figure 5 3 is a schematic diagram comparing steady-state periodic switching losses with and without a soft switching loop according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0062] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0063] As shown in the figure, a hydraulic soft-switching transformer circuit based on the zero-pressure resonance principle comprises a main transformer system and an auxiliary soft-switching system connected thereto. The main transformer system comprises a pressure source assembly including a switching element, a liquid sensing element, a one-way valve, a liquid capacitance element, and a load terminal.

[0064] The auxiliary soft switching system includes a resonance unit and a one-way valve;

[0065] The pressure source component is a high-low pressure constant pressure network oil source system; the switching element is a high-speed switching valve A1; the liquid sensing element is composed of a hydraulic motor B1 and an inertial flywheel B2; the liquid capacity element is a bladder accumulator D; the equipment on the load end includes a hydraulic cylinder and a hydraulic motor, and a throttle valve E can be used as a temporary replacement device; the resonance unit is composed of a liquid sensing element and a compression chamber Ch1.

[0066] The constant high-pressure source P of the high-low pressure constant-pressure network oil source system H The oil inlet of the high-speed switching valve A1 is connected, and the oil outlet of the high-speed switching valve A1 is respectively connected to the compression chamber Ch1, the oil inlet of the hydraulic motor B1 and the oil outlet of the one-way valve C1. The oil outlet of the hydraulic motor B1 is connected to the low-pressure source and one end of the load throttle valve E. When the throttle valve is used at the load end, the other end of the throttle valve E is connected to the filter accumulator D and the oil inlet of the one-way valve C1. The one-way valve C2 is anti-parallel to the high-speed switching valve A1.

[0067] The voltage conversion circuit performs cyclic charging and discharging operations of the system's energy storage liquid sensing element motor inertia flywheel combination and liquid capacitance element accumulator through frequent switching of the high-speed switching valve A1. When performing the voltage conversion function of the hydraulic constant pressure network, the maximum energy storage of the liquid sensing element is increased by changing the periodic conduction time of the high-speed switching valve A1, that is, the duty cycle of the switching valve, thereby achieving adjustment of the output pressure for different loads.

[0068] The combination of the hydraulic motor B1 and the inertial flywheel B2 reverses after fully releasing energy in a single cycle. A compression chamber Ch1 is provided in the middle of the oil circuit between the high-speed switching valve A1 and the motor B1, so that the reversed hydraulic motor B1 resonates with the chamber Ch1, driving the pressure of the chamber Ch1 to rise rapidly to balance the valve pressure difference.

[0069] The high-speed switching valve A1 is anti-parallel-connected with a one-way valve C2 for preventing excessive pressure rise in the compression chamber Ch1. The one-way valve C2 is turned on when the pressure in the chamber Ch1 is higher than the high-pressure source, thereby clamping the pressure before and after the high-speed switching valve, continuously maintaining the pressure difference at 0, eliminating the pressure-flow overlap area when the high-speed switching valve A1 is turned on, and thus achieving zero-pressure conduction of the high-speed switching valve A1.

[0070] The soft-switching voltage-transformation circuit includes three different working processes within a switching cycle T: the hydraulic motor acceleration process, the deceleration process, and the reversal process. The acceleration and deceleration processes of the hydraulic motor are used to realize the circuit voltage-transformation function, while the reversal stage of the hydraulic motor is used to solve the switching loss of the switching valve and improve the circuit voltage-transformation efficiency.

[0071] The specific actions of the soft switching transformer circuit within one switching cycle are:

[0072] Step A1: The high-speed switching valve A1 receives the PWM signal and remains on, while the one-way valves C1 and C2 remain closed. At this time, the hydraulic motor inertia flywheel B1 begins to accelerate and store energy under the action of the high and low pressure differential, and the low-pressure source PL continuously supplies pressure to the load throttle valve E.

[0073] Step A2: High-speed switching valve A1 remains closed. At this time, hydraulic motor B1 draws oil from accumulator D at the load end through check valve C1, causing the pressure difference at both ends to decelerate and release energy. Hydraulic motor B1 forms a passage with load throttle valve E and check valve C1 to supply energy to the load. Check valve C1 remains closed.

[0074] In step A3, the high-speed on-off valve A1 and the one-way valve C1 remain closed. Since the motor flywheel B1 decelerated in step A2 to supply energy to the load, the high-speed on-off valve has not yet received the on-PWM signal when it decelerates to zero. At this time, the low-pressure source PL supplies oil to the motor flywheel B1, causing it to reverse. Due to the arrangement of the rear-valve cavity Ch1, the motor flywheel B1 and the cavity Ch1 inherently resonate, causing the pressure in cavity Ch1 to rise above that of the high-pressure source. This allows the anti-parallel one-way valve of the high-speed on-off valve to maintain the pressure differential across the high-speed on-off valve A1 at zero, paving the way for the zero-pressure opening of the on-off valve in a new working cycle. This completes a full working cycle.

[0075] A working method for a hydraulic soft-switching transformer circuit based on the zero-pressure resonance principle is used for the hydraulic soft-switching transformer circuit based on the zero-pressure resonance principle described above, and is characterized in that: in the method, the minimum equivalent liquid induction value for continuous energy supply of the motor inertia flywheel combination B1, that is, the relationship between displacement and rotational inertia, is determined based on the required maximum load condition, so that the continuous energy supply state only has two stages: acceleration energy storage and deceleration energy release of the motor inertia flywheel combination B1, thereby realizing the reversal process of the hydraulic motor, that is, the intermittent energy supply state of the circuit.

[0076] The working method specifically includes the following steps:

[0077] Step S1: According to the relationship between the motor inertia flywheel combination B1 and the pressure flow of the accumulator D, determine the hydraulic pressure, flow, and accumulator flow of the high-speed switch valve during the conduction phase, and then determine the motor flow increment Δq during the charging phase. Lm1 :

[0078]

[0079]

[0080] Where, P m is the pressure on the motor, q m (t) is the change relationship of motor flow, q c (t) is the accumulator flow relationship, P H is the high pressure source pressure, P L is the low pressure source pressure, D is the duty cycle of the switch valve, T S is the valve switching cycle, L m is the equivalent fluid induction value of the motor-flywheel combination;

[0081] Step S2: According to the hydraulic motor inertia flywheel combination B1 and the pressure-flow relationship of the accumulator D, determine the hydraulic pressure, flow, and accumulator flow of the high-speed switch valve during the closing phase, and then determine the motor flow increment during the discharge phase.

[0082]

[0083] Where, P o is the output pressure, D is the duty cycle of the switch valve, T S is the valve switching cycle, L m It is the equivalent liquid sense of the motor inertia flywheel combination;

[0084] Assume that the change of the liquid flow rate in a single cycle under steady state is 0, and calculate the average value of the liquid pressure in the cycle according to steps S1 and S2:

[0085]

[0086] Obtain the steady-state output pressure of the transformer circuit in continuous working mode

[0087]

[0088] Step S3: Calculate the motor flow cycle average value based on the flow average value of the accumulator D during the switching cycle

[0089]

[0090] Where q c (t) is the accumulator flow relationship, Po is the output pressure, D is the duty cycle of the switch valve, and R is the load equivalent fluid resistance;

[0091] Step S4: The average motor flow rate obtained from Steps S1 to S3 and flow rate increase Determine the continuous / intermittent power supply mode according to the following Figure 3 The flow rate change diagram of the motor in a steady state single cycle is shown. When , it is continuous mode, otherwise it is discontinuous mode, that is:

[0092]

[0093] have to

[0094]

[0095] The working method determines the size of the compression chamber to ensure that the chamber pressure can fully resonate and rise to the high-pressure source pressure during the off-state of the switch valve. The method includes the following specific steps:

[0096] Step B1: Determine the acceleration time T within a single cycle of the motor D1 , deceleration time T D2 and reversal time T D3 :

[0097] Step B2: Determine the resonance relationship between the motor and the compression chamber and obtain the resonance time T res ;

[0098]

[0099] Among them, L m is the equivalent fluid sense of the motor inertia flywheel, C v is the equivalent liquid capacity of the compression chamber, J t is the moment of inertia, D m is the motor displacement, V vol is the volume of the compression chamber, and β is the elastic modulus of the oil.

[0100] Step B3: Determine the resonance time and the motor reversal time to determine the size of the compression chamber;

[0101] Assuming that the cavity will resonate to the maximum pressure within 1 / 4 cycle, in order to achieve the conduction of the anti-parallel one-way valve, it is necessary to ensure that 1 / 4 of the resonance process can be completed within the reversal time, that is:

[0102]

[0103] Therefore, the formula for determining the size of the compression cavity is:

[0104]

[0105] Example:

[0106] The technical solution adopted in this embodiment is: a hydraulic soft-switching transformer circuit based on the zero-pressure resonance principle, characterized in that it includes a main transformer system and an auxiliary soft-switching system, and the hydraulic soft-switching transformer circuit includes the main transformer system and the auxiliary soft-switching system; the main transformer system includes a pressure source component, a switching element, a liquid sensing element, a one-way valve, a liquid capacity element and a load end; the auxiliary soft-switching system includes a resonance unit and a one-way valve; the pressure source component is a high-low pressure constant pressure network oil source system; the switching element is a high-speed switching valve A1; the liquid sensing element is composed of a hydraulic motor B1 and an inertial flywheel B2; the liquid capacity element is a bladder accumulator D; the load end E can be a hydraulic cylinder, a motor, etc., which is replaced by a throttle valve in this example; the resonance unit is composed of a liquid sensing element and a compression chamber Ch1.

[0107] In this embodiment, the constant high-pressure source PH is connected to the oil inlet of the high-speed switching valve A1, and the oil outlet of the high-speed switching valve A1 is respectively connected to the compression chamber Ch1, the oil inlet of the hydraulic motor B1 and the oil outlet of the one-way valve C1. The oil outlet of the hydraulic motor B1 is connected to the low-pressure source PL and one end of the load throttle valve E. The other end of the throttle valve E is connected to the filter accumulator D and the oil inlet of the one-way valve C1. The one-way valve C2 is anti-parallel to the high-speed switching valve A1.

[0108] In this embodiment, the circuit completes the cyclic charging and discharging of the system's energy storage liquid sensing element motor inertia flywheel combination and the liquid capacitance element accumulator through the frequent switching of the high-speed switching valve A1, thereby realizing the voltage transformation function of the hydraulic constant pressure network. The maximum energy storage of the liquid sensing element can be increased by changing the periodic conduction time of the high-speed switching valve A1, that is, the duty cycle of the switching valve, thereby realizing the adjustment of the output pressure of different loads.

[0109] In this embodiment, the combination of the hydraulic motor B1 and the inertial flywheel B2 will reverse after fully releasing energy in a single cycle. A compression chamber Ch1 is set between the high-speed switching valve A1 and the motor B1. The reversed hydraulic motor B1 will resonate with the chamber Ch1, and the pressure in the chamber Ch1 will rise rapidly.

[0110] In this embodiment, in order to prevent the excessive rise of the pressure in the compression chamber Ch1, a one-way valve C2 is connected in anti-parallel at the high-speed switching valve A1. The one-way valve C2 will be turned on when the pressure in the chamber Ch1 is higher than the high-pressure source, clamping the pressure before and after the high-speed switching valve, keeping the pressure difference at 0, eliminating the pressure-flow overlap area when the high-speed switching valve A1 is turned on, and thus achieving zero-pressure conduction of the high-speed switching valve A1.

[0111] like Figure 2As shown in this embodiment, the soft switching transformer circuit includes three different working processes of motor acceleration, deceleration and reversal within a switching cycle T. The method of solving the switching loss of the switching valve and improving the circuit transformer efficiency depends on the reversal stage of the motor inertia flywheel combination, which is as follows: (1) The high-speed switching valve A1 receives the PWM signal and remains on, and the one-way valves C1 and C2 remain closed. At this time, the motor inertia flywheel B1 begins to accelerate and store energy under the action of the high and low pressure difference, and the low-pressure source PL continuously supplies pressure to the load throttle valve E; (2) The high-speed switching valve A1 remains closed. At this time, the hydraulic motor B1 draws oil from the load end accumulator D through the one-way valve C1. Because of the pressure difference at both ends, it begins to decelerate and release energy. The hydraulic motor B1 and the load throttle valve E. The one-way valve C1 forms a passage to supply energy to the load, and the one-way valve C1 remains closed; (3) The high-speed switch valve A1 and the one-way valve C1 remain closed. Since the motor inertia flywheel B1 decelerates to supply energy to the load in step 2, and when it decelerates to 0, the high-speed switch valve has not yet received the on-PWM signal. At this time, the low-pressure source PL will supply oil to the motor inertia flywheel B1 to reverse it. Due to the arrangement of the valve rear cavity Ch1, the motor inertia flywheel B1 and the cavity Ch1 have inherent resonance. The pressure of the cavity Ch1 rises to a level higher than the high-pressure source, allowing the anti-parallel one-way valve of the high-speed switch valve to keep the pressure difference before and after the valve at 0, providing conditions for the zero-pressure opening of the switch valve in a new working cycle, and a complete working cycle ends.

[0112] In this embodiment, to ensure the reversal process of the hydraulic motor, that is, the intermittent energy supply state of the circuit, it is necessary to determine the minimum equivalent liquid induction value for continuous energy supply of the motor inertia flywheel combination B1 based on the required maximum load condition, that is, the relationship between the motor displacement and the moment of inertia. The continuous energy supply state only exists in two stages: acceleration energy storage and deceleration energy release of the motor inertia flywheel combination B1.

[0113] Figure 4 This is a diagram showing the output pressure regulation effect of the hydraulic soft switch voltage conversion circuit when the duty cycle varies between 0.1-0.9 under an input pressure difference of 2 MPa. It can be seen that the circuit provided by the present invention can effectively achieve a wide range of voltage conversion function.

[0114] Figure 5 The valve loss comparison between the hydraulic soft-switching transformer circuit and the non-soft-switching transformer circuit in a steady-state single cycle shows that the soft-switching transformer circuit provided by the present invention can allow the flow to pass only after the switch valve is fully turned on, effectively solving the opening loss. The presence of the rear-valve cavity prevents the pressure behind the valve from dropping immediately when the valve is turned off, reducing the closing loss. This effectively saves most of the energy for frequently switched switch valves.

[0115] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. Hydraulic soft switch voltage conversion circuit based on zero-pressure resonance principle, characterized by: The transformer circuit includes a main transformer system and an auxiliary soft switch system connected thereto; the main transformer system includes a pressure source component including a switch element, and also includes a liquid sensing element, a one-way valve, a liquid capacitance element and a load end; the auxiliary soft switch system includes a resonance unit and a one-way valve; the pressure source component is a high-low pressure constant pressure network oil source system; the switch element is a high-speed switch valve A1; the liquid sensing element is composed of a hydraulic motor B1 and an inertial flywheel B2; the liquid capacitance element is a bladder accumulator D; the equipment at the load end includes a hydraulic cylinder and a hydraulic motor, and a throttle valve E can be used as a temporary replacement device; the resonance unit is composed of a liquid sensing element and a compression chamber Ch1.

2. The hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to claim 1 is characterized in that: The constant high-pressure source P of the high-low pressure constant-pressure network oil source system H Connect the oil inlet of the high-speed switch valve A1, the oil outlet of the high-speed switch valve A1 is connected to the compression chamber Ch1, the oil inlet of the hydraulic motor B1 and the oil outlet of the one-way valve C1 respectively, the oil outlet of the hydraulic motor B1 is connected to the low-pressure source and one end of the load throttle valve E, When a throttle valve is used at the load end, the other end of the throttle valve E is connected to the filter accumulator D and to the oil inlet of the one-way valve C1, and the one-way valve C2 is anti-parallel connected to the high-speed switch valve A1.

3. The hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to claim 1 is characterized in that: The voltage conversion circuit performs the cyclic charging and discharging operations of the system energy storage liquid sensing element motor inertia flywheel combination and the liquid capacitance element accumulator through the frequent switching of the high-speed switching valve A1. When performing the voltage conversion function of the hydraulic constant pressure network, the maximum energy storage of the liquid sensing element is increased by changing the periodic conduction time of the high-speed switching valve A1, that is, the duty cycle of the switching valve, thereby realizing the adjustment of the output pressure of different loads.

4. The hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to claim 1 is characterized in that: The combination of the hydraulic motor B1 and the inertial flywheel B2 has a reverse phenomenon after completely releasing energy in a single cycle. A compression chamber Ch1 is set in the middle of the oil circuit between the high-speed switching valve A1 and the motor B1, so that the reversed hydraulic motor B1 resonates with the chamber Ch1, driving the pressure of the chamber Ch1 to rise rapidly to balance the valve pressure difference.

5. The hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to claim 1 is characterized in that: The high-speed switch valve A1 is anti-parallel connected with a one-way valve C2 for preventing the pressure of the compression chamber Ch1 from excessively rising. The one-way valve C2 is turned on when the pressure of the chamber Ch1 is higher than the high-pressure source, so as to clamp the pressure before and after the high-speed switch valve, keep the pressure difference at 0, eliminate the pressure-flow overlap area when the high-speed switch valve A1 is turned on, and thus achieve zero-pressure conduction of the high-speed switch valve A1.

6. The hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to any one of claims 1, 2, 3, 4, and 5, characterized in that: The soft switch voltage transformation circuit includes three different working processes of hydraulic motor acceleration process, deceleration process and reversal process within a switching cycle T. The acceleration process and deceleration process of the hydraulic motor are used to realize the circuit voltage transformation function, while the reversal stage of the hydraulic motor is used to solve the switching loss of the switch valve and improve the circuit voltage transformation efficiency.

7. The hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to claim 6 is characterized in that: The actions of the soft switch transformer circuit in one switching cycle are specifically as follows: Step A1: The high-speed switch valve A1 receives the PWM signal and remains on, and the one-way valves C1 and C2 remain closed. At this time, the hydraulic motor inertia flywheel B1 begins to accelerate energy storage under the action of the high and low pressure difference, and the low-pressure source PL continuously supplies pressure to the load throttle valve E; Step A2: The high-speed switch valve A1 remains closed. At this time, the hydraulic motor B1 draws oil from the accumulator D at the load end through the one-way valve C1, so that the pressure difference at both ends begins to decelerate and release energy. The hydraulic motor B1 forms a passage with the load throttle valve E and the one-way valve C1 to supply energy to the load, and the one-way valve C1 remains closed; Step A3: The high-speed switch valve A1 and the one-way valve C1 remain closed. Since the motor inertia flywheel B1 decelerates to supply energy to the load in step A2, and when it decelerates to 0, the high-speed switch valve has not received the on-PWM signal. At this time, the low-pressure source PL will supply oil to the motor inertia flywheel B1 to reverse. Due to the arrangement of the rear-valve cavity Ch1, the motor inertia flywheel B1 resonates with the cavity Ch1, and the pressure in the cavity Ch1 rises to a level higher than the high-pressure source, allowing the anti-parallel one-way valve of the high-speed switch valve to keep the pressure difference before and after the valve A1 at 0, providing conditions for the zero-pressure opening of the switch valve in a new working cycle, and a complete working cycle ends.

8. A working method of a hydraulic soft switch transformer circuit based on the zero-voltage resonance principle, used for the hydraulic soft switch transformer circuit based on the zero-voltage resonance principle as claimed in claim 6, characterized in that: In the method, the minimum equivalent liquid sense value for continuous energy supply of the motor inertia flywheel combination B1, i.e., the relationship between displacement and rotational inertia, is determined according to the required maximum load condition, so that the continuous energy supply state only has two stages, i.e., acceleration energy storage and deceleration energy release of the motor inertia flywheel combination B1, to realize the reversal process of the hydraulic motor, i.e., the intermittent energy supply state of the circuit.

9. The working method of the hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to claim 8 is characterized in that: The working method specifically includes the following steps: Step S1: According to the relationship between the motor inertia flywheel combination B1 and the pressure flow of the accumulator D, determine the liquid pressure, flow, and accumulator flow of the high-speed switch valve during the conduction stage, and then determine the motor flow increment Δq during the charging stage Lm1 : Where P m is the pressure on the motor, q m (t) is the change relationship of motor flow, q c (t) is the accumulator flow rate relationship, P H is the high pressure source pressure, P L is the low pressure source pressure, D is the duty cycle of the switch valve, T S is the valve switching cycle, L m is the equivalent fluid induction value of the motor-flywheel combination; Step S2: According to the hydraulic motor inertia flywheel combination B1 and the pressure-flow relationship of the accumulator D, determine the hydraulic pressure, flow, and accumulator flow of the high-speed switch valve during the closing stage, and then determine the motor flow increment Δq during the energy release stage Lm2 : Where P o is the output pressure, D is the duty cycle of the switch valve, T S is the valve switching cycle, L m It is the equivalent liquid sense of the motor inertia flywheel combination; Assume that the change of the liquid flow rate in a single cycle under steady state is 0, and calculate the average value of the liquid pressure in the cycle according to step S1 and step S2: p Lm >=(P H -P L )·D-Po·(1-D)=0Formula 5; The steady-state output pressure of the transformer circuit in continuous operation mode is obtained Step S3: Calculate the motor flow cycle average value based on the flow average value of the accumulator D during the switching cycle In the formula, q c (t) is the accumulator flow relationship, Po is the output pressure, D is the duty cycle of the switch valve, and R is the load equivalent fluid resistance; Step S4: The average motor flow rate obtained from Step S1 to Step S3 and flow increment Δq Lm , to judge the continuous / intermittent energy supply mode, when When , it is continuous mode, otherwise it is discontinuous mode, that is: have to 10. The working method of the hydraulic soft switch voltage conversion circuit based on the zero-voltage resonance principle according to claim 9 is characterized in that: The working method determines the size of the compression chamber to ensure that the chamber pressure can fully resonate and rise to the high pressure source pressure during the closing stage of the switch valve. The method includes the following specific steps: Step B1: Determine the acceleration time T of the motor within a single cycle D1 , deceleration time T D2 and reversal time T D3 : Step B2: Determine the resonance relationship between the motor and the compression chamber and obtain the resonance time T res ; Among them, L m is the equivalent fluid induction of the motor inertia flywheel, C v is the equivalent liquid capacity of the compression chamber, J t is the moment of inertia, D m is the motor displacement, V vol is the volume of the compression chamber, and β is the elastic modulus of the oil. Step B3: Determine the resonance time and the motor reversal time to determine the size of the compression chamber; Assuming that the cavity will resonate to the maximum pressure within 1 / 4 cycle, in order to achieve the conduction of the anti-parallel check valve, it is necessary to ensure that 1 / 4 of the resonance process can be completed within the reversal time, that is: Therefore, the formula for determining the size of the compression chamber is:

Images