JPH11332001A - Abnormality sensing device and method for dc-to-dc converter, and vehicle driving system having abnormality sensing function thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely sense the generation of the abnormality of a DC/DC converter, when the output voltage of a DC/DC converter is increased. SOLUTION: A DC/DC converter assembly 20 has a plurality of DC/DC converter modules 22a, 22b connected in parallel with each other. The rate of change of the output voltage of the DC/DC converter assembly 20 when all the converter modules 22a, 22b are normal is different from one when an abnormality is generated in one of the converter modules 22a, 22b. Therefore, when the rate of change of its detected output voltage value is different from the one in the normal state, a system ECU 32 decides that an abnormality has been generated in it, based on the output of a voltage sensor 34. The rate of change of the output voltage is represented, e.g. by its voltage gradient with respect to time axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for detecting an abnormality of a DC / DC converter. This abnormality detection device is suitably applied to, for example, a vehicle drive system that generates a propulsion force of a vehicle by an engine and an assist motor.

[0002]

2. Description of the Related Art Conventionally, electric vehicles have attracted attention from the viewpoint of low pollution. One type of electric vehicle is a vehicle with a wheel motor. FIG. 14 shows an example of the configuration of a vehicle with a wheel motor. The front wheel 102 is driven by the output of the engine 100. The auxiliary battery 104 is charged by an alternator driven by an engine output, and supplies electric power to an engine ignition system and the like. In addition, the DC voltage of auxiliary battery 104 is boosted by DC / DC converter 106, and power is temporarily stored in capacitor 108 on the boost side. And
Electric power is supplied from the capacitor 108 to the left and right wheel motors 110 via the inverter. Wheel motor 1
The stator 10 is fixed on the vehicle body side and the rotor is fixed on the wheel side. The output of the wheel motor 110 drives the rear wheel 112.

In the system shown in FIG. 14, the engine 100 generates main propulsion of the vehicle, and the wheel motor 110 generates assist propulsion. For example, even in a situation where the friction coefficient of the road surface is low and the front wheel 102 easily slips, such as on an uphill road on a snowy road, the vehicle stably travels by driving the rear wheel 112 using the assist propulsive force. When the vehicle decelerates, the wheel motor 110
The power obtained by the regenerative braking is stored in the capacitor 108, and the wheel motor 110 is driven using this power. In this way, the athletic performance of the vehicle is improved,
Energy efficiency can be improved. Further, by directly attaching the motor to the wheel, (1) transmission system components such as a drive shaft and a space therefor can be omitted, and transmission loss is reduced; (2) the driving force of one motor is applied to the left and right wheels. Rather than distributing, the left and right wheels can be independently driven, so that the left and right driving forces can be controlled independently, which results in high athletic performance; .

[0004]

In the vehicle drive system as shown in FIG. 14, when an abnormality occurs in the DC / DC converter, the normal operation of the system becomes difficult. So D
It is necessary to detect that an abnormality has occurred in the C / DC converter, and to appropriately deal with the occurrence of the abnormality. The converter abnormality is, for example, an internal disconnection, and is, for example, a failure of those elements when a transistor or a diode is incorporated.

As a reference technology, Japanese Patent Application Laid-Open No. 9-284994
In the overvoltage protection circuit described in Japanese Patent Application Laid-Open Publication No. H11-260, it has been proposed to detect a converter abnormality by comparing the magnitude of the output voltage of the DC / DC converter with a predetermined reference voltage.

[0006] The above publication presupposes that a DC / DC converter is provided in a computer or the like and used to constantly obtain a constant output voltage. If the converter is normal, it should continue to output a constant voltage. Therefore, it is possible to easily determine whether or not a converter abnormality has occurred simply by monitoring the magnitude of the detected output voltage.

However, in a system as shown in FIG. 14, a DC / DC converter is used for charging a capacitor. Charging is performed at the start of operation or after the power of the capacitor is consumed for driving the motor. The charging is started by the activation of the DC / DC converter, and the output voltage rises. The output voltage of the converter is equal to the voltage across the capacitor, and when the target output voltage is obtained, the converter is stopped. When using a converter for such a purpose,
The output voltage of the converter is not constant but changes.
For this reason, it is difficult to detect an abnormality of the converter even if only the magnitude of the output voltage is monitored as in the related art. Therefore, it is desired that the occurrence of converter abnormality can be reliably detected even in such a case.

Further, in the system as shown in FIG. 14, it is desirable that after the power of the capacitor is consumed for driving the motor, the capacitor is quickly charged in preparation for the next motor driving. For that purpose, it is effective to connect a plurality of DC / DC converters in parallel and function as one DC / DC converter as a whole. Hereinafter, each DC / DC converter connected in parallel in such a configuration is referred to as a “DC / DC converter module”. However, when a part of the plurality of converter modules connected in parallel fails, power conversion is possible but the power conversion capability is reduced. Therefore, it is not possible to determine whether or not a converter abnormality has occurred by only looking at the magnitude of the output voltage. Of course, it is conceivable to attach a sensor for abnormality detection to each converter module, but there are disadvantages such as a complicated configuration and an increase in cost.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an abnormality detection device and an abnormality detection method capable of reliably detecting occurrence of an abnormality in a converter with a simple configuration.

[0010] Another object of the present invention is to provide a DC / DC converter.
An object of the present invention is to provide an abnormality detection device and an abnormality detection method that can reliably detect converter abnormality even when a plurality of DC / DC converter modules are provided in parallel with the DC converter.

Still another object of the present invention is to provide a plurality of DC / DC converters.
An object of the present invention is to provide an abnormality detection device and an abnormality detection method that can identify which converter module has an abnormality when DC converter modules are provided in parallel.

Still another object of the present invention is to provide a vehicle drive system having the above-described suitable converter abnormality detecting function.

[0013]

(1) In order to achieve the above object, the present invention relates to a DC / DC converter abnormality detecting apparatus for converting an input DC voltage into a different DC voltage and outputting the converted DC voltage. Voltage detecting means for detecting an output voltage of the DC / DC converter; and abnormality determining means for determining whether or not a converter abnormality has occurred based on the detected value of the output voltage. When the speed of change of the detected value of the output voltage is different from the speed of change of the output voltage in the converter normal state, it is determined that a converter abnormality has occurred.

According to the present invention, a converter abnormality is detected by utilizing the speed of change of the output voltage. The output voltage changes depending on whether the converter is normal or abnormal.
The speed of voltage change is different. Therefore, it can be determined whether or not a converter abnormality has occurred, based on whether or not the output voltage has changed at a different speed from the normal state of the converter.

As described above, according to the present invention, for example, DC
Even when the converter abnormality is not known only by the magnitude of the output voltage, such as when using a / DC converter to charge a capacitor, the converter abnormality can be reliably detected by utilizing the speed of the output voltage change. Becomes possible.

The present invention is suitably applied to a case where the DC / DC converter has a plurality of DC / DC converter modules. However, the present invention is not limited to such a configuration, and the present invention can be similarly applied to a case where a DC / DC converter is provided alone.

Further, the abnormality detecting means of the present invention described above includes, for example, one of the following (2) to (4) in order to determine whether or not the speed of change of the output voltage is appropriate. It is preferred to have a strategic configuration.

(2) In one aspect of the present invention, the abnormality determining means includes a slope calculating means for calculating a slope of the output voltage detection value with respect to a time axis, and a reference corresponding to a converter normal state based on the output voltage detection value. And a reference slope obtaining means for determining the voltage slope of the converter, and determines whether a converter abnormality has occurred by comparing the calculated voltage slope with the reference voltage slope. The slope of the voltage with respect to the time axis corresponds to the voltage change speed.

(3) In another aspect, the abnormality determining means includes a voltage change calculating means for obtaining a change amount of an output voltage detection value before and after a predetermined determination period, and an output voltage at the start of the determination period. And a reference voltage change obtaining means for obtaining a reference output voltage change amount before and after a determination period corresponding to a converter normal state based on the reference voltage, and comparing the change amount of the output voltage detection value with the reference output voltage change amount. Thus, it is determined whether or not a converter abnormality has occurred. The amount of voltage change before and after the determination period corresponds to the average voltage change speed (slope) during the determination period.

(4) In another aspect, the abnormality determining means determines a reference output voltage at the end of the determination period corresponding to the converter normal state based on the output voltage at the start of the predetermined determination period. Including the reference voltage obtaining means to be obtained,
It is determined whether or not a converter abnormality has occurred by comparing the detected value of the output voltage at the end of the determination period with the reference output voltage. In this aspect, the output voltage itself at the end of the determination period is used for abnormality determination,
The principle of the determination is substantially the same as the above (3).

(5) In a preferred aspect of the present invention, the DC / DC converter includes a plurality of DC / DC converter modules provided in parallel between an input terminal and an output terminal of the converter, The output voltage of the DC / DC converter detected by the means is equal to the plurality of DC / DC converters.
A total output voltage of the DC / DC converter module, and the abnormality determining means outputs a plurality of DC / DC signals when the total output voltage changes at a speed different from a speed at which all the DC / DC converter modules are normal. It is determined that an abnormality has occurred in any of the converter modules.

In this embodiment, a plurality of DC / DC converter modules are connected in parallel. Each DC / DC converter module can function as a normal DC / DC converter. The voltage detection means detects a total output voltage after all the converter modules have been collected. The speed of change of the total output voltage differs between a case where all converter modules are normal and a case where some converter modules are abnormal. Therefore, the occurrence of converter abnormality can be detected by utilizing the speed of change of the total output voltage. In the case of monitoring only the magnitude of the output voltage as in the related art, power conversion is performed even if an abnormality occurs in some converter modules, so that it has been difficult to reliably detect the converter abnormality. According to the present invention, as described above,
It is also possible to reliably detect that an abnormality has occurred in some converter modules. Since it is not necessary to separately provide a voltage sensor for each converter module, the structure is simple and the cost can be reduced.

(6) In another preferred aspect of the present invention, the DC / DC converter includes a plurality of DC / DC converters provided in parallel between an input terminal and an output terminal of the converter.
An output voltage of the DC / DC converter which includes a DC converter module and which is detected by the voltage detection means is a total output voltage of the plurality of DC / DC converter modules, and controls the plurality of DC / DC converter modules by time division control. And time-division drive control means for sequentially and individually driving the DC / D converters.
When driving the C converter module, if the total output voltage changes at a speed different from the speed in the converter normal state, it is determined that an abnormality has occurred in the DC / DC converter module driven at that time.

In this embodiment, a plurality of DC / DC converter modules are sequentially driven individually by time division control. When each DC / DC converter module is driven, it is determined whether or not a converter abnormality has occurred based on a change in the total output voltage. When it is determined that an abnormality has occurred, an abnormality has occurred in the DC / DC converter module driven at that time. Therefore, it is possible to specify which converter module has an abnormality. As a result, more appropriate countermeasures can be taken for converter abnormalities, and work such as converter repair can be performed quickly and easily.

(7) Another aspect of the present invention is a DC / DC converter that converts an input DC voltage into a different DC voltage and outputs the converted DC voltage.
A converter abnormality detection method, characterized in that it is determined that a converter abnormality has occurred when an output voltage of the DC / DC converter changes at a different speed from a converter normal state. According to this aspect, the above-described effect of the present invention can be obtained in the form of an abnormality detection method.

(8) According to another aspect of the present invention, an engine for generating a main propulsion force of a vehicle, an assist motor for generating an assist propulsion force for the vehicle, and electric power supplied from auxiliary power storage means are supplied to the assist motor. A DC / DC converter for boost-converting power to a required voltage, a motor power storage means for temporarily storing power boosted by the DC / DC converter, and supplying the stored power to the assist motor;
A voltage detecting means for detecting an output voltage of the DC / DC converter;
An abnormality which determines that an abnormality has occurred in the DC / DC converter when the output voltage changes at a speed different from the speed in the converter normal state when the DC / DC converter is activated and the motor power storage means is charged. Determining means;
It is characterized by including.

According to this aspect, the vehicle drive system includes:
It is possible to reliably detect that an abnormality has occurred in the DC / DC converter for charging the motor power storage unit at an early stage when the converter is started, and to take appropriate countermeasures. For example, use of the assist motor is prohibited. In the case where the DC / DC converter is composed of a plurality of unit converters and some of the unit converters are normal, the available unit converters are used,
Subsequently, the assist motor can be operated.

For example, the assist motor is a wheel motor attached to a wheel, the auxiliary power storage means is an auxiliary battery, and the motor power storage means is a capacitor or a capacitor. Preferably, each configuration of the abnormality determination means of the present invention is appropriately incorporated in a control device that controls the DC / DC converter.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] Hereinafter, a preferred embodiment of the present invention (hereinafter, referred to as an embodiment) will be described with reference to the drawings. FIG. 1 shows the configuration of the vehicle drive system of the present embodiment. The abnormality detection device of the present invention is provided in this system. The engine 10 is an internal combustion engine, which is mounted on a front portion of a vehicle body, and includes a transmission 1
2 and to the front wheel 16 via the axle 14. The front wheel 16 is driven by the output of the engine 10.

The auxiliary battery 18 having a voltage of 12 V is charged by the power generated by the alternator 19 driven by the output of the engine 10. The auxiliary battery 18 supplies power to the engine ignition system and other auxiliary machines. A DC voltage is input from the auxiliary battery 18 to the DC / DC converter assembly 20, and the converter boosts the voltage. D
The C / DC converter assembly 20 includes two DC / DC converter modules 22a and 22b connected in parallel.
Having. Here, in the present embodiment, the DC / DC converter assembly 20 corresponds to the DC / DC converter of the present invention. Each converter module may have a known configuration. Hereinafter, the DC / DC converter assembly 20 or the DC / DC converter module 2
2a and 22b are simply called converters.

The DC voltage output from converter assembly 20 is applied to capacitor 24, which charges capacitor 24. The capacitor 24 is provided for temporarily storing electric power for driving the wheel motor 28. It is also preferable to provide an electric field capacitor instead of the capacitor 24. The electric power stored in the capacitor 24 is supplied to the left and right wheel motors 28 via the left and right inverters 26. Inverter 26 has a plurality of switching elements, and converts DC current sent from capacitor 24 to AC current. Wheel motor 28
Is a three-phase AC type PM synchronous motor, for example. The stator of the wheel motor 28 is fixed to the vehicle, and the rotor is fixed to the rear wheel 30. Therefore, the output of the wheel motor 28 drives the rear wheel 30.

The system ECU 32 controls the wheel motor 2
8 controls the power assist system of FIG. The system ECU 32 operates based on various components including the wheel motor 28, the auxiliary battery 18 and the engine 10, and signals input from sensors provided on those components. The system ECU 32 is a DC
A control signal is output to the / DC converter assembly 20 to perform a boosting operation. Here, the system ECU 32
Is configured to individually output a control signal to each converter module constituting the converter assembly 20 and to operate individually. Therefore, it is also possible to activate only one converter and perform power conversion.

The system ECU 32 generates and outputs a signal for controlling the switching operation of the inverter 26. A switching signal for generating an alternating current for generating a desired torque in the wheel motor 28 is generated. When the vehicle is decelerating, a switching signal for causing the wheel motor 28 to perform regenerative braking is generated. The electric power generated by the regenerative braking charges the capacitor 24. The engine 10 is an engine EC (not shown).
Although controlled by U, this engine ECU may also be integrated with the system ECU 32.

Further, the system ECU 32 functions as the abnormality determining means of the present invention. On the output side of the DC / DC converter assembly 20, a voltage sensor 34 is provided. The detection signal of this voltage sensor 34 is the system EC
The input voltage is input to U32, and the output voltage CO_VDET of the converter assembly 20 is obtained by the ECU 32. The system ECU 32 detects a converter abnormality using this output voltage, as described later. The output voltage is 2
This is a voltage (combined output voltage) at a portion after the two converter modules 22a and 22b are gathered. The output voltage is also a voltage across the capacitor 24.

FIG. 2 shows the overall control of the vehicle drive system of the present embodiment. When an ignition switch (not shown) is turned on (S100), the system E
The CU 32 is started (S101), and engine start control is performed (S102). When the engine starts, an assist system, that is, a system related to the wheel motor 28 is started (S103), and travel control is performed (S104). During traveling control, the engine 10 generates main propulsion of the vehicle, and the wheel motor 28 generates assist propulsion. In a situation where the road surface is slippery or the like, by using the driving force of the rear wheel 30,
The athletic performance of the vehicle is improved. Then, it is determined whether or not the ignition switch has been turned off (S10).
5). If the ignition is not turned off, the traveling control is continued, and if the ignition is turned off, the entire process ends.

In the process of FIG. 2, the DC / DC converter is first driven in an assist system start-up step in S103. It is necessary to store enough electric energy in the capacitor 24 to drive the wheel motor 28.
Therefore, charging is performed until the converter output voltage CO_VDET (= voltage across the capacitor) reaches a predetermined target value. As described above, the converter output voltage is detected by the voltage sensor 34. Also, during running control, after the power of the capacitor 24 is consumed for driving the motor, it is necessary to charge the capacitor 24 in preparation for driving the wheel motor 26 next time. Also at this time, DC / DC
The converter is driven. Also in this case, the converter is driven until the converter output voltage CO_VDET reaches the target. The reason why the two converter modules 22a and 22b are provided in the present embodiment is to charge the capacitor 24 in a short time.

Next, a description will be given of the converter abnormality detection of the present embodiment. In the present embodiment, since the DC / DC converter is used for charging the capacitor 24, the output voltage increases with the passage of time after the start of the converter. FIG. 3 shows voltage rise curves when two converter modules are driven and when only one converter module is driven. As is clear from FIG. 3, even if one of the two converter modules 22a and 22b fails, the output voltage increases with the passage of time. Therefore, even if only the magnitude of the output voltage is monitored, it is not known whether a converter abnormality has occurred.

However, as shown in FIG. 3, the speed at which the output voltage increases depends on the number of normal converter modules. Therefore, the converter abnormality can be detected using the speed of the increase in the output voltage. That is, by comparing the detected output voltage change with the reference voltage change in the converter normal state, it can be determined whether or not a converter abnormality has occurred. In the present embodiment, specifically, a converter abnormality is detected by one of the following abnormality determination processes 1 to 3.

[Abnormality Detection Process 1] Here, the slope of the output voltage with respect to the time axis (voltage change speed) is used as a parameter indicating the speed of change of the output voltage. As is clear from FIG. 3, as the time elapses, the output voltage increases and the voltage gradient decreases. The output voltage and the voltage gradient correspond one to one. Then, even if the magnitude of the output voltage is the same, the voltage gradient differs according to the number of normal converter modules. Therefore, a voltage gradient map (a table or the like may be used, the same applies hereinafter) representing the relationship between the output voltage and the voltage gradient when the two converter modules are normal is created. This map shows the allowable range of the voltage gradient. FIG. 4 shows an example of the voltage gradient map.
This map is stored in the system ECU 32. The system ECU 32 outputs the detected output voltage CO_VDE
A voltage gradient is determined from T, and if this gradient deviates from the allowable range indicated by the dotted line in FIG.

FIG. 5 is a flowchart showing an abnormality detection process using a voltage gradient. The system ECU 32
When starting up the converter (S200), the number of times of voltage measurement is set to N (S201). Then, the converter output voltage CO_VDET is input from the voltage sensor 34 (S202), and 1 is subtracted from the number of measurements N (S203).
Then, a timer process is performed to wait for a predetermined timer time to elapse (S204), and it is determined whether or not the number of measurements N has become zero (S205). If N = 0, S2
Return to 02. In this way, N voltage detection values are obtained every timer time.

Next, the system ECU 32 calculates the voltage gradient CO_ΔV from the N voltage detection values (S20).
6). Here, one voltage gradient is calculated by dividing the difference between the first and second voltage detection values obtained by the timer time. Similarly, the voltage gradient is calculated from the second and third data, the third and fourth data. When N-1 slope calculation values are obtained in this way, the average of these slopes is calculated. This average value is the final voltage gradient CO_
ΔV.

The system ECU 32 calculates a reference voltage gradient CO_ΔVBASE (S207). First,
An average of the N voltage detection values CO_VDET is calculated. Then, a voltage gradient CO_ΔVBASE corresponding to the average voltage value is obtained by referring to the voltage gradient map of FIG.

Next, a difference ΔCO between the voltage gradient CO_ΔV and the reference voltage gradient CO_ΔVBASE is calculated (S20).
8). Then, it is determined whether or not the inclination deviation ΔCO is outside the allowable range (S209). The permissible range is indicated by a dotted line in FIG. If the inclination deviation ΔCO is within the allowable range, it is considered that the two converter modules 22a and 22b are operating normally, and the abnormality detection processing ends. If the inclination deviation ΔCO is out of the allowable range, it is considered that an abnormality has occurred in at least one of the two converter modules 22a and 22b, and therefore, “abnormality processing”
Is performed (S210). The converter abnormality is, for example, an internal disconnection, and is, for example, a failure of those elements when a transistor or a diode is incorporated.
In the “abnormal process”, the output of the wheel motor 28 is limited. As a result, the power assist system using the wheel motor 28 can be continuously operated within a range that is possible in the current converter capacity reduction state.
In addition, an indicator at the driver's seat is displayed, thereby notifying the driver of the occurrence of an abnormality.

It should be noted that the above-described abnormality detection may be performed only when the converter is started when the assist system is started (S103 in FIG. 2). Also, it may be performed every time the converter is started during the traveling control.

With the above processing, occurrence of a converter abnormality can be reliably detected. In particular, even when two or more converters are provided in parallel as in the present embodiment, a converter abnormality can be detected.

Further, the above-described processing has an advantage that it is possible to determine whether or not a converter abnormality has occurred by using the voltage gradient, regardless of the state of the initial voltage at the start of the converter.

In the above process, the reference voltage gradient was obtained using a voltage gradient map created and stored in advance. On the other hand, the system ECU 32 may calculate the reference voltage gradient by calculation using an appropriate function. This applies to other detection processes described below.

[Abnormality detection processing 2] Abnormality detection processing 1 described above
In, a converter abnormality was detected using the voltage gradient.
In the abnormality detection process 2, a converter abnormality is detected using a difference (voltage change amount) between output voltages before and after a predetermined determination period. This voltage change amount corresponds to the average of the voltage change speed during the determination period. Therefore, detection processing 2
This is the same as the above-described detection processing 1 in that abnormality detection is performed based on the speed of voltage change.

Abnormality detection processing 2 with reference to FIGS.
The principle of will be described. 6 and 7 show rising curves of the output voltage CO_VDET when the converter is normal. After the converter starts at time T0, the output voltage rises. Here, the converter start time T0 is set as the judgment start time.

In the example of FIG. 6, the initial voltage V0 at the point of time T0 when the converter is started is zero. If the converter is normal,
After the elapse of the predetermined judgment period P (T1), the output voltage should reach V2, and the output voltage difference before and after the judgment period should be V2-V0. This voltage difference V2-V
0 is a reference voltage difference ΔVBASE. Time point T0 and time point T
The difference Δ of the output voltage CO_VDET actually detected at 1
Find V. The difference ΔV between the detected values is calculated by using the above-described reference voltage difference ΔV.
If the two are significantly different from BASE, it is determined that a converter abnormality has occurred.

In the example of FIG. 7, electric power remains in the capacitor 24 when the converter is started, and the initial voltage is not zero.
In such a case, the converter abnormality can be detected in the same manner as in the example of FIG. However, the reference voltage difference ΔVBASE needs to be different from the example of FIG.

As described above, since the amount of voltage change before and after the determination period P differs depending on the initial voltage V0, the reference voltage difference Δ
VBASE is also different. Therefore, a reference voltage difference map that associates the initial voltage V0 with the reference voltage difference ΔVBASE is created, and this map is stored in the system ECU 32. The system ECU 32 obtains the reference voltage difference ΔVBASE from the initial voltage V0 with reference to the reference voltage difference map. Then, it is determined whether or not a converter abnormality has occurred using the reference voltage difference ΔVBASE and the detected voltage value.

FIG. 8 shows the processing of the abnormality detection processing 2. When starting up the converter (S300), system ECU 32 inputs the converter output voltage from voltage sensor 34 (S301). The voltage detection value CO_VDET_1 input here corresponds to the above initial voltage V0. Next, the system ECU 32 performs a timer process and waits until a predetermined determination period P has elapsed (S302).
The converter output voltage CO_VDET_2 is input (S3
03).

Next, the system ECU 32 calculates the difference ΔV between the above two detected voltage values = (CO_VDET_2) − (CO
_VDET_1) is calculated (S304). Voltage difference ΔV
Is compared with a reference voltage difference ΔVBASE to determine whether ΔV is within an allowable range (S305). ΔVBASE is read from the reference voltage difference map as described above. The permissible range is indicated by a dotted line in FIGS. Voltage difference Δ
If V is not between (V3−V0) and (V1−V0), it is considered that an abnormality has occurred in at least one of the two converter modules 22a and 22b.
"Abnormal processing" is performed (S306). “Abnormal processing” is the same as in the first embodiment, and is motor output restriction and indicator lighting.

The abnormality detection processing 2 has been described above. In addition,
In the above processing, the determination start time, that is, the start time of the determination period P was the converter activation time. However, the determination start time may be an appropriate time after the start of the converter (the same applies to the detection processing 3).

[Abnormality Detection Process 3] Abnormality Detection Process 2
In the above, the converter abnormality is detected using the output voltage difference before and after the predetermined period. On the other hand, in the detection process 3, the output voltage detection value itself after the elapse of the predetermined period is compared with the reference output voltage. Although the specific contents of the processing are different, the principle of abnormality detection is the same as that of the detection processing 2. That is, FIG.
In FIG. 7 and FIG. 7, based on the initial voltage V0, the output voltage after the elapse of the determination period P when the converter is assumed to be normal is obtained and set as a reference output voltage. By comparing the reference output voltage with the actual output voltage detection value, it is determined whether or not a converter abnormality has occurred. In order to perform this detection process, a reference voltage map that associates the initial voltage with the reference output voltage is created and stored in the system ECU 32.

FIG. 9 shows the processing of the abnormality detection processing 3. When starting up the converter (S400), the system ECU 32 inputs the converter output voltage from the voltage sensor 34 (S401). The detected voltage value at this time is CO_VDET_1. Next, the system ECU 32
Performs a timer process and waits for a predetermined judgment period P to elapse (S402), and inputs the converter output voltage again (S403). The voltage detection value at this time is set to CO_VDE
Let it be T_2.

Next, the system ECU 32 refers to the reference voltage map stored in the memory and refers to the initial voltage CO.
A reference voltage CO_VBASE corresponding to _VDET_1 is obtained (S404). Further, the detected voltage CO_VD
The difference ΔVE between ET_2 and the reference voltage CO_VBASE is obtained (S405). It is determined whether or not voltage error ΔVE is within an allowable range (S406). If not, it is determined that a converter abnormality has occurred. The allowable range of ΔVE is indicated by a dotted line in FIGS. 6 and 7 ((V
3-V1) / 2). If a converter abnormality has occurred, “abnormality processing” is performed in the same manner as the abnormality determination processings 1 and 2 (S407). If no abnormality has occurred, the process ends.

In the above detection processing 3, since the voltage detection value itself after the elapse of the determination period is compared with the reference value, there is an advantage that the processing is simple. The detection process 3 is performed when the system is started in S103 in FIG. 2 and when the converter is started during the traveling control in S104. In particular, during traveling control, the system ECU 32 is subjected to a processing load for controlling the entire system. Therefore, it is desired to simplify the converter abnormality detection processing and reduce the processing time as much as possible. In this regard, the detection processing 3 is advantageous because the processing content is simple and the processing time is short.

[Embodiment 2] A preferred second embodiment of the present invention will now be described.
An embodiment will be described. In the second embodiment, a plurality of converter modules are sequentially and individually driven in a time-division manner, thereby identifying which converter module has an abnormality.

FIG. 10 shows a vehicle drive system according to the second embodiment. 10, the same reference numerals as in FIG. 1 denote the same components as in FIG. The system of FIG. 10 differs from the system of FIG.
The C converter assembly 20 includes three DC / DC converter modules 22a, 22b, 22c. These DC / DC converter modules 22
a, 22b and 22c are connected in parallel. Other configurations are the same as those in the first embodiment, and a description thereof will not be repeated.

FIG. 11 shows the principle of abnormality detection in the second embodiment. When starting up the DC / DC converter assembly 20, first, only the converter module 1 (22a) is driven from time T0 to time T1. The period from time T0 to time T1 corresponds to the determination period P of [Abnormality detection processing 2] in the first embodiment. Using the detected values of the output voltage CO_VDET at the time points T0 and T1,
Based on the principle of [abnormality detection processing 2], it is determined whether converter module 1 is abnormal.

Here, with respect to one converter module, a reference voltage difference map that associates the output voltage at the start of the determination with the reference voltage difference is created. With reference to this map, a reference voltage difference is determined from the output voltage at the start time T0 of the converter module. Then, the difference between the voltage detection values at time T1 and time T0 is compared with a reference voltage difference.

Next, only converter module 2 (22b) is driven from time T2 to time T3. And
[Abnormality detection processing 2] is also executed based on the voltage detection values at time T2 and time T3. Here, the reference voltage difference is obtained based on the output voltage V10 at the time T2. Similarly, only the converter module 3 (22c) is driven from time T4 to time T5,
Is determined to be abnormal.

As described in the first embodiment, the system ECU 32 outputs a control signal to each converter module constituting the converter assembly 20 individually.
It is configured to be able to operate individually. Utilizing this function, the system ECU 32 functions as a time division drive control unit of the present invention, and divides the drive of the converter in a time series as described above.

As shown in FIG. 12, the above-described abnormality detection processing can be similarly executed even when electric energy remains in capacitor 24 before the start of the converter. The reference voltage difference may be obtained based on the voltage at the time of starting each converter module.

FIG. 13 shows an abnormality detection process according to the second embodiment. The system ECU 32 first activates the converter module 1 (S500), and inputs a converter output voltage from the voltage sensor 34 (S501). The voltage detection value at this time is defined as CO_VDET1_1. Next, the system ECU 32 performs a timer process, waits for a predetermined determination period P to elapse (S502), and inputs the converter output voltage again (S503). The voltage detection value at this time is defined as CO_VDET1_2. The system ECU 32
The converter module 1 is stopped (S504), and the difference ΔV1 between the detected voltage values before and after the determination period is equal to (CO_VDET1_).
2)-(CO_VDET1_1) is calculated (S50)
5). The detected voltage difference ΔV1 is used as a reference voltage difference ΔVBAS
It is compared with E1 to determine whether ΔV is within the allowable range (S506). ΔVBASE1 is obtained by referring to the reference voltage difference map as described above. That is, FIG.
The reference voltage difference corresponding to CO_VDET1_1 obtained in S301 is read from the map.

If ΔV1 is not within the allowable range, “abnormal processing” is performed (S507). Here, the occurrence of an abnormality is recorded in the memory of the system ECU 32 in order to take a specific countermeasure after waiting for the abnormality determination result of another converter.

After the abnormal processing in S507, or in S5
When it is determined that there is no abnormality in 06, the process proceeds to S508, and the system ECU 32 activates the converter module 2. The period from S504 to S508 corresponds to the period from time T1 to time T2 in FIGS. 10 and 11, and the output voltage does not increase during this period.

After starting converter module 2 in S508, S501 to S5 performed for module 1
The same processing as 07 is performed. That is, the output voltage at the time of starting the converter is input. The output voltage when the module 1 is stopped may be used as the output voltage when the module 2 is started. Further, an output voltage detection value is input after a lapse of the determination period. The difference between the two output voltage detection values is compared with a reference voltage difference to determine whether there is a converter abnormality. If there is an abnormality, the fact is recorded in the system ECU 32.
Next, the converter module 3 is activated, and the same processing determines whether there is an abnormality. The processing for the converter modules 2 and 3 is the same as the processing of the module 1, and thus is omitted in FIG.

In the process for the converter module 3, it is not necessary to stop the converter even after the determination period P has elapsed and the time has reached T5 in FIG. If the three converter modules are normal, the system ECU 32
Starts the other converter modules 1 and 2. Thereby, the capacitor 24 is further charged. Charging is performed using the output voltage CO_VDET (ie, capacitor 2
4) until the target value is reached.

When it is detected that an abnormality has occurred in at least one of the three converter modules, the system ECU 32 performs a final “abnormality process” after the process of FIG. Here, use of an abnormal converter module is prohibited. The system ECU 32 drives only the normal converter module to charge the capacitor 24. The output of the wheel motor 28 is limited in response to the reduction in the performance of the entire converter. As a result, the power assist system can be continuously operated within the allowable range of the current converter capacity. If an abnormality has occurred in all converter modules, the DC / DC converter assembly 2
0 is prohibited, and the vehicle is driven using only the engine 10 without using the wheel motor 28.

The system ECU 32 lights the indicator in the driver's seat and informs the driver of the occurrence of an abnormality as part of the "abnormality processing". When the driver carries the vehicle to a maintenance shop or the like, the operator can access the system ECU 32 and know that an abnormality has occurred in the converter and which converter module has experienced the abnormality. This operation can be performed using an appropriate computer terminal capable of communicating with the system ECU 32. Further, when an operator performs a predetermined operation on a device in the vehicle, information about the abnormality may be displayed on a display in the vehicle. Since the operator can easily identify the abnormal converter module, the module can be replaced and repaired accurately and quickly.

The abnormality detection processing according to the second embodiment has been described above. In the present embodiment, the [abnormality detection process 2] is performed when each converter module is driven. On the other hand, the converter abnormality can be similarly detected by using [abnormality detection process 1] or [abnormality detection process 2] of the first embodiment. In the former case, the slope of the output voltage is obtained at an appropriate timing during driving of the converter, and is compared with a reference voltage slope. In the latter case, the output voltage detection value at the end of driving of each converter module is compared with a reference output voltage.

Since the abnormality detection processing of the second embodiment requires a certain amount of time, it is preferable to perform the abnormality detection processing as a part of the system start-up processing of S103 in FIG. When starting the converter during the traveling control, the converter abnormality is detected by the processing of the first embodiment. Depending on the use of such detection processing, it takes a long processing time, but a determination processing that can identify an abnormal converter is performed at the time of system startup, and a simple determination processing that ends in a short time while the vehicle is running can be performed. Therefore, the detection function of the second embodiment for specifying the abnormal converter can be incorporated into the drive system without affecting the traveling control.

The present invention is not limited to the system of the above embodiment, and the present invention is similarly applied to other systems. Further, the present invention can be similarly applied to abnormality detection of a DC / DC converter provided in a system other than the vehicle drive system.

Further, DC that can be suitably applied to the present embodiment
The / DC converter is, for example, as follows. However, the present invention is not limited to a system to which a DC / DC converter exemplified below is applied.

Further, a well-known flyback converter, forward converter, or other suitable converter may be applied to the DC / DC converter of the present embodiment.
With such a converter, according to the method of period,
Boost drive from the auxiliary battery side to the capacitor side is performed.

[0079]

As described above, according to the present invention, the occurrence of an abnormality in the DC / DC converter can be reliably detected by utilizing the speed of change of the output voltage. According to the present invention, even when a plurality of DC / DC converter modules are connected in parallel, converter abnormality can be reliably detected. Furthermore, by dividing and driving a plurality of DC / DC converter modules in a time series, it is possible to identify which converter module has an abnormality, and to take an appropriate abnormality handling process.

[Brief description of the drawings]

FIG. 1 is a diagram showing a vehicle drive system with a wheel motor according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an overall process of the system of FIG. 1;

FIG. 3 is a diagram showing a principle of a converter abnormality detection process together with a rising curve of an output voltage at the time of activation of a DC / DC converter of the system of FIG. 1;

4 is a diagram showing a principle of a converter abnormality detection process together with a rising curve of an output voltage when the DC / DC converter of the system of FIG. 1 is started.

FIG. 5 is a flowchart showing DC / DC converter abnormality detection processing 1;

FIG. 6 is a diagram showing the principle of DC / DC converter abnormality detection processing 2;

FIG. 7 is a diagram illustrating the principle of DC / DC converter abnormality detection processing 2;

FIG. 8 is a flowchart showing a DC / DC converter abnormality detection process 2;

FIG. 9 is a flowchart showing DC / DC converter abnormality detection processing 3;

FIG. 10 is a diagram showing a vehicle drive system with a wheel motor according to a second embodiment of the present invention.

11 is a diagram showing the principle of the abnormality detection processing of the DC / DC converter of the system of FIG.

12 is a diagram showing the principle of the abnormality detection processing of the DC / DC converter of the system of FIG.

13 is a flowchart showing an abnormality detection process of the DC / DC converter of the system of FIG.

FIG. 14 is a diagram showing a configuration example of a conventional vehicle drive system with a wheel motor.

[Explanation of symbols]

Reference Signs List 10 engine, 16 front wheel, 18 auxiliary battery, 19 alternator, 20 DC / DC converter assembly, 22a, 22b, 22c DC / DC
Converter module, 24 capacitors, 26 inverters, 28 wheel motors, 30 rear wheels, 3
2 System ECU, 34 Voltage sensor.

Claims (8)

[Claims] 1. An abnormality detection device for a DC / DC converter that converts an input DC voltage into a different DC voltage and outputs the converted DC voltage, comprising: voltage detection means for detecting an output voltage of the DC / DC converter; Abnormality determination means for determining whether or not a converter abnormality has occurred based on the detected value of the voltage, wherein the abnormality determination means determines that the speed of change of the detection value of the output voltage is equal to the output voltage in a converter normal state. A DC / DC converter abnormality detecting device that determines that a converter abnormality has occurred when the change speed is different from the change speed. 2. The abnormality detection device according to claim 1, wherein the abnormality determination unit calculates an inclination of an output voltage detection value with respect to a time axis, and sets the converter to a normal state based on the output voltage detection value. And DC / DC determining a converter abnormality by comparing the calculated voltage gradient value with the reference voltage gradient. Converter abnormality detection device. 3. The abnormality detection device according to claim 1, wherein the abnormality determination unit includes: a voltage change calculation unit configured to determine a change amount of an output voltage detection value before and after a predetermined determination period; and a start time of the determination period. Reference voltage change obtaining means for obtaining a reference output voltage change amount before and after a determination period corresponding to a converter normal state based on the output voltage of the converter. A DC / DC converter abnormality detection device, which determines whether or not a converter abnormality has occurred by comparing with a DC / DC converter. 4. The abnormality detection device according to claim 1, wherein the abnormality determination unit is configured to determine a reference of an end time of the determination period corresponding to a converter normal state based on an output voltage at a start time of a predetermined determination period. A reference voltage obtaining means for obtaining an output voltage, wherein a determination is made as to whether or not a converter abnormality has occurred by comparing a detected value of the output voltage at the end of the determination period with the reference output voltage. Abnormality detection device for DC / DC converter. 5. The abnormality detection device according to claim 1, wherein the DC / DC converter is a plurality of DC / DC converter modules provided in parallel between an input terminal and an output terminal of the converter. Wherein the output voltage of the DC / DC converter detected by the voltage detection means is a total output voltage of the plurality of DC / DC converter modules, and the abnormality determination means determines that all the DC / DC converter modules are normal. A DC / DC converter abnormality detecting device that determines that an abnormality has occurred in any of the plurality of DC / DC converter modules when the total output voltage changes at a speed different from the speed in a normal state. . 6. The abnormality detection device according to claim 1, wherein the DC / DC converter is a plurality of DC / DC converter modules provided in parallel between an input terminal and an output terminal of the converter. Wherein the output voltage of the DC / DC converter detected by the voltage detection means is a total output voltage of the plurality of DC / DC converter modules, and the plurality of DC / DC converter modules are individually separated by time division control. Time-division drive control means for driving the DC / DC converter modules when the total output voltage changes at a speed different from the speed in the converter normal state when the respective DC / DC converter modules are driven. And determining that an abnormality has occurred in the DC / DC converter module driven at that time. DC / DC converter of the abnormality detection device. 7. A method for detecting an abnormality of a DC / DC converter that converts an input DC voltage into a different DC voltage and outputs the converted DC voltage, wherein the output voltage of the DC / DC converter changes at a different speed from a converter normal state. A method for detecting an abnormality of a DC / DC converter, wherein it is determined that a converter abnormality has occurred when the error has occurred. 8. An engine for generating main propulsion of the vehicle,
An assist motor for generating an assist propulsion force of the vehicle, a DC / DC converter for boosting the power supplied from the auxiliary power storage means to power of a voltage required by the assist motor, and a DC / DC converter boosted by the DC / DC converter A motor power storage means for temporarily storing power and supplying the stored power to the assist motor; a voltage detection means for detecting an output voltage of the DC / DC converter; An abnormality determining unit that determines that an abnormality has occurred in the DC / DC converter when an output voltage changes at a speed different from a speed in a converter normal state when a converter is started to charge the motor power storage unit; And a vehicle drive system comprising: