JP2022006515A - On-vehicle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-vehicle control device capable of reliably detecting a ground disconnection with a simple structure.
An in-vehicle control device 100 includes a solenoid drive circuit 140 having a current detection resistor 142 for driving a solenoid 210 and detecting a current flowing through the solenoid 210, a CPU 130 for controlling the solenoid drive circuit 140, and a CPU 130. It includes a power supply circuit 120 that generates a power supply to be supplied, and a pull-up resistor 190 that pulls up the ground 181 of the vehicle-mounted control device 100 to the power supply voltage generated by the power supply circuit 120.
[Selection diagram] Fig. 1

Description

The present invention relates to an in-vehicle control device mounted on a vehicle.

As an example of an in-vehicle control device mounted on a vehicle, a device including a solenoid drive circuit for driving a solenoid that is a part of an in-vehicle electric load is known. In such an in-vehicle control device, there is a problem that the in-vehicle control device continues to operate without stopping even if the ground of the in-vehicle control device is disconnected for some reason due to the configuration of the solenoid drive circuit.

In order to solve such a problem, for example, it is considered to use the technique described in Patent Document 1 below. That is, a semiconductor element having a function of monitoring the ground current is used in the solenoid drive circuit, and the current flowing on the ground side of the semiconductor element is constantly monitored. When the ground is disconnected and the current flowing to the ground side disappears, it is determined that the ground is disconnected and the signal output is stopped.

Japanese Unexamined Patent Publication No. 3-166816

However, in the technique described in Patent Document 1, it is necessary to use a dedicated semiconductor element in which the function of detecting ground disconnection is integrated with the driver element for driving the solenoid, so that the choice of parts is very small. Therefore, a new problem arises in which a driver element having an optimum current rating for driving a solenoid cannot be selected. In addition, the use of a dedicated semiconductor element raises a new problem that the structure of the in-vehicle control device becomes complicated.

The present invention has been made to solve such a technical problem, and an object of the present invention is to provide an in-vehicle control device capable of reliably detecting a ground disconnection with a simple structure.

The vehicle-mounted control device according to the present invention has a solenoid drive circuit that drives a solenoid and has a current detection resistor for detecting a current flowing through the solenoid, a control unit that controls the solenoid drive circuit, and the control unit. It is characterized by including a power supply circuit that generates a power supply to be supplied, and a pull-up resistor that pulls up the ground of the vehicle-mounted control device to the power supply voltage generated by the power supply circuit.

Since the in-vehicle control device according to the present invention has a pull-up resistor that pulls up the ground of the in-vehicle control device to the power supply voltage generated by the power supply circuit, it is pulled up to the current detection resistor of the solenoid drive circuit when the ground is disconnected. It becomes possible to superimpose a current via a resistor. Therefore, the ground disconnection can be reliably detected based on the change in the current flowing through the current detection resistor before and after the ground disconnection. Moreover, the structure is simple because it can be realized simply by adding a pull-up resistor. As a result, it becomes possible to reliably detect the ground disconnection of the in-vehicle control device with a simple structure.

According to the present invention, it is possible to reliably detect a ground disconnection of an in-vehicle control device with a simple structure.

It is an internal block diagram of the vehicle-mounted control device which concerns on embodiment. It is an internal block diagram which shows the current flow at the time of a ground disconnection in the vehicle-mounted control device which concerns on embodiment. It is an internal block diagram for demonstrating the problem of the conventional in-vehicle control device.

Hereinafter, embodiments of the vehicle-mounted control device according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. Further, in the following embodiment, an example in which two solenoids and two solenoid drive circuits are provided will be described, but the present invention is also applied to one or three or more solenoids and solenoid drive circuits, respectively.

FIG. 1 is an internal configuration diagram of an in-vehicle control device according to an embodiment. As shown in FIG. 1, the in-vehicle control device 100 of the present embodiment is an ECU (Electronic Control Unit) mounted on a vehicle, and is a solenoid drive circuit for driving a plurality of solenoids (here, solenoids 210 and 220). It includes 140, 150, a CPU (Central Processing Unit) 130 that controls the solenoid drive circuits 140, 150, and a power supply circuit 120 that supplies power to the inside of the vehicle-mounted control device 100.

The power supply circuit 120 is connected to the positive electrode side of the battery 400 via the connector 110 and the ignition switch 300, which will be described later, and generates a power supply to the CPU 130 and the like.

The CPU 130 corresponds to the "control unit" described in the claims, and optimally controls the solenoid drive circuits 140 and 150 by performing calculations and determinations based on various input conditions. I do. For example, the CPU 130 controls the solenoid drive circuit 140 so that the calculated current value flows through the solenoid 210. Further, the CPU 130 has an AD conversion function, and an AD port 131 is provided inside the CPU 130.

The CPU 130 also controls the operation of the power supply circuit 120. For example, the CPU 130 controls the operation and stop of the power supply circuit 120. Further, the CPU 130 also controls the opening / closing operation of the ignition switch 300.

Since the solenoid drive circuit 140 and the solenoid drive circuit 150 have the same structure, only the solenoid drive circuit 140 will be described here. The solenoid drive circuit 140 amplifies and outputs the potential difference between the driver element 141 that drives the solenoid 210, the current detection resistor (that is, the shunt resistor) 142 that detects the current flowing through the solenoid 210, and the current detection resistor 142. It has an arithmetic amplifier 143 and a diode 144 that returns the current flowing through the solenoid 210.

The vehicle-mounted control device 100 includes connectors 110, 160, 170, and 180 for connecting to the outside of the vehicle-mounted control device 100. The connector 110 serves as a power supply terminal, and is connected to the positive electrode side of the battery 400 via an ignition switch 300 that turns on and off the power supply of the vehicle-mounted control device 100. The connector 180 serves as a ground terminal and is connected to the ground (GND) 181 of the vehicle-mounted control device 100. The connector 160 and the connector 170 each have a role of an output terminal. The connector 160 is connected to the solenoid 210, and the connector 170 is connected to the solenoid 220.

The solenoid 210 and the solenoid 220 are, for example, linear solenoids, respectively, and drive a hydraulic circuit (not shown). The solenoid 210 and the solenoid 220 are arranged in a transmission 200 having a conductive metal housing. The ground 230 of the solenoid 210, the ground 240 of the solenoid 220, the ground 181 of the vehicle-mounted control device 100, and the ground 410 of the battery 400 are connected to the metal housing of the transmission 200, respectively.

Here, in order to make the present invention easier to understand, a problem of the conventional in-vehicle control device, that is, even if the ground 181 is disconnected, the CPU 130 continues to operate without stopping will be described with reference to FIG.

As shown in FIG. 3, in the conventional in-vehicle control device 100A, when the ground 181 of the in-vehicle control device 100A is disconnected for some reason (hereinafter referred to as “when the ground 181 is disconnected”, the cross mark in FIG. 3 is used. The ground current of the power supply circuit 120 and the ground current of the CPU 130 flow along the ground current paths 301, 302, 303, 304, and 305, and further along the ground current path 306 via the connector 160. It flows into the metal housing of the transmission 200. Then, in the metal housing of the transmission 200, the ground current further reaches the negative electrode of the battery 400 along the ground current paths 307 and 308 via the ground 410 of the battery 400. That is, when the ground 181 is disconnected, the ground current paths 301, 302, 303, 304, 305, 306, 307, and 308 are formed.

As a result of the ground current path being formed in this way, even if the ground 181 of the in-vehicle control device 100 is disconnected, the CPU 130 is in a state of continuing to operate, so that there arises a problem that the CPU 130 does not stop. As a result, even though the ground 181 is disconnected, the ground disconnection cannot be detected.

In order to solve such a conventional problem, the vehicle-mounted control device 100 according to the present embodiment further includes a pull-up resistor 190 that pulls up the ground 181 to the power supply voltage generated by the power supply circuit 120. More specifically, as shown in FIG. 1, a pull-up resistor 190 is connected between the power supply voltage Vcc generated by the power supply circuit 120 and the connector 180 as a ground terminal.

In the vehicle-mounted control device 100 having the pull-up resistor 190 as described above, when the ground 181 is normally connected to the transmission 200 (hereinafter referred to as “normal time of the ground 181”), the power supply voltage generated by the power supply circuit 120 is generated. A current flows from the Vcc (eg 5V) to the ground 181 via the pull-up resistor 190 along the ground current paths 401, 402, 403 (see FIG. 1).

At this time, the solenoid drive circuit 140 is controlled so that the current value calculated by the CPU 130 is passed through the solenoid 210. Specifically, the current flowing from the driver element 141 is converted into a voltage by the current detection resistor 142, the signal is amplified by the operational amplifier 143, and is input to the AD port 131 of the CPU 130. Then, the CPU 130 compares the preset target current value with the current value input to the AD port 131, and the pulse width calculated so that the current value input to the AD port 131 matches the target current value. The solenoid drive circuit 140 is feedback-controlled by a modulation (PWM) signal.

That is, in the normal state of the ground 181 the ground current of the vehicle-mounted control device 100 flowing through the pull-up resistor 190 has no effect on the control of the solenoid drive circuit 140.

Hereinafter, in the in-vehicle control device 100 of the present embodiment, the situation when the ground 181 is disconnected for some reason (that is, when the ground 181 is disconnected) will be described with reference to FIG.

As shown in FIG. 2, when the ground 181 is disconnected (the cross mark in FIG. 2 indicates the disconnection point), the power supply voltage Vcc (for example, 5V) generated by the power supply circuit 120 is grounded via the pull-up resistor 190. Current flows like current paths 501, 502, 503, 504, 505.

At this time, the CPU 130 controls the solenoid drive circuit 140 in the same manner as when the ground 181 is normal, but even if feedback control is attempted to match the preset target current value, the ground current when the ground 181 is disconnected. Is superimposed on the current detection resistor 142, so that correct feedback control cannot be performed.

Specifically, the CPU 130 attempts to pass a current so as to control the solenoid drive circuit 140 with a PWM signal calculated so as to reach a target current value. However, since the ground current at the time of disconnection of the ground 181 is superimposed on the current detection resistor 142, a current larger than the target current value flows in the solenoid drive circuit 140. As a result, the CPU 130 recognizes that the current detected by the operational amplifier 143 of the solenoid drive circuit 140 is flowing more than the target current value, and feedback-controls the solenoid drive circuit 140 so that the current flows less.

Therefore, the CPU 130 defines the duty ratio of the PWM signal corresponding to the target current value (for example, 200 mA) of the solenoid drive circuit 140 as the normal value when the ground 181 is normal.

Further, the CPU 130 sets a predetermined value (for example, 20 mA) of the current flowing from the power supply voltage Vcc (for example, 5 V) generated by the power supply circuit 120 to the current detection resistor 142 via the pull-up resistor 190 when the ground 181 is disconnected. do.

Therefore, when the ground 181 is disconnected, even if the CPU 130 instructs the solenoid drive circuit 140 of the PWM signal corresponding to the target current value (that is, 200 mA), the current detection resistance 142 actually has the target current value. The sum of a certain 200 mA and the current 20 mA flowing when the ground 181 is disconnected, that is, a current of 200 mA + 20 mA = 220 mA flows. Since a current of 220 mA flows through the current detection resistor 142 in this way, the CPU 130 reduces the Dutu ratio of the PWM signal required to pass the target current value of 200 mA (for example, about 10% smaller), and the solenoid drive circuit 140. Controls the feedback to.

As a result, a difference occurs in the duty ratio for controlling the same target current between the normal time of the ground 181 and the disconnection of the ground 181. Then, the CPU 130 can grasp whether or not there is a difference in the duty ratios by comparing the duty ratios of the ground 181 at the time of normal operation and at the time of disconnection. Then, if there is a difference, the CPU 130 determines that the ground 181 is disconnected. By doing so, it is possible to reliably detect the ground disconnection.

Since the vehicle-mounted control device 100 having the above configuration includes a pull-up resistor 190 that pulls up the ground 181 of the vehicle-mounted control device 100 to the power supply voltage generated by the power supply circuit 120, the solenoid drive circuit is provided when the ground 181 is disconnected. A current passing through the pull-up resistor 190 is superimposed on the current detection resistor 142 of the 140, and the ground disconnection can be reliably detected based on the difference in the Dutu ratio of the PWM signal at the time of normal and disconnection of the ground 181. Moreover, since it can be realized only by adding a pull-up resistor 190 to the conventional in-vehicle control device 100, the structure is simple. As a result, it becomes possible to reliably detect a ground disconnection with a simple structure.

Further, since the ground 181 of the in-vehicle control device 100 is pulled up to the power supply voltage generated by the power supply circuit 120 via the pull-up resistor 190, the superimposed current is compared with the case where the ground 181 is pulled up to the voltage of the battery 400, for example. Since there is little variation, that is, the superimposed current is stable, it becomes easy to detect a ground disconnection.

In the present embodiment, it is preferable that the CPU 130 stops the solenoid drive circuit 140 when it is determined that the ground 181 is disconnected (in other words, when the ground disconnection is detected). Specifically, the CPU 130 stops the solenoid drive circuit 140 by transmitting a stop signal to the solenoid drive circuit 140 or stopping transmission from the CPU 130 to the solenoid drive circuit 140. In this way, the safety of the system can be ensured while utilizing the other functions of the in-vehicle control device 100. Then, when the solenoid drive circuit 140 is stopped, it is more preferable not to stop the solenoid drive circuit 140 as soon as the ground disconnection is detected, but to delay the solenoid drive circuit 140 for a few seconds and then stop the solenoid drive circuit 140. By doing so, it becomes possible to secure the optimum abnormal case processing for the system.

Further, in the present embodiment, it is preferable that the CPU 130 stops the power supply circuit 120 when it is determined that the ground 181 is disconnected (in other words, when the ground disconnection is detected). By doing so, the function of the in-vehicle control device 100 can be completely stopped, so that the safety of the system can be ensured. Then, when the power supply circuit 120 is stopped, it is more preferable not to stop the power supply circuit 120 as soon as the ground disconnection is detected, but to delay the power supply circuit 120 for a few seconds and then stop the power supply circuit 120. By doing so, it becomes possible to secure the optimum abnormal case processing for the system.

Further, in the present embodiment, when the CPU 130 determines that the ground 181 is disconnected (in other words, when the ground disconnection is detected), the ignition switch 300 may be opened. By doing so, the function of the in-vehicle control device 100 can be completely stopped, so that the safety of the system can be ensured. It is more preferable that when the ignition switch 300 is opened, the ignition switch 300 is opened after a delay of, for example, a few seconds, instead of immediately detecting the ground disconnection. By doing so, it becomes possible to secure the optimum abnormal case processing for the system.

Further, in the present embodiment, it has been described that the duty ratio of the PWM signal, which is the control signal of the solenoid drive circuit 140, is used in order to detect the ground disconnection. However, the duty ratio of the PWM signal is the power supply voltage of the battery 400 or the like. Since it is affected by the ambient temperature of the vehicle-mounted control device 100, the impedance of the solenoid 210 to be controlled, and the like, for example, by incorporating these parameters into the vehicle-mounted control device 100 and performing more precise control, the ground of the vehicle-mounted control device 100 can be obtained. Needless to say, the performance of detecting disconnection can be improved.

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 are designed without departing from the spirit of the present invention described in the claims. You can make changes.

100,100A In-vehicle control device 110, 160, 170, 180 Connector 120 Power supply circuit 130 CPU
131 AD port 140, 150 solenoid drive circuit 141 driver element 142 current detection resistor 143 arithmetic amplifier 144 diode 181,230, 240,410 ground 190 pull-up resistor 200 transmission 210, 220 solenoid 300 ignition switch 301, 302, 303, 304, 305,306,307,308 Ground current path 400 Battery 401,402,403 Ground current path 501,502,503,504,505 Ground current path

Claims (5)

It is an in-vehicle control device mounted on a vehicle.
A solenoid drive circuit that drives a solenoid and has a current detection resistor to detect the current flowing through the solenoid.
A control unit that controls the solenoid drive circuit and
A power supply circuit that generates power to be supplied to the control unit,
A pull-up resistor that pulls up the ground of the in-vehicle control device to the power supply voltage generated by the power supply circuit, and
An in-vehicle control device characterized by being equipped with. The pull-up resistor is the pull-up resistor when the current flowing through the pull-up resistor does not flow to the current detection resistor when the ground of the vehicle-mounted control device is normally connected and the ground of the vehicle-mounted control device is disconnected. The vehicle-mounted control device according to claim 1, wherein a current flowing through an up resistor flows through the current detection resistor. The control unit has the duty ratio of the pulse width modulation signal of the solenoid drive circuit when the ground of the vehicle-mounted control device is normally connected, and the duty ratio of the solenoid drive circuit when the ground of the vehicle-mounted control device is disconnected. The vehicle-mounted control device according to claim 1 or 2, wherein it is determined that the ground of the vehicle-mounted control device is disconnected when there is a difference from the duty ratio of the pulse width modulation signal. The vehicle-mounted control device according to claim 3, wherein the control unit stops the solenoid drive circuit when the ground of the vehicle-mounted control device is determined to be disconnected. The control unit further controls the power supply circuit.
The vehicle-mounted control device according to claim 3, wherein the control unit stops the power supply circuit when the ground of the vehicle-mounted control device is determined to be disconnected.

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