JPH02176576A - Abnormality detector for load of intermittent current supply - Google Patents

Abstract

PURPOSE:To reduce a detection delay from the time when a current abnormality is occurred until the time it is detected by automatically renewing the threshold for a discrimination of the load current amount so as to follow up the objective value of the current in the manner of providing the load, current detection means, switching means and current supply control means. CONSTITUTION:The load is worked in accordance with the supplied current. The current flowing into the load is detected by the current detection means 180. The current flowing into the load is switched by a driver 200 which is the switching means. By microcomputers 110, 120 which are the current supply control means, the objective current renewable as occasion demands is formed and the driver 200 which is the switching means is controlled in accordance with the objective current and also the current value detected by the current detection means 180 is compared with the threshold level having the difference or the ratio settled for the objective current in advance, then an existence of abnormality is discriminated in accordance with those large/small relations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to abnormality detection of a load such as a solenoid that is energized substantially intermittently by a device such as a pulse duty control circuit. It can be used in the control circuit of a proportional control valve that adjusts the hydraulic pressure applied to the absorber.

[Conventional technology] For example, when using a proportional control valve to adjust oil pressure.

A pressure proportional to the current flowing through the solenoid of the proportional control valve can be generated. Therefore, in this type of pressure control, the value of the current flowing through the proportional control valve is adjusted. Pulse duty control is generally used to control such current. In other words, the voltage applied to the load is kept constant, the energization is controlled repeatedly at a constant cycle, and the duty between the energization period and the non-energization period is adjusted in each cycle of one energization control period, so that the average current to be energized can be calculated. Change the value.

Therefore, in this case, the current flowing to the load becomes substantially intermittent.

By the way, in various electrical control devices, the presence or absence of an abnormality such as a short circuit or disconnection of the load is identified, and 5'! It is important to take safety measures such as stopping power supply to the load when a problem is detected.

Load abnormality detection has conventionally been performed using the following method. In other words, the current flowing through the load is detected as a voltage by a resistor connected in series with the load, and the voltage is compared with a predetermined fixed threshold, and the presence or absence of a short circuit or disconnection is identified from the magnitude relationship. do.

[Problems to be Solved by the Invention] When detecting an abnormality in a load that is intermittently controlled to be energized by pulse duty control, etc., in order to detect the average value of the current flowing through the load, it is necessary to An integration circuit with a time constant is used to average the level of the pulsating current signal, and the level of the averaged signal is compared with a fixed threshold. Therefore, even if an abnormality occurs in the load and the current changes suddenly, if there is a large difference between the integral output at that time and the threshold level, by the time the integral output reaches the threshold level, It takes a long time depending on the integration time constant, and there is a delay in abnormality detection (see Figure 6).

This type of detection delay causes major secondary failures such as destruction of the control transistor due to excessive current and burnout of the electric cable (wire harness) connecting the control device and the load.

Here are some ways to reduce this type of detection delay.

It may be possible to reduce the time constant of integration and to reduce the difference between the threshold level and the level after integration at the time of occurrence of the abnormality.6 However, in the former method, if the time constant is made smaller, detection will occur. Since the average current pulsates, there is a disadvantage that the detection error increases. Also, in the latter method,
Since the difference (margin) between the normal fluctuation range of the average current due to duty control and the fixed threshold value becomes small, it becomes easy to falsely detect the current as abnormal even when it is normal.

An object of the present invention is to reduce the detection delay in abnormality detection of a load that is substantially intermittently energized by pulse duty control or the like.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides: a load that operates according to the 11ffi current; a current detection means for detecting the current flowing through the load; a switching means for switching the current; and generating a target current value that is updated at any time, controlling the switching means according to the target current, and applying the current value detected by the current detection means to the eye St current. An energization control means is provided which compares with a threshold level having a predetermined difference or ratio and identifies the presence or absence of an abnormality according to the magnitude relationship thereof.

[Function] With the above means, the difference between the normal current value and the threshold level becomes smaller, so the detection delay becomes smaller than before.

That is, the threshold level is based on the target current set by the current supply control means at each point in time, and is determined by a certain difference (Ix
), the threshold level automatically follows normal current changes, so even if the difference (Ix) between the target current and the threshold level is small,
There is no risk of erroneously detecting a normal current change as an abnormal current. During normal operation, a current that matches the target current set by the current supply control means flows through the load, so the current value detected by the current detection means substantially matches the target current.

However, if a short circuit or disconnection occurs in the load, the current flowing through the load changes to a value that is significantly different from the target current, so if the difference exceeds Ix, an abnormality in energization is detected. Ix
If is set to a relatively small value, even if the time constant when integrating the pulsating waveform is relatively large, the detection delay time from when a current abnormality actually occurs until it is detected becomes short.

Other objects and features of the present invention will become clear from the following description of an embodiment with reference to one drawing.

[Example] Fig. 2 shows the configuration of a hydraulic path of a -type automobile suspension control device. The configuration of this hydraulic circuit will be explained with reference to FIG. 1 is a hydraulic pump driven by the engine, 2 is a relief valve that restricts the pressure at the output end of the hydraulic pump 1 from rising above a predetermined level, and 3 is a check valve.

4 is an oil cooler, and 5 is a reservoir. Hydraulic pump 1
A hydraulic line 9 is connected to the output end of the hydraulic line 9 via a check valve 3.
are connected to the hydraulic line 9, and four sets of hydraulic control units 10, 20, 30, and 40, accumulators 6 and 7, and a bypass valve 8 are connected.

The four hydraulic control units 10, 20, 30 and 40 are
respectively, the left front axle of the vehicle (denoted FL).

A shock absorber (FL) supports the right front axle (designated FR), the left rear wheel (RL
15) Control the internal hydraulic pressure. By adjusting the hydraulic pressure of the shock absorber, its length (i.e. vehicle height)
and the spring constant can be changed.

Since the four hydraulic control units 10, 20, 30, and 40 have substantially the same configuration, only the FL hydraulic control unit 10 will be specifically described below. The hydraulic control unit 10 includes a filter 11. Linear control valve 1
2. Cut valve 13, relief valve 14. and a shock absorber 15. The linear control valve 12 applies a pressure proportional to the value of the current applied to the solenoid 12a to a hydraulic line 16 connected to its output.
Output to. The cut valve 13 mechanically detects when the pressure in the hydraulic line 17 falls below a predetermined value and automatically closes the valve. The relief valve 14 opens when a high pressure equal to or higher than a predetermined value is applied from the absorber 15 side, and releases the pressure to the drain.

Therefore, by changing the value of the current applied to the solenoid of the linear control valve 12, the shock absorber 15
The hydraulic pressure applied to the shock absorber 15 changes, the length of the shock absorber 15 changes, and the vehicle height changes.

Note that the bypass valve 8 connected to the hydraulic line 9 is
This is a solenoid valve that is normally closed, but is opened when there is an urgent need to reduce pressure or when restarting the engine when it stalls.

FIG. 3 shows the configuration of an electrical component that controls the hydraulic circuit shown in FIG. 2. Referring to FIG. 3, this circuit is implemented by control unit E
It consists of a CU, various switches, various sensors, various solenoids, etc. connected to its numerous input terminals and output terminals.

First, the sensors will be explained. 51.52° 53 and 54 are FL, FR, and RL, respectively.

and a vehicle height sensor placed near the shock absorber of the RR, each of which outputs a voltage (analog signal) according to the distance between the wheel at each position and the vehicle body, that is, the vehicle height at each position. 55, 56.57 and 58 are respectively FL,
This is a pressure sensor placed inside each of the FR, RL, and RR shock absorbers, and outputs a voltage (analog signal) corresponding to each oil pressure. Moreover, 59 and 60 are pressure sensors arranged in the hydraulic line 9 and the drain, respectively, and output a voltage (analog signal) according to the pressure at each position. 61 and 62 are G sensors that output a voltage (analog signal) according to acceleration (G), 61 detects G in the longitudinal direction of the vehicle body, and 62 detects G in the lateral direction of the vehicle body, respectively.

A steering sensor 74 outputs a pulse signal according to the amount of rotation of the steering wheel, and outputs two-phase signals whose phases are shifted from each other.

75 is one output terminal of a regulator that stabilizes the output voltage of the generator, and outputs a binary signal indicating whether or not the engine is rotating. 76 is a throttle sensor that outputs a 3-bit binary signal depending on the opening degree of the throttle valve. A reed switch 73 detects the rotation of a permanent magnet connected to the speedometer cable, and outputs a pulse whose period changes depending on the vehicle speed.

Also, 71, 72, 77, 78, 79 and 80 are the main relay, ignition switch, stop lamp switch, and door switch, respectively.

These are a reservoir level warning switch and a vehicle height adjustment switch. 12a, 22a, 32a and 42a are
These are linear control valve solenoids provided in the FL, FR, RL, and RR hydraulic control units, respectively, and 8a
is the solenoid of the bypass valve 8.

FIG. 4 shows a specific configuration of the control unit ECU shown in FIG. 3. Referring to FIG. 4, the control unit EC1J includes two CPUs (microcomputers) 110,
120. I10 expansion unit 130, reset control unit 140. A/D conversion unit 150. Active filter unit 160, duty control unit 170
．． Current detection unit 180. Drivers 190, 200.
Power supply 210, backup power supply 220. driver 230
and an input buffer 240.

Input terminals IG, SPD, SS of this control unit ECU
The signals applied to input ports PAO and SS2 of CPU110 are respectively applied to input ports PAO and A
Applied to SRO, ASRI and ASR2. Furthermore, AS
RO to ASR2 are interrupt request boats. Also, an input terminal ICL.

Ll, L2. L3. STP, DOOR, LOIL and H
The information of the signal applied to the I
- Applied to PA7.

Vehicle height sensors 51-54. Analog signals output by the pressure sensors 55 to 60 and the G sensors 61 and 62 are applied to each analog signal input terminal of the A/D conversion unit 150 via the active filter unit 160. Further, analog signals corresponding to the current flowing through each of the solenoids 12a, 22a, 32a, 42a, and 8a are generated by the current detection unit 180 and applied to each analog signal input terminal of the A/D conversion unit 150. CPU
120 can convert the level of the signal applied to each analog signal input terminal into a digital signal and read it by controlling the A/D conversion unit 150.

Information between the CPU 120 and the A/D conversion unit 150 is transmitted through the serial output port SO and the serial input port S.
transmitted through i.

Solenoids 12a, 22a, 32a for each solenoid valve.

42a and 8. The value of the current flowing through the sensor is adjusted by pulse duty control (pwM). The pulse that controls the on/off of energization of each solenoid.

Generated by duty control unit 170. C
When the PU 120 writes a predetermined instruction code and data for determining a duty value into the duty control unit 170, the duty control unit 170 outputs duty pulses corresponding to the data to each output terminal. The driver 200 controls energization/off of each solenoid according to the H/L level of each pulse signal output by the duty control unit.

By the way, it is necessary to detect the current that actually flows through the solenoid of each solenoid valve in order to perform feedback control so that the current value that should be energized matches the actual current value. The current signal is also used to detect abnormalities such as short circuits and disconnections in each solenoid.

In this type of abnormality detection, it is important to quickly detect an abnormality when it occurs and take measures such as, for example, stopping power supply. for example.

If the solenoid is short-circuited and continues to be energized for a long time, the transistor of the driver unit 200 may be destroyed, the electric cable may be burned out due to heat generation due to excessive current, and especially in the case of a suspension device, part of the shock absorber may be damaged. However, the height becomes abnormal and the vehicle body tilts.

In this embodiment, since the solenoid is energized by pulse duty control, the energization is substantially intermittent. For this reason, an integrating circuit is provided inside the current detection unit 180, and a signal obtained by averaging the intermittent current waveform with a predetermined time constant is obtained as an output. However, in this case, it is unavoidable that the level change of the detected signal is delayed relative to the actual change in current. Therefore, in order to identify the presence or absence of an abnormality in the current, if the current signal is compared with the upper and lower limit levels fixed in advance as shown in Figure 6, the level of the averaged signal will change after an abnormality appears in the actual current. reaching an upper or lower level; Since it takes time behind the scenes, there is a delay in abnormality detection. Therefore, in order to reduce this delay, in this embodiment, a threshold value (upper limit value) is set.

We have devised a way to set the lower limit value). This will be specifically explained next.

FIG. 1 shows in detail the energization control portion for one solenoid among the operations of the control unit ECU.

This will be explained with reference to FIG. In suspension control, for example, when an instruction to change the vehicle height is detected, it is necessary to change the oil pressure of the shock absorber. In that case, in order to change the current value of the solenoid of the linear control valve, the target value Is of the current is adjusted.

If there is a change in Is, step 3 then step 4
In step 5, the duty value of the pulse duty control corresponding to the new Is is calculated, and in the next step 5, the new duty value is written into the duty control unit 170.

As a result, the duty of the pulses output by the duty control unit 170 changes, and the average value of the current flowing through the solenoid of the linear control valve changes, so the pressure at the output end of the valve changes, and the oil pressure of the shock absorber is adjusted. .

On the other hand, the current detection unit 180, as shown in FIG.
The averaged signal is output to the A/D conversion unit 150. This averaged current signal If is the first
In step 6 of the figure, the CPU 120 performs sampling via the A/D conversion unit 150.

In step 7, the difference ΔI between the target current value Is and the sampled current value If is determined, and the subsequent step 9
and 10, identify the value of the difference ΔI. That is, ΔI is -
If it is between Ix and +Ix, that is, IfJ'Is+I
If it is between x-Is-Ix, the process proceeds to step 11, and the duty value is corrected by performing a PID (proportional, integral, differential) calculation on the difference Δ■.

If the difference ΔT<-Ix, the process proceeds to step 12, where it is determined that the solenoid is short-circuited, and abnormality processing is executed at the next step 14. If ΔI>Ix, it is determined that the solenoid is disconnected at step 13. In the next step 14, abnormality processing is executed.

That is, in this embodiment, as shown in FIG.
The upper limit level of f is set to Is+Ix, and the lower limit level is set to 15-Ix. That is, the threshold level is automatically changed according to the target value Is. Therefore, in this case, Ix is Ix when there is no short circuit or disconnection in the solenoid.
The value may be the sum of the deviation that may occur between s and If, plus a slight margin, and the detected current If and threshold value l5fl
The difference with x becomes sufficiently small.

Therefore, for example, when a solenoid is short-circuited, the current that actually flows through the solenoid increases rapidly, and the detected current If
also gradually increases according to a predetermined time constant. Under normal conditions, the target value Is and the detected value If are very close values, but if a short circuit or disconnection of the solenoid occurs, they will no longer match. Therefore, when the detected value If exceeds the upper limit value Is+1x, a solenoid short circuit is detected. In this case, since Ix is very small, the detection delay from when an abnormality appears in If until it exceeds the upper limit or lower limit is very small.

In the above embodiment, when detecting an abnormality in the solenoid current, the latest target value Is is compared with the detected value If.
It may be changed to use a value obtained by averaging s.

[Effects] As described above, according to the present invention, the threshold value (upper limit value and lower limit value) for identifying the magnitude of load current.

Since the current is automatically updated to follow the target value, the difference between the normal load current and the threshold is small, so the detection period from when an abnormality occurs until the load current exceeds the threshold is small. time becomes shorter 6

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a part of the operation of the control unit ECU of FIG. 3. FIG. FIG. 2 is a hydraulic circuit diagram showing a hydraulic system of a sunpension device embodying the present invention. FIG. 3 is a block diagram showing an electrical equipment section that controls the hydraulic system shown in FIG. 2. FIG. FIG. 4 is a block diagram showing the configuration of the control unit ECU of FIG. 3. FIG. 5 and FIG. 6 are waveform diagrams showing the timing of abnormality detection in the embodiment and the conventional example, respectively. FIG. 7 is an electrical circuit diagram showing a part of the current detection unit 180 of FIG. 4. 1: Hydraulic pump 2: Cleave valve 3: Check valve 5: Reservoir 8; Bypass valve to, 20, 30, 40: Hydraulic control unit 12: Linear control valve 8a, 12a, 22a, 32a, 42a: Solenoid (load) 13 : Cut valve 14: Relief valve 15: Shock absorber 51-54: Vehicle height sensor 55-60: Pressure sensor 61.62: G sensor 74 Ni steering sensor 76: Throttle sensor 1i0.120: Microcomputer (energization control means) 180 :Current detection unit (current detection means) 200:
Driver (switching means) ECU: Control unit Applicant: Aisin Seiki Co., Ltd. and one other person

Claims (2)

[Claims] (1) A load that operates according to the energized current; a current detection means that detects the current flowing through the load; a switching means that switches the current flowing through the load; and a target current value that is updated from time to time. The switching means is controlled according to the target current, and the current value detected by the current detection means is compared with a threshold level having a predetermined difference or ratio with respect to the target current, and the magnitude relationship thereof is determined. An abnormality detection device for an intermittent energized load, comprising: energization control means for identifying the presence or absence of an abnormality depending on the situation. (2) The current detection means includes a resistor connected in series with the load, and an averaging means for inputting the voltage between the terminals of the resistor and averaging the signal level, and the energization control means 2. The abnormality detection device for an intermittent energized load according to claim 1, wherein the signal level averaged by the averaging means is sampled as a current value.