阅读说明：本技术 实现工程车辆机构顺序动作的液压系统、方法及工程车辆 (Hydraulic system and method for realizing sequential action of engineering vehicle mechanism and engineering vehicle ) 是由 孙文庆 史继江 秦家升 石立京 李寿鹏 吕建森 于 2019-11-05 设计创作，主要内容包括：本发明公开了一种实现工程车辆机构顺序动作的液压系统、方法及工程车辆,其中,液压系统包括电动机、液压泵、电磁换向阀、顺序阀Ⅰ、液压执行元件Ⅰ、顺序阀Ⅱ和液压执行元件Ⅱ；所述电动机连接液压泵,液压泵出油经电磁换向阀带动液压执行元件Ⅰ、液压执行元件Ⅱ动作,顺序阀Ⅰ串联在液压执行元件Ⅰ大腔油口与电磁换向阀油口液压回路之间,顺序阀Ⅱ串联在液压执行元件Ⅱ大腔油口与电磁换向阀油口液压回路之间。本发明电控部分仅需控制一个电磁换向阀,其他部分由液压控制,实现运动的顺序性和对速度的控制,安全、平稳、可靠、成本低,适于普及与推广。(The invention discloses a hydraulic system, a method and an engineering vehicle for realizing sequential actions of an engineering vehicle mechanism, wherein the hydraulic system comprises a motor, a hydraulic pump, an electromagnetic directional valve, a sequence valve I, a hydraulic actuating element I, a sequence valve II and a hydraulic actuating element II; the motor is connected with a hydraulic pump, the oil output of the hydraulic pump drives a hydraulic actuating element I and a hydraulic actuating element II to act through an electromagnetic directional valve, a sequence valve I is connected between a large cavity oil port of the hydraulic actuating element I and an oil port hydraulic loop of the electromagnetic directional valve in series, and a sequence valve II is connected between a large cavity oil port of the hydraulic actuating element II and the oil port hydraulic loop of the electromagnetic directional valve in series. The electric control part of the invention only needs to control one electromagnetic directional valve, and other parts are controlled by hydraulic pressure, thus realizing the sequence of movement and the control of speed, being safe, stable, reliable and low in cost, and being suitable for popularization and promotion.)

1. The utility model provides a realize hydraulic system of engineering vehicle mechanism sequence action which characterized in that: the hydraulic system comprises a motor, a hydraulic pump, an electromagnetic directional valve, a sequence valve I, a hydraulic actuating element I, a sequence valve II and a hydraulic actuating element II;

the motor is connected with a hydraulic pump, the oil output of the hydraulic pump drives a hydraulic actuating element I and a hydraulic actuating element II to act through an electromagnetic directional valve, a sequence valve I is connected between a large cavity oil port of the hydraulic actuating element I and an oil port hydraulic loop of the electromagnetic directional valve in series, and a sequence valve II is connected between a large cavity oil port of the hydraulic actuating element II and the oil port hydraulic loop of the electromagnetic directional valve in series.

2. The hydraulic system for realizing sequential actions of the mechanism of the engineering vehicle as claimed in claim 1, wherein: the hydraulic actuating element I is a locking oil cylinder, and the hydraulic actuating element II is a lifting oil cylinder and is used for controlling the sequential movement of the centralized filling mechanism of the hydraulic excavator;

the opening pressure of the sequence valve I is greater than the oil inlet pressure of the small cavity when the oil cylinder rod of the lifting oil cylinder is retracted, so that the sequence control function of controlling the first completion of the oil cylinder rod retracting action of the lifting oil cylinder and then the completion of the oil cylinder rod extending action of the locking oil cylinder is realized;

the opening pressure of the sequence valve II is greater than the small-cavity oil inlet pressure when the oil cylinder rod of the locking oil cylinder is retracted, so that the sequence control function of controlling the first completion of the retraction action of the oil cylinder rod of the locking oil cylinder and then the completion of the extension action of the oil cylinder rod of the lifting oil cylinder is realized.

3. The hydraulic system for realizing sequential actions of the mechanism of the engineering vehicle as claimed in claim 1, wherein: the hydraulic actuating element I is a locking oil cylinder, and the hydraulic actuating element II is a hydraulic motor and is used for controlling the sequential movement of the boarding ladder mechanism of the hydraulic excavator;

the opening pressure of the sequence valve I is greater than the pressure of an oil port on the right side of the hydraulic motor, so that the sequence control function of firstly completing the action of rotating and recovering the boarding ladder by the hydraulic motor and then completing the extending action of an oil cylinder rod of the locking oil cylinder is realized;

the opening pressure of the sequence valve II is larger than the small-cavity oil inlet pressure when the oil cylinder rod of the locking oil cylinder is retracted, so that the sequence control function of controlling the locking oil cylinder rod to retract firstly and then completing the action of rotating the hydraulic motor to release the boarding ladder is achieved.

4. The hydraulic system for realizing sequential actions of the mechanism of the engineering vehicle as claimed in claim 1, wherein: the hydraulic system further comprises a balance valve, the balance valve is connected in series between the oil port of the hydraulic actuating element II and the oil port hydraulic circuit of the electromagnetic directional valve, and the balance valve prevents the oil port of the hydraulic actuating element II from being emptied and controls the working speed of the hydraulic actuating element II.

5. The hydraulic system for realizing sequential actions of the mechanism of the engineering vehicle as claimed in claim 1, wherein: the hydraulic system also comprises an overflow valve which is connected in series between the oil outlet and the oil return way of the hydraulic pump.

6. The hydraulic system for realizing sequential actions of the mechanism of the engineering vehicle as claimed in claim 1, wherein: the electromagnetic directional valve adopts a three-position four-way electromagnetic directional valve.

7. Engineering vehicle, its characterized in that: the hydraulic system for realizing the sequential actions of the mechanisms of the engineering vehicle, which is disclosed by any one of claims 1 to 6.

8. The work vehicle of claim 7, wherein: the work vehicle includes a hydraulic excavator.

9. The method for realizing the hydraulic system of the sequential action of the mechanism of the engineering vehicle as claimed in claim 2, characterized in that: when the centralized filling operation is needed, the tray needs to be loosened firstly and then put down, the left side of the electromagnetic directional valve is electrified and works in a left-position machine, hydraulic oil output by a hydraulic pump enters a small cavity of a locking oil cylinder through a left-side oil duct, the locking oil cylinder returns oil in a large cavity, the locking oil cylinder gradually loosens the locking of the tray until the tray is completely loosened, the opening pressure of a sequence valve II is greater than the oil inlet pressure of the small cavity when an oil cylinder rod of the locking oil cylinder is retracted, the pressure entering the small cavity of the locking oil cylinder is continuously increased to reach the opening value of the sequence valve II, the oil inlet and the oil return of the large cavity oil port of the lifting oil cylinder are carried out, and the putting down operation;

when the centralized filling operation is completed, the tray needs to be lifted firstly and then locked, the right side of the electromagnetic directional valve is powered at the moment, the tray works at a right position, hydraulic oil output by a hydraulic pump enters a small cavity of the lifting oil cylinder through an oil duct, oil is returned from a large cavity of the lifting oil cylinder, the lifting operation of the tray is realized until the tray is completely lifted, the opening pressure of the sequence valve I is greater than the oil inlet pressure of the small cavity when an oil cylinder rod of the lifting oil cylinder is retracted, the pressure entering the small cavity of the lifting oil cylinder is continuously increased to reach the opening value of the sequence valve I, the oil inlet and the oil return of an oil port of the large cavity of the locking oil cylinder are locked, and the.

10. The method for realizing the hydraulic system of the sequential action of the mechanism of the engineering vehicle as claimed in claim 3, characterized in that: when a person needs to board the vehicle, the boarding ladder needs to be put down, the locking mechanism needs to be firstly released and then put down by the boarding ladder, the left side of the electromagnetic directional valve is electrified and works on a left-position machine, hydraulic oil output by the hydraulic pump enters a small cavity of the locking oil cylinder through a left-side oil duct, oil returns from a large cavity of the locking oil cylinder, the locking oil cylinder gradually releases locking of the boarding ladder until the boarding ladder is completely released, the opening pressure of a sequence valve II is greater than the oil inlet pressure of the small cavity when an oil cylinder rod of the locking oil cylinder is retracted, the pressure entering the small cavity of the locking oil cylinder is continuously increased to reach the opening value of the sequence valve II, an oil inlet port on the left side of the hydraulic motor and an oil return port on the right;

when the boarding ladder needs to be lifted, the boarding ladder needs to be lifted firstly and then locked, the right side of the electromagnetic directional valve is electrified at the moment, the work is in a right-position function, hydraulic oil output by a hydraulic pump enters a right-side oil port and a left-side oil port of a hydraulic motor through an oil duct to return oil, the lifting operation of the boarding ladder is realized, the opening pressure of a sequence valve I is greater than the pressure of the right-side oil port of the hydraulic motor until the boarding ladder is completely lifted, the pressure of the right-side oil port of the hydraulic motor continues to increase to reach the opening value of the sequence valve I, the oil inlet of a large cavity oil port and the oil return of a.

Technical Field

The invention relates to a hydraulic system for realizing sequential actions of an engineering vehicle mechanism, belonging to the field of hydraulic systems.

Background

The movement of some mechanisms of the hydraulic excavator often has a sequence, and the control of the sequence directly influences the movement effect and the product performance. The joint of the relative movement of each mechanism of the hydraulic excavator needs to be lubricated and maintained regularly, and particularly for large excavators, the lubricating oil requirement is large, the vehicle body is large, and the filling difficulty is large, so that a centralized filling mechanism is often designed for the hydraulic excavator, a filling port and a filling pipeline of the lubricating oil are centralized on a tray, and when filling is not needed, the tray is fixedly locked on the bottom surface of the excavator shed by a locking oil cylinder; when the tray needs to be filled, the locking oil cylinder loosens the tray, and the lifting oil cylinder puts down the tray to realize centralized filling operation; after filling, the lifting oil cylinder lifts the tray, and the locking oil cylinder locks and fixes the tray. The large hydraulic excavator is provided with a boarding ladder, and the boarding ladder also has the problems of locking and sequential actions of lifting. However, the scheme of electrically controlling a plurality of electromagnetic valves in the existing control scheme has the problems of high cost, high control difficulty, poor motion coordination, high control response rigidity and the like.

Disclosure of Invention

In view of this, the present invention aims to provide a hydraulic system for implementing locking and lifting sequential actions of an engineering vehicle mechanism, wherein an electric control part only needs to control one electromagnetic directional valve, and other parts are controlled by hydraulic pressure, so that sequential movement and speed control are implemented, and the hydraulic system is safe, stable, reliable, low in cost and suitable for popularization and promotion.

In order to solve the technical problem, the technical scheme of the invention is realized as follows:

a hydraulic system for realizing sequential actions of an engineering vehicle mechanism comprises a motor, a hydraulic pump, an electromagnetic directional valve, a sequence valve I, a hydraulic execution element I, a sequence valve II and a hydraulic execution element II; the motor is connected with a hydraulic pump, the oil output of the hydraulic pump drives a hydraulic actuating element I and a hydraulic actuating element II to act through an electromagnetic directional valve, a sequence valve I is connected between a large cavity oil port of the hydraulic actuating element I and an oil port hydraulic loop of the electromagnetic directional valve in series, and a sequence valve II is connected between a large cavity oil port of the hydraulic actuating element II and the oil port hydraulic loop of the electromagnetic directional valve in series.

Further, the hydraulic actuating element I is a locking oil cylinder, and the hydraulic actuating element II is a lifting oil cylinder and is used for controlling the sequential movement of the centralized filling mechanism of the hydraulic excavator; the opening pressure of the sequence valve I is greater than the oil inlet pressure of the small cavity when the oil cylinder rod of the lifting oil cylinder is retracted, so that the sequence control function of controlling the first completion of the oil cylinder rod retracting action of the lifting oil cylinder and then the completion of the oil cylinder rod extending action of the locking oil cylinder is realized; the opening pressure of the sequence valve II is greater than the small-cavity oil inlet pressure when the oil cylinder rod of the locking oil cylinder is retracted, so that the sequence control function of controlling the first completion of the retraction action of the oil cylinder rod of the locking oil cylinder and then the completion of the extension action of the oil cylinder rod of the lifting oil cylinder is realized.

Further, the hydraulic actuating element I is a locking oil cylinder, and the hydraulic actuating element II is a hydraulic motor and is used for controlling the sequential movement of the boarding ladder mechanism of the hydraulic excavator; the opening pressure of the sequence valve I is greater than the pressure of an oil port on the right side of the hydraulic motor, so that the sequence control function of firstly completing the action of rotating and recovering the boarding ladder by the hydraulic motor and then completing the extending action of an oil cylinder rod of the locking oil cylinder is realized; the opening pressure of the sequence valve II is larger than the small-cavity oil inlet pressure when the oil cylinder rod of the locking oil cylinder is retracted, so that the sequence control function of controlling the locking oil cylinder rod to retract firstly and then completing the action of rotating the hydraulic motor to release the boarding ladder is achieved.

Furthermore, the hydraulic system also comprises a balance valve, the balance valve is connected in series between the oil port of the hydraulic actuating element II and the hydraulic loop of the oil port of the electromagnetic directional valve, and the balance valve prevents the oil port of the hydraulic actuating element II from being sucked empty and controls the working speed of the hydraulic actuating element II.

Furthermore, the hydraulic system also comprises an overflow valve which is connected in series between the oil outlet and the oil return way of the hydraulic pump.

Furthermore, the electromagnetic directional valve adopts a three-position four-way electromagnetic directional valve.

The engineering vehicle is provided with the hydraulic system for realizing the sequential action of the engineering vehicle mechanism.

Further, the work vehicle includes a hydraulic excavator.

Compared with the prior art, the hydraulic system for realizing the locking and lifting sequential actions of the hydraulic engineering vehicle mechanism has the following advantages:

(1) the hydraulic system for realizing the locking and lifting sequential actions of the engineering vehicle mechanism only needs to electrically control one three-position four-way electromagnetic directional valve, and the electric control part is simple and convenient and has low cost.

(2) According to the hydraulic system for realizing locking and lifting sequential actions of the engineering vehicle mechanism, the action sequence of the locking oil cylinder and the lifting oil cylinder is realized by setting different pressures of the sequence valve I and the sequence valve II, compared with the action sequence controlled by the electric control solenoid valve, the hydraulic system effectively avoids pressure impact and incongruity, is safer and more reliable in control and more stable in action, and is suitable for popularization and use.

(3) According to the hydraulic system for realizing locking and lifting sequential actions of the engineering vehicle mechanism, the balance valve is used for effectively preventing the large cavity of the lifting oil cylinder from being sucked to be empty and controlling the descending speed, and the safety and the reliability are high.

(4) According to the hydraulic system for realizing the locking and lifting sequential actions of the engineering vehicle mechanism, the overflow valve is used for effectively preventing the system from being damaged due to overhigh output pressure of the hydraulic pump.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a hydraulic system for implementing sequential locking and raising and lowering actions of a hydraulic excavator mechanism according to the present invention;

FIG. 2 is a schematic diagram of the movement of a centralized charging mechanism of a hydraulic excavator to provide a further understanding of the present invention;

FIG. 3 is a schematic structural diagram of a hydraulic system for implementing locking and sequential lifting actions of a hydraulic excavator boarding ladder mechanism according to the present invention;

FIG. 4 is a schematic diagram of the movement of the hydraulic excavator boarding ladder mechanism that provides a further understanding of the present invention;

in the figure: a motor 1; a hydraulic pump 2; a three-position four-way electromagnetic directional valve 3; a sequence valve I4; locking the oil cylinder 5; a sequence valve II 6; a lift cylinder 7; a hydraulic motor 7 a; a balancing valve 8; and an overflow valve 9.

Detailed Description

In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are only some, but not all embodiments of the invention. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In the prior art, a centralized filling mechanism is designed for a hydraulic excavator, a filling port and a filling pipeline of lubricating oil are centralized on a tray, and the tray is fixedly locked on the bottom surface of an excavator shed by a locking oil cylinder when filling is not needed; when the tray needs to be filled, the locking oil cylinder loosens the tray, and the lifting oil cylinder puts down the tray to realize centralized filling operation; after filling, the lifting oil cylinder lifts the tray, and the locking oil cylinder locks and fixes the tray. The large hydraulic excavator is provided with a boarding ladder, and the boarding ladder also has the problems of locking and sequential actions of lifting. Therefore, the invention provides a hydraulic system for realizing locking and lifting sequential actions of a hydraulic excavator mechanism, an electric control part only needs to control one electromagnetic directional valve, and other parts are controlled by hydraulic pressure to realize the sequential movement and speed control. The specific scheme is as follows:

a hydraulic system for realizing sequential actions of an engineering vehicle mechanism comprises a motor 1, a hydraulic pump 2, an electromagnetic directional valve, a sequence valve I4, a hydraulic actuating element I, a sequence valve II 6 and a hydraulic actuating element II; the motor 1 is connected with the hydraulic pump 2, the oil output of the hydraulic pump 2 drives the hydraulic actuating element I and the hydraulic actuating element II to act through the electromagnetic directional valve, the sequence valve I4 is connected between the oil port of the large cavity of the hydraulic actuating element I and the hydraulic loop of the oil port of the electromagnetic directional valve in series, and the sequence valve II 6 is connected between the oil port of the large cavity of the hydraulic actuating element II and the hydraulic loop of the oil port of the electromagnetic directional valve in series.

As shown in fig. 1, a hydraulic actuator i is a locking cylinder 5, and a hydraulic actuator ii is a lifting cylinder 7, and is used for controlling the sequential movement of a centralized filling mechanism of a hydraulic excavator; the opening pressure of the sequence valve I4 is greater than the oil inlet pressure of the small cavity when the oil cylinder rod of the lifting oil cylinder 7 is retracted, so that the sequence control function of controlling the oil cylinder rod of the lifting oil cylinder 7 to be retracted and then controlling the oil cylinder rod of the locking oil cylinder 5 to be extended is achieved; the opening pressure of the sequence valve II 6 is greater than the oil inlet pressure of the small cavity when the oil cylinder rod of the locking oil cylinder 5 is retracted, so that the sequence control function of controlling the oil cylinder rod of the locking oil cylinder 5 to be retracted and then controlling the oil cylinder rod of the lifting oil cylinder 7 to be extended is achieved.

Further scheme: the hydraulic system further comprises a balance valve 8, the balance valve 8 is connected in series between the oil port of the lifting oil cylinder 7 and the oil port hydraulic circuit of the electromagnetic directional valve, the balance valve 8 sets a pressure value according to working occasions, and the balance valve 8 is used for effectively preventing the oil inlet cavity from being sucked to be empty and controlling descending speed, so that the speed of a mechanism controlled by the oil cylinder rod of the lifting oil cylinder 7 is limited to be stable, safe and reliable.

Further scheme: the hydraulic system also comprises an overflow valve 9, and the overflow valve 9 is connected in series between the oil outlet and the oil return path of the hydraulic pump 2.

As shown in fig. 1 and 2, the motor 1 supplies power to the hydraulic pump 2, the hydraulic pump 2 outputs hydraulic oil, when the centralized filling operation is not performed, the tray is locked and fixed on the bottom surface of the excavator shed, the three-position four-way electromagnetic directional valve 3 works in a middle position function, and the hydraulic oil returns through the overflow valve 9. When the centralized filling operation is needed, the tray needs to be loosened and then put down firstly by the locking mechanism, the left side of the three-position four-way electromagnetic directional valve 3 is electrified and works on a left-position machine, hydraulic oil output by the hydraulic pump 2 enters the small cavity of the locking oil cylinder 5 through the left oil passage, oil returns from the large cavity of the locking oil cylinder 5, the locking oil cylinder 5 gradually loosens the locking of the tray until the tray is completely loosened, the opening pressure of the sequence valve II 6 is greater than the oil inlet pressure of the small cavity when the oil cylinder rod of the locking oil cylinder 5 is retracted, the pressure entering the small cavity of the locking oil cylinder 5 is continuously increased to reach the opening value of the sequence valve II 6, the oil inlet of the oil port of the large cavity of the lifting oil cylinder 7 and the oil return from the small cavity, the putting down operation of the tray by the lifting oil cylinder 7 is executed, and the balance valve 8 effectively prevents the large cavity of the lifting. When the centralized filling operation is completed, the tray needs to be lifted firstly and then locked, the right side of the three-position four-way electromagnetic directional valve 3 is electrified and works on a right machine function, hydraulic oil output by the hydraulic pump 2 enters the small cavity of the lifting oil cylinder 7 through an oil duct, oil returns from the large cavity of the lifting oil cylinder 7, the tray is lifted until the tray is completely lifted, the opening pressure of the sequence valve I4 is greater than the oil inlet pressure of the small cavity when the oil cylinder rod of the lifting oil cylinder 7 is retracted, the pressure entering the small cavity of the lifting oil cylinder 7 is continuously increased to reach the opening value of the sequence valve I4, the oil inlet of the large cavity oil port of the locking oil cylinder 5 and the oil return of the small cavity are achieved, and the locking operation of the locking.

The different pressure settings of the sequence valve I4 and the sequence valve II 6 realize that the action sequence of the locking oil cylinder 5 and the lifting oil cylinder 7 effectively avoids pressure impact and incoordination, is safer and more reliable in control, has more stable action, and is suitable for popularization and application.

As shown in fig. 3, the hydraulic actuator i is a locking cylinder 5, and the hydraulic actuator ii is a hydraulic motor 7a, which is used for controlling the sequential movement of the boarding ladder mechanism of the hydraulic excavator; the opening pressure of the sequence valve I4 is greater than the pressure of an oil port on the right side of the hydraulic motor 7a, so that the sequence control function of controlling the hydraulic motor 7a to rotate and recover the boarding ladder and then controlling the locking oil cylinder 5 to stretch out the oil cylinder rod is achieved; the opening pressure of the sequence valve II 6 is greater than the small-cavity oil inlet pressure when the oil cylinder rod of the locking oil cylinder 5 is retracted, so that the sequence control function of controlling the locking oil cylinder 5 to retract the oil cylinder rod and then controlling the hydraulic motor 7a to rotate to release the boarding ladder is achieved.

Further scheme: the hydraulic system also comprises a balance valve 8, and the balance valve 8 is connected in series between an oil port of the hydraulic motor 7a and a hydraulic circuit of an oil port of the electromagnetic directional valve. The pressure value is set by the balance valve 8 according to the working occasion, and the use of the balance valve 8 effectively prevents the air suction of the oil inlet cavity and controls the descending speed, so that the speed of a mechanism controlled by the hydraulic motor 7a is limited to be stable, safe and reliable.

Further scheme: the hydraulic system also comprises an overflow valve 9, and the overflow valve 9 is connected in series between the oil outlet and the oil return path of the hydraulic pump 2.

As shown in fig. 3 and 4, the system can be used for controlling the sequential movement of the boarding ladder mechanism of the hydraulic excavator, the motor 1 supplies power to the hydraulic pump 2, the hydraulic pump 2 outputs hydraulic oil, when the boarding ladder is not operated, the boarding ladder is locked and fixed, the three-position four-way electromagnetic directional valve 3 works in a middle position function, and the hydraulic oil returns through the overflow valve 9. When a person needs to board the vehicle, the boarding ladder needs to be put down, the locking mechanism of the boarding ladder needs to be firstly released and then put down, the left side of the three-position four-way electromagnetic directional valve 3 is electrified and works on a left-position machine, hydraulic oil output by the hydraulic pump 2 enters the small cavity of the locking oil cylinder 5 through the left oil duct, the large cavity of the locking oil cylinder 5 returns oil, the locking oil cylinder 5 gradually releases locking of the boarding ladder until the boarding ladder is completely released, the opening pressure of the sequence valve II 6 is greater than the oil inlet pressure of the small cavity when the oil cylinder rod of the locking oil cylinder 5 is retracted, the pressure entering the small cavity of the locking oil cylinder 5 is continuously increased to reach the opening value of the sequence valve II 6, and the left oil port of, the right oil port returns oil, the hydraulic motor 7a is used for lowering the boarding ladder, the balance valve 8 effectively prevents the oil inlet of the hydraulic motor 7a from sucking air and controls the speed of the boarding ladder when the boarding ladder is lowered, and the safety and the reliability are high. When the boarding ladder needs to be lifted, the boarding ladder needs to be lifted firstly and then locked, the right side of the three-position four-way electromagnetic directional valve 3 is electrified and works at a right machine function, hydraulic oil output by the hydraulic pump 2 enters a right oil port and a left oil port of the hydraulic motor 7a through oil ducts to return oil, the lifting operation of the boarding ladder is realized, the opening pressure of the sequence valve I4 is greater than the pressure of the right oil port of the hydraulic motor 7a until the boarding ladder is completely lifted, the pressure of the right oil port of the hydraulic motor 7a continues to increase to reach the opening value of the sequence valve I4, the large cavity oil port of the locking oil cylinder 5 is used for feeding oil and returning oil, and the locking operation of the locking oil cylinder 5 on the boarding.

The different pressure settings of the sequence valve I4 and the sequence valve II 6 realize that the action sequence of the locking oil cylinder 5 and the hydraulic motor 7a effectively avoids pressure impact and incoordination, is safer and more reliable in control, has more stable action, and is suitable for popularization and popularization.

In conclusion, the hydraulic system for realizing the locking and lifting sequential actions of the engineering vehicle mechanism realizes the sequential actions of the locking oil cylinder and the lifting oil cylinder, and simultaneously realizes the speed control of the descending action, so that the engineering vehicle mechanism runs safely, stably and reliably.

The invention also provides an engineering vehicle which is provided with the hydraulic system for realizing the sequential action of the engineering vehicle mechanism. Wherein, the engineering vehicle comprises a hydraulic excavator.

While the present application has been described with reference to exemplary embodiments, it is understood that the terminology used is intended to be in the nature of words of description and illustration, rather than of limitation. As the present application may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.