JPH0688545A - Method and device for driving electromagnetic load - Google Patents

Abstract

PURPOSE: To prevent, to the greatest possible extent, emission of noise generated in a method and an apparatus for controlling an electromagnetic load, particularly an electromagnetic valve of an injector in an internal combustion engine. CONSTITUTION: An electromagnetic valve 120 of an injector in an internal combustion engine is switched on and off by a switch means 110. When rpm N is low, a return current switch 165 is actuated when the current flowing through the electromagnetic valve is turned off. Thus, the switch off duration of the electromagnetic valve is extended by the consequent return current. When rpm N is high, the return current switch is turned off and electric current is rapidly eliminated by a quenching diode 150, thereby further shortening the switch off duration. In intermediate rpm, the return current switch is turned on after the elapse of a predetermined period of time. Thus, the switching time of the electromagnetic valve is set in accordance with the rpm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for driving an electromagnetic load, in particular an electromagnetic valve of an injector of an internal combustion engine.

[0002]

A method of this kind for driving an electromagnetic load and a device of this kind are known from SAE paper 850542. The document describes a control device for a fuel pump, in which an electronic control unit controls an electromagnetically operated valve provided in association with the fuel pump via a power output stage. The control unit determines the desired time points for starting and ending the feeding of the fuel pump according to the operating state of the internal combustion engine. The control unit calculates the driving time of the power output stage on the basis of these desired times, so that the solenoid valve is in a position where the fuel pump does not deliver fuel or ends delivery. In that case, the drive pulse is generated a predetermined time before the time when the solenoid valve is operated and the fuel is not fed or the feeding is ended.

This delay is due to the switching time of the solenoid valve. The switch-on time represents the delay between the drive pulse and the closing of the solenoid valve. The switch-off time represents the delay between the drive pulse and the opening of the solenoid valve.

From DE-OS 4018320 there is known a device for driving an electromagnetic load, in particular an electromagnetic valve of an injector of an internal combustion engine. In this device, in order to adjust the injection characteristic, the solenoid valve is driven for a short time to interrupt the injection or delay the pressure buildup. If such driving is performed to adjust the injection characteristic, the short switching time of the solenoid valve becomes long. In this device, the switching time cannot be changed to determine the start and end of injection.

In the device according to the state of the art, noise emissions which are problematic occur especially when the rotational speed is low.

[0006]

SUMMARY OF THE INVENTION The object of the invention is to prevent as much as possible the emission of noise in electromagnetic loads, in particular in methods and devices for actuating solenoid valves of injectors.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a method and a device for driving an electromagnetic load, in particular an electromagnetic valve of an injection device of an internal combustion engine, in which injection start and / or injection end In order to determine, the electromagnetic load switching time can be set according to the operating parameters during driving.

[0008]

According to the device of the present invention, it is possible to greatly prevent the emission of noise.

When the number of revolutions is low, the recirculation switch is activated when the current flowing through the solenoid valve is turned off, and the current recirculates, thereby prolonging the switch-off time of the solenoid valve. When the speed of rotation is high, the freewheeling switch opens and the current is rapidly extinguished by the quenching diode. This reduces the switch-off time. At the rotation speed in the middle range, the reflux switch is opened after a predetermined time has elapsed. Thus, the switching time of the solenoid valve is the operating parameter,
Especially, it is set according to the rotation speed.

[0010]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 schematically shows an embodiment of the device of the present invention. The electronic control unit 100 is connected to the first switching means 110. One terminal of this switching unit is connected to ground. The other terminal is connected to the battery voltage UBAT via an electromagnetic load 120 (hereinafter also referred to as an electromagnetic valve or a solenoid valve) and a resistor 130. The electronic control unit 100 is further connected to various sensors 105 having at least one speed sensor.

The output line of the electronic control unit which drives the first switching means 110 is a fast deenergizing diode 15
0 through the first switching means 110 and the solenoid valve 12
It is connected to the connection point between 0. This connection point is further connected to the battery voltage UBA via the free wheeling diode (free wheel diode) 160 and the second switching means 165.
Connected with T. The second switching means 165 is also referred to below as a return switch. Similarly, a signal is supplied to the reflux switch 165 from the electronic control unit 100.

The freewheeling switch 165 and the first switching means 110 are preferably formed as field effect transistors. However, it can be formed by other means. The resistor 130 is used as a measuring device that detects a current flowing through the solenoid valve 120.

Usually, in an inductive load such as a solenoid valve, a free wheeling diode 160 connected in parallel with the inductive load is provided. Furthermore, a so-called fast disabling diode 150 is connected between the switching input of the switching means 110 and the inductive load. As a result, the switch-off current drops very rapidly. As a result, the switching time of the solenoid valve is very short. This is necessary especially when the rotational speed is high. This is because otherwise the fuel metering will be inaccurate. This short switch-off time is obtained by rapidly deactivating (suppressing) the electromagnetic valve current in which a predetermined counter electromotive force is induced by the inductance of the electromagnetic coil.

If the switching time is short, the noise emission increases at relatively low engine speeds. According to the invention, this is prevented by choosing a longer switching time for the solenoid valve when the rotational speed is low. This is obtained by turning on the return switch 165 by the electronic control unit 100 when the rotation speed is low. In that case, no back electromotive force is generated. At this time, the current collapses due to the ohmic loss of the de-energizing circuit, which causes the current fall time to increase several times compared to fast de-energizing.

The device of the present invention comprises a fast deenergizing diode 150.
Since the high-speed de-energizing means consisting of and the freewheeling circuit consisting of the freewheeling switch 165 and the freewheeling diode 160 are provided, the freewheeling circuit is activated (activated) when the rotation speed is low,
When the engine speed is high, high-speed de-energization can be activated to improve noise characteristics and achieve fuel metering with great accuracy. In the case of mid-range rpms, preferably the deenergization by reflux is first activated. This is ended by opening the reflux switch 165 after a predetermined time, and thereafter, the influence of high-speed deenergization becomes large. The time during which the deenergization by the return flow is active is selected so that it gradually decreases as the rotation speed increases. From the given speed, the return circuit is no longer active,
Only fast deenergization takes place.

The various possibilities are shown in FIG. Figure 2
(A) shows the current I and the stroke H (stroke) of the solenoid valve needle when the rotation speed is small. At time T1, the switching means 110 is activated and the solenoid valve is separated from the power supply voltage. The reflux switch is closed.
The current flowing through the solenoid valve 120 drops to zero according to an exponential function. At time T2, the current drops to the value zero and the solenoid valve transitions to the second state. The interval between time points T1 and T2 is relatively long.

FIG. 2 (b) shows the current and the stroke of the solenoid valve needle when the engine speed is in the middle range. At time T1, the switching means 110 is activated and the solenoid valve is separated from the power supply voltage. The reflux switch is closed. The current flowing through the solenoid valve 120 drops to zero according to an exponential function.

At time T2, the reflux switch opens. From this point, the influence of the fast deenergizing diode 150 becomes strong. This means that the current I drops very quickly to zero. After a short time, at time T3, the valve needle reaches a new position. The period between time points T1 and T3 is shorter than in the case of FIG.

FIG. 2 (c) shows the current and the stroke of the solenoid valve needle when the rotational speed is high. At time T1, the switching means 110 is activated and the solenoid valve is separated from the power supply voltage. The reflux switch opens. In this case, the influence of the fast deenergizing diode 150 becomes strong. This means that the current I drops to zero very quickly. After a short time, the valve needle reaches a new position at time T4. The period between time T1 and time T4 is shown in FIG.
Even shorter than in the case of (b).

FIGS. 3, 4 and 5 show flow charts of different embodiments of the method of the present invention. A simple implementation is shown in FIG. In step 300, the switching means 110 is driven to open. Thereby, the driving of the solenoid valve is finished. In step 305, the rotation speed N is detected. In decision step 310 it is checked whether the rotational speed is greater than the threshold value NS. If so, the reflux switch 165 is driven to open. As a result, the return circuit is deactivated. In this case, only high speed deactivation is performed at high revolutions. As a result, a very short switching time of the solenoid valve is obtained.

When it is determined in decision step 310 that the number of revolutions N is smaller than the threshold value NS, in step 320 the return switch 165 is driven to be closed. In that case, the return circuit becomes active and the switching time of the solenoid valve is extended accordingly. In this way, the noise generation caused by the short switching time of the solenoid valve at low rotational speeds is significantly reduced.

Since only two different switching times can be selected using this configuration, the rotation speed threshold value N
Optimal driving characteristics cannot be obtained in the S range. This drawback is eliminated using the method shown in FIG.

In step 300, the switching means 110 is driven to open. As a result, the driving of the solenoid valve ends. In step 305, the rotation speed is detected. Then, in step 330, the optimum switching time TF is read out from the map according to at least the rotational speed or is calculated using the function F at least based on the rotational speed. Optimal switching time TF
Other operating parameters, for example load or temperature values, can also be taken into account in order to determine

In step 335, the reflux switch 16
5 is driven to close. Judgment step 340
Checks whether the optimum switching time TF has already passed. If not, the reflux switch remains closed. If the time has elapsed, then in step 345 the reflux switch is driven to open. This means that from this point on, fast deactivation becomes active and the current quickly returns to zero.

Another embodiment is shown in FIG. This is a mixed version of the embodiment shown in FIGS. Step 30
At 0, the first switching means 110 is driven to open, and then at step 305, the rotation speed N
Is detected. The decision step 350 checks whether the rotational speed is lower than the first rotational speed threshold NS1. If so, in step 352 the return switch 165 is closed.

If the number of revolutions is greater than the first threshold NS1, it is checked in a second decision step 355 whether the number of revolutions is greater than the second threshold NS2. If so, in step 363 the return switch 165 is opened. If the speed is between the two thresholds, the optimum switching time TF is determined based on at least the speed, as shown in step 365 of FIG. 4, and the return switch is closed in step 370. . Decision step 375 checks if the switching time TF has already elapsed. After the switching time TF has elapsed, the return switch 165 is opened again in step 363.

According to the device of the present invention, the drive speed can be selected according to the rotational speed in the diesel injection pump controlled by the solenoid valve. Particularly at low rotational speeds, a long switching time of the solenoid valve and at high rotational speeds a short switching time is obtained, which makes it possible to reduce noise emissions.

[0029]

As is apparent from the above description, according to the present invention, it is possible to prevent as much as possible the noise emission generated in the method and apparatus for controlling the electromagnetic load, particularly the electromagnetic valve of the injection device.

[Brief description of drawings]

FIG. 1 is a block diagram schematically illustrating a configuration of the present invention.

FIG. 2 is a diagram showing a time characteristic of a current flowing through a solenoid valve and a stroke of a solenoid valve needle.

FIG. 3 is a flowchart of the operation of the first embodiment of the present invention.

FIG. 4 is a flow chart illustrating another embodiment of the present invention.

FIG. 5 is a flow chart illustrating another embodiment of the present invention.

[Explanation of symbols]

 100 Electronic Control Unit 110 First Switching Unit 120 Electromagnetic Valve 130 Resistance 150 High Speed Deactivating Diode 160 Freewheeling Diode 165 Freewheeling Switch

Claims (8)

[Claims] 1. A method of driving an electromagnetic load (120), in particular an electromagnetic valve of an injector of an internal combustion engine, wherein a switching time of the electromagnetic load (120) is a driving parameter when driving to determine an injection start and / or an injection end. A method of driving an electromagnetic load, which is configurable according to. 2. Method according to claim 1, characterized in that the switching time can be set according to the rotational speed. 3. The method according to claim 2, wherein a small switching time is set when the rotation speed is high, and a large switching time is set when the rotation speed is low. 4. An electromagnetic load (120), in particular, a device for driving an electromagnetic valve of an injection device of an internal combustion engine, wherein the switching time of the electromagnetic load (120) is set as an operating parameter when driving to determine injection start and / or injection end. An apparatus for driving an electromagnetic load, characterized in that it is provided with means for setting according to the above. 5. A control device (100) drives a first switching means (110) for turning on and off a current flowing through an electromagnetic load (120) and a second switching means (165) for activating a return circuit. The device according to claim 4, characterized in that: 6. Device according to claim 5, characterized in that the switching time is adjustable by the second switching means (165). 7. Device according to claim 5, characterized in that the second switching means (165) are closed when the rotational speed is low and open when the rotational speed is high. 8. At a rotational speed in the middle range, the second switching means (165) is first closed and the second switching means (165) is opened after a predetermined period. 5. The device according to 5 or 6.