Internal combustion forklift daily maintenance and common troubleshooting methods

Nov 18th,2024 1168 Views

Internal combustion forklift daily maintenance method:

1. Check whether the thermostat works normally.

2, check the transmission shift work is normal.

3. Check the tightness of the fan belt.

4, check whether the diesel tank oil inlet filter is blocked or damaged, and clean or replace the filter.

5. Check and adjust the valve clearance.

6. Check and adjust the gap between the brake disc and the brake drum of the hand and foot brake.

7. Check whether the generator and starter motor are firmly installed, whether the connector is clean and firm, and whether the carbon brush and commutator are worn.

8. Replace the oil in the oil pan, check whether the crankcase ventilation nozzle is intact, and clean the oil filter and diesel filter element.

9, check the cylinder pressure or vacuum degree.

10. Check whether the wheel installation is firm, whether the tire pressure meets the requirements, and remove the debris embedded in the tread.

11, due to maintenance work and separated parts, when reassembled to carry out forklift road test.

(1) Braking performance in different degrees should be free from deviation and snaking. On steep slopes, when the hand brake is tightened, it can stop reliably.

(2) Listen to the engine in the case of acceleration, deceleration, heavy load or no-load operation, there is no normal sound.

(3) After a road test, check the brake, transmission, front axle housing, gear pump for overheating.

(4) Whether the lifting speed of the cargo fork is normal and whether there is shaking.

12. Check whether the multi-way reversing valve, lifting cylinder, tilt cylinder, steering cylinder and gear pump work normally.

Internal combustion forklift common faults and troubleshooting methods

The braking system of the internal combustion forklift truck is the front wheel braking of the oil pressure shoe type. The brake pedal is stepped, the brake master pump outputs low pressure brake fluid, and enters the transmission control valve all the way to cut off the pressure oil path leading to the clutch. The other way into the vacuum supercharger, pressurized into the wheel brake brake in the brake pump, expand the brake shoe to achieve wheel braking. If the brake system of the forklift truck is underpowered, it may be the mechanical part, or the oil circuit system or the vacuum booster system is faulty.

1. Mechanical part

(1) Improper adjustment of the gap between the brake shoe and the brake drum or serious wear of the brake shoe; Should be adjusted or replaced.

(2) The size of the brake drum exceeds the limit, resulting in a large pump stroke, and the brake fluid discharged from the total pump is not enough to push the two brake pumps (the standard size of the brake drum is ∮420mm, if it exceeds ∮426mm, it should be replaced).

(3) the curvature radius of the brake shoe is less than the radius of the brake drum (under normal circumstances, it should be about 0.5mm), resulting in the brake shoe "eating the middle", so that the contact area of the brake shoe and the brake drum can not meet the requirements.

(4) the oil seal in the drum and the brake pump leak oil, causing the brake drum and brake shoe to have oil, so that the brake friction coefficient is reduced; The oil seal should be replaced, and the brake drum and shoe should be cleaned.

(5) the free travel of the brake pedal is too large; Should be adjusted.

2. Oil circuit system

(l) The hydraulic forklift brake system has air or joint oil leakage; Remove air from the system or replace leaking joints.

(2) The sealing performance of the brake master pump, sub-pump, vacuum booster cylinder (auxiliary cylinder) and transmission cut-off valve is poor, the pressure can not be maintained during braking, and there is oil leakage or oil return phenomenon; The seals should be replaced.

3, vacuum pressurization system

(1) Insufficient vacuum supercharger is a common fault of vacuum supercharger system.

The type 60-II vacuum supercharger is composed of a booster cylinder (auxiliary cylinder), a control room and a vacuum strengthening room (power cylinder). The inner part of the control valve is separated by a diaphragm into two chambers. The vacuum valve and the air valve are integrated and rely on spring action. When the forklift truck is not braking, the vacuum valve and the center hole of the diaphragm seat are kept in a normally open state, while the air valve is kept in a normally closed state. The power cylinder is divided into a front cavity and a back cavity by a skin film. The front cavity is connected with the vacuum tank, and the vacuum tank is connected with the vacuum pump through a tube. The rear chamber is connected to the right chamber of the control valve through a tube.

When the engine starts without stepping the brake pedal, the front and back cavities of the vacuum supercharger power cylinder are connected with the left and right cavities of the control valve, and have the same vacuum degree, so under the action of the return spring, the power cylinder skin film and the center push rod are in the backward limit position.

When the engine starts, step on the brake pedal, when the oil pressure of the total pump rises to a certain value, the brake oil enters the supercharger, and flows to the front left and right brake sub-pump through the center hole of the auxiliary cylinder piston; All the way, push the control valve piston to the right, the diaphragm seat first closes the vacuum valve, so that the left and right two chambers of the control valve are isolated (equivalent to the front and back of the power cylinder spleen diaphragm), and then open the air valve, so that the back chamber of the power cylinder is filled with air, while the front chamber still maintains a certain degree of vacuum. Therefore, the pressure difference generated by the front and back cavities forces the power cylinder skin film to drive the push rod forward, and the push rod first closes the center hole of the auxiliary cylinder piston with the top steel ball, and then pushes the piston forward to pressurize (pressurize) the oil from the main pump, and the brake branch pump thus obtains higher oil pressure, so that the whole vehicle obtains good braking efficiency.

From the above working principle, it can be seen that the vacuum degree of the power cylinder of the forklift brake system determines the quality of the supercharging effect of the vacuum supercharger. The reasons for the decrease of the vacuum degree of the power cylinder are: the performance of the vacuum pump, vacuum valve and air valve is poor or the power cylinder skin film is damaged, etc., among which the poor seal of the vacuum valve and the air valve is more common. If the vacuum valve is not sealed, when the pedal is pressed, although the vacuum valve is closed, air can still permeate the front chamber of the power cylinder from the vacuum valve and the seat, causing the vacuum degree of the power cylinder to decrease, so that the push rod thrust is greatly reduced, the auxiliary cylinder can not form high pressure, thus reducing the braking performance of the whole car.

Similarly, if the air valve leaks, the front chamber of the power cylinder has penetrated air when the brake pedal is not stepped on, and the vacuum degree of the power cylinder will be greatly reduced when the pedal is stepped on. Therefore, the vacuum valve and air valve in the control valve are common points of failure when the vacuum supercharger is undercharged. From our years of maintenance practice, vacuum pump oil is a fatal factor causing damage to vacuum supercharger. Because the oil into the vacuum system will cause damage to the valve and the skin film, if the oil pumping phenomenon occurs, it is necessary to repair or replace the vacuum pump in time. In addition, the vacuum pump performance is not good, the connection pipeline is damaged and leaky, and the cloth such as Banyan pipe Park Kuang makes the pressure of Haocheng direct supercharger insufficient.

(2) After the failure of the vacuum booster system, it should be judged and eliminated in the following ways: ① Check the vacuum pump

a. Manual inspection: remove the tube joint of the vacuum pump, plug the interface of the vacuum pump tube with your finger, start the engine, if the finger is sucked, the vacuum pump is fine; If the suction is very weak, the vacuum pump is faulty and must be repaired. b. Vacuum gauge test: Connect the vacuum gauge to the vacuum tube and start the engine. No matter the engine is at any speed, the vacuum degree shall not be less than 500mm mercury column, otherwise the vacuum pump should be repaired or replaced.

② Inspection of vacuum supercharger

A. Listen first, that is, after starting the engine for a few minutes to turn off, step down the brake pedal several times, each time you can hear the vacuum supercharger emit a "hiss, hiss" sound, if the sound is large, and gradually weaken with the increase of the number of steps, you can basically conclude that the vacuum supercharger performance is good.

b. Start the engine, one person step on the brake pedal and keep still, so that the vacuum valve and the air valve in the control valve are closed at the same time, and the brake is in a balanced state (at this time, with a wisp of cotton yarn placed at the air filter port of the vacuum supercharger, there should be no suction phenomenon); The other person removes the rear cavity air tube of the power cylinder, and quickly plugs the joint of the air tube mouth and the rear cavity tube with his finger. If the tube mouth has suction, it indicates that the vacuum valve is not sealed and should be repaired or replaced; If the joint has suction, it means that the power cylinder skin film has been damaged and must be replaced.

c. Start the engine, do not step on the brake pedal, put a wisp of cotton yarn on the air filter port of the control valve, if the cotton yarn is sucked, it indicates that the air valve leaks, the control valve must be removed and the rubber ring or air valve replaced.

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