JPH0136374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vacuum cleaner having a heat sink for cooling a semiconductor element that controls the current of an electric blower.

Conventional Technology In recent years, vacuum cleaners with power consumption control devices have been commercialized from the perspective of energy conservation. Semiconductor devices such as three-terminal controlled rectifiers have come into use. In addition, magnetic relays were conventionally used to turn on and off the power by remote control, but due to problems such as dust getting into the contacts and poor durability, semiconductor relays were considered and put into practical use. It has been. When using such a semiconductor element in a vacuum cleaner, the most important thing to keep in mind is how to prevent the semiconductor element from overheating. Needless to say, semiconductor devices have the characteristic of generating self-heating when current flows through them, and if this exceeds an upper limit, they will be destroyed. Especially in vacuum cleaners, electric blowers generate self-heating. When the exhaust gas temperature increases and the amount of air flowing in decreases due to clogging of the filter device, the temperature of the exhaust passage itself sometimes approaches the upper limit of the temperature of the semiconductor element. For this reason, in the past, a heat sink to which the semiconductor element was fixed was provided, and this heat sink was placed in a compartment that was isolated from the exhaust passage of the main body and communicated with the atmosphere, and this compartment was further communicated with the intake side of the front of the electric blower. A method was adopted in which cooling air was always sucked in from the atmosphere when the electric blower was rotating.

However, with the above-mentioned means, there is always an airflow that bypasses the filter device, which leads to a decrease in suction performance.

In addition, instead of guiding the air sucked by the electric blower into a compartment, the compartment was opened to the atmosphere, and in addition, a ventilated opening facing the exhaust path of the electric blower was formed in a part of the compartment. (Jikko 49-
Publication No. 31017).

Problems to be Solved by the Invention The ventilate opening has a low pressure due to the effect of the exhaust flow (ventilation effect), and therefore the atmosphere is sucked into the compartment and cools the heat sink.

However, a fatal drawback of this cooling means is that when the filter device becomes clogged, the amount of air flowing through the compartment is reduced. That is,
If the intake flow rate of the electric blower decreases due to clogging of the filter device, the exhaust flow rate of the electric blower will naturally decrease as well. As is well known, the Ventilly effect changes in proportion to the flow rate, and therefore, the above-mentioned means cannot always reliably cool the heat sink.

The present invention solves these conventional problems and aims to constantly and reliably cool semiconductor elements.

Means for Solving the Problems In order to solve these conventional problems, the present invention includes a built-in electric blower and an exhaust passage that communicates the electric blower with an exhaust hole for discharging the exhaust air to the outside air. A safety valve device that directly communicates the formed main body with the negative pressure section at the front of the electric blower and the atmosphere, and opens and introduces outside air due to the pressure difference between the negative pressure section and outside air, and a semiconductor element for current control. This heat sink faces the exhaust passage substantially perpendicularly to the exhaust passage.

Effects According to the present invention, when the filter device is not clogged and the vacuum cleaner is operating normally, the safety valve device is closed and atmospheric air is not introduced into the compartment. However, in this case, since the exhaust temperature of the electric blower is low, the electric blower can be used to encourage the electric blower to be left on the heat sink. Furthermore, if the filter device becomes clogged and the degree of negative pressure in the negative pressure section at the front of the electric blower becomes high, the safety valve device opens and external air is directly mixed into the electric blower. Therefore, the flow rate of the exhaust gas does not substantially change, and the temperature of the exhaust gas does not increase significantly, so that heat radiation from the heat sink can be maintained satisfactorily.

Embodiments Hereinafter, embodiments will be described with reference to the accompanying drawings.

In the figure, 1 is a main body roughly divided into left and right sides,
Inside, an electric blower 4 held by a front support 2 and a rear support 3, and a winding device 6 for a power cord 5 are installed. Reference numeral 7 denotes an exhaust passage formed by an outer wall 8 and an inner wall 9 of the main body 1, through which exhaust air flows from an electric blower chamber 10 to an exhaust chamber 11, and is discharged to the outside air via an exhaust filter 12 and an exhaust hole 13. Reference numeral 14 denotes a dust collection box that is detachably attached to the main body 1 by a buckle device 15, and has a filter device 16 inside it that can be detached from the main body 1. When the dust collection box 14 is attached to the main body 1, the filter packing 17 is in close contact with the main body 1 and the negative pressure part 1
form 8. Reference numeral 19 denotes a handle formed integrally with the main body 1, into which there is a pressure-type safety valve device 20 that operates to introduce outside air when the suction power is lower than the maximum air volume.
is installed. This safety valve device 20 includes a connecting pipe 21 that communicates with the negative pressure section 18, and a connecting pipe 21 that communicates with the negative pressure section 18.
One end is connected to the valve spring 22 and the valve body 2.
3 and a transparent valve cylinder 25 with a valve hole 24 smaller in diameter than the outer diameter of the valve element 23 at the other end.The valve element 23 is slidable inside the valve cylinder 25, and It is biased toward the hole 24 side by a valve spring 22. 26 is a ventilation hole formed in the handle 19, through which outside air is introduced and introduced into the safety valve device 20. 27 is an open display window through which the movement of the valve body 23 can be confirmed through the transparent valve barrel 25. Reference numeral 28 denotes a metal heat sink to which a bidirectional three-terminal control rectifier element 29 (hereinafter referred to as a semiconductor element), which is a semiconductor element, is fixed with screws or the like.
It is housed in a compartment 30 formed at the rear of the main body 9 and is sandwiched between the left and right partition walls 31 of the main body 1 that partition the compartment 30 and the exhaust passage 7, and a part of the heat sink 28 is vertically disposed inside the exhaust passage 7. It stands out. 3
Reference numeral 2 denotes a printed circuit board incorporating a control circuit, which is held by a rib body 33 of the main body 1.

Next, the electric circuit will be briefly explained based on FIG. The printed circuit board 32 includes a trigger element 34 for sending a signal to the semiconductor element 29 fixed to the heat sink 26, and a variable resistor 35, a resistor 36, and a capacitor 37 for adjusting the signal current of the trigger element 34. A control circuit that controls the current flowing through the electric blower 4 and changes the rotation speed of the electric blower 4 is incorporated. A capacitor 38 and a resistor 39 are a protection circuit for the semiconductor element 29, and a hand switch 40 for remote control is also provided.
A current is caused to flow through the control circuit by turning on and off.
In addition, the current flowing through the auxiliary bidirectional three-terminal control rectifier element 41 (hereinafter referred to as auxiliary semiconductor element), the trigger element 42 that sends a signal to this auxiliary semiconductor element 41, the capacitor 43, and the hand switch 40 is reduced to a minute current. A resistor 44 is provided. In the above circuit, when the hand switch 40 is turned on after applying voltage to the power source, the capacitance is stored in the capacitor 43, and when the voltage reaches a certain level, a signal is sent from the trigger element 42 to the auxiliary semiconductor element 41.
A current is passed through. Then, current flows into the control circuit by the auxiliary semiconductor element 41, and the capacitor 38
When a certain capacity is accumulated, a signal is sent from the trigger element 34 to the semiconductor element 29, current flows through the main circuit, and the electric blower 4 rotates. This semiconductor element 2
9 causes a self-heating effect when a large current flows, and if it exceeds a certain limit, the junction part inside the semiconductor element 29 is destroyed, so the heat sink 28
It must be kept constantly cooled. The semiconductor element 29 used in this example has a junction temperature of 125°C as a limit, and in this case, the semiconductor element 29
The upper limit of the junction case temperature Tj (hereinafter referred to as Tj) on the surface of 9 is set at 75°C. When the hand switch 40 is turned off, the auxiliary semiconductor element 41 no longer conducts current, and the main circuit also stops current.
The electric blower 4 stops.

In the above configuration, when the electric blower 4 rotates, the exhaust air flows through the exhaust passage 7, but if the filter device 16 is not clogged and there is sufficient air flow, the electric blower 4 is also cooled.
The temperature of the exhaust flow is low and cools the heat sink 28 protruding into the exhaust passage 7 to prevent the temperature of the semiconductor element 29 from rising excessively. Next, when the filter device 16 becomes clogged and the exhaust flow rate decreases, the cooling of the electric blower 4 becomes insufficient, the temperature of the exhaust passage 7 rises, and the cooling effect of the semiconductor element 29 deteriorates. In this case, when the air volume at the tip of the hose extension pipe becomes less than around 0.7 m ³ /min, the pressure of the negative pressure part 18 overcomes the biasing force of the valve spring 22 and moves the valve body 23 toward the connecting pipe 21, and the outside air is Since the air flows into the negative pressure section 18 through the ventilation hole 26 and the valve hole 23, the exhaust flow rate of the electric blower 4 is kept above a certain level, and there is no significant temperature rise. Therefore, the semiconductor element 29 is cooled by the outside air, and an excessive temperature rise is prevented.

To explain about FIG. 4, it is a graph depicting how the temperature changes. The curve shown in FIG. This shows the change in temperature rise with air volume. As the exhaust passage temperature rises, the cooling effect worsens, and the Tj upper limit is exceeded. The curve shows the change in air volume immediately before the safety valve operates when all the heat sinks 28 with semiconductor elements 29 are housed in the compartment 30 of the handle 19. Since it is in contact with the air, there is a cooling effect to some extent and the upper limit of Tj is not exceeded, but if the safety valve device 20 does not operate and the air volume further decreases, the temperature of the exhaust passage 7 will rise and approach the curve. Since the Tj upper limit value would be exceeded, a safety valve device 20 is provided to prevent the temperature from rising by introducing cooling air when the air volume falls below a certain level. Of course, in view of the above, if the heat sink 28 is completely separated from the exhaust passage 7 and other areas where the temperature rises, the safety valve device 20 is unnecessary, but in this case, the main body 1 becomes large. Next, to explain the curve, the temperature change when the heat sink 28 is made to protrude into the exhaust passage 7 as shown in FIG.
The temperature change in the open air volume when the valve 6 is not clogged is the temperature change when the air volume is just before the safety valve device 20 operates (approximately 0.7 m ³ /min in this example), and as the air volume decreases, The temperature rise also increases,
Although the cooling effect of the heat radiating plate 28 decreases, when the air volume is sufficient (close to the open air volume), the heat radiating plate 28 is cooled by the exhaust flow to prevent temperature rise.
Immediately before the safety valve device 20 operates, the heat sink 28
The effect of protruding into the exhaust passage 7 is eliminated, but
When the air volume drops slightly below this level, the safety valve device 20 is activated, and cooling air flows through the compartment 30 of the handle 19 to cool the semiconductor element 29 . Therefore, since the temperature rise value is lower than that of the curve, it is possible to use the semiconductor element 29 with a lower upper limit of Tj.

Next, regarding the cooling effect of the heat sink 28, as shown above, since it projects into the exhaust passage 7, it is normally cooled by the exhaust flow. By the way, 100% of the dust collected by the vacuum cleaner is not collected by the filter device 16, and a few percent of the fine dust is discharged backward with the exhaust flow, so it also adheres to the surface of the heat sink 28. It has become clear through experiments that the heat dissipation effect is reduced.
Among these, if the heat sink 28 is arranged horizontally, fine dust floating in the exhaust air will accumulate on the upper surface of the heat sink 28 after the electric blower 4 stops, and it will adhere in a layered manner especially during times of high humidity. In order to reduce the cooling effect of half of the plane portion of the heat sink 28, it was necessary to use a semiconductor element 29 with a higher heat-resistant temperature, but in the above configuration, the heat sink 28 is made to be approximately vertical. This prevents the adhesion of fine dust and improves the sustainability of the cooling effect.

In the above embodiment, all of the heat sinks 28 protruding into the exhaust passage 7 are vertical, but if at least half of the area of the heat sink 28 is made substantially vertical, the area of the heat sink 28 can be reduced. Since more than 75% of the cooling effect can be effectively utilized, the sustainability of the cooling effect can be maintained.

Effects of the Invention As described above, according to the present invention, since the heat sink on which the semiconductor element is installed faces approximately vertically into the exhaust flow,
This makes it difficult for fine dust contained in the exhaust flow to adhere to the heat sink, which has the effect of improving the sustainability of the cooling effect. Further, even if the filter device becomes clogged, the exhaust flow acting on the heat sink is maintained at a constant flow rate or higher, and the temperature does not rise significantly. Therefore, since the semiconductor element is always reliably cooled, the efficiency of the vacuum cleaner does not decrease significantly.

[Brief explanation of drawings]

Fig. 1 is a front view showing the overall structure of a vacuum cleaner according to an embodiment of the present invention in partial cross section, Fig. 2 is a cross-sectional view taken along the line A-A in Fig. The electrical circuit diagram used in the example, FIG. 4, is a temperature characteristic diagram showing the effects of this embodiment. 1...Main body, 4...Electric blower, 7...Exhaust passage, 18...Negative pressure section, 20...Safety valve device, 28
... Heat sink, 29 ... Semiconductor element, 30 ... Compartment.

Claims (1)

[Claims] 1 The main body has a built-in electric blower and an exhaust passage that communicates the electric blower with an exhaust hole for discharging the exhaust air to the outside air, and the negative pressure section at the front of the electric blower is in direct communication with the atmosphere. It is equipped with a safety valve device that opens and introduces outside air due to the pressure difference between the negative pressure part and the outside air, and a heat sink to which a semiconductor element for controlling current is fixed. Vacuum cleaner.