METHOD OF CONTROLLING INJECTOR DRIVING CIRCUIT

Abstract

A method of controlling an injector driving circuit that may include a first field effect transistor (FET) that opens and closes a driving power supply to an injector, a second FET having a pulse width modulation control function for supplying a starting current to the injector to open a valve and then supplying a driving current for maintaining an opening driving state to the injector, and a Zener diode. The method may include increasing a valve opening torque to open the injector via turning ON both the first and second FET to obtain a maximum current during a cold start or when an injector valve sticks, turning OFF the second FET before closing the injector, and preventing damage to the Zener diode due to a back electromotive voltage from the injector provided when the valve is closed via turning OFF the first FET after a predetermined amount of time elapses.

Claims

1. A method of controlling an injector driving circuit including a first field effect transistor which is a switching element that opens and closes a driving power supply to an injector, a second field effect transistor having a pulse width modulation control function for supplying a starting current of a value set in advance at a beginning of a valve opening time to the injector for a set time in synchronization with the first field effect transistor when the first field effect transistor is in an ON state to open a valve in a short time and then supplying a driving current for maintaining an opening driving state to the injector having a value greater than or equal to a value necessary to maintain at least one of the opening driving state and a closing driving state to the injector, and a Zener diode for protecting the first field effect transistor from a back electromotive voltage provided by a coil of the injector when the first field effect transistor is turned OFF, the method comprising: increasing a valve opening torque to open the injector via turning ON both the first field effect transistor and the second field effect transistor to obtain a maximum current at least one of (i) during a cold start and (ii) when an injector valve sticks; turning OFF the second field effect transistor at first when the injector is closed thereafter; and preventing damage to the Zener diode due to the back electromotive voltage from the injector provided when the valve is closed via turning OFF the first field effect transistor after a predetermined amount of time elapses.

2. The method of controlling an injector driving circuit according to claim 1, wherein the predetermined amount of time between turning OFF the second field effect transistor and turning OFF the first field effect transistor is an amount of time for the back electromotive voltage from the coil of the injector to be consumed by the first field effect transistor in an ON state and become lower than a voltage value of the Zener diode after at least the second field effect transistor is turned OFF.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0014] FIG. 1 is a circuit diagram illustrating a main part of an injector driving circuit of a preferable embodiment of the invention and a conventional example; and

[0015] FIGS. 2A, 2B, and 2C illustrate waveform flowcharts of control signals in the embodiment and the conventional example illustrated in FIG. 1, in which FIG. 2A corresponds to a normal time, FIG. 2B corresponds to a time when a vehicle is cold or when a valve sticks in the conventional example, and FIG. 2C corresponds to a time when a vehicle is cold or when a valve sticks in the present embodiment illustrated in FIG. 1.

DETAILED DESCRIPTION

[0016] Next, an embodiment of the invention will be described with reference to drawings.

[0017] FIG. 1 is a circuit diagram illustrating a main part of an injector driving circuit used for carrying out a control method by the invention, and the invention can prevent an increase in size of a component and an increase in price by preventing damage to a Zener diode for reducing back electromotive voltage energy due to the injector in an OFF state even when a conventional component is used, which is basically in common with a conventional driving circuit.

[0018] In addition, the control method is the same as that in the conventional example in a normal time, and a detailed description thereof is omitted.

[0019] In addition, the present embodiment is similar to the conventional control method illustrated in FIG. 2B in that valve opening torque is increased to open an injector by turning ON both the first FET T1 and the second FET T2 in an ON state to obtain a maximum current when a vehicle is cold or a valve sticks.

[0020] Further, the control method according to the present embodiment first turns OFF the second FET T2 in an OFF state, and then turns OFF the first FET T1 after a predetermined time elapses, thereby preventing damage to the Zener diode ZD1 due to a back electromotive voltage from the injector I generated when a valve is closed.

[0021] Furthermore, a detailed description will be given based on FIG. 1 and FIG. 2C. When the vehicle is cold or when the valve sticks, a driving signal 1 and a driving signal 2 from a first driving circuit DC1 and a second driving circuit DC2 are transmitted to the first FET T1 and the second FET T2 by a command from the CPU to turn ON both the transistors, so that a maximum injector current (X) (the same as the injector current (C) of FIG. 2B) flows to the injector I, thereby increasing the valve opening torque to open the injector I. After a specified time is reached, unlike conventional control by driving signals from the first driving circuit DC1 and the second driving circuit DC2 by a command from the CPU for simultaneously turning OFF both the first FET T1 and the second FET T2 illustrated in FIG. 2B, the second FET T2 is first turned OFF by the driving signal 1 in an OFF state, and then the first FET T1 is turned OFF by the driving signal 2 after a predetermined time t1 elapses.

[0022] In this instance, even when a back electromotive voltage generated in the injector I is consumed by the first FET T1 in an ON state after at least the second FET T2 is turned OFF, so that an injector current (Y) decreases, and then the first FET T1 is turned OFF, it is possible to prevent damage to the Zener diode ZD1 by a back electromotive voltage V1 from the injector I generated when the valve is closed.

[0023] As described above, according to the present embodiment, it is possible to prevent components (FET and Zener diode (ZD1)) from being damaged even when a control operation is performed such that valve opening torque is increased by having a maximum current in an ON state to open the injector when the vehicle is cold or when the valve sticks using a component and a driving circuit similar to the conventional injector driving circuit.