On-board electronic control unit

Abstract

Generally, the current threshold is set to a fixed value. Therefore, even if an abnormality occurs in the load and the resistance value becomes smaller, when the power supply voltage applied to the load is low, the current value also becomes lower and is lower than the threshold value, which may result in failure to detect overcurrent. In the present invention, in addition to providing a first detection unit that detects an overcurrent state indicating a load abnormality only through current value information, a second detection unit is provided that detects an abnormality of the load by calculating the resistance value of the load through the power supply voltage information applied to the load, thereby enabling overcurrent indicating a load abnormality to be detected even when the power supply voltage applied to the load is low.

Description

Technical Field

[0001] The present invention relates to an on-vehicle electronic control device, and its object is to improve the accuracy of detecting abnormality of a load driven by the on-vehicle electronic control device. Background Art

[0002] In vehicles, various sensors are used for engine control. The information from these sensors is input into the vehicle-mounted electronic control unit (ECU) and is effectively used for engine control. For example, the O2 sensor detects the concentration of oxygen in the exhaust gas. The mixture ratio of fuel and air (air-fuel ratio) is controlled based on the oxygen concentration information. When the O2 sensor does not work properly, proper combustion will not be possible, and the concentration of carbon monoxide, nitrogen oxides, etc. in the exhaust gas will increase, which may have a greater impact on the catalyst that purifies the exhaust gas. Therefore, the ECU is required to detect abnormalities of these sensors and the like at an early stage, and urge the user to take countermeasures such as maintenance.

[0003] The O2 sensor is activated by heating to an appropriate temperature and detects the oxygen concentration. Therefore, a heater is provided inside the sensor. However, in the case of a battery short circuit where the battery voltage is applied to both ends of the heater, the current does not flow to the heater and the sensor cannot be heated. The ECU detects the overcurrent caused by the battery short circuit, notifies the abnormality, and stops the heater drive.

[0004] As such, one of the main functions of the ECU is to detect abnormalities such as a battery short circuit in a load.

[0005] When the resistance value decreases due to the degradation of external components as loads, or when the power supply is disconnected (battery short circuit) due to the damage of the connection cable, a current larger than usual will flow in the ECU. The ECU detects this as an overcurrent and uses it to detect load abnormalities.

[0006] The ECU detects the current value of the driving load and detects it as overcurrent when the current value exceeds a threshold value. Generally, the current threshold value is set to a fixed value.

[0007] Conventionally, a technique for detecting only the current flowing to a load and detecting an overcurrent is disclosed in Patent Document 1. This detection is based on a fixed threshold value, and an overcurrent is detected as a current exceeding the threshold value.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2009-278724 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] The current value flowing through the load is determined by the applied power supply voltage and the resistance value of the load, the resistance value of the connecting cable, the wiring in the ECU, the resistance value of the driving element, etc. However, in general, other resistance values ​​are designed to be sufficiently small compared to the resistance value of the load. As conditions for the current value to become lower, there are cases where the power supply voltage applied to the load is lower and the resistance value of the load is increased. Therefore, even if an abnormality occurs in the load and the resistance value becomes smaller, when the power supply voltage applied to the load is lower, the current value will also become lower and fall below the threshold, which may cause the overcurrent to fail to be detected.

[0013] In vehicles, the power supply voltage may be low and not constant. As a result, the current value may be low, but even if the current value is abnormal as a load, it will not be detected as overcurrent if it is lower than the threshold value, and thus it cannot be detected as abnormality.

[0014] An object of the present invention is to detect an overcurrent indicating an abnormality of the load even when a power supply voltage applied to the load is low.

[0015] Technical means of solving problems

[0016] In order to solve the above-mentioned problems, the vehicle-mounted electronic control device of the present invention is provided with, in addition to a first detection unit that detects an overcurrent state indicating a load abnormality only through current value information, a second detection unit that detects a load abnormality by calculating the resistance value of the load through power supply voltage information applied to the load. Thus, even when the power supply voltage applied to the load is low, overcurrent indicating a load abnormality can be detected.

[0017] In addition, in the present invention, by providing means for stepwise switching the threshold for detecting overcurrent according to the power supply voltage applied to the load, overcurrent indicating load abnormality can be detected even when the power supply voltage applied to the load is low.

[0018] Effects of the Invention

[0019] According to the present invention, by adding a new second detection unit to the existing first detection unit, even when the power supply voltage applied to the load is lower than before, it is possible to detect an overcurrent indicating a load abnormality. It should be noted that if the second detection unit is executed by a program of a computing device, it can be implemented by an existing circuit configuration.

[0020] Furthermore, according to the present invention, when the power supply voltage applied to the load is high, overcurrent detection is performed only by the existing first detection means, so that the processing load when the second detection means is executed by a program of the computing device can be reduced.

[0021] Furthermore, according to the present invention, since the threshold for detecting overcurrent can be switched in stages according to the power supply voltage applied to the load, the burden of the second detection unit can be reduced by a small change in the existing first detection unit or by a program of a computing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a circuit diagram of the vehicle-mounted electronic control device of the present invention.

[0023] Figure 2 is the current threshold in Embodiment 1 of the present invention.

[0024] Figure 3 It is the current threshold value (straight line) in Example 2 of the present invention.

[0025] Figure 4 It is the current threshold value (three stages) in the third embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will describe embodiments of the present invention using the accompanying drawings. It should be noted that the embodiments can be combined.

[0027] Example 1

[0028] use Figure 1 and Figure 2 , Example 1 of the present invention is described.

[0029] In order to drive the load 3, the battery 2 is connected to the load 3 as a load power source.

[0030] The ECU 1 includes a driving element 103 for driving the load 3 , a current detection resistor 104 for detecting a current flowing through the load 3 , an integrated circuit 102 , and a computing device 101 .

[0031] The driving element 103 drives the load 3 according to the control signal 203 from the integrated circuit 102 .

[0032] The current detection resistor 104 obtains a voltage value proportional to the current flowing to the load 3. The obtained voltage value is input to the integrated circuit 102 as the load current value information 204.

[0033] The computing device 101 uses input signals from sensors and the like connected to the ECU 1 to perform operations for driving the load 3. The integrated circuit 102 outputs a control signal 203 to the driving element 103 according to a control instruction from the computing device 101. The integrated circuit 102 includes a first diagnostic unit that diagnoses an overcurrent when the load current value information 204 exceeds a current threshold. This detection method is a conventionally known method and is used herein as a first detection unit. In addition, the current threshold is generally set to a fixed value.

[0034] As described above, the current threshold of the integrated circuit 102 is set to a fixed value, but the value that can be taken has a certain range of variation due to individual differences caused by manufacturing variations and environmental factors such as temperature.

[0035] like Figure 2 As shown, there are individuals with a maximum current threshold 401 and individuals with a minimum current threshold 402 .

[0036] In the past, overcurrent diagnosis was performed at a voltage value where the current value 301 exceeded the maximum current threshold 401. However, in recent years, the demand for overcurrent diagnosis at low voltage has been increasing, and it is required to perform overcurrent diagnosis at a voltage where the current value 301 is lower than the maximum current threshold 401. In this case, the following new issues have been discovered: Figure 2 As shown, if the current threshold is the minimum current threshold 402, the overcurrent diagnosis can be performed, but if the current threshold is the maximum current threshold 401, the overcurrent diagnosis may not be performed.

[0037] Therefore, in this embodiment, in order to detect the abnormality of the load, the second detection unit is implemented in addition to the first detection unit.

[0038] Next, the second detection unit will be described.

[0039] The computing device 101 communicates with the integrated circuit 102 and the communication line 201, and obtains the current value information 204 flowing to the load 3 input to the integrated circuit 102. In addition, the power supply voltage applied to the load 3 is input to the computing device 101 as the load power supply voltage value information 202 via an analog-to-digital converter (not shown).

[0040] When the computing device 101 determines that the power supply voltage applied to the load is low based on the load power supply voltage value information 202 applied to the load 3, the computing device 101 calculates the resistance value of the load based on the current value information 204 flowing to the load 3 and the load power supply voltage value information 202 applied to the load 3, thereby executing the second detection unit for detecting the abnormality of the load.

[0041] The resistance value of the load can be obtained by simply dividing the load power supply voltage value information 202 by the current value information 204. More specifically, the resistance value can be obtained by subtracting the resistance value of the cable connecting the load and the ECU, the wiring in the ECU, the resistance value of the driving element, etc. from the simply obtained resistance value.

[0042] For example, when the load is 10 ohms in a normal state and does not become less than 9 ohms even if the initial deviation and temperature characteristics are taken into consideration, it is desirable to reliably detect less than 2 ohms as a load abnormality. This is achieved by incorporating into the computing device 101 a process of determining that the load is abnormal if the calculation result of the computing device 101 is less than 3 ohms, taking into account errors in the load power supply voltage value information 202 and the current value information 204.

[0043] It should be noted that in this example, if the resistance value judged as a load abnormality is set to a value close to 9 ohms, it may be easier to capture signs of abnormality before the battery is completely short-circuited, and load degradation can be discovered at an early stage.

[0044] On the contrary, if the value is set to be close to 2 ohms, it becomes easy to detect only the truly abnormal cases, and the possibility of false alarms in which the load is detected as abnormal even though it is a normal load can be reduced.

[0045] If the resistance threshold is set to an intermediate value as a compromise between the two, false alarms can be reduced and signs of abnormality can be detected.

[0046] In this embodiment, the current detection resistor 104 is used as a current detection unit for obtaining the current value information 204 . However, the driving element 103 may be built into the integrated circuit 102 to form a current mirror circuit to detect the current.

[0047] In addition, in this embodiment, the computing device 101 uses the communication line 201 with the integrated circuit 102 as a unit for obtaining the current value information 204, but it is also possible to output the current value information 204 as amplified voltage information, for example, through the integrated circuit 102, and the computing device 101 uses an analog-to-digital converter to receive the information.

[0048] It should be noted that, generally, the computing device 101 is composed of a microcomputer, but can also be implemented by FPGA, DSP, ASIC, etc.

[0049] Furthermore, in this embodiment, the load 3 is connected to the power supply and the driving element 103 is formed as a low-side circuit to absorb current, but the same effect can be obtained in a high-side circuit where the load 3 is grounded and the driving element 103 discharges current.

[0050] In this embodiment, at a voltage where the current when the load resistance is abnormal exceeds the maximum threshold current value, only the first detection unit that detects the abnormality based on the load current through the integrated circuit is used. In addition, in this embodiment, at a voltage where the current when the load resistance is abnormal is less than the maximum threshold current value and the abnormality may not be detected by the first detection unit, both the second detection unit and the first detection unit are used, and when either one is judged to be abnormal, it is determined that there is an abnormality in the load, wherein the second detection unit detects the abnormality with the resistance value obtained by the operation device 101 based on the load power supply voltage information and the current value information input to the operation device 101. According to this embodiment, load abnormality detection is performed in an area where the abnormality can be detected by the integrated circuit 102 without using the operation device 101, thereby reducing the calculation load of the operation device 101, and in a low voltage area where the abnormality of the load cannot be detected only by the integrated circuit 102, the load resistance is calculated by the operation device 101 to detect the abnormality of the load, thereby enabling the abnormality of the load to be detected even in a low voltage area. After detecting the abnormality, the ECU 1 performs the following processing: notifying the occurrence of the abnormality to the outside of the ECU 1 through a warning light, an alarm sound, etc., and stopping the driving of the load 3, etc.

[0051] Example 2

[0052] Below, use Figure 3 Embodiment 2 of the present invention will be described. The description of the same configuration as that of Embodiment 1 will be omitted.

[0053] As described in Example 1, the first detection unit has Figure 2 The maximum current threshold 401 and the minimum current threshold 402 are shown in the figure. In the first embodiment, these two values ​​are constant values ​​(fixed values) regardless of the power supply voltage V applied to the load 3. In contrast, in the present embodiment, Figure 3 As shown, there are a maximum current threshold 501 and a minimum current threshold 502 which are proportional to the power supply voltage V applied to the load 3.

[0054] Here, the minimum current threshold 502 is set to a value greater than the current value 302 that can be taken when the load resistance is normal, and since it is proportional to the power supply voltage V applied to the load 3 and changes in the same manner as the current value 302 in normal times, it is not detected as an overcurrent.

[0055] In addition, the maximum current threshold 501 is set to a value smaller than the current value 301 that can be taken when the load resistance is abnormal, and because it is proportional to the power supply voltage V applied to the load 3 and changes in the same manner as the current value 301 during the abnormality, it can be detected as an overcurrent.

[0056] It should be noted that the maximum current threshold 501 and the minimum current threshold 502 can be defined as resistance values, and can be obtained by simply dividing the load power supply voltage value information 202 by the current value information 204 as described in Example 1. If a microcomputer is used, it is possible to perform calculations in real time and diagnose whether the load 3 is abnormal or normal.

[0057] Example 3

[0058] Below, use Figure 4 This embodiment 3 is described.

[0059] Figure 4 It is simplified Figure 3 The maximum current threshold 501 and the minimum current threshold 502 are shown in the figure after setting. The maximum current threshold 601 and the minimum current threshold 602 shown here have three levels of values ​​with respect to the power supply voltage V applied to the load 3.

[0060] The maximum current threshold 601 and the minimum current threshold 602 do not need to be calculated in real time through the load power supply voltage value information 202 and the current value information 204. They only need to be pre-set to three current thresholds relative to the load power supply voltage value information 202. When implemented by a microcomputer, the processing load will not increase due to the calculation. In addition, it can be achieved by inputting the load power supply voltage information 202 into the integrated circuit 102 and increasing the current threshold from one to three.

[0061] It should be noted that in this embodiment, three stages of thresholds are set relative to the power supply voltage V applied to the load 3, but it is not necessarily required to be three stages. In some cases, two stages are sufficient. Conversely, by setting it to four stages or more, a wide range of power supply voltages can be coped with.

[0062] Explanation of symbols

[0063] 1…on-vehicle electronic control device, 2…battery, 3…load, 101…computing device, 102…integrated circuit, 103…driving element, 104…current detection resistor, 201…computing device-integrated circuit communication line, 202…load power supply voltage value information, 203…driving element control signal line, 204…load current value information, 301…voltage-current straight line when load resistance is abnormal, 302…voltage-current straight line when load resistance is normal, 401…maximum current threshold of embodiment 1, 402…minimum current threshold of embodiment 1, 501…maximum current threshold (straight line) of embodiment 2, 502…minimum current threshold (straight line) of embodiment 2, 601…maximum current threshold (three stages) of embodiment 2, 602…minimum current threshold (three stages) of embodiment 2.

Claims

1. A vehicle-mounted electronic control device, comprising: A driving element, which is used to drive an external element; a current detection unit, configured to detect a current value flowing through the external element; and a control unit that uses the information of the current value to send a control instruction to the driving element, The vehicle-mounted electronic control device is characterized by comprising: An integrated circuit comprising the control unit; a computing device that acquires the current value information from the integrated circuit; a first detection unit that detects an abnormality of the external element based on the current value information obtained from the current detection unit being greater than a threshold value of the current of the external element; and a second detection unit that calculates the resistance value of the external element by using the current value information and the power supply voltage information applied to the external element, and detects an abnormality when the resistance value of the external element is below a threshold value of the resistance of the external element, The integrated circuit executes a first detection unit, The computing device executes a second detection unit, When the voltage applied to the external element exceeds a predetermined voltage, the first detection unit is executed, but the second detection unit is not executed. When the voltage applied to the external element is below a predetermined voltage, at least the second detection unit is executed.

2. The vehicle-mounted electronic control device according to claim 1, characterized in that: When the voltage applied to the external element is equal to or lower than a predetermined voltage, both the first detection unit and the second detection unit are executed, and when an abnormality is detected in either one, it is determined that the external element is abnormal.

3. The vehicle-mounted electronic control device according to claim 1 or 2, characterized in that: The predetermined voltage is a voltage equal to or higher than a voltage at which a current value when the external element is abnormal intersects a maximum threshold value of a current for determining that the external element is abnormal.

4. A vehicle-mounted electronic control device having: A driving element, which is used to drive an external element; a current detection unit, configured to detect a current value flowing through the external element; and a control unit that uses the information of the current value to send a control instruction to the driving element, The vehicle-mounted electronic control device is characterized in that: A detection unit is provided, which performs a first detection for detecting an abnormality of the external element based on the current value information obtained from the current detection unit being above a threshold value of the current of the external element; and a second detection for calculating a resistance value of the external element by using the current value information and information on a power supply voltage applied to the external element, and detecting an abnormality based on the resistance value of the external element being below the threshold value of the resistance of the external element, The detection unit performs the first detection but does not perform the second detection when the voltage applied to the external element exceeds a predetermined voltage. When the voltage applied to the external element is below a predetermined voltage, at least a second detection is performed, The detection unit has the following relationship in which the threshold current is proportional to the voltage: When the power supply voltage applied to the external element is low, the threshold value of the current for judging the abnormality of the external element is set low. When the power supply voltage applied to the external element is high, the threshold value of the current for judging that the external element is abnormal is set high.

5. A vehicle-mounted electronic control device, comprising: A driving element, which is used to drive an external element; a current detection unit, configured to detect a current value flowing through the external element; and a control unit that uses the information of the current value to send a control instruction to the driving element, The vehicle-mounted electronic control device is characterized in that: A detection unit is provided for performing a first detection for detecting an abnormality of the external element based on the current value information obtained from the current detection unit being equal to or greater than a threshold value of the current of the external element; and a second detection of calculating the resistance value of the external element by using the current value information and the power supply voltage information applied to the external element, and detecting an abnormality according to the resistance value of the external element being below a threshold value of the resistance of the external element, The detection unit performs the first detection but does not perform the second detection when the voltage applied to the external element exceeds a predetermined voltage. When the voltage applied to the external element is below a predetermined voltage, at least a second detection is performed, The detection unit has a function of switching a threshold value of a current for determining whether the external element is abnormal, based on information on a power supply voltage applied to the external element.

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