An engine emergency stop mechanism

Abstract

The present invention provides an engine emergency stop mechanism, comprising: a constant pressure valve (2), a fuel flow metering device (3), a selector valve (4), an emergency stop solenoid valve (5) and a fuel cut-off valve (7); a constant pressure oil radial outlet (26) is provided on the constant pressure valve (2) so as to cut off the passage between the fuel inlet (25) and the constant pressure oil axial outlet (28) when the engine is not started; a first oil hole (43) is provided on the selector valve (4), and when the engine makes an emergency stop, the pressure in the piston chamber (48) is changed to make the metered fuel flow controlled by the fuel flow metering device (3) change to the minimum flow state, reducing the metered fuel supplied to the fuel cut-off valve (7). The present invention adds a constant pressure oil circuit pre-shielding device to avoid the problem of the constant pressure valve consuming the starting fuel flow; improves the selector valve structure, and adjusts the metered fuel flow to the minimum flow state during emergency stop to avoid hydraulic shock and ensure the reliable operation of the emergency stop mechanism.

Description

Technical Field

[0001] The present invention belongs to the field of aeroengine control, and particularly relates to an engine emergency shutdown mechanism. Background Art

[0002] The emergency shutdown mechanism plays an important role in the field of engine control. It uses a switch solenoid valve to guide the servo constant-pressure oil to a selector valve with a piston structure. When the piston of the selector valve moves from one side to the other side, the selector valve communicates the metered high-pressure fuel to the side with a larger end face area of the fuel cut-off valve, so that the fuel cut-off valve closes the fuel passage leading to the engine combustion chamber, realizing the engine shutdown function (for the structural schematic diagram, see Figure 1 ).

[0003] In the traditional emergency shutdown mechanism, the constant-pressure valve adopted is a conventional constant-pressure valve with an open constant-pressure oil circuit. When the engine is in the starting stage, since the rotational speed of the fuel supply plunger pump is relatively low, the fuel flow rate and pressure after the pump are relatively small. Since the constant-pressure oil circuit is open, the constant-pressure valve consumes the fuel flow rate after the pump since the engine starts, which easily causes insufficient starting flow rate of the engine and problems such as unsuccessful engine start.

[0004] In addition, when the traditional emergency shutdown mechanism executes the emergency shutdown function, it only cuts off the oil circuit of the metered fuel leading to the engine combustion chamber, but does not reduce the flow rate of the metered fuel. This will cause a large hydraulic shock on structures such as the fuel cut-off valve, and the working stability and reliability of the product are relatively poor. Summary of the Invention

[0005] The present invention provides an engine emergency shutdown mechanism, which solves the problems that the traditional emergency shutdown mechanism is prone to unsuccessful start and the fuel cut-off valve bears a large hydraulic shock during emergency shutdown.

[0006] The present invention provides an engine emergency shutdown mechanism, including: a constant-pressure valve 2, a fuel flow metering device 3, a selector valve 4, an emergency shutdown solenoid valve 5, and a fuel cut-off valve 7; wherein,

[0007] The constant-pressure valve 2 includes: a first housing 20, a first spring 21, a first valve core 22, a first valve sleeve 23, a fuel inlet 25, a constant-pressure oil radial outlet 26, and a constant-pressure oil axial outlet 28;

[0008] The first end of the first spring 21 is fixedly arranged at the first end inside the first housing 20. The second end of the first spring 21 is connected to the first end of the first valve core 22. The first valve core 22 is sleeved with a first valve sleeve 23, and the first valve sleeve 23 is fixedly arranged inside the first housing 20;

[0009] The second end of the first valve sleeve 23 is provided with a constant-pressure oil radial outlet 26, and the second end of the first housing 20 is provided with a constant-pressure oil axial outlet 28. The constant-pressure oil radial outlet 26 is communicated with the constant-pressure oil axial outlet 28;

[0010] A fuel inlet 25 is provided on the first housing 20. An axial cavity is provided at the center of the end face of the second end of the first valve core 22. The fuel inlet 25 passes through the first valve sleeve 23 and communicates with the cavity.

[0011] The second end of the first valve sleeve 23 is connected to the second end of the first housing 20, so that the cavity is not directly communicated with the constant-pressure oil axial outlet 28.

[0012] When the engine is not started, the second end of the first valve core 22 shields the constant-pressure oil radial outlet 26 under the pre-tightening force of the first spring 21, so that the cavity is not communicated with the pressure oil radial outlet 26, and the passage between the fuel inlet 25 and the constant-pressure oil axial outlet 28 is cut off.

[0013] The selection valve 4 includes: a second housing 40, a second valve core 41, a second valve sleeve 42, a first oil hole 43, a piston cavity 48, and a second spring 49.

[0014] The second valve sleeve 42 is in a cylindrical shape and is sleeved outside the second valve core 41. The second housing 40 is sleeved outside the second valve sleeve 42 and the second valve core 41.

[0015] A low-pressure cavity is formed between the first end of the second valve core 41 and the first end of the second housing 40, and the low-pressure cavity is communicated with the low-pressure oil return system of the engine emergency shutdown mechanism; a ring-shaped flange is provided at the second end of the second valve core 41, which is exposed outside the second valve sleeve 42 and contacts the inner wall of the second housing 40. A spring cavity is formed between the ring-shaped flange and the second end of the second housing 40, and the spring cavity is communicated with the low-pressure oil return system. A second spring 49 is provided in the spring cavity. A piston cavity 48 is formed between the ring-shaped flange, the second end of the second valve sleeve 42, and the inner wall of the second housing 40.

[0016] The piston cavity 48 passes through the second housing 40 and communicates with the outlet end of the emergency shutdown solenoid valve 5. The inlet end of the emergency shutdown solenoid valve 5 is communicated with the constant-pressure oil axial outlet 28. When the engine performs an emergency shutdown, the emergency shutdown solenoid valve 5 communicates the piston cavity 48 with the constant-pressure oil axial outlet 28.

[0017] The first end of the second valve sleeve 42 is provided with a first oil hole 43, and the first end of the second housing 40 is provided with a first oil passage. The first oil hole 43 is connected to the metering device control oil through the first oil passage.

[0018] When the engine performs an emergency shutdown, constant-pressure oil enters the piston cavity 48. The pressure of the constant-pressure oil is greater than the pre-tightening force of the second spring 49 and the fuel pressure in the spring cavity. The second valve core 41 compresses the second spring 49, and the first oil hole 43 is communicated with the low-pressure cavity, so that the metering device control oil is communicated with the low-pressure cavity, reducing the pressure of the metering device control oil, changing the metered fuel flow controlled by the fuel flow metering device 3 to the minimum flow state, and reducing the metered fuel supplied to the fuel cut-off valve 7.

[0019] Optionally, the constant pressure valve 2 further includes: a valve core plug 24;

[0020] A valve core plug 24 is provided between the second end of the first valve sleeve 23 and the second end of the first housing 20, and the valve core plug 24 is fixedly connected to the first housing 20.

[0021] Optionally, an annular stepped boss is provided inside the first housing 20, and the first end of the first valve sleeve 23 abuts against the annular stepped boss.

[0022] Optionally, the fuel flow metering device 3 is configured to receive the metering device control oil and control the metered fuel flow according to the pressure of the metering device control oil.

[0023] Optionally, the mechanism further includes: a bypass valve 6;

[0024] The selector valve 4 further includes: a second oil hole 44, a third oil hole 45, a fourth oil hole 46, a fifth oil hole 47;

[0025] The second valve core 41 is sequentially provided with a first annular groove, a second annular groove, and a third annular groove from the first end to the second end. The second annular groove communicates with the low-pressure chamber from the inside of the second valve core 41, and the third annular groove communicates with the spring chamber from the inside of the second valve core 41;

[0026] The second valve sleeve 42 is sequentially provided with a first oil hole 43, a second oil hole 44, a third oil hole 45, a fourth oil hole 46, a fifth oil hole 47 from the first end to the second end; the second housing 40 is sequentially provided with a first oil passage, a second oil passage, a third oil passage, a fourth oil passage, a fifth oil passage from the first end to the second end; the first oil hole 43, the second oil hole 44, the third oil hole 45, the fourth oil hole 46, the fifth oil hole 47 are respectively in one-to-one communication with the first oil passage, the second oil passage, the third oil passage, the fourth oil passage, the fifth oil passage;

[0027] The second oil passage is connected to the low-pressure oil return port of the bypass valve 6; the third oil passage is connected to the large chamber of the fuel cut-off valve 7; the fourth oil passage is connected to the metered fuel; the fifth oil passage is connected to the spring chamber of the bypass valve 6;

[0028] When the engine performs an emergency stop, the second oil hole 44 is disconnected from the second oil passage, disconnecting the passage between the low-pressure oil return port of the bypass valve 6 and the large chamber of the fuel cut-off valve 7; the fourth oil hole 46 communicates with the third oil hole 45 through the first annular groove, enabling the metered fuel to enter the large chamber of the fuel cut-off valve 7, driving the fuel cut-off valve of the fuel cut-off valve 7 to move, and cutting off the oil passage for the metered fuel to flow to the engine combustion chamber; the spring chamber of the bypass valve 6 and the low-pressure chamber of the selector valve 4 communicate through the second annular groove, reducing the pressure in the spring chamber of the bypass valve 6, causing the bypass valve to move, and flowing the metered fuel entering the bypass valve 6 into the low-pressure oil return system; the piston chamber 48 communicates with the third annular groove.

[0029] Optionally, when the engine cancels the emergency stop, the emergency stop solenoid valve 5 cuts off the piston chamber 48 from the constant pressure oil axial outlet 28;

[0030] The pressure in the piston chamber 48 drops to the fuel pressure in the spring chamber, and the second spring 49 resets the second spool 41. The first oil hole 43 is disconnected from the low-pressure chamber, restoring the metering device control oil pressure. The fuel flow metering device 3 controls the metered fuel supplied to the fuel cut-off valve 7 based on the restored metering device control oil pressure.

[0031] Optionally, a first central hole is provided at the center of the first end of the second spool 41, and a second central hole is provided at the center of the second end of the second spool 41;

[0032] The first central hole and the second central hole are not connected;

[0033] The second annular groove is connected to the low-pressure chamber through the first central hole, and the third annular groove is connected to the spring chamber through the second central hole.

[0034] Optionally, the selector valve 4 further includes: a throttle nozzle;

[0035] A throttle nozzle is provided on the end face of the second end of the second spool 41; the third annular groove is connected to the spring chamber through the throttle nozzle.

[0036] The present invention provides an engine emergency stop mechanism, which improves the structure of the constant pressure valve, adds a pre-shielding device for the constant pressure oil circuit, and avoids the problem of the constant pressure valve consuming the starting fuel flow; at the same time, it improves the structure of the selector valve, adjusts the metered fuel flow to the minimum flow state during emergency stop, avoids hydraulic shock, and ensures the reliable operation of the emergency stop mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a traditional emergency stop mechanism.

[0038] Figure 2 It is a schematic diagram of the improved emergency stop mechanism;

[0039] Figure 3 It is a schematic diagram of the constant pressure valve structure;

[0040] Figure 4 It is a schematic diagram of the selector valve structure;

[0041] Description of the reference numerals:

[0042] 1 - plunger pump; 2 - constant pressure valve; 3 - fuel flow metering device; 4 - selector valve; 5 - emergency stop solenoid valve; 6 - bypass valve; 7 - fuel cut-off valve;

[0043] 20 - First housing; 21 - First spring; 22 - First spool valve; 23 - First valve sleeve; 24 - Spool plug; 25 - Fuel inlet; 26 - Radial outlet for constant pressure oil; 27 - Oil return port; 28 - Axial outlet for constant pressure oil

[0044] 40 - Second housing; 41 - Second spool valve; 42 - Second valve sleeve; 43 - First oil hole; 44 - Second oil hole; 45 - Third oil hole; 46 - Fourth oil hole; 47 - Fifth oil hole; 48 - Piston chamber; 49 - Second spring Detailed implementation manners

[0045] The following specifically explains the engine emergency stop mechanism provided by the present invention in conjunction with the attached drawings. Figure 2 It is a structural schematic diagram of the engine emergency stop mechanism provided by the present invention. Figure 3 It is a structural schematic diagram of the constant pressure valve. Figure 4 It is a structural schematic diagram of the selector valve.

[0046] The present invention provides an engine emergency stop mechanism, including: a plunger pump 1, a constant pressure valve 2, a fuel flow metering device 3, a selector valve 4, an emergency stop solenoid valve 5, a bypass valve 6, and a fuel cut-off valve 7.

[0047] Among them, the plunger pump 1 is used to provide a fuel oil source for the engine control system.

[0048] The constant pressure valve 2 adjusts the fuel after the plunger pump into control oil with a constant pressure.

[0049] The fuel flow metering device 3 measures the fuel after the plunger pump according to the pressure and flow rate of the control oil of the metering device, and outputs the metered fuel to the subsequent system.

[0050] The selector valve 4 communicates or cuts off the oil path between the metered fuel and the large chamber on the left side of the fuel cut-off valve 7 according to the control requirements, communicates or cuts off the oil path between the low-pressure oil return port of the bypass valve 6 and the large chamber on the left side of the fuel cut-off valve 7, and communicates or cuts off the oil path between the control oil of the metering device and the low-pressure oil return system.

[0051] The emergency stop solenoid valve 5 is used to communicate or cut off the oil path between the constant pressure oil and the piston chamber of the selector valve 4, control the movement of the spool valve of the selector valve 4, and perform the emergency stop operation.

[0052] The bypass valve 6 is used to communicate or cut off the oil path between the metered fuel and the low-pressure oil return system.

[0053] The fuel cut-off valve 7 is used to communicate or cut off the oil path of the metered fuel leading to the engine combustion chamber.

[0054] The constant pressure valve 2 includes: a housing 20, a first spring 21, a first spool valve 22, a first valve sleeve 23, a spool plug 24, a fuel inlet 25, a radial outlet 26 for constant pressure oil, an oil return port 27, and a radial outlet 28 for constant pressure oil.

[0055] Among them, Figure 3 As shown, the left side of the first valve core 22 and the housing 20 envelop a spring cavity, in which a first spring 21 is installed. The first spring 21 is connected to the left side of the first valve core 22. The periphery of the first valve core 22 is a first valve sleeve 23, which is fixed in the housing 20. The right side of the first valve sleeve 23 presses the valve core plug 24 onto the housing 20.

[0056] When the engine is stopped and not started, the first spring 21 pushes the first valve core 22 to the right stop position, and the constant pressure oil radial outlet 26 is blocked by the first valve core 22, and no constant pressure oil is output.

[0057] When the engine starts to start, the speed of the plunger pump 1 gradually increases, the fuel flow and pressure after the plunger pump 1 gradually increase, the oil pressure at the fuel inlet 25 of the constant pressure valve 2 gradually increases, and the first valve core 22 gradually moves to the left under the action of the fuel pressure and compresses the first spring 21. The fuel on the side of the first valve core 22 close to the first spring 21 is discharged in appropriate amounts through the return oil port 27, and the shielding amount of the first valve core 22 on the constant pressure oil radial outlet 26 gradually decreases. However, before the constant pressure oil radial outlet 26 is opened, there is no constant pressure oil output, and the constant pressure valve 2 does not consume the fuel flow after the plunger pump 1, ensuring that the engine starts reliably. When the engine speed rises to a certain speed and the fuel flow after the plunger pump 1 is sufficient, the first valve core 22 moves to the open position, the constant pressure oil radial outlet 26 opens, the constant pressure oil pressure begins to build up and maintains a constant pressure, and the product control system works normally.

[0058] The selection valve 4 includes: a housing 40 , a second valve core 41 , a second valve sleeve 42 , a first oil hole 43 , a second oil hole 44 , a third oil hole 45 , a fourth oil hole 46 , a fifth oil hole 47 , a piston chamber 48 , and a second spring 49 .

[0059] The second valve core 41 is provided with a first annular groove, a second annular groove, and a third annular groove in sequence from the first end to the second end.

[0060] The second valve sleeve 42 is provided with a first oil hole 43, a second oil hole 44, a third oil hole 45, a fourth oil hole 46, and a fifth oil hole 47 in sequence from the first end to the second end; the second housing 40 is provided with a first oil circuit, a second oil circuit, a third oil circuit, a fourth oil circuit, and a fifth oil circuit in sequence from the first end to the second end; the first oil hole 43, the second oil hole 44, the third oil hole 45, the fourth oil hole 46, and the fifth oil hole 47 are connected to the first oil circuit, the second oil circuit, the third oil circuit, the fourth oil circuit, and the fifth oil circuit respectively.

[0061] Among them, Figure 4As shown, on the left side of the second spool 41, an envelope is formed with the housing 40 to form the low-pressure chamber of the selector valve 4. The low-pressure chamber is connected to the low-pressure oil return system. The periphery of the second spool 41 is the second valve sleeve 42, and the second valve sleeve 42 is fixed in the housing 40. On the right side of the second spool 41, an envelope is formed with the housing 40 to form a spring chamber. Inside the spring chamber, a second spring 49 is assembled. The spring chamber communicates with the low-pressure oil return system. The second spring 49 is connected to the right side of the second spool 41. The raised flange on the right side of the second spool 41 forms an envelope with the housing 40 and the second valve sleeve 42 to form a piston chamber. A central hole is opened on the right side of the second spool 41, and a throttle nozzle is arranged in the central hole. The annular groove on the rightmost side of the second spool 41 communicates with the throttle nozzle through the radial hole of the second spool 41 and communicates with the spring chamber through the throttle nozzle.

[0062] The second annular groove communicates with the low-pressure chamber from the inside of the second spool 41, and the third annular groove communicates with the spring chamber from the inside of the second spool 41.

[0063] The first oil passage is connected to the control oil of the metering device, the second oil passage is connected to the low-pressure oil return port of the bypass valve 6; the third oil passage is connected to the large chamber of the fuel cut-off valve 7; the fourth oil passage is connected to the metered fuel; the fifth oil passage is connected to the spring chamber of the bypass valve 6.

[0064] When the engine performs an emergency stop, the second oil hole 44 is disconnected from the second oil passage, disconnecting the passage between the low-pressure oil return port of the bypass valve 6 and the large chamber of the fuel cut-off valve 7; the fourth oil hole 46 communicates with the third oil hole 45 through the first annular groove, allowing the metered fuel to enter the large chamber of the fuel cut-off valve 7, driving the fuel cut-off valve of the fuel cut-off valve 7 to move, and cutting off the oil passage for the metered fuel to flow to the engine combustion chamber; the spring chamber of the bypass valve 6 and the low-pressure chamber of the selector valve 4 are connected through the second annular groove, reducing the pressure in the spring chamber of the bypass valve 6, causing the bypass valve to move, and flowing the metered fuel entering the bypass valve 6 into the low-pressure oil return system; the piston chamber 48 communicates with the third annular groove.

[0065] When the emergency stop operation is not performed, the piston chamber 48 is low-pressure oil. The second spool 41 is in the left stop position under the action of the second spring 49. The first oil passage connecting the oil return system is disconnected. The second oil passage and the third oil passage communicate. The fourth oil passage connecting the metered fuel is disconnected, and the fifth oil passage connecting the oil return system is disconnected.

[0066] When performing an emergency stop operation, the piston chamber 48 is filled with constant-pressure oil. Under the action of the constant-pressure oil pressure, the second spool valve 41 moves to the right against the action of the second spring 49. The piston chamber 48 communicates with the annular groove on the rightmost side of the second spool valve 41. The constant-pressure oil communicates with the throttle nozzle through the radial hole of the second spool valve 41. At this time, a metering oil pressure is formed in the piston chamber 48. Under the action of the metering oil pressure, the second spool valve 41 overcomes the combined action of the spring force on the right side of the second spool valve 41 and the low-pressure fuel pressure, continues to move to the right, and finally reaches the right stop position; the first oil circuit connects the control oil of the metering device and the low-pressure return oil system, adjusting the metered fuel flow to the minimum flow state; the second oil circuit connecting the bypass valve 6 is disconnected; the third oil circuit connecting the fuel cut-off valve 7 and the fourth oil circuit connecting the metered fuel communicate, allowing the metered fuel to enter the large cavity on the left side of the fuel cut-off valve 7. Although the pressures on both sides of the fuel cut-off valve are the metered fuel pressure, since the left end face area of the fuel cut-off valve is larger than the right end face area, the left acting force is greater than the right acting force. Therefore, the fuel cut-off valve moves to the right, finally cutting off the oil circuit for the metered fuel to flow to the engine combustion chamber; the fifth oil circuit communicates the oil circuit on the right side of the bypass valve 6 with the low-pressure return oil system. The bypass valve 6 moves to the right under the metered fuel pressure, allowing the metered fuel to flow into the low-pressure return oil system through the bypass valve 6.

[0067] When the emergency stop signal is eliminated, the emergency stop solenoid valve 5 cuts off the oil circuit between the piston chamber 48 and the axial outlet 28 of the constant-pressure oil; the pressure in the piston chamber 48 drops to the same pressure as the fuel pressure in the spring chamber. The second spring 49 causes the second spool valve 41 to return to its original position. The first oil hole 43 is disconnected from the low-pressure chamber, restoring the control oil pressure of the metering device. The fuel flow metering device 3 controls the metered fuel supplied to the fuel cut-off valve 7 according to the restored control oil pressure of the metering device; the second oil circuit and the third oil circuit communicate, allowing communication between the low-pressure return oil port of the bypass valve 6 and the large cavity of the fuel cut-off valve 7, resetting the fuel cut-off valve 7 and communicating the oil circuit for the metered fuel to flow to the engine combustion chamber; the fourth oil hole 46 is disconnected from the third oil hole 45, cutting off the oil circuit for the metered fuel to enter the large cavity of the fuel cut-off valve 7; driving the fuel cut-off valve of the fuel cut-off valve 7 to move, cutting off the oil circuit for the metered fuel to flow to the engine combustion chamber; the passage between the fifth oil hole 47 and the central hole on the left side of the second spool valve 41 is cut off, and the return oil of the spring chamber of the bypass valve 6 is cut off. The spring chamber forms a sealed chamber, and the pressure in the spring chamber rapidly rises to the metered fuel pressure. At this time, the fuel pressures at both ends of the bypass valve 6 are the same. The bypass valve 6 moves to the left to the stop position under the action of the right-side spring preload force, cutting off the passage between the metered fuel and the low-pressure return oil system.

[0068] The technical solution of the present invention provides an improved engine emergency stop mechanism. For the principle, refer to Figure 2This emergency stop mechanism improves the structure of the constant pressure valve 2. The length of the constant pressure valve core and the bushing is increased on the outlet side of the constant pressure oil circuit. Radial oil holes are opened on the bushing, and a valve core plug is added to the end face of the valve core, so that the constant pressure oil circuit changes from discharging oil through the axial central hole to discharging oil radially. The timing of establishing the constant pressure oil pressure is adjusted by reasonably setting the pre-shielding amount between the constant pressure valve core and the bushing;

[0069] During the engine starting stage, the constant pressure oil circuit is disconnected, and the constant pressure valve does not consume the engine starting fuel flow. When the engine speed rises to a certain speed and the fuel flow after the pump is sufficient, the constant pressure valve core moves to the open position, and the constant pressure oil pressure begins to be established, and the product control system works normally.

[0070] At the same time, this emergency stop mechanism improves the structure of the selector valve. An oil drain hole is added at one end of the selector valve, and the oil drain hole is connected to the metering device control oil circuit. When the selector valve moves, the metering device control oil circuit is connected to the oil return system through the oil drain hole, and the metering device is adjusted to the minimum fuel control position, so that the metered fuel flow is adjusted to the minimum flow state, avoiding hydraulic shock, and enabling the fuel cut-off valve to more stably and reliably cut off the fuel leading to the combustion chamber, realizing emergency stop.

Claims

1. An engine emergency stop mechanism, characterized in that, Comprising: A constant pressure valve (2), a fuel flow metering device (3), a selector valve (4), an emergency stop solenoid valve (5) and a fuel cut-off valve (7); wherein, The constant pressure valve (2) comprises: a first housing (20), a first spring (21), a first valve core (22), a first valve sleeve (23), a fuel inlet (25), a constant pressure oil radial outlet (26), a constant pressure oil axial outlet (28); The first end of the first spring (21) is fixedly arranged at the first end within the first housing (20), the second end of the first spring (21) is connected to the first end of the first valve core (22), the first valve core (22) is externally sleeved with the first valve sleeve (23), and the first valve sleeve (23) is fixedly arranged within the first housing (20); The second end of the first valve sleeve (23) is provided with the constant pressure oil radial outlet (26), the second end of the first housing (20) is provided with the constant pressure oil axial outlet (28), and the constant pressure oil radial outlet (26) is communicated with the constant pressure oil axial outlet (28); The first housing (20) is provided with the fuel inlet (25), the center of the end face of the second end of the first valve core (22) is provided with an axial concave cavity, and the fuel inlet (25) passes through the first valve sleeve (23) and is communicated with the concave cavity; The second end of the first valve sleeve (23) is connected to the second end of the first housing (20), so that the concave cavity is not directly communicated with the constant pressure oil axial outlet (28); When the engine is not started, the second end of the first valve core (22) shields the constant pressure oil radial outlet (26) under the action of the pre-tightening force of the first spring (21), so that the concave cavity is not communicated with the pressure oil radial outlet (26), and the passage between the fuel inlet (25) and the constant pressure oil axial outlet (28) is cut off; The selector valve (4) comprises: a second housing (40), a second valve core (41), a second valve sleeve (42), a first oil hole (43), a piston cavity (48), a second spring (49); The second valve sleeve (42) is in a cylindrical shape and is sleeved outside the second valve core (41), and the second housing (40) is sleeved outside the second valve sleeve (42) and the second valve core (41); A low-pressure cavity is formed between the first end of the second valve core (41) and the first end of the second housing (40), and the low-pressure cavity is communicated with the low-pressure oil return system of the engine emergency stop mechanism; a ring-shaped flange is arranged at the second end of the second valve core (41), which is exposed outside the second valve sleeve (42) and contacts the inner wall of the second housing (40), a spring cavity is formed between the ring-shaped flange and the second end of the second housing (40), the spring cavity is communicated with the low-pressure oil return system, the second spring (49) is arranged in the spring cavity, and a piston cavity (48) is formed between the ring-shaped flange, the second end of the second valve sleeve (42) and the inner wall of the second housing (40); The piston cavity (48) passes through the second housing (40) and is communicated with the outlet end of the emergency stop solenoid valve (5), the inlet end of the emergency stop solenoid valve (5) is communicated with the constant pressure oil axial outlet (28), and when the engine performs an emergency stop, the emergency stop solenoid valve (5) communicates the piston cavity (48) with the constant pressure oil axial outlet (28); A first oil hole (43) is provided at the first end of the second valve sleeve (42), a first oil passage is provided at the first end of the second housing (40), and the first oil hole (43) is connected to a metering device to control oil through the first oil passage; When the engine is emergency stopped, the constant pressure oil enters the piston chamber (48), the pressure of the constant pressure oil is greater than the preload force of the second spring (49) and the fuel pressure in the spring chamber, the second valve core (41) compresses the second spring (49), the first oil hole (43) is connected with the low pressure chamber, so that the metering device control oil is connected with the low pressure chamber, the metering device control oil pressure is reduced, and the metered fuel flow controlled by the fuel flow metering device (3) changes to a minimum flow state, thereby reducing the metered fuel provided to the oil cut-off valve (7).

2. The mechanism according to claim 1, wherein The constant pressure valve (2) further comprises: a valve core plug (24); A valve core plug (24) is provided between the second end of the first valve sleeve (23) and the second end of the first housing (20), and the valve core plug (24) is fixedly connected to the first housing (20).

3. The mechanism according to claim 1, characterized in that, An annular step boss is arranged in the first housing (20), and the first end of the first valve sleeve (23) abuts against the annular step boss.

4. The mechanism according to claim 1, characterized in that, The fuel flow metering device (3) is used to receive the metering device control oil and control the metered fuel flow according to the pressure of the metering device control oil.

5. The mechanism according to claim 1, characterized in that, The mechanism further comprises: a bypass valve (6); The selection valve (4) further comprises: a second oil hole (44), a third oil hole (45), a fourth oil hole (46), and a fifth oil hole (47); The second valve core (41) is provided with a first annular groove, a second annular groove, and a third annular groove in sequence from the first end to the second end, the second annular groove is communicated with the low-pressure chamber from the inside of the second valve core (41), and the third annular groove is communicated with the spring chamber from the inside of the second valve core (41); The second valve sleeve (42) is provided with a first oil hole (43), a second oil hole (44), a third oil hole (45), a fourth oil hole (46), and a fifth oil hole (47) in sequence from the first end to the second end; the second housing (40) is provided with a first oil passage, a second oil passage, a third oil passage, a fourth oil passage, and a fifth oil passage in sequence from the first end to the second end; the first oil hole (43), the second oil hole (44), the third oil hole (45), the fourth oil hole (46), and the fifth oil hole (47) are connected to the first oil passage, the second oil passage, the third oil passage, the fourth oil passage, and the fifth oil passage, respectively; The second oil circuit is connected to the low-pressure oil return port of the bypass valve (6); the third oil circuit is connected to the large chamber of the oil cut-off valve (7); the fourth oil circuit is connected to the metered fuel; and the fifth oil circuit is connected to the spring chamber of the bypass valve (6); When the engine makes an emergency stop, the second oil hole (44) is disconnected from the second oil circuit, and the passage between the low-pressure oil return port of the bypass valve (6) and the large chamber of the fuel cut-off valve (7) is disconnected; the fourth oil hole (46) communicates with the third oil hole (45) through the first annular groove, so that the metered fuel enters the large chamber of the fuel cut-off valve (7), driving the fuel cut-off valve of the fuel cut-off valve (7) to move, and cutting off the oil circuit of the metered fuel flowing to the engine combustion chamber; the spring chamber of the bypass valve (6) and the low-pressure chamber of the selector valve (4) are connected through the second annular groove, reducing the pressure in the spring chamber of the bypass valve (6), causing the bypass valve to move, and flowing the metered fuel entering the bypass valve (6) into the low-pressure oil return system; the piston chamber (48) is connected to the third annular groove.

6. The mechanism according to claim 5, characterized in that, When the engine cancels the emergency stop, the emergency stop solenoid valve (5) cuts off the piston chamber (48) and the constant-pressure oil axial outlet (28); The pressure in the piston chamber (48) is reduced to the fuel pressure in the spring chamber, and the second spring (49) resets the second valve core (41), disconnecting the first oil hole (43) from the low-pressure chamber, restoring the control oil pressure of the metering device, and the fuel flow metering device (3) controls the metered fuel supplied to the fuel cut-off valve (7) according to the restored control oil pressure of the metering device.

7. The mechanism according to claim 5, characterized in that A first central hole is provided at the center of the first end of the second valve core (41), and a second central hole is provided at the center of the second end of the second valve core (41); The first central hole and the second central hole are not connected; The second annular groove communicates with the low-pressure chamber through the first central hole, and the third annular groove communicates with the spring chamber through the second central hole.

8. The mechanism according to claim 5, wherein The selector valve (4) further includes: a throttle nozzle; A throttle nozzle is provided on the end face of the second end of the second valve core (41); the third annular groove communicates with the spring chamber through the throttle nozzle.

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