JP3697272B2 - Method and apparatus for driving an electromagnetic load - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method and apparatus for driving an electromagnetic load, and more particularly, to a method and apparatus for driving an electromagnetic load having a movable member, particularly an electromagnetic valve of an injection device of an internal combustion engine.
[0002]
[Prior art]
A method and apparatus for driving an electromagnetic load is known from DE-OS 3426799 (US-A 4,653,447). In the apparatus described in the publication, the switching time of the solenoid valve and the switch-on and switch-off times based on the switching time are detected. The exact switching time of the solenoid valve is determined based on the time waveform of the current flowing through the solenoid valve.
[0003]
This type of solenoid valve is preferably used to control fuel injection in gasoline and / or diesel engines. In order to accurately measure even the minimum injection amount, the switching point at which the armature of the supplied solenoid valve reaches one of its end positions is particularly important.
[0004]
In a known system, a current waveform is examined within a time window in which a normal switching time occurs, and the switching time is obtained based on this time waveform.
[0005]
[Problems to be solved by the invention]
It is an object of the present invention to provide a method and apparatus for driving an electromagnetic load that can determine the switching time with an inexpensive configuration.
[0006]
[Means for Solving the Problems]
In order to solve this problem, the present invention (Claim 1)
A method for drive the electromagnetic load having a movable member,
Calculated et been by switching the time the movable member reaches the end position detects bending points of the time waveform of variable corresponding to the current flowing through the electromagnetic load,
A reflux circuit for supplying current to the electromagnetic load is provided ,
The switching time point adopts a configuration that is obtained during a reflux period in which current flows in the reflux circuit ,
In the present invention (Claim 6),
An apparatus for driving an electromagnetic load having a movable member,
Means for obtaining a switching time point when the movable member reaches the terminal position by detecting a bending point of a variable time waveform corresponding to a current flowing through the electromagnetic load;
A reflux circuit for passing current to an electromagnetic load;
Means for determining the switching time during a reflux period in which current is flowing in the reflux circuit;
A configuration in which is provided is also adopted.
[0007]
[Action]
In such a configuration, a time window in which a switching time point is predicted to occur is set. This time window is set according to the operating parameters. The reflux circuit is activated by opening the switching means connected in series with the load within the time window thus set. The switching time is obtained by detecting a change in the gradient of the current waveform.
[0008]
By determining the switching time during the reflux period, a device for adjusting the voltage between time windows is not required. At the same time, the power loss is significantly reduced compared to devices with a voltage regulator.
[0009]
【Example】
Hereinafter, the present invention will be described in detail using embodiments shown in the drawings.
[0010]
This embodiment relates to an apparatus for switching an electromagnetic load. This device can in principle be used in connection with the respective electromagnetic load and is therefore not limited to a specific use case. However, in particular, the device according to the invention is used effectively in connection with an internal combustion engine, in particular when supplying fuel to the combustion chamber of the internal combustion engine. For this purpose, a solenoid valve for controlling the amount of fuel supplied to the internal combustion engine is used in a particularly preferred manner.
[0011]
In that case, particularly when the load is small, it is necessary to measure and supply the minimum amount of fuel as accurately as possible. For this purpose, it is necessary to accurately know when the armature of the solenoid valve to be fed reaches one terminal position. This point is usually called the beginning of injection period (BIP). This time is obtained by examining the temporal transition waveform of the solenoid valve current. Preferably, the time waveform of the current when the voltage is made constant or the time waveform of the voltage when the current is made constant is examined, and the bending point in the waveform or the differential quotient of the observed variable (parameter) is detected. It is detected whether there are any significant changes possible.
[0012]
FIG. 1 schematically shows a main configuration of a device for controlling a fuel metering device controlled by an electromagnetic valve. The electromagnetic load 100 is connected to the power supply device (Ubat) via the switching means 110. The switching means 110 is driven by the driving device 120. The driving device 120 is also connected to a current regulating or voltage regulating device 130.
[0013]
The other terminal of the electromagnetic load is connected to the ground via the sensor 145. The sensor 145 is connected to the detection circuit 140, and this detection circuit is connected to the voltage adjustment or current adjustment device 130. A freewheeling device 150 is connected in parallel to the series circuit of the electromagnetic load and the sensor 145. In the simplest embodiment, the reflux device 150 is formed from a correspondingly connected reflux diode (freewheel diode).
[0014]
The order of each element in the series circuit composed of the switching means 110, the load 100, and the sensor 145 can be selected to be different. Importantly, the sensor 145 is electrically connected directly to the load even when the switching means 110 is open, and the current flowing or applied voltage can be measured by the sensor 145 during the return period. It is arranged.
[0015]
The operation of this apparatus will be described below with reference to FIG. In FIG. 2, the stroke H of the solenoid valve needle is indicated by a one-dot chain line, the voltage UM dropping between the solenoid valves is indicated by a solid line, and the current IM flowing through the solenoid valve is indicated by a broken line. The waveforms of these signals are illustrated over time in FIG.
[0016]
FIG. 2 (a) shows the state of the device in which voltage adjustment is performed. This illustration is merely an example. The temporal waveform depends significantly on the type of solenoid valve used and the applied voltage.
[0017]
Initially, the solenoid valve armature is in its first end position X1. The current IM takes the value 0, and the voltage UM dropping between the solenoid valves also takes the first value U1. The driving device 120 closes the switching means 110 at a predetermined time T1. As a result, the voltage takes a second value U2. This value is in the region of the battery voltage Ubat. At the same time, the current IM rises with time. The armature of the solenoid valve does not react at first.
[0018]
This state is continued until the current flowing through the solenoid valve reaches a predetermined threshold value. This threshold is in the region of about 10A. When this threshold is reached, the current regulator 130 generates a corresponding signal that is supplied to the driver 120. The driving device 120 drives the switching means 110 to open the switching means. As a result, the current flowing through the solenoid valve drops. The current adjusting device 130 compares the current value detected by the sensor 145 with a set target value, and generates a signal to be supplied to the driving device 120 according to the comparison result.
[0019]
The driving device 120 adjusts the current or voltage to the target value by opening and closing the switching means 110. This target value is about 10 A in this embodiment. From the time when the threshold is reached and the current regulation is activated, the armature moves in the direction of its second end position X2.
[0020]
A time window defined by the lower limit value T2 and the upper limit value T3 is set. It is expected that the switching time TBIP will occur within this time window.
[0021]
It is particularly effective if the limit values T2 and T3 of the time window are read from the map in accordance with, for example, operating parameters such as speed, fuel quantity to be injected or other variables (parameters).
[0022]
Normally, at time T2, the current adjustment is shifted to the voltage adjustment. This means that the voltage regulator 130 adjusts the voltage dropping between the solenoid valves to a settable voltage value (a magnitude of about 4 to 9 volts). The current no longer varies bi-directionally between the two thresholds, and in this example it falls slowly. In that case, the armature continues to move in the direction of the new end position X2. The current need not necessarily decrease slowly. According to each embodiment, the current always has a distinguishable waveform on both sides of the instant tBIP.
[0023]
While the armature is moving, a voltage is induced in the coil of the electromagnetic load. At the switching time TBIP, the armature reaches its new end position and finishes moving. Thereby, the induced voltage disappears. As a result, the current IM flowing through the coil has other gradients. A change in the current waveform is detected by the detection circuit 140. After the time window has expired at time T3, the control 110 selectively opens, or the switch 110 opens if T3 is equal to T4. At time T4, the switch 110 is opened, and the driving of the solenoid valve is finished.
[0024]
A transistor is preferably used as the switch. In this type of drive, the power loss stress of the switch 110 during voltage regulation is very high. In order to increase the general efficiency of the injector and reduce the thermal stress of the switch 110, it is desirable to reduce this power loss.
[0025]
According to the invention, this is done as follows. While switch 110 is open, reflux device 150 is active. This means that when switch 110 is open, current flows to the load via diode 150 and sensor 145. Under ideal conditions, that is, when the voltage dropped between the ohmic resistance of the electromagnetic load 100 and the diode 150 is zero and the armature does not move, this current continues to flow unchanged. Under actual conditions, i.e. when the load ohmic resistance is not zero and the voltage drops about 1 volt at the diode, the current waveform has a negative slope that moves and is accurate. It is further reduced under the influence of the induced negative voltage.
[0026]
When the load armature reaches its new end position X2, the induced voltage disappears. As a result, the current slowly decreases or increases in some cases. This change in the slope of the current waveform is used to detect the switching time TBIP.
[0027]
The corresponding situation is described in FIG. The signal waveforms up to and from time T2 correspond to the signal waveforms shown in FIG. According to the present invention, as shown in FIG. 2B, the switch 110 is opened at time T2. Thereby, the current IM flowing through the electromagnetic valve decreases with time. When the armature reaches its new end position X2, the current drops with a slight slope. A change in the first derivative of the bending point or current waveform is detected by the detection device 140.
[0028]
The method according to the present invention will be described with reference to the flowchart of FIG. In a first step 300, during the first stage of driving between time points T1 and T2, a time window defined by the time points T2 and T3 when the normal switching time point occurs is set according to various operating parameters.
[0029]
Next, at step 310, the time counter is incremented. While the time counter has not yet exceeded the lower limit value T2 of the time window, current adjustment is performed. If it is determined in decision step 230 that the time counter has reached the lower limit T2 of the time window, the switch 110 is driven and opened in step 330. Subsequently, in step 340, the detection device 140 is activated so that the switching time TBIP can be detected. In step 350, the detection device 140 determines the switching time.
[0030]
This means that the switching time point is obtained within a time window in which the voltage dropping between the loads is substantially constant.
[0031]
If it is determined at decision step 360 that the time counter has exceeded the second threshold of time window T3, then at step 370, normal current regulation is again entered. If the time counter has not yet exceeded the second threshold, the time counter is incremented at step 380 and decision step 360 is reached.
[0032]
In an embodiment of the invention, it is also possible to shift to current regulation again as soon as the switching time is detected.
[0033]
Therefore, according to the present invention, the current adjustment is stopped and the switch 110 is opened during the time window during which the switching instant TBIP is expected to occur. The switching time is detected by examining the current waveform during this period. The detection of the switching time is well known.
[0034]
【The invention's effect】
The configuration in which the switching time is detected when the return circuit is active provides an advantage that voltage adjustment is not particularly necessary. Thereby, the construction cost can be significantly reduced. The power loss stress of the switch 110 during the time window is significantly reduced. The resulting characteristic current waveform allows reliable and stable processing, i.e. the detection of the switching time, even if the engine types are different and thus the electrical or mechanical parameters are significantly different. Under actual conditions, the current level decreases during the time window, so that the energy stored in the magnetic circuit when the solenoid valve is shut off is small, so that the moving direction of the armature can be reversed rapidly. This is more effective than the conventional case especially considering the short injection period.
[0035]
As is clear from the above description, according to the present invention, it becomes possible to detect the switching time with an inexpensive configuration.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing a configuration of a device of the present invention.
FIG. 2 is a signal waveform diagram showing waveforms of various signals with respect to time.
FIG. 3 is a flowchart illustrating the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Electromagnetic load 110 Switching means 120 Drive apparatus 130 Current regulator (voltage regulator)
140 detection circuit 145 sensor 150 reflux device

Claims (6)

A method for drive the electromagnetic load having a movable member,
Calculated et been by switching the time the movable member reaches the end position detects bending points of the time waveform of variable corresponding to the current flowing through the electromagnetic load,
A reflux circuit for supplying current to the electromagnetic load is provided ,
Wherein said switching time drives the electromagnetic load, characterized in that it is determined during the reflux period in which current flows in the reflux circuit. The method of claim 1, wherein a time window in which the switching time is predicted to occur is set. The method according to claim 2, wherein the time window is set according to operating parameters. 4. A method according to claim 1, wherein the return circuit is activated within the time window by opening a switching means connected in series with the electromagnetic load. The method according to claim 1, wherein the switching time is detected based on a change in a slope of a current waveform. An apparatus for driving an electromagnetic load having a movable member ,
Means for obtaining a switching time point when the movable member reaches the terminal position by detecting a bending point of a variable time waveform corresponding to a current flowing through the electromagnetic load ;
A reflux circuit for passing current to an electromagnetic load ;
Means for determining the switching time during a reflux period in which current is flowing in the reflux circuit ;
An apparatus for driving an electromagnetic load, wherein:

Images