Variable amplitude cylinder hydraulic control system and jib tower crane

Abstract

The application relates to the technical field of engineering machinery, and discloses a boom cylinder hydraulic control system and a luffing tower crane. The boom cylinder hydraulic control system comprises a boom cylinder used for driving a luffing of a boom support to perform a boom lifting action or a boom lowering action; a rod cavity locking valve arranged in a rod cavity working oil path of the boom cylinder; a rod cavity locking valve and an electric control locking valve group arranged in series in a rod cavity working oil path; wherein the electric control locking valve group comprises a hydraulic control check valve and an electromagnetic reversing valve, a pilot control oil path of the hydraulic control check valve is hydraulically connected to the rod cavity working oil path, the electromagnetic reversing valve is arranged in a bypass oil path between two ends of the hydraulic control check valve and is used for controlling the bypass oil path to be conducted or one-way cut off, and hydraulic oil can flow to the rod cavity in sequence through the hydraulic control check valve and the rod cavity locking valve and is reversely cut off. The electric control locking valve group is additionally arranged on the basis of the original rod cavity locking valve, double hydraulic locking can be realized, and the safety reliability and controllability of the luffing of the boom support are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engineering machinery, in particular, to a boom cylinder hydraulic system and a luffing tower crane. BACKGROUND

[0002] Figure 1 The figure is a hydraulic principle diagram of the oil cylinder locking circuit commonly used in the prior art. Generally, the luffing tower crane drives the luffing cylinder 1 to drive the lifting arm to perform the actions of lifting and lowering the arm. As shown in the figure, the rodless cavity and the rod cavity of the luffing cylinder 1 are respectively provided with a balance valve. In the action of lifting the arm, the high-pressure oil of the hydraulic system pushes the piston rod to extend, thereby driving the lifting arm to lift up and realizing the luffing movement in the design range, and at the same time, the oil in the rod cavity is returned through the rod cavity locking valve 3. In the action of lowering the arm, the piston of the oil cylinder is driven to retract under the action of the weight of the lifting arm, and the rodless cavity locking valve 2 (i.e. the balance valve) plays a role in balancing the load, so that the action of lowering the arm is stable. In addition, when the action stops or there is no action, the rodless cavity locking valve 2 seals the oil in the rodless cavity, locks the oil cylinder, and brakes the luffing action of the lifting arm. Figure 1 However, due to the cleanliness of the oil and other reasons, the long-term use of the oil inevitably contains impurities, and the valve core of the rodless cavity locking valve 2 may be stuck, resulting in the failure to seal the oil. At this time, under the action of the gravity of the lifting arm, the oil in the rodless cavity flows out from the rodless cavity locking valve 2, the piston rod of the oil cylinder retracts, the lifting arm lowers, and the lowering speed of the lifting arm becomes faster and faster. When the lifting arm lowers to 0°, it will collide with other structural parts of the tower crane, causing structural damage. If there is a heavy object on the hook, the uncontrolled lowering of the arm will make the lifting moment of the whole machine become larger and larger, eventually exceeding the limit lifting moment of the whole machine and causing structural damage.

[0003] SUMMARY The present application relates to the technical field of engineering machinery, in particular, to a boom cylinder hydraulic system and a luffing tower crane.

[0004] The purpose of the present application is to provide a luffing cylinder hydraulic system and a luffing tower crane to improve the safety and controllability of the luffing of the boom.

[0005] To achieve the above purpose, the present application provides a luffing cylinder hydraulic control system, comprising:

[0006] a luffing cylinder, configured to drive the luffing of the boom to perform the actions of lifting or lowering the arm;

[0007] a rod cavity locking valve, arranged in the rod cavity working oil path of the luffing cylinder;

[0008] a rodless cavity locking valve and an electric control locking valve group, arranged in series in the rodless cavity working oil path of the luffing cylinder;

[0009] The electric control locking valve group comprises a hydraulic control check valve and an electromagnetic reversing valve, the pilot control oil way of the hydraulic control check valve is hydraulically connected to the rod cavity working oil way, the electromagnetic reversing valve is arranged in the bypass oil way between the two ends of the hydraulic control check valve and is used for controlling the bypass oil way to be conducted or one-way cut-off, and the hydraulic oil can flow to the rodless cavity through the hydraulic control check valve and the rodless cavity locking valve in turn and is reversely cut off.

[0010] In some embodiments, the electromagnetic reversing valve is an electromagnetic on-off valve; or the electromagnetic reversing valve comprises a conducting valve position and a one-way cut-off valve position, and the hydraulic oil flowing to the rodless cavity can pass through the one-way cut-off valve position and is reversely cut off.

[0011] In some embodiments, the rodless cavity locking valve and the rod cavity locking valve are balance valves or one-way hydraulic locks.

[0012] In some embodiments, the boom cylinder hydraulic control system comprises a controller, which communicates with the electromagnetic reversing valve and is configured to:

[0013] determine that the boom cylinder is retracted to perform the boom action;

[0014] control the electromagnetic reversing valve to switch to the conducting valve position to open the bypass oil way.

[0015] In some embodiments, the boom cylinder hydraulic control system comprises:

[0016] a pressure detection element for detecting the oil pressure of the rod cavity working oil way or the rod cavity;

[0017] The controller is further configured to:

[0018] determine that the boom cylinder is retracted to perform the boom action;

[0019] determine that the oil pressure detection value of the pressure detection element is less than a preset low pressure threshold value;

[0020] control the electromagnetic reversing valve to switch to the one-way cut-off valve position to cut off the bypass oil way.

[0021] In some embodiments, the boom cylinder hydraulic control system comprises:

[0022] a main reversing valve for controlling the extension and retraction of the boom cylinder;

[0023] The controller communicates with the main reversing valve and is configured to:

[0024] determine that the main reversing valve is switched from a first reversing valve position for driving the boom cylinder to retract to an intermediate valve position;

[0025] after a preset delay time after the main reversing valve switches back to the intermediate valve position, the controller controls the electromagnetic reversing valve to switch to a one-way cut-off valve position, so that the bypass oil path is cut off.

[0026] In some embodiments, the preset low pressure threshold is 0.5-0.8 MPa, and the preset delay time is 2-6 s.

[0027] In some embodiments, the main reversing valve has a Y-type intermediate position function.

[0028] In some embodiments, the controller is further configured to:

[0029] determine that the main reversing valve remains in the intermediate valve position;

[0030] control the electromagnetic reversing valve to remain in the one-way cut-off valve position, so that the bypass oil path is cut off.

[0031] In some embodiments, the controller is further configured to:

[0032] determine that the boom cylinder extends to perform the boom-raising action;

[0033] control the electromagnetic reversing valve to remain in the one-way cut-off valve position, so that the bypass oil path is cut off.

[0034] The application also protects a luffing tower crane, which comprises a boom and the above-mentioned boom cylinder hydraulic control system, and the boom cylinder is used to drive the boom to raise or lower.

[0035] In the boom cylinder hydraulic control system and the tower crane according to the embodiment of the present application, the electric control locking valve group is additionally provided on the basis of the original rodless cavity locking valve, including the parallel liquid control check valve and the electromagnetic reversing valve, and the double hydraulic locking is realized through the rodless cavity locking valve and the liquid control check valve, and when the rodless cavity locking valve leaks, the liquid control check valve can further lock the hydraulic oil in the rodless cavity to prevent the impact between the boom and other structural members of the tower crane caused by the out-of-control boom, and improve the safety and reliability and the controllability of the boom luffing process; the bypass oil path is connected between the two ends of the liquid control check valve, the electromagnetic reversing valve is arranged in the bypass oil path, when the electromagnetic reversing valve is powered on, the oil pressure acting on the valve core of the liquid control check valve is reduced due to the shunt effect, thereby reducing the pilot oil pressure required for the reverse opening of the liquid control check valve, and the more reliable return of the oil in the rodless cavity can be realized when the liquid control check valve is difficult to open, and during the boom luffing process, the control of the double locking hydraulic circuit can be realized, when the boom luffing cylinder extends, the electromagnetic reversing valve is not powered on, and the hydraulic oil flows through the liquid control check valve and the electromagnetic reversing valve in one direction. When the boom luffing cylinder retracts, the electromagnetic reversing valve is powered on; during the boom luffing cylinder retraction process, if it is judged that the boom action is out of control or overspeed, the electromagnetic reversing valve is powered off, the bypass oil path is one-way cut off, and at the same time, the liquid control check valve is also locked due to the low control pressure, so that the cylinder piston rod is locked by the electric control locking valve group, and the boom is braked.

[0036] Other features and advantages of the embodiments of the present application will be described in detail in the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are included to provide a further understanding of the embodiments of the present application, and constitute a part of the specification, and are used together with the following detailed description to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. For those skilled in the art, other drawings can be obtained from the structures shown in the drawings without creative labor. In the drawings:

[0038] Figure 1 It is the hydraulic principle diagram of the cylinder locking circuit commonly used in the prior art;

[0039] Figure 2 It is the hydraulic principle diagram of the boom cylinder hydraulic system according to the embodiment of the present application;

[0040] Figure 3 It is the control principle diagram of the controller in the boom cylinder hydraulic system according to the embodiment of the present application.

[0041] Explanation of reference signs:

[0042] 1 boom cylinder 2 rodless cavity locking valve

[0043] 3 rod cavity locking valve 4 electrically controlled locking valve group

[0044] 5 main reversing valve

[0045] 41 hydraulic control check valve 42 electromagnetic reversing valve

[0046] L1 rodless cavity working oil path L2 rod cavity working oil path

[0047] L3 bypass oil path DETAILED DESCRIPTION

[0048] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0049] The boom cylinder hydraulic system and the luffing tower crane of the present application will be described in detail below with reference to the accompanying drawings and in combination with exemplary embodiments.

[0050] The present application discloses a novel boom cylinder hydraulic control system. As shown in Figure 2 in one specific embodiment, the boom cylinder hydraulic control system comprises:

[0051] a boom cylinder 1 for driving the luffing of the jib to perform the boom-raising action or the boom-lowering action;

[0052] a rod cavity locking valve 3 arranged in the rod cavity working oil path L2 of the boom cylinder 1;

[0053] a rodless cavity locking valve 2 and an electrically controlled locking valve group 4 arranged in series in the rodless cavity working oil path L1 of the boom cylinder 1;

[0054] The electrically controlled locking valve group 4 comprises a hydraulic control check valve 41 and an electromagnetic reversing valve 42, the pilot control oil path of the hydraulic control check valve 41 is hydraulically connected to the rod cavity working oil path L2, the electromagnetic reversing valve 42 is arranged in the bypass oil path L3 between the two ends of the hydraulic control check valve 41 and is used to control the conduction or one-way cut-off of the bypass oil path L3, and the hydraulic oil can flow to the rodless cavity in sequence through the hydraulic control check valve 41 and the rodless cavity locking valve 2 and be reversely cut off.

[0055] The application aims to improve the safety and reliability and maneuverability of the boom luffing process, and thus an electric control locking valve group 4 is additionally provided on the basis of the original locking valve, and double hydraulic locking is realized through the hydraulic control check valve 41, for example, when the locking valve 3 of the rod cavity leaks, the hydraulic oil of the rodless cavity can be further locked through the hydraulic control check valve 41. Further, the bypass oil path L3 is connected between the a1 port and the a2 port at both ends of the hydraulic control check valve 41, and the electromagnetic reversing valve 42 is arranged in the bypass oil path L3. When the electromagnetic reversing valve 42 is powered on, the oil hydraulic pressure acting on the valve core of the hydraulic control check valve 41 is lower, thereby reducing the pilot oil hydraulic pressure required for the reverse opening of the hydraulic control check valve 41, and realizing reliable return of the oil of the rodless cavity when the hydraulic control check valve 41 cannot be opened. In addition, more control options are provided during the boom luffing process, which will be described in detail below.

[0056] For example, in the prior art Figure 2 Before the pressure pilot of the rod cavity working oil path L2 opens the hydraulic control check valve 41, the a2 port is in a closed state. If the rodless cavity locking valve 2 has been opened, the oil at the a2 port is blocked at high pressure, which acts on the valve core of the hydraulic control check valve 41, hinders the opening of the hydraulic control check valve 41, and the high pressure at the a2 port also acts on the valve core of the rodless cavity locking valve 2, so that the rodless cavity locking valve 2 tends to close. Thus, the cylinder action cannot be started, or after starting, it is paused and vibrates.

[0057] In addition, when the rodless cavity working oil path L1 is simply connected in series with the rodless cavity locking valve 2 and the hydraulic control check valve 41, the cylinder action is not stable in the specific working process, which is easy to cause the loop to be self-locked or to run with vibration. Therefore, the bypass oil path L3 and the electromagnetic reversing valve 42 can assist the opening and closing of the hydraulic control check valve 41, so that the cylinder action process is stable.

[0058] It should be noted that the electromagnetic reversing valve 42 is used to control the bypass oil path L3 to be conducted or one-way cut off. The "oil path cut off" can be bidirectional cut off or one-way cut off of the oil path. When used to control the bidirectional cut off of the bypass oil path L3, the electromagnetic reversing valve 42 can adopt an electromagnetic switch valve. When used to control the one-way cut off of the bypass oil path L3, the electromagnetic reversing valve 42 can adopt a Figure 2 The reversing valve shown in the figure includes a conducted valve position and a one-way cut off valve position, and the one-way cut off valve position is provided with a one-way valve, so that the hydraulic oil flowing to the rodless cavity direction can pass through the one-way cut off valve position and is reversely cut off.

[0059] Referring to Figure 2In the embodiment, in the de-energized state of the electromagnetic reversing valve 42, the spool switches to the left valve position shown in the figure, i.e. the one-way check valve position, the liquid flow between the a1 port and the a2 port is one-way flow, and the direction from the a2 port to the a1 port is closed; in the energized state of the electromagnetic reversing valve 42, the spool switches to the right valve position shown in the figure, i.e. the open valve position, the a1 port and the a2 port are communicated. The control oil port a3 of the hydraulic control one-way valve 41 is connected with the rod cavity working oil path L2, and the direction from the a1 port to the a2 port of the hydraulic control one-way valve 41 is one-way flow, and the direction from the a2 port to the a1 port needs the pressure of the rod cavity working oil path L2 to open the hydraulic control one-way valve 41, so as to realize the flow in the direction from the a2 port to the a1 port, and if the pressure of the rod cavity working oil path L2 is insufficient, the direction from the a2 port to the a1 port of the hydraulic control one-way valve 41 is closed.

[0060] In addition, the rodless cavity locking valve 2 and the rod cavity locking valve 3 can adopt a balance valve, as shown in Figure 2 However, in other embodiments, the rodless cavity locking valve 2 and the rod cavity locking valve 3 can also adopt a one-way hydraulic lock and the like.

[0061] The hydraulic control system of the variable amplitude oil cylinder can further include a controller (not shown in the figure), which is in communication with the electromagnetic reversing valve 42 and is configured to:

[0062] determine that the variable amplitude oil cylinder 1 is retracted to perform the lying arm action;

[0063] control the electromagnetic reversing valve 42 to switch to the open valve position, and the bypass oil path L3 is open.

[0064] It can be seen that when the hydraulic oil cylinder 1 is passively retracted due to the self-weight action of the boom or is actively retracted by supplying pressure oil to the rod cavity through the rod cavity working oil path L2, it can be determined that the oil cylinder is currently retracted and performs the lying arm action, at this time, the electromagnetic reversing valve 42 can be controlled to switch to the open valve position, so that the bypass oil path L3 is open, the rodless cavity oil can be returned through the rodless cavity working oil path L1, and the returned oil sequentially passes through the rodless cavity locking valve 2, the electromagnetic reversing valve 42 and the like. In other words, when the oil cylinder is retracted to perform the lying arm action, the additional electrically controlled locking valve group 4 does not affect the rodless return and does not cause any obstruction to the oil cylinder retraction under reasonable control.

[0065] In other working conditions, the hydraulic control system of the variable amplitude oil cylinder can include:

[0066] a pressure detection element for detecting the oil pressure of the rod cavity working oil path L2 or the rod cavity;

[0067] Referring to Figure 3 , the controller is further configured to perform the following steps:

[0068] S100, determining that the variable amplitude oil cylinder 1 is retracted to perform the lying arm action;

[0069] S200, determine that the oil pressure detection value of the pressure detection element is less than the preset low pressure threshold;

[0070] S300 controls the solenoid directional valve 42 to switch to the one-way shut-off valve position, thereby shutting off the bypass oil circuit L3.

[0071] It should be noted that if the measured value of the rod chamber oil pressure detected by the pressure detection element (not shown in the figure) is less than the preset low-pressure threshold, it indicates that the rod chamber expansion speed is too fast, which means that the cylinder retraction speed is too fast, or even out of control, requiring intervention. Therefore, the solenoid directional valve 42 can be switched to the one-way shut-off valve position in a timely manner, thus cutting off the bypass oil circuit L3. The hydraulically controlled one-way valve 41 then hydraulically locks the oil in the rodless chamber, eliminating the risk caused by excessively rapid boom movement and improving the safety and reliability of boom luffing.

[0072] like Figure 2 As shown, the hydraulic control system for the luffing cylinder may also include:

[0073] Main directional valve 5 is used to control the extension and retraction of luffing cylinder 1;

[0074] The controller communicates with and is configured to communicate with the main directional valve 5 as follows:

[0075] Determine that the main directional valve 5 switches from the first directional valve position, where the drive luffing cylinder 1 retracts, back to the intermediate valve position;

[0076] After a preset delay time following the main directional valve 5 switching back to the intermediate valve position, the solenoid directional valve 42 is switched to the one-way shut-off valve position, thereby shutting off the bypass oil circuit L3.

[0077] The main directional valve 5 controls the extension and retraction of the luffing cylinder 1. It can be a proportional directional valve with a proportional solenoid as shown in the diagram, or it can be a manually operated directional valve, a hydraulically piloted directional valve, etc. It can exist independently or be integrated into a multi-way valve as one of its components. Figure 2 Taking the three-position four-way main directional valve 5 as an example, when the cylinder retracts to the end of the boom movement, the main directional valve 5 should switch from the right valve position (i.e., the first directional valve position) back to the middle valve position. It should be noted that the main directional valve 5 shown in the diagram has a Y-type neutral position function, meaning that in the middle valve position of the main directional valve 5, the rodless chamber working oil circuit L1 and the rod chamber working oil circuit L2 are short-circuited and return oil. At this time, the system locks the rodless chamber through the rodless chamber lock-up valve 2.

[0078] After the main directional valve 5 switches back to the intermediate valve position, it waits for a preset delay time, allowing the oil in the rodless chamber working oil circuit L1 to continue returning through the intermediate valve position of the main directional valve 5. Then, the solenoid directional valve 42 is controlled to switch to the one-way shut-off valve position, thus shutting off the bypass oil circuit L3. At this time, the hydraulically controlled one-way valve 41, together with the rodless chamber lock-up valve 2, locks the rodless chamber.

[0079] In the embodiment, the preset low pressure threshold is 0.5-0.8 MPa, and the preset delay time is 2-6 s, which can meet the requirements of the hydraulic system. Figure 2 The use control of the hydraulic system is shown. Of course, in the hydraulic system of other embodiments or when other hydraulic valves are used, the preset low pressure threshold and the preset delay time can be adaptively adjusted according to different parameters.

[0080] When the telescopic oil cylinder 1 does not act, the controller can also be configured to:

[0081] determine that the main reversing valve 5 remains in the intermediate valve position;

[0082] control the electromagnetic reversing valve 42 to remain in the one-way cut-off valve position, so that the bypass oil path L3 is cut off.

[0083] At this time, the hydraulic control one-way valve 41 and the rodless cavity locking valve 2 jointly lock the rodless cavity, and the function of redundant hydraulic locking is achieved, and the locking reliability is higher.

[0084] When the telescopic oil cylinder 1 extends to perform the arm lifting action, the controller can also be configured to:

[0085] determine that the telescopic oil cylinder 1 extends to perform the arm lifting action;

[0086] control the electromagnetic reversing valve 42 to remain in the one-way cut-off valve position, so that the bypass oil path L3 is cut off.

[0087] At this time, the pressure oil enters from the A port of the electric control locking valve group 4, flows to the rodless cavity locking valve 2 through the hydraulic control one-way valve 41 and the one-way cut-off valve position of the electromagnetic reversing valve 42, and then flows to the rodless cavity through the one-way valve in the rodless cavity locking valve 2, to drive the piston rod to extend. Of course, in other embodiments, the electromagnetic reversing valve 42 can also remain in the conductive valve position when the arm lifting action is performed, and at this time, the hydraulic control one-way valve 41 is virtually non-existent, but does not hinder the hydraulic oil from guiding the rodless cavity to drive the piston rod to extend.

[0088] The application also protects a luffing tower crane, which comprises a jib and the above-mentioned luffing oil cylinder hydraulic control system, and the luffing oil cylinder 1 is used to drive the jib to lift or lie down. Due to the adoption of the above-mentioned luffing oil cylinder hydraulic control system, the control of the jib lifting or lying down action of the luffing tower crane is more flexible, safe and reliable.

[0089] The following describes the luffing oil cylinder hydraulic control system and the luffing driving control process of the boom in the embodiment. Figure 2

[0090] ​Generally, the rod cavity working oil path L2 and the non-rod cavity working oil path L1 are connected to two working oil ports of the main reversing valve 5 respectively, by controlling the main reversing valve 5, the pressure oil enters the non-rod cavity working oil path L1, the oil is supplied to the non-rod cavity, the piston rod is driven to push out, the oil in the rod cavity is returned to the tank from the rod cavity working oil path L2, at this time the oil cylinder is extended, the driving arm frame performs the lifting arm action. When the pressure oil enters the rod cavity working oil path L2 and returns to the tank from the non-rod cavity working oil path L1, the oil cylinder is retracted, the driving arm frame performs the lifting arm action.

[0091] When the boom, i.e. the luffing cylinder 1 is extended, the control electromagnetic reversing valve 42 is not powered, the hydraulic oil flows from a1 port to a2 port, and flows through the hydraulic control check valve 41 and the electromagnetic reversing valve 42 in one direction. When the boom, i.e. the luffing cylinder 1 is retracted, the non-rod cavity working oil path L1 is communicated with the tank, there is only a small back pressure (usually within 3 MPa) at A port, at this time the control electromagnetic reversing valve 42 is powered, a2 port and a1 port are communicated, and a2 port also has only a small back pressure, so that the hydraulic control check valve 41 can be smoothly opened. If the electromagnetic reversing valve 42 is missing, before the hydraulic control check valve 41 is opened by the pressure in the rod cavity, a2 port is in a closed state, if the non-rod cavity balance valve (i.e. the non-rod cavity locking valve 2) has been opened, the oil is blocked at a2 port with high pressure, this pressure acts on the spool of the hydraulic control check valve 41, which hinders the opening of the hydraulic control check valve 41, and the high pressure at a2 port also acts on the spool of the balance valve, which makes the balance valve tend to close. Thus, it will lead to that the cylinder retraction action cannot be started, or after starting, it stops and shakes again.

[0092] When the boom, i.e. the luffing cylinder 1 is retracted, the control electromagnetic reversing valve 42 is de-energized after the main reversing valve 5 is switched back to the intermediate valve position for several seconds (recommended 2-6s). During the boom, i.e. the luffing cylinder 1 retraction deceleration and braking process, the electromagnetic reversing valve 42 keeps a2 and a1 ports communicated, so as to prevent the hydraulic control check valve 41 from being closed due to the pressure reduction of the rod cavity working oil path L2, which brings impact and shaking. In theory, after the boom, i.e. the luffing cylinder 1 retraction action stops, the electromagnetic reversing valve 42 can be de-energized. In the absence of displacement detection, the de-energization of the electromagnetic reversing valve 42 is controlled according to the main reversing valve 5 returning to the intermediate position as the starting point for a delay (several seconds). In addition, during the boom, i.e. the luffing cylinder 1 retraction action, the pressure in the rod cavity or the pressure of the rod cavity working oil path L2 is detected, when the pressure is lower than the low pressure threshold (for example 0.5-0.8 MPa), it is judged that the boom action is out of control or overspeed, at this time the control electromagnetic reversing valve 42 is de-energized, the oil in the non-rod cavity of the oil cylinder is locked, the oil cylinder piston rod is locked by the electric control locking valve group 4, and the crane boom is braked.

[0093] When the piston rod of the variable-amplitude oil cylinder 1 is extended (arm-raising), the electromagnetic reversing valve 42 of the electric control locking valve group 4 is in a power-off state; the rod cavity working oil circuit L2 is communicated with the oil tank, and is low pressure; at this time, if the balance valve core is stuck, the arm-raising action stops, the hydraulic control check valve 41 and the electromagnetic reversing valve 42 of the electric control locking valve group 4 are in a closed state in the direction of a2 to a1 port, the rod cavity oil is blocked, the oil cylinder piston rod is locked by the electric control locking valve group 4, the crane boom is braked, and uncontrolled arm-laying does not occur.

[0094] When the oil cylinder is not in action, the electromagnetic reversing valve 42 of the electric control locking valve group 4 is in a power-off state; at this time, if the balance valve core is stuck, the arm-raising action stops, the hydraulic control check valve 41 and the electromagnetic reversing valve 42 of the electric control locking valve group 4 are in a closed state in the direction of a2 to a1 port, the rod cavity oil is blocked, the oil cylinder piston rod is locked by the electric control locking valve group 4, the crane boom is braked, and uncontrolled arm-laying does not occur.

[0095] In summary, in the variable-amplitude oil cylinder hydraulic control system of the present application, on the basis of the balance valve in the rodless cavity of the variable-amplitude oil cylinder, the electric control locking valve group 4 is additionally arranged in the rodless cavity working circuit, which is composed of the electromagnetic reversing valve 42 and the hydraulic control check valve 41 in parallel. In this way, the control of the double-locking hydraulic circuit can be realized. When the arm is raised, i.e. the variable-amplitude oil cylinder is extended, the electromagnetic reversing valve 42 is not powered, and a1 to a2 ports pass through the hydraulic control check valve 41 and the electromagnetic reversing valve 42 for one-way flow. When the arm is laid, i.e. the variable-amplitude oil cylinder is retracted, the control electromagnetic reversing valve 42 is powered; when the arm-laying, i.e. the variable-amplitude oil cylinder retraction, is decelerated and braked to stop, the control electromagnetic reversing valve 42 is power-off after the main reversing valve 5 is in the middle position for a few seconds; during the arm-laying, i.e. the variable-amplitude oil cylinder retraction, the rod cavity pressure or the rod cavity working oil circuit L2 pressure is detected, and when the pressure is lower than the low pressure threshold, it is judged that the arm-laying action is out of control or overspeed, then the control electromagnetic reversing valve 42 is power-off, the bypass oil circuit L3 is one-way blocked, and at the same time, due to the low control pressure of the hydraulic control check valve 41, the hydraulic control check valve 41 is also locked, so that the oil cylinder piston rod is locked by the electric control locking valve group 4, and the crane boom is braked. When the oil cylinder is not in action, the electromagnetic reversing valve 42 of the electric control locking valve group 4 can be controlled to be in a power-off state. The whole control process is flexible, but the safety and reliability is greatly improved, especially when it is applied to the control process of the arm-raising or arm-laying action of the crane boom.

[0096] In the description of the present application, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0097] In this application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection or communication with each other; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0098] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0099] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A hydraulic control system for a variable amplitude cylinder, characterized by, The variable amplitude oil cylinder hydraulic control system comprises: a variable amplitude oil cylinder (1) for driving the arm frame to perform a boom raising action or a boom lowering action; a rod cavity locking valve (3) arranged in a rod cavity working oil path (L2) of the variable amplitude oil cylinder (1); a rodless cavity locking valve (2) and an electrically controlled locking valve group (4) arranged in series in a rodless cavity working oil path (L1) of the variable amplitude oil cylinder (1); a main reversing valve (5) for controlling the extension and retraction of the variable amplitude oil cylinder (1); wherein the electrically controlled locking valve group (4) comprises a hydraulic control check valve (41) and an electromagnetic reversing valve (42), a pilot control oil path of the hydraulic control check valve (41) is hydraulically connected to the rod cavity working oil path (L2), the electromagnetic reversing valve (42) is arranged in a bypass oil path (L3) between two ends of the hydraulic control check valve (41) and is used for controlling the bypass oil path (L3) to be conducted or one-way cut off, hydraulic oil can flow to the rodless cavity in sequence through the hydraulic control check valve (41) and the rodless cavity locking valve (2) and be reversely cut off; the variable amplitude oil cylinder hydraulic control system further comprises a controller, the controller is in communication with the electromagnetic reversing valve (42) and is configured to: determine that the variable amplitude oil cylinder (1) is retracted to perform the boom lowering action; control the electromagnetic reversing valve (42) to switch to a conducting valve position to open the bypass oil path (L3); and the controller is in communication with the main reversing valve (5) and is configured to: determine that the main reversing valve (5) is switched from a first reversing valve position for driving the variable amplitude oil cylinder (1) to retract to a middle valve position; after a preset delay time after the main reversing valve (5) is switched to the middle valve position, control the electromagnetic reversing valve (42) to switch to a one-way cut-off valve position so that the bypass oil path (L3) is cut off.

2. The hydraulic control system for a variable amplitude cylinder according to claim 1, wherein The electromagnetic reversing valve (42) is an electromagnetic on-off valve; or the electromagnetic reversing valve (42) comprises a conducting valve position and a one-way cut-off valve position, and hydraulic oil flowing to the rodless cavity direction can pass through the one-way cut-off valve position and be reversely cut off.

3. The hydraulic control system for a variable amplitude cylinder according to claim 1, wherein The rodless cavity locking valve (2) and the rod cavity locking valve (3) are balance valves or one-way hydraulic locks.

4. The hydraulic control system for a variable amplitude cylinder according to claim 1, wherein The variable amplitude oil cylinder hydraulic control system comprises: a pressure detection element for detecting the oil pressure of the rod cavity working oil path (L2) or the rod cavity; wherein the controller is further configured to: determine that the variable amplitude oil cylinder (1) is retracted to perform the boom lowering action; determine that the oil pressure detection value of the pressure detection element is less than a preset low pressure threshold value; control the electromagnetic reversing valve (42) to switch to a one-way cut-off valve position so that the bypass oil path (L3) is cut off.

5. The hydraulic control system for a variable amplitude cylinder according to claim 4, wherein The preset low pressure threshold value is 0.5-0.8 MPa, and the preset delay time is 2-6 s.

6. The hydraulic control system for a variable amplitude cylinder according to claim 1, wherein, The main reversing valve (5) has a Y-shaped middle position function.

7. The hydraulic boom cylinder control system of claim 1, wherein, The controller is further configured to: determine that the main reversing valve (5) is kept in the middle valve position; control the electromagnetic reversing valve (42) to keep in the one-way cut-off valve position so that the bypass oil path (L3) is cut off.

8. The hydraulic control system for a variable amplitude cylinder of claim 1, wherein, The controller is further configured to: determine that the variable amplitude oil cylinder (1) is extended to perform the boom raising action; The electromagnetic directional valve (42) is controlled to be kept in a one-way cut-off valve position, so that the bypass oil passage (L3) is cut off.

9. A tower crane, characterized in that The tower crane comprises a jib and the hydraulic control system of the luffing cylinder according to any one of claims 1-8, and the luffing cylinder (1) is used to drive the jib to lift or lower.

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