1 FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] SCROLL CASING OF CENTRIFUGAL FAN, CENTRIFUGAL FAN, AIR-CONDITIONING APPARATUS AND REFRIGERATION CYCLE APPARATUS INCLUDING THE SCROLL CASING MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. 2 DESCRIPTION Technical Field [0001] The present disclosure relates to a scroll casing that accommodates a fan, a centrifugal fan provided with this scroll casing, an air-conditioning apparatus and a 5 refrigeration cycle apparatus each including this scroll casing. Background Art [0002] Some related-art air conditioning apparatuses have, between an air inlet and an air outlet, a heat exchanger and a centrifugal fan provided with a scroll casing. In 10 such an air-conditioning apparatus, a fan accommodated in the scroll casing rotates to cause air drawn in from the air inlet of the air-conditioning apparatus to flow into the fan along the bell mouth that forms a suction port of the scroll casing. The airflow discharged from the fan is subjected to pressure rising in the scroll casing, discharged from a discharge port of the scroll casing, passes through the heat exchanger, and 15 then blown out from the air outlet of the air-conditioning apparatus into a space to be air-conditioned (see Patent Literature 1, for example). Citation List Patent Literature [0003] 20 Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2005-69177 Summary of Invention Technical Problem [0004] 25 The scroll casing installed in an air-conditioning apparatus with such a configuration suffers from insufficient rising in pressure of airflow since it is impossible to sufficiently enlarge the discharge port due to structural restrictions inside the apparatus. In addition, such inability to sufficiently enlarge the discharge port limits a range of passage of the airflow discharged from the discharge port when it passes 30 3 through the heat exchanger. Therefore, if the scroll casing tilts or the like for some reasons and, as a result, the direction of the discharge port of the airflow changes, the airflow cannot pass through some areas of the heat exchanger, whereby a drift flow occurs. Such a drift flow may result in inefficient heat exchange. [0005] 5 For an air-conditioning apparatus, there is a need to improve the workability in assembling a centrifugal fan into a housing of the air-conditioning apparatus, and under such circumstances, a scroll casing having a configuration that can achieve this improvement in workability has been required. [0006] 10 The present disclosure has been made to solve the above-mentioned problems and an object thereof is to obtain a scroll casing capable of attaining a pressure rising effect and a drift flow suppression effect, and also can improve workability in assembly, as well as to obtain a centrifugal fan, an air-conditioning apparatus and a refrigeration cycle apparatus provided with the scroll casing. 15 Solution to Problem [0007] The scroll casing for a centrifugal fan according to the present disclosure includes a fan configured to generate airflow, the scroll casing comprising: a scroll portion configured to accommodate the fan and guide an airflow generated by the fan 20 in a spiral shape; a discharge portion provided at a winding end portion of the scroll portion and having a discharge port configured to cause airflow to be discharged; and a tongue portion provided at a part connecting a winding start portion of the scroll portion and the discharge portion, wherein the discharge portion forms a flow passage of which an area of a cross section crossing orthogonally to a flow direction 25 of the airflow gradually enlarges toward the discharge port, an extended plate formed so as to extend from the winding end portion in the discharge portion is, in a cross section obtained by cutting the extended plate in a thickness direction thereof, inclined relative to an inner wall surface of a housing configured to accommodate the centrifugal fan, and the extended plate has a change point at which an enlargement 30 4 ratio of the area of the cross section on a downstream side is increased so as to be larger than that on an upstream side due to a change in degree of inclination, and wherein, when a portion on the upstream side than the change point is named as a first portion and a portion on the downstream side than the change point is named as a second portion, an angle θ1 and an angle θ2 satisfy a relationship of either 0≦5 θ2<θ1 or 0<θ2≦θ1, where θ1 is defined by the first portion and a virtual line that is parallel to the inner wall surface of the housing and passes the change point, and the angle θ2 is defined by the second portion and the virtual line, and a distance L1 and a distance L2 satisfy a relationship of L2L1 as a comparative example. [0037] 15 Fig. 4 is an assembly diagram explaining the assembly of an air-conditioning apparatus provided with a comparative scroll casing. Fig. 5 is an assembly diagram explaining the assembly of the air-conditioning apparatus provided with the scroll casing according to Embodiment 1. Although an explanation has not been made so far, the scroll casing is divided into an upper portion and a lower portion so as to 20 include two portions, i.e., a first case portion having the discharge portion 42 and a second case portion. In the comparative example, as illustrated in Fig. 4(a), a first case portion 410A of a scroll casing 41A is inserted into the housing 11, and a discharge portion 42A of the first case portion 410A is inserted toward the opening 13a of a partition plate 13 in 25 a direction indicated by the arrow. At this time, if the relationship is L2>L1, as illustrated in Fig. 4(b), an end portion 43Aa on the downstream side of the first case portion 410A interferes with the housing 11. [0038] To avoid such interference, it suffices that the opening 13a of the partition plate 30 14 13 be enlarged. However, if the opening 13a of the partition plate 13 is enlarged, in a state where the scroll casing 41A is installed in the housing 11, a gap is generated between the periphery of the opening 13a of the partition plate 13 and the outer circumference of the discharge portion 42A, and this gap is required to be closed with a separate component. 5 [0039] On the other hand, in the scroll casing 4 according to Embodiment 1, as shown in Fig. 5(a), a first case portion 410 of the scroll casing 4 is inserted into the housing 11, and the discharge portion 42 of the first case portion 410 is inserted in the direction shown by the arrow toward the opening 13a of the partition plate 13. At this 10 time, in the scroll casing 4 of Embodiment 1, due to the relationship of L2