Fault analysis and improvement measures of diesel engine speed out of control

1 preface

Yangquan workshop is equipped with 14 Dongfeng 4 diesel locomotive to undertake the traction task of 7 pairs of passenger cars on Shijiazhuang-Taiyuan line. Because of many long ramps, the locomotive works under high load for a long time, the power room vibrates greatly, and the working environment of the combined regulator is harsh. In traction application, the failure of diesel engine speed out of control due to various reasons occurs from time to time. When the diesel engine turns to the long downhill and returns to the handle, it may sometimes overspeed, and the speed may not drop, and sometimes it may stop on the ramp. Although the parts causing the failure are very small, they pose a threat to the safety and running quality of the locomotive. Therefore, in the application, the driver must accurately judge the cause according to the fault phenomenon and deal with it correctly in time to prevent the machine from breaking and possible accidents.

2 failure cause analysis

The speed control system of diesel engine is controlled by electric drive system and combined regulator. Any fault requires a certain time for judgment and treatment, and misjudgment and untimely treatment will affect the quality and safety of operation. Comprehensive analysis of all kinds of faults shows that there are six kinds of faults with high frequency, and examples are given in detail.

2. 1 electric drive system failure

2. 1. 1 SKQ controller failure.

The falling of SKQ plug will cause the diesel engine speed not to rise or fall; The virtual connection speed of the No.7 finger of SKQ does not increase, and the virtual connection speed of the No.8 finger does not decrease: the short circuit between the plug and socket of SKQ will make the handle out of control when it is in non-zero position.

Handling: The above faults can be operated by replacing the terminal (when the plug and socket are burnt out and short-circuited, unplug it first and then replace the terminal).

2. 1.2 CVT driver failure

If the panel light is not on, it is safe to burn. If the frequent burning loss is RBC (positive) virtual connection 1507 and 15 15 lines; 1DZ jump can be turned off artificially; When the panel light is on, the internal circuit of the driver is faulty;

Solution: Replace fuse or short-circuit RBC (positive electrode). Drivers are two groups of devices. When one group fails, the other group can be replaced. When both groups fail, unplug the driving plug, and then manually twist the knob of the stepping motor to realize manual speed regulation.

2. 1.3 stepper motor failure

The wiring of stepping motor is damaged, the bearing is burnt out, the machine is stuck, and the two-phase short circuit between lines occurs.

Treatment: pry the oil supply pull rod by hand to maintain operation.

Example: On October 20th, 2008, 65438, I took 1584 to complete the brake test in Tujiling, and the diesel engine suddenly increased its speed automatically, so I quickly took measures to reduce the speed. No reason was found in loop maintenance. On the 22nd, 2606 times, I encountered the same phenomenon. After careful search, it is found that two of the three wires from the driver to the stepping motor are insulated and worn at the opening of the threading pipe, resulting in "live" grounding. When the two wires are short-circuited due to shaking during locomotive operation, the power supply of the deceleration signal line enters the acceleration signal line, so that the rotation speed automatically rises.

2.2 Joint regulator failure

2.2. 1 The minimum speed pin of the combined regulator is broken.

No 165438+20071October 16, turn back the handle and stop the machine during operation. After confirming that there is nothing abnormal in the protection circuit, I jack up the DLS mandrel and start it again, but it can't be started. Manually pull the oil supply lever to lift and maintain operation. The inspection of Taiyuan warehouse found that the lowest gear pin of the combined regulator broke at 4mm, which caused the diesel engine to stop and could not be started again.

The combined regulator is stepless speed regulation. When the stepping motor receives the pulse signal from the driving power supply, it rotates accordingly. Through the action of master-slave bevel gear and screw pair, the rotary motion of stepping motor is transformed into the vertical motion of piston rod compression speed regulating spring, so as to achieve the purpose of adjusting the speed of diesel engine. The limitation of the minimum rotation speed is accomplished by the screw rotating with the driven bevel gear to prevent the minimum rotation speed stop nail from moving upward with the mating screw. When the nail block works, it is often subjected to certain impact force and shear force, and the diameter of the nail block suddenly changes from 8mm to 4mm, resulting in stress concentration here, which is easy to cause fatigue cracks and fractures in severe cases. Moreover, this fault is hidden and difficult to find.

Treatment: during the operation, put the main handle in the position to maintain the operation.

2.2.2 The minimum speed of the combined regulator prevents the nail from falling off.

The front end of the lowest speed stop nail has a right-handed thread with a length of 8mm and a diameter of 5 mm. When the lowest speed adjusting screw contacts the nail stopper, the direction of force is just opposite to the fastening direction of the screw. The nail stopper is repeatedly subjected to impact force and shear force, which easily causes the nail stopper to loosen or even fall off, and the handle will stop.

Treatment: during the operation, put the main handle in the position of maintaining the operation.

2.2.3 The adjusting screw of the highest speed of the combined regulator falls off.

When this screw falls off, when the handle is lifted to 1000r/min, the diesel engine speed will continue to rise, causing the limit governor to act; If the stop pin falls off at the meshing position of the bevel gear of the stepping motor and the matching bevel gear, the handle will not go back at high speed.

Solution: Open the governor cover, remove the stuck screw and screw in the replacement screw.

2.2.4 The rivet connected between DLS bracket and bracket base is loose and falls off.

On July 3, 2007, the locomotive stopped suddenly during operation. After inspection, it was found that the four 4mm rivets connected between the DLS bracket and the bracket base of the electromagnetic interlocking coil of the combined regulator were loose and fell off, and the bracket body was separated from the chassis.

Although this kind of fault is easy to find, it is very difficult to deal with in the process of locomotive operation. If it is not handled properly, it will easily lead to machine failure. Personally, I think: on the one hand, the working environment of the power room is bad when the diesel engine is running at high load, and the combined regulator vibrates greatly; On the other hand, after the DLS is energized, the iron core moves down and presses down the iron core of the parking valve. The pressure oil (0.65 ~ 0.70 MPa) under the iron core of the parking valve has a reaction force, which finally acts on the rivet connected between the DLS bracket and the bracket base, and the rivet is made of aluminum. Under the repeated action of these two factors, the connecting rivet loosens and falls off, which causes the iron core of the parking valve to move up and open the oil return circuit, so that the pressure oil at the lower part of the power piston leaks downward.

Treatment method: manually pry the oil supply pull rod to maintain operation.

3 improvement measures

3. 1 Open the governor cover regularly for inspection.

Check the interior of the governor in detail with the following table, and tighten the loose screws in time. The wiring of stepping motors should be checked one by one to eliminate hidden dangers in the bud. In addition, the governor cover should not be screwed too tightly, so as not to delay the troubleshooting time.

3.2 Increase the minimum stopping speed.

In order to prevent the lowest speed stop nail from breaking and loosening, it is changed to a left-handed screw. In this way, the strength of the low-speed nail stopper is increased, and the direction in which the low-speed adjusting screw acts on the lowest-speed nail stopper is consistent with the fastening direction of the screw thread of the nail stopper, so that the nail stopper will only become tighter and tighter and will not loosen. This improvement measure is simple and easy, and will not affect the original performance of the nail block.

3.3 Application of welding technology

In order to strengthen the connection strength between DLS bracket and bracket base, both sides of the joint between DLS bracket and bottom plate are welded, and the original rivet connection remains unchanged. This improved method is simple and practical, and will not affect the performance.

4 effect

After the implementation of the above improvement measures, after more than two months of practical application test, the diesel engine did not have the above faults, which showed that the improvement measures were reasonable and feasible, ensured the safety and quality of locomotive operation, and achieved the expected improvement purpose.