Quantitative pump on-off valve throttling hydraulic system and control method thereof

Abstract

The application discloses a kind of quantitative pump switch valve throttling hydraulic system and its control method including the oil outlet of quantitative pump respectively with the oil inlet of second switch valve and the oil inlet of first overflow valve communication, the A oil port of second switch valve is connected with the upper vehicle oil circuit, the B oil port of second switch valve is connected with the oil inlet of outrigger valve, the pilot oil port of first overflow valve and hydraulic oil tank are sequentially connected with first switch valve and second overflow valve, the A1 oil port of outrigger valve is connected with corresponding rod cavity, the B1 oil port of outrigger valve is connected with corresponding rodless cavity, the A2 oil port of outrigger valve is connected with corresponding rodless cavity, the B2 oil port of outrigger valve is connected with corresponding rod cavity, controller output PWM pulse signal controls second switch valve commutation, and controller outputs voltage switch signal to control first commutation valve commutation.The application realizes proportional adjustment to switch valve on the basis of not increasing cost, reduces the pressure impact caused by sudden commutation of electromagnetic switch valve in system and sudden stop of liquid flow.

Description

Technical Field

[0001] This invention relates to hydraulic buffer systems, and more particularly to a fixed displacement pump switching valve throttling hydraulic system and its control method. Background Technology

[0002] As a special type of engineering vehicle, a crane must meet both road vehicle driving requirements and lifting operation functions. To ensure stability during onboard operations, the vehicle must be supported by the outrigger hydraulic system before onboard operations begin, ensuring the tires are not under stress. Because the actions required by the system's actuators are relatively simple and the positional accuracy requirements are low, the fixed displacement pump throttling hydraulic system is widely used due to its low cost and fast response speed. Its operation methods can be divided into mechanical control and electrical control. However, the fixed displacement pump switching valve hydraulic system (electric control) is prone to pressure surges due to its fast reversing speed. This causes significant vibration in the hydraulic lines, severely impacting the customer's operating experience and the lifespan of components. The instantaneous pressure peak is much higher than the normal operating pressure, which not only damages hydraulic components and sealing devices, affecting component lifespan, but also provides a very poor operating experience for the customer. Figure 1 As shown.

[0003] Numerous companies both domestically and internationally have conducted extensive research on the causes and buffering mechanisms of hydraulic shocks. Common implementation methods include: ① Using throttle valves or damping valves to control the pressure and flow of the pilot valve, reducing the force pushing the main valve core and the switching speed, thereby reducing shock. ② Using electro-hydraulic proportional valves to achieve slow valve opening by proportionally controlling the movement of the valve core, reducing pressure shock. ③ Using accumulators to absorb hydraulic shocks and pressure pulsations generated in the system. ④ Installing balance valves or back pressure valves to suppress shock velocity by adjusting the back pressure. However, regardless of the buffering method used, it significantly increases system cost and complexity.

[0004] Therefore, it is urgent to solve the above problems. Summary of the Invention

[0005] Purpose of the invention: The first objective of this invention is to provide a quantitative pump switching valve throttling hydraulic system, which aims to achieve proportional regulation of the electromagnetic switching valve without increasing costs, thereby reducing the pressure shock caused by the sudden cessation of fluid flow due to the sudden reversal of the electromagnetic switching valve in the system.

[0006] A second objective of this invention is to provide a control method for the throttling hydraulic system of the metering pump switching valve.

[0007] Technical Solution: To achieve the above objectives, this invention discloses a fixed displacement pump switching valve throttling hydraulic system, including a hydraulic oil tank, a fixed displacement pump, a switching valve assembly, a support valve, a vertical cylinder, a horizontal cylinder, and a controller. The switching valve assembly includes a first relief valve, a first switching valve, a second relief valve, and a second switching valve. The outlet of the fixed displacement pump is connected to the inlet of the second switching valve and the inlet of the first relief valve, respectively. The outlets of the second switching valve, the first relief valve, and the support valve are connected to the hydraulic oil tank. The A port of the second switching valve is connected to the upper vehicle oil circuit, and the B port of the second switching valve... The port is connected to the oil inlet of the outrigger valve. The pilot oil port of the first relief valve is connected to the hydraulic oil tank in sequence to the first switching valve and the second relief valve. The A1 oil port of the outrigger valve is connected to the rod chamber of the vertical cylinder. The B1 oil port of the outrigger valve is connected to the rodless chamber of the vertical cylinder. The A2 oil port of the outrigger valve is connected to the rodless chamber of the horizontal cylinder. The B2 oil port of the outrigger valve is connected to the rod chamber of the horizontal cylinder. The controller is connected to the first switching valve and the second switching valve respectively. The controller outputs a PWM pulse signal to control the second switching valve to switch direction. The controller outputs a voltage switch signal to control the first switching valve to switch direction.

[0008] The outrigger valve includes a first directional valve and a second directional valve. When the first directional valve is in the left-hand position, the oil inlet of the outrigger valve is connected to the B1 port, and the oil outlet of the outrigger valve is connected to the A1 port. When the first directional valve is in the right-hand position, the oil inlet of the outrigger valve is connected to the A1 port, and the oil outlet of the outrigger valve is connected to the B1 port. When the first directional valve is in the neutral position, the A1 port, the B1 port, and the oil outlet of the outrigger valve are connected. When the second directional valve is in the left position, the oil inlet of the outrigger valve is connected to the B2 port of the outrigger valve, and the A2 port of the outrigger valve is connected to the outlet port of the outrigger valve. When the second directional valve is in the right position, the oil inlet of the outrigger valve is connected to the A2 port of the outrigger valve, and the B2 port of the outrigger valve is connected to the outlet port of the outrigger valve. When the second directional valve is in the neutral position, the A2 port, B2 port, oil inlet port, and outlet port of the outrigger valve are all closed.

[0009] Preferably, the controller is connected to the first reversing valve and the second reversing valve respectively, and the controller outputs voltage switching signals to control the reversing of the first reversing valve and the second reversing valve respectively.

[0010] Furthermore, when the second switching valve is in the left-hand working state, the oil inlet of the second switching valve is connected to the A port of the second switching valve, and the B port of the second switching valve is connected to the outlet of the second switching valve; when the second switching valve is in the right-hand working state, the oil inlet of the second switching valve is connected to the B port of the second switching valve, and the A port of the second switching valve is connected to the outlet of the second switching valve.

[0011] Furthermore, when the first switching valve is in the left-hand working state, the pilot port of the first relief valve is connected to the inlet port of the second relief valve; when the first switching valve is in the right-hand working state, the pilot port of the first relief valve is not connected to the inlet port of the second relief valve.

[0012] Preferably, the duty cycle of the PWM pulse signal is D1 = (V1 / V)×100% ~ (V2 / V)×100%, and the high-level time corresponding to the off state is Ton′1 = T×(V1 / V), Ton′ n =T×(V2 / V), where V1 is the output voltage before the switching valve starts to close, V2 is the output voltage when the switching valve is fully closed, the preset closing time of the electromagnetic switching valve ton′=n1×T, n1 is the number of times the high level is adjusted when closing, V is the total output voltage of the switching valve, and T is one modulation period.

[0013] Furthermore, the duty cycle of the PWM pulse signal is D2 = (V3 / V)×100% ~ (V4 / V)×100%, and the high-level time corresponding to the turn-on state is Ton1 = T×(V3 / V), Ton n =T×(V4 / V), where V3 is the output voltage before the switch valve starts to open, V4 is the output voltage when the switch valve is fully open, the preset opening time of the electromagnetic switch valve ton=n2×T, n2 is the number of high-level adjustments during opening, V is the total output voltage of the switch valve, and T is one modulation period.

[0014] Furthermore, the overflow pressure setting value of the first overflow valve is higher than that of the second overflow valve.

[0015] This invention discloses a control method for a quantitative pump switching valve throttling hydraulic system, comprising the following steps:

[0016] When the second switching valve, the first directional valve, and the first switching valve are all in the right-hand working state, hydraulic oil enters the rod chamber of the vertical cylinder, causing the vertical cylinder to retract inward. The system pressure is the set value of the first relief valve. At the instant the vertical cylinder retracts and stops, the right-hand solenoid Y215 of the first directional valve is immediately de-energized. Simultaneously, the solenoid Y222 of the first switching valve is continuously energized for a duration of t1s, and the system pressure decreases from the set value of the main relief valve to the set value of the second relief valve. After the right-hand solenoid Y215 of the first directional valve is de-energized for t2s, the system pressure has dropped to the set value of the second relief valve, and the solenoid Y221 of the second switching valve begins to de-energize. The controller controls the voltage of the solenoid Y221 of the second switching valve to decrease from V1 to V2 within t3s via a PWM pulse signal, and the second switching valve completes the switching.

[0017] When the second switching valve is in the right-hand working state, the first directional valve is in the left-hand working state, and the first switching valve is in the right-hand working state, hydraulic oil enters the rodless chamber of the vertical cylinder, the vertical cylinder extends outward, and the system pressure is the set value of the first relief valve; at the instant the vertical cylinder stops extending outward, the left-hand solenoid Y216 of the first directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t1s, and the system pressure decreases from the set value of the main relief valve to the set value of the second relief valve; after the left-hand solenoid Y216 of the first directional valve is de-energized for t2s, the system pressure has dropped to the set value of the second relief valve, and the solenoid Y221 of the second switching valve begins to de-energize. The controller controls the voltage of the solenoid Y221 of the second switching valve to decrease from V1 to V2 within t3s through the PWM pulse signal, and the second switching valve completes the switching.

[0018] This invention discloses a control method for a quantitative pump switching valve throttling hydraulic system, comprising the following steps:

[0019] When the second switching valve is in the right-hand working state, the second directional valve is in the right-hand working state, and the first switching valve is in the left-hand working state, hydraulic oil enters the rodless chamber of the horizontal cylinder, the horizontal cylinder extends outward, and the system pressure is the set value of the second relief valve; at the instant the horizontal cylinder stops extending outward, the right-hand solenoid Y209 of the second directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t4s, and the system pressure is saved as the set value of the second relief valve; after the right-hand solenoid Y209 of the second directional valve is de-energized for t5s, the solenoid Y221 of the second switching valve begins to de-energize, and the controller controls the voltage of the solenoid Y221 of the second switching valve to drop from V1 to V2 within t6s through the PWM pulse signal, and the second switching valve completes the switching.

[0020] When the second switching valve is in the right-hand working state, the second directional valve is in the left-hand working state, and the first switching valve is in the left-hand working state, hydraulic oil enters the rod chamber of the horizontal cylinder, the horizontal cylinder retracts inward, and the system pressure is the set value of the second relief valve; at the instant the horizontal cylinder retracts inward and stops moving, the left-hand solenoid Y210 of the second directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t4s, and the system pressure is saved as the set value of the second relief valve; after the left-hand solenoid Y210 of the second directional valve is de-energized for t5s, the solenoid Y221 of the second switching valve begins to de-energize, and the controller controls the voltage of the solenoid Y221 of the second switching valve to drop from V1 to V2 within t6s through the PWM pulse signal, and the second switching valve completes the switching.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) Based on the principle of pulse width modulation (PWM), the present invention dynamically adjusts the output voltage and combines the commutation property of the electromagnetic switch valve to achieve proportional adjustment of the electromagnetic switch valve without increasing the cost, thereby reducing the pressure shock caused by the sudden commutation of the electromagnetic switch valve in the system and the instantaneous conversion of the liquid's kinetic energy into pressure energy due to the sudden cessation of flow.

[0023] (2) In this invention, the second overflow valve has two functions: reducing the system pressure at the moment the outrigger stops extending and retracting, buffering the impact of the shock wave superimposed on the sudden reversal of the switching valve, improving the customer's operating feel and system smoothness, and increasing the service life of the components.

[0024] (3) Without increasing costs, this invention can reduce pressure shock and improve component life by non-linear switching adjustment of the electromagnetic switch valve; it can well meet the needs of outrigger operation, with simple operation, low position accuracy requirements and short working time. Attached Figure Description

[0025] Figure 1 This is a diagram showing the system pressure change in the prior art of this invention;

[0026] Figure 2 This is a hydraulic schematic diagram of the present invention;

[0027] Figure 3 This is a schematic diagram of output voltage adjustment based on PWM duty cycle in this invention;

[0028] Figure 4 This is a system pressure variation curve of the present invention;

[0029] Figure 5 This is a comparison graph of the system pressure change curves of the present invention and the prior art;

[0030] Figure 6 This is a schematic diagram of the control logic of the present invention. Figure 1 ;

[0031] Figure 7 This is a schematic diagram of the control logic of the present invention. Figure 2 ;

[0032] Figure 8 This is a schematic diagram of the digital voltage switching signal output by the controller in this invention;

[0033] Figure 9 This is a diagram showing the closing characteristics of the electromagnetic switching valve based on pulse width modulation (PWM) in this invention.

[0034] Figure 10 This is a schematic diagram of the PWM signal when the electromagnetic switch valve is closed in this invention;

[0035] Figure 11This is a schematic diagram of the voltage when the electromagnetic switch valve is closed in this invention;

[0036] Figure 12 This is a diagram showing the opening characteristics of the electromagnetic switching valve based on pulse width modulation (PWM) in this invention.

[0037] Figure 13 This is a schematic diagram of the PWM signal when the electromagnetic switch valve is turned on in this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of the parts may be exaggerated. The same reference numerals denote the same parts throughout.

[0040] Fixed displacement pump: A hydraulic pump in which the volume (displacement) of oil discharged by the pump remains constant during one revolution of the pump shaft;

[0041] Electromagnetic switching valve: This type of valve controls the opening and closing of the oil circuit by controlling the energization and de-energization of an electromagnet coil. The first switching valve 3.2, the second switching valve 3.4, the second directional valve 4.1, and the first directional valve 4.2 listed in this invention all fall under the category of electromagnetic switching valves. During normal operation, it is either fully open or fully closed, with no intermediate transition position.

[0042] Electro-proportional valves: The proportional electromagnet inside the valve actuates according to the input voltage signal, causing the valve core to shift and the valve orifice size to change. This allows for continuous and proportional control of the hydraulic system's pressure and flow, achieving precise control of the actuator's position and speed. Compared to solenoid valves, the main difference lies in the characteristics of the electromagnet, and the cost is significantly higher.

[0043] PWM (Pulse Width Modulation): Dynamically adjusts the output voltage by adjusting the pulse width / duty cycle;

[0044] Pressure shock: When a valve in a pipeline suddenly reverses its direction, the liquid's kinetic energy is instantly converted into pressure energy due to the sudden cessation of flow, resulting in a sharp increase in pressure and causing hydraulic shock.

[0045] like Figure 2As shown, the present invention discloses a quantitative pump switching valve throttling hydraulic system, comprising a hydraulic oil tank 1, a quantitative pump 2, a switching valve assembly 3, a support valve 4, a vertical cylinder 5, a horizontal cylinder 6, and a controller. The switching valve assembly 3 includes a first relief valve 3.1, a first switching valve 3.2, a second relief valve 3.3, and a second switching valve 3.4. The support valve 4 includes a first directional valve 4.2 and a second directional valve 4.1.

[0046] The outlet of the fixed displacement pump 2 is connected to the inlet of the second switching valve 3.4 and the inlet of the first relief valve 3.1, respectively. The outlets of the second switching valve 3.4, the first relief valve 3.1 and the outrigger valve 4 are connected to the hydraulic oil tank. The A port of the second switching valve 3.4 is connected to the upper vehicle oil circuit. The B port of the second switching valve 3.4 is connected to the inlet of the outrigger valve 4. The pilot port of the first relief valve 3.1 is connected to the first switching valve 3.2 and the second relief valve 3.3 in sequence between the hydraulic oil tank 1 and the first switching valve 3.2. The A1 port of the outrigger valve 4 is connected to the rod chamber of the vertical cylinder 5. The B1 port of the outrigger valve 4 is connected to the rodless chamber of the vertical cylinder 5. The A2 port of the outrigger valve 4 is connected to the rodless chamber of the horizontal cylinder 6. The B2 port of the outrigger valve 4 is connected to the rod chamber of the horizontal cylinder 6. When the first directional valve 4.2 is in the left-hand operating position, the oil inlet of the outrigger valve 4 is connected to the B1 port of the outrigger valve, and the oil outlet of the outrigger valve 4 is connected to the A1 port of the outrigger valve. When the first directional valve 4.2 is in the right-hand operating position, the oil inlet of the outrigger valve 4 is connected to the A1 port of the outrigger valve, and the oil outlet of the outrigger valve 4 is connected to the B1 port of the outrigger valve. When the first directional valve 4.2 is in the neutral-hand operating position, the A1 port and the B1 port of the outrigger valve are connected to the oil outlet of the outrigger valve, and the oil inlet of the outrigger valve is closed. When the second directional valve 4.1 is in the left position, the oil inlet of the outrigger valve 4 is connected to the B2 port of the outrigger valve, and the oil outlet of the outrigger valve 4 is connected to the outlet of the outrigger valve. When the second directional valve 4.1 is in the right position, the oil inlet of the outrigger valve 4 is connected to the A2 port of the outrigger valve, and the oil outlet of the outrigger valve 4 is connected to the outlet of the outrigger valve. When the second directional valve 4.1 is in the neutral position, the A2 port of the outrigger valve 4, the B2 port of the outrigger valve, the oil inlet of the outrigger valve, and the oil outlet of the outrigger valve are all cut off. When the second switching valve 3.4 is in the left-hand operating position, its inlet port is connected to its A port, and its B port is connected to its outlet port. When the second switching valve 3.4 is in the right-hand operating position, its inlet port is connected to its B port, and its A port is connected to its outlet port. The overflow pressure setting of the first relief valve 3.1 is higher than that of the second relief valve 3.3. When the first switching valve 3.2 is in the left-hand operating position, its pilot port is connected to the inlet port of the second relief valve 3.3. When the first switching valve 3.2 is in the right-hand operating position, its pilot port is not connected to the inlet port of the second relief valve 3.3.

[0047] In this invention, when the switching valve assembly 3 is de-energized, the metering pump 2 supplies power to the upper vehicle for rotation through the second switching valve 3.4. At this time, the electromagnet Y222 of the second switching valve 3.4 is de-energized, and the system overflow pressure is the set pressure value of the first overflow valve 3.1, which is 21 MPa. When the outriggers are in operation, the electromagnet Y221 of the second switching valve 3.4 is energized, and the oil source of the metering pump 2 enters the outrigger valve 4 through the second switching valve 3.4. The extension and retraction of the vertical cylinder 5 and the horizontal cylinder 6 are achieved by controlling the second reversing valve 4.1 and the first reversing valve 4.2. To prevent the horizontal cylinder from bending due to excessive machining deviation of the outrigger box or accidental operation of the horizontal cylinder by the customer after the vertical cylinder is extended, the electromagnet Y222 of the first switching valve 3.2 is energized when the horizontal cylinder 6 is extended. At this time, the system overflow pressure is the set pressure value of the second overflow valve 3.3, which is 6 MPa. In this invention, the second overflow valve has two functions: reducing the system pressure at the moment the outrigger extension and retraction stops, buffering the impact of the shock wave superimposed on the sudden reversal of the switching valve, improving the customer's operating feel and system smoothness, and increasing the service life of components. The electromagnets Y209 and Y210 of the second directional valve 4.1, Y215 and Y216 of the first directional valve 4.2, Y221 of the second switching valve 3.4, and Y222 of the first switching valve 3.2 are all controlled by a controller outputting a 24V voltage to regulate their energization logic. The controller directly outputs a digital voltage switch signal of 24V. When the coil is energized, the valve opens directly, with an opening time of approximately (40-80) ms. The voltage values ​​are only 0V and 24V. Figure 8 As shown. This invention is based on the principle of pulse width modulation (PWM) to dynamically adjust the output voltage, verify the opening characteristics of the electromagnetic switching valve, and find the actual voltage range of the switching valve during opening or closing. Taking the opening process as an example, the switching valve starts to close from 8V and completes full closure between 2V. By extending the dynamic adjustment time of the electromagnetic switching valve between (8-2)V, the slow commutation of the electromagnetic switching valve is achieved, such as... Figure 9 As shown.

[0048] The controller is connected to the first switching valve 3.2 and the second switching valve 3.4, respectively, and to the first directional valve 4.2 and the second directional valve 4.1, respectively. The controller outputs voltage switching signals to control the switching of the first directional valve 4.2 and the second directional valve 4.1, respectively. Specifically, the controller outputs a PWM pulse signal to control the switching of the second switching valve 3.4, and the controller outputs a voltage switching signal to control the switching of the first directional valve 3.2. The duty cycle of the PWM pulse signal is D1 = (V1 / V)×100% ~ (V2 / V)×100%, and the high-level time when it is off corresponds to Ton′1 = T×(V1 / V), Ton′... n=T×(V2 / V), where V1 is the output voltage before the switching valve begins to close, V2 is the output voltage when the switching valve is fully closed, the preset closing time of the electromagnetic switching valve ton′=n1×T, n1 is the number of high-level adjustments during closing, V is the total output voltage of the switching valve, and T is one modulation cycle. The duty cycle of the PWM pulse signal D2=(V3 / V)×100%~(V4 / V)×100%, the high-level time corresponding to the opening Ton1=T×(V3 / V), Ton n =T×(V4 / V), where V3 is the output voltage before the switch valve starts to open, V4 is the output voltage when the switch valve is fully open, the preset opening time of the electromagnetic switch valve ton=n2×T, n2 is the number of high-level adjustments during opening, V is the total output voltage of the switch valve, and T is one modulation period.

[0049] The frequency of PWM is constant, meaning T is a fixed value. Voltage regulation is achieved by changing its duty cycle (Ton′ / T). Taking a total output voltage of 24V as an example, a 100% duty cycle results in an output voltage of 24V, while a 0% duty cycle results in an output voltage of 0V. Therefore, the duty cycle corresponding to an output of (8-2)V is (8 / 24)×100% to (2 / 24)×100%. In the corresponding diagram below, Ton′1=T×(8 / 24), Ton′... n =T×(2 / 24). To prolong the closing time of solenoid valve Y221, by reducing (Ton′) n -Ton′ n-1 The value of ) satisfies the preset closing time ton′=n1×T of the electromagnetic switch valve, where n1 is the number of times the high-level adjustment is performed during closing, such as Figure 10 and Figure 11 .

[0050] The system pipeline vibration of this invention mainly occurs at the moment the vertical / horizontal cylinder stops extending or retracting. This is because at this moment, a closed space is momentarily formed between the outrigger 4 and the second switching valve 3.4, preventing pressure release and causing pipeline vibration. Since the moment the vertical / horizontal cylinder extends or retracts involves the input of oil into the large and small chambers of the vertical / horizontal cylinder, the pipeline vibration is not significant.

[0051] When this invention is used in other working scenarios where a slow reversal is required upon startup, the analysis is as follows:

[0052] Taking the opening process as an example, the second switching valve 3.4 starts opening from 12V and completes full opening between 12V and 18V. By extending the dynamic adjustment time of the solenoid valve between (12-18)V, the solenoid valve achieves slow reversal. Figure 12 As shown.

[0053] The frequency of PWM is constant, meaning T is a fixed value. Voltage regulation is achieved by changing its duty cycle (Ton / T). Taking a total output voltage of 24V as an example, a 100% duty cycle results in an output voltage of 24V, while a 0% duty cycle results in an output voltage of 0V. Therefore, the duty cycle corresponding to an output of (12-18)V is (12 / 24)×100% to (18 / 24)×100%. In the corresponding diagram below, Ton1 = T×(12 / 24), Ton... n =T×(18 / 24). To prolong the opening time of solenoid valve Y221, by reducing (Ton n -Ton n-1 The value of ) satisfies the preset opening time of the electromagnetic switch valve ton=n2×T, where n2 is the number of times the high level is adjusted during opening, such as Figure 13 As shown.

[0054] Based on the test characteristics of the second switching valve 3.4, it is known that, except for its fully open and fully closed states, it is energized and de-energized by 24V. During its switching process, the valve core moves non-linearly with voltage changes: when the voltage drops from around 12V, the valve core begins to switch to the right, and when the voltage reaches around 17V, the overall switching of the second switching valve 3.4 is completed. During the de-energization process of the electromagnet, when the voltage drops to 7V, the second switching valve 3.4 begins to switch to the left, and when it drops to 3V, the overall switching of the second switching valve 3.4 is completed. By adjusting the PWM duty cycle by the controller, the voltage of the non-proportional electromagnet of the second switching valve 3.4 can be regulated, such as... Figure 3 As shown, when electromagnet Y221 is energized, its rise time from 12V to 18V is set to 1 second; when electromagnet Y221 is de-energized, its fall time from 8V to 2V is set to 1 second. Simultaneously, the transition position function of the second switching valve 3.4 is designed as an H-type. Although the relationship between its energized voltage and the valve core movement speed is non-linear, it increases the switching valve's reversing time and reduces the main valve core's reversing speed, thereby reducing pressure surges.

[0055] The second relief valve 3.3 serves a dual purpose, reducing system pressure during the moment of switching valve de-energization: Taking the sudden stop of the vertical cylinder 5 retracting inward as an example: At the moment of stopping, solenoid Y215 immediately de-energizes, preventing the cylinder from continuing to extend outward when the operation stops. Simultaneously, Y222 is energized, with an energization time set to 2.5s (adjustable). At this time, the system pressure decreases from the first relief valve setting value of 21MPa to the second relief valve setting value of 6MPa. One second after solenoid Y215 de-energizes, the system pressure has dropped to 6MPa. Y221 then de-energizes. The controller adjusts the PWM duty cycle and voltage decay frequency, setting the 8V to 2V drop time to 1s, completing the dual coordination of pressure overriding control and slow valve core reversal, reducing the pressure impact during the switching valve reversal. The system pressure change curve and comparison with existing technical solutions are shown below. Figure 4 and Figure 5.

[0056] like Figure 6 As shown, the present invention provides a control method for a fixed displacement pump switching valve throttling hydraulic system, comprising the following steps:

[0057] When the second switching valve, the first directional valve, and the first switching valve are all in the right-hand working state, hydraulic oil enters the rod chamber of the vertical cylinder, causing the vertical cylinder to retract inward. The system pressure is the set value of the first relief valve. At the instant the vertical cylinder retracts and stops, the right-hand solenoid Y215 of the first directional valve is immediately de-energized. Simultaneously, the solenoid Y222 of the first switching valve is continuously energized for a duration of t1s, and the system pressure decreases from the set value of the main relief valve to the set value of the second relief valve. After the right-hand solenoid Y215 of the first directional valve is de-energized for t2s, the system pressure has dropped to the set value of the second relief valve, and the solenoid Y221 of the second switching valve begins to de-energize. The controller controls the voltage of the solenoid Y221 of the second switching valve to decrease from V1 to V2 within t3s via a PWM pulse signal, and the second switching valve completes the switching.

[0058] When the second switching valve is in the right-hand working state, the first directional valve is in the left-hand working state, and the first switching valve is in the right-hand working state, hydraulic oil enters the rodless chamber of the vertical cylinder, the vertical cylinder extends outward, and the system pressure is the set value of the first relief valve; at the instant the vertical cylinder stops extending outward, the left-hand solenoid Y216 of the first directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t1s, and the system pressure decreases from the set value of the main relief valve to the set value of the second relief valve; after the left-hand solenoid Y216 of the first directional valve is de-energized for t2s, the system pressure has dropped to the set value of the second relief valve, and the solenoid Y221 of the second switching valve begins to de-energize. The controller controls the voltage of the solenoid Y221 of the second switching valve to decrease from V1 to V2 within t3s through the PWM pulse signal, and the second switching valve completes the switching.

[0059] like Figure 7 As shown, the present invention provides a control method for a fixed displacement pump switching valve throttling hydraulic system, comprising the following steps:

[0060] When the second switching valve is in the right-hand working state, the second directional valve is in the right-hand working state, and the first switching valve is in the left-hand working state, hydraulic oil enters the rodless chamber of the horizontal cylinder, the horizontal cylinder extends outward, and the system pressure is the set value of the second relief valve; at the instant the horizontal cylinder stops extending outward, the right-hand solenoid Y209 of the second directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t4s, and the system pressure is saved as the set value of the second relief valve; after the right-hand solenoid Y209 of the second directional valve is de-energized for t5s, the solenoid Y221 of the second switching valve begins to de-energize, and the controller controls the voltage of the solenoid Y221 of the second switching valve to drop from V1 to V2 within t6s through the PWM pulse signal, and the second switching valve completes the switching.

[0061] When the second switching valve is in the right-hand working state, the second directional valve is in the left-hand working state, and the first switching valve is in the left-hand working state, hydraulic oil enters the rod chamber of the horizontal cylinder, the horizontal cylinder retracts inward, and the system pressure is the set value of the second relief valve; at the instant the horizontal cylinder retracts inward and stops moving, the left-hand solenoid Y210 of the second directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t4s, and the system pressure is saved as the set value of the second relief valve; after the left-hand solenoid Y210 of the second directional valve is de-energized for t5s, the solenoid Y221 of the second switching valve begins to de-energize, and the controller controls the voltage of the solenoid Y221 of the second switching valve to drop from V1 to V2 within t6s through the PWM pulse signal, and the second switching valve completes the switching. This invention is based on the principle of pulse width modulation (PWM) to dynamically adjust the output voltage. Combined with the commutation property of the electromagnetic switch valve, it achieves proportional-like regulation of the electromagnetic switch valve without increasing costs. This reduces the pressure shock caused by the sudden commutation of the electromagnetic switch valve in the system, which results in the instantaneous conversion of the liquid's kinetic energy into pressure energy due to the sudden cessation of flow. This invention, without increasing costs, achieves the effect of reducing pressure shock and improving component lifespan through non-linear commutation regulation of the electromagnetic switch valve. It can well meet the needs of outrigger operation, with simple operation, low positional accuracy requirements, and short working time.

Claims

1. A quantitative pump switching valve throttling hydraulic system, characterized in that, The system includes a hydraulic oil tank (1), a fixed displacement pump (2), a switching valve assembly (3), a support valve (4), a vertical cylinder (5), a horizontal cylinder (6), and a controller. The switching valve assembly (3) includes a first relief valve (3.1), a first switching valve (3.2), a second relief valve (3.3), and a second switching valve (3.4). The outlet of the fixed displacement pump (2) is connected to the inlet of the second switching valve (3.4) and the inlet of the first relief valve (3.1), respectively. The outlets of the second switching valve (3.4), the first relief valve (3.1), and the support valve (4) are connected to the hydraulic oil tank. The A port of the second switching valve (3.4) is connected to the upper vehicle oil circuit, and the B port of the second switching valve (3.4) is connected to the inlet of the support valve (4). The pilot port of the first relief valve (3.1) is connected to the hydraulic oil tank (1) in sequence with the first switching valve (3.2) and the second relief valve (3.3). The A1 port of the outrigger valve (4) is connected to the rod chamber of the vertical cylinder (5). The B1 port of the outrigger valve (4) is connected to the rodless chamber of the vertical cylinder (5). The A2 port of the outrigger valve (4) is connected to the rodless chamber of the horizontal cylinder (6). The B2 port of the outrigger valve (4) is connected to the rod chamber of the horizontal cylinder (6). The controller is connected to the first switching valve (3.2) and the second switching valve (3.4) respectively. The controller outputs a PWM pulse signal to control the second switching valve (3.4) to switch. The controller outputs a voltage switch signal to control the first switching valve (3.2) to switch. The first switching valve (3.2) and the second switching valve (3.4) are both electromagnetic switching valves. The duty cycle of the PWM pulse signal is D1 = (V1 / V) × 100% ~ (V2 / V) × 100%. The high-level time when closed is Ton´1 = T × (V1 / V). n =T×(V2 / V), where V1 is the output voltage before the switching valve starts to close, V2 is the output voltage when the switching valve is fully closed, the preset closing time of the electromagnetic switching valve ton´=n1×T, n1 is the number of high-level adjustments when closing, V is the total output voltage of the switching valve, and T is one modulation period; The duty cycle of the PWM pulse signal is D2 = (V3 / V) × 100% ~ (V4 / V) × 100%, and the high-level time Ton1 when it is turned on is T × (V3 / V). n =T×(V4 / V), where V3 is the output voltage before the switch valve starts to open, V4 is the output voltage when the switch valve is fully open, the preset opening time of the electromagnetic switch valve ton=n2×T, n2 is the number of high-level adjustments during opening, V is the total output voltage of the switch valve, and T is one modulation period.

2. The quantitative pump switching valve throttling hydraulic system according to claim 1, characterized in that: The outrigger valve (4) includes a first directional valve (4.2) and a second directional valve (4.1). When the first directional valve (4.2) is in the left-hand working state, the oil inlet of the outrigger valve (4) is connected to the B1 oil port of the outrigger valve, and the A1 oil port of the outrigger valve (4) is connected to the oil outlet of the outrigger valve. When the first directional valve (4.2) is in the right-hand working state, the oil inlet of the outrigger valve (4) is connected to the A1 oil port of the outrigger valve, and the B1 oil port of the outrigger valve (4) is connected to the oil outlet of the outrigger valve. When the first directional valve (4.2) is in the neutral working state, the A1 oil port and the B1 oil port of the outrigger valve (4) are connected to the oil outlet of the outrigger valve. When the second directional valve (4.1) is in the left position, the oil inlet of the outrigger valve (4) is connected to the B2 port of the outrigger valve, and the A2 port of the outrigger valve (4) is connected to the oil outlet of the outrigger valve. When the second directional valve (4.1) is in the right position, the oil inlet of the outrigger valve (4) is connected to the A2 port of the outrigger valve, and the B2 port of the outrigger valve (4) is connected to the oil outlet of the outrigger valve. When the second directional valve (4.1) is in the middle position, the A2 port of the outrigger valve (4), the B2 port of the outrigger valve, the oil inlet of the outrigger valve, and the oil outlet of the outrigger valve are all cut off.

3. The quantitative pump switching valve throttling hydraulic system according to claim 2, characterized in that: The controller is connected to the first reversing valve (4.2) and the second reversing valve (4.1) respectively. The controller outputs voltage switching signals to control the reversing of the first reversing valve (4.2) and the second reversing valve (4.1) respectively.

4. The quantitative pump switching valve throttling hydraulic system according to claim 3, characterized in that: When the second switching valve (3.4) is in the left position, the oil inlet of the second switching valve (3.4) is connected to the A port of the second switching valve, and the B port of the second switching valve is connected to the outlet of the second switching valve; when the second switching valve (3.4) is in the right position, the oil inlet of the second switching valve (3.4) is connected to the B port of the second switching valve, and the A port of the second switching valve is connected to the outlet of the second switching valve.

5. The quantitative pump switching valve throttling hydraulic system according to claim 4, characterized in that: When the first switching valve (3.2) is in the left position, the pilot port of the first relief valve (3.1) is connected to the inlet port of the second relief valve (3.3); when the first switching valve (3.2) is in the right position, the pilot port of the first relief valve (3.1) is not connected to the inlet port of the second relief valve (3.3).

6. The quantitative pump switching valve throttling hydraulic system according to claim 5, characterized in that: The overflow pressure setting value of the first overflow valve (3.1) is higher than the overflow pressure setting value of the second overflow valve (3.3).

7. A control method for a throttling hydraulic system with a fixed displacement pump switching valve according to claim 6, characterized in that, Includes the following steps: When the second switching valve, the first directional valve, and the first switching valve are all in the right-hand working state, hydraulic oil enters the rod chamber of the vertical cylinder, causing the vertical cylinder to retract inward. The system pressure is at the set value of the first relief valve. At the instant the vertical cylinder retracts and stops moving, the right-hand solenoid Y215 of the first directional valve is immediately de-energized. Simultaneously, the solenoid Y222 of the first switching valve is continuously energized for a duration of t1s, and the system pressure decreases from the set value of the first relief valve to the set value of the second relief valve. After the right-hand solenoid Y215 of the first directional valve is de-energized for t2s, the system pressure has dropped to the set value of the second relief valve, and the solenoid Y221 of the second switching valve begins to de-energize. The controller controls the voltage of the solenoid Y221 of the second switching valve to decrease from V1 to V2 within t3s via a PWM pulse signal, and the second switching valve completes the switching. When the second switching valve is in the right-hand working state, the first directional valve is in the left-hand working state, and the first switching valve is in the right-hand working state, hydraulic oil enters the rodless chamber of the vertical cylinder, the vertical cylinder extends outward, and the system pressure is the set value of the first relief valve; at the instant the vertical cylinder stops extending outward, the left-hand solenoid Y216 of the first directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t1s, and the system pressure decreases from the set value of the first relief valve to the set value of the second relief valve; after the left-hand solenoid Y216 of the first directional valve is de-energized for t2s, the system pressure has dropped to the set value of the second relief valve, and the solenoid Y221 of the second switching valve begins to de-energize. The controller controls the voltage of the solenoid Y221 of the second switching valve to decrease from V1 to V2 within t3s through the PWM pulse signal, and the second switching valve completes the switching.

8. A control method for a quantitative pump switching valve throttling hydraulic system according to claim 6, characterized in that, Includes the following steps: When the second switching valve is in the right-hand working state, the second directional valve is in the right-hand working state, and the first switching valve is in the left-hand working state, hydraulic oil enters the rodless chamber of the horizontal cylinder, the horizontal cylinder extends outward, and the system pressure is the set value of the second relief valve; at the instant the horizontal cylinder stops extending outward, the right-hand solenoid Y209 of the second directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t4s, and the system pressure is saved as the set value of the second relief valve; after the right-hand solenoid Y209 of the second directional valve is de-energized for t5s, the solenoid Y221 of the second switching valve begins to de-energize, and the controller controls the voltage of the solenoid Y221 of the second switching valve to drop from V1 to V2 within t6s through the PWM pulse signal, and the second switching valve completes the switching. When the second switching valve is in the right-hand working state, the second directional valve is in the left-hand working state, and the first switching valve is in the left-hand working state, hydraulic oil enters the rod chamber of the horizontal cylinder, the horizontal cylinder retracts inward, and the system pressure is the set value of the second relief valve; at the instant the horizontal cylinder retracts inward and stops moving, the left-hand solenoid Y210 of the second directional valve is immediately de-energized; at the same time, the solenoid Y222 of the first switching valve is continuously energized for a time set to t4s, and the system pressure is saved as the set value of the second relief valve; after the left-hand solenoid Y210 of the second directional valve is de-energized for t5s, the solenoid Y221 of the second switching valve begins to de-energize, and the controller controls the voltage of the solenoid Y221 of the second switching valve to drop from V1 to V2 within t6s through the PWM pulse signal, and the second switching valve completes the switching.

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