JPS6082971A - Current detecting device for electric automobile - Google Patents

Abstract

PURPOSE:To raise measuring accuracy, and especially, to raise measuring accuracy in a low current area by using selectively two current sensors having different sensitivity when driving a vehicle and when charging a battery. CONSTITUTION:When driving a vehicle, a current flowing to a driving motor 3 through a power control device 2 from a battery 1 is detected by a large current measuring sensor 4. A detecting output is inputted to a microcomputer 9 through a signal selecting circuit 7 and an A/D converter 8, expressed in terms of a current value corresponding to the sensitivity of the large current measuring sensor 4, and a signal corresponding to its integrating value is displayed on an indicator 10. On the other hand, when charging a battery 1, a signal 20 for showing a fact that charging is being executed from a charger 6 is outputted to the signal selecting circuit 7 and the microcomputer 9, a detecting output of a small current measuring sensor 5 is inputted to an operating circuit 30 through the signal selecting circuit 7, and its current integrating value is displayed on the display part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a current detection device for an electric vehicle, and more particularly to a current detection device for an electric vehicle that detects current flowing into and out of a battery mounted on an electric vehicle.

[Prior art]

A drive device for an electric vehicle is configured by connecting a battery and a power converter via a power line, and connecting a vehicle drive electric motor (traction motor) to the power converter. This power converter controls the vehicle drive electric motor based on a current command value corresponding to the amount of accelerator depression, and a maximum current of 500 A flows through the power line when the vehicle is accelerated. In addition, when the battery capacity decreases, a charger that is connected to an external AC power source and converts AC current to DC current is connected to the power line via a charging line, and a current of about 1 to IOA is applied for a long time (approximately 8 o'clock). ) and the battery is charged.

Conventional electric vehicles are equipped with a current integrator that detects the current flowing into and out of the battery and calculates a current integrated value (amount of electricity) from this current to detect the capacity of the battery. Shunt resistors, Hall elements, etc. are often used as current measurement sensors to detect the current flowing into and out of the battery, and these sensors are connected to the power line, but the measurement accuracy of these sensors is limited to the full scale. It is about 1%. However, as mentioned above, the current value of an electric car is up to 5 when accelerating.
Although the current can be as high as 00A, only a current of about 1 to IOA flows during battery charging. Therefore, when a current of 500A flows, there is only an error of 5A, but 10A
When a small current flows, the error becomes as much as 50% (5 A).

In the conventional current integrator, the current in the above-mentioned range was measured with one sensor, and therefore the measurement accuracy was particularly poor in the low current range, which caused a practical problem.

[Purpose of the invention]

The present invention was made to solve the above problems, and an object of the present invention is to provide a current detection device for an electric vehicle with improved measurement accuracy.

[Structure of the Invention] In order to achieve the above object, the present invention provides a sensor for measuring a large current that detects a current flowing through a power line for supplying power from a battery to a vehicle drive electric motor, a charger, and the power line. A small current measurement sensor that detects the current flowing through a charging line connected to charge a battery and outputs a detected value with an error smaller than the maximum error of the large current measurement sensor at the Niful scale, and a small current measurement sensor that detects a current flowing through a charging line to charge a battery. a signal selection circuit that selects the output of the large current measurement sensor during power supply and selects the output of the small current measurement sensor during charging; and calculates current flowing into and out of the battery based on the output of the signal selection circuit. and an arithmetic circuit that detects the battery current. As a result, the large current flowing out of the battery is measured by the large current measurement sensor output, and the small current flowing into the battery is charged to the small current measurement sensor output, reducing the error of the small current measurement sensor at full scale. Since the maximum error of the large current measurement sensor is made smaller, the accuracy is improved compared to when detecting current using only the large current measurement sensor.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings. In this embodiment, the present invention is applied to a current integrator that calculates a current integrated value from the current value flowing into and out of a battery.

FIG. 1 shows the configuration of the current integrator according to this embodiment. In the figure, 1 is a battery, and 2 is an i-dynamic motor 3 connected to the battery via a power line t to drive the vehicle. A power control device 4 that controls the power to be supplied is a large current measurement sensor that detects the current flowing through the power line 11, and is capable of measuring up to several hundred amperes of current when the drive motor 3 is driven.

Further, 5 is a small current measuring sensor that detects the current flowing into the battery when charging the battery 1 with the charger 6, and the current 1 to IO flowing through the charging line 12 when charging the battery.
Measure A.

Further, 7 is a sensor 4 for measuring current flow, and a sensor 5 for measuring small current.
A signal selection circuit 9 is a microcomputer that receives the output of the A/D converter 8 and converts and integrates the current value according to the current sensor selected by the signal selection circuit.

The A/D converter 8 and the microcomputer 9 constitute an arithmetic circuit 30.

"e fc 10" This is a display section that receives the calculation output of the microcomputer 9 and displays the current integrated value.

In the above configuration, while the vehicle is operating, the current flowing from the power supply 1 to the drive motor 3 via the power control device 2 is detected by the large current measurement sensor 4, and the detection output of the sensor 4 is detected by the signal selection circuit 7. The A/D converter 8 converts the signal into a digital value via the A/D converter 8.

The output of the A/D converter 8 is the microcomputer 9.
is converted into a current value corresponding to the sensitivity of the large current measurement sensor 4, and a signal corresponding to the integrated value is outputted from the microcomputer 9. Further, the display 10 receives the output of the microcomputer 9 and displays the current integrated value.

On the other hand, when charging the battery 1, the charger 6 outputs a signal 20 indicating that charging is in progress to the signal selection circuit 7 and the microcomputer 9, and the detection output of the small current measurement sensor 5 is selectively selected by the signal selection circuit 7. Incorporated into A/D
It is input to converter 8. Then, the detection output of the sensor 5 is converted into a digital value, and the microcomputer 9 converts the output of the A/D converter 8 into a current value corresponding to the sensitivity of the small current measurement top/suction 5, and the integrated value. A corresponding signal is output. Furthermore, the current integrated value is displayed on the display section 10.

Figure 2 shows the operation flow of the current integrator described above, and Figure 3 shows the operation flow of the current integrator described above.
The figure shows an example of the measurement accuracy of the current sensor.

In Figure 3, curve A represents the characteristics of a sensor for measuring small currents.
Song mB shows the characteristics of the large current measurement sensor. For example, conventional large current measurement sensors (up to 5008"
! , which can be measured with , will have an error of 5 A assuming an accuracy of 1% full scale, but since the current flowing during charging is about IOA, this error will be as high as 50%.

However, when used together with a small current measurement sensor (capable of measuring up to 50A, error 1% full scale), it is 0.5A.
It can be seen that the current measurement accuracy is improved by keeping the error to .

As explained above, in this embodiment, two current sensors with different sensitivities are used separately for driving the vehicle and charging the battery, which improves measurement accuracy, especially in the low current range. I can figure it out. Specifically, for example, if only a conventional high current measurement sensor (capable of measuring up to 500A) is used, assuming 1% full scale accuracy, there will be an error of 5A, but since the current flowing during charging is about IOA. This error is as much as 50%. However, when a small current measurement sensor (measurable at maximum 50 A-t, error 1% full scale) is used in combination, the error remains at 0.5 and the current measurement accuracy improves.

〔Effect of the invention〕

According to the present invention, it is possible to realize a current detection device for an electric vehicle with improved measurement accuracy.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the current integrator for electric vehicles according to the present invention, Fig. 2 is a flowchart showing the operation of the current integrator shown in Fig. 1, and Fig. 3 shows the measurement accuracy of the current sensor. FIG. 3 is a characteristic diagram showing an example. 4... Sensor for large current measurement, 5... Sensor for small current measurement, 6... Charger, 7... Signal selection circuit, 8... A
/ D converter, 9...Microcomputer, 10...Display device. Agent Tatsuyuki Unuma (and 1 other person) Figure 1

Claims (1)

[Claims] (1) A large current measurement sensor that detects the current flowing through the power line that supplies power from the battery to the vehicle drive electric motor, and the current flowing through the charging line that connects the charger and the power line to charge the battery. Selecting a small current measurement sensor that detects current and outputs a detected value with an error smaller than the maximum error of the large current measurement sensor at full scale, and an output of the large current measurement sensor when power is supplied to the vehicle electric motor. and a signal selection circuit that selects the output of the small current measurement sensor during charging, and an arithmetic circuit that calculates the current flowing into and out of the battery based on the output of the signal selection circuit and detects the battery current. Current detection device for electric vehicles.