A hydraulic control system for boom-type engineering machinery

Abstract

After derrick hoists and puts in place, stamp fixedly derrick of derrick pin, change hydraulic oil circuit then, make hydraulic oil lead to the base hydraulic oil circuit, make the base hydraulic oil circuit breaker machine to the derrick pin respectively.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic control of engineering machinery, and more particularly to a hydraulic control system for boom-type engineering machinery. Background Art

[0002] With the rapid development of my country's economic construction, the demand for boom-type construction machinery in modern construction projects is increasing.

[0003] Common boom-type construction machinery, such as concrete pump trucks, are widely used to transport concrete on capital construction sites. They significantly reduce the arduous physical labor of concrete delivery on construction sites, improving construction progress and efficiency. Concrete pump trucks integrate the concrete pumping mechanism, boom system, and support mechanism into a vehicle chassis, making them highly efficient concrete delivery equipment that combines driving, pumping, and distribution. The boom system, which supports and moves the concrete delivery pipe, consists of multiple booms and connecting rods articulated by pins. Hydraulic cylinders installed on the corresponding booms drive the various mechanisms.

[0004] However, the arm attitude control multi-way valve of current boom-type engineering machinery is usually arranged on the lower vehicle (the boom pump truck, the entire boom can be rotated, the upper vehicle is above the rotating device, and the lower vehicle is below the rotating device), the actuator hydraulic cylinder is arranged on each boom section, and the working port pipeline is connected from the arm attitude control multi-way valve of the lower vehicle to the cylinder of each boom section. The working port pipeline increases the weight of the boom and limits the length of the boom; in addition, the long working port pipeline causes the boom movement to respond slowly.

[0005] In addition, when facing load pressure, the hydraulic system of boom-type engineering machinery needs to ensure that the maximum load pressure is transmitted to the hydraulic pump or three-way flow valve, so that the output pressure of the hydraulic system is always adapted to the maximum load. In actual implementation, the pressure of each boom hydraulic valve needs to be collected one by one, and then fed back to the hydraulic pump or three-way flow valve through the boom multi-way valve and long pipeline. Traditionally, hydraulic shuttle valves are generally used when facing load pressure selection. The basic structure of the shuttle valve is as follows Figure 1As shown, regardless of which inlet pressure is higher, A or B, the pressure at the oil outlet, LS, is guaranteed to be consistent with the higher pressure port, A or B. This is typically used to connect two main oil circuits with alternating pressures to form a control oil circuit. Its operating process is as follows: when the pressure at port A is higher, the force exerted by A on the middle steel ball (the structure is not limited to a steel ball) is greater than the force exerted by B on the middle steel ball. The steel ball is pushed toward port B, blocking the B inlet. The hydraulic oil at port A flows to port LS, at which point the pressure at port A equals the pressure at port LS. Conversely, when the pressure at port B is higher, the steel ball blocks port A, and the pressure at port LS equals the pressure at port B. In short, the pressure at port LS always equals the higher pressure between ports A and B. In actual applications, when several actuators operate simultaneously, each actuator generates an LS pressure corresponding to the load size. At this time, the hydraulic system needs to generate a pressure that at least meets the maximum load. At this time, the shuttle valve needs to compare several load pressures of different sizes, and finally only take out the maximum LS oil pressure as the LS control oil pressure of the system. If the pressure of each boom hydraulic valve is compared to finally extract the highest pressure, it is necessary to arrange the shuttle valve and external pipeline outside the hydraulic valve. The external pipeline connects the hydraulic valve of each boom. Since the pipeline is very long, the boom will also become heavy and the response speed of the actuator structure will be reduced. Therefore, such a hydraulic system still faces the problem of slow response of the boom movement. Summary of the Invention

[0006] In order to solve the problems of slow boom response and heavy boom weight in current boom-type engineering machinery, the present invention proposes a hydraulic control system for boom-type engineering machinery, which reduces the length of the pipeline, and can flexibly adapt the output pressure of the entire hydraulic system to the maximum load, and ensures that the pressure oil pipe always maintains a low standby pressure, thereby accelerating the response speed of the boom movement.

[0007] In order to achieve the above technical effects, the technical solutions of the present invention are as follows:

[0008] A hydraulic control system for boom-type engineering machinery, the system comprising: a hydraulic pump, an electric proportional pressure control valve, an electric shuttle valve unit and a plurality of boom hydraulic units;

[0009] Each boom is equipped with a boom hydraulic unit, each boom hydraulic unit is equipped with a hydraulic valve, a pressure sensor and a hydraulic cylinder, and several oil port pipelines are connected to the hydraulic valve along each boom;

[0010] In each boom hydraulic unit, the pressure sensor collects the load pressure on the boom where the hydraulic valve is located and transmits it to the electric shuttle valve unit;

[0011] The electric shuttle valve unit compares the load pressure signals received from the pressure sensors in all booms, determines the maximum load pressure signal and transmits it to the electric proportional pressure control valve;

[0012] The hydraulic pump is connected to the hydraulic oil port pipeline. The electric proportional pressure control valve controls the hydraulic oil displacement output by the hydraulic pump to the hydraulic oil port pipeline according to the maximum electric load pressure signal received. The hydraulic oil is input to the hydraulic cylinder through the hydraulic oil port pipeline and the hydraulic valve. The hydraulic cylinder moves adaptively with the maximum load pressure to control the corresponding boom.

[0013] After derrick hoists and puts in place, stamp fixedly derrick of derrick pin, then, by derrick pin, under the action of the pressure of derrick hoists and puts in place, the control cabinet that derrick of derrick pin is like this. After derrick hoists and puts in place, carry out derrick pin movement and the control cabinet that is located at derrick hoist.

[0014] Preferably, the plurality of oil port pipelines include a hydraulic oil port pipeline P, an oil return port pipeline T, and an oil unloading port pipeline L, and the hydraulic valve includes a pressure reducing valve, a first electric proportional pressure reducing valve, a second electric proportional pressure reducing valve, a pressure compensating valve, a main control valve core, a first secondary relief valve, and a second secondary relief valve;

[0015] When a single boom is in motion, the first electric proportional pressure reducing valve is energized, and the hydraulic oil port pipeline P is connected to the pressure reducing valve. The hydraulic oil in the hydraulic oil port pipeline P is reduced in pressure through the pressure reducing valve to the first electric proportional pressure reducing valve, and reaches the lower end of the main control valve core through the first electric proportional pressure reducing valve, pushing the main control valve core to move upward. At the same time, the hydraulic oil reaches the rodless chamber of the hydraulic cylinder through the pressure compensation valve and the upper position of the main control valve core, pushing the hydraulic cylinder to extend, thereby pushing the load. At the same time, the hydraulic oil in the rod chamber of the hydraulic cylinder flows to the return oil port through the upper position of the main control valve core. Pipeline T; or the second electric proportional pressure reducing valve is energized, the hydraulic oil port pipeline P is connected to the pressure reducing valve, the hydraulic oil in the hydraulic oil port pipeline P is reduced in pressure through the pressure reducing valve to the first electric proportional pressure reducing valve, and then reaches the upper end of the main control valve core through the second electric proportional pressure reducing valve, pushing the main control valve core to move downward, and the hydraulic oil simultaneously reaches the rod chamber of the hydraulic cylinder through the pressure compensation valve and the lower position of the main control valve core, pushing the hydraulic cylinder to retract, thereby pushing the load, and at the same time, the hydraulic oil in the rodless chamber of the hydraulic cylinder flows to the oil return port pipeline T through the lower position of the main control valve core;

[0016] The load pressure is fed back to the pressure compensation valve through the main control valve core. The pressure compensation valve ensures that the output flow of the hydraulic valve is always related to the opening of the main control valve core, and is transmitted to the electric shuttle valve unit through the pressure sensor, so that the hydraulic system adapts to the load pressure.

[0017] Preferably, if multiple booms move simultaneously, the pressure sensor of each boom hydraulic unit collects the load pressure signal on the boom where the hydraulic valve is located and transmits it to the electric shuttle valve unit. The electric shuttle valve unit compares the load pressure signals on multiple booms and takes the signal with the maximum load pressure for control, so that the hydraulic system adapts to the load pressure.

[0018] Preferably, the electric shuttle valve unit includes a multi-channel pressure sensor voltage value input module, a multi-channel voltage comparison maximum voltage follower circuit module, an N-segment comparator module, and a variable timer module. The pressure sensor of each arm is connected to the input end of the multi-channel pressure sensor voltage value input module, and the collected load pressure is converted into a voltage value and input into the multi-channel pressure sensor voltage value input module. The number of output ports of the multi-channel pressure sensor voltage value input module is the same as the number of pressure sensors, and the voltage value transmitted by the pressure sensor of each arm is output respectively; the multi-channel pressure sensor voltage value input module, the multi-channel voltage comparison maximum voltage follower circuit module, the N-segment comparator module, and the variable timer module are connected in sequence, and the output end of the variable timer module is connected to the electric proportional pressure control valve.

[0019] Compared with the traditional shuttle valve, this technical solution proposes the concept of an electric shuttle valve unit. Through the cooperation of a multi-channel voltage comparison maximum voltage follower circuit module, an N-segment comparator module, and a variable timer module, it avoids the design of arranging shuttle valves and external pipelines outside the hydraulic valve, reduces the weight of the boom, and thus improves the response speed of the execution structure.

[0020] Preferably, the multi-channel voltage comparison maximum voltage follower circuit module is provided with a plurality of comparison circuits and comparison output circuits arranged in sequence from top to bottom. The number of comparison circuits is the same as the number of output ports of the multi-channel pressure sensor voltage value input module. The input signal of each comparison circuit corresponds to the voltage value output by each output port of the multi-channel pressure sensor voltage value input module. Each comparison circuit includes an operational amplifier, a positive input resistor, a positive grounding capacitor, a comparator grounding capacitor, an output terminal resistor and an output diode. One end of the positive input resistor is connected to an output port of the multi-channel pressure sensor voltage value input module. The other end of the positive input resistor is connected to one end of the positive grounded capacitor and the positive input terminal of the operational amplifier, the other end of the positive grounded capacitor is grounded, the single-phase power supply voltage of the operational amplifier is +5V, the power supply that provides the +5V single-phase power supply voltage for the operational amplifier is connected to one end of the comparator grounded capacitor, the other end of the comparator grounded capacitor is grounded, the output terminal of the operational amplifier is connected to one end of the output resistor, the other end of the output resistor is connected to the anode of the output diode, and the cathode of the output diode is respectively connected to the negative input terminal of the operational amplifier of the comparator circuit in which the output diode is located and the negative input terminals of the operational amplifiers of the remaining comparator circuits;

[0021] The comparison output circuit includes a grounding resistor R and a grounding capacitor C. The cathode of the output diode is also connected to one end of the grounding resistor R, one end of the grounding capacitor C and the output end of the comparison output signal respectively. The output end of the comparison output signal outputs a maximum follower voltage U_pmax. The other end of the grounding resistor R and the other end of the grounding capacitor C are both grounded.

[0022] Preferably, the N-segment comparator module includes N voltage comparators and 2N+2 photoelectric couplers. The N-segment comparator module sets a reference voltage. The reference voltage is linearly or nonlinearly segmented into N segments according to the control characteristics of the electric proportional pressure control valve to obtain reference voltages: VREF1, VREF2, VREF3, ..., VREFN. VREF1, VREF2, VREF3, ..., VREFN are respectively used as the negative input voltages of the N voltage comparators. The positive input voltage of each of the N voltage comparators is VI, and VI = U_pmax is satisfied. The output terminal VOi of the i-th voltage comparator is connected to the 2i-1th photoelectric coupler to the 2i+2th photoelectric coupler, i = 1, 2. …,N; wherein, the output terminal VOi of the i-th voltage comparator is connected to the anode terminal "1" of the 2i-1-th photocoupler and the 2i-th photocoupler light-emitting diode, and the output terminal VOi of the i-th voltage comparator is connected to the cathode terminal "2" of the 2i+1-th photocoupler and the 2i+2-th photocoupler light-emitting diode; the first output terminal "3" of the 2i-1-th photocoupler is connected to the voltage source, the second output terminal "4" of the 2i-1-th photocoupler and the first output terminal "3" of the 2i-th photocoupler are output as the first input resistance timing parameter R555A of the variable timer module, and the output of the second output terminal "4" of the 2i-th photocoupler is output as the second input resistance timing parameter R555B of the variable timer module.

[0023] Preferably, the variable timer module adopts a 555 timer, which is provided with a "1" pin GND terminal, a "2" pin TRIG terminal, a "3" pin OUT terminal, a "4" pin power terminal, a "5" pin CONT terminal, a "6" pin THRES terminal, a "7" pin DISCH terminal, and an "8" pin VCC terminal, and is also provided with a first diode D1 and a second diode DB, wherein the first input resistor timing parameter R555A is respectively connected to the "7" pin DISCH terminal and the anode end of the first diode D1, the cathode end of the first diode D1 is respectively connected to the "6" pin THRES, the "2" pin TRIG and the anode end of the second diode DB, the second input resistor timing parameter R555B is connected to the cathode end of the second diode DB, the anode end of the second diode DB is also connected to the ground terminal GND of the "1" pin through a grounding capacitor, and the "5" pin CONT terminal is connected to the ground terminal GND through a grounding capacitor.

[0024] Preferably, when the 555 timer is just powered on, the voltage on the ground capacitor does not change suddenly, the initial level of the "2" pin TRIG end is low, the 555 timer is set, the "3" pin OUT end is high, and the ground capacitor charges the 555 timer through the first input resistor timing parameter R555A and the first diode D1. The charging time t 充 for:

[0025] t 充 =0.7*RAn*C

[0026] Wherein, RAn represents the resistance value output by the N-segment comparator module corresponding to the first input resistance timing parameter R555A; C represents the grounding capacitance;

[0027] When the charging voltage reaches the threshold voltage 2 / 3VCC, the 555 timer is reset, and the "3" pin OUT terminal is low. At this time, the grounded capacitor is discharged through the second input resistor timing parameter R555B, the first diode D1, and the internal discharge tube of the 555 timer. The discharge time t 放 for:

[0028] t 放 =0.7*RBn*C;

[0029] Wherein, RBn represents the resistance value output by the N-segment comparator module corresponding to the second input resistance timing parameter R555B.

[0030] Preferably, the oscillation period T of the 555 timer is:

[0031] T=t 充 +t 放

[0032] The duty cycle D can be solved as follows:

[0033] D=t 充 / T=RAn / (RAn+RBn)

[0034] The frequency is:

[0035] f=1 / T≈1.43 / [(RAn+RBn)*C]

[0036] Take (RAn+RBn) as a constant, keep the frequency unchanged, change the values ​​of RAn and RBn to adjust the duty cycle D, and by changing the duty cycle D, adjust the DC voltage signal output by the variable timer module.

[0037] Preferably, the pressure sensor converts the collected load pressure into a voltage value and transmits it to the multi-channel pressure sensor voltage value input module, which sequentially passes through the multi-channel voltage comparison maximum voltage follower circuit module, the N-segment comparator module, and the variable timer module. The larger the output Ran / RBn, the larger the duty cycle D, the larger the DC voltage signal received by the electric proportional pressure control valve, the larger the hydraulic oil displacement output by the hydraulic pump to the hydraulic oil port pipeline, and the greater the adaptation to the load pressure.

[0038] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0039] After derrick hoists and puts in place, stamp fixedly derrick of derrick pin, change hydraulic oil circuit then, make hydraulic oil circuit breaker machine's one. After derrick hoists and puts in place, control derrick pins and the like are located in the engine room of derrick hoist. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram showing the principle of a currently commonly used hydraulic shuttle valve proposed in the background technology of the present invention;

[0041] Figure 2 The figure shows the overall control block diagram of the hydraulic control system of the boom-type engineering machinery proposed in the first embodiment of the present invention;

[0042] Figure 3 A schematic diagram showing a hydraulic valve in a hydraulic control system for boom-type engineering machinery according to a second embodiment of the present invention;

[0043] Figure 4 A block diagram showing the overall composition of the electric shuttle valve unit proposed in Example 3 of the present invention;

[0044] Figure 5 A structural diagram showing a multi-channel voltage comparison and maximum voltage follower circuit module proposed in Example 3 of the present invention;

[0045] Figure 6 A structural diagram showing an N-segment comparator module proposed in Example 3 of the present invention;

[0046] Figure 7A structural diagram showing a variable timer module proposed in embodiment 3 of the present invention;

[0047] Figure 8 A graph showing a duty cycle curve of an equivalent PWM output proposed in Example 3 of the present invention;

[0048] Figure 9 A diagram showing the relationship between load and oil pressure proposed in Example 3 of the present invention.

[0049] Among them, 1-hydraulic pump; 2-electric proportional pressure control valve; 3-electric shuttle valve unit; 4-arm hydraulic unit; 41-hydraulic valve; 42-pressure sensor; 43-hydraulic cylinder; 411-pressure reducing valve; 412-first electric proportional pressure reducing valve; 413-second electric proportional pressure reducing valve; 414-pressure compensation valve; 415-main control valve core; 416-first and second relief valves; 417-second and second relief valves; 31-multi-channel pressure sensor voltage value input module; 32-multi-channel voltage comparison maximum voltage follower circuit module; 33-N-segment comparator module; 34-variable timer module. DETAILED DESCRIPTION

[0050] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting this patent;

[0051] In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the actual size;

[0052] It is understandable to those skilled in the art that descriptions of certain well-known contents may be omitted in the drawings.

[0053] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0054] The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting this patent;

[0055] Example 1

[0056] A hydraulic control system for boom-type engineering machinery, see Figure 2 The system includes: a hydraulic pump 1, an electric proportional pressure control valve 2, an electric shuttle valve unit 3 and several boom hydraulic units 4;

[0057] Each boom is equipped with a boom hydraulic unit 4, each boom hydraulic unit 4 is provided with a hydraulic valve 41, a pressure sensor 42 and a hydraulic cylinder 43, a number of oil port pipelines are connected to the hydraulic valve 41 along each boom, and a boom control multi-way valve is provided in the hydraulic valve 41. Compared with the traditional method, the boom control multi-way valve is split and installed near the boom cylinder of each section. In addition, Figure 2The hydraulic oil port pipeline P, oil return port pipeline T and oil unloading port pipeline L shown are connected to the hydraulic valve along each boom to reduce the pipeline length;

[0058] In this embodiment, Figure 2 For example, two boom hydraulic units equipped with two booms are listed. In each boom hydraulic unit 4, the pressure sensor 42 collects the load pressure on the boom where the hydraulic valve 41 is located and transmits it to the electric shuttle valve unit 3;

[0059] The electric shuttle valve unit 3 compares the received load pressure signals transmitted by the pressure sensors 42 in all booms, determines the maximum load pressure signal and transmits it to the electric proportional pressure control valve 2;

[0060] The hydraulic pump 1 is connected to the hydraulic oil port pipeline. The electric proportional pressure control valve 2 controls the hydraulic oil displacement output by the hydraulic pump 1 to the hydraulic oil port pipeline according to the received maximum electric load pressure signal. The hydraulic oil is input to the hydraulic cylinder 43 through the hydraulic oil port pipeline and the hydraulic valve 41. The hydraulic cylinder 43 moves adaptively with the maximum load pressure to control the corresponding boom.

[0061] Example 2

[0062] In this embodiment, the plurality of oil port pipelines include a hydraulic oil port pipeline P, an oil return port pipeline T, and an oil unloading port pipeline L, wherein the oil unloading port pipeline L is a special oil port identification letter in hydraulics and is used for unloading oil. Figure 3 The hydraulic valve 41 includes a pressure reducing valve 411, a first electric proportional pressure reducing valve 412, a second electric proportional pressure reducing valve 413, a pressure compensating valve 414, a main control valve core 415, a first secondary relief valve 416, and a second secondary relief valve 417;

[0063] When a single boom is in motion, the first electric proportional pressure reducing valve 412 is energized, and the hydraulic oil port pipeline P is connected to the pressure reducing valve 411. The hydraulic oil in the hydraulic oil port pipeline P is reduced in pressure through the pressure reducing valve 411 and flows into the first electric proportional pressure reducing valve 412. The hydraulic oil reaches the lower end of the main control valve core 415 through the first electric proportional pressure reducing valve 412, pushing the main control valve core 415 to move upward. At the same time, the hydraulic oil reaches the rodless chamber ( Figure 3 The line "A" in the middle corresponds to the cavity in the hydraulic cylinder 43), pushing the hydraulic cylinder 43 out, thereby pushing the load, and at the same time the rod cavity ( Figure 3The hydraulic oil in the cavity of the hydraulic cylinder 43 corresponding to the line where "B" is located) flows to the oil return line T through the upper position of the main control valve core 415; or the second electric proportional pressure reducing valve 413 is energized, the hydraulic oil port line P is connected to the pressure reducing valve 411, and the hydraulic oil in the hydraulic oil port line P is reduced in pressure through the pressure reducing valve 411 to the first electric proportional pressure reducing valve 413, and reaches the upper end of the main control valve core 415 through the second electric proportional pressure reducing valve 413, pushing the main control valve core 415 to move downward, and the hydraulic oil simultaneously reaches the rod cavity of the hydraulic cylinder 43 through the lower position of the pressure compensation valve 414 and the main control valve core 415, pushing the hydraulic cylinder 43 to retract, thereby pushing the load, and at the same time, the hydraulic oil in the rodless cavity of the hydraulic cylinder 43 flows to the oil return line T through the lower position of the main control valve core 415;

[0064] The load pressure is fed back to the pressure compensation valve 414 through the main control valve core 415. The pressure compensation valve 414 ensures that the output flow of the hydraulic valve 41 is always related to the opening of the main control valve core 415, and is transmitted to the electric shuttle valve unit 3 through the pressure sensor 42, so that the hydraulic system adapts to the load pressure.

[0065] If multiple booms move simultaneously, the pressure sensor 42 of each boom hydraulic unit 4 collects the load pressure signal on the boom where the hydraulic valve 41 is located and transmits it to the electric shuttle valve unit 3. The electric shuttle valve unit 3 compares the load pressure signals on the multiple booms and takes the signal with the maximum load pressure for control, so that the hydraulic system adapts to the load pressure.

[0066] Example 3

[0067] like Figure 4 As shown, the electric shuttle valve unit 3 proposed in this embodiment includes a multi-channel pressure sensor voltage value input module 31, a multi-channel voltage comparison maximum voltage follower circuit module 32, an N-segment comparator module 33, and a variable timer module 34. The pressure sensor 42 of each arm is connected to the input end of the multi-channel pressure sensor voltage value input module 31, and the collected load pressure is converted into a voltage value and input into the multi-channel pressure sensor voltage value input module 31. The number of output ports of the multi-channel pressure sensor voltage value input module 31 is the same as the number of pressure sensors 42, and the voltage value transmitted by the pressure sensor 42 of each arm is output respectively; the multi-channel pressure sensor voltage value input module 31, the multi-channel voltage comparison maximum voltage follower circuit module 32, the N-segment comparator module 33, and the variable timer module 34 are connected in sequence, and the output end of the variable timer module 34 is connected to the electric proportional pressure control valve 2.

[0068] like Figure 5As shown, the multi-channel voltage comparison maximum voltage follower circuit module 32 is provided with several comparison circuits and comparison output circuits arranged in sequence from top to bottom. The number of comparison circuits is the same as the number of output ports of the multi-channel pressure sensor voltage value input module 31. The input signal of each comparison circuit corresponds to the voltage value output by each output port of the multi-channel pressure sensor voltage value input module 31.

[0069] In this embodiment, see Figure 5 The multi-channel voltage comparison maximum voltage follower circuit module 32 includes three comparison circuits, each comparison circuit includes an operational amplifier, a positive input resistor, a positive grounding capacitor, a comparator grounding capacitor, an output resistor and an output diode, one end of the positive input resistor is connected to an output port of the multi-channel pressure sensor voltage value input module 31, the other end of the positive input resistor is connected to one end of the positive grounding capacitor and the positive input end of the operational amplifier, the other end of the positive grounding capacitor is grounded, the single-phase power supply voltage of the operational amplifier is +5V, the power supply that provides the +5V single-phase power supply voltage for the operational amplifier is connected to one end of the comparator grounding capacitor, the other end of the comparator grounding capacitor is grounded, the output end of the operational amplifier is connected to one end of the output resistor, the other end of the output resistor is connected to the anode of the output diode, and the cathode of the output diode is respectively connected to the negative input end of the operational amplifier of the comparison circuit in which it is located and the negative input ends of the operational amplifiers of the remaining comparison circuits;

[0070] See also Figure 5 , are the input signals of the positive input terminals of the three comparison circuits, respectively, input signal A voltage U A_in 、Input signal B voltage U B_in And input signal C voltage U C_in The comparison output circuit includes a grounding resistor R and a grounding capacitor C. The cathode of the output diode is also connected to one end of the grounding resistor R, one end of the grounding capacitor C and the output end of the comparison output signal. The output end of the comparison output signal outputs the maximum follower voltage U_pmax. The other end of the grounding resistor R and the other end of the grounding capacitor C are both grounded. When the voltage values ​​of multiple pressure sensors are input, the maximum value of the multiple voltage values ​​is compared and output; suppose the input signal U A_in >U B_in >U C_in , op amp U1A works in the linear region, can conduct diode D1A, and has closed-loop negative feedback. The negative input voltage of the other two op amps is U A_out For op amps U1B and U1C, the negative voltage is higher than the positive voltage. Since the circuit is not powered by positive and negative power supplies, but by a single power supply, the actual U B_out , U C_out The output is 0, and the operational amplifier proportional coefficient is set to 1, so the maximum voltage following U_pmax=UA_out =U A_in .

[0071] In this embodiment, the N-segment comparator module 33 includes N voltage comparators and 2N+2 photoelectric couplers. In this embodiment, the N-segment comparator module sets a reference voltage. According to the control characteristics of the electric proportional pressure control valve 2, the reference voltage is divided into N segments in a linear or nonlinear manner to obtain reference voltages: VREF1, VREF2, VREF3, ..., VREFN. Figure 6 As shown, VREF1, VREF2, VREF3, ..., VREFN are respectively used as the negative input voltages of N voltage comparators, and the positive input voltage of each voltage comparator in the N voltage comparators is VI, and satisfies VI = U_pmax, the output terminal VOi of the i-th voltage comparator is connected to the 2i-1th photoelectric coupler to the 2i+2th photoelectric coupler, i = 1, 2, ..., N; wherein, the output terminal VOi of the i-th voltage comparator is connected to the 2i-1th photoelectric coupler and the anode terminal "1" of the light emitting diode of the 2i photoelectric coupler, and the output terminal VOi of the i-th voltage comparator is connected to the anode terminal "1" of the light emitting diode of the 2i-1th photoelectric coupler. The output terminal VOi of each voltage comparator is connected to the cathode end "2" pin of the light emitting diode of the 2i+1th photoelectric coupler and the 2i+2th photoelectric coupler; the first output terminal "3" pin of the 2i-1th photoelectric coupler is connected to a voltage source; the output of the second output terminal "4" pin of the 2i-1th photoelectric coupler and the first output terminal "3" pin of the 2ith photoelectric coupler is a first input resistance timing parameter R555A of a variable timer module (34); the output of the second output terminal "4" pin of the 2ith photoelectric coupler is a second input resistance timing parameter R555B of the variable timer module 34.

[0072] In this embodiment, the reference voltage is divided into N segments according to the control characteristics of the rear-end voltage proportional valve, where N is set as needed and N>=2; the N segments can be linear or nonlinear, such as a group of reference voltages N=8, namely VREF1=4.5V, VREF2=4V, VREF3=3.5V, VREF4=3V, VREF5=2.5V, VREF6=2V, VREF7=1.5V, VREF8=1V, and the reference voltages are compared with the maximum voltage U_pmax respectively.

[0073] like Figure 6 As shown, let VI = U_pmax, and compare it with each reference voltage to see which level the voltage falls into. In the above example, VREF1>VREF2>VREF3>VREF4>VREF5>VREF6>VREF7>VREF8, see Figure 6, IC1, IC2,... IC2n+1 are optoelectronic couplers. If VI > VREF1, only the light-emitting diodes of IC1 and IC2 can conduct because at this time Vo1, Vo2,... Von all output high levels. The first and second pins of other IC3, IC4,... IC2n+2 are all at high levels, without a voltage difference, so the light-emitting diodes cannot conduct. However, the first pin of IC1 and IC2 is high and the second pin is low, so the light-emitting diodes can conduct. Under the optoelectronic conversion effect, the third and fourth pins of IC1 and IC2 are conducted, and the resistors RA1 and RB1 are selected as the input of the backend timing parameters. Similarly, if VI > VREF2 and VI < VREF1, the resistors RA2 and RB2 are selected as the input of the backend timing parameters because except for the first and second pins of the IC corresponding to the smaller voltage level being all high and without a voltage difference and not conducting. At this time, the first and second pins of IC1 and IC2 are both low and there is also no voltage difference and they do not conduct. Similarly, when VI > VREFn and VI < VREFn-1, only the resistors RAn and RBn are selected as the input of the backend timing parameters. The N-stage comparator and the optoelectronic coupler can select different time parameters according to the different levels where the maximum voltage at the front end falls. Here, the larger U_pmax is, the larger the value of the time parameter RAn / RBn to be selected (n = 1, 2,.. N), and the actual value is determined according to the pressure electro-hydraulic proportional valve at the backend; and N+1 groups of results can be selected, and the N+1th group is the selection result when all are not greater than

[0074] As Figure 7 shown, the variable timer module 34 uses a 555 timer. The 555 timer has a "1" pin GND terminal, a "2" pin TRIG terminal, a "3" pin OUT terminal, a "4" pin power supply terminal, a "5" pin CONT terminal, a "6" pin THRES terminal, a "7" pin DISCH terminal, an "8" pin VCC terminal, and also has a first diode D1 and a second diode DB. Among them, the first input resistance timing parameter R555A is respectively connected to the "7" pin DISCH terminal and the anode terminal of the first diode D1. The cathode terminal of the first diode D1 is respectively connected to the "6" pin THRES, the "2" pin TRIG, and the anode terminal of the second diode DB. The second input resistance timing parameter R555B is connected to the cathode terminal of the second diode DB. The anode terminal of the second diode DB is also connected to the GND terminal of the "1" pin through a grounding capacitor, and the "5" pin CONT terminal is connected to the grounding terminal GND through a grounding capacitor.

[0075] The 555 timer is a mature integrated circuit. Using the unidirectional conductivity of the diodes D1 and DB, the charging and discharging circuits of the capacitor C are separated, and the duty cycle of the timer is adjusted by changing the values of RA and RB connected to R555A and R555B. The function table of the 555 timer is shown in Table 1.

[0076] Table 1

[0077]

[0078] When V6 <V 555A 、V2 <V 555B OUTV3 is high level; when V6>V 555A 、V2>V 555B OUTV3 is low level. When V6 <V 555A 、V2>V 555B OUTV3 remains unchanged.

[0079] When the 555 timer is just powered on, the voltage on the ground capacitor does not change suddenly. The initial level of the "2" pin TRIG terminal is low, the 555 timer is set, and the "3" pin OUT terminal is high. The ground capacitor charges the 555 timer through the first input resistor timing parameter R555A and the first diode D1. The charging time t 充 for:

[0080] t 充 =0.7*RAn*C

[0081] Wherein, RAn represents the resistance value output by the N-segment comparator module corresponding to the first input resistance timing parameter R555A; C represents the grounding capacitance;

[0082] When the charging voltage reaches the threshold voltage 2 / 3VCC, the 555 timer is reset, and the "3" pin OUT terminal is low. At this time, the grounded capacitor is discharged through the second input resistor timing parameter R555B, the first diode D1, and the internal discharge tube of the 555 timer. The discharge time t 放 for:

[0083] t 放 =0.7*RBn*C;

[0084] Wherein, RBn represents the resistance value output by the N-segment comparator module corresponding to the second input resistance timing parameter R555B.

[0085] The oscillation period T of the 555 timer is:

[0086] T=t 充 +t 放

[0087] The duty cycle D can be solved as follows:

[0088] D=t 充 / T=RAn / (RAn+RBn)

[0089] The frequency is:

[0090] f=1 / T≈1.43 / [(RAn+RBn)*C]

[0091] Take (RAn+RBn) as a constant, keep the frequency unchanged, and change the values ​​of RAn and RBn to adjust the duty cycle D. By changing the duty cycle D, the DC voltage signal output by the variable timer module is adjusted. Of course, (RAn+RBn) can fluctuate within a small range, but the overall calculated frequency must meet the parameter characteristics of the back-end proportional pressure reducing valve, and the overall duty cycle must meet the output requirements of the PWM current. Figure 8 It is the current output under PWM control. In this way, the output of the variable timer network can output DC voltage signals with different duty cycles, which is equivalent to an equivalent PWM circuit. The back end is then connected to the electric proportional pressure control valve 2. The whole can be used after passing the actual engineering test.

[0092] The pressure sensor converts the collected load pressure into a voltage value and transmits it to the multi-channel pressure sensor voltage value input module 31. After selecting the circuit parameters according to the characteristics of the electric proportional pressure control valve 2, for example, the relationship diagram between a certain load and the system oil pressure is as shown in the figure below. Figure 9 As shown, the oil pressure will increase with the increase of load, but there will be a step shape. If the N division is larger, the step will be less obvious. The load pressure is converted into a voltage value and sequentially passes through the multi-channel voltage comparison maximum voltage follower circuit module 32, the N segment comparator module 33, and the variable timer module 34. The larger the output Ran / RBn is, the larger the duty cycle D is, the larger the DC voltage signal received by the electric proportional pressure control valve 2 is, and the larger the hydraulic oil displacement output by the hydraulic pump 1 to the hydraulic oil port pipeline is, and it is adaptive to the load pressure. The above can be widely used in concrete pump truck booms, fire truck pump truck booms and other booms.

[0093] The embodiments are provided merely to illustrate the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the claims.

Claims

1. A hydraulic control system for boom-type engineering machinery, characterized in that: The system comprises: a hydraulic pump (1), an electric proportional pressure control valve (2), an electric shuttle valve unit (3) and a plurality of boom hydraulic units (4); Each boom is equipped with a boom hydraulic unit (4), each boom hydraulic unit (4) is provided with a hydraulic valve (41), a pressure sensor (42) and a hydraulic cylinder (43), and a plurality of oil port pipelines are connected to the hydraulic valve (41) along each boom; In each boom hydraulic unit (4), a pressure sensor (42) collects the load pressure on the boom where the hydraulic valve (41) is located and transmits it to the electric shuttle valve unit (3); The electric shuttle valve unit (3) compares the received load pressure signals transmitted by the pressure sensors (42) in all the booms, determines the maximum load pressure signal and transmits it to the electric proportional pressure control valve (2); The hydraulic pump (1) is connected to the hydraulic oil port pipeline, and the electric proportional pressure control valve (2) controls the hydraulic oil displacement outputted from the hydraulic pump (1) to the hydraulic oil port pipeline according to the received maximum electric load pressure signal. The hydraulic oil is inputted into the hydraulic cylinder (43) through the hydraulic oil port pipeline and the hydraulic valve (41). The hydraulic cylinder (43) operates adaptively with the maximum load pressure to control the corresponding boom. The electric shuttle valve unit (3) comprises a multi-channel pressure sensor voltage value input module (31), a multi-channel voltage comparison maximum voltage follower circuit module (32), an N-segment comparator module (33), and a variable timer module (34). The pressure sensor (42) of each arm is connected to the input end of the multi-channel pressure sensor voltage value input module (31), converts the collected load pressure into a voltage value and inputs it into the multi-channel pressure sensor voltage value input module (31). The number of output ports of the multi-channel pressure sensor voltage value input module (31) is the same as the number of pressure sensors (42), and outputs the voltage value transmitted by each arm pressure sensor (42). The multi-channel pressure sensor voltage value input module (31), the multi-channel voltage comparison maximum voltage follower circuit module (32), the N-segment comparator module (33), and the variable timer module (34) are connected in sequence, and the output end of the variable timer module (34) is connected to the electric proportional pressure control valve (2).

2. The hydraulic control system for boom-type engineering machinery according to claim 1, characterized in that: The plurality of oil port pipelines include a hydraulic oil port pipeline P, an oil return port pipeline T, and an oil unloading port pipeline L. The hydraulic valve (41) includes a pressure reducing valve (411), a first electric proportional pressure reducing valve (412), a second electric proportional pressure reducing valve (413), a pressure compensating valve (414), a main control valve core (415), a first secondary relief valve (416), and a second secondary relief valve (417); When a single boom is in motion, the first electric proportional pressure reducing valve (412) is energized, and the hydraulic oil port pipeline P is connected to the pressure reducing valve (411). The hydraulic oil in the hydraulic oil port pipeline P is reduced in pressure through the pressure reducing valve (411) and enters the first electric proportional pressure reducing valve (412). The hydraulic oil reaches the lower end of the main control valve core (415) through the first electric proportional pressure reducing valve (412), pushing the main control valve core (415) to move upward. At the same time, the hydraulic oil reaches the rodless chamber of the hydraulic cylinder (43) through the pressure compensation valve (414) and the upper position of the main control valve core (415), pushing the hydraulic cylinder (43) to extend, thereby pushing the load. At the same time, the hydraulic oil in the rod chamber of the hydraulic cylinder (43) flows to the return oil port through the upper position of the main control valve core (415). Pipeline T; or the second electric proportional pressure reducing valve (413) is energized, the hydraulic oil port pipeline P is connected to the pressure reducing valve (411), the hydraulic oil in the hydraulic oil port pipeline P is reduced in pressure through the pressure reducing valve (411) to the second electric proportional pressure reducing valve (413), and reaches the upper end of the main control valve core (415) through the second electric proportional pressure reducing valve (413), pushing the main control valve core (415) to move downward, and the hydraulic oil simultaneously reaches the rod chamber of the hydraulic cylinder (43) through the pressure compensation valve (414) and the lower position of the main control valve core (415), pushing the hydraulic cylinder (43) to retract, thereby pushing the load, and at the same time, the hydraulic oil in the rodless chamber of the hydraulic cylinder (43) flows to the return oil port pipeline T through the lower position of the main control valve core (415); The load pressure is fed back to the pressure compensation valve (414) through the main control valve core (415). The pressure compensation valve (414) makes the output flow of the hydraulic valve (41) always related to the opening of the main control valve core (415). The output flow is transmitted to the electric shuttle valve unit (3) through the pressure sensor (42), so that the hydraulic system adapts to the load pressure.

3. The hydraulic control system for boom-type engineering machinery according to claim 2, characterized in that: If multiple booms are in motion simultaneously, the pressure sensor (42) of each boom hydraulic unit (4) collects the load pressure signal on the boom where the hydraulic valve (41) is located and transmits it to the electric shuttle valve unit (3). The electric shuttle valve unit (3) compares the load pressure signals on the multiple booms and uses the signal of the maximum load pressure for control, so that the hydraulic system adapts to the load pressure.

4. The hydraulic control system for boom-type engineering machinery according to claim 1, characterized in that: The multi-channel voltage comparison maximum voltage follower circuit module (32) is provided with a plurality of comparison circuits and comparison output circuits arranged in sequence from top to bottom. The number of the comparison circuits is the same as the number of output ports of the multi-channel pressure sensor voltage value input module (31). The input signal of each comparison circuit corresponds to the voltage value output by each output port of the multi-channel pressure sensor voltage value input module (31). Each comparison circuit includes an operational amplifier, a positive input resistor, a positive grounding capacitor, a comparator grounding capacitor, an output terminal resistor and an output diode. One end of the positive input resistor is connected to the positive terminal of the multi-channel pressure sensor voltage value input module (31). an output port, the other end of the positive input resistor is connected to one end of the positive grounded capacitor and the positive input terminal of the operational amplifier, the other end of the positive grounded capacitor is grounded, the single-phase power supply voltage of the operational amplifier is +5V, the power supply that provides the +5V single-phase power supply voltage for the operational amplifier is connected to one end of the comparator grounded capacitor, the other end of the comparator grounded capacitor is grounded, the output terminal of the operational amplifier is connected to one end of the output resistor, the other end of the output resistor is connected to the anode of the output diode, and the cathode of the output diode is respectively connected to the negative input terminal of the operational amplifier of the comparator circuit in which the output diode is located and the negative input terminals of the operational amplifiers of the remaining comparator circuits; The comparison output circuit includes a grounding resistor R and a grounding capacitor C. The cathode of the output diode is also connected to one end of the grounding resistor R, one end of the grounding capacitor C and the output end of the comparison output signal respectively. The output end of the comparison output signal outputs a maximum follower voltage U_pmax. The other end of the grounding resistor R and the other end of the grounding capacitor C are both grounded.

5. The hydraulic control system for boom-type engineering machinery according to claim 4, characterized in that: The N-segment comparator module (33) includes N voltage comparators and 2N+2 photoelectric couplers. The N-segment comparator module sets a reference voltage. According to the control characteristics of the electric proportional pressure control valve (2), the reference voltage is linearly or nonlinearly segmented into N segments to obtain reference voltages: VREF1, VREF2, VREF3, ..., VREFN. VREF1, VREF2, VREF3, ..., VREFN are respectively used as negative input voltages of the N voltage comparators in sequence. The positive input voltage of each voltage comparator in the N voltage comparators is VI, and satisfies VI=U_pmax. The output terminal VOi of the i-th voltage comparator is connected to the 2i-1th photoelectric coupler to the 2i+2th photoelectric coupler, i=1, 2, ..., N wherein the output terminal VOi of the i-th voltage comparator is connected to the anode terminal "1" pin of the 2i-1th photoelectric coupler and the 2i-th photoelectric coupler light emitting diode, and the output terminal VOi of the i-th voltage comparator is connected to the cathode terminal "2" pin of the 2i+1th photoelectric coupler and the 2i+2th photoelectric coupler light emitting diode; the first output terminal "3" pin of the 2i-1th photoelectric coupler is connected to a voltage source, the second output terminal "4" pin of the 2i-1th photoelectric coupler and the first output terminal "3" pin of the 2i-th photoelectric coupler output is the first input resistance timing parameter R555A of the variable timer module (34), and the second output terminal "4" pin of the 2i-th photoelectric coupler output is the second input resistance timing parameter R555B of the variable timer module (34).

6. The hydraulic control system for boom-type engineering machinery according to claim 5, characterized in that: The variable timer module (34) adopts a 555 timer. The 555 timer is provided with a "1" pin GND terminal, a "2" pin TRIG terminal, a "3" pin OUT terminal, a "4" pin power terminal, a "5" pin CONT terminal, a "6" pin THRES terminal, a "7" pin DISCH terminal, and an "8" pin VCC terminal. A first diode D1 and a second diode DB are also provided. A first input resistor timing parameter R555A is respectively connected to the "7" pin DISCH terminal and the anode terminal of the first diode D1, a cathode terminal of the first diode D1 is respectively connected to the "6" pin THRES, the "2" pin TRIG and the anode terminal of the second diode DB, a second input resistor timing parameter R555B is connected to the cathode terminal of the second diode DB, an anode terminal of the second diode DB is further connected to the ground terminal GND of the "1" pin via a grounding capacitor, and a "5" pin CONT terminal is connected to the ground terminal GND via a grounding capacitor.

7. The hydraulic control system for boom-type engineering machinery according to claim 6, characterized in that: When the 555 timer is just powered on, the voltage on the ground capacitor does not change suddenly. The initial level of the "2" pin TRIG terminal is low, the 555 timer is set, and the "3" pin OUT terminal is high. The ground capacitor charges the 555 timer through the first input resistor timing parameter R555A and the first diode D1. The charging time t 充 for: t 充 =0.7*RAn*C Wherein, RAn represents the resistance value output by the N-segment comparator module corresponding to the first input resistance timing parameter R555A; C represents the grounding capacitance; When the charging voltage reaches the threshold voltage 2 / 3VCC, the 555 timer is reset and the "3" pin OUT terminal is low. At this time, the grounded capacitor is discharged through the second input resistor timing parameter R555B, the first diode D1, and the internal discharge tube of the 555 timer. The discharge time is t 放 for: t 放 =0.7*RBn*C; Wherein, RBn represents the resistance value output by the N-segment comparator module corresponding to the second input resistance timing parameter R555B.

8. The hydraulic control system for boom-type engineering machinery according to claim 7, characterized in that: The oscillation period T of the 555 timer is: T=t 充 +t 放 The duty cycle D can be solved as follows: D=t 充 / T=RAn / (RAn+RBn) The frequency is: f=1 / T≈1.43 / [(RAn+RBn)*C] Take (RAn+RBn) as a constant, keep the frequency unchanged, change the values ​​of RAn and RBn to adjust the duty cycle D, and by changing the duty cycle D, adjust the DC voltage signal output by the variable timer module.

9. The hydraulic control system for boom-type engineering machinery according to claim 8, characterized in that: The pressure sensor converts the collected load pressure into a voltage value and transmits it to a multi-channel pressure sensor voltage value input module (31). After the multi-channel voltage comparison maximum voltage follower circuit module (32), the N-segment comparator module (33), and the variable timer module (34), the larger the Ran / RBn output is, the larger the duty cycle D is, the larger the DC voltage signal received by the electric proportional pressure control valve (2), and the larger the hydraulic oil displacement output by the hydraulic pump (1) to the hydraulic oil port pipeline is, and the hydraulic pressure is adapted to the load pressure.

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