Hydraulic control circuit for main and tail rotor control and helicopter landing gear

Abstract

The application relates to a hydraulic control circuit of a main and passive differential control and a helicopter landing gear, and belongs to the field of mechanical design. In order to solve the problem that the terrain adaptability of the traditional landing gear is insufficient, a parking apron needs to be built in advance on a complex terrain, and the terrain adaptability of the helicopter cannot be improved. The landing leg unit is matched with the hydraulic control circuit, so that various control modes of the landing gear can be realized, such as active control of the landing leg unit, passive differential control between the landing leg units, active differential control between the front and rear landing leg units, when the landing leg units in each group are two, active differential control between the two landing leg units in the group, so that the helicopter can change the structural posture of the landing leg unit according to the terrain condition, and the helicopter can keep the body horizontal and stable when landing on a rugged or inclined ground. The application is mainly used for the landing of the helicopter on a complex terrain.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of mechanical design, and particularly relates to a hydraulic control circuit of active and passive differential control and a helicopter landing gear. BACKGROUND

[0002] As a vertical take-off and landing aircraft, helicopters are often used for tasks in complex terrain environments, such as mountain rescue, terrain survey, etc. However, the structure of the traditional helicopter landing gear is relatively fixed, such as skid type, front three-point type and rear three-point type, etc. These traditional landing gears have insufficient terrain adaptability, and need to build a landing pad in advance in complex terrain, which cannot improve the terrain adaptability of the helicopter. SUMMARY

[0003] Therefore, the present application provides a hydraulic control circuit of active and passive differential control and a helicopter landing gear, which can select active control mode, passive differential control mode or active differential control mode for landing according to the use scene, so as to increase the terrain adaptability and stability of the helicopter during landing.

[0004] The technical scheme adopted by the present application to solve the above technical problems is as follows:

[0005] A hydraulic control circuit of active and passive differential control, comprising a hydraulic control unit, the hydraulic control unit is provided with N, N>=3, each hydraulic control unit corresponds to one landing leg unit, and is provided as one landing leg control mechanism with the landing leg unit, the N landing leg control mechanisms are divided into M groups and are arranged side by side, M>=2, each landing leg unit is provided with a first actuator cylinder;

[0006] Each hydraulic control unit comprises a first liquid inlet pipe, a first liquid outlet pipe, an active control oil way, a passive control oil way, a first electro-hydraulic servo valve and an electromagnetic reversing valve for switching the active control oil way and the passive control oil way, one end of the first liquid inlet pipe is communicated with the rod cavity of the first actuator cylinder, and the other end is communicated with the electromagnetic reversing valve, one end of the first liquid outlet pipe is communicated with the rodless cavity of the first actuator cylinder, and the other end is communicated with the first liquid outlet pipe in the remaining hydraulic control unit, the first liquid inlet pipe and the first liquid outlet pipe are both communicated with the first electro-hydraulic servo valve, the first electro-hydraulic servo valve can switch the oil way between the rod cavity and the rodless cavity of the first actuator cylinder and the first liquid inlet pipe and the first liquid outlet pipe; one end of the passive control oil way is communicated with the electromagnetic reversing valve, and the other end is communicated with the passive control oil way in the remaining hydraulic control unit; when the electromagnetic reversing valve controls the passive control oil way to be communicated with the first liquid inlet pipe, each first actuator cylinder is connected into a closed loop through the first liquid inlet pipe, the passive control oil way and the first liquid outlet pipe, so as to realize passive differential control between each first actuator cylinder; the active control oil way and the passive control oil way are designed in parallel, and the active control oil way is communicated with the first liquid inlet pipe through the electromagnetic reversing valve;

[0007] The second differential oil pump is arranged between the two adjacent groups of landing leg control mechanisms, and is connected with the active control oil paths in the two adjacent groups of landing leg control mechanisms, so that when the electromagnetic reversing valves in the two adjacent groups are controlled to connect the active control oil paths with the first liquid inlet pipe, a closed loop is formed between the first actuators in the two groups via the first liquid inlet pipe, the first liquid outlet pipe and the active control oil paths, the second differential oil pump is started, and active differential control is realized between the two groups of landing leg control mechanisms.

[0008] In addition, the helicopter landing gear of the active and passive differential control is also provided by using the hydraulic control circuit to connect each landing leg unit, and the helicopter landing gear comprises a landing gear body, a landing leg unit and a hydraulic control circuit, and the landing leg unit is installed on the landing gear body. The landing leg unit can adopt a single degree of freedom structure, and can also adopt a two degree of freedom structure to increase the adaptability of the leg to the ground.

[0009] Compared with the prior art, the helicopter landing gear has the following beneficial effects:

[0010] 1. The landing leg unit of the helicopter landing gear is matched with the hydraulic control circuit, and various control modes of the landing gear can be realized, such as active control of the landing leg unit, passive differential control between the landing leg units, active differential control between the two groups of landing leg units, active differential control between the two landing leg units in each group when the number of landing leg units in each group is two, so that the helicopter can change the structural posture of the landing leg unit according to the terrain conditions, and the helicopter can keep horizontal and stable when landing on rugged or inclined ground.

[0011] 2. In the active control mode, the oil tank actively supplies oil to make the actuators work and realize precise control. In the passive differential control mode, the oil tank does not supply oil, and the passive flow of oil between the actuators is relied on to realize the cooperative differential between the landing legs, thereby saving energy and simplifying the structure. In the active differential control mode, the oil tank does not supply oil, and the active flow of oil between the actuators is relied on to realize the active differential control between the landing legs, so that the posture of each leg can be flexibly adjusted to adapt to complex terrain.

[0012] 3. The hydraulic control circuit of the helicopter landing gear can be compatible with different degrees of freedom and different numbers of landing gear legs, and has good flexibility and expansibility. This makes it more convenient to adjust and optimize the landing gear system of the helicopter when facing different task requirements and use scenarios, without the need for large-scale redesign of the hydraulic control circuit. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings are part of the present application and serve to provide a further understanding of the present application.

[0014] Figure 1Structure schematic diagram for landing leg unit adopting single degree of freedom structure, a is the first configuration of single degree of freedom landing leg unit, b is the second configuration of single degree of freedom landing leg unit.

[0015] Figure 2 Structure schematic diagram for landing leg unit adopting two degrees of freedom structure, a is the first configuration of two degrees of freedom landing leg unit, b is the second configuration of two degrees of freedom landing leg unit, c is the third configuration of two degrees of freedom landing leg unit.

[0016] Figure 3 Hydraulic control schematic diagram for landing gear of embodiment 7.

[0017] Figure 4 Hydraulic control schematic diagram for landing gear of embodiment 8.

[0018] Figure 5 Hydraulic control schematic diagram for landing gear in embodiment 8 adopting active control mode.

[0019] Figure 6 Hydraulic control schematic diagram for landing gear in embodiment 8 adopting passive differential control mode.

[0020] Figure 7 Hydraulic control schematic diagram for landing gear in embodiment 8 adopting left-right active differential control mode.

[0021] Figure 8 Hydraulic control schematic diagram for landing gear in embodiment 8 adopting front-rear active differential control mode.

[0022] Figure 9 Hydraulic control schematic diagram for landing gear of embodiment 1.

[0023] Figure 10 Hydraulic control schematic diagram for landing gear of embodiment 2.

[0024] Figure 11 Hydraulic control schematic diagram for landing gear in embodiment 2 adopting active control mode.

[0025] Figure 12 Hydraulic control schematic diagram for landing gear in embodiment 2 adopting passive differential control mode.

[0026] Figure 13 Hydraulic control schematic diagram for landing gear in embodiment 2 adopting left-right active differential control mode.

[0027] Figure 14 Hydraulic control schematic diagram for landing gear in embodiment 2 adopting front-rear active differential control mode.

[0028] Figure 15Hydraulic control schematic for the landing gear of Example 3.

[0029] Figure 16 Hydraulic control schematic for the landing gear of Example 4.

[0030] Figure 17 Hydraulic control schematic for the landing gear of Example 4 using active control mode.

[0031] Figure 18 Hydraulic control schematic for the landing gear of Example 4 using passive differential control mode.

[0032] Figure 19 Hydraulic control schematic for the landing gear of Example 4 using left-right active differential control mode.

[0033] Figure 20 Hydraulic control schematic for the landing gear of Example 4 using active differential control mode for the front three groups of landing legs control mechanisms.

[0034] Figure 21 Hydraulic control schematic for the landing gear of Example 4 using front-back active differential control mode for the adjacent two groups of landing legs control mechanisms.

[0035] Figure 22 Hydraulic control schematic for the landing gear of Example 5.

[0036] Figure 23 Hydraulic control schematic for the landing gear of Example 6.

[0037] Figure 24 Hydraulic control schematic for the landing gear of Example 6 using active control mode.

[0038] Figure 25 Hydraulic control schematic for the landing gear of Example 6 using passive differential control mode.

[0039] Figure 26 Hydraulic control schematic for the landing gear of Example 6 using active differential control mode for the left front leg and the right rear leg.

[0040] Figure 27 Hydraulic control schematic for the landing gear of Example 6 using active differential control mode for the left rear leg and the right front leg.

[0041] Explanation of reference signs: 1-first actuating cylinder; 2-first connecting rod; 3-supporting rod; 4-first landing leg; 5-second actuating cylinder; 6-second connecting rod; 7-third connecting rod; 8-second landing leg; 9-fourth connecting rod; 10-fifth connecting rod; 11-third landing leg; 12-oil tank; 13-main oil path; 14-first branch oil path; 15-second branch oil path; 16-closed oil valve; 17-liquid level gauge; 18-air filter; 19-one-way hydraulic pump; 20-hydraulic oil filter; 21-one-way valve; 22-accumulator; 23-pressure gauge; 24-second differential oil pump; 25-first differential oil pump; 26-first series oil path; 27-parallel oil path; 28-second series oil path; 29-first liquid inlet pipe; 30-first liquid outlet pipe; 31-active control oil path; 32-passive control oil path; 33-first electro-hydraulic servo valve; 34-electromagnetic reversing valve; 35-second liquid inlet pipe; 36-second liquid outlet pipe; 37-second electro-hydraulic servo valve; 38-excess flow valve; 39-oil return valve; 40-on-off valve. DETAILED DESCRIPTION

[0042] The invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] As shown in Figures 1 to 27 , the embodiment provides a main and passive differential control helicopter landing gear, which comprises a landing leg unit and a hydraulic control circuit. As shown in Figure 1 and Figure 2 , the landing leg unit is provided with N, and each landing leg unit can adopt a single degree of freedom structure or a two degree of freedom structure. The landing gear can use the corresponding landing leg configuration according to actual needs.

[0044] As shown in Figure 1 , when the landing leg unit adopts a single degree of freedom structure, an actuating cylinder is designed, in combination with Figure 1 a, the cylinder body of the first actuating cylinder 1 is connected to the landing gear body, the piston rod of the first actuating cylinder 1 is directed towards the ground, and the first actuating cylinder 1 is used as a landing leg. When the helicopter lands, the piston rod of the first actuating cylinder 1 is extended and contacts the ground to achieve the purpose of landing the helicopter. In combination with Figure 1b, the actuating cylinder can also be used with connecting rods to drive the swing of the landing leg. The landing leg unit further comprises a first connecting rod 2, a support rod 3 and a first landing leg 4, the first landing leg 4 being a bent rod, one end of the first connecting rod 2 being hingedly connected to the landing gear body, the other end being movably connected to the top end of the first landing leg 4, one end of the support rod 3 being hingedly connected to the landing gear body, the other end being hingedly connected to the bending position of the first landing leg 4, the cylinder body of the first actuating cylinder 1 being hingedly connected to the landing gear body, the end of the piston rod of the first actuating cylinder 1 being hingedly connected to the connecting position of the first connecting rod 2 and the first landing leg 4, to drive the swing of the first landing leg 4. The configuration of this kind of landing leg unit utilizes the principle of lever. When the piston rod of the first actuating cylinder 1 is retracted, the piston rod of the first actuating cylinder 1 pulls the first landing leg 4 to swing outward around the other end of the support rod 3. When the piston rod of the first actuating cylinder 1 is extended, the piston rod of the first actuating cylinder 1 pushes the first landing leg 4 to swing inward around the other end of the support rod 3. That is, the posture of the landing leg can be adjusted by the extension and retraction of the piston rod of the first actuating cylinder 1.

[0045] As shown in Figure 2 , when the landing leg unit adopts a two-degree-of-freedom structure, two actuating cylinders are designed. In combination Figure 2 a, the two actuating cylinders are connected in series, the second actuating cylinder 5 is used as a side swing leg, and the first actuating cylinder 1 is used as a lifting leg, and the first actuating cylinder 1 and the second actuating cylinder 5 are connected in series as a whole to form a landing leg. Specifically, the cylinder body of the second actuating cylinder 5 is connected to the landing gear body, and the end of the piston rod of the second actuating cylinder 5 is connected to the cylinder body of the first actuating cylinder 1. During landing of the helicopter, the second actuating cylinder 5 can drive the first actuating cylinder 1 to swing sideways, increasing the flexibility of the leg, and the extension and retraction of the piston rod in the first actuating cylinder 1 realizes the extension or retraction of the leg to adapt to the landing of complex terrain. Figure 2 b and Figure 2 c, the two actuating cylinders can also be used with connecting rods to form various configurations to increase the movement posture of the leg. In combination Figure 2 b, the landing leg unit further comprises a second connecting rod 6, a third connecting rod 7 and a second landing leg 8, one end of the second connecting rod 6 being hingedly connected to the landing gear body, the other end being hingedly connected to the middle position of the second landing leg 8, the cylinder body of the first actuating cylinder 1 being hingedly connected to the landing gear body via the third connecting rod 7, the end of the piston rod of the first actuating cylinder 1 being hingedly connected to the middle position of the second connecting rod 6, the cylinder body of the second actuating cylinder 5 being hingedly connected to the third connecting rod 7, and the end of the piston rod of the second actuating cylinder 5 being hingedly connected to the top of the second landing leg 8. When the piston rod of the first actuating cylinder 1 is stationary and the piston rod of the second actuating cylinder 5 is extended, the second actuating cylinder 5 can drive the second landing leg 8 to swing inward, and when the piston rods of the first actuating cylinder 1 and the second actuating cylinder 5 are retracted, the second landing leg 8 can swing outward. Figure 2c, the landing leg unit further comprises a fourth connecting rod 9, a fifth connecting rod 10 and a third landing leg 11, one end of the fourth connecting rod 9 is hingedly connected to the landing gear body, the other end is hingedly connected to the top end of the third landing leg 11, the cylinder body of the first actuating cylinder 1 is hingedly connected to the landing gear body, the end of the piston rod of the first actuating cylinder 1 is hingedly connected to the fourth connecting rod 9, the cylinder body of the second actuating cylinder 5 is hingedly connected to the fourth connecting rod 9, the end of the piston rod of the second actuating cylinder 5 is hingedly connected to one end of the fifth connecting rod 10, the other end of the fifth connecting rod 10 is fixedly connected to the third landing leg 11. When the piston rod of the first actuating cylinder 1 extends and the piston rod of the second actuating cylinder 5 retracts, the third landing leg 11 swings inward, and when the piston rod of the second actuating cylinder 5 extends and the piston rod of the first actuating cylinder 1 retracts, the third landing leg 11 swings outward. As can be seen, through the combined action of the first actuating cylinder 1 and the second actuating cylinder 5, the landing leg can be driven to swing inward or outward, the attitude of the leg part is increased, and the adaptability to complex terrain environment is improved.

[0046] As shown in Figures 3 to 27 the hydraulic control circuit of the embodiment comprises an oil tank 12, a main oil way 13, a first branch oil way 14, a second branch oil way 15 and a closed oil valve 16, one end of the main oil way 13 communicates with the oil tank 12, the other end respectively communicates with the first branch oil way 14 and the second branch oil way 15, the first branch oil way 14 communicates with the first actuating cylinder 1, the oil tank 12 can supply oil to the first actuating cylinder 1 through the main oil way 13 and the first branch oil way 14, and the closed oil valve 16 is arranged on the first branch oil way 14 to control whether the oil tank 12 supplies oil to the first actuating cylinder 1. The second branch oil way 15 communicates with the second actuating cylinder 5, and the oil tank 12 can supply oil to the second actuating cylinder 5 through the main oil way 13 and the second branch oil way 15. A liquid level gauge 17 for monitoring whether the oil amount in the oil tank 12 is maintained within a safe and available range is arranged on the oil tank 12, and an air filter 18 is also installed at the oil filling port of the oil tank 12, which can ensure that the outside air entering the oil tank 12 is clean and free of impurities, so as to ensure the quality of the oil. A one-way hydraulic pump 19, a hydraulic oil filter 20 and a one-way valve 21 are sequentially arranged on the main oil way 13 and in the flow direction of the hydraulic oil, the one-way valve 21 can prevent the hydraulic oil from flowing back to the one-way hydraulic pump 19, and the hydraulic oil filter 20 is used to filter the impurities in the pumped hydraulic oil, and an accumulator 22 and a pressure gauge 23 are further arranged at the output end of the one-way hydraulic pump 19, the accumulator 22 is mainly used to reduce the pressure fluctuation of the hydraulic system, and the pressure gauge 23 is used to monitor the output oil pressure of the one-way hydraulic pump 19 in real time.

[0047] The hydraulic control circuit of the embodiment further comprises N hydraulic control units, each of which corresponds to one landing leg unit and forms a landing leg control mechanism with the landing leg unit, and the N landing leg control mechanisms are divided into M groups, M≥2, and the M groups of landing leg control mechanisms are arranged side by side in front and back and installed at the bottom of the helicopter. Specifically, N can be an odd number or an even number. When N=3, the three landing leg control mechanisms are divided into two groups, one of which is a group of landing leg control mechanisms, and the other two are a group of landing leg control mechanisms arranged side by side in front and back and installed at the bottom of the helicopter, with the group of landing leg control mechanisms in front and the group of landing leg control mechanisms in back. When N=4, the four landing leg control mechanisms are divided into two groups, and the two landing leg control mechanisms in each group are arranged side by side in front and back and installed at the bottom of the helicopter. When N=5, the five landing leg control mechanisms are divided into three groups, one of which is a group of landing leg control mechanisms, and the other four are divided into two groups, and the two groups of landing leg control mechanisms are arranged side by side in front and back and installed at the bottom of the helicopter. When N=6, the six landing leg control mechanisms are divided into three groups, and the two landing leg control mechanisms in each group are arranged side by side in front and back and installed at the bottom of the helicopter. The number of landing leg control mechanisms can be selected as needed, and the above arrangement can increase the stability of the helicopter during landing.

[0048] As Figure 3 , Figure 9 , Figure 15 and Figure 22As shown, when the landing leg unit has a single degree of freedom, each hydraulic control unit in this embodiment includes a first fluid inlet pipe 29, a first fluid outlet pipe 30, an active control oil circuit 31, a passive control oil circuit 32, a first electro-hydraulic servo valve 33, and a solenoid reversing valve 34 for switching between the active control oil circuit 31 and the passive control oil circuit 32. One end of the first fluid inlet pipe 29 connects to the rod chamber of the first actuator 1, and the other end connects to the solenoid reversing valve 34. One end of the first fluid outlet pipe 30 connects to the rodless chamber of the first actuator 1, and the other end connects to the first fluid outlet pipes 30 in the remaining hydraulic control units. To ensure effective locking of the first actuator 1 during landing, on-off valves 40 are installed on both the first fluid inlet pipe 29 and the first fluid outlet pipe 30 of the first actuator 1. These valves are opened during the adaptive adjustment process and locked after landing is complete. The first inlet pipe 29 and the first outlet pipe 30 are both connected to a first electro-hydraulic servo valve 33, which switches the oil circuits between the rodless and rod-operated chambers of the first actuator 1 and the first inlet pipe 29 and first outlet pipe 30. An active control oil circuit 31 and a passive control oil circuit 32 are designed in parallel. The active control oil circuit 31 communicates with the first inlet pipe 29 via a solenoid reversing valve 34. One end of the passive control oil circuit 32 is connected to the solenoid reversing valve 34, and the other end is connected to the passive control oil circuits 32 in the remaining hydraulic control units. When the solenoid reversing valve 34 controls the passive control oil circuit 32 to communicate with the first inlet pipe 29, each first actuator 1 is connected to form a closed circuit via the first inlet pipe 29, the passive control oil circuit 32, and the first outlet pipe 30, achieving passive differential control between the first actuators 1.

[0049] The oil tank 12 is connected to the passive control oil circuit 32 in each hydraulic control unit via the main oil circuit 13 and the first branch oil circuit 14. When the electromagnetic reversing valve 34 controls the first actuator cylinder 1 to be connected to the passive control oil circuit 32, the oil tank 12 supplies oil to each first actuator cylinder 1 to actively control the extension and retraction of the piston rod of each first actuator cylinder 1, thereby realizing active control of the landing gear.

[0050] like Figure 4 、 Figure 10 、 Figure 16 and Figure 23As shown, when the landing leg unit has two degrees of freedom, each hydraulic control unit in this embodiment also includes a second fluid inlet pipe 35, a second fluid outlet pipe 36, and a second electro-hydraulic servo valve 37. One end of the second fluid inlet pipe 35 connects to the rod chamber of the second actuator 5, and the other end connects to the oil tank 12 via the second branch oil circuit 15 and the main oil circuit 13. One end of the second fluid outlet pipe 36 connects to the rodless chamber of the second actuator 5, and the other end connects to the oil tank 12. To ensure effective locking of the second actuator 5 during landing, on-off valves 40 are installed on both the second fluid inlet pipe 35 and the second fluid outlet pipe 36 of the second actuator 5. These valves are opened during the adaptive adjustment process and locked after landing is complete. The second electro-hydraulic servo valve 37 controls the switching between the second fluid inlet pipe 35 and the second fluid outlet pipe 36 and the rodless chamber and the rod chamber of the second actuator 5. During the helicopter landing process, the oil tank 12 supplies oil to the second actuator 5 through the main oil circuit 13 and the second branch oil circuit 15 to actively control the extension and retraction of the piston rod of each second actuator 5, and couples with the first actuator 1 to achieve the change of the landing leg posture.

[0051] like Figures 3 to 27 As shown, the hydraulic control circuit of this embodiment further includes a second differential oil pump 24. The second differential oil pump 24 is provided between two adjacent groups of landing leg control mechanisms. The second differential oil pump 24 is connected to the active control oil circuits 31 in the two adjacent groups of landing leg control mechanisms, respectively. When the solenoid reversing valves 34 in the two adjacent groups control the active control oil circuits 31 to connect with the first liquid inlet pipe 29, the first actuator cylinders 1 in the front and rear groups are connected to form a closed circuit via the first liquid inlet pipe 29, the first liquid outlet pipe 30, and the active control oil circuit 31. The second differential oil pump 24 is activated to achieve active differential control between the front and rear groups of landing leg control mechanisms.

[0052] The active differential control between the front and rear landing leg control mechanisms includes two cases, one is the active differential control between the front group and the rear group, and the other is the active differential control between a landing leg control mechanism in the front group and a landing leg control mechanism in the rear group. When the front group and the rear group are actively differentially controlled, the second differential oil pump 24 is provided, which is in communication with the active control oil path 31 in each landing leg control mechanism. At this time, the first actuator 1 in all landing leg control mechanisms is connected into a closed loop through the first liquid inlet pipe 29, the first liquid outlet pipe 30 and the active control oil path 31, and the second differential oil pump 24 is started to achieve the active differential control between the landing leg control mechanisms of the front group and the landing leg control mechanisms of the rear group. When a landing leg control mechanism in the front group and a landing leg control mechanism in the rear group are actively differentially controlled, each group of landing leg control mechanisms is provided with at least two landing leg control mechanisms, and the number of landing leg control mechanisms in the adjacent two groups is the same, and the landing leg control mechanisms in the adjacent two groups are one-to-one corresponding. The active control oil path 31 between the corresponding two landing leg control mechanisms is communicated by the second differential oil pump 24. When the corresponding two landing leg control mechanisms are connected into a closed loop through the first liquid inlet pipe 29, the first liquid outlet pipe 30 and the active control oil path 31 by the electromagnetic reversing valve 34 in the corresponding two landing leg control mechanisms respectively controlling the active control oil path 31 and the first liquid inlet pipe 29, the second differential oil pump 24 is started to achieve the active differential control between the front and rear landing leg control mechanisms.

[0053] As shown in Figures 3 to 21 When each group of landing leg control mechanisms is provided with two landing leg control mechanisms, the hydraulic control circuit of the embodiment further includes a first differential oil pump 25, and each group of landing leg control mechanisms corresponds to a first differential oil pump 25. The first differential oil pump 25 communicates the two active control oil paths 31 in the corresponding group, and when the two first actuators 1 in the group are connected into a closed loop through the first liquid inlet pipe 29, the first liquid outlet pipe 30 and the active control oil path 31 by the two electromagnetic reversing valves 34 in the group respectively controlling the corresponding active control oil path 31 and the first liquid inlet pipe 29, the first differential oil pump 25 is started to achieve the active differential control between the two landing leg units in the group.

[0054] Therefore, the landing leg unit of the embodiment matched with the hydraulic control circuit can realize various control modes of the landing gear, such as the active control of the landing leg unit, the passive differential control between the landing leg units, the active differential control between the front and rear landing leg units, and the active differential control between the two landing leg units in the group when the landing leg unit in each group is two. Such design enables the helicopter to change the structural posture of the landing leg unit according to the terrain conditions, and ensures that the helicopter can maintain the horizontal stability of the body when landing on the rugged or inclined ground.

[0055] Embodiment 1

[0056] Figure 9 A hydraulic control diagram is shown for a landing gear with a four-leg design and a single-degree-of-freedom structure for the landing leg unit, as shown in Figure 9 The hydraulic control circuit of the embodiment is provided with four hydraulic control units, and the landing leg unit is provided with four landing leg units. Each hydraulic control unit corresponds to one landing leg unit and forms a landing leg control mechanism with the landing leg unit. The four landing leg control mechanisms are divided into two groups and installed side by side from front to back on the bottom of the helicopter.

[0057] Each landing leg unit is provided with a first actuator 1, and each hydraulic control unit comprises a first inlet pipe 29, a first outlet pipe 30, an active control oil path 31, a passive control oil path 32, a first electro-hydraulic servo valve 33 and an electromagnetic switching valve 34 for switching the active control oil path 31 and the passive control oil path 32, one end of the first inlet pipe 29 is communicated with the rod cavity of the first actuator 1, and the other end is communicated with the P port of the electromagnetic switching valve 34, one end of the first outlet pipe 30 is communicated with the rodless cavity of the first actuator 1, and the other end is communicated with the first outlet pipe 30 in the remaining hydraulic control unit, in addition, the first outlet pipe 30 is also communicated with the oil tank 12 through the overflow valve 38 and the oil return valve 39, the oil return valve 39 is a two-position two-way electromagnetic valve, and the overflow valve 38 and the oil return valve 39 can make the excess hydraulic oil in the closed loop return to the oil tank 12. The first electro-hydraulic servo valve 33 is a three-position four-way electro-hydraulic valve, and the first electro-hydraulic servo valve 33 can control the switching of the oil path between the rodless cavity and the rod cavity of the first actuator 1 and the first inlet pipe 29 and the first outlet pipe 30, specifically, the first inlet pipe 29 is divided into two sections and provided with a first inlet pipe A and a first inlet pipe B, the first outlet pipe 30 is divided into two sections and provided with a first outlet pipe A and a first outlet pipe B, one end of the first inlet pipe A is communicated with the P port of the electromagnetic switching valve 34, and the other end is communicated with one inlet of the first electro-hydraulic servo valve 33, one end of the first inlet pipe B is communicated with the rod cavity of the first actuator 1, and the other end is communicated with one outlet of the first electro-hydraulic servo valve 33, one end of the first outlet pipe A is communicated with the other inlet of the first electro-hydraulic servo valve 33, and the other end is communicated with the remaining first outlet pipe 30, one end of the first outlet pipe B is communicated with the other outlet of the first electro-hydraulic servo valve 33, and the other end is communicated with the rodless cavity of the first actuator 1. When the first electro-hydraulic servo valve 33 is in the left position, the first inlet pipe A and the first inlet pipe B are communicated, and the first outlet pipe A and the first outlet pipe B are communicated, when the first electro-hydraulic servo valve 33 is in the right position, the first inlet pipe 29A and the first outlet pipe B are communicated, and the first inlet pipe B and the first outlet pipe A are communicated, so that the rodless cavity and the rod cavity of each first actuator 1 can be adjusted to be communicated, not simply the rodless cavity and the rodless cavity are communicated, and the rod cavity and the rod cavity are communicated, which can better realize the control of the hydraulic oil between each first actuator 1 and ensure the stability of the helicopter landing. One end of the passive control oil path 32 is communicated with the A port of the electromagnetic switching valve 34, so that the passive control oil path 32 can be communicated with the first inlet pipe 29, and the other end of the passive control oil path 32 is communicated with the passive control oil path 32 in the remaining hydraulic control unit; when the electromagnetic switching valve 34 controls the passive control oil path 32 to be communicated with the first inlet pipe 29, each first actuator 1 is connected into a closed loop through the first inlet pipe 29, the passive control oil path 32 and the first outlet pipe 30, so as to realize the passive differential control between each first actuator 1.

[0058] The active control mode of the landing leg unit is implemented as follows: Before the helicopter lands, the oil shut-off valve 16 and the oil return valve 39 are opened, and all solenoid directional valves 34 are switched to port A. At this point, the first actuator 1 is connected to the oil tank 12 via the first inlet pipe 29, the passive control oil circuit 32, the first branch oil circuit 14, and the main oil circuit 13. The one-way hydraulic pump 19 is activated, and hydraulic oil in the oil tank 12 is pumped into the first actuator 1. The extension or retraction of the piston rod of the first actuator 1 is controlled by the first electro-hydraulic servo valve 33. When the first electro-hydraulic servo valve 33 is in the left position, hydraulic oil is pumped into the rod chamber of the first actuator 1, causing the piston rod of the first actuator 1 to retract. When the first electro-hydraulic servo valve 33 is in the right position, hydraulic oil is pumped into the rodless chamber of the first actuator 1, causing the piston rod of the first actuator 1 to extend. This adjusts the extension length of each first actuator 1 to adapt to rough terrain. The oil flowing out of each first actuator 1 converges and flows back to the oil tank 12 through the return valve. Relief valve 38 ensures that the hydraulic oil pressure in the roll and lift circuits remains within the normal operating range. This control mode actively adjusts the posture of each leg based on the terrain, ensuring that the helicopter remains level during landing. Furthermore, the master control mode is used to control the leg retraction and initial leg height alignment before landing, facilitating switching to other control modes.

[0059] The implementation process of the passive differential control mode is as follows: Figure 12 The passive differential control mode of this embodiment is shown. Before the helicopter lands, the active control mode is used to control the piston rods of all first actuators 1 to the same length. At this time, all first actuators 1 are at the same height, and the oil closing valve 16 cuts off the oil supply between the oil tank 12 and the first actuators 1. Figure 12As shown, the oil return valve 39 is de-energized, the first electro-hydraulic servo valves 33 in the four landing leg control mechanisms are switched to the left position, and all solenoid reversing valves 34 are switched to port A. At this point, all first actuators 1 are connected via the passive control oil circuit 32, the first inlet pipe 29, and the first outlet pipe 30 to form a closed circuit. The total amount of hydraulic oil in this closed circuit remains unchanged, and the set pressure of the relief valve 38 is adjusted to a higher value to ensure normal function of the closed circuit control while preventing damage from excessive pressure. When the helicopter lands, the one-way hydraulic pump 19 is activated, pumping the hydraulic oil from the oil tank 12 into the four second actuators 5. The piston rod of the first actuator cylinder 1 in the landing leg unit that touches the ground first is stressed and moves toward the rodless cavity side, and the hydraulic oil in the rodless cavity of the first actuator cylinder 1 is pressed into the rodless cavity of the first actuator cylinder 1 in the remaining landing leg units that have not touched the ground through the first liquid outlet pipe 30. The piston rod of the first actuator cylinder 1 in the landing leg unit that has not touched the ground extends out and touches the ground under the pressure of the hydraulic oil. At the same time, the hydraulic oil in the rod cavity of the first actuator cylinder 1 in the landing leg unit that has not touched the ground is squeezed into the rod cavity of the first actuator cylinder 1 in the landing leg unit that has not touched the ground through the passive control oil circuit 32 and the first liquid inlet pipe 29 to ensure the circuit pressure balance. At this time, all the landing legs of the helicopter touch the ground, and at the same time, the movement of the second actuator cylinder 5 is coupled to prevent the foot end from slipping during the movement of the first actuator cylinder 1, thereby achieving a stable landing of the helicopter. As can be seen, this embodiment relies on the hydraulic oil within the entire closed circuit to achieve differential drive of the four first actuators 1. The driving force comes from the ground support force exerted on the first actuators 1 in one or more landing leg units that touch the ground first. Passive differential control between the first actuators 1 can enhance the helicopter's terrain adaptability. This control mode can also ensure that the helicopter can effectively maintain a level body in complex terrain or dynamically changing landing scenarios (such as the shaking of a ship's deck during a ship-borne helicopter landing), thereby improving the safety and stability of the helicopter landing.

[0060] like Figure 9 As shown, in this embodiment, the active control oil circuit 31 and the passive control oil circuit 32 are designed in parallel. One end of the active control oil circuit 31 is connected to port B of the electromagnetic reversing valve 34, allowing the active control oil circuit 31 to communicate with the first liquid inlet pipe 29. The hydraulic control circuit of this embodiment also includes a first differential oil pump 25. Two first differential oil pumps 25 are provided, one for each landing leg control mechanism. These first differential oil pumps 25 communicate with the two active control oil circuits 31 in that group. When the two electromagnetic reversing valves 34 in that group control the active control oil circuits 31 to communicate with the first liquid inlet pipe 29, the two first actuators 1 in that group are connected to form a closed circuit via the first liquid inlet pipe 29, the first liquid outlet pipe 30, and the active control oil circuit 31. The first differential oil pumps 25 are activated to achieve active differential control between the two landing leg units in that group.

[0061] The implementation process of the left and right leg active differential control is as follows: Figure 13 The active differential control mode of the left and right legs of the embodiment is shown, combined with Figure 13 Before the helicopter lands, control all the first actuators 1 to the same height via the active control mode, and close the oil valve 16 to cut off the oil supply relationship between the oil tank 12 and the first actuator 1. The oil return valve 39 is de-energized, each first electro-hydraulic servo valve 33 is switched to the left position, and all the electromagnetic reversing valves 34 are switched to the B interface. At this time, the two active control oil paths 31 in each group are connected via the first differential oil pump 25, and are connected with the first liquid inlet pipe 29 of the two first actuators 1, that is, the left and right first actuators 1 form a closed loop as a whole via the first liquid inlet pipe 29, the active control oil path 31 and the first liquid outlet pipe 30. The total amount of hydraulic oil in the closed loop remains unchanged, and the relief valve 38 is set to a higher pressure to ensure that the control closed loop functions normally while preventing excessive pressure from damaging the closed loop. When the helicopter lands, start the one-way hydraulic pump 19, and the hydraulic oil in the oil tank 12 is pumped into the second actuator 5. Start the two first differential oil pumps 25, and each first differential oil pump 25 pumps the hydraulic oil in the corresponding left (right) first actuator 1 into the right (left) first actuator 1 via the active control oil path 31 and the first liquid inlet pipe 29, while the hydraulic oil in the right (left) first actuator 1 is pressed into the left (right) first actuator 1 via the first liquid outlet pipe 30 to ensure that the loop pressure is balanced. At this time, all the landing legs of the helicopter are in contact with the ground. As can be seen, the embodiment is also an active control mode, but this control mode relies on the hydraulic oil in the entire closed loop and the first differential oil pump 25 to drive the piston rods of the left and right first actuators 1 to extend and retract, so as to realize the active differential control between the left and right first actuators 1. The active differential control between the first actuators 1 can increase the terrain adaptability of the helicopter. And this control mode can effectively maintain the level of the helicopter body in complex terrain or dynamic changing landing scenarios (such as the shaking of the ship deck when the ship-borne helicopter lands), thereby improving the safety and stability of the helicopter landing. In addition, compared with the active control mode using the hydraulic oil in the oil tank 12, this control mode can save driving power and reduce energy consumption. Before the helicopter lands, if the active control mode is directly used to control the first actuator 1 to act to adjust the attitude of the helicopter, a large power consumption is required, which will increase the weight of the helicopter. On the contrary, if the active control mode is only used to complete the simple action of retracting the first actuator 1, the required pressure is smaller.

[0062] As Figure 9As shown, the two adjacent groups of landing leg control mechanisms in the embodiment are provided with a first series oil path 26, a second differential oil pump 24 and two parallel oil paths 27, the two parallel oil paths 27 are provided in one-to-one correspondence with the two adjacent groups of landing leg control mechanisms, each parallel oil path 27 is provided in parallel with the first differential oil pump 25 in the corresponding group, and the two ends of each parallel oil path 27 are connected to the two active control oil paths 31 in the corresponding group; the first series oil path 26 is provided in one, the first series oil path 26 communicates the two parallel oil paths 27, and the second differential oil pump 24 is arranged in the first series oil path 26. When the electromagnetic reversing valve 34 controls the first actuator cylinder 1 to communicate with the active control oil path 31, at this time, all the first actuator cylinders 1 in the two adjacent groups are connected into a closed loop through the first liquid inlet pipe 29, the active control oil path 31, the parallel oil path 27, the first series oil path 26 and the first liquid outlet pipe 30, the second differential oil pump 24 is started to pump the hydraulic oil in all the first actuator cylinders 1 in one group to all the first actuator cylinders 1 in the other group, so as to realize the active differential control between the first actuator cylinders 1 in the two adjacent groups of landing leg control mechanisms.

[0063] The realization process of the active differential control of the two adjacent groups of landing leg control mechanisms is as follows: Figure 14 The active differential control mode of the two groups of legs in the embodiment is shown, before the helicopter lands, all the first actuator cylinders 1 are controlled to be the same height through the active control mode, and the oil supply relationship between the oil tank 12 and the first actuator cylinder 1 is cut off by the closed oil valve 16. Figure 14As shown, the oil return valve 39 is powered off, all the first electro-hydraulic servo valves 33 are switched to the left position, all the electromagnetic reversing valves 34 are switched to the B interface, and the active control oil way 31 is connected to the first liquid inlet pipe 29 connecting the two first actuating cylinders 1 at this time. When the helicopter lands, the one-way hydraulic pump 19 is started, and the hydraulic oil in the oil tank 12 is pumped into the second actuating cylinder 5. The second differential oil pump 24 is started, and the second differential oil pump 24 pumps the hydraulic oil in all the first actuating cylinders 1 in the front group (rear group) to all the first actuating cylinders 1 in the rear group (front group) through the first series oil way 26, the parallel oil way 27, the active control oil way 31 and the first liquid inlet pipe 29, while the hydraulic oil in all the first actuating cylinders 1 in the rear group (front group) is pressed into all the first actuating cylinders 1 in the front group (rear group) through the first liquid outlet pipe 30 to ensure the balance of the loop pressure, at this time all the landing legs of the helicopter touch the ground, realizing the stable landing of the helicopter. As can be seen, the embodiment is also in the active control mode, and the front and rear groups of first actuating cylinders 1 form a closed loop as a whole through the connection of the first series oil way 26, the parallel oil way 27, the active control oil way 31 and the first liquid inlet pipe 29, and the total amount of the hydraulic oil in the closed loop remains unchanged. The relief valve 38 is set to a higher pressure to ensure the normal control of the closed loop and prevent the closed loop from being damaged due to excessive pressure. The embodiment relies on the hydraulic oil in the entire closed loop and the second differential oil pump 24 to drive the piston rods of the front and rear groups of first actuating cylinders 1 to extend or retract, so as to realize the active differential control between the front and rear groups of first actuating cylinders 1. The active differential control between the front and rear groups of first actuating cylinders 1 can increase the terrain adaptability of the helicopter, ensure that the helicopter can effectively maintain the horizontal of the body in complex terrain or dynamic changing landing scene, and improve the safety and stability of the helicopter landing.

[0064] Embodiment 2:

[0065] Figure 10 The hydraulic control schematic diagram is shown, in which the landing gear adopts a four-leg design and the landing leg unit adopts a two-degree-of-freedom structure, as shown in Figure 10As shown, the difference between the present embodiment and embodiment 1 is that the landing leg unit of the present embodiment further comprises a second actuating cylinder 5, and each hydraulic control unit of the present embodiment further comprises a second liquid inlet pipe 35, a second liquid outlet pipe 36 and a second electro-hydraulic servo valve 37. One end of the second liquid inlet pipe 35 is communicated with the rod cavity of the second actuating cylinder 5, and the other end is communicated with the oil tank 12 via the main oil line 13 and the second branch oil line 15. The second liquid outlet pipe 36 is communicated with the rodless cavity of the second actuating cylinder 5 and the oil tank 12. The second electro-hydraulic servo valve 37 is a three-position four-way electro-hydraulic valve. The second electro-hydraulic servo valve 37 can switch the oil line between the rodless cavity and the rod cavity of the second actuating cylinder 5 and the second first liquid inlet pipe 29 and the second oil outlet pipe. The specific connection mode is the same as that of the first actuating cylinder 1, the first liquid inlet pipe 29, the first liquid outlet pipe 30 and the first electro-hydraulic servo valve 33. When the helicopter lands, the oil tank 12 is communicated with the second actuating cylinder 5 via the main oil line 13 and the second branch oil line 15, the one-way hydraulic pump 19 is opened, and the hydraulic oil in the oil tank 12 is pumped into the second actuating cylinder 5 to realize active control of the second actuating cylinder 5. The oil of each second actuating cylinder 5 flows back to the oil tank 12 after flowing out of the second electro-hydraulic servo valve 37. The extension and retraction of the piston rod of the second actuating cylinder 5 is controlled by the second electro-hydraulic servo valve 37. When the second electro-hydraulic servo valve 37 is in the left position, the hydraulic oil is pumped into the rod cavity of the second actuating cylinder 5, and the piston rod of the second actuating cylinder 5 is retracted. When the second electro-hydraulic servo valve 37 is in the right position, the hydraulic oil is pumped into the rodless cavity of the second actuating cylinder 5, and the piston rod of the second actuating cylinder 5 is extended, thereby adjusting the attitude of the landing leg. The movement of the landing leg coupled with the second actuating cylinder 5 can prevent the foot end from slipping during the movement of the landing leg, and realize stable landing of the helicopter. The first actuating cylinder 1 is the same as embodiment 1 regardless of whether it adopts active control mode, passive differential control mode or active differential control mode.

[0066] Embodiment 3:

[0067] Figure 15 The hydraulic control schematic diagram is shown in FIG. 4, which shows that the landing gear adopts six-leg design and the landing leg unit adopts single-degree-of-freedom structure. Figure 15 The difference between the present embodiment and embodiment 1 is that the present embodiment is provided with six landing leg units and six hydraulic control units. Each hydraulic control unit corresponds to a landing leg unit, and is arranged as a landing leg control mechanism with the landing leg unit. The six landing leg control mechanisms are divided into three groups and are installed side by side from front to back on the bottom of the helicopter. The rest of the design remains unchanged.

[0068] Embodiment 4:

[0069] Figure 16 The hydraulic control schematic diagram is shown in FIG. 5, which shows that the landing gear adopts six-leg design and the landing leg unit adopts two-degree-of-freedom structure. Figure 16As shown, the difference between the present embodiment and embodiment 2 is that the present embodiment is provided with six landing leg units and six hydraulic control units, each hydraulic control unit corresponds to one landing leg unit and is provided as a landing leg control mechanism with the landing leg unit, the six landing leg control mechanisms are divided into three groups and are installed side by side from front to back on the bottom of the helicopter. The rest of the design remains unchanged.

[0070] Embodiment 5:

[0071] Figure 22 Another hydraulic control schematic diagram is shown, in which the landing gear adopts a four-leg design and the landing leg unit adopts a single-degree-of-freedom structure. The difference between the present embodiment and embodiment 1 is that no differential oil pump is provided between the two landing leg control mechanisms in each group, and the design of the differential oil pump between the front and rear two groups of landing leg control mechanisms is different from that of embodiment 1. In order to clearly express the connection relationship, the two landing leg control mechanisms of each group of landing leg control mechanisms in the present embodiment are respectively referred to as left leg and right leg. As shown, Figure 22 As shown, the two adjacent groups of landing leg control mechanisms in the present embodiment are provided with a second series oil path 28 and a second differential oil pump 24, the second series oil path 28 is provided with two paths, one of which connects the active control oil path 31 of the left front leg with the active control oil path 31 of the rear right leg, and the second differential oil pump 24 is provided with two, one second differential oil pump 24 is arranged on each second series oil path 28. When the electromagnetic reversing valve 34 controls the first actuator cylinder 1 to communicate with the active control oil path 31, the first actuator cylinder 1 of the left front leg and the first actuator cylinder 1 of the right rear leg are connected into a closed loop via the first oil inlet pipe, the first oil outlet pipe, the active control oil path 31 and the second series oil path 28, the second differential oil pump 24 is started to pump the hydraulic oil in the first actuator cylinder 1 of the left front leg into the first actuator cylinder 1 of the right rear leg, so as to realize the active differential control between the left front leg and the right rear leg. The other second series oil path 28 connects the active control oil path 31 of the right front leg with the active control oil path 31 of the left rear leg, when the electromagnetic reversing valve 34 controls the first actuator cylinder 1 to communicate with the active control oil path 31, the first actuator cylinder 1 of the right front leg and the first actuator cylinder 1 of the left rear leg are connected into a closed loop via the first oil inlet pipe, the first oil outlet pipe, the active control oil path 31 and the second series oil path 28, the second differential oil pump 24 is started to pump the hydraulic oil in the first actuator cylinder 1 of the right front leg into the first actuator cylinder 1 of the left rear leg, so as to realize the active differential control between the right front leg and the left rear leg.

[0072] The realization process of the front and rear leg active differential control mode is as follows: before the helicopter lands, all the first actuating cylinders 1 are controlled to be the same height by the active control mode, and the oil supply relationship between the oil tank 12 and the first actuating cylinders 1 is cut off by the closed oil valve 16. The return valve 39 is de-energized, all the first electro-hydraulic servo valves 33 are switched to the left position, and all the electromagnetic reversing valves 34 are switched to the B interface. At this time, the first inlet pipe 29, the first outlet pipe 30, the active control oil way 31 and the second series oil way 28 are connected to the two first actuating cylinders 1 of the left front leg and the right rear leg. Two second differential oil pumps 24 are started, one of which pumps the hydraulic oil in the first actuating cylinder 1 in the left front leg into the first actuating cylinder 1 in the right rear leg through the second series oil way 28, the active control oil way 31 and the first inlet pipe 29, while the hydraulic oil in the first actuating cylinder 1 in the right rear leg is pressed into the first actuating cylinder 1 in the left front leg through the first outlet pipe 30, so as to ensure the balance of the loop pressure. The other second differential oil pump 24 pumps the hydraulic oil in the first actuating cylinder 1 in the right front leg into the first actuating cylinder 1 in the left rear leg through the second series oil way 28, the active control oil way 31 and the first inlet pipe 29, while the hydraulic oil in the first actuating cylinder 1 in the left rear leg is pressed into the first actuating cylinder 1 in the right front leg through the first outlet pipe 30, so as to ensure the balance of the loop pressure. At this time, all the landing legs of the helicopter are in contact with the ground, and the stable landing of the helicopter is realized.

[0073] The principles of the remaining active control modes and the passive differential control mode are the same as those of embodiment 1, which will not be described here.

[0074] Embodiment 6:

[0075] Figure 23Another hydraulic control schematic diagram is shown, in which the landing gear is designed with four legs and the landing leg unit is designed with two degrees of freedom. The difference between this embodiment and embodiment 5 is that the landing leg unit of this embodiment further comprises a second actuating cylinder 5, and each hydraulic control unit of this embodiment further comprises a second inlet pipe 35, a second outlet pipe 36 and a second electro-hydraulic servo valve 37. One end of the second inlet pipe 35 is connected to the rod cavity of the second actuating cylinder 5, and the other end is connected to the oil tank 12 via the main oil line 13 and the second branch oil line 15. The second outlet pipe 36 is connected to the rodless cavity of the second actuating cylinder 5 and the oil tank 12. The second electro-hydraulic servo valve 37 is a three-position four-way electro-hydraulic valve. The second electro-hydraulic servo valve 37 can switch the oil line between the rodless cavity and the rod cavity of the second actuating cylinder 5 and the second first inlet pipe 29 and the second outlet pipe. The specific connection mode is the same as that of the first actuating cylinder 1, the first inlet pipe 29, the first outlet pipe 30 and the first electro-hydraulic servo valve 33. When the helicopter lands, the oil tank 12 is connected to the second actuating cylinder 5 via the main oil line 13 and the second branch oil line 15, the one-way hydraulic pump 19 is opened, and the hydraulic oil in the oil tank 12 is pumped into the second actuating cylinder 5 to realize active control of the second actuating cylinder 5. The oil of each second actuating cylinder 5 flows back to the oil tank 12 after flowing out of the second electro-hydraulic servo valve 37. The extension or retraction of the piston rod of the second actuating cylinder 5 is controlled by the second electro-hydraulic servo valve 37. When the second electro-hydraulic servo valve 37 is in the left position, the hydraulic oil is pumped into the rod cavity of the second actuating cylinder 5, and the piston rod of the second actuating cylinder 5 is retracted. When the second electro-hydraulic servo valve 37 is in the right position, the hydraulic oil is pumped into the rodless cavity of the second actuating cylinder 5, and the piston rod of the second actuating cylinder 5 is extended, thereby adjusting the attitude of the landing leg. The movement of the landing leg coupled with the second actuating cylinder 5 can prevent the foot end from slipping during the movement of the landing leg, and realize stable landing of the helicopter. The first actuating cylinder 1 is the same as embodiment 5 whether it is in active control mode, passive differential control mode or active differential control mode.

[0076] Embodiment 7:

[0077] Figure 3 A hydraulic control schematic diagram is shown, in which the landing gear is designed with three legs and the landing leg unit is designed with a single degree of freedom structure, Figure 3As shown, since the landing leg control mechanism in this embodiment has only one leg in each group, different from embodiment 1, there is only one parallel oil line 27 between the front and rear groups of landing leg control mechanisms, which connects the two active control oil lines 31 in the double-leg mechanism group and is designed in parallel with the first differential oil pump 25, and the first series oil line 26 connects the parallel oil line 27 and the active control oil line 31 in the single-leg mechanism group, when the electromagnetic reversing valve 34 controls the first actuator cylinder 1 to communicate with the active control oil line 31, at this time, all the first actuator cylinders 1 in the adjacent front and rear groups are connected into a closed loop through the first liquid inlet pipe 29, the active control oil line 31, the parallel oil line 27, the first series oil line 26 and the first liquid outlet pipe 30, the second differential oil pump 24 is started to pump the hydraulic oil in all the first actuator cylinders 1 in the front (rear) group to all the first actuator cylinders 1 in the rear (front) group, to realize active differential control between the first actuator cylinders 1 in the adjacent two groups of landing leg control mechanisms.

[0078] The principles of the active control mode, passive differential control mode and active differential control mode of this embodiment are the same as those of embodiment 1.

[0079] Embodiment 8:

[0080] Figure 4 The hydraulic control schematic diagram of the landing gear with a three-leg design and the landing leg unit with a two-degree-of-freedom structure is shown in FIG. 8. Figure 4As shown, the difference between the embodiment and embodiment 7 is that the landing leg unit of the embodiment further comprises a second actuating cylinder 5, and each hydraulic control unit of the embodiment further comprises a second inlet pipe 35, a second outlet pipe 36 and a second electro-hydraulic servo valve 37. One end of the second inlet pipe 35 is communicated with the rod cavity of the second actuating cylinder 5, and the other end is communicated with the oil tank 12 via the main oil line 13 and the second branch oil line 15. The second outlet pipe 36 is communicated with the rodless cavity of the second actuating cylinder 5 and the oil tank 12. The second electro-hydraulic servo valve 37 is a three-position four-way electro-hydraulic valve. The second electro-hydraulic servo valve 37 can switch the oil line between the rodless cavity and the rod cavity of the second actuating cylinder 5 and the second first inlet pipe 29 and the second outlet pipe. The specific connection mode is the same as that of the first actuating cylinder 1, the first inlet pipe 29, the first outlet pipe 30 and the first electro-hydraulic servo valve 33. When the helicopter lands, the oil tank 12 is communicated with the second actuating cylinder 5 via the main oil line 13 and the second branch oil line 15, the one-way hydraulic pump 19 is opened, and the hydraulic oil in the oil tank 12 is pumped into the second actuating cylinder 5 to realize active control of the second actuating cylinder 5. The oil of each second actuating cylinder 5 flows back to the oil tank 12 after flowing out of the second electro-hydraulic servo valve 37. The extension and retraction of the piston rod of the second actuating cylinder 5 is controlled by the second electro-hydraulic servo valve 37. When the second electro-hydraulic servo valve 37 is in the left position, the hydraulic oil is pumped into the rod cavity of the second actuating cylinder 5, and the piston rod of the second actuating cylinder 5 is retracted. When the second electro-hydraulic servo valve 37 is in the right position, the hydraulic oil is pumped into the rodless cavity of the second actuating cylinder 5, and the piston rod of the second actuating cylinder 5 is extended, thereby adjusting the attitude of the landing leg. The movement of the landing leg coupled with the second actuating cylinder 5 can prevent the foot end from slipping during the movement of the landing leg, and realize stable landing of the helicopter. The first actuating cylinder 1 is the same as embodiment 7 in the active control mode, the passive differential control mode or the active differential control mode.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A hydraulic control circuit of a main and auxiliary differential control characterized by, The hydraulic control unit is provided with N (N≥3) hydraulic control units, each of which corresponds to one landing leg unit and is provided as a landing leg control mechanism with the landing leg unit, the N landing leg control mechanisms are divided into M groups and are arranged side by side, M≥2, and each landing leg unit is provided with a first actuator cylinder; Each hydraulic control unit comprises a first liquid inlet pipe, a first liquid outlet pipe, an active control oil way, a passive control oil way, a first electro-hydraulic servo valve and an electromagnetic reversing valve for switching the active control oil way and the passive control oil way, one end of the first liquid inlet pipe is communicated with the rod cavity of the first actuator cylinder, the other end is communicated with the electromagnetic reversing valve, one end of the first liquid outlet pipe is communicated with the rodless cavity of the first actuator cylinder, the other end is communicated with the first liquid outlet pipe in the remaining hydraulic control units, the first liquid inlet pipe and the first liquid outlet pipe are both communicated with the first electro-hydraulic servo valve, the first electro-hydraulic servo valve can switch the oil way between the rod cavity and the rodless cavity of the first actuator cylinder and the first liquid inlet pipe and the first liquid outlet pipe; one end of the passive control oil way is communicated with the electromagnetic reversing valve, the other end is communicated with the passive control oil way in the remaining hydraulic control units; when the electromagnetic reversing valve controls the passive control oil way to be communicated with the first liquid inlet pipe, each first actuator cylinder is connected into a closed loop through the first liquid inlet pipe, the passive control oil way and the first liquid outlet pipe, so as to realize passive differential control between each first actuator cylinder; the active control oil way is designed in parallel with the passive control oil way, and the active control oil way is communicated with the first liquid inlet pipe through the electromagnetic reversing valve; A second differential oil pump is arranged between the two adjacent groups of landing leg control mechanisms, the second differential oil pump is communicated with the active control oil ways in the two adjacent groups of landing leg control mechanisms, so that when the electromagnetic reversing valves in the two adjacent groups control the active control oil ways to be communicated with the first liquid inlet pipe, the first actuator cylinders in the two adjacent groups are connected into a closed loop through the first liquid inlet pipe, the first liquid outlet pipe and the active control oil way, and the second differential oil pump is started, so as to realize active differential control between the two adjacent groups of landing leg control mechanisms.

2. A hydraulic control circuit for active and passive differential control according to claim 1, characterized in that When each group of landing leg control mechanisms is provided with two landing leg control mechanisms, a first differential oil pump is arranged between the two first actuator cylinders in the group, the first differential oil pump is communicated with the two active control oil ways in the group, when the two electromagnetic reversing valves in the group control the active control oil ways to be communicated with the first liquid inlet pipe, the two first actuator cylinders in the group are connected into a closed loop through the first liquid inlet pipe, the first liquid outlet pipe and the active control oil way, and the first differential oil pump is started, so as to realize active differential control between the two landing leg units in the group.

3. The hydraulic control circuit of claim 1, wherein, When each group of landing leg control mechanisms is provided with at least two landing leg control mechanisms, and the number of landing leg control mechanisms in two adjacent groups is the same, the landing leg control mechanisms in the two adjacent groups correspond to each other, the active control oil paths between the corresponding two landing leg control mechanisms are communicated by a differential oil pump, and when the electromagnetic reversing valves in the corresponding two landing leg control mechanisms respectively control the active control oil paths and the first liquid inlet pipe to be communicated, the first actuators in the corresponding two landing leg control mechanisms are connected into a closed loop via the first liquid inlet pipe, the first liquid outlet pipe and the active control oil path, the differential oil pump is started, and active differential control between the front and rear landing leg control mechanisms is realized.

4. The master, slave differential control hydraulic control circuit according to claim 1, characterized by, The two adjacent groups of landing leg control mechanisms are provided with a series oil path, two parallel oil paths and a second differential oil pump, the two parallel oil paths correspond to the two adjacent groups of landing leg control mechanisms one by one, each parallel oil path is provided in parallel with the first differential oil pump in the corresponding group, and the two ends of each parallel oil path are connected to two active control oil paths in the corresponding group; the series oil path is provided with one, the series oil path communicates the two parallel oil paths, and the second differential oil pump is arranged in the series oil path; when the electromagnetic reversing valves control the first actuators and the active control oil paths to be communicated, all the first actuators in the two adjacent groups are connected into a closed loop via the first liquid inlet pipe, the active control oil path, the parallel oil path, the series oil path and the first liquid outlet pipe, the second differential oil pump is started, and the hydraulic oil in all the first actuators in one group is pumped into all the first actuators in the other group, so as to realize active differential control between the first actuators in the two adjacent groups of landing leg control mechanisms.

5. A hydraulically controlled circuit for active and passive differential control according to claim 1, 2, 3 or 4, characterized in that The hydraulic control circuit further comprises an oil tank, the oil tank communicates with the passive control oil paths in each hydraulic control unit, and when the electromagnetic reversing valves control the first actuators and the passive control oil paths to be communicated, the oil tank supplies oil to each first actuator to actively control the extension and retraction of the piston rod of each first actuator.

6. A master, slave differential control hydraulic control circuit according to claim 5, wherein, Each landing leg unit further comprises a second actuator, each hydraulic control unit further comprises a second liquid inlet pipe, a second liquid outlet pipe and a second electro-hydraulic servo valve, the second liquid inlet pipe communicates the rod cavity of the second actuator with the oil tank, the second liquid outlet pipe communicates the rodless cavity of the second actuator with the oil tank, and the second electro-hydraulic servo valve controls the switching of the second liquid inlet pipe and the second liquid outlet pipe with the rodless cavity and the rod cavity of the second actuator.

7. A main, passive differential controlled helicopter landing gear, characterised in that, The landing gear body, the landing leg unit and the active and passive differential control hydraulic control circuit according to claim 6 are comprised, and the landing leg unit is installed on the landing gear body.

8. A main, passive differential controlled helicopter landing gear according to claim 7, characterised in that, The cylinder body of the second actuator is connected to the landing gear body, and the end of the piston rod of the second actuator is connected to the cylinder body of the first actuator.

9. A main, passive differential controlled helicopter landing gear according to claim 7, characterised in that, The landing leg unit further comprises a second connecting rod, a third connecting rod and a second landing leg, one end of the second connecting rod is hingedly connected to the landing gear body, the other end is hingedly connected to the second landing leg at an intermediate position, the cylinder body of the first actuator is hingedly connected to the landing gear body via the third connecting rod, the end of the piston rod of the first actuator is hingedly connected to the second connecting rod at an intermediate position, the cylinder body of the second actuator is hingedly connected to the third connecting rod, and the end of the piston rod of the second actuator is hingedly connected to the top of the second landing leg.

10. A main, passive differential controlled helicopter landing gear according to claim 7, characterised in that, The landing leg unit further comprises a fourth connecting rod, a fifth connecting rod and a third landing leg, one end of the fourth connecting rod is hingedly connected to the landing gear body, the other end is hingedly connected to the top end of the third landing leg, the cylinder body of the first actuating cylinder is hingedly connected to the landing gear body, the end of the piston rod of the first actuating cylinder is hingedly connected to the fourth connecting rod, the cylinder body of the second actuating cylinder is hingedly connected to the fourth connecting rod, the end of the piston rod of the second actuating cylinder is hingedly connected to one end of the fifth connecting rod, and the other end of the fifth connecting rod is fixedly connected to the third landing leg.

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