JP2004248458A - Driving device for hybrid electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a converter for hybrid electric vehicle which is reliable and starts an engine with a reduced current command at a high ambient temperature, at which high torque required to start the engine at low temperature is not required. <P>SOLUTION: The driving device for a hybrid electric vehicle comprises an internal combustion engine 1, an ac motor 2 mechanically connected with the internal combustion engine 1, an inverter arrangement 3 for driving the ac motor 2, a dc power source 4 which supplies the inverter arrangement 3 with dc power, a control circuit 34 which controls the inverter arrangement 3, and a temperature detecting means which directly or indirectly detects the temperature of the internal combustion engine. The current supplied from the inverter arrangement 3 to the ac motor 2 is limited to a first current value lower than the limit current value of the inverter arrangement 3 according to the temperature detected by the temperature detecting means. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improved hybrid electric vehicle drive.
[0002]
[Prior art]
A hybrid electric vehicle drive device includes an internal combustion engine (hereinafter referred to as an engine), an AC motor, an inverter device for driving the engine, and a DC power supply for supplying power to the inverter device. The output shaft of the engine, the AC motor Are mechanically connected so that the engine and the AC motor cooperate to drive the vehicle body. Since the engine has low operating efficiency in the low-speed range and has a lot of exhaust gas, the hybrid mainly controls the vehicle with the output of the motor in the low-speed range, and controls the engine mainly in the high-speed range. This is the basic concept of an electric vehicle drive device.
[0003]
Although the driving force of the engine may be used even in a low speed range, even in such a case, starting from a stopped state usually depends on the starting torque of the AC motor. Therefore, the AC motor in the hybrid electric vehicle drive device requires the most torque at the time of starting. In other words, the inverter device is in a state where the maximum current flows at the time of starting.
[0004]
On the other hand, the main circuit power device used in the inverter device is susceptible to heat, and when its temperature rises, there is a risk of causing thermal destruction. For this reason, a technique has been devised to detect the temperature near the main circuit power device and to reduce the current command of the inverter device when the temperature exceeds a certain value (for example, see Patent Document 1).
[0005]
The idea of Patent Document 1 is an idea of always operating the output current of the inverter device at a limit value. However, in order to further secure the protection of the main circuit power device and increase the reliability of the inverter device, it is also important to devise a method to further reduce the starting current when the load is small.
[0006]
[Patent Document 1]
JP-A-11-252932 (pages 2-4, FIG. 1)
[0007]
[Problems to be solved by the invention]
As described above, since the inverter starts with the maximum current when the engine is started, the temperature of the main circuit power device is required if the so-called idling stop operation is frequently performed as recently implemented as a measure to reduce exhaust gas. There is a possibility that the main circuit power device may be damaged.
[0008]
The present invention has been made in view of the above points, and when the ambient temperature is high, a high torque required for starting the engine at a low temperature is not required. An object of the present invention is to provide a highly reliable drive device for a hybrid electric vehicle.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a hybrid electric vehicle drive device according to the present invention includes an engine, an AC motor mechanically connected to the engine, an inverter device for driving the AC motor, and an inverter device. A DC power supply that supplies DC power, a control circuit that controls the inverter device, and a temperature detection unit that directly or indirectly detects the temperature of the engine, and the temperature detected by the temperature detection unit A current supplied from the inverter device to the AC motor is limited to a first current value smaller than a limit current value of the inverter device.
[0010]
According to the present invention, since the starting current of the inverter device can be suppressed, a highly reliable hybrid electric vehicle drive device can be provided.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
Hereinafter, a first embodiment of a hybrid electric vehicle drive device according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a hybrid electric vehicle drive device of the present invention.
[0012]
Engine 1 and AC motor 2 are mechanically connected. The AC motor 2 is driven at a desired voltage and frequency by an inverter device 3, and the inverter device 3 is supplied with DC power from a DC power supply 4 via a switch 5. The inside of the inverter device 3 includes a capacitor 32 and an inverter circuit 33 bridge-connected by main circuit power devices 33u, 33v, 33w, 33x, 33y, and 33z. The inverter circuit 33 is controlled by the control circuit 34.
[0013]
The configuration of the control circuit 34 is as follows. The torque current command iq * and the excitation current command id * obtained as the output of the current command value calculator 341 are compared with the feedback-calculated torque current iq and the excitation current id by the amplifier 342 and the amplifier 343, respectively. The outputs are a torque voltage command vq * and an excitation voltage command vd *. The torque voltage command vq * and the excitation voltage command vd * are converted into a three-phase voltage reference V * by a coordinate converter 344, which is converted into a pulse by a PWM controller 345 to obtain a gate signal for the inverter circuit 33. I have.
[0014]
On the other hand, the above-described torque current iq and excitation current id are used to detect any two-phase output current of the inverter device 3, for example, the U-phase current iu and the W-phase current iw. Converted to two phases. Here, the reference phase of the coordinate converter 346 is obtained by integrating the phase angle θr obtained by integrating the rotation speed n of the AC motor 2 and the slip frequency fs calculated from the torque current command iq * and the excitation current command id *. The phase angle θ obtained by adding the obtained phase angle θs is used. This phase angle θ is similarly used for the reference phase of the coordinate converter 344 described above.
[0015]
Next, the operation of the control circuit 34 will be described. The motor speed n is detected from a speed detector (not shown), and a phase angle θr obtained by integrating the detected speed n is obtained. On the other hand, the slip frequency fs is calculated from the excitation current command id *, the torque current command iq *, and the motor constant, and the slip frequency fs is integrated to obtain the phase angle θs. As described above, θ obtained by adding θs and the θr is used as the reference phase of the coordinate converter. This phase angle θ is the output phase of the inverter circuit 33 and the rotational magnetic field of the AC motor 2. It corresponds to the electrical angle to make. It should be noted that the motor speed n can also be obtained by calculation without using a speed detector.
[0016]
The motor current is detected, for example, by detecting a U-phase current and a W-phase current, and performing a biaxial coordinate conversion from three-phase to two-phase based on the above-described reference phase using a coordinate converter 346. Separate into current iq. The differences between the excitation current id and the torque current iq and the excitation current command id * and the torque current command iq * are amplified by the amplifiers 342 and 343, respectively, to obtain the excitation voltage command vd * and the torque voltage command vq *. . The excitation voltage command vd * and the torque voltage command vq * are subjected to two-phase / three-phase conversion by the coordinate converter 344, and the three-phase AC voltage command V * is pulse width-modulated by the PWM converter 345. Gate signals of 33u to 33z are obtained.
[0017]
Here, vector control is used to separate the motor current into a torque component (q-axis) and an excitation component (d-axis) orthogonal to the torque component (q-axis), and independently control the rotation speed n without using a rotation speed detector. It is already known that a method of performing similar control by calculating from a current signal or a motor constant and performing similar control is called sensorless vector control.
[0018]
Next, the internal configuration and operation of the current command value calculator 341 will be described with reference to FIG. FIG. 2A is an internal configuration diagram of the current command value calculator 341. An excitation current command id * and an initial torque current command iq0 * are output from a table based on the rotational speed n, and the torque current command iq * is determined by multiplying the initial torque current command iq0 * by a ratio α.
[0019]
FIG. 2B shows an example of the above-described table function for obtaining the excitation current command id * and the initial torque current command iq0 * according to the rotation speed n. As shown here, up to a certain rotational speed, the excitation current command id * has a constant torque characteristic that is constant, and above that, the excitation current command id * generally has a weakened constant output characteristic.
[0020]
FIG. 2C is a graph illustrating how the above-described ratio α is given to a change in the temperature thd in the vicinity of the main circuit power devices 33u to 33z. From a certain temperature t1, a pattern 1 in which the ratio α is reduced in proportion to the temperature, a pattern 2 in which the ratio α is reduced stepwise at the temperature t1, and furthermore, if the temperature becomes high, an excessive current is required when the temperature becomes high. A pattern 3 to be suppressed is conceivable. Here, although not shown, α determined from the limit withstand capability of the main circuit power devices 33u to 33z is always larger than α in pattern 1, and conversely, α determined from the load characteristics of the engine is always smaller than α in pattern 3.
[0021]
In this case, the engine temperature detection is performed by the temperature detection of the main circuit power devices 33u to 33z. However, since the engine 1 and the inverter device 3 are arranged in the vicinity, such substitution is possible. .
[0022]
As described above, by selecting the patterns 1 to 3, it is possible to prevent an excessive current from flowing when starting the engine 1 and suppress an excessive rise in temperature of the main circuit power devices 33u to 33z.
[0023]
Further, in the block diagram of FIG. 2A, the ratio α is multiplied only by the torque current command. However, when the torque current is reduced, the excitation current becomes large, and the efficiency of the motor deteriorates. It is also possible to multiply both id * and the initial torque current command iq0 * by this. Further, the current command is adjusted with the ratio α, but the limit value of the current command may be adjusted.
[0024]
Further, it is also possible to use the pattern 3 only when the engine 1 is started, that is, only in a region where the number of revolutions n of the electric motor is small, and switch to the patterns 1 and 2 when the number of revolutions exceeds a certain value.
[0025]
For example, an analog signal from a thermistor embedded in the main circuit power devices 33u to 33z or a contact signal from a thermostat attached to a fin can be used to detect the temperature in the vicinity of the main circuit power devices 33u to 33z.
[0026]
(Second embodiment)
FIG. 3 is a configuration diagram of a hybrid electric vehicle drive device according to a second embodiment of the present invention. Regarding each part of the second embodiment, the same parts as those of the hybrid electric vehicle drive device according to the first embodiment of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The second embodiment is different from the first embodiment in that an AC motor temperature thm is detected instead of detecting the temperature thd near the main circuit power devices 33u to 33z.
[0027]
Since the AC motor 2 is also disposed near the engine similarly to the inverter device 3, detecting the temperature of the AC motor 2 is substantially equivalent to detecting the temperature of the engine.
[0028]
Also in this case, the current command at the time of starting the engine 1 is adjusted by the ratio α shown in FIG. Can be suppressed.
[0029]
Note that a thermistor, a platinum resistor, a thermostat, or the like embedded in the winding of the AC motor 2 is used as the temperature detector of the AC motor 2.
[0030]
(Third embodiment)
FIG. 4 is a configuration diagram of a hybrid electric vehicle drive device according to a third embodiment of the present invention. Regarding each part of the third embodiment, the same parts as those of the hybrid electric vehicle drive device according to the first embodiment of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The third embodiment is different from the first embodiment in that a reactor 6 and a chopper circuit 31 are inserted between a switch 5 and a capacitor 32. The chopper circuit 31 includes a power device 31a connected in parallel and a power device 31b connected in series.
[0031]
A system in which the power is increased as a high voltage by the boosting operation of the chopper circuit 31 is generally smaller in size and higher in efficiency as compared with a case where the power is increased by a large current, and a higher voltage is obtained by a DC power supply, for example, a battery. In comparison, there is an advantage that the space and mass mounted on the vehicle can be reduced, and the traveling distance can be increased. Conversely, if the capacity of the AC motor 2 is relatively small, the chopper circuit 31 may perform a step-down operation for safety.
[0032]
As described above, even when the chopper circuit 31 that performs the step-up or step-down operation is added to the main circuit, it is possible to adjust the current command at the time of starting the engine 1 and suppress an excessive rise in temperature of the main circuit power devices 33u to 33z. it can.
[0033]
In the above description, the example in which the inverter device 3 is controlled by the vector is described. However, the present invention can be applied to the case of the sensorless vector control, and can be applied to another control method.
[0034]
【The invention's effect】
As described above, according to the present invention, a highly reliable hybrid electric vehicle drive device can be provided by lowering the current command and starting the engine while preventing the current from flowing to the main circuit power device more than necessary. .
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a hybrid electric vehicle drive device according to a first embodiment of the present invention.
FIG. 2 is a detailed explanatory diagram of a current command value calculator according to the present invention.
FIG. 3 is a configuration diagram of a hybrid electric vehicle drive device according to a second embodiment of the present invention.
FIG. 4 is a configuration diagram of a hybrid electric vehicle drive device according to a third embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 engine 2 AC motor 3 inverter device 4 DC power supply 5 switch 6 reactor 31 chopper circuit 31a, 31b power device 32 capacitor 33 inverter circuit 33u, 33v, 33w, 33x, 33y, 33z main circuit power device 34 control circuit 341 current command Value calculator 342 Amplifier 343 Amplifier 344 Coordinate converter 345 PWM controller 346 Coordinate converter

Claims (5)

An internal combustion engine,
An AC motor mechanically connected to the internal combustion engine,
An inverter device for driving the AC motor;
A DC power supply for supplying DC power to the inverter device,
A control circuit for controlling the inverter device;
Temperature detection means for directly or indirectly detecting the temperature of the internal combustion engine,
A hybrid electric vehicle driving device, wherein a current supplied from the inverter device to the AC motor is limited to a first current value smaller than a limit current value of the inverter device, based on the temperature detected by the temperature detecting means. . Means for detecting a starting state of the inverter device, wherein a current supplied from the inverter device to the AC motor is limited to a second current value smaller than the first current value at the time of starting. Item 6. The hybrid electric vehicle drive device according to item 1. The hybrid electric vehicle drive device according to claim 1, wherein the temperature detection unit is a temperature detector attached near a power device of the inverter device. The hybrid electric vehicle drive device according to claim 1, wherein the temperature detection unit is a temperature detector attached to the AC motor. 5. The hybrid electric vehicle drive device according to claim 1, wherein the inverter device is supplied with power from the DC power supply via a reactor and a chopper. 6.

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