Diesel engine automatic preheater
The maintenance of diesel engine automatic preheater Liang Zeqing (Huangpu Port Company, Guangzhou, Guangdong Province) detailed analysis of the circuit principle of the Toyota 5F30 forklift automatic preheater. Burning the diesel engine r some mechanical cold air into the hair is known to improve the starting performance, diesel engines are generally equipped with a warm-up starting system. The main components of the preheating starter system are usually installed in the engine cylinder. The glow plug generates a high temperature of about 800*C when it is energized. This effectively helps the misty diesel fuel from the injector to start smoothly. start. When used in severe cold regions, there is also a hot body installed in the intake port of the intake manifold, so that the pre-heating is preheated and converted into hot air required by the engine, so that it can be started normally in cold weather. The traditional way of circuit control of the preheating system is manual control (manual preheating). The manual preheating control circuit is relatively simple and easy to maintain. The disadvantage is that the operator controls the preheating time to be more random, and the heating plug is easily damaged. With the rapid development of electronic technology, an electronic device-centric automatic timing preheater (hereinafter referred to as automatic preheater) with its advanced design, simple operation of long life, and gradually imported in some machinery, especially Mechanically, the starting performance of these machines has been greatly improved, and the life of electrical equipment has been greatly improved. The manual preheating and automatic preheating modes are respectively explained below, and the circuit working principle of the automatic preheater is analyzed in detail. i Manual preheating methods for domestic diesel vehicles and early imported mechanical diesel engines, most of which use manual preheating as shown. Before starting, the operator will turn the warm-up start switch to R1, that is, point B and point R1 are connected. The power supply is supplied to the glow plug by the positive pole of the battery through the fuse, the warm-up start switch and the preheating indicator. Preheating (about ten s), the preheating indicator should turn red within the specified time and give an indication that the operator can start after warming up. At this time, the starting switch is pulled to the starting gear C. At this point, point B is connected with point C and point R2 respectively. At the same time that the starting machine is powered by point C, the preheating plug is heated by the point R2 and the diesel engine is successfully completed. start. Since the preheating indicator light is connected in series with each glow plug, when one of the glow plugs has an open circuit damage, the preheating indicator light is reduced due to the preheating current flowing through it, and the operator glows to notify the operator that the glow plug is faulty. Although the manual preheating method is simple but inconvenient and the manual warm-up time is not standard, the warm-up time is too short, the engine is difficult to start, or the warm-up time is too long, and the glow plug is easily damaged. 2 Automatic preheater The automatic preheater is an all-electronic device with integrated circuit as the core to automatically adjust the warm-up time according to the engine temperature. It transmits an electrical signal reflecting the engine temperature to the automatic preheating device through a sensor installed in the engine cooling water pipe. The internal electronic circuit automatically calculates the power-on time of the glow plug using the maintenance room during the preheating according to the signal. . The engine temperature is low and the warm-up time is long, whereas the warm-up time is short. In this way, the preheating time can be accurately controlled to improve the engine starting performance and the energizing time of the glow plug can be reasonably distributed, the service life of the glow plug can be prolonged effectively, and the related electrical appliances such as the starter and the storage battery can be reasonably protected. Taking the automatic preheater of Toyota 5F30 forklift as an example, the working principle is analyzed in detail. When the circuit is ready to start, first turn the start switch to the ignition gear, then point B and Acc point are connected, and the automatic preheater is energized. Set the engine water temperature to 20 and the temperature sensor (thermistor) has a resistance of about 245kA. The voltage at point A is about 6V and is sent to the 4th pin of the integrated block IC via R3. At this time, the 2 pin is charged to C3. During the C3 charging period, the pins 8 and 9 of the IC output a low level. At the same time, the potential at point B is clamped to a low level due to the action of D2. As a result, the transistors Ti and T4 are turned off, T2, T3, and T5 are turned on, and the preheating is performed. The relay is connected, the glow plug is energized and the preheating indicator lights up for about 15s. After the C3 is charged, the output of the IC's 8 and 9 pins is high, causing the Ti~T5 to be turned over respectively. The preheating relay is de-energized, the contacts are opened, and the glow plug is turned on. Stop the heating preheating indicator and annihilate at the same time, indicating that the preheating is completed. At this time, the starting switch is turned to point C to start the engine warming time. The water temperature is also the temperature of the engine, and the engine temperature is high. The corresponding change process of the working state is: engine temperature t* temperature sensor Rt A point potential i*C3 charging time i*IC 8, 9 foot potential t*Ti, T4 conduction *T2, T3, T5 cut off - electric heating Plug-on-heating time i If the engine temperature is low, the above-mentioned change in the operation will eventually extend the warm-up time. The temperature sensor is a negative temperature coefficient thermistor whose values ​​are at different temperatures as shown in Table 1. It should be noted that the negative pole of D2 is connected to the alternator L (charge meter 1 temperature sensor resistance value and temperature change relationship temperature / ° c resistance / k temperature / ° c resistance / k electric indicator) terminal, the purpose is to When the engine is not started, the potential at point B is clamped by the D2 clamp at the lower potential engine. When the alternator is working normally, the potential of the D2 anode is higher than the cathode potential, so that the potential of D2 is cut off at point B. Whether the potential of the 9-pin output is high or low does not affect the effective conduction of Ti and T4. In other words, as long as the alternator is working normally, the automatic preheater will refuse to heat the glow plug under any circumstances, preventing the glow plug from being energized and lowered. Service life. D3 has two functions: one is to isolate during preheating to prevent the starter relay from malfunctioning; the other is to let the preheating relay draw the glow plug to continue heating through D3 during start-up to help the engine start smoothly. The working principle of the automatic preheater described above is similar to that of other diesel engine machines such as KOMATSU (Komatsu) 4D95S*1 and NISSAN (Nissang) TD27. (Responsible editor Chang Cheng) Titanium Multi-Tool,Bottle Opener,Key Holder,Titanium Keychain BaoJi JiaXin Nonferrous Metal Co., Ltd. , https://www.jiaxin-ti.com