DETACHABLE COMBINED TOY TOP FIELD OF THE INVENTION The present disclosure relates to a toy top, and more particularly, to a detachable combined toy top. 5 BACKGROUND OF THE INVENTION An existing toy top is usually consisted of a single top that comprises an axle sleeve structure, a top cap, a top piece, and a top tip, the top cap of which can be connected to a top ejector in order to eject and spin the top. In order to enhance or modify their functionality and beat a rival top in a game, the prior tops are mostly designed to be 10 upgradable, assembled in a way that is easy for disassembling and reassembling; the axle sleeve structure is also designed to be extendable so that the top can be quickly dissembled to replace or add parts. However, no matter how strengthened they are, the prior toy tops are still spinning as just one single top and it is hard to further increase their winning chances in a spin-and-duel game. Meanwhile, the characteristic of tops of 15 being upgradable by disassembling and reassembling has become common and insipid, and therefore hard to remain favorable for the players in the long term. SUMMARY OF THE INVENTION A preferred aim of the present invention is to overcome or ameliorate the problem in the prior art above by providing a detachable combined toy top that can be divided in two 20 during a game, increasing the chances to win and the fun of the gameplay. In one embodiment, the invention provides a detachable combined toy top, including a main top and a subsidiary top, wherein the main top includes a top cap, a main top piece, a top axle sleeve, and a top tip, and the subsidiary top includes a subsidiary top piece, an axle sleeve structure, and a top tip. An elastic structure is provided on the upper portion 25 of the subsidiary top, the main top is configured to be actively connected to the upper portion of the subsidiary top, and in use, the main top can be detached from the subsidiary top and ejected by means of the elastic structure when an object comes into contact with the toy top during rotation to cause differential rotation between the main top and the subsidiary top, such that the two tops spin on themselves separately. 30 Preferably, the elastic structure above is a spring base provided on the axle sleeve structure of the subsidiary top, wherein the axle sleeve structure has a cavity to contain the spring base, and the upper end of the spring base protrudes from the axle sleeve structure so that the spring base is compressed when the main top is connected to the subsidiary top. To allow the removable connection to unlock when the toy top clashes with an object, 5 preferably the removable connection between the main top and the subsidiary top is realized by linking the main top piece and the subsidiary top piece. The main top piece and the subsidiary top piece are provided respectively with adapting pieces that can be actively connected to each other, by which the main top and the subsidiary top can be combined into one by pushing the main top onto the subsidiary top and compressing the 10 spring base until the adapting pieces of the main top piece and subsidiary top piece are fitted and connected together. Furthermore, the subsidiary top piece is designed to be a torus, wherein the adapting pieces of the subsidiary top piece are upper holders provided at the upper edge of the inner ring of the subsidiary top, and the adapting piece of the main top piece are designed correspondingly to be lower holders fitting the upper 15 holders. The main top piece and subsidiary top piece can be combined into one top, which can later be separated by turning, by stacking the main top piece onto the subsidiary top, staggering the lower holders and the upper holders while pressing, and then turning the main top piece so that the lower holders are snapped onto the upper holders. 20 Preferably, to achieve the connection between the main top and the subsidiary top secure enough yet not too tight to unlock, hemispherical bumps are provided on the lower surface of the upper holders, while corresponding hemispherical pits are provided on the upper surface of the lower holders, wherein the hemispherical pits and the hemispherical bumps form socket locks when the lower holders turn and snap onto the 25 upper holders. Preferably, to ensure that the main top will not separate from the subsidiary top immediately upon a clash between the toy top and an object, there are two hemispherical pits on the lower holder to fit one hemispherical bump successively before the detachment of the main top from the subsidiary top occurs. 30 There is disclosed herein a top combination of a main top and a subsidiary top, wherein the subsidiary top has an elastic structure on its top and the main top is actively connected to the top of the subsidiary top and pressing against the elastic structure. 2 When clashed against an object during spinning, the main top can be detached from the subsidiary top by unsnapping the moveable connection and ejected out, the two tops spinning on themselves separately therefrom. As a result, the top divides into two in a game, which substantially promotes its attack capability and the chances to win. In 5 addition, the gameplay is novel and highly interesting, which may gain the favor of more players. The moveable connection structure of the main and subsidiary tops are provided on the main and subsidiary top pieces, so that the clash between the top pieces of two rival tops pushes the top pieces to turn, unlocking the link joint; meanwhile, there are multiple hemispherical pits on the adapting pieces of the main top for one 10 hemispherical bump on the adapting pieces of the subsidiary top, so that the hemispherical bump will fit in multiple hemispherical pits before the final detachment of the main top from the subsidiary top. Therefore, the combined toy top will not detach upon one clash, but save the winning trick to the critical moment, which increases the randomness of the top duels and further increases the fun of the gameplay. Overall, the 15 detachable combined toy top is an ingenuous design that combines two tops in one, which can be detached by a clash of the rival, giving the player higher chances to win in a game; meanwhile, it can also help develop the manual dexterity and competitive capacity of the children. The invention will be explained in more detail below with reference to the drawings and 20 its embodiments. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a dimensional structure view of the toy top according to one embodiment of the present disclosure. Fig. 2 shows a section structure view of the toy top according to one embodiment of the 25 present disclosure. Fig. 3 shows an exploded structure view of the toy top according to one embodiment of the present disclosure. Fig. 4 shows a dimensional structure view of the subsidiary top piece according to one embodiment of the present disclosure. 30 Fig. 5 shows a dimensional structure view of the main top piece according to one embodiment of the present disclosure. 3 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in Fig. 1 through Fig. 3, the embodiment herein provides a detachable combined toy top that comprises a main top and a subsidiary top, wherein the main top includes a top cap 1, a main top piece 2, a top axle sleeve 3, and a top tip 4, while the 5 subsidiary top includes a subsidiary top piece 5, an axle sleeve structure 6, and a top tip 4. The subsidiary top has an elastic structure on its top, and the main top is actively connected to the top of the subsidiary top. By the elastic structure, when clashed during spinning, the main top can be detached from the subsidiary top and ejected out, and the two tops spinning on themselves separately therefrom. As a result, the top divides into 10 two in a game, which substantially promotes its attack capability and the chances to win. In addition, the gameplay is novel and highly interesting, which may gain the favor of more players. As shown in Fig. 3, in this embodiment, the elastic structure above is a spring base 7 provided on the axle sleeve structure 6 of the subsidiary top, wherein the axle sleeve 15 structure 6 has a cavity 61 to contain the spring base 7, with the upper end of the spring base 7 protruding above the axle sleeve structure 6 so that the spring base 7 is compressed when the main top is connected to the subsidiary top. The assembled structure is shown in Fig. 2. The spring base 7 in this embodiment includes a ring base 71 and a spring 72, wherein snap-fit tabs 73 is formed in downward extension of the 20 ring base 71, while the wall of the cavity 61 is provided with strip snap-fit grooves 62; snap-fitting of the snap-fit tabs 73 into the strip snap-fit grooves 62 allows the movement of the ring base 71 in the strip snap groove 62; the spring 72 is installed between the ring base 71 and the cavity 61 so that the ring base 71 can move elastically. The moveable connection between the main top and the subsidiary top in this 25 embodiment is realized by linking the main top piece 2 and the subsidiary top piece 5, the two of which can be combined into one by pushing the main top onto the subsidiary top and compressing the spring base 7 until the adapting pieces of the main top piece 2 and subsidiary top piece 5 are connected together. As shown in Fig. 4, the subsidiary top piece 5 is designed to be a torus, wherein the 30 adapting pieces of the subsidiary top piece 5 are the upper holders 51 at the upper edge of the inner surface of the torus of the subsidiary top piece 5. In this embodiment the junction plates 54 is provided on the inner ring of the subsidiary top piece 5: four junction plates 54 in total, evenly distributed in a ring. Each of the left and right ends of 4 each junction plate 54 has an upper holder 51, which forms a "T" shape with the junction plate 54 and has hemispherical bumps 52 on its lower surface. The outer surface of the torus of the subsidiary top piece 5 adopts a bumpy texture, which promotes the aesthetics and attack capacity of the top at the same time. As shown in Fig. 5 5, in this embodiment, the main top piece 2 is also a torus, with another small torus in the middle, and the two toruses are connected by four bracing bars 23. The adapting piece of the main top are designed to be lower holders 21 for cooperating with the upper holders 51, wherein the lower holders 21 bulge on the edge of the inner surface of the torus, one on each of the left and right ends of each bracing bar 23. There are two 10 hemispherical pits 22 on the upper surface of each lower holder 21, corresponding to a hemispherical bump 52. In this embodiment, there are a plurality of attack portions 24 on the outer surface of the main top piece 2, which protrude out from the edge of the main top piece 2. The attack portions are cone-shape attaching blocks, six in total, with bumpy texture between each two units, making the main top piece 2 the attacking top 15 piece of the combined top. To assemble the two top pieces in this embodiment, first staggeredly align the lower holder 21 of the main top piece 2 and the upper holder 51 of the subsidiary piece 5, i.e., the lower holders 21 are aligned with the gaps in between the upper holders 51 of the subsidiary toy piece 5, and close up. Now, the lower holders 21 of the main top piece 2 pass through the gaps and locate beneath the upper holders 20 51 of the subsidiary top piece 5. Then, turn the main top to fasten it onto the subsidiary top according to the desired direction to eject and spin the top. If a clockwise spin is desired, then turn the main top counter-clockwise against the subsidiary top, so that the lower holders 21 on the right end of the bracing bars 23 fasten onto the upper holders 51 on the left side of the subsidiary top, meanwhile matching the interior hemispherical 25 pits 22 to the hemispherical bumps 52 on the upper holder 51. If a counter-clockwise spin is desired, then turn the main top clockwise against the subsidiary top, so that the lower holders 21 on the left end of the bracing bars 23 fasten onto the upper holders 51 on the right side of the subsidiary top, meanwhile matching the interior hemispherical pits 22 to the hemispherical bumps 52 on the upper holder 51. Therefore during a game, 30 when the toy top is clashed for the first time by an impact force that is large enough to turn the main top piece 2, the main top will not unlock immediately from the subsidiary top; instead, the hemispherical bumps 52 move to match with the exterior hemispherical pits 22 of the main top piece 2. When another clash occurs that turns the main top piece 2 again, the hemispherical bumps 52 will slide out of the hemispherical pits 22, and the 5 upper holders 51 and the lower holders 21 are completely dislocated. At this time, the spring base 7 recovers its elasticity and ejects out the main top, so that the main top and the subsidiary top disengage and spin separately. As shown in Fig. 3, in this embodiment, the axle sleeve structure 6 of the subsidiary top 5 has an enveloping edge 62 on the outward extension of its the upper edge, wherein the enveloping edge 62 has snap holes 63. The subsidiary top piece 5 has a snap block 53 on its lower part and a stop block on its upper part, wherein the vertical distance between the snap block 53 and the stop block is equal to the thickness of the enveloping edge 62. The subsidiary toy piece 5 can be fastened onto the axle sleeve structure 6 by 10 pushing the snap blocks 53 through the snap holes 63 and turning. The stop blocks in this embodiment are the junction plates 54 that connect the upper holders 51. The main top piece 2 of the main top has a weight stack 8 connected to its top, which is fastened between the top cap 1 and top axle sleeve 3 by connection of the top cap 1 and top axle sleeve 3. The main top piece 2 is fastened on the top of the top axle sleeve 3, while the 15 top tip 4 of the main top is installed on the lower tip of the top axle sleeve 3. The top disclosed herein can be applied to top duel games. Many kinds of main top piece 2 can be derived from this design with different attacking capacities. The players can assemble the main top according to their choices, assemble the subsidiary top, and decide whether the top should spin clockwise or counter-clockwise. Afterwards, the 20 main top can be fastened onto the subsidiary top by the movable connection between the main top piece 2 and the subsidiary top piece 5. At the start of the game, the dueling players can eject their tops onto the playground, where the two tops clash against each other; during the clashing, the main top of the combined top will turn in an opposite direction relative to the subsidiary top, until the hemispherical pits 22 on the main top 25 piece 2 and the hemispherical bumps 52 on the subsidiary top piece 5 completely disengage. Then, the main top will jump up as ejected by the spring 72 of the spring base 7 on the subsidiary top, deviate from the subsidiary top as affected by the rotational inertia force, and land on the ground on its tip 4 to continue spinning; meanwhile, the subsidiary top also continues spinning after ejecting out the main top. As a result, the 30 combined top divides into two independent tops that spin separately, which creates a two-against-one situation, substantially enhancing the chances to win. Meanwhile, it promotes the fun of top duel games and also helps develop the manual dexterity and competitive capacity of the children. 6 Although the disclosure has described herein in terms of specific embodiments, such description should not mean any limitation to our disclosure. Based on the description of this disclosure, those skilled in the art will recognize that the invention-creation can be practiced in other variations within the spirit and scope of the claims. 5 The term "comprise" and variants of that term such as "comprises" or "comprising" are used herein to denote the inclusion of a stated integer or integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required. Reference to background art or other prior art in this specification is not an admission 10 that such background art or other prior art is common general knowledge in Australia or elsewhere. 7