CN111485967A

CN111485967A - Camshaft and method for producing same

Info

Publication number: CN111485967A
Application number: CN201910074467.3A
Authority: CN
Inventors: 张凤武; 奚勇
Original assignee: Shanghai Universoon Auto Parts Co Ltd
Current assignee: Shanghai Universoon Auto Parts Co Ltd
Priority date: 2019-01-25
Filing date: 2019-01-25
Publication date: 2020-08-04

Abstract

The invention provides a camshaft and a manufacturing method thereof, comprising the following steps: a mandrel having an axially extending shaft bore; the mandrel is provided with a matching section, and key teeth and key grooves are alternately arranged on the peripheral surface of the matching section in the circumferential direction; the cam and the transmission unit are sleeved on the matching section of the mandrel, and the inner peripheral surface profiles of the cam and the transmission unit are consistent with the outer peripheral surface profile of the matching section and are fixed with the mandrel in an expanding manner. When the mandrel is matched with the cam and the transmission unit, the precise positioning can be realized, and the fixed and anti-rotation connection between the mandrel and the cam and the transmission unit is realized; the structure and the manufacturing process of the existing camshaft can be simplified, the time consumption and the cost of the manufacturing process of the camshaft are shortened, and meanwhile, the enough large transmission torque is ensured.

Description

Camshaft and method for producing same

Technical Field

The invention relates to the field of automobile engines, in particular to a camshaft and a manufacturing method thereof.

Background

The camshaft is one of the key transmission components of an automotive engine, and directly influences the performance of the engine. At present, the method for manufacturing the camshaft is as follows: the traditional integral casting method and forging method, and a combined method for manufacturing the camshaft. Among them, the casting method and the forging method are used to manufacture the camshaft, and have many disadvantages, such as: the performance maximization design and utilization can not be carried out to each position of camshaft, and the performance requirement to each part such as cam, axle journal, dabber, drive unit has very big difference, if with single material, can not accomplish the maximize to the performance of every part, and whole manufacturing process is complicated, needs a large amount of machining processes, and production efficiency is not high, wastes time and energy, and the cost is too high to, the energy consumption is big, environmental pollution is serious.

The manufacturing method of the assembled camshaft comprises the following steps: welding, sintering, expanding, shrink-fitting, mechanical knurling, and the like. The methods are that the camshaft is decomposed into a single cam part, an intermediate mandrel part, a transmission part and the like, and then different manufacturing methods are applied to connect the parts to form the camshaft. The welding method is easy to generate the phenomena of thermal deformation, thermal cracks and the like, and the cam unit is difficult to be well positioned on the middle shaft tube, so that the size precision of the cam shaft is low; the sintering method is easy to bend and deform after the camshaft in an integral sintering mode, and the dimensional accuracy is low; the hot jacket method needs to ensure that the sizes of gaps of all components are uniform, and the temperature is difficult to control during hot jacket matching; the mechanical knurling method needs to be combined for many times to complete the assembly of one camshaft, the production procedures are many and are tedious, and the torsional strength is not high.

The above methods have many problems difficult to control after connection, among them: the angular positioning of the cam unit and the central shaft tube and the control of the connection strength are all problems that are difficult to solve.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a camshaft and a method for manufacturing the same, which solve the problems of the prior art that the camshaft cannot accurately position the cam and the transmission unit with the mandrel during the production process and the torsional strength after combination is insufficient.

To achieve the above and other related objects, the present invention provides a camshaft including:

a mandrel having an axially extending shaft bore; the mandrel is provided with a matching section, and key teeth and key grooves are alternately arranged on the peripheral surface of the matching section in the circumferential direction;

the cam and the transmission unit are sleeved on the matching section of the mandrel, and the inner peripheral surface profiles of the cam and the transmission unit are consistent with the outer peripheral surface profile of the matching section and are fixed with the mandrel in an expanding manner.

Preferably, in the cross-sectional profile of the mandrel at any axial position, the top surface lines of all the key teeth belong to the same polygon, and the groove bottom lines of all the key grooves belong to the same polygon.

Preferably, the top surface lines of the adjacent key teeth are connected with the groove bottom lines of the key grooves through straight lines; one end of the straight line is connected with the groove bottom line of the key groove through arc transition, and the other end of the straight line is connected with the top line of the key tooth through arc transition.

Preferably, the polygon formed by the top surface line of the key tooth is concentric with the polygon formed by the groove bottom line of the key groove.

Preferably, the line forms an angle with a radial plane through the axis of the mandrel.

Preferably, the width of the groove bottom of the key groove is smaller than that of the notch of the key groove, and the width of the tooth top of the key tooth is smaller than that of the tooth bottom of the key tooth.

Preferably, the inner circumferential surface of the cam is provided with a groove area and a convex tooth area in an annular direction, the groove area corresponds to the key tooth on the mandrel, the convex tooth area corresponds to the key groove on the mandrel, and two side walls of the groove area are straight walls.

Preferably, the groove bottom width of the groove region is smaller than the notch width of the groove region, and the tooth top width of the convex tooth region is smaller than the tooth bottom width of the convex tooth region.

Preferably, the inner circumferential surface of the transmission unit has a notch area and a protrusion area corresponding to the key teeth and the key grooves, respectively, and both side walls of the notch area are linear walls.

Preferably, the width of the bottom of the notch area is smaller than the opening width of the notch area.

Preferably, cylindrical sections are machined on the outer surface of the mandrel at intervals, and the cylindrical sections are journals of the mandrel, which are used for rotating and supporting the camshaft.

Preferably, the outer diameter of the mating section is larger than the outer diameter of the cylindrical section.

Preferably, the end part of the mandrel is provided with a plug for plugging the shaft hole.

Preferably, one end of the plug inserted into the mandrel is provided with an outer cylindrical surface, and knurling is performed on the outer cylindrical surface.

The present invention also provides a method of manufacturing a camshaft as described above, including: 1) preparing the mandrel, the cam and the transmission unit; the key teeth and the key grooves are formed on the outer peripheral surface of the mandrel in an annular alternating mode;

2) sleeving the cam and the transmission unit on the mandrel respectively according to a certain phase angle;

3) and radially expanding the part of the mandrel sleeved with the cam and the transmission unit to ensure that the cam and the transmission unit are expanded and fixed on the mandrel in the axial direction and the radial direction.

Preferably, the top surface lines of the adjacent keys are linearly connected with the bottom surface lines of the key slots; one end of the straight line is connected with the top surface line of the key tooth through arc transition, and the other end of the straight line is connected with the bottom line of the key groove through arc transition.

Preferably, the inner circumferential surface of the cam has a groove area and a convex tooth area corresponding to the key tooth and the key groove, respectively; the inner peripheral surface of the transmission unit has a notch area and a protrusion area corresponding to the key teeth and the key grooves, respectively.

Preferably, the specific step of radially expanding the mandrel in step 3) includes:

the shaft hole of the mandrel is filled with liquid, two self-centering sealing plugs are used for sealing two ports of the shaft tube, high-pressure liquid is continuously introduced into the shaft hole through central holes in the self-centering sealing plugs at two ends respectively, so that the matching part of the mandrel, the cam and the transmission unit is radially expanded and is radially and mutually expanded with the cam and the transmission unit.

Preferably, the specific step of radially expanding the mandrel in step 3) includes: extending an expansion piece into the shaft hole of the mandrel, so that the matching part of the mandrel, the cam and the transmission unit is expanded along the radial direction; the expansion piece is a steel ball, a cylinder or an elliptic cylinder, and the outer diameter of the cross section of the expansion piece attached to the shaft hole is larger than the inner diameter of the shaft hole.

Preferably, before the cam and the transmission unit are sleeved on the mandrel, cylindrical sections are machined on the outer peripheral surface of the mandrel at intervals of a certain distance, the cylindrical sections form a journal, and the journal is used for rotating and supporting the whole camshaft.

As described above, the camshaft and the method for manufacturing the same according to the present invention have the following advantageous effects: the staggered key teeth and key grooves are arranged on the outer peripheral surface of the mandrel, the inner peripheral surface profiles of the cam and the transmission unit are consistent with the outer peripheral surface profile of the matching section, and when the mandrel is matched with the cam and the transmission unit, accurate positioning can be realized; meanwhile, the key teeth and the key grooves on the cam, the transmission unit and the mandrel are mutually matched and connected, so that the expansion connection of the tops of the polygonal key teeth and the bottoms of the key grooves is not only relied on, but also the expansion connection of the two side edges of the key teeth and the key grooves is increased, therefore, the connection strength of the cam, the transmission unit and the mandrel is greatly enhanced, and the fixed and anti-rotation connection between the cam and the transmission unit and the mandrel is realized; the structure and the manufacturing process of the existing camshaft can be simplified, the time consumption and the cost of the manufacturing process of the camshaft are shortened, and meanwhile, the enough large transmission torque is ensured.

Drawings

Fig. 1 shows a schematic view of a camshaft according to the invention.

Figure 2 shows a schematic cross-section of a mandrel of the present invention in an axial position.

Fig. 3 is a partially enlarged view of fig. 2.

Figure 4 shows a schematic view of a mandrel according to the invention.

Fig. 5 shows a cross-sectional schematic view of the cam of the present invention.

Fig. 6 is a partially enlarged view of fig. 5.

Fig. 7 shows a schematic view of the transmission unit of the present invention.

Fig. 8 shows a partial enlarged view of the transmission unit of the present invention.

Fig. 9 is a schematic view of the plug of the present invention.

FIG. 10 shows one embodiment of the expansion performed in the manufacture of the camshaft of the present invention.

Fig. 11 shows another embodiment of the expansion performed in the manufacture of the camshaft of the present invention.

Fig. 12a-12c show various embodiments of the extender of the present invention.

Description of the element reference numerals

1 mandrel

10 mating segment

102 key tooth

103 key groove

105 straight line

104. 106 arc

107 top surface line

108 slot bottom line

11 cylindrical section

2 cam

201 groove area

202 convex tooth area

204 straight line

203. 205 arc of circle

Top surface line of 206 lobe region

207 groove zone slot bottom line

3 plug

4 Transmission unit

401 notch area

402 raised area

404 straight wall

403. 405 arc surface

7 high-pressure oil pipe

8 hydraulic cylinder

9 working table

100 mould

110 self-centering sealing plug

120 hydraulic piston rod

130 oil groove

140 liquid

150 lower die

240 upper die

250 lower die

220 shaft hole

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Please refer to fig. 1 to 12. It should be understood that the structures, ratios, sizes, and the like shown in the drawings are only used for matching the disclosure of the present disclosure, and are not used for limiting the conditions that the present disclosure can be implemented, so that the present disclosure is not limited to the technical essence, and any structural modifications, ratio changes, or size adjustments should still fall within the scope of the present disclosure without affecting the efficacy and the achievable purpose of the present disclosure. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.

As shown in fig. 1, the present invention provides a camshaft including:

a mandrel 1 having an axially extending shaft hole; the mandrel 1 is provided with a matching section 10, and the outer peripheral surface of the matching section 10 is provided with key teeth 102 and key grooves 103 in an annular and alternate manner, as shown in fig. 2-4;

the cam 2 and the transmission unit 4 are sleeved on the matching section 10 of the mandrel 1, and the inner peripheral surface profiles of the cam 2 and the transmission unit 4 are consistent with the outer peripheral surface profile of the matching section 10 and are fixed with the mandrel 2 in an expanding manner.

According to the invention, the staggered key teeth 102 and the key grooves 103 are arranged on the outer peripheral surface of the mandrel 1, the inner peripheral surface profiles of the cam 2 and the transmission unit 4 are consistent with the outer peripheral surface profile of the matching section 10, when the mandrel 1 is matched with the cam 2 and the transmission unit 4, accurate positioning can be realized, fixed and anti-rotation connection between the cam 2 and the transmission unit can be realized, positioning of the cam, the mandrel and the transmission unit during assembly can be omitted, namely, the structure and the manufacturing process of the existing camshaft can be simplified, the time consumption of the manufacturing process of the camshaft is shortened, the cost is reduced, and meanwhile, a sufficiently large transmission torque is ensured.

For convenience of description, the term "cross section" as used herein refers to a section perpendicular to the axis of the mandrel.

Core shaft

As shown in fig. 4, in the present embodiment, cylindrical sections 11 are machined at intervals on the outer surface of the mandrel 1, and the cylindrical sections 11 are journals of the mandrel 1, which are used for rotating and supporting a camshaft. The cylindrical sections 11 and the fitting sections 10 are alternately arranged in this embodiment, and the outer diameter of the fitting sections 10 is larger than that of the cylindrical sections 11.

Referring to fig. 2 and 3, in the present embodiment, the key teeth 102 and the key slots 103 are alternately arranged on the outer peripheral surface of the mating segment, and in the cross-sectional profile of any axial position of the mandrel, the top surface lines 107 of all the key teeth 102 belong to the same polygon, and the bottom surface lines 108 of all the key slots 103 belong to the same polygon.

Furthermore, in the adjacent key tooth 102 and key slot 103, the top surface line 107 of the key tooth 102 is connected with the bottom surface line 108 of the key slot 103 through the straight line 105. In the cross-sectional profile of the mandrel at any axial position, a straight line 105 is in transition connection with the groove bottom line 108 through an arc 106, and the straight line 105 is in transition connection with the top surface line 107 through an arc 104. That is, between the adjacent key teeth 102 and the key grooves 103, the top surfaces of the key teeth (i.e., the top surface lines 107) and the groove walls of the key grooves 103 (i.e., the straight lines 105) are adjacent to each other through arc surface transition, the groove walls of the key grooves 103 and the groove bottoms of the key grooves are also adjacent to each other through arc surface transition, and the arc surfaces can be regarded as chamfer processing, so that the guide matching of the cam and the transmission unit is facilitated.

In the present embodiment, all the top surface lines 107 described above form a polygon which is concentric with all the bottom surface lines 108. The polygon is a hexagon in this embodiment. The polygon may be other than a hexagon. The number of sides of the polygon may be a multiple of the number of engine cylinders, such as one, two, etc. For example, for a three or six cylinder engine, the polygon may be a hexagon; for a four cylinder engine, the polygon may be a quadrilateral. The phase difference between two cams corresponding to two adjacent cylinders of the engine is N (360 DEG/N), wherein N is the number of cylinders of the engine cylinder, and N is 1 or an integer larger than 1.

In this embodiment the line 105 forms an angle with a radial plane through the axis of the spindle, i.e. the angle formed by the groove wall of the key groove 103 and a radial plane through the axis of the spindle and the width of the groove bottom. The included angle exists, so that the width of the groove bottom of the key groove 103 is smaller than that of the notch of the key groove 103, namely, the groove width is gradually reduced along with the increase of the groove depth; the top width of the key teeth 102 is less than the bottom width of the key teeth 102.

Cam and transmission unit

The inner circumferential profiles of the cam 2 and the transmission unit 4 in this embodiment correspond to the outer circumferential profile of the engagement section 10 described above. Referring to fig. 5 and 6, the inner circumferential surface of the cam 2 is circumferentially provided with a groove area 201 and a convex tooth area 202, the groove area 201 corresponds to the key tooth 102 on the spindle, the convex tooth area 202 corresponds to the key groove 103 on the spindle, and two side walls of the groove area 201 are linear walls. The method specifically comprises the following steps: in a cross-section in axial position, the groove bottom line 207 of the groove region 201 is connected to the top line 206 of the tooth region 202 by a straight line 204.

For guiding, the straight line 204 is connected with the slot bottom line 207 and the top surface line 206 through the

circular arcs

205 and 203.

In this embodiment, the width of the groove bottom of the groove region 201 is smaller than the width of the notch of the groove region 201, that is, the groove width gradually decreases with the increase of the groove depth, and the width of the notch is large to facilitate the introduction of the key teeth 102 on the spindle; similarly, the key slot 103 of the spindle 1 has a wide slot for guiding the cam 2 in the cam area 202. The width of the tooth top of the lobe region 202 is smaller than the width of the tooth bottom of the lobe region 202. This embodiment makes it and dabber change the direction cooperation through the design to the width and the lateral wall in recess district, dogtooth district, is convenient for fixed, anti rotation ground between the two to be connected.

As shown in fig. 7 and 8, the inner circumferential surface of the transmission unit 4 has a notch area 401 and a protrusion area 402 corresponding to the key teeth 102 and the key grooves 103, respectively, and both side walls of the notch area 401 are linear walls 404. The method specifically comprises the following steps: in a cross-section at an axial position, the groove bottom line of the notch zone 401 is connected to the top surface line of the protrusion zone 402 by a straight line.

For guiding, the side wall of the notch region 401 is connected to the bottom of the notch region 401 and the top of the protrusion region 402 by

arc surfaces

405 and 403. In this embodiment, the width of the bottom of the notch area 401 is smaller than the opening width of the notch area 401, i.e. the groove width gradually decreases with the increase of the groove depth, and the opening width is large to facilitate the introduction of the key teeth 102 on the mandrel.

As shown in fig. 1, in the embodiment, a plug 3 for plugging a shaft hole is disposed at an end of the mandrel 1, and the plug 3 prevents impurities from entering the mandrel, and enhances strength of the end of the mandrel, so as to facilitate fixing of the transmission unit 4.

For convenience of processing, as shown in fig. 3, the end of the plug 3 of this embodiment inserted into the mandrel 1 has an outer cylindrical surface on which knurling processing is performed. The diameter of the outer cylindrical surface of the plug 3 is slightly larger than the inner diameter of the shaft hole, and the plug 3 is pressed into inner holes at two ends of the mandrel.

The present invention also provides a method of manufacturing a camshaft as described above, including: 1) preparing the mandrel 1, the cam 2 and the transmission unit 4; the specific structures of the mandrel 1, the cam 2 and the transmission unit 4 are as described above and will not be described in detail;

2) sleeving the cam 2 and the transmission unit 4 on the mandrel 1 respectively according to a certain phase angle;

3) and radially expanding the part of the mandrel 1 sleeved with the cam 2 and the transmission unit 4, so that the cam 2 and the transmission unit 4 are expanded and fixed on the mandrel 1 in the axial direction and the radial direction.

The specific production process of the mandrel 1 may be as follows:

the shaft tube with the shaft hole 220 is formed by utilizing a precise cold drawing process, and the teeth strengthening 102 and the key groove 103 are formed on the outer cylindrical surface of the shaft tube by utilizing the cold drawing process, so that the circular arc area and the straight line area of the shaft tube can be ensured to have higher precision, machining is not needed, and the manufacturing cost of the camshaft is reduced. The external cross-section of the shaft tube, as shown in fig. 2-4, comprises: top surface lines 107 and arcs 104 of the outer ring, and groove bottom lines 108 and arcs 106 of the inner ring, wherein all the top surface lines 107 in the outer ring belong to a polygon, and the top surface lines 107 and the arcs 104 of the outer ring form the key teeth 102; all groove bottom lines 108 of the inner ring belong to a polygon, the groove bottom lines 108 and arcs 106 of the inner ring form key grooves 103, the polygon of the outer ring and the polygon of the inner ring are concentric, the key teeth 102 and the key grooves 103 are connected through inclined straight lines 105, the straight lines 105 form a certain angle with a radial plane passing through the axis of the mandrel, and the key teeth 102 and the key grooves 103 are arranged in a staggered mode along the circumferential direction and are connected with each other to form the cross section profile.

After the shaft tube is subjected to a cold drawing process and is straightened, a section of outer cylindrical surface, namely the cylindrical section 11, is processed on the outer circumferential surface of the mandrel 1 at certain intervals, so as to form a shaft neck. After the shaft neck is formed, the shaft neck is subjected to a corresponding heat treatment process, so that the hardness and the wear resistance of the shaft neck are enhanced, and the shaft neck is used for positioning, rotating and supporting the rotary motion of the whole camshaft.

In the step 2), the cam 2 and the transmission unit 4 are sleeved on the mandrel 1, and the outer circumferential surface of the mandrel 1 is matched with the inner circumferential surfaces of the cam 2 and the transmission unit 4. Sleeving the cams 2 on the mandrel 1 according to a certain angle, keeping a certain axial distance between the cams 2 on the mandrel 1, inserting the convex tooth areas 202 of the cams 2 into the key grooves 103 of the mandrel 1, inserting the key teeth 102 of the mandrel 1 into the groove areas 201 of the cams 2, and forming a certain small gap between the cams 2 and the mandrel 1 in the radial direction; the transmission unit 4 is sleeved at one end of the shaft tube according to a certain angle, the convex area 402 of the transmission unit 4 is inserted into the key groove 103 of the mandrel 1, the key teeth 102 of the mandrel 1 are inserted into the notch area 401 of the transmission unit 4, and a certain small gap exists between the transmission unit 4 and the mandrel 1 in the radial direction. The cam 2 and the transmission unit 4 are sleeved on the mandrel 1 according to a certain angle to form a pre-assembly body of the camshaft.

An embodiment of radially expanding the mandrel in the step 3) is shown in fig. 10, and the specific steps include:

putting the pre-assembly formed in the step 2) into a professional pressure expanding device, wherein the professional device comprises an upper die 100, a lower die 150, a workbench 9, a left hydraulic cylinder 8, a right hydraulic cylinder 8, a hydraulic piston rod 120, a self-centering sealing plug 110, an oil groove 130, a high-pressure oil pipe 7 and the like.

The die is integrally placed in the oil tank 130, the oil tank 130 is filled with the liquid 140, the liquid 140 fills the shaft hole of the whole mandrel 1, and no space which is not filled with the liquid is left in the shaft hole.

The hydraulic cylinders 8 at the two ends push the piston rod 120 to advance, the piston rod 120 drives the self-centering sealing plug 110 to advance, the self-centering sealing plug 110 is attached to the conical surfaces of the two ports of the mandrel to be sealed, high-pressure liquid is pressed into the mandrel 1 through the high-pressure oil pipe 7, when the fluid is continuously pressurized and introduced into the shaft hole 220, the self-centering sealing plugs 110 at the left side and the right side continuously push against the conical surfaces at the two ends of the mandrel 1 to be sealed, internal high pressure is formed in the shaft hole of the mandrel 1, and the matching section 10, the cam 2 and the transmission unit 4 are radially expanded to axially and radially fix the cam 2 and the transmission unit 4 on the mandrel 1.

Another embodiment of radially expanding the mandrel in step 3) above is shown in fig. 11, and the specific steps include:

this embodiment uses a solid member as the expansion member. The method specifically comprises the following steps: placing the pre-assembly formed in step 2) into the upper and

lower molds

240, 250 for axial positioning, the angular positioning having been positioned by the outer circumferential profile of the mandrel 1. By slowly pushing the expansion piece S into the shaft hole of the mandrel 1, the outer diameter of the expansion piece S is larger than the inner diameter of the mandrel shaft hole 220, so that the matching section expands along the radial direction at the extending part of the expansion piece S, and the cam 2 and the transmission unit 4 are tightly matched with the matching section 10, so that the cam 2 and the transmission unit 4 are fixed on the mandrel 1 along the axial direction and the radial direction.

In this embodiment, the stent S is not limited to the spherical shape shown in fig. 11 and 12a, but may be cylindrical in fig. 12b or elliptical in fig. 12c, and when the stent S is cylindrical or elliptical, the outer diameter of the stent S pushed into the axial hole is larger than the inner diameter of the mandrel.

After the cam 2, the transmission unit 4 and the matching section of the mandrel 1 are radially expanded and connected, the plug 3 is pressed into two ends of the mandrel 1; the end cap 3 can be machined in advance by using a machine, knurling is machined on the outer cylindrical surface at one end of the end cap, the knurled outer cylindrical surface is pressed into two ends of the mandrel 1, and the end cap 3 can be used as a positioning reference for subsequent grinding.

In summary, according to the camshaft and the manufacturing method thereof of the present invention, the end of the shaft hole of the mandrel is pressed with the plug, the outer circumferential surface of the mandrel is provided with the staggered key teeth and the key slots, the inner circumferential surface profiles of the cam and the transmission unit are consistent with the outer circumferential surface profile of the matching section, when the mandrel is matched with the cam and the transmission unit, the precise positioning can be achieved, and the fixed and anti-rotation connection between the cam and the transmission unit can be achieved; the structure and the manufacturing process of the existing camshaft can be simplified, the time consumption and the cost of the manufacturing process of the camshaft are shortened, and meanwhile, the enough large transmission torque is ensured. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A camshaft, comprising:

a mandrel having an axially extending shaft bore; the mandrel is provided with a matching section, and key teeth and key grooves are alternately arranged on the peripheral surface of the matching section in the circumferential direction; the cam and the transmission unit are sleeved on the matching section of the mandrel, and the inner peripheral surface profiles of the cam and the transmission unit are consistent with the outer peripheral surface profile of the matching section.

2. The camshaft of claim 1 wherein in the cross-sectional profile of the spindle at any axial position, the top surface lines of adjacent key teeth engage the bottom surface lines of the key slots by a straight line, one end of the straight line connects the top surface lines of the key teeth by an arc transition, and the other end of the straight line connects the bottom surface lines of the key slots by an arc transition.

3. A camshaft as claimed in claim 1 or 2, wherein the top surface lines of all the key teeth on the outer peripheral surface of the core shaft belong to the same polygon, and the groove bottom lines of all the key grooves belong to the same polygon.

4. The camshaft of claim 3, wherein: the polygon formed by the top surface lines of the key teeth is concentric with the polygon formed by the groove bottom lines of the key grooves.

5. The camshaft of claim 3, wherein: the straight line forms an angle with a radial plane passing through the axis of the mandrel.

6. The camshaft of claim 1, wherein: the width of the groove bottom of the key groove is smaller than that of the notch of the key groove, and the width of the tooth top of the key tooth is smaller than that of the tooth bottom of the key tooth.

7. The camshaft of claim 1, wherein: the inner peripheral surface of the cam is annularly provided with a groove area and a convex tooth area, the groove area corresponds to the key teeth on the mandrel, the convex tooth area corresponds to the key groove on the mandrel, and two side walls of the groove area are linear walls.

8. The camshaft of claim 7, wherein: the groove bottom width of the groove area is smaller than the groove opening width of the groove area, and the tooth top width of the convex tooth area is smaller than the tooth bottom width of the convex tooth area.

9. The camshaft of claim 1, wherein: the inner peripheral surface of the transmission unit is provided with a notch area and a protruding area which correspond to the key teeth and the key grooves respectively, and two side walls of the notch area are straight walls.

10. The camshaft of claim 9, wherein: the bottom width of the notch area is less than the opening width of the notch area.

11. The camshaft of claim 1, wherein: and machining the outer surface of the mandrel at intervals to form cylindrical sections, wherein the cylindrical sections are journals of the mandrel, and the journals are used for rotating and supporting the camshaft.

12. The camshaft of claim 11, wherein: the outer diameter of the matching section is larger than that of the cylindrical section.

13. The camshaft of claim 1, wherein: and a plug for plugging the shaft hole is arranged at the end part of the mandrel.

14. The camshaft of claim 13, wherein: and one end of the plug inserted into the mandrel is provided with an outer cylindrical surface, and knurling is performed on the outer cylindrical surface.

15. A method of manufacturing a camshaft as claimed in claim 1, comprising: 1) preparing the mandrel, the cam and the transmission unit; the key teeth and the key grooves are formed on the outer peripheral surface of the mandrel in an annular alternating mode;

16. The manufacturing method of a camshaft according to claim 15, wherein: in the cross-sectional profile of the mandrel at any axial position, the top surface lines of all the key teeth belong to the same polygon, and the groove bottom lines of all the key grooves belong to the same polygon.

17. The manufacturing method of a camshaft according to claim 15, wherein: the adjacent key top surface lines are connected with the key groove bottom lines through straight lines; one end of the straight line is connected with the top surface line of the key tooth through arc transition, and the other end of the straight line is connected with the bottom line of the key groove through arc transition.

18. The manufacturing method of a camshaft according to claim 15, wherein: the inner circumferential surface of the cam is provided with a groove area and a convex tooth area which respectively correspond to the key tooth and the key groove; the inner peripheral surface of the transmission unit has a notch area and a protrusion area corresponding to the key teeth and the key grooves, respectively.

19. The manufacturing method of a camshaft according to claim 15, wherein: the specific step of radially expanding the mandrel in step 3) comprises:

20. The manufacturing method of a camshaft according to claim 15, wherein: the specific step of radially expanding the mandrel in step 3) comprises: extending an expansion piece into the shaft hole of the mandrel, so that the matching part of the mandrel, the cam and the transmission unit is expanded along the radial direction; the expansion piece is a steel ball, a cylinder or an elliptic cylinder, and the outer diameter of the cross section of the expansion piece attached to the shaft hole is larger than the inner diameter of the shaft hole.

21. The manufacturing method of a camshaft according to claim 15, wherein: before the cam and the transmission unit are sleeved on the mandrel, cylindrical sections are machined on the outer peripheral surface of the mandrel at intervals of a certain distance, the cylindrical sections form journals, and the journals are used for rotating and supporting the whole camshaft.