Automatic unloading protection circuit for emergency braking of locomotive

Abstract

The utility model relates to the technical field of control of internal combustion locomotives, in particular to an automatic unloading protection circuit for emergency braking of a locomotive. Through the protection circuit, when a locomotive runs normally, a traction generator excitation contactor is electrified, an exciter excitation contactor on a generator excitation branch is electrified, a generator rotor is driven to generate electricity, a diesel engine rotating speed adjusting branch runs normally, and the running speed of the locomotive is controlled; when the locomotive is braked emergently, the sanding pressure relay is closed, the coil of the intermediate relay is electrified, the first normally open contact of the intermediate relay is closed, the normally closed contact of the intermediate relay is opened, the coil of the unloading relay is electrified, the normally closed contact of the unloading relay is opened, the excitation branch of the generator is disconnected, and the excitation contactor of the exciter loses power and stops working. The generator rotor loses excitation power and stops generating power; and meanwhile, an intermediate relay normally-closed contact on the diesel engine rotating speed adjusting branch is disconnected, so that the diesel engine rotating speed adjusting branch is disconnected, the input end of the locomotive microcomputer loses the adjusting signal, and the diesel engine is automatically decelerated.

Description

Technical Field

[0001] The present application relates to the field of control technology for diesel locomotives, and in particular to an automatic unloading protection circuit for emergency braking of a locomotive. Background Art

[0002] During the operation of a diesel locomotive, if an emergency situation occurs, such as someone encroaching on the line, shunting speed exceeding the limit, etc., emergency braking is required to stop the locomotive. At this time, the driver should immediately move the self-valve handle to the emergency brake position and must not move the self-valve handle again before stopping. Then move the locomotive main handle to 0 position, complete the locomotive braking, and stop traction. However, such operation has a lag, that is, traction and braking are carried out at the same time, which greatly prolongs the braking distance and increases the possibility of accidents. Utility Model Content

[0003] The utility model aims to solve the problem that the locomotive will not automatically unload during emergency braking, which increases the risk factor, and thus provides a protection circuit that can automatically unload during emergency braking of the locomotive.

[0004] The utility model solves the above problems by adopting the following technical solutions:

[0005] A locomotive emergency brake automatic unloading protection circuit includes a locomotive excitation control circuit and an unloading control circuit. The locomotive excitation control circuit includes a traction branch, a generator excitation branch, and a diesel engine speed adjustment branch.

[0006] The traction branch includes a traction generator excitation contactor. The normally open contact of the traction generator excitation contactor is connected to the generator excitation branch. The generator excitation branch is connected to the exciter excitation contactor. The normally open contact of the traction generator excitation contactor is connected to the input terminal of the locomotive microcomputer, and the exciter excitation contactor is connected to the output terminal of the locomotive microcomputer. When the traction branch is turned on, the normally open contact of the traction generator excitation contactor closes, the exciter excitation contactor is energized, and the generator rotor is driven to generate electricity. The diesel engine speed adjustment branch is connected to the input terminal of the locomotive microcomputer.

[0007] The unloading control circuit includes a sand-spreading pressure relay, an intermediate relay, and an unloading relay. The sand-spreading pressure relay is connected to the coil and the first normally open contact of the intermediate relay, and the coil of the intermediate relay and the first normally open contact of the intermediate relay are connected to both ends of the coil of the unloading relay; the normally closed contact of the intermediate relay is connected to the diesel engine speed control branch, and the normally closed contact of the unloading relay is connected to the generator excitation branch;

[0008] When the locomotive is in emergency braking, the sand-spreading pressure relay is closed by air pressure, and the coil of the intermediate relay is energized, so that the first normally open contact of the intermediate relay is closed and the normally closed contact is disconnected, the diesel engine speed adjustment branch is disconnected, the unloading relay coil is energized, the normally closed contact of the unloading relay is disconnected, and the generator excitation branch is disconnected.

[0009] Compared with the prior art, the present invention adopting the above technical solution has the following beneficial effects:

[0010] By means of the protection circuit of the present invention, when the locomotive is running normally, the traction generator excitation contactor is energized, so that the normally open contact of the traction generator excitation contactor connected to the generator excitation branch is closed, the input end of the locomotive microcomputer receives the signal and supplies power to the exciter excitation contactor, the exciter excitation contactor is energized, driving the generator rotor to generate electricity, the train runs normally, the diesel engine speed adjustment branch operates normally, and the locomotive running speed is controlled; when the locomotive is emergency braked, the sand spreading pressure relay is closed by the air pressure of the sand spreading pipe, the coil of the intermediate relay is energized, so that the first normally open contact of the intermediate relay is closed and the normally closed contact is disconnected, the coil of the unloading relay is energized, the normally closed contact of the unloading relay is disconnected, the generator excitation branch is disconnected, the exciter excitation contactor loses power and stops working, the generator rotor loses excitation power and stops generating electricity; at the same time, the normally closed contact of the intermediate relay on the diesel engine speed adjustment branch is disconnected, causing the diesel engine speed adjustment branch to be disconnected, the input end of the locomotive microcomputer loses the adjustment signal, and the diesel engine automatically slows down.

[0011] As a preferred embodiment, a further technical solution of the present invention is:

[0012] The traction branch also includes a machine-controlled switch and a first dynamic connection point. One end of the machine-controlled switch is connected to the positive pole of the power supply via the master switch, and the other end of the machine-controlled switch is connected to the first dynamic connection point. The first dynamic connection point is connected to the traction generator excitation contactor. When the locomotive main handle is in position 1, lowered, held, or raised, the first dynamic connection point closes, and the traction branch is connected. The first dynamic connection point ensures that the traction branch is connected only when the locomotive main handle is in position 1, lowered, held, or raised, and the first dynamic connection point is connected, thus facilitating the traction branch and preparing for the traction generator excitation branch.

[0013] The first dynamic connection point is also connected to the second normally open contact of the intermediate relay, which is connected between the coil of the intermediate relay and the first normally open contact of the intermediate relay. When the coil of the intermediate relay is energized, the first and second normally open contacts of the intermediate relay close, and the first dynamic connection point supplies power to the coil of the intermediate relay through the second normally open contact of the intermediate relay. When the sand-spreading pressure relay is energized, the coil of the intermediate relay is energized and connected, causing the second normally open contact of the intermediate relay to close. The first dynamic connection point continuously supplies power to the coil of the intermediate relay through the second normally open contact of the intermediate relay, causing the intermediate relay to self-lock.

[0014] The generator excitation branch includes a second dynamic connection point and a wind pressure protection relay. One end of the second dynamic connection point is connected to the master switch, and the other end is connected to the wind pressure protection relay. The wind pressure protection relay is connected to the normally closed contact of the unloading relay. When the locomotive main handle is in the lowering, holding, or raising position, the second dynamic connection point closes, and the wind pressure in the ventilation system drives the wind pressure protection relay to open and close. The wind pressure protection relay detects the wind pressure in the ventilation system and controls the generator excitation branch to open or close according to the wind pressure.

[0015] The diesel engine speed adjustment branch includes a third dynamic connection point and a fourth dynamic connection point. The third dynamic connection point is used to close when the locomotive main handle is in the raised position, and the fourth dynamic connection point is used to close when the locomotive main handle is in the held position or raised position. The third dynamic connection point and the fourth dynamic connection point are connected in parallel, and one end is connected to the normally closed contact of the intermediate relay. The other ends of the third dynamic connection point and the fourth dynamic connection point are respectively connected to the input end of the locomotive microcomputer. When the normally closed contact of the intermediate relay is disconnected, the branch of the third dynamic connection point and the branch of the fourth dynamic connection point are disconnected. Through the third dynamic connection point and the fourth dynamic connection point, the input end of the locomotive microcomputer receives different diesel engine speed control signals, thereby controlling the speed of the diesel engine. When the locomotive brakes suddenly, the normally closed contact of the intermediate relay is disconnected, the branch of the third dynamic connection point and the fourth dynamic connection point are disconnected, and the locomotive microcomputer has no diesel engine speed control signal input, so the locomotive microcomputer automatically controls the diesel engine to slow down.

[0016] The unloading control circuit also includes a sand spreading control branch, which includes a forward sand spreading control valve and a rearward sand spreading control valve. The forward sand spreading control valve is connected to the forward switch, and the rearward sand spreading control valve is connected to the rearward switch. The forward sand spreading control valve, the forward switch, the rearward sand spreading control valve, and the rearward switch are connected in parallel and in series with a third normally open contact of an intermediate relay. When the coil of the intermediate relay is energized, the third normally open contact of the intermediate relay closes. By controlling the forward switch and the rearward switch, the forward and rearward sand spreading control valves are controlled to switch on and off, thereby controlling the front and rear sand spreading. The sand spreading control branch is then turned on through the third normally open contact of the intermediate relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a locomotive excitation control circuit according to an embodiment of the present application;

[0018] Figure 2 This is a schematic diagram of an unloading control circuit according to an embodiment of the present application; DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with embodiments, the purpose of which is only to provide a better understanding of the content of the present invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0020] Reference Figure 1-2 The embodiment of the present application discloses a locomotive emergency braking automatic unloading protection circuit, including a locomotive excitation control circuit and an unloading control circuit. The locomotive excitation control circuit includes a traction branch, a generator excitation branch and a diesel engine speed adjustment branch.

[0021] In this embodiment, the traction branch includes a machine-controlled switch 2AK, a first dynamic connection point, an electro-pneumatic contactor and a traction generator excitation contactor LC. The positive pole of the power supply is connected to the upper port of the master control switch 1AK, and the lower port of the master control switch 1AK is connected to the upper port of the machine-controlled switch 2AK. The first dynamic connection point includes two terminals 7j and 7d. Terminal 7d is connected to the lower port of the machine-controlled switch 2AK, and terminal 7j is connected to the electro-pneumatic contactor. The normally open contacts 1C-6C of the electro-pneumatic contactor are energized and closed, and are connected to the coil of the traction generator excitation contactor LC.

[0022] In this embodiment, the generator excitation branch includes a second dynamic connection point, a wind pressure protection relay 3YK, an overcurrent relay LJ, a grounding relay DJ, a fault excitation contactor GLC and an exciter excitation contactor LLC. The second dynamic connection point includes two terminals 9j and 9d. Terminal 9j is connected to the lower port of the main control switch 1AK, and terminal 9d is connected to the input end of the wind pressure protection relay 3YK. The output end of the wind pressure protection relay 3YK is connected to the overcurrent relay LJ, and the overcurrent relay LJ is connected to the grounding relay DJ. The grounding relay DJ is connected to the upper port of the normally open contact of the traction generator excitation contactor LC. The traction generator excitation The lower end of the normally open contact of contactor LC is connected to the locomotive microcomputer input terminal EXP-A23. The lower end of the normally open contact of traction generator excitation contactor LC is also connected to the upper end of the normally open contact of fault excitation contactor GLC. The locomotive microcomputer output terminal EXP-A41 and the lower end of the normally open contact of fault excitation contactor GLC are connected to the input of exciter excitation contactor LLC. The output of exciter excitation contactor LLC is connected to traction generator excitation contactor LC. The normally closed contact of fault excitation contactor GLC is also connected between locomotive microcomputer output terminal EXP-A41 and the input of exciter excitation contactor LLC. The wind pressure in the ventilation system is detected by wind pressure protection relay 3YK, and the generator excitation branch is controlled to be open or closed according to the wind pressure.

[0023] When the locomotive's main handle is in position 1, lowered, held, or raised, the first dynamic connection points 7j and 7d are connected. When the locomotive's main handle is in position 1, lowered, held, or raised, the second dynamic connection points 9j and 9d are connected. The traction branch circuit is conducting, the coil of the traction generator excitation contactor LC is energized, and the normally open contacts of the traction generator excitation contactor LC are closed. The wind pressure protection relay 3YK, which controls the wind pressure of the ventilation system, is closed. At this time, the generator excitation branch circuit is conducting. After receiving the input signal, the input terminal EXP-A23 of the locomotive microcomputer supplies power to the exciter excitation contactor LLC through the output terminal EXP-A41. The exciter excitation contactor LLC is energized to drive the generator rotor to generate electricity. Specifically, the exciter excitation contactor LLC is connected to the locomotive excitation circuit to control the rotor excitation of the locomotive generator.

[0024] In this embodiment, the diesel engine speed adjustment branch includes a third dynamic connection point and a fourth dynamic connection point. The third dynamic connection point includes two terminals, 5j and 5d. The fourth dynamic connection point includes two terminals, 4j and 4d. Terminal 4d is connected to the input terminal EXP-A51 of the locomotive microcomputer, terminal 5d is connected to the input terminal EXP-A52 of the locomotive microcomputer, terminal 4j is connected to terminal 5j, and terminal 5j is connected to the negative electrode of the power supply. The negative electrode of the power supply is also connected to the input terminal EXP-A61 of the locomotive microcomputer. The third dynamic connection point is closed when the locomotive main handle is in the raised position, and the fourth dynamic connection point is used to close when the locomotive main handle is in the held position or raised position. Closed; when the locomotive main handle is adjusted to the raising position, the third dynamic connection point and the fourth dynamic connection point are closed, the negative pole-5j-5d-terminal EXP-A52 branch is turned on, and the negative pole-4j-4d-terminal EXP-A51 branch is turned on, and a signal is sent to the locomotive microcomputer through the terminal EXP-A52 and the terminal EXP-A51 to control the diesel engine rotor speed to increase; when the locomotive main handle is in the holding position, the third dynamic connection point is closed, the negative pole-5j-5d-terminal EXP-A52 branch is turned on, and a signal is sent to the locomotive microcomputer through the terminal EXP-A52 to control the diesel engine rotor speed to remain unchanged, thereby controlling the speed of the diesel engine.

[0025] In this embodiment, the unloading control circuit includes a sand-spreading pressure relay 6YK, an intermediate relay JXZ and an unloading relay J3. The input end of the sand-spreading pressure relay 6YK is connected to the positive pole of the power supply, the output end of the sand-spreading pressure relay 6YK is connected to the coil input end of the intermediate relay JXZ and the upper end of the first normally open contact JXZ-1 of the intermediate relay JXZ, the coil output end of the intermediate relay JXZ and the lower end of the first normally open contact JXZ-1 of the intermediate relay JXZ are connected to the two ends of the coil of the unloading relay J3, the normally closed contact of the intermediate relay JXZ is connected between the negative pole and the terminal 5j and the terminal 4j in the diesel engine speed control branch, and the normally closed contact of the unloading relay J3 is connected between the grounding relay DJ in the generator excitation branch and the normally open contact of the traction generator excitation contactor LC.

[0026] In this embodiment, the second normally open contact JXZ-2 of the intermediate relay JXZ is also connected between the coil of the intermediate relay JXZ and the first normally open contact JXZ-1 of the intermediate relay JXZ; the lower port of the second normally open contact JXZ-2 is connected to the upper port of the first normally open contact JXZ-1, and the lower port of the second normally open contact JXZ-2 is connected to the terminal 7j of the first dynamic connection point.

[0027] In this embodiment, the unloading control circuit also includes a sand-spreading control branch, which includes a forward sand-spreading control valve, a backward sand-spreading control valve, a forward switch 2DC and a backward switch 1DC. The upper port of the third normally open contact JXZ-3 of the intermediate relay JXZ is connected to the positive pole of the power supply, and the lower port of the third normally open contact JXZ-3 of the intermediate relay JXZ is connected to the upper port of the forward switch 2DC and the upper port of the backward switch 1DC. The lower port of the forward switch 2DC is connected to the input end of the forward sand-spreading control valve, and the lower port of the backward switch 1DC is connected to the input end of the backward sand-spreading control valve. The output end of the forward sand-spreading control valve and the output end of the backward sand-spreading control valve are connected to the negative pole of the power supply; by controlling the forward switch 2DC and the backward switch 1DC, the forward sand-spreading control valve and the backward sand-spreading control valve switches are controlled to control the front and rear sand sprinkling, and the sand-spreading control branch is turned on through the third normally open contact JXZ-3 of the intermediate relay JXZ.

[0028] The control principle of this embodiment is:

[0029] When the locomotive starts to move, close the main control switch 1AK and the machine control switch 2AK, and adjust the main handle to the lowering position, the holding position or the raising position. At this time, the first dynamic connection point and the second dynamic connection point are closed, the traction branch is turned on, the coil of the traction generator excitation contactor LC is energized, the normally open contact of the traction generator excitation contactor LC is closed, the generator excitation branch is turned on, and the input terminal EXP-A23 of the locomotive microcomputer receives the input signal and supplies power to the exciter excitation contactor LLC through the output terminal EXP-A41. The exciter excitation contactor LLC is energized to drive the generator rotor to generate electricity. At this time, the locomotive starts to move. When the main handle is in the raising position, the third dynamic connection point and the fourth dynamic connection point are closed, and signals are sent to the locomotive microcomputer through terminals EXP-A52 and EXP-A51. The locomotive microcomputer controls the diesel engine rotor speed to increase , at this time the locomotive travel speed increases; when the locomotive main handle is in the holding position, the third dynamic connection point is closed, the fourth dynamic connection point is disconnected, and a signal is sent to the locomotive microcomputer through the terminal EXP-A52. The locomotive microcomputer controls the diesel engine rotor speed to remain unchanged, and the locomotive travel speed remains unchanged; when the locomotive main handle is in the lowering position, the third dynamic connection point and the fourth dynamic connection point are disconnected, the locomotive microcomputer has no signal input, and the locomotive microcomputer controls the diesel engine rotor speed to decrease, and the locomotive travel speed slows down; when the excitation function of the locomotive microcomputer fails, the normally open contact of the fault excitation contactor GLC closes and the normally closed contact opens, and the output terminal EXP-A41 of the locomotive microcomputer cannot supply power to the exciter excitation contactor LLC. The exciter excitation contactor LLC loses power and stops working, and the generator rotor loses excitation power and stops generating electricity, causing the locomotive to unload.

[0030] When the locomotive is in emergency braking, the valve handle moves to the emergency braking position, the reconnecting plunger cam rotates, the amplifying lever and the reconnecting plunger move to the right under the action of the spring, and the main air duct is connected to the sand spreading pipe through the plunger groove. The sand spreading pressure relay 6YK is closed by the air pressure of the sand spreading pipe, so that the coil of the intermediate relay JXZ is energized, and the first normally open contact JXZ-1 of the intermediate relay JXZ is closed, so that the coil of the unloading relay J3 is energized, the normally closed contact of the unloading relay J3 is disconnected, and the generator excitation branch is broken. At this time, the excitation contactor LLC of the exciter loses power and stops working, and the generator rotor loses excitation power and stops generating electricity, causing the locomotive to unload; at the same time, the normally closed contact of the intermediate relay JXZ is disconnected , the diesel engine speed adjustment branch is open, the branch of the third dynamic connection point and the branch of the fourth dynamic connection point are open, the locomotive microcomputer has no input signal, and the locomotive microcomputer controls the diesel engine rotor speed to decrease; the second normally open contact JXZ-2 of the intermediate relay JXZ is closed, and the first dynamic connection point supplies power to the coil of the intermediate relay JXZ through the second normally open contact JXZ-2 of the intermediate relay JXZ, so that the intermediate relay JXZ is self-locking; at the same time, the third normally open contact JXZ-3 of the intermediate relay JXZ is closed. At this time, the forward switch 2DC or the reverse switch 1DC can be selected to be closed to control the forward sand spreading control valve or the reverse sand spreading control valve to be energized and turned on, so as to carry out forward sand spreading or reverse sand spreading of the sand spreading pipe.

[0031] With the protection circuit of this utility model, during normal locomotive operation, the traction generator excitation contactor LC is energized, closing the normally open contacts of the traction generator excitation contactor LC connected to the generator excitation branch. This energizes the exciter excitation contactor LLC on the generator excitation branch, driving the generator rotor to generate electricity, allowing the train to operate normally and the diesel engine speed control branch to operate normally, controlling the locomotive's operating speed. During locomotive emergency braking, the generator excitation branch is disconnected, de-energizing the exciter excitation contactor LLC, causing the generator rotor to lose excitation power and cease generating electricity. Simultaneously, the diesel engine speed control branch is disconnected, de-energizing the input of the locomotive microcomputer, and automatically reducing the diesel engine speed. Only after the main handle returns to 0 and the self-valve handle is moved out of the emergency braking position, does the first dynamic connection point open, disconnecting the sand-spreading pressure relay 6YK, de-energizing the coil of intermediate relay JXZ, resetting its normally open and normally closed contacts, and shutting off the self-locking circuit and unloading relay J3. Only after all components are restored can the locomotive resume loading and operation. This ensures that the locomotive automatically unloads and self-locks during emergency braking, preventing misoperation and ensuring safe operation.

[0032] The above description is only a preferred embodiment of the present invention and does not limit the scope of the present invention. Any equivalent changes made using the contents of the present invention specification and its drawings are included in the scope of the present invention.

Claims

1. A locomotive emergency brake automatic unloading protection circuit, characterized in that: It includes locomotive excitation control circuit and unloading control circuit. The locomotive excitation control circuit includes traction branch, generator excitation branch and diesel engine speed adjustment branch. The traction branch includes a traction generator excitation contactor. The normally open contact of the traction generator excitation contactor is connected to the generator excitation branch. The generator excitation branch is connected to the exciter excitation contactor. The normally open contact of the traction generator excitation contactor is connected to the input terminal of the locomotive microcomputer, and the exciter excitation contactor is connected to the output terminal of the locomotive microcomputer. When the traction branch is turned on, the normally open contact of the traction generator excitation contactor closes, the exciter excitation contactor is energized, and the generator rotor is driven to generate electricity. The diesel engine speed adjustment branch is connected to the input terminal of the locomotive microcomputer. The unloading control circuit includes a sand-spreading pressure relay, an intermediate relay, and an unloading relay. The sand-spreading pressure relay is connected to the coil and the first normally open contact of the intermediate relay, and the coil of the intermediate relay and the first normally open contact of the intermediate relay are connected to both ends of the coil of the unloading relay; the normally closed contact of the intermediate relay is connected to the diesel engine speed control branch, and the normally closed contact of the unloading relay is connected to the generator excitation branch; When the locomotive is in emergency braking, the sand-spreading pressure relay receives air pressure and closes, the coil of the intermediate relay is energized, the first normally open contact of the intermediate relay is closed and the normally closed contact is disconnected, the diesel engine speed adjustment branch is disconnected, the unloading relay coil is energized, the normally closed contact of the unloading relay is disconnected, and the generator excitation branch is disconnected.

2. The locomotive emergency brake automatic unloading protection circuit according to claim 1, characterized in that: The traction branch also includes a machine-controlled switch and a first dynamic connection point. One end of the machine-controlled switch is connected to the positive pole of the power supply through the main control switch, and the other end of the machine-controlled switch is connected to the first dynamic connection point. The first dynamic connection point is connected to the traction generator excitation contactor. When the locomotive main handle is in position 1, lowering, maintaining or raising, the first dynamic connection point is closed and the traction branch is turned on.

3. The locomotive emergency brake automatic unloading protection circuit according to claim 2, characterized in that: The first dynamic connection point is also connected to the second normally open contact of the intermediate relay, and the second normally open contact of the intermediate relay is connected between the coil of the intermediate relay and the first normally open contact of the intermediate relay. When the coil of the intermediate relay is energized, the first and second normally open contacts of the intermediate relay are closed, and the first dynamic connection point supplies power to the coil of the intermediate relay through the second normally open contact of the intermediate relay.

4. The locomotive emergency brake automatic unloading protection circuit according to claim 1, characterized in that: The generator excitation branch includes a second dynamic connection point and a wind pressure protection relay. One end of the second dynamic connection point is connected to the main control switch, and the other end of the second dynamic connection point is connected to the wind pressure protection relay. The wind pressure protection relay is connected to the normally closed contact of the unloading relay. When the locomotive main handle is in the lowering position, the holding position or the raising position, the second dynamic connection point is closed, and the wind pressure of the ventilation system drives the wind pressure protection relay to open and close.

5. The locomotive emergency brake automatic unloading protection circuit according to claim 1, characterized in that: The diesel engine speed adjustment branch includes a third dynamic connection point and a fourth dynamic connection point. The third dynamic connection point is used to close when the locomotive main handle is in the raised position, and the fourth dynamic connection point is used to close when the locomotive main handle is in the maintained position or raised position. The third dynamic connection point and the fourth dynamic connection point are connected in parallel, and one end is connected to the normally closed contact of the intermediate relay. The other ends of the third dynamic connection point and the fourth dynamic connection point are respectively connected to the input end of the locomotive microcomputer. When the normally closed contact of the intermediate relay is disconnected, the branch of the third dynamic connection point and the branch of the fourth dynamic connection point are disconnected.

6. The locomotive emergency brake automatic unloading protection circuit according to claim 1, characterized in that: The unloading control circuit also includes a sand spreading control branch, which includes a forward sand spreading control valve and a backward sand spreading control valve. The forward sand spreading control valve is connected to the forward switch, and the backward sand spreading control valve is connected to the backward switch. The forward sand spreading control valve, the forward switch, the backward sand spreading control valve and the backward switch are connected in parallel and in series with the third normally open contact of the intermediate relay. When the coil of the intermediate relay is energized, the third normally open contact of the intermediate relay is closed.

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