JPH0588261A - LCD projector lamp safety device - Google Patents

Abstract

(57) [Summary] [Purpose] When replacing the projection lamp, automatically prevent the operator from touching the projection lamp until the projection lamp has cooled to a safe temperature. A safety device 1 of a liquid crystal projector detects the temperature of a projection lamp 3 by a thermistor 2 which is a temperature sensor, displays the detection result on a light emitting diode 4 which is a display, and detects the temperature. Based on the result, the door lock mechanism unit 5 locks the door of the storage unit that stores the projection lamp 3. The operator judges that the temperature of the projection lamp 3 has dropped below the safe temperature T1 even when touched by hand because the light emitting diode 4 stops emitting light, and the unlocked door is opened to open the projection lamp. Exchange 3 Thereby, when replacing the projection lamp 3, it is possible to automatically prevent an operator from touching the projection lamp 3 until the projection lamp has cooled to a safe temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lamp safety device for a liquid crystal projector which can enhance safety when replacing a projection lamp.

[0002]

2. Description of the Related Art In recent years, a liquid crystal projector using a liquid crystal panel has been developed as a projection image receiver for enlarging and projecting an image on a screen. Since the liquid crystal panel does not emit light by itself, in the liquid crystal projector, the light from the projection lamp is transmitted to the liquid crystal panel and enlarged and projected on the screen. As the projection lamp in this case, a high light emission lamp such as a metal halide lamp is generally used in order to obtain a bright and clear image.

Since such a projection lamp uses a large amount of electric power, high heat is generated during use. Moreover, since the projection lamp does not have a long life, it needs to be replaced within a certain period of time. When replacing the projection lamp, it is very hot during use, so the projection lamp is turned off and then waits for it to cool down before replacement. However, the waiting time until the projection lamp cools depends on the prediction of the experience of users such as users, and if the prediction goes wrong, the hot projection lamp will be touched by the hand and burns. Had caused an accident such as. Also, depending on the worker,
Forgetting to wait for the projection lamp to cool down often caused accidents such as burns.

[0004]

In the above-mentioned conventional liquid crystal projector, the waiting time until the projection lamp is cooled when the projection lamp is replaced depends on the prediction of the experience of the operator. If the projection lamp went crazy or if the user forgot to wait for the projection lamp to cool, he or she would touch the high-temperature projection lamp with his / her hand, causing an accident such as a burn.

The present invention eliminates the above problems, and when replacing the projection lamp, the liquid crystal projector can automatically prevent an operator from touching the projection lamp until the projection lamp has cooled to a safe temperature. The purpose is to provide a safety device.

[0006]

A lamp safety device of a liquid crystal projector determines a temperature sensor for detecting the temperature of a projection lamp of the liquid crystal projector and determines whether or not the detection result of the temperature sensor exceeds a predetermined value. A determination means, a display for displaying the determination result of the determination means, and a door locking means for locking the door containing the projection lamp when the determination means determines that the predetermined value is exceeded. It is characterized by having.

[0007]

According to this structure, the display is not cooled to a safe temperature until the detection result of the temperature sensor becomes a predetermined value or less, that is, the projection lamp is cooled to a safe temperature. Is displayed, and the locking means locks the door housing the projection lamp, so when replacing the projection lamp, do not allow the operator to touch the projection lamp until it cools to a safe temperature. It can be prevented automatically.

[0008]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a safety device for a liquid crystal projector according to the present invention.

In FIG. 1, a liquid crystal projector safety device 1 detects the temperature of a projection lamp 3 by a thermistor 2 which is a temperature sensor, and displays the detection result on a light emitting diode 4 which is a display. With
Based on the detection result, the door locking mechanism 5 locks the door of the housing for housing the projection lamp 3.

More specifically, in the DC power supply 6, the negative output terminal is connected to the reference potential point, and the positive output terminal is connected to the reference potential point via the thermistor 2 and the resistor R1 connected in series. Therefore, a DC voltage of voltage V0 is output from the positive output terminal. A reflector 3 is provided on the projection lamp 3.
1 is attached, and the thermistor 2 is arranged on the rear surface of the reflector 31. As the thermistor 2, one having a negative temperature coefficient of resistance is used, and the resistance value decreases as the temperature rises. Due to such characteristics, the voltage Va at the connection point a between the thermistor 2 and the resistor R1 rises as the temperature of the thermistor 2 rises. The connection point a is connected to the non-inverting input terminal of the error amplifier 7. The inverting input terminal of the error amplifier 7 is connected to the positive output terminal of the DC power supply 8. In the DC power supply 8, the negative output terminal is connected to the reference potential point, and the positive output terminal receives the reference voltage VRE.
Output F. In the error amplifier 7, the voltage Va is the reference voltage V
It is a judgment means for judging whether or not the voltage exceeds REF, and it is the voltage Va at the connection point a and the reference voltage V from the DC power supply 8.
A voltage Vb obtained by amplifying the difference from REF with VON as the upper limit is supplied from the output terminal to the first and second control circuits 9 and 10.
Since the amplification factor of the error amplifier 7 is set sufficiently high, the error amplifier 7 sets the voltage Vb from the output terminal to VON when the voltage Va exceeds the reference voltage VREF, and the voltage V
When a does not exceed the reference voltage VREF, the voltage Vb from the output terminal can be considered to be VOFF (about 0V).

The positive output terminal of the DC power supply 6 is connected to the terminal 9a of the first control circuit 9 via the anode / cathode path of the light emitting diode 4. The first control circuit 9 prevents a current from flowing from the light emitting diode 4 to the terminal 9a when the voltage Vb of the error amplifier 7 is VON, and when the voltage Vb of the error amplifier 7 is VOFF, the terminal 9
a is connected to the reference potential point, and the terminal 9a is operated.
The current is allowed to flow from the light emitting diode 4 to the.

When the voltage Vb of the error amplifier 7 is VON, the second control circuit 10 supplies a power supply voltage to the door lock mechanism unit 5 to lock the door lock mechanism unit 5 in the closed state. When the voltage Vb of the error amplifier 7 is VOFF, the door lock mechanism unit 5 unlocks the door.

FIG. 2 is an explanatory view showing the positional relationship between the projection lamp 3 and the thermistor 2 shown in FIG.

The projection lamp 3 is attached to a socket 32 fixed inside the lamp housing. Further, a reflector 31 is attached to the socket 32 so that the light of the projection lamp 3 is reflected on the front surface of the reflector 31, transmitted to the liquid crystal panel, and enlarged and projected on the screen. The thermistor 2 is provided on the back side of the reflector 31, and the temperature T of the projection lamp 3 is detected by the temperature of the thermistor 2.

The operation of this embodiment will be described below with reference to the graphs of FIGS. 3 and 4.

FIG. 3 is a graph showing the relationship between the voltage Va at the connection point a between the thermistor 2 and the resistor R1 and the temperature T of the projection lamp 3. The voltage Va is plotted on the vertical axis and the temperature T is plotted on the horizontal axis. ..

In FIG. 3, the temperature T1 is a predetermined temperature (for example, 40 ° C.) that is safe to touch with the projection lamp 3. The voltage Va increases as the temperature T increases while decreasing the rate of increase, and at the temperature T1, the voltage Va becomes the reference voltage VREF in the DC power supply 8. After this, the voltage Va
Rises as the temperature T rises, further lowering the rate of rise, and approaches the voltage V1 of the DC power supply 6.

FIG. 4 shows the voltage Vb at the output terminal of the error amplifier 7.
3 is a graph showing the relationship between the temperature and the temperature T of the projection lamp 3, in which the voltage Vb is plotted on the vertical axis and the temperature T is plotted on the horizontal axis.

In FIG. 4, the voltage Vb at the output terminal of the error amplifier 7 maintains VOFF until the temperature rises to T1 and rises rapidly to VON when the temperature exceeds T1.

Next, the overall operation of the safety device will be described.

When replacing the projection lamp 3, the worker first turns off the power of the projection lamp 3. Immediately after the power of the projection lamp 3 is turned off, the projection lamp 3 has a dangerous temperature TD (TD> T1) when touched by hand, and the voltage Va at the connection point a between the thermistor 2 and the resistor R1 is the reference. Since it exceeds the voltage VREF, the voltage Vb at the output terminal of the error amplifier 7 becomes VON. As a result, the first control circuit 9 causes the current from the light emitting diode 4 to flow into the terminal 9a.
By such an operation, the light emitting diode 4 emits light to indicate to the operator that the projection lamp 3 cannot be replaced. When the second control circuit 10 is supplied with the voltage VON, the second control circuit 10 supplies a power supply voltage to the door lock mechanism unit 5 to lock the door lock mechanism unit 5 in the closed state. After that, when the temperature of the projection lamp 3 reaches a safe temperature T1 after a lapse of a predetermined time from turning off the power of the projection lamp 3, the voltage Va becomes the reference voltage VREF, and the output terminal of the error amplifier 7 The voltage Vb at VOFF becomes VOFF. As a result, the first control circuit 9 connects the light emitting diode 4 to the terminal 9a.
Do not allow current to flow from. By such an operation, the light emitting diode 4 stops emitting light, and the operator is informed that the projection lamp 3 can be replaced. In addition, the second control circuit 10 includes the door lock mechanism unit 5
The supply of the power supply voltage is stopped and the door lock mechanism unit 5 unlocks the door. Also, the temperature T1 of the projection lamp 3
When the voltage Vb becomes lower than that, the voltage Va becomes lower than the reference voltage VREF and the voltage Vb becomes VOFF. As a result, the first control circuit 9 maintains a state in which the current from the light emitting diode 4 does not flow into the terminal 9a, the light emitting diode 4 does not emit light, and the projection lamp 3 is in a replaceable state. Show to operator. In addition, the second control circuit 10 does not supply the power supply voltage to the door lock mechanism unit 5 and maintains the door lock mechanism unit 5 in the unlocked state. The worker, because the light emitting diode 4 stops emitting light,
When it is judged that the temperature of the projection lamp 3 has fallen below the safe temperature T1 even if it is touched by hand, the unlocked door is opened and the projection lamp 3 is replaced.

According to such an embodiment, when the projection lamp 3 is replaced, the door is automatically locked until the projection lamp 3 cools when the operator touches the projection lamp 3. Therefore, there is no danger of touching the high-temperature projection lamp 3 with hands, and accidents such as burns and incidental accidents can be prevented. Further, since it is possible to accurately know the cooling of the projection lamp 3, there is an effect that it is not necessary to take a waiting time until the projection lamp 3 is cooled more than necessary.

In the embodiment of FIG. 1, the temperature of the projection lamp 3 is detected by using the thermistor 2 as a temperature sensor, but the temperature of the projection lamp 3 is detected by using another temperature sensor such as a thermocouple. It may be configured to do so. Although the light emitting diode 4 is used as the display, another display,
For example, a liquid crystal panel may be used to display whether or not the projection lamp 3 can be replaced.

[0025]

According to the present invention, when the light emitting lamp is replaced, it is possible to automatically prevent the operator from touching the projection lamp until the projection lamp has cooled to a safe temperature, and therefore, it is possible to prevent high temperature projection. There is no danger of touching the operating lamp with hands, and accidents such as burns and incidental accidents can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a safety device for a liquid crystal projector according to the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship between a projection lamp and a thermistor shown in FIG.

FIG. 3 is a graph showing the relationship between the voltage at the connection point between the thermistor and the resistor in FIG. 1 and the temperature of the projection lamp.

4 is a graph showing the relationship between the voltage of the output terminal of the error amplifier of FIG. 1 and the temperature of the projection lamp.

[Explanation of symbols]

 1 Safety Device for Liquid Crystal Projector 2 Thermistor 3 Projection Lamp 4 Light Emitting Diode 5 Door Lock Mechanism 7 Error Amplifier 9 First Control Circuit 10 Second Control Circuit

Claims (1)

[Claims] 1. A temperature sensor for detecting the temperature of a projection lamp of a liquid crystal projector, a determination means for determining whether or not the detection result of the temperature sensor exceeds a predetermined value, and a display of the determination result of the determination means. A lamp safety of a liquid crystal projector, comprising: a display device for performing the above; and a door locking device that locks a door that houses the projection lamp when the determination device determines that the predetermined value is exceeded. apparatus.