Description A Structure for Mounting Magnetic Steel of Motor Technical Field The invention relates to a structure for mounting magnetic steel of a motor, which belongs to the technical field of production and manufacturing of motors. Background of the Invention In the prior art, magnetic steel of a motor is often bonded on the inner wall of a housing through glue, and then a spring clamp is arranged between the adjacent magnetic steel for positioning between the magnetic steel in the circumferential direction. The mounting way of the magnetic steel has the problems that the assembly is more difficult, the environmental protection is poorer, and the magnetic steel becomes loose or falls off and the like because the glue is easy to be heated and molten during the operation process of the motor. Summary of the Invention The invention aims at providing a structure for mounting magnetic steel of a motor, which is relatively convenient in assembly, better in 1 environmental protection and reliable and precise in positioning of the magnetic steel, and can further solve the problems that the existing magnetic steel mounting structure is more difficult to assemble and poorer in environmental protection, and the magnetic steel becomes loose or falls off and the like because glue is easy to be heated and molten during the operation process of the motor. The above technical purpose of the invention is mainly solved through the following technical scheme: the structure for mounting the magnetic steel of the motor comprises a housing and the magnetic steel which is uniformly arranged on the inner wall of the housing at intervals, and the structure is characterized in that a positioning sheet is arranged between the adjacent magnetic steel, the axial length of each positioning sheet is smaller than the axial length of the magnetic steel, each positioning sheet is axially centered and arranged between the adjacent magnetic steel, and the positioning sheets are connected with the housing through screws; and annular positioning clamps are respectively arranged at two ends of the inner wall of the housing, convex heads protruding axially are respectively formed on the annular positioning clamps corresponding to the position between the adjacent magnetic steel, the convex heads are tightly matched between the adjacent magnetic steel, and the parts of the annular positioning clamps, which are correspondingly positioned between the convex heads, are in contact with the end parts of the 2 magnetic steel for axially positioning the magnetic steel. The rough positioning between the adjacent magnetic steel in the circumferential direction is performed through the positioning sheets, the convex head are tightly matched between the adjacent magnetic steel for precisely positioning the magnetic steel in the circumferential direction, and the parts of the annular positioning clamps, which are correspondingly positioned between the convex heads, are in contact with the end parts of the magnetic steel for axially positioning the magnetic steel, thereby realizing the positioning in the circumferential direction and the axial positioning between the magnetic steel and the housing, being unnecessary to use the glue for bonding between the magnetic steel and the housing, being more environment-friendly on the one hand, being convenient to assemble on the other hand and simultaneously enabling the positioning of the magnetic steel on the inner wall of the housing to be reliable and precise. The outer walls of the annular positioning clamps form annular convex rings, and one end surface of each annular convex ring is in contact with the end surface of the housing, thereby realizing reliable axial fixation of the annular positioning clamps. Preferably, gaps are arranged between the end parts of the positioning sheets and the end parts of the convex heads of the annular positioning clamps, thereby ensuring that the end surfaces between the annular positioning clamps and the convex heads are in close contact with the 3 magnetic steel and further ensuring the axial precise positioning of the magnetic steel. Therefore, the invention has the characteristics that the assembly is more convenient, the environmental protection is better, the positioning of the magnetic steel is reliable and precise and the like. Brief Description of the Drawings Figure 1 is a schematic diagram of stereo structure of the invention; Figure 2 is a schematic diagram of main view structure of the invention; Figure 3 is a schematic diagram of overhead view structure of Figure 2; Figure 4 is a C-C view of Figure 3. Detailed Description of the Invention In combination of the figures, the technical scheme of the invention is further specifically described through the following embodiment. Embodiment 1: as shown in Figure 1, Figure 2, Figure 3 and Figure 4, two blocks of magnetic steel 1 are uniformly arranged on the inner wall of a housing 2 at intervals, a positioning sheet 3 is arranged between the adjacent magnetic steel 1, the axial length of each positioning sheet 3 is smaller than the axial length of the magnetic steel 1, the positioning sheet 3 is axially centered and arranged between the adjacent magnetic steel 1, and the positioning sheets 3 are connected with the housing 2 through 4 screws; and annular positioning clamps 4 are respectively arranged at two ends of the inner wall of the housing, convex heads 5 protruding axially are respectively formed on the annular positioning clamps 4 corresponding to the position between the adjacent magnetic steel 1, the convex heads 5 are tightly matched between the adjacent magnetic steel 1, the parts of the annular positioning clamps 4, which are correspondingly positioned between the convex heads 5, are in contact with the end parts of the magnetic steel 1 for axially positioning the magnetic steel 1, gaps are arranged between the end parts of the positioning sheets 3 and the end parts of the convex heads of the annular positioning clamps 4, the outer walls of the annular positioning clamps 4 form annular convex rings 6, and one end surface of each annular convex ring 6 is in contact with the end surface of the housing 2. The rough positioning between the adjacent magnetic steel in the circumferential direction is performed through the positioning sheets, the convex head are tightly matched between the adjacent magnetic steel for precisely positioning the magnetic steel in the circumferential direction, and the parts of the annular positioning clamps, which are correspondingly positioned between the convex heads, are in contact with the end parts of the magnetic steel for axially positioning the magnetic steel, thereby realizing the positioning in the circumferential direction and the axial positioning between the magnetic steel and the housing, being 5 unnecessary to use the glue for bonding between the magnetic steel and the housing, being more environment-friendly on the one hand, being convenient to assemble on the other hand and simultaneously enabling the positioning of the magnetic steel on the inner wall of the housing to be reliable and precise. 6