JPH0345780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a temperature estimating device for estimating the armature winding temperature of, for example, a DC motor using a microcomputer.

[Prior art]

First, the principle of estimating the temperature rise will be explained using a DC motor as an example of an electrical device whose temperature is to be estimated.

The temperature rise of a DC motor is given by the formula:

Here, each variable is as follows.

θ: Temperature rise [℃] Q: Heat capacity of DC motor armature winding [W] P: Energy consumption rate of 〃 〃 [W] α: Heat dissipation rate per 1℃ increase of 〃 〃 [W/℃] t : Arbitrary time [sec] Also, DC motor armature winding energy consumption rate P
If it is almost copper loss, then P=I ² R[W]... Here, I: armature current [A] R: armature winding resistance [Ω].

Furthermore, if the temperature time constant T is set as T=4.2Q/α..., the equation becomes as follows from the equation.

θ=R/αI ² (1-e-t/T)... Therefore, the armature winding resistances R, α, and T (=4.2Q/α) can be determined depending on the DC motor used, so the armature current I By detecting and calculating the formula, the rising temperature θ can be estimated.

FIG. 4 is a block diagram of a conventional apparatus for estimating armature winding temperature of a DC motor. This device is comprised of a detection circuit 1 that detects the armature current of a DC motor, and a microcomputer 2 that inputs signals from the detection circuit 1.

FIG. 5 is a functional block diagram of the operation performed by the microcomputer 2, and FIG. 6 is a flowchart showing the operation. The microcomputer 2 calculates the temperature rise θ from the armature current value I according to a formula according to a predetermined program. That is, in FIG. 5, 21 is a circuit that squares the current value I from the detection circuit 1, and 22 is a circuit that multiplies this by the armature winding resistance R, and the heat dissipation rate of the armature winding per 1°C rise. 23 is a subtraction circuit; 24 is a circuit that divides the signal from the subtraction circuit 23 by the temperature time constant T; 25 is a circuit that integrates the signal from the division circuit 24 using the Laplace operator S. , from which a signal indicating the rising temperature θ is obtained. A signal indicating this increased temperature is negatively fed back to the subtraction circuit 23.

In a conventional device using a microcomputer that is shown in such a functional block diagram and operates as shown in the flowchart in Figure 6, the DC motor is first turned on, and when the temperature rises from the initial temperature, it is accurately controlled. Temperature can be estimated, but if the motor is powered off after t ₁ hour, for example, and turned on again at t ₂ hours, the armature winding at t ₂ can be estimated. Since the temperature of the wire was unknown, it was not possible to accurately estimate the subsequent temperature of the armature winding.

FIG. 7 is a diagram illustrating this, showing actual temperature changes in the armature winding. In the conventional device, the estimated temperature after time _t2 is as shown by the broken line, which is lower than the actual temperature (solid line) and is not accurate.

[Summary of the Invention] The present invention comprises a detection circuit that detects the current flowing through an electrical device, and a microcomputer that inputs a signal from the detection circuit and performs a predetermined calculation to estimate the temperature of the electrical device. In the device,
means for outputting a signal related to the estimated temperature when the electrical equipment is powered off; a discharging circuit having a discharge time constant substantially the same as a temperature time constant of the electrical equipment to which the signal from the output means is input; means for applying the output signal of the discharge circuit to the microcomputer when the power of the device is turned on, and the microcomputer generates electricity by using the output signal of the discharge circuit and the signal from the detection circuit when the power is turned on again. By estimating the temperature of the equipment, it is possible to accurately estimate the temperature of the armature winding even when the motor is powered off and then turned on again. The present invention provides an estimation device.

[Embodiments of the invention]

FIG. 1 is a block diagram showing an example of a device according to the present invention. In this figure, 1 is a detection circuit that detects an armature current of a DC motor (not shown), and 2 is a microcomputer that inputs a signal from this detection circuit. This microcomputer has a predetermined calculation program and performs calculations to estimate the armature winding temperature. 3 is 3
is a D/A converter that converts a digital signal related to the estimated temperature calculated by the microcomputer 2 into an analog signal, and this D/A converter converts the estimated temperature data at the time when the power of the DC motor is turned off into an analog signal. and output. Reference numeral 4 denotes a discharge circuit which inputs the signal from the D/A converter, the discharge time constant of which is selected to be the same as the temperature time constant of the direct current motor, and here constituted by a capacitor and a resistor. Reference numeral 5 denotes an A/D converter that converts the output signal of the discharge circuit 4 into a digital signal and applies it to the microcomputer 2 when the DC motor is powered on.

The operation of the device configured in this way will be described next. When the DC motor is powered on, the microcomputer 2 first reads the output signal of the discharge circuit 4 via the A/D converter 5, and converts this data into the initial value of the armature winding temperature, that is, as shown in FIG. The temperature of the armature winding is estimated using the same principle as the conventional device. In this device, after driving the DC motor, if the power is turned off after ₁ hour t as shown in Fig. 2, the signal related to the estimated temperature θ ₁ at time t ₁ will be converted into a D/A converter. The voltage is applied to the discharge circuit 4 through the device 3. The output signal of this discharge circuit 4 (shown by the broken line in Figure 2) is then attenuated by the time constant of the CR, but the discharge time constant of the CR is selected in advance to be the same as the temperature time constant of the DC motor. , changes in accordance with the temperature of the armature winding (shown by the solid line in Figure 2). Therefore, when the power is turned on again at time _t2 , a signal corresponding to the armature winding temperature _θ2 at this time is applied to the microcomputer via the A/D converter 5, and the microcomputer 2 By using the data related to the armature winding temperature θ ₂ at time t ₂ as an initial value and performing a predetermined calculation using the signal from the detection circuit 1, the subsequent armature winding temperature is accurately estimated. be able to. FIG. 3 is a flowchart showing the operation of the microcomputer when the power is turned on.

Note that in the above explanation, the temperature of the armature winding of a DC motor is estimated, but it is not limited to armature windings, which have characteristics such that their temperature increases when current flows. It can be applied to estimate the temperature of various electrical devices.

〔Effect of the invention〕

As explained above, according to the present invention, a signal corresponding to the temperature change of the device can be obtained from the output terminal of the discharge circuit even when the power is turned off, and even after the power is turned on again. It is possible to accurately estimate the temperature of electrical equipment.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing an example of the device according to the present invention, FIG. 2 is a waveform diagram for explaining its operation, FIG. 3 is a flowchart showing an example of the operation of a microcomputer, and FIG. 4 5 is a block diagram of the configuration of the conventional device, and FIG. 5 is a functional block diagram of the operation performed by the microcomputer in FIG. 4.
Figure 6 is a flowchart showing the operation, Figure 7
The figure is an operation waveform diagram. 1... Current detection circuit, 2... Microcomputer, 3... D/A converter, 4... Discharge circuit, 5... A/
In the D converter, the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A current detection circuit that detects a current flowing through an electrical device whose temperature is to be estimated, and a signal from this current detection circuit is inputted and a predetermined calculation is performed to estimate the temperature of the electrical device. A device comprising a microcomputer that outputs a signal related to the estimated temperature when the electric device is powered off, and a temperature time constant of the electric device to which the signal from the output device is input. A discharge circuit having the same discharge time constant and a means for applying an output signal of the discharge circuit to the microcomputer when the electric device is powered on are provided, and the microcomputer applies the output signal of the discharge circuit and the current detection A temperature estimation device characterized by performing calculations to estimate the temperature of an electrical device from an output signal of a circuit.