JP4280145B2 - Insulation resistance drop detector and self-diagnosis method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation resistance decrease detector and its self-diagnostic method capable of self-diagnosing whether or not functions of the detector itself are normally working. <P>SOLUTION: The insulation resistance decrease detector detects the decrease of insulation resistance in a vehicle including a direct current power source system electrically insulated from the vehicle body and an alternate current circuit connected with the direct current power source system comprises a resistor Rs for self-diagnosis and a switch element Q directly connected between a connection point of a detection resistor Rd and an insulation resistor Ri and the ground. It also comprises a control means 52 for controlling the switch element Q to be off for insulation resistance decrease detection functioning and to be on for self diagnosis functioning, and a judgment means 52 for judging a degradation in failure of the detection resistor Rd when the switch element Q is turned on and the voltage Vx value of connection point appearing in the connection point of the detection resistor Rd and the insulation resistor Ri is detected to be different from a reference value. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to an insulation resistance decrease detector that detects a decrease in insulation resistance between a vehicle body and a DC power source in a high voltage vehicle such as an EV (Electric Vehicle) or an HEV (Hybrid Electric Vehicle), and in particular, the operation of the detector itself. The present invention relates to an insulation resistance reduction detector capable of self-diagnosis and a self-diagnosis method thereof.

  Conventionally, as an insulation resistance lowering detector, for example, there is a ground fault detection circuit for an electric vehicle described in Patent Document 1. As shown in FIGS. 3 and 4, the ground fault detection circuit includes a battery group B provided as a high-voltage DC power source (for example, 200 to 300 V), and a positive bus 4 that is a DC positive power feed line from the battery group B. And an inverter 2 as a DC-AC converter for converting a direct current fed through a negative bus 5 which is a direct current negative electrode feeder to an alternating current, and a U phase wire 6 and a V phase wire 7 which are alternating current feeders from the inverter 2. And for detecting a ground fault from the battery group B to the vehicle body E in the traveling drive circuit system A of the electric vehicle composed of the AC motor 3 fed with AC via the W-phase line 8. An oscillation circuit 10 as an output circuit and a detection unit 20 as a voltage level change detection circuit, and between a connection point P between the oscillation circuit 10 and the detection unit 20 and the plus bus 4 of the battery group B of the traveling drive circuit system A Are connected by a coupling capacitor 10A, the DC component is cut off.

  In the oscillation circuit 10, the oscillator 11 generates a rectangular wave pulse having a constant frequency with a duty ratio of 50% (see the left and right in FIG. 4A), and the impedance converter 12 in the next stage outputs the rectangular wave pulse of the oscillator 11. The signal is output with the duty ratio as it is, and the AC signal output of the oscillation circuit 10 appears at the connection point P through the detection resistor 13. The detection resistor 13 acts as a voltage divider by the ground fault resistor 31 when a ground fault occurs.

  The detector 20 is provided with a comparator 21 for comparing the voltage level at the connection point P between the detection resistor 13 where the AC signal output of the oscillation circuit 10 appears and the coupling capacitor 10A with the reference voltage V1. Point P is connected to the inverting input terminal of the comparator 21. A reference voltage circuit in which a reference voltage V1 is set by voltage dividing resistors 22 and 23 is connected to the non-inverting input terminal of the comparator 21.

  Note that the operational amplifiers constituting the impedance converter 12 and the comparator 21 protect against reverse voltage and overvoltage when a ground fault occurs. Therefore, a protective diode 15 is provided on the output side of the impedance converter 12 and on the input side of the comparator 21. -18 are connected.

  With such a circuit configuration, the insulation resistance 31 shown in FIG. 3 is extremely larger than the detection resistance 13 in normal times when no ground fault occurs, and the rectangular wave pulse is divided by the insulation resistance 31 and the detection resistance 13. From the connection point P where the value appears, a rectangular pulse having a peak value higher than a preset reference voltage V1 is output (see the left side of FIG. 4B).

  Therefore, a rectangular wave pulse having a peak value higher than a preset reference voltage V1 is input to the inverting input terminal of the comparator 21, and the output of the comparator 21 is a rectangular wave pulse with a duty ratio of 50% (see FIG. (See the left side of 4 (c)). Then, the smoothing voltage Vr appearing by the smoothing circuit 26 of the resistor 24 and the capacitor 25 becomes lower than the reference voltage (see the left side of FIG. 4D), which is input to the non-inverting input terminal of the comparator 27 and compared. The output of the device 27 becomes a low level indicating normal (see the left side of FIG. 4 (e)).

  However, when a ground fault occurs between the negative bus and the vehicle body E and the insulation resistance 31 shown in FIG. 3 decreases, a value obtained by dividing a rectangular wave pulse by the insulation resistance 31 and the detection resistance appears from the connection point P. Outputs a rectangular pulse having a peak value lower than the reference voltage V1 (see the right side of FIG. 4B). For this reason, a rectangular wave pulse having a peak value lower than the reference voltage V1 is input to the inverting input terminal of the comparator 21, and the duty ratio of the comparator 21 changes to 100% (see the right side of FIG. 4C). .

As a result, the smoothing voltage Vr appearing by the smoothing circuit 26 of the resistor 24 and the capacitor 25 becomes higher than the reference voltage (see the right side of FIG. 4D), and is input to the non-inverting input terminal of the comparator 27. The output of the comparator 27 becomes a high level indicating a decrease in insulation resistance (see the right side of FIG. 4 (e)). As described above, when a ground fault occurs in the battery group B, the ground fault can be detected from the logic level of the comparator 27.
JP-A-8-70503

  However, the above-described ground fault detection circuit has a problem that it cannot perform a self-diagnosis as to whether or not a failure has occurred in the components constituting the ground fault detection circuit.

  Therefore, the present invention focuses on the above-described problems, and an object thereof is to provide an insulation resistance lowering detector capable of self-diagnosis whether the operation of the detector itself is normally performed and a self-diagnosis method thereof. To do.

In order to solve the above-mentioned problem, the invention according to claim 1 detects a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system. An insulation resistance lowering detector, comprising: a pulse signal generating means for outputting a pulse signal; and applying the pulse signal from the pulse signal generating means to the DC power supply system via a detection resistor and a coupling capacitor for insulation. Self-diagnosis of an insulation resistance decrease detector comprising a decrease detection means for detecting a decrease in the insulation resistance in accordance with a value of a connection point voltage appearing at a connection point between the detection resistor and the coupling capacitor during a resistance decrease detection operation. a method, during the self-diagnosis, connect the self-diagnostic resistor between ground and the connection point of the coupling capacitor and the detecting resistor, the mosquito and the detection resistor Value of the connection point voltage appearing at the connection point of the pulling capacitor, when it has been detected that is a reference value different, and judging with the detection resistor degradation or failure.

According to a second aspect of the present invention, a reduction in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system is detected. An insulation resistance lowering detector, comprising: a pulse signal generating means for outputting a pulse signal; and applying the pulse signal from the pulse signal generating means to the DC power supply system via a detection resistor and a coupling capacitor for insulation. Self-diagnosis of an insulation resistance decrease detector comprising a decrease detection means for detecting a decrease in the insulation resistance in accordance with a value of a connection point voltage appearing at a connection point between the detection resistor and the coupling capacitor during a resistance decrease detection operation. a method, during the self-diagnosis, connect the self-diagnostic resistor between ground and the connection point of the coupling capacitor and the detecting resistor, the self-diagnosis resistor Anti value is varied, detects that the change rate of the connection point voltage the response to the variable resistance value of the self-diagnostic resistor at the connection point of the coupling capacitor and the detecting resistor is different from the reference change rate In this case, it is determined that the detection resistor is deteriorated or failed.

According to a third aspect of the present invention, a reduction in insulation resistance is detected in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system. An insulation resistance lowering detector, comprising: a pulse signal generating means for outputting a pulse signal; and applying the pulse signal from the pulse signal generating means to the DC power supply system via a detection resistor and a coupling capacitor for insulation. during the resistance drop detection operation, the insulation resistance drop detector and a drop detecting means for detecting a drop in the insulation resistance in accordance with the value of the connecting point voltage at the connection point of the coupling capacitor and the detecting resistor, wherein and diagnostics resistor and switch element which are connected in series between the ground and the detection resistor and the connection point of the coupling capacitor, the switching element, And control means for controlling to turn on off and during the self-diagnosis operation during edge resistance drop detection operation, the switching element when turned on, the connection point voltage appearing at the connection point of the coupling capacitor and the detecting resistor When it is detected that the value is a value different from the reference value, there is further provided judgment means for judging that the detection resistor has deteriorated or failed.

According to a fourth aspect of the present invention, a reduction in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system is detected. An insulation resistance lowering detector, comprising: a pulse signal generating means for outputting a pulse signal; and applying the pulse signal from the pulse signal generating means to the DC power supply system via a detection resistor and a coupling capacitor for insulation. In an insulation resistance decrease detector, comprising a decrease detection means for detecting a decrease in the insulation resistance in accordance with a value of a connection point voltage appearing at a connection point between the detection resistor and the coupling capacitor during a resistance decrease detection operation, and diagnostics resistor and switch element which are connected in series between the ground and the detection resistor and the connection point of the coupling capacitor, the switching element, Control means for controlling to turn off at the time of edge resistance drop detection operation and on at the time of self-diagnosis operation; variable means for varying the resistance value of the self-diagnosis resistor; and when the switch element is turned on, When it is detected that the change rate of the connection point voltage appearing at the connection point of the detection resistor and the coupling capacitor in accordance with the variable resistance value of the diagnostic resistor is different from the reference change rate, the detection resistor And a determination means for determining deterioration or failure.

According to a fifth aspect of the present invention, a reduction in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system is detected. An insulation resistance lowering detector, comprising: a pulse signal generating means for outputting a pulse signal; and applying the pulse signal from the pulse signal generating means to the DC power supply system via a detection resistor and a coupling capacitor for insulation. In an insulation resistance decrease detector, comprising a decrease detection means for detecting a decrease in the insulation resistance in accordance with a value of a connection point voltage appearing at a connection point between the detection resistor and the coupling capacitor during a resistance decrease detection operation, and diagnostics resistor and switch element which are connected in series between the ground and the detection resistor and the connection point of the coupling capacitor, the switching element, Rate of change and control means for controlling so as to function as a variable resistor when the self-diagnosis operation, the connection point voltage between the detection resistor during the self-diagnosis operation at the connection point of the coupling capacitor as well as off during edge resistance drop detection operation Is further provided with determination means for determining that the detection resistor has deteriorated or failed when it is detected that it is different from the reference change rate.

In order to solve the above-mentioned problem, the invention according to claim 6 detects a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from the vehicle body and an AC circuit connected to the DC power supply system. An insulation resistance lowering detector, comprising: a pulse signal generating means for outputting a pulse signal; and applying the pulse signal from the pulse signal generating means to the DC power supply system via a detection resistor and a coupling capacitor for insulation. In an insulation resistance decrease detector, comprising a decrease detection means for detecting a decrease in the insulation resistance in accordance with a value of a connection point voltage appearing at a connection point between the detection resistor and the coupling capacitor during a resistance decrease detection operation, a switching element and the detection resistor and the connection point of the coupling capacitor is connected between ground and the switching element, the insulation resistance drop detection operation While the full, and control means for controlling so as to function as a variable resistor when the self-diagnosis operation, the change rate of the connection point voltage between the detection resistor during the self-diagnosis operation at the connection point of the coupling capacitor, reference change rate And determining means for determining that the detection resistor has deteriorated or failed when it is detected that the detection resistance is different.

The invention according to claim 7 made to solve the above problem detects a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from the vehicle body and an AC circuit connected to the DC power supply system. An insulation resistance lowering detector, comprising: a pulse signal generating means for outputting a pulse signal; and applying the pulse signal from the pulse signal generating means to the DC power supply system via a detection resistor and a coupling capacitor for insulation. In an insulation resistance decrease detector, comprising a decrease detection means for detecting a decrease in the insulation resistance in accordance with a value of a connection point voltage appearing at a connection point between the detection resistor and the coupling capacitor during a resistance decrease detection operation, detection resistor and the connecting point of the coupling capacitors and field effect transistors connected between ground and the field effect transistor, the insulation resistance While off during the lower detection operation, and control means for controlling so as to function as a variable resistor when the self-diagnosis operation, the change rate of the connection point voltage between the detection resistor during the self-diagnosis operation at the connection point of the coupling capacitor And determining means for determining that the detection resistance is deteriorated or failed when it is detected that the difference from the reference change rate is different.

  The invention according to claim 8, which has been made to solve the above problem, is the insulation resistance lowering detector according to any one of claims 3 to 7, wherein a bus connecting the DC power supply system to the AC circuit is provided. And a switch connected to the DC power supply system, controlled by the control means, and turned on during the insulation resistance drop detection operation and turned off during the self-diagnosis operation.

  According to the first aspect of the present invention, when the surge resistance or overvoltage exceeding the withstand voltage is applied to the detection resistor, the detection resistor is deteriorated for some reason, and the resistance value of the detection resistor is changed from the original normal value. In the case of increase, it is possible to self-diagnose the presence or absence of detection resistance deterioration or failure.

  According to the second aspect of the present invention, when the surge resistance or overvoltage exceeding the withstand voltage is applied to the detection resistor, the detection resistor is deteriorated due to some cause, the resistance value of the detection resistor is changed from the original normal value. In the case of increase, by monitoring the rate of change of the connection point voltage, it is possible to perform self-diagnosis with high accuracy whether the detection resistor is deteriorated or there is a failure.

  According to the third aspect of the present invention, when the surge resistance or overvoltage exceeding the withstand voltage is applied to the detection resistor, the detection resistor is deteriorated for some reason, and the resistance value of the detection resistor is changed from the original normal value. In the case of increase, it is possible to self-diagnose the presence or absence of detection resistance deterioration or failure.

  According to the invention of claim 4, when the surge resistance or overvoltage exceeding the withstand voltage is applied to the detection resistor, the detection resistor is deteriorated due to some cause, or the resistance value of the detection resistor is changed from the original normal value. In the case of increase, by monitoring the rate of change of the connection point voltage, it is possible to perform self-diagnosis with high accuracy whether the detection resistor is deteriorated or there is a failure.

  According to the fifth aspect of the present invention, the detection resistor is deteriorated by applying a surge voltage or an overvoltage exceeding the withstand voltage, or is broken for some reason, and the resistance value of the detection resistor is changed from the original normal value. In the case of increase, by monitoring the rate of change of the connection point voltage, it is possible to perform self-diagnosis with high accuracy whether the detection resistor is deteriorated or there is a failure. In addition, since the switch element is used as a switch and variable resistance element, self-diagnosis can be performed with a simple circuit configuration.

  According to the sixth aspect of the present invention, the resistance value of the detection resistor is changed from the original normal value because the detection resistor is deteriorated by applying a surge voltage or an overvoltage exceeding its withstand voltage, or is broken for some reason. In the case of increase, by monitoring the rate of change of the connection point voltage, it is possible to perform self-diagnosis with high accuracy whether the detection resistor is deteriorated or there is a failure. Further, since the switch element is used as a switch and variable resistance element, self-diagnosis can be performed with a simple circuit configuration.

  According to the seventh aspect of the present invention, a switch and variable resistance element can be realized using a field effect transistor.

  According to the eighth aspect of the invention, even when the insulation resistance is lowered (ground fault), it is possible to accurately self-diagnose the presence or absence of detection resistance deterioration or failure.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an insulation resistance lowering detector and a self-diagnosis method thereof according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit diagram showing an embodiment of an insulation resistance lowering detector that implements the self-diagnosis method of the present invention. In FIG. 1, a battery group B includes a high-voltage DC power source (for example, 200) that supplies power to a high-voltage vehicle such as an EV or HEV via a positive bus P that is a DC positive feed line and a negative bus N that is a DC negative feed line. ~ 300V). The positive bus P and the negative bus N supply power from a DC power supply system of the battery group B to a travel drive circuit system (not shown) of a high-voltage vehicle via an AC circuit (not shown) such as an inverter.

  The insulation resistance decrease detector 50 is for detecting a decrease in the insulation resistance Ri between the plus bus P or the minus bus N of the battery group B and the vehicle body E. In FIG. 1, the insulation resistance Ri is shown only between the negative bus N and the vehicle body E. The insulation resistance decrease detector 50 includes a pulse oscillation circuit 51 as a pulse signal generation means, a control circuit 52 as a decrease detection means, a control means, a variable means and a determination means, a low-pass filter 53, a waveform shaping circuit 54, A self-diagnosis circuit 55, a detection resistor Rd, and a coupling capacitor Co for cutting off DC are provided.

  The detection resistor Rd and the coupling capacitor Co are connected in series between the insulation resistance detection terminal Vi connected between the negative side of the battery group B and the negative bus N and the pulse oscillation circuit 51. The resistance value of the detection resistor Rd is considerably smaller than the resistance value of the insulation resistance Ri (for example, several mega ohms) when not decreasing, and is smaller than the resistance value of the insulation resistance Ri after the decrease (for example, almost zero ohms at the time of ground fault). It is chosen to be bigger. The resistance value of the detection resistor Rd is set to 100 kilohms as an example.

  The pulse oscillation circuit 51 includes, for example, a Colpitts oscillation circuit, a crystal oscillation circuit, a CR oscillation circuit, etc., and outputs a rectangular wave pulse signal P1 having a predetermined peak value and applies it to one end of the detection resistor Rd. Here, the peak value means a voltage value of the wave height of one pulse signal. The pulse oscillation circuit 51 is controlled by the control signal S1 from the control circuit 52, and can change the frequency of the output pulse by changing the frequency division value of the frequency divider constituting the PLL circuit. .

  The control circuit 52 is composed of, for example, a microcomputer.

  The low-pass filter 53 includes a resistor Rf and a capacitor Cf connected in series between a connection point between the detection resistor Rd and the coupling capacitor Co and the ground. The low-pass filter 53 passes a signal component having a predetermined frequency or less from a connection point voltage Vx appearing at a connection point between the detection resistor Rd and the coupling capacitor Co (in other words, a connection point between the detection resistor Rd and the insulation resistor Ri). It is provided for the purpose of removing noise superimposed on the point voltage Vx.

  The waveform shaping circuit 54 has an input side connected to a connection point between the resistor Rf and the capacitor Cf of the low-pass filter 53 and an output side connected to the control circuit 52, and shapes the connection point voltage Vx that has passed through the low-pass filter 53. Output.

  The self-diagnosis circuit 55 includes a self-diagnosis resistor Rs and a junction field effect transistor (FET) Q connected in series between a connection point between the detection resistor Rd and the coupling capacitor Co and the ground. The field effect transistor Q is turned off during a normal insulation resistance reduction detection operation, and operates as a switch element that is turned on by being controlled by the control signal S2 from the control circuit 52 during the self-diagnosis operation. The self-diagnosis resistor Rs has a resistance value (for example, 200 kΩ) that is considerably smaller than a normal resistance value in which the insulation resistance Ri does not decrease.

  The self-diagnosis circuit 55 includes a switch SW1 connected between the plus side of the battery group B and the plus bus P, and a switch SW2 connected between the minus side of the battery group B and the minus bus N. The switches SW1 and SW2 are composed of relays or the like and are normally turned on, but are turned off by being controlled by the control signal S3 from the control circuit 52 during the self-diagnosis operation.

  Further, the connection point voltage Vx appearing at the connection point between the detection resistor Rd and the coupling capacitor Co is a value obtained by dividing the peak value of the pulse signal P1 from the pulse oscillation circuit 51 by the detection resistor Rd and the insulation resistor Ri. . Therefore, when the insulation resistance Ri is larger than that of the detection resistance Rd, a pulse having a peak value substantially the same as that of the pulse signal P1 appears as the connection point voltage Vx. On the other hand, when the insulation resistance Ri is lowered, the connection point voltage Vx is also reduced and becomes almost zero at the time of ground fault.

  Next, the operation of the above-described insulation resistance lowering detector will be described below.

  First, the normal insulation resistance decrease detection operation will be described. The control circuit 52 functions as an insulation resistance decrease detection means during normal operation, and outputs a pulse signal P1 having a predetermined frequency (for example, 3 Hz) from the pulse oscillation circuit 51. Based on the output peak value of the low-pass filter 53 at this time, the decrease in the insulation resistance Ri is detected. Specifically, when the output peak value of the low-pass filter 53 is substantially equal to the peak value of the pulse signal P1, the control circuit 52 determines that the insulation resistance has not decreased. On the other hand, when the output peak value of the low-pass filter 53 is approximately 0, the control circuit 52 determines that the insulation resistance Ri has decreased (ie, ground fault).

  Next, the self-diagnosis operation of the insulation resistance lowering detector will be described. The control circuit 52 detects an insulation resistance decrease based on a predetermined trigger signal such as an ON signal of an ignition switch (not shown) or a self-diagnosis start switch (not shown) of a high-voltage vehicle. Is stopped and the self-diagnosis operation starts.

  When the self-diagnosis operation is started, the control circuit 52 controls the field-effect transistor Q to be turned on from off by outputting a control signal S2 that is low level at normal time and high level at the time of self-diagnosis. As a result, the self-diagnosis resistor Rs is connected to the connection point between the detection resistor Rd and the coupling capacitor Co (in other words, the connection point between the detection resistor Rd and the insulation resistor Ri).

  Thereby, the connection point voltage Vx is divided by the parallel combined resistance value of the insulation resistance Ri and the self-diagnosis resistance Rs and the resistance value of the detection resistance Rd. The voltage dividing ratio at this time is smaller than the voltage dividing ratio before the self-diagnosis resistor Rs is connected because the resistance value of the self-diagnosis resistor Rd is considerably smaller than the normal resistance value of the insulation resistance Ri. Therefore, the voltage of the connection point voltage Vx is lower than the voltage value before the start of self-diagnosis. Since the resistance value of the self-diagnosis resistor Rs is known in advance, the degree of voltage drop of the connection point voltage Vx before the self-diagnosis starts and after the self-diagnosis starts can also be known in advance.

  Incidentally, the resistance value of the detection resistor Rd may increase due to deterioration or failure. For example, there are cases as described below as the cause of the deterioration of the detection resistor Rd. That is, the positive bus P and the negative bus N are connected from the DC power supply system of the battery group B to the travel drive circuit system (including a motor or the like, not shown) of the high-voltage vehicle via an AC circuit (not shown) such as an inverter. Power is being supplied. Therefore, noise generated in the inverter, motor, etc. is transmitted from the plus bus P or minus bus N to the insulation resistance drop detector 50 via the insulation resistance detection terminal Vi, and applied to the detection resistor Rd via the coupling capacitor Co. May be. When the noise generated by the inverter or the motor is applied as a surge voltage or overvoltage having a large amplitude with respect to the withstand voltage of the detection resistor Rd, the detection resistor Rd suddenly deteriorates and its resistance value is reduced. May increase from the normal resistance value.

  When the resistance value of the detection resistor Rd increases due to such deterioration or failure, the voltage dividing ratio at the connection point between the detection resistor Rd and the coupling capacitor Co during self-diagnosis is higher than that when the resistance value of the detection resistor Rd is normal. Becomes even smaller. Therefore, due to the deterioration of the detection resistor Rd or the occurrence of a failure, the voltage of the connection point voltage Vx is higher than the voltage value (reference value) after the start of the above self-diagnosis, which is known in advance when the resistance value of the detection resistor Rd is normal. Further decrease.

  Therefore, if the voltage value of the connection point voltage Vx after the start of the self-diagnosis is the reference value, the control circuit 52 has no deterioration or failure of the detection resistor Rd, and the insulation resistance drop detector 50 operates normally. It is determined that

  On the other hand, when it is detected that the voltage value of the connection point voltage Vx after the start of the self-diagnosis is different from the reference value, that is, lower than the reference value, the control circuit 52 causes deterioration or failure of the detection resistor Rd. It is determined that the insulation resistance drop detector 50 is not operating normally.

  After the above determination, the control circuit 52 controls the field effect transistor Q to be turned off from on by outputting a control signal S2 that changes from high level to low level. As a result, the self-diagnosis resistor Rs connected to the connection point between the detection resistor Rd and the coupling capacitor Co is disconnected, and the self-diagnosis operation ends.

  In this way, the insulation resistance drop detector 50 can detect the deterioration or failure of the component, that is, the detection resistor Rd, during the self-diagnosis operation.

  In the above description, the field effect transistor Q is controlled to be turned on from off by applying the control signal S2 that is low level during normal operation and high level during self-diagnosis from the control circuit 52. That is, the field effect transistor Q used as a switching element is controlled to operate in a saturation region where the drain current is constant when the transistor is turned on.

  However, by adjusting the level of the control signal S2 when the control signal S2 that is at a high level during the self-diagnosis operation is applied to the field effect transistor Q, the drain current becomes a function of the drain-source voltage. It can also be controlled to operate in the saturation region. In this case, the field effect transistor Q can be used as a variable resistor that can vary the drain-source resistance in accordance with the level of the control signal S2 applied to the gate.

  That is, the field effect transistor Q is turned off by applying a low level control signal S2 from the control circuit 52 to the gate of the field effect transistor Q at the time of the insulation resistance decrease detection operation (normal time). A high level control signal S2 is applied from 52, the drain current is limited, and it acts as an apparent variable resistance element. The apparent resistance value of the variable resistance element can be varied according to the level adjustment of the high level control signal from the control circuit 52. Alternatively, the control circuit 52 applies a control signal in which a continuous pulse wave is superimposed on a high portion of a signal that is at a low level and becomes a high level at the time of self-diagnosis at the time of an insulation resistance decrease detection operation (normal time) to the gate and is constant The apparent resistance value of the variable resistance element may be varied by apparently controlling the average value of the drain current per unit time with the pulse width of the period continuous pulse wave.

  Therefore, in this case, a series connection resistance of a self-diagnosis resistor Rs and a field effect transistor Q is connected to the connection point of the detection resistor Rd and the coupling capacitor Co (can be regarded as a substantial self-diagnosis resistor). Is connected. As a result, the connection point voltage Vx is equal to the parallel combined resistance value of the series resistance value of the resistance by the self-diagnosis resistor Rs and the field effect transistor Q (substantially the resistance value of the self-diagnosis resistor) and the resistance value of the insulation resistance Ri. The voltage is divided by the resistance value of the detection resistor Rd.

  For example, when the resistance by the field effect transistor Q is controlled to be 100 kΩ, during the self-diagnosis, in addition to the resistance value 200 kΩ of the self-diagnosis resistor Rs, a total combined resistance for self-diagnosis is 300 kΩ. This is connected to the connection point between the detection resistor Rd and the coupling capacitor Co.

  Even in such a case, since the resistance value of the resistor by the field effect transistor Q can be set in advance, the control circuit 52 can detect the component part, that is, the detection by detecting the connection point voltage Vx after the start of the self-diagnosis. It is possible to detect the deterioration or failure of the resistor Rd, and thus it is possible to diagnose whether or not the insulation resistance lowering detector 50 is operating normally.

  FIG. 2 is a graph showing the relationship between the combined resistance value (kΩ) and the output peak value (V) of the low-pass filter 53 during self-diagnosis. A curve A indicates when the detection resistor Rd is normal, and a curve B indicates when the resistance increases due to deterioration or failure of the detection resistor Rd. In FIG. 2, the combined resistance value (kΩ) at the time of self-diagnosis on the horizontal axis was sequentially replaced with a self-diagnosis resistor Rs having a resistance value of 200 kΩ, 300 kΩ, 400 kΩ, 500 kΩ, 600 kΩ, 700 kΩ, or 800 kΩ. The series combined resistance (substantial self-diagnostic resistance) of the case and the resistance when the self-diagnosis resistor Rs and the field-effect transistor Q function as a variable resistance element have a resistance value of 200 kΩ to 800 kΩ. It means both when variable.

  From FIG. 2, the control circuit 52 detects based on the decrease in the output peak value (V) in the curve (B) with respect to the output peak value (V) in the curve A at one point of self-diagnosis resistance value (kΩ). It is possible to detect deterioration or failure of the resistor Rd.

  In FIG. 2, a curve C indicates characteristics when a decrease (ground fault) in the insulation resistance Ri occurs during self-diagnosis. When the insulation resistance Ri is lowered (ground fault), the output peak value of the low-pass filter 53 becomes almost zero. Therefore, at the time of self-diagnosis, this almost zero output peak value is due to the drop (ground fault) of the insulation resistance Ri. It is impossible to distinguish whether the detection resistor Rd is caused by deterioration or failure.

  Therefore, when it is detected that the output peak value of the low-pass filter 52 is almost zero, the control circuit 52 subsequently outputs the control signal S3 that becomes a high level, whereby the switches SW1 and SW2 are turned on. Control from on to off. Thereby, the insulation resistance lowering detector 50 is separated from the DC power supply system including the battery group B and the bus bar, and is not affected by the lowering of the insulation resistance Ri (ground fault).

  In this state, the control circuit 52 detects the output peak value of the low-pass filter 53 again, and if the detected output peak value has increased from a substantially zero value, the detection resistor Rd is degraded or malfunctioned. Can be determined. Further, if the detected output peak value is still almost zero, it can be determined that any of the components of the insulation resistance drop detector 50 has failed.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to this, and various modifications and applications are possible.

  For example, in the above-described embodiment, detection of deterioration or failure of the detection resistor Rd is performed on the output peak value of the low-pass filter 53 before the start of self-diagnosis and after the start of self-diagnosis with respect to the combined resistance value at a certain point of self-diagnosis. However, instead of this, the control circuit 52 detects the change in the output peak value of the low-pass filter 53 with respect to the combined resistance value during two or more self-diagnosis (for example, the rate of change). It is also possible to detect deterioration or failure of the resistor Rd. For example, the control circuit 52 uses the field-effect transistor Q as a variable resistor, changes the combined resistance value for substantial self-diagnosis under the control of the control signal S3, and changes the connection point voltage Vx in accordance with this change. The rate is compared with the normal change rate (reference change rate) of the detection resistor Rd. When the control circuit 52 detects that the change rate of the connection point voltage Vx according to the variable is different from the reference change rate, the control circuit 52 determines that the detection resistor Rd is deteriorated or malfunctions.

  Further, as another embodiment, the control circuit 52 is configured so that the self-diagnosis resistor Rs is deleted and the field effect transistor Q is turned off when a decrease in insulation resistance is detected and functions as a self-diagnosis resistor during a self-diagnosis operation. It may be controlled by the control signal S2. Also in this case, if the voltage value of the connection point voltage Vx after the start of the self-diagnosis is the reference value, the control circuit 52 has no deterioration or failure of the detection resistor Rd, and the insulation resistance lowering detector 50 operates normally. It is determined that it is operating. On the other hand, when it is detected that the voltage value of the connection point voltage Vx after the start of the self-diagnosis is different from the reference value, that is, lower than the reference value, the control circuit 52 causes deterioration or failure of the detection resistor Rd. Therefore, it can be determined that the insulation resistance lowering detector 50 is not operating normally.

  Further, as another embodiment, the control circuit is configured so that the self-diagnosis resistor Rs is deleted, the field-effect transistor Q is turned off when a decrease in insulation resistance is detected, and the self-diagnosis operation functions as a variable resistor for self-diagnosis. It may be controlled by a control signal S2 from 52. Also in this case, the control circuit 52 varies the resistance value of the field effect transistor Q functioning as a variable resistor under the control of the control signal S3, and changes the connection point voltage Vx in accordance with this variable. Compare with the normal change rate (reference change rate). When the control circuit 52 detects that the change rate of the connection point voltage Vx according to the variable is different from the reference change rate, the control circuit 52 can determine that the detection resistor Rd has deteriorated or failed.

  Further, according to the above-described embodiment, the control circuit 52 is configured by a microcomputer, but may be configured by, for example, a comparator.

  Furthermore, the present invention can be applied to the case where the capacitor Cf of the low-pass filter 53 is deteriorated and its leakage current is increased and the output peak value is lowered, in addition to the detection of the detection resistor Rd or the failure.

  In addition, the switch element configured by the field effect transistor Q or the like is not limited to a semiconductor device element, and includes a mechanical switch or a switch circuit having the same function that functions as the switch and variable resistance element described above.

It is a circuit diagram which shows embodiment of the insulation resistance fall detector which implemented the self-diagnosis method of this invention. 2 is a graph showing the relationship between the combined resistance value and the output peak value of the low-pass filter during self-diagnosis in the insulation resistance drop detector of FIG. It is a circuit diagram which shows an example of the conventional ground fault detection circuit. FIG. 4 is a waveform diagram for explaining the operation of the ground fault detection circuit of FIG. 3.

Explanation of symbols

50 Insulation resistance drop detector 51 Pulse oscillation circuit (pulse signal generating means)
52 Control circuit (decrease detection means, control means, variable means and determination means)
53 Low-pass filter 54 Waveform shaping circuit 55 Self-diagnosis circuit B Battery group Co coupling capacitor E Car body Ri Insulation resistance Rd Detection resistance Rs Self-diagnosis resistance Q Field effect transistor (switch element)
SW1 switch SW2 switch

Claims (8)

An insulation resistance decrease detector for detecting a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system, and generating a pulse signal for outputting a pulse signal means, said pulse signal the pulse signal from the generating means detecting resistor and is applied to the DC power supply system via a coupling capacitor, the insulation resistance drop detection operation, the connection point of the coupling capacitor and the detecting resistor A self-diagnosis method for an insulation resistance lowering detector comprising a lowering detecting means for detecting a lowering of the insulating resistance according to a value of a connection point voltage appearing in
During self-diagnosis, connect a self-diagnosis resistor between the connection point of the detection resistor and the coupling capacitor and the ground,
When it is detected that a value of a connection point voltage appearing at a connection point between the detection resistor and the coupling capacitor is a value different from a reference value, it is determined that the detection resistor is deteriorated or failed. Self-diagnosis method for insulation resistance drop detector. An insulation resistance decrease detector for detecting a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system, and generating a pulse signal for outputting a pulse signal means, said pulse signal the pulse signal from the generating means detecting resistor and is applied to the DC power supply system via a coupling capacitor, the insulation resistance drop detection operation, the connection point of the coupling capacitor and the detecting resistor A self-diagnosis method for an insulation resistance lowering detector comprising a lowering detecting means for detecting a lowering of the insulating resistance according to a value of a connection point voltage appearing in
During self-diagnosis, connect a self-diagnosis resistor between the connection point of the detection resistor and the coupling capacitor and the ground,
Variable the resistance value of the self-diagnosis resistor;
The detection is performed when it is detected that a change rate of a connection point voltage appearing at a connection point of the detection resistor and the coupling capacitor is different from a reference change rate according to a change in a resistance value of the self-diagnosis resistor. A self-diagnosis method for an insulation resistance lowering detector, characterized in that it is determined that the resistance has deteriorated or failed. An insulation resistance decrease detector for detecting a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system, and generating a pulse signal for outputting a pulse signal means, said pulse signal the pulse signal from the generating means detecting resistor and is applied to the DC power supply system via a coupling capacitor, the insulation resistance drop detection operation, the connection point of the coupling capacitor and the detecting resistor Insulation resistance decrease detector comprising a decrease detection means for detecting a decrease in the insulation resistance according to the value of the connection point voltage appearing in
A self-diagnostic resistor and a switch element connected in series between a connection point of the detection resistor and the coupling capacitor and the ground;
Control means for controlling the switch element to be turned off during an insulation resistance drop detecting operation and turned on during a self-diagnosis operation;
When it is detected that the value of the connection point voltage appearing at the connection point of the detection resistor and the coupling capacitor is different from a reference value when the switch element is turned on, the detection resistor An insulation resistance lowering detector, further comprising a determination means for determining deterioration or failure. An insulation resistance decrease detector for detecting a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system, and generating a pulse signal for outputting a pulse signal means, said pulse signal the pulse signal from the generating means detecting resistor and is applied to the DC power supply system via a coupling capacitor, the insulation resistance drop detection operation, the connection point of the coupling capacitor and the detecting resistor Insulation resistance decrease detector comprising a decrease detection means for detecting a decrease in the insulation resistance according to the value of the connection point voltage appearing in
A self-diagnostic resistor and a switch element connected in series between a connection point of the detection resistor and the coupling capacitor and the ground;
Control means for controlling the switch element to be turned off during an insulation resistance drop detecting operation and turned on during a self-diagnosis operation;
Variable means for varying the resistance value of the self-diagnosis resistor;
When the switch element is turned on, the change rate of the connection point voltage that appears at the connection point of the detection resistor and the coupling capacitor according to the variable resistance value of the self-diagnosis resistor is different from the reference change rate. An insulation resistance lowering detector, further comprising: a determination unit that determines that the detection resistor has deteriorated or failed when the detection resistance is detected. An insulation resistance decrease detector for detecting a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system, and generating a pulse signal for outputting a pulse signal means, said pulse signal the pulse signal from the generating means detecting resistor and is applied to the DC power supply system via a coupling capacitor, the insulation resistance drop detection operation, the connection point of the coupling capacitor and the detecting resistor Insulation resistance decrease detector comprising a decrease detection means for detecting a decrease in the insulation resistance according to the value of the connection point voltage appearing in
A self-diagnostic resistor and a switch element connected in series between a connection point of the detection resistor and the coupling capacitor and the ground;
Control means for controlling the switch element to be turned off during an insulation resistance drop detection operation and to function as a variable resistor during a self-diagnosis operation;
Judgment that the detection resistor is deteriorated or failed when it is detected that the change rate of the connection point voltage that appears at the connection point of the detection resistor and the coupling capacitor during the self-diagnosis operation is different from the reference change rate. And a means for detecting a decrease in insulation resistance. An insulation resistance decrease detector for detecting a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system, and generating a pulse signal for outputting a pulse signal means, said pulse signal the pulse signal from the generating means detecting resistor and is applied to the DC power supply system via a coupling capacitor, the insulation resistance drop detection operation, the connection point of the coupling capacitor and the detecting resistor Insulation resistance decrease detector comprising a decrease detection means for detecting a decrease in the insulation resistance according to the value of the connection point voltage appearing in
A switch element connected between a connection point of the detection resistor and the coupling capacitor and the ground;
Control means for controlling the switch element to be turned off during an insulation resistance drop detection operation and to function as a variable resistor during a self-diagnosis operation;
Judgment that the detection resistor is deteriorated or failed when it is detected that the change rate of the connection point voltage that appears at the connection point of the detection resistor and the coupling capacitor during the self-diagnosis operation is different from the reference change rate. And a means for detecting a decrease in insulation resistance. An insulation resistance decrease detector for detecting a decrease in insulation resistance in a vehicle including a DC power supply system electrically insulated from a vehicle body and an AC circuit connected to the DC power supply system, and generating a pulse signal for outputting a pulse signal means, said pulse signal the pulse signal from the generating means detecting resistor and is applied to the DC power supply system via a coupling capacitor, the insulation resistance drop detection operation, the connection point of the coupling capacitor and the detecting resistor Insulation resistance decrease detector comprising a decrease detection means for detecting a decrease in the insulation resistance according to the value of the connection point voltage appearing in
A field effect transistor connected between a connection point of the detection resistor and the coupling capacitor and the ground;
Control means for controlling the field effect transistor to be turned off during an insulation resistance drop detection operation and to function as a variable resistor during a self-diagnosis operation;
Judgment that the detection resistor is deteriorated or failed when it is detected that the change rate of the connection point voltage that appears at the connection point of the detection resistor and the coupling capacitor during the self-diagnosis operation is different from the reference change rate. And a means for detecting a decrease in insulation resistance. Connected between the DC power supply system and the bus connecting the DC power supply system to the AC circuit, controlled by the control means, turned on during the insulation resistance lowering detection operation and turned off during the self-diagnosis operation The insulation resistance lowering detector according to any one of claims 3 to 7, further comprising a switch to be operated.

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