In recent years, there is available a three-zone-type air conditioning system which is configured to independently cool and heat a left zone, a right zone and a rear seat zone of a vehicle room. In the three-zone-type air conditioning system, as illustrated in FIG. 1, a left path 14, a right path 16 and a rear seat path 18 are formed within an air conditioner case 10. Left, right and rear seat temperature doors 20, 22 and 24 are installed in the left path 14, the right path 16 and the rear seat path 18, respectively. The flow rates of a cold air or a hot air in the left path 14, the right path 16 and the rear seat path 18 are independently adjusted by independently controlling the left, right and rear seat temperature doors 20, 22 and 24.
The cold air or the hot air having an adjusted flow rate and flowing through the left path 14 is supplied to a left zone of a vehicle room. The cold air or the hot air having an adjusted flow rate and flowing through the right path 16 is supplied to a right zone of a vehicle room. The cold air or the hot air having an adjusted flow rate and flowing through the rear seat path 18 is supplied to a rear seat zone of a vehicle room. Thus, the left zone, the right zone and the rear seat zone of the vehicle room are independently cooled or heated.
In this regard, the left, right and rear seat temperature doors 20, 22 and 24 are rotated in response to a change in an indoor air temperature, an outdoor air temperature or a sunshine amount, whereby the opening positions thereof are automatically adjusted. Thus, the left, right and rear seat temperature doors 20, 22 and 24 automatically control the temperature of an air introduced into the vehicle room, in conformity with the indoor air temperature, the outdoor air temperature or the sunshine amount. Accordingly, regardless of the indoor air temperature, the outdoor air temperature or the sunshine amount, the temperature of an air introduced into the vehicle room is always controlled at a constant temperature in conformity with the temperature set by a user.
The three-zone-type air conditioning system further includes an air volume distribution door 30 installed at the upstream side of the left path 14 and the right path 16. The air volume distribution door 30 is configured to rotate between an entrance 14a of the left path 14 and an entrance 16a of the right path 16, thereby adjusting the opening degrees of the left path 14 and the right path 16. Thus, the air volume distribution door 30 adjusts the volumes of the air introduced from a main blower 40 into the left path 14 and the right path 16, thereby controlling the volumes of the cold air or the hot air supplied to the left zone and the right zone of the vehicle room.
The three-zone-type air conditioning system further includes a rear seat auxiliary blower 50 installed in the rear seat path 18. The rear seat auxiliary blower 50 is configured to further increase the volume and pressure of the cold air or the hot air flowing along the rear seat path 18, thereby further increasing the volume and pressure of the cold air or the hot air supplied to the rear seat zone. This helps enhance the ability to cool or heat the rear seat zone.
However, the conventional air conditioning system described above has the following two problems.
Firstly, if the opening positions of the left and right temperature doors 20 and 22 are changed in a state in which the opening degrees of the left and right paths 14 and 16 are controlled at a specific ratio by the air volume distribution door 30, the flow route of an air flowing toward a heater core 9 is changed and the static pressure difference between the left and right paths 14 and 16 is changed. This poses a problem in that the air volume distribution ratio in the left and right paths 14 and 16 is changed.
For example, if the opening degrees of the left and right paths 14 and 16 are controlled at a ratio of 3:7 by the air volume distribution door 30, a deviation is generated between the static pressures of the left and right paths 14 and 16 due to the difference in the opening degrees (cross-sectional areas) of the left and right paths 14 and 16.
In this state, if the opening position of each of the left and right temperature doors 20 and 22 is changed from a maximum cooling position X to a maximum heating position Y as illustrated in FIG. 2, the air existing in each of the left and right paths 14 and 16 passes through the heater core 19 as an air-resistant body. Thus, the static pressures at the upstream side of the left and right paths 14 and 16 grow larger. As a result, the static pressure difference between the left and right paths 14 and 16 is changed.
Particularly, the static pressures of the air vary depending on the cross-sectional areas of the paths. In the left and right paths 14 and 16 having different opening degrees (cross-sectional areas), the static pressure change rates with respect to the prior ones differ from each other due to the flow of the air through the heater core 19. The air volume distribution ratio of the air introduced from the main blower 40 into the left and right paths 14 and 16 is changed by the mutually-different static pressure change rates.
For example, due to the flow of the air through the heater core 19, the static pressure change rate in the left path 14 having a small opening degree (cross-sectional area) is smaller than the static pressure change rate in the right path 16 having a large opening degree (cross-sectional area). Since the static pressure change rate is small in the left path 14, the amount of the air introduced into the left path 14 becomes larger than before. As a result, the air volume distribution ratio of the air introduced from the main blower 40 into the left and right paths 14 and 16 is changed.
For that reason, the air volume distribution ratio of the air flowing toward the left and right paths 14 and 16 is not accurately controlled at an original control value. Consequently, the volumes of the cold air or the hot air supplied to the left and right zones of the vehicle room are not controlled at the user's desire. As a result, the comfort in the vehicle room decreases.
Secondly, if the rotation speed level of the rear seat auxiliary blower 50 is changed by manual control or automatic control, the amount of the air introduced into the rear seat path 18 is also changed. Due to the change in the amount of the air introduced into the rear seat path 18, the amounts of the air introduced into the left and right paths 14 and 16 are changed. Thus, the amounts of the cold air or the hot air blown toward the left and right zones of the vehicle room are changed. This poses a problem in that the ability to cool or heat the left and right zones of the vehicle room is reduced.
In particular, if the rotation speed level of the rear seat auxiliary blower 50 grows higher, the amount of the air introduced into the rear seat path 18 increases. Due to the increase of the amount of the air introduced into the rear seat path 18, the amount of the air introduced into the left and right paths 14 and 16 decreases. Thus, the amount of the cold air or the hot air blown toward the left and right zones of the vehicle room is reduced. This poses a problem in that the ability to cool or heat the left and right zones of the vehicle room is sharply reduced.
In the conventional air conditioning system, if the rotation speed level of the rear seat auxiliary blower 50 is changed, the static pressures acting in the left and right paths 14 and 16 are also changed. Due to the change in the static pressures in the left and right paths 14 and 16, the static pressure difference between the left and right paths 14 and 16 grows larger. As a result, the air volume distribution ratio in the left and right paths 14 and 16 is changed.
More specifically, the opening degrees (cross-sectional areas) of the left and right paths 14 and 16 are differently controlled by the air volume distribution door 30. Thus, a static pressure difference is generated between the left and right paths 14 and 16.
At this time, if the rotation speed level of the rear seat auxiliary blower 50 is changed, the static pressures acting in the left and right paths 14 and 16 are also changed. Due to this static pressure change, the static pressure difference between the left and right paths 14 and 16 is also changed.
In particular, the static pressure of an air varies depending on the cross-sectional area of a path. Therefore, in the left and right paths 14 and 16 having different opening degrees (cross-sectional areas), the static pressure change rates attributable to the change in the rotation speed level of the rear seat auxiliary blower 50 differ from each other. Due to the mutually-different static pressure change rates, the air volume distribution ratio of the air introduced from the main blower 40 into the left and right paths 14 and 16 is changed.
For example, due to the change in the rotation speed level of the rear seat auxiliary blower 50, the static pressure change rate in the left path 14 having a small opening degree (cross-sectional area) is smaller than the static pressure change rate in the right path 16 having a large opening degree (cross-sectional area). Since the static pressure change rate is small in the left path 14, the amount of the air introduced into the left path 14 becomes larger than before. As a result, the air volume distribution ratio of the air introduced from the main blower 40 into the left and right paths 14 and 16 is changed.
For that reason, the air volume distribution ratio of the air flowing toward the left and right paths 14 and 16 is not accurately controlled at an original control value. Consequently, the volumes of the cold air or the hot air supplied to the left and right zones of the vehicle MOM are not controlled at the user's desire. As a result, the comfort in the vehicle room decreases.