COMPRESSOR BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a compressor. Description of the Related Art [0002] Conventionally a compressor has a circular tube-shaped connecting pipe communicating with a compression chamber that is press fitted at the side of a cylinder inside which the compression chamber is formed. For example, a high pressure shell-type compressor in whose hermetic container is produced a discharge pressure, is provided with a connecting pipe that connects the low pressure side of the refrigeration cycle circuit and the compression chamber. Also, for example, a low pressure shell-type compressor in whose hermetic container is produced a suction pressure is provided with a connecting pipe that connects the high pressure side of the refrigeration cycle circuit and the compression chamber. And also, for example, in a multistage compressor in which a refrigerant is compressed sequentially in a plurality of compression chambers, the compression chamber on the lower stage side and the compression chamber on the higher stage side are connected by a connecting pipe. [0003] Incidentally, if the thickness of the cylinder can be reduced, the compressor can be made smaller or can be made to have multiple cylinders without increasing the shell capacity of the compressor too much. Also, in a rotary compressor, it is possible to increase the diameter of the inner surface of the cylinder or the diameter of the rotary piston without changing the capacity of the compression chamber by reducing the thickness of the cylinder, and so it is possible to reduce leakage of the refrigerant from the high-pressure space to the low-pressure space in the compression chamber. However, if the thickness of the cylinder is reduced like this, the circular tube-shaped connecting pipe and the through hole in the cylinder into which to press fit the connecting pipe (namely, the through hole communicating with the compression chamber) must be reduced in diameter according to the thickness of the cylinder, resulting in a reduction in the flow rate of the refrigerant that flows through the compression chamber. [0004] Accordingly, there has been proposed a compressor wherein a connecting pipe to communicate with the compression chamber and a through hole in the cylinder into which to press fit the connecting pipe are formed in an oval shape in cross section (see Patent Literature 1). By forming the connecting pipe and the through hole in the cylinder into which to press fit the connecting pipe to be in an oval shape in cross section, it is possible to secure an enough flow passage cross section in the connecting pipe and the through hole in the cylinder into which the connecting pipe is press fitted, and so the thickness of the cylinder can be reduced with preventing a decrease in the flow rate of the refrigerant flowing through the compression chamber. [0005] [Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2010-121481 SUMMARY OF THE INVENTION [0006] However, with the through hole in the cylinder into which to press fit the connecting pipe being in an oval shape in cross section, when the connecting pipe is press fitted into the through hole in the cylinder, the flat part of the connecting pipe may be deformed toward the inside of the connecting pipe. Hence, the seal ability between the connecting pipe and the through hole in the cylinder into which the connecting pipe is press fitted may be worse. Therefore, there is the problem that the gas leakage loss at the time of compression is greater, resulting in a decrease in the performance of the compressor. [0007] Although there is a method that has conventionally been employed in which sealing is performed by using elastic material such as an O-ring or seal tape in order to secure seal ability, this method is not desirable considering workability and cost. Also, in the case of a compressor, when connection is made between a connecting pipe and, for example, a pipe on the low pressure side of a refrigeration cycle circuit, the connection is made by welding. For this reason, in the case of a compressor, if the sealing method using elastic material such as an O-ring or seal tape is employed, there will arise the problem that the elastic material deteriorates due to the heat during welding, resulting in a decrease in the reliability of the compressor. [0008] The present invention was made to solve the problems as described above, and an object thereof is to provide a compressor wherein while the through hole in the cylinder into which to press fit the connecting pipe is an oval shape in cross section, the seal ability between the connecting pipe and the through hole in the cylinder can be secured without using elastic material such as an O-ring or seal tape. [0009] A compressor according to the present invention comprises a cylinder inside which a compression chamber is formed; and a connecting pipe that is attached to the cylinder and communicates with the compression chamber. The cylinder has a through hole oval-shaped in cross section which is formed extending through from the side of the cylinder to the compression chamber and whose longitudinal direction is along the circumferential direction of the cylinder. At least one end of the connecting pipe is formed in an oval shape in cross section, and the one end is press fitted into the through hole with a press-fit interference of 0.05 mm or less, so that the connecting pipe communicates with the compression chamber. Letting A be a wall thickness of a portion of the cylinder abutting the linear part of the through hole, B be a length in the longitudinal direction in a cross section of the through hole, and C be a length in the transverse direction in the cross section of the through hole, where these sizes are ones before the connecting pipe is press fitted into the through hole, then for the connecting pipe whose wall thickness t satisfies 0 mm < t S 1.6 mm, 0 < A x B / C £ 3.38 is satisfied. For the connecting pipe whose wall thickness t satisfies 0 mm < t s 1 mm, 0 < A x B / C £ 2.88 is satisfied. For the connecting pipe whose wall thickness t satisfies 0 mm < t £ 0.4 mm, 0 < A x B / C £ 2.38 is satisfied. [0010] And, a compressor according to the present invention comprises a cylinder inside which a compression chamber is formed; and a connecting pipe that is attached to the cylinder and communicates with the compression chamber. The cylinder has a through hole oval-shaped in cross section which is formed extending through from the side of the cylinder to the compression chamber and whose longitudinal direction is along the circumferential direction of the cylinder. At least one end of the connecting pipe is formed in an oval shape in cross section, and the one end is press fitted into the through hole with a press-fit interference of 0.1 mm or less, so that the connecting pipe communicates with the compression chamber. Letting A be a wall thickness of a portion of the cylinder abutting the linear part of the through hole, B be a length in the longitudinal direction in a cross section of the through hole, and C be a length in the transverse direction in the cross section of the through hole, where these sizes are ones before the connecting pipe is press fitted into the through hole, then for the connecting pipe whose wall thickness t satisfies 0 mm < t < 1.6 mm, 0 < A x B / C< 3.28 is satisfied. For the connecting pipe whose wall thickness t satisfies 0 mm < t < 1 mm, 0 < A x B / C< 2.83 is satisfied. For the connecting pipe whose wall thickness t satisfies 0 mm < t <, 0.4 mm, 0 < A x B / C< 2.37 is satisfied. [0011] And, a compressor according to the present invention comprises a cylinder inside which a compression chamber is formed; and a connecting pipe that is attached to the cylinder and communicates with the compression chamber. The cylinder has a through hole oval-shaped in cross section which is formed extending through from the side of the cylinder to the compression chamber and whose longitudinal direction is along the circumferential direction of the cylinder. At least one end of the connecting pipe is formed in an oval shape in cross section, and the one end is press fitted into the through hole with a press-fit interference of 0.15 mm or less, so that the connecting pipe communicates with the compression chamber. Letting A be a wall thickness of a portion of the cylinder abutting the linear part of the through hole, B be a length in the longitudinal direction in a cross section of the through hole, and C be a length in the transverse direction in the cross section of the through hole, where these sizes are ones before the connecting pipe is press fitted into the through hole, then for the connecting pipe whose wall thickness t satisfies 0 mm < t S 1.6 mm, 0 < A x B / C £ 3.2 is satisfied. For the connecting pipe whose wall thickness t satisfies 0 mm < t £ 1 mm, 0 < A x B / C £ 2.8 is satisfied. For the connecting pipe whose wall thickness t satisfies 0 mm < t s 0.4 mm, 0 3.38, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0036] A straight line F1 in Fig. 7 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 under the conditions of press-fit interference D being 0.1 mm and wall thickness t of connecting pipe 12 being 1.6 mm, with the wall thickness A of cylinder flat area 11c, length B in the longitudinal direction in the cross section of gas sucking hole 11a, and length C in the transverse direction in the cross section of gas sucking hole 11 a as indexes. [0037] This straight line F1 is represented by the following relational equation 2. [0038] [Expression 2] [0039] In this relational equation 2, Y becomes 0 when A x B / C = 3.28. It can be seen from this that if press-fit interference D is 0.1 mm and the wall thickness t of connecting pipe 12 is 1.6 mm, when A x B / C = 3.28, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 3.28, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C > 3.28, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0040] A straight line G1 in Fig. 7 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 under the conditions of press-fit interference D being 0.15 mm and wall thickness t of connecting pipe 12 being 1.6 mm, with the wall thickness A of cylinder flat area 11 c, length B in the longitudinal direction in the cross section of gas sucking hole 11a, and length C in the transverse direction in the cross section of gas sucking hole 11a as indexes. [0041] This straight line G1 is represented by the following relational equation 3. [0042] [Expression 3] [0043] In this relational equation 3, Y becomes 0 when A x B / C = 3.2. It can be seen from this that if press-fit interference D is 0.15 mm and the wall thickness t of connecting pipe 12 is 1.6 mm, when A x B / C = 3.2, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 3.2, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 be pomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C > 3.2, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0044] Fig. 8 is a characteristic diagram showing the results of the CAE analysis when the wall thickness t of the connecting pipe in the embodiment of the prevent invention is 1 mm. A straight line E2 in Fig. 8 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 in Fig. 7 under the conditions of press-fit interference D being 0.05 mm and wall thickness t of connecting pipe 12 being 1 mm, with the wall thickness A of cylinder flat area 11c, length B in the longitudinal direction in the cross section of gas sucking hole 11 a, and length C in the transverse direction in the cross section of gas sucking hole 11a as indexes. [0045] This straight line E2 is represented by the following relational equation 4. [0046] [Expression 4] [0047] In this relational equation 4, Y becomes 0 when A x B / C = 2.88. It can be seen from this that if press-fit interference D is 0.05 mm and wall thickness t of connecting pipe 12 is 1 mm, when A x B / C = 2.88, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 2.88, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C > 2.88, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being, created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0048] A straight line F2 in Fig. 8 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 in Fig. 7 under the conditions of press-fit interference D being 0.1 mm and wall thickness t of connecting pipe 12 being 1 mm, with the wall thickness A of cylinder flat area 11c, length B in the longitudinal direction in the cross section of gas sucking hole 11 a, and length C in the transverse direction in the cross section of gas sucking hole 11 a as indexes. [0049] This straight line F2 is represented by the following relational equation 5. [0050] [Expression 5] [0051] In this relational equation 5, Y becomes 0 when A x B / C = 2.83. It can be seen from this that if press-fit interference D is 0.1 mm and wall thickness t of connecting pipe 12 is 1 mm, when A x B / C = 2.83, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 2.83, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C > 2.83, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0052] A straight line G2 in Fig. 8 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 in Fig. 7 under the conditions of press-fit interference D being 0.15 mm and wall thickness t of connecting pipe 12 being 1 mm, with the wall thickness A of cylinder flat area 11 c, length B in the longitudinal direction in the cross section of gas sucking hole 11a, and length C in the transverse direction in the cross section of gas sucking hole 11 a as indexes. [0053] This straight line G2 is represented by the following relational equation 6. [0054] [Expression 6] [0055] In this relational equation 6, Y becomes 0 when A x B / C = 2.8. It can be seen from this that under the conditions of press-fit interference D being 0.15 mm and wall thickness t of connecting pipe 12 being 1 mm, when A x B / C = 2.8, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 2.8, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C > 2.8, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0056] Fig. 9 is a characteristic diagram showing the results of the CAE analysis when the wall thickness t of the connecting pipe in the embodiment of the prevent invention is 0.4 mm. A straight line E3 in Fig. 9 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 in Fig. 7 under the conditions of press-fit interference D being 0.05 mm and wall thickness t of connecting pipe 12 being 0.4 mm, with the wall thickness A of cylinder flat area 11c, length B in the longitudinal direction in the cross section of gas sucking hole 11a, and length C in the transverse direction in the cross section of gas sucking hole 11 a as indexes. [0057] This straight line E3 is represented by the following relational equation 7. [0058] [Expression 7] [0059] In this relational equation 7, Y becomes 0 when A x B / C = 2.38. It can be seen from this that under the conditions of press-fit interference D being 0.05 mm and wall thickness t of connecting pipe 12 being 0.4 mm, when A x B / C = 2.38, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 2.38, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C > 2.38, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0060] A straight line F3 in Fig. 9 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 in Fig. 7 under the conditions of press-fit interference D being 0.1 mm and wall thickness t of connecting pipe 12 being 0.4 mm, with the wall thickness A of cylinder flat area 11 c, length B in the longitudinal direction in the cross section of gas sucking hole 11 a, and length C in the transverse direction in the cross section of gas sucking hole 11a as indexes. [0061] This straight line F3 is represented by the following relational equation 8. [0062] [Expression 8] [0063] In this relational equation 8, Y becomes 0 when A x B / C = 2.37. It can be seen from this that under the conditions of press-fit interference D being 0.1 mm and wall thickness t of connecting pipe 12 being 0.4 mm, when A x B / C = 2.37, the mode deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 2.37, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C > 2.37, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0064] A straight line G3 in Fig. 9 shows the relation of the amount of deformation Y of connecting pipe 12, obtained by the same method as for the straight line E1 in Fig. 7 under the conditions of press-fit interference D being 0.15 mm and wall thickness t of connecting pipe 12 being 0.4 mm, with the wall thickness A of cylinder flat area 11c, length B in the longitudinal direction in the cross section of gas sucking hole 11a, and length C in the transverse direction in the cross section of gas sucking hole 11 a as indexes. [0065] This straight line G3 is represented by the following relational equation 9. [0066] [Expression 9] [0067] In this relational equation 9, Y becomes 0 when A x B / C = 2.35. It can be seen from this that under the conditions of press-fit interference D being 0.15 mm and wall thickness t of connecting pipe 12 being 0.4 mm, when A x B / C = 2.35, the mode of deformation of the area around the gas sucking hole 11 a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (a), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C < 2.35, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (b), so that the seal ability between first cylinder 2a and connecting pipe 12 is secured. Also, it can be seen that when A x B / C> 2.35, the mode of deformation of the area around the gas sucking hole 11a of first cylinder 2a and of connecting pipe 12 becomes as shown in Fig. 4 (c), so that a gap being created between connecting pipe 12 and cylinder flat area 11c, no seal between first cylinder 2a and connecting pipe 12 is created. [0068] Namely, it can be seen from Figs. 7 through 9 and the above relational equations 1 through 9 that as the press-fit interference D becomes smaller (in other words, as the deforming load imposed on the flat part of connecting pipe 12 becomes smaller), A x B / C becomes greater. Also, as the wall thickness of connecting pipe 12 becomes greater (in other words, as the strength of the flat part of connecting pipe 12 becomes greater), A x B / C becomes greater. More specifically, it can be seen that in the case of press-fit interference D being 0.05 mm or less (0 < D < 0.05 mm), the seal ability between first cylinder 2a and connecting pipe 12 can be secured by making 0 < A x B / C < 3.38 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t < 1.6 mm, by making 0 < A x B / C < 2.88 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t < 1 mm, and by making 0 < A x B / C < 2.38 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t< 0.4 mm. Also, it can be seen that in the case of press-fit interference D being 0.1 mm or less (0 < D < 0.1 mm), the seal ability between first cylinder 2a and connecting pipe 12 can be secured by making 0 < A x B / C < 3.28 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t < 1.6 mm, by making 0 < A x B / C < 2.83 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t < 1 mm, and by making 0 < A x B / C < 2.37 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t < 0.4 mm. Also, it can be seen that in the case of press-fit interference D being 0.15 mm or less (0 < D < 0.15 mm), the seal ability between first cylinder 2a and connecting pipe 12 can be secured by making 0 < A x B / C < 3.2 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t < 1.6 mm, by making 0 < A x B / C <2.8 satisfied if wall thickness t of the connecting pipe satisfies 0 mm < t <1 mm, and by satisfying 0