JPH02223863A - Method and apparatus for measuring current to be pulsated of induction load - Google Patents

Abstract

PURPOSE: To dispense with measuring by a large common-mode rejection ratio by a method wherein a series circuit of an inertia activating value and a resister is connected to a load in parallel and an instant voltage of the resister during the inertia activating is detected when a pulsed current which is allowed to flow in an inductive load grounded to a vehicle is measured. CONSTITUTION: A pulsed current is energized via a switching element 3 to an inductive load 4 of a vehicle grounded by a terminal 9a. The measuring and controlling of the current at that time is carried out as follows. A time point of measuring the current is synchronized with pulsing of the switching element 3 and an instant value of a terminal voltage of a resister 7 during the inertia activating is detected preferably at an intermediate point during the activating instead of detecting the current during the energizing of the current. At this point, the load current during the applying is in proportion to the instant voltage of the resister 7. As a result, the detected value is digitally converted by an A/D converter 14 to be compared with a target value stored in a microprocessor 16, then a ratio of mark to a space on the load 4 is varied to control the load current.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a method for connecting one end of an inductive load to an on-vehicle source as close as possible to ground potential. Then, a device for energizing the load and detecting the current is connected to the space 0 +1 between the poles of the vehicle's armpits, and the energizing conductor connects the load to P&lFF to detect the operating current passing through the load. TECHNICAL FIELD The present invention relates to a method for measuring the pulsed tIjL current of an inductive load in a motor vehicle, in which a measuring resistor applied thereto forms a measuring voltage characterizing the pulsed operating current, and a device for implementing this method.

[Conventional technology]

A step motor that pulses supply 1, a Kamehiro switch,
Self-actuated actuators, such as solenoid valves, are increasingly being used in automobiles. I for fast flow adjustment! ! In principle-based proportional valves, the pulsed supply U generates less heat in the control device. The advantage of pulsed flow regulation in on-off valves is that the size of the on-off valves is reduced.

An on-off valve that operates at the on-board vehicle pressure without pulsing,
Operating temperature range (approximately -40°C to at least +85°C)
Fluctuations in in-vehicle market pressure (9v to 1v in cars)
6V) must be constructed so that they open and close reliably and do not overload. Only two parameters, pressure and operating deviation, cause a variation of 2.3 times the operating current. With pulsed on-off valves, the cost increase due to structural measures to accommodate such parameter variations is completely eliminated.

Technical journal 1, Sub-device dated November 13, 1987, article 1 "Lossless energization of operator" and applicant's application No. P38
In No. 177770, inductive load pulse? [In order to control or regulate the current to an advantageous value, it has been proposed to exploit the voltage drop proportional to the current at the load by means of an inertia circuit which limits the re-emf voltage using a valve element.

In such a device, it is not suitable to return the current through the vehicle earth at the location of the load (measuring resistance in the earth force flow path), so two conductors without potential are connected from the white cap U to the valve. This is disadvantageous because two control lines leading to the valve have to be routed and are connected to the whitening device, and these control lines have to be electronically protected against vehicle disturbance voltages.

Another known device, in which the measuring resistor is moved from earth, allows the return current path to be obtained by connecting the load to the vehicle earth in the field, thereby requiring only one energizing conductor to the load; In any case, the measured voltage of the measuring resistor must be taken out as a differential voltage by two conductors insulated from the vehicle ground and then measured with a large common-mode rejection ratio. Components suitable for this are expensive. However, when using an A-D microcontroller for signal processing, as is common in modern control systems, measurements with large common mode rejection ratios pose significant difficulties.

[Problem to be solved by the invention]

Therefore, it is an object of the present invention to energize an inductive load, which is normally connected to the vehicle ground, through a single conductor at an installation location in a vehicle, and to
It is an object of the present invention to provide a method and a device that allow the magnitude of the voltage with respect to one pole of an operating angle of 5 voltage to be evaluated as a measure of turtle current without expensive in-phase component rejection means.

[Means for resolving issues]

In order to solve this problem, the method according to the invention provides that the measuring voltage that is built up across the measuring resistor is reduced in each time interval to the inert energization only during the pulse period or only during the blockage of the inert energizing valve or during the "pulse relief". Detect and evaluate while the valve is conducting. This again.

In an apparatus for carrying out the method, the measuring device includes an inertial energization valve connected in series with the measuring resistor and a digital microcomputer, the inertial energization valve being able to conduct during pulse breaks in the operating current of the load, and the output of the microcomputer The other end is connected to the control input terminal of a switching element that applies a dynamic fv-voltage to an inductive load.

〔Effect of the invention〕

The advantage of the method according to the invention is that it is only necessary to install one biasing conductor for each small load, which reduces the number of terminals that have to be provided on the measuring resistance device.

Furthermore, the device according to the invention makes it possible to use a microcomputer, for example a microprocessor or a microcontroller, for the measurement of the monitored current.

[Conventional example]

Before explaining the embodiments of the apparatus implementing the present invention,
A conventional example will be explained with reference to FIGS. 18 to 1c.

According to FIG. 1a, an on-vehicle power supply pressure UBATT is supplied to the electronic control device 1 via a conductor 2.

The vehicle s s m voltage is applied to a controlled switch 3 through which an eleventh current can be supplied to a stack 4 depending on the pulsed energization. For this purpose, the load 4 is connected via two conductors 5 and 6 to the control device yIi1. The second conductor 6 is connected in the control device al to a Q11 constant resistor 7, which measuring resistor 7 is connected to ground 9 and opens a current circuit. A semiconductor valve 10 as an inertia valve is connected in parallel to the series circuit consisting of the load 4 and the measuring resistor 7 and is blocked when the load 4 is supplied.

With respect to the measuring resistor 7 and earth 9, a measuring voltage UM can be taken out, which measuring voltage is equal to the current through the load 4 (wJ output th
, current). FIG. 1c shows the time course of the measured pressure UM or current during pulsed operation of the electronic switch 3. Due to the smoothing effect of the inductance of the load 4, when pulsed at a sufficiently high frequency, in conjunction with the semiconductor valve 10, a sawtooth-like pressure curve is produced in a known manner. In this case, the supply to load 4 -1 conductor 1!5
and 6 must be insulated from ground 9 and the on-board power supply voltage of conductor 2. Therefore, the two lead-out wires in the electronic control unit 1 must also be protected against electrical connection or vehicle disturbance voltages. This is in-vehicle m#
This also applies to the case where the switch 3 for the voltage +UBATT is replaced by the switch 3 for the ground 9, ie, when the circuit according to section 1a 1 is constructed symmetrically.

FIG. 1b shows the known device D in which the order of the load 4 and measuring resistor 7 in the current circuit is reversed.

Here, the load 4 is connected to the ground 9a, and the control device fits
is connected to ground 9b at a different location. For this reason, it is sealed! It is only necessary to lay one conductor 5 between the load 4 and the load 4, and it is sufficient to electronically protect the two conductor pull-outs for each load 4 directly from the electronic control unit against incorrect connections or vehicle disturbance voltages. do it. However, the advantage of a return current path via vehicle ground is accompanied by the disadvantage that current measurements can only be made by measuring the floating differential voltage UM with respect to ground 9b. In principle, this differential voltage follows the same course 12 as in FIG. 1C.

However, when the opener 3 is closed, the measuring leads 11a and Ilb
has a position close to the on-vehicle static removal position + UBATT, and when switch 3 opens, Cff1l conduction period), these measurement leads have a potential close to earth 9, so it is difficult to evaluate the difference and pressure. Therefore, the differential voltage UN must be measured with a large common-mode rejection ratio.

A simplification of the external wiring of the control device 1i[1 is thus only possible by requiring expensive evaluation elements in the control device 1, such as laser-controlled hybrid circuits, which represent a device with considerable equipment cost.

〔Example〕

Now, in the method according to the present invention, ↑lr during the energization period,
, the direct continuous measurement of the current is replaced by a short-term wl, current detection, and for this purpose the time of current establishment is synchronized with the pulsing of the switch 3, and the voltage representing the current strength is injected into the control 1@1. The load 4 is always connected to the same terminal in the control device 1 or taken out from the constant resistor 7 which can be connected to the ground potential 9a at the moment of current measurement in the control device l. ing. Instead of detecting the current during the pulse period, the 4TB flow measurement can be made as indirectly as possible during the inert sump 1 period. Therefore, during the inertia period, the voltage characterizing the current is detected directly or indirectly, the result is stored, and the mark-to-space ratio of the power supply of the load 4 is readjusted every cycle, so that the current is adjusted as a whole. can be done.

2 and 3 show a device implementing the method for indirectly measuring the current during current pulse pauses, and FIG. 5 shows a device for directly measuring the current during the current pulse.

The first embodiment shown in FIG. 2 includes a slave switch 3, which is capable of applying the on-vehicle 14 gap pressure UBATT in pulse form from the on-vehicle main gland 2 to the load 4. .

Terminals 5 and 6 of load 4 are connected to switch 3 and external ground terminal 9
connected to a.

In the control device I, a series circuit consisting of a measuring resistor 7 and a semiconductor valve 10 is connected in parallel to an inductive load 4, and the measuring resistor 7 is connected to the same unit potential as the load 4 via a connection 8 with a local earth terminal 9b. The semiconductor valve 10 is in a blocked state while the supply iJ5 is connected to the load 4 through the switch 3. Measuring resistance 7
The tap 13 between the and the semiconductor valve IO is connected to the analog input terminal of an analog-to-digital converter 14, and the output side 1 of this analog-to-digital converter j514 is connected to the microcomputer 16 via the data bus 15. There is. The output end of the microcomputer 16 is the active channel 1
7 to the control input terminal of the switch 3.

This device operates as follows. A rectangular current is applied to each measuring resistor 7 at the free flow m, J9] 11M+, which results in a voltage drop UM with a time course according to FIG. Thus analog-digital converter 1
A pulsating DC voltage whose top edge drops exponentially is applied to the input terminal of 4.

Preferably in the middle of the inertia period, the % i, 11 m pressure value at the measuring resistor 7 is read by the analog-to-digital converter 14 , converted into a digital value, and transmitted to the microcomputer 16 . The microcomputer diagram compares the measured value with the stored target value,
If necessary, change the mark-to-space ratio. This corresponds to the principle of a simple two-point regulator. In this embodiment, measurement is performed in the voltage range where analog-digital conversion +a14 is convex. Based on the linear approximation, the detection of current during the middle of the inertia conduction period is possible even at relatively low frequencies. A sufficiently linear relationship is maintained between the actual energizing current during JA and the tracing result during the inert energization period. Mainly loss 1 due to especially pulsed operation
For on-off valves that aim to limit one force, there are relatively few requirements for accuracy in current establishment.

In the second embodiment according to FIG. 3, the electronic switch 3 makes it possible to apply the on-board power supply voltage UBATT in pulses from the on-board power supply bus 2 to the load 4. Terminals 5 and 6 of load 4
is connected to the switch 3 and the ground terminal 9a. In the whitening device @1, a series circuit consisting of a measuring resistor 7 and a semiconductor valve 10 is connected in parallel to an inductive load 4, and the measuring resistor 7 is connected to the same standard as the load 4 via a connection 8 with a local earth terminal 9b. The semiconductor valve 10 is in a blocked state while power is being supplied to the load 4 through the switch 3. Measuring resistor 7 and semiconductor valve 1
The tap 13 of h with 0 is connected to a first input of a comparator 18, the other input of the comparator being connected to the reference point -UREF.

The output of the comparator is connected to the trigger input h'r of a timing pulse generator 20, which is connected to the microcomputer 16. A connecting portion 17 communicates from the output end of the microcomputer 16 to the control input end of the switch 3.

The differences in operation from the embodiment shown in Figure 2 are as follows.

Here the current measurement is based on a time measurement. Comparator 18
, the timing pulse generator 20 and the microcomputer 16 cause the measuring resistor 7 to be
It is checked whether the voltage across corresponds to a predetermined setpoint value -UREF. If the comparator 18 does not switch at exactly the right time, there will be a current deviation from the predetermined target value and the microcomputer 16 can change the mark-to-space ratio accordingly.

In this case as well, in addition to current measurement, the current can be adjusted to a fixed value or to an arbitrary predetermined value by appropriate activation of the microcomputer 16.

FIG. 5 shows an apparatus for making current measurements at time intervals during a current pulse. Here, the electronic switch 3 is connected via a connection 8 to a ground 9a in the area of the installation at the location.The switch 3 consists of a load 4 and a semiconductor valve 10. A measuring resistor 7 connected in series to the parallel circuit is connected to the ground 9a in synchronization with the output of the microcomputer 16, and thus the terminal 10 BA is connected to the ground 9a.
A power source (not shown) connected between the TT and the ground point 9a enables pulsed power supply to the load 4 from a pressure source. In contrast to the previous embodiment, here the voltage drop UM is conducted in two conductors to a differential amplifier 18', which is connected to the earth point 9C inside the device and which carries out an analog-to-digital conversion i+4 on the output side. This analog-to-digital converter 14 is connected to a microcomputer 16.

Since the contact resistance of the electronic switch 3 may vary significantly, a differential amplifier is provided.

If the measurement is carried out only during the current pulse, i.e. a relatively small voltage occurs at both terminals of the measuring resistor 7 with respect to the earth point 9C, high requirements are placed on the common-mode rejection ratio in the differential amplifier 18'. Not done. Open/close i! ? I3
When opened, the load 4 has voltage-conducting terminals 5' and 6'. Other operations are similar to those described in the previous figure. That is, the measuring resistor 7 is exposed to the standard pressure UM only during the flow pulse period.

[Brief explanation of the drawing]

Figure 1a is a km diagram of a conventional pulsed inductive load energizer that obtains a current signal related to ground, and Figure 1b is a km diagram of a conventional pulsed inductive load energizer that obtains a current signal that is not related to ground. Figure 11 and Figure 1c of the power supply device are similar to Figures 1 and 2.
a diagram showing a signal curve representing the current curve obtained by the diagram;
2 and 3 are connection diagrams of different embodiments of the device for carrying out the method according to the invention, and FIG. 4 is a signal il representative of the current f & pressure curve obtained from FIGS. 2 and 3. Figure 5 shows the current pulse rate during the current pulse period.
FIG. 6 is a micro-reading diagram of a third embodiment in which the settings are made; 3... Switching element (electronic switch) 4... Inductive load, 7... Measurement resistance, 10... Inertial product 1 valve, 16...
...Microcomputer, 10BATT...Operating voltage. Patent applicant Daimler-Benz Akchengesellschaft

Claims (1)

[Claims] 1. One end of the inductive load is connected to an on-vehicle power supply potential, a device for energizing the load and detecting the load current is connected between both poles of the on-vehicle power supply, and is connected to the load by an energizing conductor. In a measuring method in which a measuring resistor to which an operating current is applied through the load forms a measuring voltage characterizing the pulsed operating current, the measuring voltage formed across the measuring resistor (7) is During the blocking of the inertial energizing valve (10) only during the pulse period or during the blocking of the inertial energizing valve (10) only during the pulse period
10) is characterized by detecting and evaluating during conduction,
A method for measuring the pulsed current of an inductive load in an automobile. 2. Method according to claim 1, characterized in that the measured voltage is detected and evaluated approximately in the middle of the energization time interval synchronously with the pulsing of the operating current. 3. Characterized by detecting and evaluating the measured voltage approximately in the middle of the power supply time interval in synchronization with the pulsing of the operating current,
The method according to claim 1. 4. A claim characterized in that the measured voltage is converted into a digital data word, the data word is processed into a signal for pulsing the operating current, and the signal is transmitted as a control signal to the switching element (3) that pulses the current. The method described in Section 1. 5. Claim characterized in that the measured voltage is converted into a time interval, the time interval is processed into a signal for pulsing the operating current, and the signal is transmitted as a control signal to the switching element (3) that pulses the current. The method described in 1. 6. Method according to claim 4 or 5, characterized in that the mark-to-space ratio of the operating current of the load is set or adjusted as a function of the difference between the measured voltage and at least one stored target value. 7 A measuring device is connected in series with a measuring resistor (7), an inertial energizing valve (10) and a digital microcomputer (16).
), the inertial energizing valve (10) is capable of conducting during a pulse pause of the operating current of the load (4), and the output side of the microcomputer applies an operating voltage (+U_B_A_T_T) to the inductive load (4). 3. Device for carrying out the method according to claim 1, characterized in that it is connected to the control input of (3). 8. The measuring device comprises a comparator (18) with a reference voltage source, and a timing pulse generator (20) is connected to the output of this comparator to generate the time interval, and the difference between the measured voltage and the reference voltage is 8. Device according to claim 7, characterized in that at least one pulse with a related duration can be supplied from a timing pulse generator to the input of the digital microcomputer (16). 9 An analog-digital converter (14) is connected to the input side of the digital microcomputer (16),
8. Device according to claim 7, characterized in that the voltage drop (U_M) of the measuring resistor (7) can be supplied to its input. 10 The load (4) is connected to the inertia energizing valve (10) and the measuring resistor (7
10. The device according to claim 9, characterized in that the measuring resistor (7) is energized during pulse breaks in the operating current of the load (4). 11. Device according to claim 9, characterized in that the load (4) is connected in parallel with the free-flow energization valve (10), and the energization of the measuring resistor (7) takes place during pulses of the operating current of the load. 12 The measuring device is an analog-digital converter (14)
It includes a differential amplifier (18') connected to the input side of the differential amplifier, and the voltage drop (
Claim 9, characterized in that U_M) can be supplied.
The device described in.