Humidifying apparatus for an air-conditioning equipment

A humidifying apparatus for equipment for conditioning the air of vehicle has a humidity detecting circuit and a humidifying device including a spray nozzle. The humidifying device is intermittently operated by a control device. Thus, humidity in the vehicle cabin can be controlled so as to be maintained at a desired value while keeping the humidity in the cabin uniform.

This invention relates to a humidifying apparatus for equipment mounted on 
a vehicle to condition the air therein. 
It has been considered necessary to control the humidity during 
conditioning the air in a car, especially when heating the air. However, 
since a spatial volume of the car is small and a configuration of the 
space is complicated, it may become highly humid in the vicinity of a 
humidifier and low in humidity at a position remote from the humidifier if 
a humidifier having a simple control system such as that typically used in 
a household humidifier is employed. This may cause trouble in an 
electrical system in the car space where a plurality of wirings for the 
electrical system are arranged. For this reason, an apparatus for 
conditioning the air in a car is often restrained from carrying out 
humidification. In addition, it is required to sense the humidity to 
control the humidifying operation. This involves such problems that a 
humidity is one of the most difficult physical properties to measure and 
that a humidity sensor is liable to be in an atmosphere containing various 
components other than water vapor. This is also a reason why 
humidification has not been carried out with much success in a car 
heretobefore. 
It is therefore an object of the present invention to provide a humidifying 
apparatus for equipment conditioning air in a motor vehicle which is 
capable of attaining desirable humidification control. 
It is another object of the present invention to provide a humidifying 
apparatus for such equipment which can control the humidity in the cabin 
so as to be maintained at desired value while keeping the humidity in the 
cabin uniform. 
It is still another object of the present invention to provide a 
humidifying apparatus for such equipment which can be operated in stable 
condition even if the apparatus is located in a contaminated environment. 
According to the present invention, a humidifying apparatus for equipment 
conditioning air in a vehicle has a humidity detecting circuit and a 
humidifying device including a spray nozzle. The humidifying device is 
operated intermittently by a control device on the basis of a detecting 
signal from the humidity detecting circuit in order that a humidity in the 
vehicle is maintained a given set value. Preferably, the spray nozzle is 
located before an evaporator of the equipment. The operation of the 
humidifying device is intermittently carried out during a given period of 
time at given time intervals. Thus, a humidity in the cabin can be 
controlled so as to be maintained at a desired value while keeping the 
humidity in the cabin uniform. Furthermore, it can be effectively 
prevented that only a particular portion of the cabin becomes highly humid 
by employing a single humidity sensor.

The present invention will now be described in detail referring to an 
embodiment illustrated in the accompanying drawings. 
FIG. 1 illustrates one embodiment of equipment for conditioning the air of 
a vehicle and including therein a humidifying apparatus according to the 
present invention. The equipment 1 comprises a blower 2, an evaporator 3 
and a heater core 4 arranged as illustrated in FIG. 1. An intake vent 6 of 
a duct 5 has an opening 7 communicating with the inside of the car and an 
opening communicating with the outside of the car. A shutter 9 is provided 
at the intake vent 6 to selectively close either of the openings 7 and 8. 
By operating the shutter 9, air in the car or air outside the car is 
selectively introduced into the duct 5 by the blower 2. In this 
connection, it is to be noted that the shutter 9 may be positioned at the 
position shown in FIG. 1 to take a mixture of the air in the car and the 
air outside the car into the duct 5. In FIG. 1, numeral 10 designates a 
shutter for changing a path of air flow within the duct 5 to effect 
changeover between heating and cooling. 
The equipment 1 is provided with a humidifier 11 to control the humidity in 
the cabin of the car. The humidifier 11 includes a humidifying device 12 
for spraying water into the duct 5 to impart moisture to the air in the 
duct 5 and a control device 13 for controlling the operation of the 
humidifying device 12 so as to keep the humidity within the cabin at a 
desired value. The humidifying device 12 comprises a water tank 14, an air 
blowing motor 15 and a spray nozzle 19 connected to a water pipe 17 for 
supplying the water 16 in the water tank 14, and an air pipe 18 connected 
to the air blowing motor 15. The spray nozzle 19 is disposed before the 
evaporator 3, i.e. on the windward side of the evaporator 3. In the 
embodiment as illustrated, the spray nozzle 19 is fixed on a wall of the 
duct 5 between the blower 2 and the evaporator 3 so that it can spray the 
water 16 in the water tank 14 into the duct 5 with air from the motor 15. 
In this connection, it is to be noted that since the spray nozzle 19 is 
located before the evaporator 3, large particles of water strike against 
the evaporator 3 and drain out through a drain pipe 20 and only small 
particles of atomized components are fed into the cabin through blow-off 
openings 21. This can effectively prevent waterdrops from falling onto a 
floor through the blow-off openings 21 of the duct 5. 
A humidity sensor 22 is fixed at a suitable position in the cabin to keep 
the humidity in the cabin at a predetermined value. The humidity sensor 22 
and the control device 13 cooperate to control the driving of the motor 15 
in the on-off control mode as will be mentioned in detail below. 
FIG. 2 is a circuit diagram of an electrical circuit of the humidifier 11 
including the humidity sensor 22. The control device 13 includes a 
humidity detecting circuit 24 mainly comprised of the humidity sensor 22 
and operational amplifiers A.sub.1 and A.sub.2 for detecting whether a 
humidity at a place where the humidity sensor 22 is located is higher or 
lower than the predetermined value. In the humidity detecting circuit 24, 
a series circuit of the sensor 22 and a resistor R.sub.1 is connected in 
parallel to a d.c. power source 23. A resistance value of the sensor 22 
varies depending on the humidity at the place where the sensor is 
disposed, so that a potential V.sub.1 at a junction M of the sensor 22 and 
the resistor R.sub.1 varies. This variation in potential is amplified by 
the operational amplifier A.sub.1 and applied to an inverting input 
terminal of the operational amplifier A.sub.2 functioning as a comparator. 
As the sensor 22, there is employed a ceramic humidity sensor utilizing a 
change in conductivity due to moisture adhering in pores of a ceramic of a 
metallic oxide. This is, this ceramic humidity sensor detects water 
absorbed throughout its bulk, thus making it less subject to the effect of 
surface contamination and more stable than the surface-layer type, and 
moreover with a quick response nearly equal to that of the surface-layer 
type. 
The potential V.sub.1 is raised according to a rise in relative humidity. 
To a non-inverting input terminal of the operational amplifier A.sub.2 is 
applied a potential V.sub.2 at a junction N of resisters R.sub.4 and 
R.sub.5, so that when the humidity at the place where the sensor 22 is 
disposed is low, a potential at an output of the operational amplifier 
A.sub.1 is lower than the potential V.sub.2. Accordingly, an output level 
of the operational amplifier A.sub.2, i.e. a level of a detection signal 
S.sub.1, is high. On the other hand, when the humidity at the place where 
the sensor 22 is located is high, the potential at the output of the 
operational amplifier A.sub.1 is raised to above the potential V.sub.2 and 
the level of the detection signal S.sub.1 becomes low. 
Therefore, the value of the potential V.sub.2 may suitably be selected to 
lower the level of the detection signal S.sub.1 when the humidity at the 
place where the sensor 22 is located is raised to a desired value. The 
detection signal S.sub.1 is supplied to one input of an AND gate 25. 
Another input of the AND gate 25 receives a pulse signal S.sub.2 supplied 
from a pulse generator 26 and having a given period and a given duty 
ratio. The AND gate 25 is opened only when the pulse signal S.sub.2 is at 
a high level to pass the detection signal S.sub.1 therethrough. 
In the present embodiment, the pulse signal S.sub.2 is a repetitive pulse 
signal having a period T of 30 seconds and a high-level duration of 5 
seconds. Therefore, an output signal S.sub.3 of the AND gate 25 remains at 
a low level when the level of the detection signal S.sub.1 is low, while 
it is kept at a high level for 5 seconds every 30 seconds during the 
period when the level of the detection signal S.sub.1 is high. The output 
signal S.sub.3 is supplied to a driving circuit 27 for the motor as an 
on-off control signal so that the motor 15 is controlled to be driven only 
during a period when the output signal S.sub.3 is at a high level. 
Thus, in accordance with such an arrangement, when the humidity at the 
place where the sensor 22 is disposed is lowered to below the 
predetermined value, the level of the signal S.sub.1 becomes high and the 
humidifying device 12 is intermittently driven according to the repetitive 
period and the duty ratio of the pulse signal S.sub.2. Therefore, moisture 
is intermittently supplied on the air discharged through the blow-off 
openings 21, so that humidification can be effected uniformly in the 
cabin, preventing humidity in the vicivity of the blow-off openings from 
being extremely high as compared with the humidity at places remote from 
the blow-off openings as in the case with the conventional humidifying 
apparatus. 
To obtain a pulse signal as illustrated in FIG. 3, a square wave signal 
S.sub.10 having a period of 30 seconds is generated by a square wave 
oscillator 30 as illustrated in FIG. 4. The signal S.sub.10 is 
differentiated by a differentiating circuit 31. An output signal S.sub.11 
from the differentiating circuit 31 is then rectified by a rectifying 
circuit 32 including a diode and a rectified differentiation signal 
S.sub.12 is applied as a trigger signal to a mono-stable multivibrator 33. 
In accordance with the present invention, as mentioned above, a humidity in 
the cabin can be controlled so as to be maintained at a desired value 
while keeping the humidity in the cabin uniform. Thus, it can be 
effectively prevented that only a particular portion of the cabin becomes 
highly humid even if only one humidity sensor is employed.