JPH0799112A - Device for driving electromagnetic load - Google Patents

Abstract

PURPOSE: To maintain an interception speed within a permissible error as small as possible by a method wherein voltage dropping for driving second switching means is set using a current source. CONSTITUTION: This embodiment has an electromagnetic load 1, and in particular, an electromagnetic injection valve of an internal combustion engine and switching means 2 connected thereto in series. The electromagnetic load 1 is connected to a reflux circuit (free wheel circuit) in parallel. Preferably, this reflux circuit has second switching means 3, and the switching part is connected to a diode 4 in series. Similarly, the switching means 3 is realized as a transistor, in particular as a field-effect transistor. Further, drive means 5 for driving the switching means 2 is provided. Further, the second switching means, namely, a source terminal of the transistors 3, is connected to a resistor 6, and is driven by voltage dropping between the resistors 6 set using a current source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for driving an electromagnetic load, and more specifically, a series circuit of an electromagnetic load and a first switching means, and an electromagnetic load return circuit having a second switching means. , An apparatus for driving an electromagnetic load having a driving means for driving these switching means.

[0002]

Devices of this type for driving electromagnetic loads are DE
-Known from OS 4020094. In the publication,
An apparatus for driving an electromagnetic load is described which has a series circuit consisting of the electromagnetic load and a first switching means. The second switching means is connected to the return circuit (freewheel circuit) for the electromagnetic load. Further, driving means for driving these switching means is also provided.

In this device, the switching time or the shut-off speed, and thus the opening and closing time of the solenoid valve, are related to various parameters, so that, for example, in the case of fuel injection valves
Undesirable variations in the injected fuel quantity occur. As a result, harmful substances have an undesirable effect on the environment.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a circulating circuit capable of interrupting at a predetermined breaking speed in an apparatus for driving an electromagnetic load. Furthermore, the breaking speed must be limited in order to protect the corresponding circuit elements from large voltage fluctuations. Furthermore, in order to keep the current reduction rate tolerance of the solenoid valve, and hence the injection quantity tolerance, as small as possible, it is necessary to maintain the shutoff speed within the smallest possible tolerance. .

[0005]

In order to solve the above problems, according to the present invention, a series circuit of an electromagnetic load and a first switching means, and an electromagnetic load return circuit including a second switching means. In a device for driving an electromagnetic load having a driving means for driving these switching means, a configuration is adopted in which a voltage drop between resistors for driving the second switching means is set by using a current source. .

[0006]

With such a structure, it is possible to realize a recirculating circuit capable of shutting off having a predetermined shutoff speed. In that case, the breaking speed is limited, so that variations in the breaking speed can be small tolerances.

[0007]

An embodiment of the invention is shown in the drawing and will be explained in more detail below.

As shown in the circuit diagram of FIG. 1, an apparatus for driving an electromagnetic load has an electromagnetic load 1, in particular an electromagnetic injection valve of an internal combustion engine, and a switching means 2 connected in series with it.

In the illustrated embodiment, the switching means 2 is formed as a field effect transistor, but it can also be realized using another switching means such as a transistor. The terminal of the electromagnetic load 1 on the side opposite to the switching means 2 is connected to the battery voltage U. The source terminal of the transistor 2 on the side opposite to the electromagnetic load 1 is connected to the ground.

A freewheeling circuit is connected in parallel to the electromagnetic load 1. This return circuit preferably comprises a second switching means 3, the switching part of which is connected in series with a diode 4. In the example shown, the switching means 3 are likewise realized as transistors, in particular field-effect transistors. The anode of diode 4 is load 1
It is also connected to the drain terminal of the transistor 2. The cathode of the diode 4 is connected to the second switching means 3.

The device further comprises drive means 5 for driving the switching means 2. The drive means 5 is preferably realized as a microcomputer.

The current reduction circuit (de-energization circuit) is shown at 13. In the illustrated embodiment, this current reducing circuit connects the cathode of the diode 4, the source terminal of the transistor 3 and the connection point between the load and ground. In a simple embodiment, the current reduction circuit is realized as a Zener diode, the anode of which is connected to ground and the cathode of which is connected to the load.

The source terminal of the transistor 3 is connected to the resistor 6. The other terminal of the resistor 6 is connected to the first terminal of another resistor 8 via another switching means 7. The connection point between the resistor 6 and the other switching means 7 is connected to the gate terminal of the transistor 3.

The driving means 5a is another switching means 12
Supply a drive signal to. When the other switching means 12 becomes conductive, the connection point 9 is connected to the second terminal of the resistor 8. The connection point 9 is connected to the first terminal of the resistor 10 and to the reference voltage URef via the resistor 11. The emitter of the switching means 12, the second terminal of the resistor 8 and the second terminal of the resistor 10 are connected to each other. The base terminal of the switching means 7 is supplied with the potential of the connection point 9. The drive means 5a is preferably the switching means 2
It is the same drive means that supplies a drive signal to the.

Switching means 7, resistors 8, 10, 11
And the switching means 12 forms a current source 20 which can be interrupted.

The switching means 7 and 12 are preferably realized as bipolar transistors.

The function of this device will be described with reference to FIG.
By driving the first transistor 2, the electromagnetic load 1 is connected between the battery voltage U and ground. As a result, a current flows through the load.

The time waveforms of various voltage, current and drive signals are illustrated in FIG. FIG. 2A shows the output signal of the driving means 5 supplied to the transistor 2. The drive means 5 outputs a pulse-shaped drive signal. In that case, the pulse duration or pulse width is associated with a current or voltage control not shown.

The drive starts at time T1. At time T1, the transistors 2 and 3 are driven,
Both transistors are closed, which allows current to flow. As shown in FIG. 2B, the current flowing through the load increases from this point. When the current reaches the set threshold S1 at time T2, the transistor 2 opens.

Since the transistor 3 is in the closed state, the freewheeling circuit including the diode 4 and the transistor 3 becomes active. This causes the current to slowly decrease, reaching the lower threshold S2. When this threshold is reached, transistor 2 is closed and the current increases again to threshold S1. This process is repeated until the driving ends at time T3.

At this time, the transistor 2 is driven and opened. At the same time, the transistor 3 is driven and opened.
The freewheeling circuit is no longer active due to the opening of the transistor 3 and the current reducing circuit 13 causes a rapid current reduction. This causes the current through the load to decrease to zero very quickly. This results in extremely short turn-off times. The current is reduced relatively slowly while the transistor 2 is repeatedly turned on and off. As a result, the on / off time becomes relatively long.

The device shown is preferably used to drive a solenoid valve which controls the fuel metering of a motor vehicle. Figure 2
In (c), the stroke of the solenoid valve needle is shown. The solenoid valve moves from time T1 and reaches the other end position at time T2. It returns to the original position again between time points T3 and T4. The fuel is metered between times T2 and T4.

FIG. 2D shows the drive signal of the transistor 3. The current source 20 drives the transistor 3.
Done through. The transistor 3 becomes conductive when a predetermined voltage of about 10 volts is applied between the source terminal and the gate terminal.

The driving is performed as follows. At time T1, as shown in FIG. 2 (e), the transistor 12 turns into the driving means 5
Driven by a, this transistor opens. This causes the voltage at point 9 of the voltage divider formed by resistors 10 and 11 to increase, closing transistor 7. The switching state of the transistor 7 is shown in FIG.

When the transistor 7 is closed, a constant current flows through the resistor 6. This causes a constant voltage drop across the resistor 6. The transistor 3 is driven by this constant voltage, the transistor 3 is closed as shown in FIG. 2D, and the freewheeling circuit becomes active.

A constant current is supplied to the resistor 6 via the current source 20. The constant current flowing through the resistor 6 causes a constant voltage drop across the resistor 6, which is used to drive the transistor 3.

At time T3, the transistor 12 is driven by the drive.
Are conducted. The connection point 9 is thereby connected to earth. As a result, the transistor 7 cuts off the current flowing through the resistor 6. This reduces the voltage across resistor 6 to zero and opens transistor 3.

The period until the transistor 3 opens is
About the value of the resistor 6, the voltage across the resistor 6 and the transistor 3
Related only to the gate-source capacitance constant of. Resistance 6
If the current flowing through is regulated to a constant value, a constant voltage is generated at the gate of the transistor 3. The reproducibility and accuracy of the switching time of the solenoid valve are almost related to the voltage drop across the resistor 6.

The Zener diode 14 connected in parallel to the resistor 6 is used to set the exact voltage drop across the resistor.

When the injection ends at time T3, the current source is cut off by driving the transistor 12. As a result, no current flows through the resistor 6, and the voltage between the gate and the source collapses. As a result, the transistor 3 is opened and the freewheeling circuit becomes inactive. The breaking speed is almost related to the capacitance between the gate and the source and the resistance 6.

Alternatively, the interruptable constant current source 20 shown in FIGS. 3 (a) and 3 (b) can be used.

In the embodiment shown in FIG. 3A, corresponding elements are designated by the same reference numerals. Compared to the embodiment shown in FIG.
Are connected. In that case, the base of this transistor is connected to the collector and the connection point 9. The emitter is connected to the terminal of the resistor 10 on the side opposite to the ground.

By using this transistor, the voltage drop of the voltage divider formed by the resistors 10 and 11 can be set more accurately. Thereby, the switching time of the transistor 7 can also be controlled accurately.

In the embodiment shown in FIG. 3B, the resistor 6 is connected to the drain terminal of the transistor 16. The source terminal of the transistor 16 is connected to the transistor 18 via the resistor 17, and this transistor is driven by the driving means 5a. The connection point between the resistor 17 and the transistor 18 is connected to the gate terminal of the transistor 16.

Transistor 16 can preferably be realized as a self-conducting field effect transistor or as an N-channel depletion type field effect transistor.

When the transistor 18 becomes conductive, a constant current flows through the resistor 6. When the transistor 18 opens, the current is cut off. The constant current source is formed almost only by (self-conducting) N-channel transistor 16 and resistor 17.

Other constant current sources not shown can also be used.

[0038]

As is apparent from the above description, according to the present invention, it is possible to realize a reflux circuit capable of shutting off at a predetermined shutoff speed in an apparatus for driving an electromagnetic load.
Further, since the breaking speed can be limited, the circuit element can be protected from a large voltage fluctuation. Furthermore, since the variation of the shutoff speed is within a slight tolerance, the tolerance of the current reduction speed of the solenoid valve, and hence the tolerance of the injection amount, can be suppressed as small as possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a first exemplary embodiment of the present invention.

2 is a waveform diagram showing signals at various points in the circuit of FIG. 1 over time.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 Electromagnetic Load 5, 5a Driving Means 20 Current Source

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Bernd Wichert, Federal Republic of Germany 71394 Kernen Wiesenstraße 49 (72) Inventor Werner Zimmermann, Federal Republic of Germany 70435 Stuttgart Droizestrasse 9 Base

Claims (5)

[Claims] 1. An electromagnetic load having a series circuit of an electromagnetic load and a first switching means, an electromagnetic load return circuit having a second switching means, and a driving means for driving these switching means is driven. A device for driving an electromagnetic load, wherein a voltage drop between resistors for driving the second switching means is set by using a current source. 2. Device according to claim 1, characterized in that the current source comprises a self-conducting field effect transistor. 3. A transistor as the switching means,
Device according to claim 1 or 2, characterized in that in particular field effect transistors are used. 4. Device according to claim 1, characterized in that at least one microcomputer is provided as drive means for the switching means. 5. The device according to claim 1, wherein the load is an electromagnetic injection valve of an internal combustion engine.