A hydraulic speed control circuit and control method for a slewing system of a truck crane

Abstract

The present invention discloses a hydraulic speed control circuit and control method for a slewing system of a truck crane, comprising: a proportional control hydraulic valve, a slewing hydraulic motor, a pilot control hydraulic valve and a handle, wherein the proportional control hydraulic valve is used to switch different proportional control working positions and provide hydraulic oil of different directions and flows to the slewing hydraulic motor; the pilot control hydraulic valve receives a current signal, opens the pilot valve, and the oil pushes the main valve core to move, and the oil drives the slewing hydraulic motor to move on the vehicle; the handle is an operating end device for slewing operation, and the controller controls the high-speed switch hydraulic valve through PWM, and changes the flow of hydraulic oil flowing into the slewing hydraulic motor when the crane is in a low-speed slewing state, so as to stabilize the slewing speed. The present invention creates conditions for the response speed, is conducive to improving the stability and accuracy of the entire hydraulic system, is convenient to modify, has low cost, and has a relatively simple control process.

Description

Technical Field

[0001] The invention relates to a hydraulic speed control circuit and a control method, and in particular to a hydraulic control circuit and a control method for a slewing system of a truck crane. Background Art

[0002] The slewing speed is an important indicator of crane operation. Within a certain range, the faster the slewing speed, the higher the work efficiency. However, beyond a certain range, the faster the slewing speed, the lower the operation stability and safety. Therefore, it is necessary to keep the crane slewing speed within a certain range and be able to freely control the appropriate speed within this range as needed.

[0003] To meet the needs of low-speed operation, hydraulic pumps and hydraulic proportional valves with lower rated flow can be selected, but they cannot meet the needs of high-speed operation. To meet the needs of high-speed operation and ensure work efficiency, hydraulic pumps and hydraulic proportional valves with larger rated flow are often used. However, under the constraints of current processing technology and manufacturing costs, the hydraulic valve core of the crane is subject to nonlinear friction when working, which to a certain extent leads to discontinuity in the low-speed rotation and start-stop conditions of the crane. The handle is highly sensitive and cannot perform low-speed stable rotation operations, reducing the stability of the operation. Summary of the invention

[0004] The purpose of the present invention is to provide a hydraulic control circuit and control method for a slewing system of a truck crane, aiming at solving the problems of poor stability and control accuracy and unadjustable compensation flow rate of the separating and merging hydraulic valve in the prior art, and solving the shortcomings of the prior art.

[0005] The present invention provides the following scheme:

[0006] 1. A hydraulic speed control circuit for a slewing system of a truck crane, comprising:

[0007] A hydraulic oil tank 1, used for storing hydraulic oil;

[0008] Hydraulic pump 2, providing liquid pressure energy for the entire hydraulic system;

[0009] The proportional control hydraulic valve 4 switches different proportional control working positions and provides hydraulic oil of different directions and flows to the rotary hydraulic motor 5;

[0010] A rotary hydraulic motor 5, used to provide a rotary speed output, the rotary hydraulic motor is connected to the proportional control hydraulic valve 4;

[0011] The pilot control hydraulic valve 6 is used to provide a pilot pressure, control the direction of the hydraulic oil, and control the output flow of the proportional control hydraulic valve 4;

[0012] Handle 10, an operating end device for performing a rotation operation;

[0013] It is characterized in that it also includes a high-speed switch hydraulic valve 3 and a controller 9, the controller 9 is respectively connected to the high-speed switch hydraulic valve 3, the proportional control hydraulic valve 4 and the handle 10, the controller 9 controls the high-speed switch hydraulic valve through pulse width modulation, the high-speed switch hydraulic valve 3 is connected to the rotary hydraulic motor 5, an electromagnetic coil is arranged in the high-speed switch hydraulic valve 3, and the high-speed switch hydraulic valve 3 switches different high-speed switch working positions by gaining and losing power of the electromagnetic coil;

[0014] When the crane is in a low-speed slewing state, the controller sends a PWM signal to the electromagnetic coil in the high-speed switching hydraulic valve 3, and changes the flow rate of the hydraulic oil flowing into the slewing hydraulic motor 5 by adjusting the duty cycle of the PWM signal, thereby compensating the slewing speed and stabilizing the slewing speed of the crane in the low-speed slewing state.

[0015] Further, the high-speed switching hydraulic valve 3 is a three-phase four-way valve, the inlet of the high-speed switching hydraulic valve 3 includes a high-speed switching hydraulic valve left inlet I, a high-speed switching hydraulic valve right inlet L, the outlet of the high-speed switching hydraulic valve 3 includes a high-speed switching hydraulic valve left outlet J, a high-speed switching hydraulic valve right outlet K, the high-speed switching hydraulic valve left outlet J is connected to the proportional control hydraulic valve left outlet D of the proportional control hydraulic valve 4, and the high-speed switching hydraulic valve right outlet K is connected to the proportional control hydraulic valve right outlet F of the proportional control hydraulic valve 4;

[0016] The high-speed switch hydraulic valve 3 is an electromagnetically controlled hydraulic valve, including a first high-speed switch working position, a second high-speed switch working position, and a third high-speed switch working position. When the first electromagnetic coil Y1 is energized, the high-speed switch hydraulic valve 3 is in the first high-speed switch working position, the left inlet I of the high-speed switch hydraulic valve is connected to the left outlet J of the high-speed switch hydraulic valve, and the right inlet L of the high-speed switch hydraulic valve is connected to the right outlet K of the high-speed switch hydraulic valve; when the second electromagnetic coil Y2 is energized, the valve is in the third high-speed switch working position, the left inlet I of the high-speed switch hydraulic valve is connected to the right outlet of the high-speed switch hydraulic valve, and the right inlet L of the high-speed switch hydraulic valve is connected to the left outlet J of the high-speed switch hydraulic valve; when the first electromagnetic coil Y1 and the second electromagnetic coil Y2 are both de-energized, the high-speed switch hydraulic valve 3 is in the second high-speed switch working position, and the left inlet I of the high-speed switch hydraulic valve is not connected to the left outlet J of the high-speed switch hydraulic valve and the right outlet K of the high-speed switch hydraulic valve.

[0017] Further, the proportional control working position of the proportional control hydraulic valve 4 includes a first proportional control working position, a second proportional control working position, and a third proportional control working position. The proportional control hydraulic valve 4 is a three-phase six-way valve. The inlet of the proportional control hydraulic valve includes a left inlet A of the proportional control hydraulic valve, a middle inlet B of the proportional control hydraulic valve, and a right inlet C of the proportional control hydraulic valve. The left inlet A of the proportional control hydraulic valve and the middle inlet B of the proportional control hydraulic valve are connected to the outlet of the hydraulic pump 2. The outlet of the proportional control hydraulic valve 4 includes a left outlet D of the proportional control hydraulic valve, a middle outlet E of the proportional control hydraulic valve, and a right outlet F of the proportional control hydraulic valve.

[0018] When the proportional control hydraulic valve 4 is in the first proportional control working position, the left inlet A of the proportional control hydraulic valve is connected to the left outlet D of the proportional control hydraulic valve, the right inlet C of the proportional control hydraulic valve is connected to the right outlet F of the proportional control hydraulic valve, and the middle inlet B of the proportional control hydraulic valve and the middle outlet E of the proportional control hydraulic valve are both in the closed state;

[0019] When the proportional control hydraulic valve 4 is in the second proportional control working position, the middle inlet B of the proportional control hydraulic valve is connected to the middle outlet E of the proportional control hydraulic valve, and the left outlet D of the proportional control hydraulic valve and the right outlet F of the proportional control hydraulic valve are both connected to the right inlet C of the proportional control hydraulic valve;

[0020] When the proportional control hydraulic valve 4 is in the third proportional control working position, the left inlet A of the proportional control hydraulic valve is connected to the right outlet F of the proportional control hydraulic valve, the right inlet C of the proportional control hydraulic valve is connected to the left outlet D of the proportional control hydraulic valve, and the middle inlet B of the proportional control hydraulic valve and the middle outlet E of the proportional control hydraulic valve are both in the closed state;

[0021] The proportional control hydraulic valve left outlet D and the proportional control hydraulic valve right outlet F of the proportional control hydraulic valve 4 are connected to the first port G and the second port H of the rotary hydraulic motor 5 respectively;

[0022] The left and right ends of the proportional control hydraulic valve 4 are loading ends of the pilot pressure, wherein the left loading end is loaded with the left pilot pressure S1, and the right loading end is loaded with the right pilot pressure Sr. The above two pilot pressures are provided by the pilot control hydraulic valve 6 under the control of the handle 10.

[0023] Furthermore, it also includes an overflow valve 7, between the proportional control hydraulic valve 4 and the hydraulic pump 2, which is connected to the hydraulic oil tank 1 through the overflow valve 7 to control the hydraulic oil to flow back to the hydraulic oil tank.

[0024] Furthermore, it also includes a one-way valve 8, which is installed at the outlet of the hydraulic pump 2 to ensure the one-way flow of the hydraulic oil.

[0025] Furthermore, the inlet of the hydraulic pump 2 is connected to the hydraulic oil tank 1 for extracting the hydraulic oil in the hydraulic oil tank 1, and the outlet of the hydraulic pump 2 is respectively delivered to the inlets of the high-speed switching hydraulic valve 3 and the proportional control hydraulic valve 4.

[0026] Furthermore, the hydraulic oil tank 1 is connected to the right inlet C of the proportional control hydraulic valve and the middle outlet E of the proportional control hydraulic valve.

[0027] Furthermore, the pilot control hydraulic valve 6 is provided with a first input port T, a second input port P, a first output port P1 and a second output port P2. The pilot control hydraulic valve 6 provides a right pilot pressure Sr through the first output port P1 and a left pilot pressure Sl through the second output port P2.

[0028] Furthermore, the pilot control hydraulic valve 6 is connected to a pilot pump to obtain pressure oil from the pilot pump.

[0029] A hydraulic speed control method for a slewing system of a truck crane, specifically comprising:

[0030] Determine the signal value of the handle;

[0031] If the signal value of the handle is greater than or equal to 300, the first electromagnetic coil Y1 and the second electromagnetic coil Y2 of the high-speed switching hydraulic valve 3 shall not be energized;

[0032] If the signal value of the handle is less than 300, the operation controller outputs a PWM signal with a frequency of 100 Hz, an amplitude of 15 mA and an adjustable duty cycle, so that the amount of oil entering the rotary hydraulic motor 5 increases and the speed of the rotary hydraulic motor 5 is compensated.

[0033] Compared with the prior art, the present invention has the following advantages: when the low-speed slewing speed of the crane fluctuates, a high-speed switching hydraulic valve is added to the hydraulic compensation circuit to increase the flow into the motor so that the motor keeps rotating at a constant speed. Since low-speed slewing speed compensation is provided, the problem of discontinuity of operation under low-speed slewing and start-stop conditions caused by the nonlinear friction of the hydraulic valve core is solved. The crane can maintain continuous and smooth operation under low-speed slewing and start-stop conditions, with a low minimum stable operating speed and good stability and safety for heavy-load low-speed slewing. The high-speed switching hydraulic valve creates conditions for the response speed, which is beneficial to improving the stability and accuracy of the entire hydraulic system. It can be completed by adding a few components to the ordinary crane slewing system, which is convenient to modify, low cost, and a relatively simple control process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 The present invention is a hydraulic control circuit diagram of the automobile crane slewing system. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] A Chinese utility model patent (authorization announcement number CN201165455Y) discloses a crane slewing speed control system, which includes a hydraulic oil tank, a main hydraulic pump, a supplementary hydraulic pump, a split-and-joint flow control hydraulic valve, a proportional control hydraulic valve, a slewing hydraulic motor, and a pilot control hydraulic valve. When the crane needs to work in a low-speed slewing state, the split-and-joint flow control hydraulic valve does not provide the slewing hydraulic motor with the hydraulic oil output from the independent oil source, so that the hydraulic oil flow obtained by the slewing hydraulic motor is low, thereby reducing the slewing speed. The above-mentioned valve-controlled speed regulation method reduces the minimum stable slewing speed to a certain extent, but the problem of discontinuity of work under low-speed slewing and start-stop conditions caused by the nonlinear friction of the hydraulic valve core has not been solved, and multiple pumps need to be used, resulting in a significant increase in cost and a more complicated control process. The disadvantage of the prior art represented by the above-mentioned utility model is that flow compensation is performed by increasing the number of pumps, resulting in a significant increase in cost; the split-and-joint flow control hydraulic valve also has poor responsiveness, affecting the stability and control accuracy of the system. The split-and-joint flow control hydraulic valve cannot adjust the size of the compensation flow. The problem of discontinuity in operation under low-speed rotation and start-stop conditions caused by the nonlinear friction of the hydraulic valve core has not been solved. The operation under low-speed rotation and start-stop conditions is still discontinuous and uneven, the minimum stable working speed is high, and the stability of heavy-load low-speed rotation is poor, resulting in load swing and other problems, and poor safety. The measures taken by the existing technology can improve the above problems to a certain extent, but the cost is greatly increased and the control process is more complicated.

[0038] like Figure 1 The hydraulic speed control circuit of the slewing system of the truck crane shown includes:

[0039] A hydraulic oil tank 1, used for storing hydraulic oil;

[0040] Hydraulic pump 2, providing liquid pressure energy for the entire hydraulic system;

[0041] The connection relationship, function and purpose of the hydraulic oil tank 1 and the hydraulic pump 2 are: the inlet of the hydraulic pump 2 is connected to the hydraulic oil tank 1, which is used to extract the hydraulic oil in the hydraulic oil tank 1. The outlet of the hydraulic pump 2 is respectively delivered to the inlets of the high-speed switching hydraulic valve 3 and the proportional control hydraulic valve 4. The hydraulic oil tank 1 is connected to the right inlet C of the proportional control hydraulic valve and the middle outlet E of the proportional control hydraulic valve.

[0042] The proportional control hydraulic valve 4 switches different proportional control working positions and provides hydraulic oil in different directions and flows;

[0043] A rotary hydraulic motor 5 is used to provide a rotary speed output, and the rotary hydraulic motor 5 is connected to a proportional control hydraulic valve 4;

[0044] The pilot control hydraulic valve 6 is used to provide a pilot pressure; the pilot control hydraulic valve 6 is provided with a first input port T, a second input port P, a first output port P1 and a second output port P2. The pilot control hydraulic valve 6 provides a right pilot pressure Sr through the first output port P1 and provides a left pilot pressure Sl through the second output port P2. The two pilot pressures are switched and outputted mutually under the control of the handle 10, and increase as the tilt angle of the operating handle increases. The pilot control hydraulic valve 6 is connected to a pilot pump (not shown in the figure) to obtain the pressure oil from the pilot pump.

[0045] Handle 10, an operating end device for performing a rotation operation;

[0046] This embodiment also includes a high-speed switching hydraulic valve 3 and a controller 9. The controller 9 is respectively connected to the high-speed switching hydraulic valve 3, the proportional control hydraulic valve 4 and the handle 10. The controller 9 controls the high-speed switching hydraulic valve 3 through pulse width modulation, and realizes high-speed opening or closing of the valve by controlling the power on or off of the first electromagnetic coil Y1 and the second electromagnetic coil Y2.

[0047] The high-speed switching hydraulic valve 3 is connected to the rotary hydraulic motor 5. An electromagnetic coil is arranged in the high-speed switching hydraulic valve 3. The high-speed switching hydraulic valve 3 switches different high-speed switching working positions by gaining and losing power of the electromagnetic coil. When the crane is in a low-speed rotary state, the controller sends a PWM signal to the electromagnetic coil in the high-speed switching hydraulic valve 3, so that the high-speed switching hydraulic valve 3 is always in a high-speed switching state. By adjusting the duty cycle of the PWM signal, the flow rate of the hydraulic oil flowing into the rotary hydraulic motor 5 is changed, the rotary speed is increased, and speed compensation is performed to keep the rotary hydraulic motor 5 rotating at a uniform speed, so that the crane can maintain a stable rotary speed in the low-speed rotary state.

[0048] In this embodiment, the high-speed switching hydraulic valve 3 is a three-phase four-way valve, the inlet of the high-speed switching hydraulic valve 3 includes a high-speed switching hydraulic valve left inlet I, a high-speed switching hydraulic valve right inlet L, the outlet of the high-speed switching hydraulic valve 3 includes a high-speed switching hydraulic valve left outlet J, a high-speed switching hydraulic valve right outlet K, the high-speed switching hydraulic valve left outlet J is connected to the proportional control hydraulic valve left outlet D of the proportional control hydraulic valve 4, and the high-speed switching hydraulic valve right outlet K is connected to the proportional control hydraulic valve right outlet F of the proportional control hydraulic valve 4;

[0049] The high-speed switch hydraulic valve 3 is an electromagnetically controlled hydraulic valve, including a first high-speed switch working position, a second high-speed switch working position, and a third high-speed switch working position. When the first electromagnetic coil Y1 is energized, the high-speed switch hydraulic valve 3 is in the first high-speed switch working position, the left inlet I of the high-speed switch hydraulic valve is connected to the left outlet J of the high-speed switch hydraulic valve, and the right inlet L of the high-speed switch hydraulic valve is connected to the right outlet K of the high-speed switch hydraulic valve; when the second electromagnetic coil Y2 is energized, the valve is in the third high-speed switch working position, the left inlet I of the high-speed switch hydraulic valve is connected to the right outlet of the high-speed switch hydraulic valve, and the right inlet L of the high-speed switch hydraulic valve is connected to the left outlet J of the high-speed switch hydraulic valve; when the first electromagnetic coil Y1 and the second electromagnetic coil Y2 are both de-energized, the high-speed switch hydraulic valve 3 is in the second high-speed switch working position, the left inlet I of the high-speed switch hydraulic valve is not connected to the left outlet J of the high-speed switch hydraulic valve, and the right outlet K of the high-speed switch hydraulic valve is not connected.

[0050] The proportional control working position of the proportional control hydraulic valve 4 includes a first proportional control working position, a second proportional control working position, and a third proportional control working position. The proportional control hydraulic valve 4 is a three-phase six-way valve. The inlet of the proportional control hydraulic valve includes a left inlet A of the proportional control hydraulic valve, a middle inlet B of the proportional control hydraulic valve, and a right inlet C of the proportional control hydraulic valve. The left inlet A of the proportional control hydraulic valve and the middle inlet B of the proportional control hydraulic valve are connected to the outlet of the hydraulic pump 2; the outlet of the proportional control hydraulic valve 4 includes a left outlet D of the proportional control hydraulic valve, a middle outlet E of the proportional control hydraulic valve, and a right outlet F of the proportional control hydraulic valve; as the pilot pressure of the proportional control hydraulic valve 4 increases, the inlet and outlet openings of the proportional control hydraulic valve 4 increase, and more hydraulic oil flow can pass through. In this way, the output flow control of the proportional control hydraulic valve 4 can be obtained by controlling the handle 10.

[0051] When the proportional control hydraulic valve 4 is in the first proportional control working position, the left inlet A of the proportional control hydraulic valve is connected to the left outlet D of the proportional control hydraulic valve, the right inlet C of the proportional control hydraulic valve is connected to the right outlet F of the proportional control hydraulic valve, and the middle inlet B of the proportional control hydraulic valve and the middle outlet E of the proportional control hydraulic valve are both in the closed state;

[0052] When the proportional control hydraulic valve 4 is in the second proportional control working position, the middle inlet B of the proportional control hydraulic valve is connected to the middle outlet E of the proportional control hydraulic valve, and the left outlet D of the proportional control hydraulic valve and the right outlet F of the proportional control hydraulic valve are both connected to the right inlet C of the proportional control hydraulic valve;

[0053] When the proportional control hydraulic valve 4 is in the third proportional control working position, the left inlet A of the proportional control hydraulic valve is connected to the right outlet F of the proportional control hydraulic valve, the right inlet C of the proportional control hydraulic valve is connected to the left outlet D of the proportional control hydraulic valve, and the middle inlet B of the proportional control hydraulic valve and the middle outlet E of the proportional control hydraulic valve are both in the closed state;

[0054] The proportional control hydraulic valve left outlet D and the proportional control hydraulic valve right outlet F of the proportional control hydraulic valve 4 are connected to the first port G and the second port H of the rotary hydraulic motor 5 respectively;

[0055] The left and right ends of the proportional control hydraulic valve 4 are loading ends of the pilot pressure, wherein the left loading end is loaded with the left pilot pressure S1, and the right loading end is loaded with the right pilot pressure Sr. The above two pilot pressures are provided by the pilot control hydraulic valve 6 under the control of the handle 10.

[0056] In this embodiment, a relief valve 7 and a check valve 8 are also included. Between the proportional control hydraulic valve 4 and the hydraulic pump 2, the relief valve 7 is connected to the hydraulic oil tank 1 to control the hydraulic oil to flow back to the hydraulic oil tank. The check valve 8 is installed at the outlet of the hydraulic pump 2 to ensure the unidirectional flow of the hydraulic oil and prevent the hydraulic oil from flowing back. In the overflow circuit formed by the relief valve 7, the overflow circuit connects the inlet connecting the proportional control hydraulic valve 4 and the hydraulic pump 2 to the hydraulic oil tank 1 through the relief valve 7. The flow part that the hydraulic pump 2 cannot completely send to the rotary hydraulic motor 5 through the proportional control hydraulic valve 4 can directly flow back to the hydraulic oil tank 1 through the overflow pipeline. The rotary speed control device also has a check valve 8, which is connected to the outlet of the hydraulic pump 2. Its function is to ensure the unidirectional flow of the hydraulic oil and prevent the hydraulic oil from flowing back.

[0057] Based on the hydraulic speed control circuit of the above-mentioned truck crane slewing system, the present invention also discloses a corresponding hydraulic speed control method of the truck crane slewing system.

[0058] Determine the signal value of the handle;

[0059] In this embodiment, the opening range of the handle is 0 to 1000, and the opening is used to limit the range of movement of the handle. If the (opening) signal value of the handle is greater than or equal to 300, the crane is in a normal speed rotation state, and the first electromagnetic coil Y1 and the second electromagnetic coil Y2 of the high-speed switch hydraulic valve 3 are both not energized. At this time, the linearity of the proportional control hydraulic valve 4 is high, and the crane runs smoothly.

[0060] If the (opening) signal value of the handle is less than 300, the operation controller outputs a PWM signal with a frequency of 100 Hz, an amplitude of 15 mA, and an adjustable duty cycle, so that the amount of oil entering the rotary hydraulic motor 5 increases, and the speed of the rotary hydraulic motor 5 is compensated;

[0061] When the operating handle makes its handle (opening) signal value less than 300, when the proportional control hydraulic valve 4 is in the first proportional control working position, the crane rotates forward, and the crane is in a low-speed rotation state. At this time, the linearity of the proportional control hydraulic valve 4 is poor, and the rotation speed fluctuates. When the handle signal is lower than the target signal of the handle, the first electromagnetic coil Y1 of the high-speed switch hydraulic valve 3 is controlled by the PWM signal sent by the controller 9, and the first electromagnetic coil Y1 is energized, so that the amount of oil entering the left end of the rotary hydraulic motor 5 increases, and the rotation speed increases; when the rotation speed is equal to or close to the target rotation speed, the first electromagnetic coil Y1 of the high-speed switch hydraulic valve 3 loses power, and the motor continues to run under the control of the proportional control hydraulic valve 4 alone. The working principle of the crane's reverse low-speed rotation is similar. Those skilled in the art can achieve reverse low-speed rotation based on the above embodiments and the ordinary technical knowledge in this field they have mastered.

[0062] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", "top", "bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. In this patent, unless otherwise clearly stipulated and limited, the terms "connection", "fixed", etc. should be understood in a broad sense. For example, "fixed" can be a fixed connection, a detachable connection, or an integral whole; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hydraulic speed control circuit for a slewing system of a truck crane, comprising: A hydraulic oil tank (1), used for storing hydraulic oil; A hydraulic pump (2) provides liquid pressure energy for the entire hydraulic system; A proportional control hydraulic valve (4) switches between different proportional control working positions to provide hydraulic oil of different directions and flows to a rotary hydraulic motor (5); A rotary hydraulic motor (5), used for providing a rotary speed output, the rotary hydraulic motor being connected to the proportional control hydraulic valve (4); A pilot control hydraulic valve (6) is used to provide a pilot pressure, control the direction of the hydraulic oil, and control the output flow of the proportional control hydraulic valve (4); A handle (10), an operating end device for performing a rotation operation; The invention is characterized in that it further comprises a high-speed switch hydraulic valve (3) and a controller (9), wherein the controller (9) is respectively connected to the high-speed switch hydraulic valve (3), the proportional control hydraulic valve (4) and the handle (10), and the controller (9) controls the high-speed switch hydraulic valve through pulse width modulation, wherein the high-speed switch hydraulic valve (3) is connected to the rotary hydraulic motor (5), and an electromagnetic coil is arranged in the high-speed switch hydraulic valve (3), and the high-speed switch hydraulic valve (3) switches different high-speed switch working positions by gaining and losing power of the electromagnetic coil; When the crane is in a low-speed slewing state, the controller sends a PWM signal to the electromagnetic coil in the high-speed switch hydraulic valve (3), and changes the flow rate of the hydraulic oil flowing into the slewing hydraulic motor (5) by adjusting the duty cycle of the PWM signal to compensate for the slewing speed; The high-speed switching hydraulic valve (3) is a three-phase four-way valve. The inlet of the high-speed switching hydraulic valve (3) includes a high-speed switching hydraulic valve left inlet (I) and a high-speed switching hydraulic valve right inlet (L). The outlet of the high-speed switching hydraulic valve (3) includes a high-speed switching hydraulic valve left outlet (J) and a high-speed switching hydraulic valve right outlet (K). The high-speed switching hydraulic valve left outlet (J) is connected to the proportional control hydraulic valve left outlet (D) of the proportional control hydraulic valve (4), and the high-speed switching hydraulic valve right outlet (K) is connected to the proportional control hydraulic valve right outlet (F) of the proportional control hydraulic valve (4). The high-speed switch hydraulic valve (3) is an electromagnetically controlled hydraulic valve, comprising a first high-speed switch working position, a second high-speed switch working position, and a third high-speed switch working position. When the first electromagnetic coil (Y1) is energized, the high-speed switch hydraulic valve (3) is in the first high-speed switch working position, the left inlet (I) of the high-speed switch hydraulic valve is connected to the left outlet (J) of the high-speed switch hydraulic valve, and the right inlet (L) of the high-speed switch hydraulic valve is connected to the right outlet (K) of the high-speed switch hydraulic valve; when the second electromagnetic coil (Y2) is energized, the valve is in the third high-speed switch working position, the left inlet (I) of the high-speed switch hydraulic valve is connected to the right outlet of the high-speed switch hydraulic valve, and the right inlet (L) of the high-speed switch hydraulic valve is connected to the left outlet (J) of the high-speed switch hydraulic valve; when both the first electromagnetic coil (Y1) and the second electromagnetic coil (Y2) are de-energized, the high-speed switch hydraulic valve (3) is in the second high-speed switch working position, the left inlet (I) of the high-speed switch hydraulic valve is not connected to the left outlet (J) of the high-speed switch hydraulic valve, and the right outlet (K) of the high-speed switch hydraulic valve is not connected; When the operating handle makes the signal value of the handle (10) less than 300, and the proportional control hydraulic valve (4) is in the first proportional control working position, the crane is in a low-speed slewing state. At this time, the linearity of the proportional control hydraulic valve (4) is poor, and the slewing speed fluctuates. The first electromagnetic coil Y1 of the high-speed switch hydraulic valve (3) is controlled by the PWM signal sent by the controller (9), and the first electromagnetic coil Y1 is energized, so that the amount of oil entering the left end of the slewing hydraulic motor (5) increases, and the slewing speed increases; when the slewing speed is equal to or close to the target slewing speed, the first electromagnetic coil Y1 of the high-speed switch hydraulic valve (3) loses power, and the slewing hydraulic motor (5) continues to operate under the sole control of the proportional control hydraulic valve (4); The proportional control working positions of the proportional control hydraulic valve (4) include a first proportional control working position, a second proportional control working position, and a third proportional control working position. The proportional control hydraulic valve (4) is a three-phase six-way valve. The inlet of the proportional control hydraulic valve includes a left inlet (A) of the proportional control hydraulic valve, a middle inlet (B) of the proportional control hydraulic valve, and a right inlet (C) of the proportional control hydraulic valve. The left inlet (A) of the proportional control hydraulic valve and the middle inlet (B) of the proportional control hydraulic valve are connected to the outlet of the hydraulic pump (2). The outlet of the proportional control hydraulic valve (4) includes a left outlet (D) of the proportional control hydraulic valve, a middle outlet (E) of the proportional control hydraulic valve, and a right outlet (F) of the proportional control hydraulic valve. When the proportional control hydraulic valve (4) is in the first proportional control working position, the left inlet (A) of the proportional control hydraulic valve is connected to the left outlet (D) of the proportional control hydraulic valve, the right inlet (C) of the proportional control hydraulic valve is connected to the right outlet (F) of the proportional control hydraulic valve, and the middle inlet (B) of the proportional control hydraulic valve and the middle outlet (E) of the proportional control hydraulic valve are both in a closed state; When the proportional control hydraulic valve (4) is in the second proportional control working position, the middle inlet (B) of the proportional control hydraulic valve is connected to the middle outlet (E) of the proportional control hydraulic valve, and the left outlet (D) of the proportional control hydraulic valve and the right outlet (F) of the proportional control hydraulic valve are both connected to the right inlet (C) of the proportional control hydraulic valve; When the proportional control hydraulic valve (4) is in the third proportional control working position, the left inlet (A) of the proportional control hydraulic valve is connected to the right outlet (F) of the proportional control hydraulic valve, the right inlet (C) of the proportional control hydraulic valve is connected to the left outlet (D) of the proportional control hydraulic valve, and the middle inlet (B) of the proportional control hydraulic valve and the middle outlet (E) of the proportional control hydraulic valve are both in a closed state; A proportional control hydraulic valve left outlet (D) and a proportional control hydraulic valve right outlet (F) of the proportional control hydraulic valve (4) are respectively connected to a first port (G) and a second port (H) of a rotary hydraulic motor (5); The left and right ends of the proportional control hydraulic valve (4) are loading ends of the pilot pressure, wherein the left loading end is loaded with the left pilot pressure (S1), and the right loading end is loaded with the right pilot pressure (Sr), and the above two pilot pressures are provided by the pilot control hydraulic valve (6) under the control of the handle (10); The outlet of the hydraulic pump (2) is respectively delivered to the inlet of the high-speed switching hydraulic valve (3) and the proportional control hydraulic valve (4); The hydraulic oil tank (1) is connected to the right inlet (C) of the proportional control hydraulic valve and the middle outlet (E) of the proportional control hydraulic valve.

2. The hydraulic speed control circuit of the slewing system of a truck crane according to claim 1, characterized in that: It also includes an overflow valve (7) between the proportional control hydraulic valve (4) and the hydraulic pump (2), which is connected to the hydraulic oil tank (1) through the overflow valve (7) and is used to control the hydraulic oil to flow back to the hydraulic oil tank.

3. The hydraulic speed control circuit of the slewing system of a truck crane according to claim 1, characterized in that: It also comprises a one-way valve (8), which is installed at the outlet of the hydraulic pump (2) and is used to ensure the one-way flow of hydraulic oil.

4. The hydraulic speed control circuit of the slewing system of a truck crane according to claim 1, characterized in that: The inlet of the hydraulic pump (2) is connected to the hydraulic oil tank (1) and is used to extract the hydraulic oil in the hydraulic oil tank (1).

5. The hydraulic speed control circuit of the slewing system of a truck crane according to claim 1, characterized in that: The pilot control hydraulic valve (6) is provided with a first input port (T), a second input port (P), a first output port (P1) and a second output port (P2); the pilot control hydraulic valve (6) provides a right pilot pressure (Sr) through the first output port (P1) and provides a left pilot pressure (Sl) through the second output port (P2).

6. The hydraulic speed control circuit of the slewing system of a truck crane according to claim 5, characterized in that: The pilot control hydraulic valve (6) is connected to a pilot pump and obtains pressure oil from the pilot pump.

7. A method for controlling the hydraulic speed of a slewing system of a truck crane based on the hydraulic speed control circuit of the slewing system of a truck crane as claimed in any one of claims 1 to 6, characterized in that: Specifically include: Determine the signal value of the handle; If the signal value of the handle is greater than or equal to 300, the first electromagnetic coil (Y1) and the second electromagnetic coil (Y2) of the high-speed switching hydraulic valve (3) shall not be energized; If the signal value of the handle is less than 300, the operating controller outputs a PWM signal with a frequency of 100 Hz, an amplitude of 15 mA and an adjustable duty cycle, so that the amount of oil entering the rotary hydraulic motor (5) is increased, and the speed of the rotary hydraulic motor (5) is compensated.

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