Abstract: This paper introduces a capacitor energy storage high-speed solenoid valve drive circuit. Precise control of the solenoid valve current is achieved by using high-side current sense feedback to control the PWM output. Compared with the traditional solenoid valve drive circuit, the control logic is simple, more in line with the current response characteristics of the solenoid valve, and is beneficial to reduce power consumption and prevent overload of the solenoid valve.

Key words: high speed solenoid valve; drive circuit; capacitor energy storage; high-end current detection

introduction

The high pressure common rail fuel injection system is one of the development directions of diesel engines. The system ensures the engine's requirements for injection timing, precise fuel injection and ideal fuel injection rate by controlling the common rail pressure of the fuel and the quick opening and closing of the injector. The key actuator is a high-speed solenoid valve whose current response characteristics determine that the drive circuit should meet the following basic requirements.

1. Before the electromagnetic control valve is opened, the energy excitation power drive module should inject energy into the solenoid valve at the highest possible rate to ensure that the electromagnetic control valve generates sufficient electromagnetic force during the opening process to shorten the opening response time.

2. After the electromagnetic control valve is opened, the magnetic resistance of the magnetic circuit is very low due to the small working air gap, and the electromagnetic coil can generate a large enough electromagnetic force to ensure the reliable opening of the electromagnetic control valve. A small holding current reduces energy consumption, reduces coil heating, and facilitates rapid closing of the solenoid control valve.

In summary, the design of the solenoid valve drive circuit requires that the corresponding ideal drive current should be maintained at different stages of the solenoid valve.

At present, the common solenoid valve driving circuits are roughly classified into four types: adjustable resistance type, double voltage type, pulse width modulation type and dual voltage pulse width modulation type.

Among them, the adjustable resistance type driving circuit has a simple structure but a large power consumption, and the dual voltage type power consumption is reduced but still not ideal. Both pulse width modulation and dual voltage pulse width modulation use PWM to control the solenoid valve to maintain current, which greatly reduces power consumption. The advantage of the dual voltage pulse width modulation compared to the pulse width modulation is that the solenoid valve holding current is provided by the battery, reducing the load on the DC/DC boost circuit.

However, a common problem with the above several drive circuits is that it is difficult to ensure the normal opening of the solenoid valve in the case where the injection pulse width timing overlaps. This is because when the two injection signals overlap in phase, the conduction of one of the solenoid valves will cause the voltage of the DC/DC booster circuit to drop instantaneously, and the voltage at this time will not guarantee the normal opening of the other solenoid valve.

In the background of this paper, the diesel high-pressure common rail rotor machine is equipped with double injectors before and after the double-injector, that is, the pilot injector and the main injector are independently controlled, and the two injectors are injected in some work. overlapping. Therefore, it is necessary to design and develop a new type of drive circuit to ensure that the injector can work normally under this condition, that is, to ensure the injection timing and the precise injection amount.

Capacitor energy storage

High speed solenoid valve drive circuit

Main circuit

The principle of the capacitor energy storage high-speed solenoid valve drive circuit is shown in Figure 1. The pilot injection pulse width signal INJ1 of the front cylinder of the rotor machine and the pilot injection pulse width signal INJ3 of the rear cylinder pass through the NOR gate, and are input to the high-end driver chip to drive the high-end power MOS transistor Q1, and the DC/DC is boosted. The 100V power supply is charged to the capacitor C1 after being turned on by Q1, and Q1 is turned off during the injection pulse width period. The PWM generator controls the duty cycle of the 12V power supply input through the power MOS transistor Q2. The sources of Q1 and Q2 are connected to the upper ends of the solenoid valves L1 and L3 through diodes D11 and D12, respectively. The functions of D11 and D12 are to isolate the power supplies of two different voltages of 100V and 12V. INJ1 and INJ3 are selected by low-end power MOS transistors Q4 and Q5, respectively. D13 and D14 are freewheeling diodes. The current sense amplifier is connected to the PWM generator for feedback control.

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