A crank assembly and a method for its molding

Abstract

This invention discloses a crank assembly and its molding method. The crank assembly includes: a first connecting structure comprising a bottom bracket and a first crank sleeved at a first end of the bottom bracket, the bottom bracket and the first crank being integrally formed, the first crank being made of carbon fiber material; and a second connecting structure comprising a second crank and a metal sleeve disposed within the second crank, the metal sleeve being disposed at a second end of the bottom bracket, the second crank and the metal sleeve being integrally formed, the second crank being made of carbon fiber material. In this invention, the first end of the bottom bracket and the first crank are integrally formed, and the second crank and the metal sleeve are integrally formed, thereby enabling the entire crank component to be installed by simply sleeved onto the second end of the bottom bracket. The molding method is simple and easy to implement.

Claims

1. A crank assembly comprising: A first connecting structure includes a central shaft and a first crank sleeved at a first end of the central shaft, the central shaft and the first crank being integrally formed, the first crank being made of carbon fiber material; a second connecting structure includes a second crank and a metal sleeve disposed within the second crank, the metal sleeve being used to sleeve at a second end of the central shaft, the second crank and the metal sleeve being integrally formed, the second crank being made of carbon fiber material.

2. The crank assembly as claimed in claim 1, wherein the crank assembly further includes a fastener that passes through the second crank along the side of the second crank away from the bottom bracket and is connected to the bottom bracket and the metal sleeve, respectively.

3. The crank assembly of claim 1 or 2, wherein the bottom shaft further includes a shaft body and a mating head disposed at a first end of the shaft body, the mating head having a first groove extending circumferentially along the mating head, and the first crank having a first protrusion embedded in the first groove.

4. The crank assembly as claimed in claim 1 or 2, wherein the metal sleeve is a spline sleeve, the spline sleeve has a second groove extending circumferentially along the spline sleeve, and the second crank has a second protrusion that is embedded in the second groove.

5. A method for molding a crank assembly, comprising the steps of providing a first mold, a bottom shaft, and a first carbon fiber preform; fitting the first carbon fiber preform over one end of the bottom shaft and placing both into the first mold; and, under first preset conditions, fabricating the bottom shaft and the first carbon fiber preform into an integral first connecting structure, wherein... The first carbon fiber preform is used to prepare a first crank. A second mold, a metal sleeve, and a second carbon fiber preform are provided. The second carbon fiber preform is fitted over the metal sleeve and both are placed in the second mold. Under a second preset condition, the metal sleeve and the second carbon fiber preform are integrated into a second connecting structure. The second carbon fiber preform is used to prepare the second crank. The area of ​​the central shaft that is not connected to the first crank is subjected to temperature control treatment. The metal sleeve and the other end of the central shaft are connected to the first connecting structure and the second connecting structure to form a whole.

6. The method for molding a crank assembly as described in claim 5, wherein the first mold includes a first body, a first protective structure, and a second protective structure, the first body having a first cavity, the first protective structure and the second protective structure being disposed within the first cavity, and the step of placing the central shaft and the first carbon fiber preform into the first mold includes: sleeve the first protective structure on the end of the central shaft connected to the first carbon fiber preform, and fitting the first carbon fiber preform; inserting the second protective structure into the end of the central shaft, and fitting the second protective structure and the first carbon fiber preform together; and placing the central shaft, the first carbon fiber preform, the first protective structure, and the second protective structure into corresponding positions within the first cavity.

7. A method for molding a crank assembly as described in claim 5 or 6, wherein the second mold includes a second body, a third protective structure, and a fourth protective structure, the second body having a second cavity, the third protective structure and the fourth protective structure being disposed within the second cavity, and the step of placing the metal sleeve and the second carbon fiber preform into the second mold includes: inserting one end of the third protective structure along the axial direction of the metal sleeve through the metal sleeve and fitting it against the end face of one end of the metal sleeve; fitting the fourth protective structure from the other end along the axial direction of the metal sleeve outside the metal sleeve and fitting it against the second carbon fiber preform; and placing the metal sleeve, the second carbon fiber preform, the third protective structure, and the fourth protective structure into corresponding positions within the second cavity.

8. The method of forming a crank assembly as claimed in claim 5, wherein prior to the steps of providing the bottom shaft and the metal sleeve, it further includes surface treating the end of the bottom shaft connected to the first carbon fiber preform and / or surface treating the outer surface of the metal sleeve.

9. The method of forming a crank assembly as claimed in claim 5, wherein prior to the steps of providing the bottom shaft and the metal sleeve, it further includes providing a first transition layer on the outer surface of the end of the bottom shaft connected to the first carbon fiber preform and / or providing a second transition layer on the outer surface of the metal sleeve.

10. A method for forming a crank assembly as claimed in claim 5, 6, 8, or 9, wherein prior to the steps of providing the first carbon fiber preform and the second carbon fiber preform, the method further comprises adding a first toughening material to the region of the first carbon fiber preform connected to the central shaft and / or adding a second toughening material to the region of the second carbon fiber preform connected to the metal sleeve.

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