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Modern large-scale high-speed automobiles (mainly diesel vehicles) are equipped with an exhaust-reduction auxiliary brake system. The basic working principle of the exhausted retarded auxiliary brake system is to use an exhaust throttle valve disposed in the exhaust passage to block the engine exhaust passage to increase the power loss of the intake, exhaust, and compression strokes in the engine. Force the engine to reduce the speed, so as to achieve the purpose of reducing the speed in a short time.
The general structure of the exhaust-assisted auxiliary brake system is shown in Fig. 1. The exhaust slow release switch 2 is controlled by the driver. When needed, the switch is pulled to the closed position, the power is turned on, and the exhaust slowness indicator 9 is lit, indicating that the exhausted retarded auxiliary brake is in an operating state. When the accelerator pedal is not stepped on and when the clutch is in the engaged state, the accelerator switch 3 and the clutch switch 4 are in an on state, and current flows through the solenoid valve 7 to open the compressed air passage. The compressed gas from the air cylinder 8 enters the control cylinder 6 and pushes the push rod of the control cylinder forward to close the exhaust throttle valve 5 installed on the exhaust passage to rapidly reduce the engine speed, thereby rapidly reducing the vehicle speed.
1. The exhaust gas retarder type auxiliary brake system should pay attention to the problems in use. a. The working principle of the exhaust gas retarder type auxiliary brake system is to use exhaust resistance to increase the intake, exhaust and compression strokes of the engine. The power loss decelerates the car, so the engine must be in power transmission with the driveline. That is to say, when the clutch is depressed (the engine is disconnected from the transmission) or the transmission is in the neutral position, the exhaust-revving auxiliary brake system is Can not afford to reduce the speed of the role.
b. When the exhaust slow release switch 2 is turned on and the exhaust slowness indicator 9 is lit, when the exhaust retarder type auxiliary brake is in the working state, if the driver depresses the accelerator pedal or the clutch pedal, the electromagnetic The current of the valve 7 is temporarily cut off, the exhaust throttle valve 5 is opened, and exhaust deceleration is stopped; when the above-described pedal is released, the exhaust-rate retarding auxiliary brake system is again operated. Therefore, when using this system, you must never step on the accelerator pedal or the clutch pedal; when you are not using the system, you must turn off the exhaust slow release switch 2 in time, and the exhaust slowness indicator should be in the off state.
c. In the rain and snow days, when the road adhesion coefficient is low, when driving on a downhill road, the vehicle needs to be generally decelerated (such as crowded vehicles in front or corners, etc.). Reasonable use of exhaust retarder can reduce driving speed. The operating frequency of the braking system reduces the wear and tear of the service brake material and the increased wear of the tire due to braking, and reduces the occurrence of brake runaway.
2. Maintenance and Common Fault Diagnosis of Exhaust Relief Auxiliary Braking System Taking the Guilin GL6121 coach as an example, the maintenance and common fault diagnosis of the exhaust-revving auxiliary brake system are introduced.
2.1 Check exhaust release switch Pull exhaust release switch, exhaust indicator light should light. If the exhaust slowness indicator does not light, check the lamp, exhaust slowing switch, and the exhaust retard auxiliary brake fuse (5A) in fuse box #2.
2.2 Checking the Acceleration Switch The accelerating switch has three terminals, one of which is empty. The other two terminals are closed when the exhaust-relief switch is closed, and the accelerator pedal is turned off.
2.3 Check the brake fluid pressure of the clutch switch clutch switch. It has been adjusted to 392kPa-784kPa at the factory. Depress and release the clutch pedal to check the switch action.
2.4 Check the solenoid valve with a multimeter. The file detects the solenoid coil. Decompose the solenoid valve Check the contact surface of the valve plug. If the valve plug is stuck, trim it with fine sandpaper and lubricate with engine oil. It is also possible to check the air intake passage using compressed air. When the power is turned on, the air intake valve of the solenoid valve opens and the gas can pass through; the air intake valve closes when the power is turned off.
2.5 Check the control cylinder Pull the open end of the push rod fork joint of the control cylinder with a tension gauge. When the stroke of the push rod is 26.2mm, the reading of the tension gauge is 225.4N±9.8N; when the stroke of the push rod is 48.6mm (maximum stroke) The tension gauge reading is 318.5N ± 9.8N, and the control cylinder operates normally.
2.6 Checking the Exhaust Throttle Valve Figure 2 shows the inspection of the exhaust throttle valve. The fork joint of the control cylinder push rod is disengaged from the exhaust throttle valve arm 2 and the action of the exhaust throttle valve is checked. It is required that the exhaust throttle valve and the interior of the exhaust pipe are parallel when not in operation, and can work shut down. The assembly angle of the throttle valve can be estimated based on the angle of the valve arm shown in the inspection drawing without disassembling the assembly.
2.7 Exhaust Relief Type Auxiliary Braking System Test a. The engine is started and operated so that the pressure of the air cylinder reaches the normal working pressure and the flame is extinguished.
b. Pull the exhaust slow switch and check that the exhaust slow indicator light is on. At the same time, when the exhaust slow release switch is operated, a “click†sound should be heard, indicating that the air in the air reservoir enters the working chamber of the control cylinder and the exhaust throttle valve operates.
c. Depress the clutch pedal, check that the exhaust speed indicator light should be off, and there is a "click" sound of deflation until the exhaust slow brake is released.
d. Depress accelerator pedal for the same check as c above. In the process of depressing the accelerator pedal, the acceleration switch k is turned off when the accelerator pedal free stroke has not ended.
2.8 Diagnosis of Common Faults Common failures and possible causes of the exhaust-assisted auxiliary brake system:
Symptom: Pulling the exhaust slow switch, but the exhaust slow brake still does not work, its indicator light is not bright.
Possible causes: 1. Fuse or line break 2. Exhaust slow switch malfunction.
Symptom: Pulling the exhaust release switch, the exhaust release indicator light is on, but the exhaust release brake does not operate.
Possible causes: 1. Accelerated switch or line disconnection 2. Clutch switch fault or line disconnection 3. Solenoid valve coil disconnection or ground fault 4. Electromagnetic wide operation failure 5. Air pressure too low 6. Exhaust section Poor flow between actions.
Symptom: Depressing the clutch pedal, the effect of exhaust retard braking is not released.
Possible causes: Clutch switch malfunction (when the oil pressure system is operating normally).
Symptom: When the accelerator pedal is depressed, the effect of exhaust retard braking is not released.
Possible causes: Accelerated switch failure or maladjustment.
Symptom: The valve core of the solenoid valve is not reset.
Probable causes: 1. The electromagnetic vent hole is blocked 2. The spool is malfunctioning (stagnant).
Symptoms: Exhaust throttle reading normal, but the valve is not strict.
Possible causes: 1. Poor adjustment of the limit bolt 2. Eccentric or poor spool 3. The valve is not closed due to carbon deposition.