JP2022112453A - Electromagnetic induction load control device - Google Patents

Abstract

To diagnose a failure of a power cutoff switch circuit without affecting the operation of loads even when many electromagnetic induction loads are being controlled in an electromagnetic induction load control unit having a power cutoff switch circuit that cuts off the flow current of an electromagnetic induction load on the positive side of a DC power supply.SOLUTION: An electromagnetic induction load control device 10 according to the present invention includes a power cutoff switch circuit 21 that cuts off an energizing current to a plurality of electromagnetic induction loads 141, 142, ..., and 14n, and load drive control of a plurality of electromagnetic induction loads is performed by load drive signals 291, 292, ..., and 29n synchronized with each other within a preset PWM control period T, and the failure diagnosis of the power cutoff switch circuit 21 is performed during a non-energization period ΔTs during which all the output duties of the plurality of electromagnetic induction loads are turned off within the PWM control period.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electromagnetic induction load control device.

In recent years, electronic control systems have come to play a more important role in control systems for automobiles, construction machinery, and industrial machinery.

In the electronic control unit, if a failure occurs inside or outside the unit, in order to reliably detect the failure and minimize the impact on the operation of the machine, the electromagnetic induction load that controls the hydraulic pump, etc. is energized. Implementing a blocking function is required. Furthermore, in order to secure the reliability of the function itself, it is required to perform failure diagnosis of the circuit that plays the role of interruption.

Japanese Patent No. 6445699 Japanese Patent No. 4509914

In the above patent document, when a failure is diagnosed by causing the power supply cutoff circuit to perform a temporary cutoff operation while the electronic control unit is in operation, the drop in the power supply voltage from the standard value is determined by the discharge time constant of the capacitor. obey. Therefore, in order to keep the connected load within the operable voltage range, the shutdown operation period of the power supply shutdown circuit is controlled in consideration of the capacitor capacity to reduce the impact on the operation of the load and prevent failure of the power supply shutdown circuit. Techniques are described that allow the diagnosis to be made.

When the above method is used in construction machinery, there are a large number of electromagnetic induction loads that control hydraulic pumps, signal control valves, control valves, etc. Therefore, if the failure diagnosis of the power supply cutoff circuit is performed while the loads are energized, the electric charge of the capacitor will increase. Discharge occurs immediately, making fault diagnosis difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and can perform a failure diagnosis of a load power cut-off function without considering the charge capacity of a capacitor even during control of a large number of electromagnetic induction loads. The purpose is to provide technology.

The electromagnetic induction load control device of the present invention for solving the above problems is
An electromagnetic induction load control device having a power supply cutoff switch circuit that cuts off current to a plurality of electromagnetic induction loads,
Load drive control of the plurality of electromagnetic induction loads is performed by mutually synchronized PWM signals within a preset PWM control period, and all output duties of the plurality of electromagnetic induction loads are turned off within the PWM control period. The fault diagnosis of the power cut-off switch circuit is performed during the non-energization period from 1 to 10 to the start of the next PWM control cycle.

According to the present invention, even when a large number of electromagnetic induction loads are being controlled, it is possible to cut off the power cutoff switch circuit without affecting the operation of the loads, and perform fault diagnosis. Further features related to the present invention will become apparent from the description of the specification and the accompanying drawings. Further, problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a figure which shows a hydraulic excavator control part typically. 4 is a circuit configuration diagram of an electromagnetic induction load control unit; FIG. FIG. 4 is a timing chart for explaining the process of generating a temporary shutdown flag in the first embodiment of the present invention; FIG. FIG. 4 is a timing chart for explaining the process of generating a temporary shutdown flag in the first embodiment of the present invention; FIG. FIG. 4 is a flow chart illustrating a process of generating a temporary shutdown flag in the first embodiment of the present invention; FIG. FIG. 4 is a timing chart for explaining the failure diagnosis operation of the power cutoff switch circuit in the first embodiment of the present invention; FIG. FIG. 4 is a timing chart for explaining the failure diagnosis operation of the power cutoff switch circuit in the first embodiment of the present invention; FIG. FIG. 9 is a timing chart for explaining the failure diagnosis operation of the power cutoff switch circuit in the second embodiment of the present invention; FIG.

In carrying out the present invention, a hydraulic system as shown in FIG. 1 is targeted. The hydraulic system shown in FIG. 1 is mounted, for example, on construction machines such as power shovels and dump trucks. The prime mover 3 gives rotational driving force to the pump unit 4, and the pump unit 4 supplies pressure oil to the control valve 5 and the signal control valve 6, respectively.

Since the control valve 5 drives a plurality of actuators including the hydraulic cylinder 1 and the hydraulic motor 2, the hydraulic paths are switched by a spool (not shown). The operation of the control valve 5 is mainly controlled by pressure oil supplied from the signal control valve 6 and having a pressure lower than that of the actuator drive circuit.

The pump unit 4, the control valve 5, and the signal control valve 6 are controlled partially or wholly by an electromagnetic induction load 14 mounted thereon. All electromagnetic inductive loads operate with current supplied from an electromagnetic inductive load control unit (electromagnetic inductive load control device) 10 . The electromagnetic induction load control unit 10 processes input signals from various external devices including the operation device 15 and controls the load current supplied to the electromagnetic induction load.

[First embodiment]
FIG. 2 is a configuration diagram of an electromagnetic induction load control unit. The electromagnetic induction load control unit 10 includes a central processing unit 20, a power cutoff switch circuit 21, a voltage detection circuit 23, a backflow prevention circuit 27, a smoothing capacitor 28, and load drive circuits 251, 252, . . . , 25n.

The power cutoff switch circuit 21 is connected to the drive power supply +VB (battery), and the backflow prevention circuit 27 is connected to the latter stage. A smoothing capacitor 28 is connected after the backflow prevention circuit 27, and load drive circuits 251, 252, . . . , 25n are connected in parallel with each other.

The power cutoff switch circuit 21 is controlled by the switch drive signal (22) to supply or cut off the power supply voltage to the load drive circuits 251, 252, . do. Also, the power cutoff switch circuit 21 shuts off all the electromagnetic induction loads 141, 142, . , 14n. By interrupting the energization current of all the electromagnetic induction loads in the event of an abnormality, the operation of the hydraulic equipment is stopped and unintended behavior of the hydraulic system caused by the abnormality is minimized.

The backflow prevention circuit 27 synchronizes with the operation of the power cutoff switch circuit 21 in the previous stage, and supplies power supply voltage to the load drive circuits 251, 252, . On the other hand, in the cut-off state, it has the role of blocking the current flowing back from the smoothing capacitor 28 in the subsequent stage to the power cut-off switch circuit 21 in the preceding stage. Furthermore, the backflow prevention circuit 27 also has the role of protecting the internal circuit when the drive power source +VB (battery) of the electromagnetic induction load control unit 10 is accidentally reversely connected.

A voltage detection circuit (voltage detection unit) 23 is connected to each of the upstream side and the downstream side of the power cutoff switch circuit 21, detects the upstream voltage and the downstream voltage of the power cutoff switch circuit 21, and outputs the detection result to the central processing unit 20. Output for When the power cutoff switch circuit 21 is conducting, the front-stage monitoring voltage (24a) and the rear-stage monitoring voltage (24b) of the power cutoff switch circuit 21 are equivalent. When the power cutoff switch circuit 21 is cut off, the front-stage monitor voltage (24a) and the rear-stage monitor voltage (24b) of the power cutoff switch circuit 21 have different values.

The central processing unit 20 includes an abnormality determination unit 35 , a conduction command generation unit 33 , a temporary disconnection flag generation unit 34 , a load driving signal generation unit 31 and a load output monitoring unit 32 .
The load drive signal generator 31 generates load drive signals 291, 292, . . . , 29n for the load drive circuits 251, 252, .

The conduction command generator 33 outputs a command to turn on the power cutoff switch circuit 21 during normal operation, and outputs a cutoff command when an abnormality is detected inside or outside the electromagnetic induction load control unit to turn on the power cutoff switch circuit. 21 is blocked. Furthermore, according to the temporary shutdown flag signal (341) output from the temporary shutdown flag generator 34, shutdown control for failure diagnosis of the power shutdown switch circuit 21 is executed.

The temporary cutoff flag generator 34 outputs a temporary cutoff flag signal (341) to the conduction command generator 33 based on the output state signal (32m) from the load output monitor 32. FIG.

The load output monitoring unit 32 monitors the load outputs 301, 302, . Output to the flag generator 34 . 2, load outputs 301, 302, . . . , 30n are input as signals to be monitored. good too.

The abnormality determination unit 35 determines whether or not the power cutoff switch circuit 21 is operating normally based on the detected voltage output from the voltage detection unit 23, and determines whether an abnormality of the power cutoff switch circuit 21 is detected. , 29n output from the load drive signal generator 31 is issued.

The load drive circuits 251, 252, . . . , 25n are circuits for controlling drive voltages for driving the electromagnetic induction loads 141, 142, . The load drive circuits 251, 252, . . . , 25n include freewheeling diodes 261, 262, . The central processing unit 20 determines the output duty of the load drive signals 291, 292, . , 25n are operated to output currents to the electromagnetic induction loads 141, 142, . . . , 14n. A return current flows through the return diode only during the non-operation period after the load drive circuits 251, 252, .

3 and 4 are timing charts for explaining the process of generating the temporary shutdown flag (341), and FIG. 5 is a flow chart. As described above, the load drive signals 291, 292, .

The temporary shutoff flag generator 34 executes the process shown in the flowchart of FIG. In addition, the temporary shutdown flag generator 34 has a counter function, and records the number n of times the processing shown in the flowchart of FIG.

In order to reliably perform the failure diagnosis of the power cutoff switch circuit 21, it is necessary to ensure a cutoff time of at least a certain length, and this time is defined as the cutoff time ΔTsmin for diagnosis.

The load output monitoring unit 32 outputs an output state signal (32m), which is the logical sum of the load outputs 301, 302, . The load output monitoring unit 32 refers to the OR of all the load outputs 301, 302, . . . , 30n (S140). The output state signal (32m) transitions to OFF when the output duty of all the electromagnetic induction loads is turned OFF and the state becomes non-energized.

The temporary shutdown flag generator 34 calculates the length ΔTs of the non-energization period, which is the shutdown possible time from when the output state signal (32m) turns off (Yes in S150) until the next PWM control cycle starts. (S160). Then, if the length ΔTs of the non-energization period is greater than the length ΔTsmin of the cutoff time (Yes in S170), the power cutoff switch drive signal 22 is turned off for a certain period of time within the non-energization period ΔTs of the PWM control cycle. (S190).

The length ΔTs of the non-energization period can be calculated based on the PWM control period T and the longest ON time in each output duty of the plurality of electromagnetic induction loads. Specifically, the length ΔTs of the non-energization period is calculated by the difference between the counter value n at the time when it is detected that the output state signal (32m) is turned off and the counter maximum value N of the PWM control cycle T. and multiplying the difference by the temporary cutoff flag determination interval Δt.

When the temporary shutdown flag determination process is executed at the point of time (A) in FIG. 3, regarding the branch in the flowchart of FIG. As a result, the temporary shutdown flag is turned off (S180), and the process ends.

When the temporary shutdown flag determination process is executed at the point of time (B) in FIG. 3, for the branch in the flowchart of FIG. , S160 calculates the cut-off possible time ΔTs, and S170 follows Yes. As a result, the temporary cut-off flag is turned on (S190), and the process ends.

When the temporary shutdown flag determination process is executed at the point of time (C) in FIG. 3, the branch in the flowchart of FIG. Processing ends.

When the temporary shutoff flag determination process is executed at the point of time (D) in FIG. 3, the PWM control period T has ended and the counter value has reached N, so following Yes in S110 results in the temporary shutoff flag is turned off (S180) and the process ends. Note that the counter value is reset at S120 in FIG. 5 at the start of the next PWM control period.

Further, the point of time (E) in the timing chart shown in FIG. 4 will be described. Here, as compared with FIG. 3, the duty of the load output (302), which is the maximum duty, is longer in the horizontal axis direction than in FIG. At the time of (E), although S110 in FIG. 5 follows No, S130 Yes, and S150 Yes, S170 follows No, and as a result, the temporary shutdown flag is turned off (S180), and the process ends. In the same processing thereafter, the temporary cutoff flag is not turned on until the next PWM control cycle.

Next, the behavior of the conduction command generator 33 with respect to the temporary cutoff flag (341) will be described. Here, the length ΔTsmin of the cutoff time of the energized current by the power cutoff switch circuit 21 necessary for failure diagnosis of the power cutoff switch circuit 21 is compared with the length ΔTs of the non-energization period, and the length of the non-energization period is compared with the cutoff time. If it is longer, a process of executing fault diagnosis is performed.

FIG. 6 is a timing chart for explaining the process in which the electromagnetic induction load control unit 10 diagnoses the power cutoff switch circuit 21 for failure. From time t10 to t20 and from time t20 to t30, one cycle of the load drive signals 291, 292, . . . 29n is shown. Times t10 to t11 and t20 to t21 are the longest periods during which the load drive signals 291, 292, . will behave the same. Times t11 to t20 and t21 to t30 are periods in which all the load drive signals 291, 292, . . . , 29n are turned off, and the load outputs 301, 302, .

As described above, the temporary shutdown flag generator 34 raises the temporary shutdown flag (341) when it determines that the actual non-energization period ΔTs is longer than the shutdown time ΔTsmin required for fault diagnosis. Upon detecting the rise of the temporary cutoff flag (341), the conduction command generator 33 operates the power cutoff switch drive signal (22) to make it fall only for a predetermined period of time ΔTsmin.

If the power cutoff switch circuit 21 is operating normally, power to the load drive circuits 251, 252, . During the cut-off period, the post-monitoring voltage (24b) drops and a voltage difference occurs between it and the preceding-stage monitoring voltage (24a) (ΔV in the figure). The abnormality determination unit 35 determines whether the power cutoff switch circuit 21 is operating normally by comparing the voltage difference ΔV detected during the cutoff operation with a preset voltage difference threshold value ΔVth. For example, when ΔV is equal to or greater than a predetermined threshold value ΔVth (ΔV≧ΔVth), it is determined that the power cutoff switch circuit 21 is normal.

On the other hand, if an abnormality occurs in the power cutoff switch circuit 21 and the post-stage monitoring voltage (24b) does not drop sufficiently during the temporary cutoff, the voltage difference ΔV from the preceding-stage monitoring voltage becomes small (FIG. 7). When ΔV is detected to be smaller than a predetermined threshold value ΔVth (ΔV<ΔVth), the abnormality determination unit 35 determines that the power cutoff switch circuit 21 has caused an insulation failure (short circuit). When the abnormality determination section 35 detects a failure of the power cutoff switch circuit 21, the drive signal generation section 31 turns off the load drive signals 291, 292, . . . 29n. The threshold value ΔVth is set in advance according to the configuration and purpose of the system.

The electromagnetic induction load control unit 10 according to the first embodiment performs the cutoff operation of the power cutoff switch circuit 21 while the load outputs 301, 302, . do. Therefore, it is possible to diagnose the failure of the power cutoff switch circuit 21 without being affected by the capacity of the smoothing capacitor 28 and with less influence on the operation of the electromagnetic induction load.

The electromagnetic induction load control unit 10 according to the first embodiment synchronizes output drive signals for all the electromagnetic induction loads and performs PWM control at a predetermined frequency. Then, if the period ΔTs during which all the loads generated within the PWM control period are not energized can be secured for the shutdown time ΔTsmin or more required for failure diagnosis of the power shutdown switch circuit 21, the power shutdown switch circuit 21 is shut off, and the power supply is turned off. The power cutoff switch circuit 21 is diagnosed based on the voltage at the point in series with the cutoff switch circuit 21 .

According to the electromagnetic induction load control unit 10 according to the first embodiment, even when a large number of electromagnetic induction loads are being controlled, failure diagnosis of the power cutoff switch circuit can be performed without affecting the operation of the loads. can be done. When it is diagnosed that the power cutoff switch circuit 21 is out of order, the load drive signal generator 31 can stop outputting drive signals to the load drive circuits 251, 252, . . . , 25n. The operator of the construction machine can be alerted by displaying or alarming that the power cutoff switch circuit 21 has failed.

[Second embodiment]
The electromagnetic induction load control unit according to the second embodiment has an output duty ON time set in advance for a plurality of electromagnetic induction loads, and cuts off the conducting current by the power cutoff switch circuit necessary for failure diagnosis of the power cutoff switch circuit. The PWM control cycle is a time obtained by adding the time and , and the fault diagnosis is performed after the ON time of the output duty has passed within the PWM control cycle.

The target hydraulic system and the configuration of the electromagnetic induction load control unit are the same as those shown in FIGS. The difference from the first embodiment is that the duty of the load drive signals 291, 292, . This is to uniquely define a period of time during which the power cutoff switch circuit 21 is stopped, and perform a failure diagnosis of the power cutoff switch circuit 21 .

FIG. 8 is a timing chart for explaining the failure diagnosis operation of the power cutoff switch circuit 21 of the second embodiment. In the figure, t40 to t50 and t50 to t60 indicate one cycle of the load output. Time t40 to t41 and time t50 to t51 are assumed to be on-time ΔTsmax corresponding to a duty uniformly determined for all load outputs, and on-time exceeding this is prohibited for all load outputs. Also, the time width ΔTsmin obtained by subtracting ΔTsmax from the period T is the time required for failure diagnosis of the power cutoff switch circuit 21 .

The temporary shutdown flag generator 34 sets the shutdown flag (341) at time t41 when ΔTsmin can be secured. Upon detection of the cutoff flag (341), the conduction command generator 33 controls the power cutoff switch drive signal (22) and executes failure diagnosis of the power cutoff switch circuit 21. FIG.

In the second embodiment, the time ΔTsmin required for failure diagnosis is always ensured within the PWM control period, so the failure diagnosis of the power cutoff switch circuit 21 can be executed at the intended timing.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the invention described in the claims. Changes can be made. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with another configuration.

DESCRIPTION OF SYMBOLS 1... Hydraulic cylinder, 2... Hydraulic motor, 3... Prime mover, 4... Pump unit, 5... Control valve, 6... Signal control valve, 10... Electromagnetic induction load control Unit, 14... Electromagnetic induction load, 15... Operating device, 141, 142, 14n... Electromagnetic induction load, 20... Central processing unit, 21... Power cutoff switch circuit, (22). Switch drive signal 23 Voltage detection circuit (voltage detection unit) (24a) Pre-stage monitoring voltage (24b) Post-stage monitoring voltage 251, 252, 25n Load drive circuit , 261, 262, 26n... Free wheel diode, 27... Backflow prevention circuit, 28... Smoothing capacitor, 291, 292, 29n... Load drive signal, 301, 302, 30n... Load output, 31... load drive signal generator, 32... load output monitor, (32m)... output state signal, 33... conduction command generator, 4... temporary shutdown flag generator, 35.・・Abnormality determination unit

Claims (6)

An electromagnetic induction load control device having a power supply cutoff switch circuit that cuts off current to a plurality of electromagnetic induction loads,
Load drive control of the plurality of electromagnetic induction loads is performed by mutually synchronized PWM signals within a preset PWM control period, and all output duties of the plurality of electromagnetic induction loads are turned off within the PWM control period. An electromagnetic induction load control device, characterized in that the fault diagnosis of the power cutoff switch circuit is executed during a non-energized period from the start of the next PWM control cycle to the start of the next PWM control cycle. In the failure diagnosis, the current is cut off by the power cutoff switch circuit, the voltage difference between the upstream side and the downstream side of the power cutoff switch circuit is detected, and when the voltage difference is equal to or greater than a threshold, the power cutoff switch is detected. 2. The electromagnetic induction load control device according to claim 1, wherein when the circuit is normal and the voltage difference is less than a threshold value, it is determined that the power cutoff switch circuit is out of order. The length of the cutoff time of the energized current by the power cutoff switch circuit required for failure diagnosis of the power cutoff switch circuit is compared with the length of the non-energized period, and the non-energized period is longer than the cutoff time. 3. The electromagnetic induction load control device according to claim 2, wherein the fault diagnosis is executed when the fault is detected. 3. The electromagnetic induction load control device according to claim 2, wherein the non-energization period is calculated based on the PWM control period and the longest ON time in each output duty of the plurality of electromagnetic induction loads. . The PWM for the time obtained by adding the ON time of the output duty set in advance in the plurality of electromagnetic induction loads and the cutoff time of the energized current by the power cutoff switch circuit necessary for failure diagnosis of the power cutoff switch circuit. as a control cycle,
3. The electromagnetic induction load control device according to claim 2, wherein the fault diagnosis is executed after the ON time of the output duty has elapsed within the PWM control period. a load output monitoring unit that monitors all the PWM signals for the plurality of electromagnetic induction loads;
2. The apparatus according to claim 1, wherein a time point at which cutoff of current by said power cutoff switch circuit is to be started within said PWM control cycle is determined based on an output state signal output from said load output monitoring unit. Electromagnetic induction load controller.

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