Engine

Abstract

The engine comprises a crankcase and a speed change mechanism, the crankcase forms a mounting space, and the speed change mechanism is arranged in the mounting space; the speed change mechanism comprises a gear shifting hub, a gear shifting fork, a shifting fork shaft and a speed change gear assembly, the gear shifting hub and the shifting fork shaft are both installed on the crankcase, the shifting fork shaft penetrates through the gear shifting fork and is in clearance fit with the gear shifting fork, one end of the gear shifting fork is connected with the gear shifting hub, and the other end of the gear shifting fork is connected with the speed change gear assembly in a clamped mode; the shifting fork shafts comprise the first shifting fork shaft and the second shifting fork shaft, the gear shifting fork comprises the first shifting fork and the second shifting fork, the first shifting fork and the second shifting fork are hung on the first shifting fork shaft and the second shifting fork shaft respectively, a limiting piece is arranged at the end, close to the gear shifting hub, of the first shifting fork, and the first shifting fork abuts against the gear shifting hub through the limiting piece. Therefore, the first shifting fork inclines along the set direction. The engine is high in assembly efficiency, and potential safety hazards can be avoided in the assembly process.

Description

Technical Field

[0001] This application relates to the technical field of power systems, and in particular, to an engine. Background Art

[0002] The speed-changing mechanism of a motorcycle is generally arranged in the crankcase of the engine. The crankcase is divided into upper and lower boxes. The speed-changing mechanism includes a shift hub, shift forks, fork shafts, and a speed-changing gear assembly. The shift hub, shift forks, and fork shafts are arranged in the crankcase, and the speed-changing gear assembly is arranged in the lower box.

[0003] During the assembly process of the crankcase, the upper box assembled with the shift hub, shift forks, and fork shafts is covered on the lower box, and during the docking process, the shift forks are made to catch the speed-changing gear assembly located in the lower box. Since the shift forks are in a vertically downward hanging state under the action of gravity, the installer needs to manually adjust the position of the shift forks so that the shift forks can be engaged with the speed-changing gear assembly. On the one hand, it affects the assembly efficiency of the engine, and on the other hand, manual adjustment will cause certain safety hazards. Utility Model Content

[0004] In order to solve the deficiencies of the prior art, the purpose of the present utility model is to provide an engine with high assembly efficiency and can avoid safety hazards during the assembly process.

[0005] To achieve the above purpose, the present application adopts the following technical solutions:

[0006] An engine, which includes a crankcase and a speed-changing mechanism. The crankcase forms an installation space, and the speed-changing mechanism is arranged in the installation space; the speed-changing mechanism includes a shift hub, shift forks, fork shafts, and a speed-changing gear assembly. The shift hub and the fork shafts are both installed on the crankcase. The fork shafts pass through the shift forks and are in clearance fit with the shift forks. One end of the shift fork is connected to the shift hub, and the other end of the shift fork is engaged with the speed-changing gear assembly; the fork shafts include a first fork shaft and a second fork shaft, the shift forks include a first shift fork and a second shift fork. The first shift fork and the second shift fork are respectively suspended on the first fork shaft and the second fork shaft. A limiting member is provided at one end of the first shift fork close to the shift hub. The first shift fork abuts against the shift hub through the limiting member so that the first shift fork inclines in a set direction.

[0007] Further, the outer peripheral surface of the shift hub has a groove. One end of the shift fork facing away from the speed-changing gear assembly is embedded in the groove. The limiting member is located outside the groove and abuts against the outer peripheral surface of the shift hub.

[0008] Further, the limiting member is a protrusion extending from the first shift fork towards the shift hub.

[0009] Further, the speed change mechanism includes a power input shaft and a power output shaft. The first fork shaft is located obliquely above the power input shaft, and the second fork shaft is located directly above the power output shaft. Define a projection plane perpendicular to the first fork shaft. The projection of the axis of the first fork shaft on the projection plane along the extension direction of the first fork shaft is defined as the first projection point, and the projection of the axis of the power input shaft on the projection plane along the extension direction of the first fork shaft is defined as the second projection point. The extension direction from the first projection point to the second projection point is the set direction.

[0010] Further, elastic members are provided at both ends of the first fork shaft and both ends of the second fork shaft. The first fork shaft and the second fork shaft are in contact with the inner wall of the crankcase through the elastic members.

[0011] Further, an assembly gap is formed between both ends of the first fork shaft and both ends of the second fork shaft and the inner wall of the crankcase, and at least part of the elastic member is located in the assembly gap.

[0012] Further, a receiving groove that is recessed inward is formed at the end of the fork shaft, and at least part of the elastic member is provided in the receiving groove.

[0013] Further, the speed change mechanism further includes a positioning star wheel and a positioning rocker arm assembly. The positioning star wheel is provided at one end of the shift hub and is fixedly connected to the shift hub. The positioning rocker arm assembly is fixedly installed on the crankcase and abuts against the positioning star wheel. Among them, the positioning rocker arm assembly includes a bearing for abutting against the outer edge of the positioning star wheel.

[0014] Further, the positioning rocker arm assembly includes a rocker arm. One end of the rocker arm is connected to the crankcase through a fastener, and the rocker arm can rotate around the fastener. The bearing is provided at the end of the rocker arm away from the fastener.

[0015] Further, the speed change gear assembly includes a shift gear and a free gear. The shift fork is clamped with the shift gear. The shift gear is configured to be engaged with or separated from the free gear under the action of the shift fork. The shift gear includes a gear body and an inverted conical pawl. The pawl is installed on the gear body and extends from the gear body towards the free gear. The pawl has a first end and a second end. The first end is connected to the gear body, and the width of the first end is smaller than the width of the second end.

[0016] By providing a limiting member at one end of the first fork shaft and making the limiting member abut against the shift hub, the engine makes the first fork tilt along the set direction. When the upper and lower crankcases are assembled, the end of the first fork away from the shift hub can accurately engage with the speed change gear assembly, so that the assembly efficiency of the engine is high and potential safety hazards can be avoided during the assembly process. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the overall structure of the engine provided by the embodiment of the present application;

[0018] Figure 2 Structural schematic diagram of the cylinder head of the engine provided by the embodiment of the present application;

[0019] Figure 3 Cross-sectional view of the cylinder head of the engine provided by the embodiment of the present application;

[0020] Figure 4 is Figure 3 Partial enlarged view of the A position of

[0021] Figure 5 Cross-sectional view of the cylinder head and intake manifold of the engine provided by the embodiment of the present application;

[0022] Figure 6 Schematic diagram of a part of the internal structure of the crankcase of the engine provided by the embodiment of the present application;

[0023] Figure 7 Schematic diagram of the transmission mechanism of the engine provided by the embodiment of the present application;

[0024] Figure 8 Schematic diagram of a part of the transmission mechanism of the engine provided by the embodiment of the present application from the first perspective;

[0025] Figure 9 Schematic diagram of a part of the transmission mechanism of the engine provided by the embodiment of the present application from the second perspective;

[0026] Figure 10 is Figure 7 Partial enlarged view of the B position of

[0027] Figure 11 Schematic diagram of the structure of the transmission gear of the engine provided by the embodiment of the present application. Specific embodiments

[0028] In order to enable those skilled in the art to better understand the solution of the present application, the following will clearly and completely describe the technical solutions in the specific embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application.

[0029] The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. "First", "second", "third", "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", "third", "fourth" may explicitly or implicitly include at least one of the features. The singular forms "a", "the" and "said" used in the present application and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise.

[0030] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only implementation.

[0031] As Figure 1 shown, the present application provides an engine 100, which can be used as a power supply device for vehicles such as automobiles and motorcycles. In the embodiments of the present application, the engine 100 belongs to a reciprocating piston internal combustion engine, which can convert the chemical energy of fuel into the mechanical energy of piston movement and output power externally. The engine 100 includes an outer housing 10, and the outer housing 10 constitutes the main frame of the engine 100. The outer housing 10 includes an oil pan 11, a crankcase 12, a cylinder block 13, a cylinder head 14 and a cylinder head cover 15 connected in sequence from bottom to top.

[0032] To clearly illustrate the technical solution of the present application, the up-down, left-right, front-back directions as shown in Figure 2 are also provided as the up-down, left-right, front-back directions of the cylinder head 14.

[0033] As Figures 1 to 3 shown, the engine 100 further includes an intake and exhaust system 20. The intake and exhaust system 20 includes an intake manifold 21. The intake manifold 21 is connected to the cylinder head 14. The cylinder head 14 includes an intake passage 141 and a combustion chamber 142 for burning fuel-air mixture. The intake manifold 21 is in communication with the intake passage 141 and distributes air and fuel-air mixture as evenly as possible into each intake passage 141 to ensure that the combustion efficiency in each combustion chamber 142 is basically the same, making the power output of the engine 100 more stable.

[0034] As Figure 3 shown, as an implementation, the intake passage 141 has a first end 1411 and a second end 1412 arranged opposite to each other. The first end 1411 of the intake passage 141 is in communication with the air passage of the intake manifold 21 (see Figure 1 ), and the second end 1412 of the intake passage 141 is in communication with the combustion chamber 142. The first end 1411 of the intake passage 141 surrounds to form an intake port 1411a, and the first end 1411 of the intake passage 141 forms a taper angle that expands outward with the central axis of the intake port 1411a as the center. Thereby increasing the intake air volume of the engine 100 and improving the air flow turbulence at the intake port 1411a.

[0035] As Figure 2As shown, the end face where the cylinder head 14 is connected to the intake manifold 21 is defined as the manifold mounting surface 143. During the initial machining process, a machining tool such as a cutting tool or a grinding wheel is used to process the first end 1411 of the intake passage 141, so that an included angle is formed between the inner wall of the first end 1411 and the manifold mounting surface 143, that is, the aperture of the first end 1411 gradually expands in the direction from the intake passage 141 to the intake manifold 21.

[0036] As Figure 3 and Figure 4 shown, as an implementation manner, a projection plane 101 perpendicular to the left - right direction of the cylinder head 14 is defined. The projection of the central axis of the air inlet 1411a in the left - right direction of the cylinder head 14 on the projection plane 101 is defined as the first projection line 102, and the projection of the inner wall of the first end 1411 in the left - right direction of the cylinder head 14 on the projection plane 101 is defined as the second projection line 103. The included angle α between the first projection line 102 and the second projection line 103 ranges from 5° to 15°. Further, the included angle α between the first projection line 102 and the second projection line 103 ranges from 7° to 13°. More preferably, the included angle α between the first projection line 102 and the second projection line 103 is equal to 10°. It should be noted that since the included angle α between the first projection line 102 and the second projection line 103 determines the aperture of the first end 1411, if the included angle α is too small, the increase in the aperture of the first end 1411 is limited, and the improvement in the intake air volume in the intake passage 141 is small. If the included angle α is too large, the aperture of the first end 1411 is too large, which affects the assembly of the intake manifold 21 and the cylinder head 14, and may cause poor sealing at the air inlet 1411a. Through the above settings, while ensuring the stability and convenience of the assembly of the intake manifold 21 and the cylinder head 14, the intake air volume in the intake passage 141 is increased as much as possible, thereby improving the combustion efficiency of the engine 100.

[0037] Specifically, the intake passage 141 includes an airway main body 1413 that constitutes the basic shape of the intake passage 141. The airway main body 1413 is located between the first end 1411 and the second end 1412. An arc - shaped chamfer is provided at the part where the inner wall of the airway main body 1413 is connected to the inner wall of the first end 1411. According to the foregoing, since the first end 1411 of the intake passage 141 is machined to form a taper angle that expands outward with the central axis of the air inlet 1411a as the center, in the initial machining stage, the intersection range between the first end 1411 of the intake passage 141 and the airway main body 1413 is a fold angle of 0° to 180°. In order to avoid the influence of this fold angle on the intake air volume in the intake passage 141, the fold angle is further machined into an arc - shaped chamfer, thereby avoiding the first end 1411 from generating turbulent flow to the gas when the gas enters the intake passage 141 and improving the intake air volume in the intake passage 141.

[0038] As an implementation, the length L1 of the first end 1411 extending along the axial direction of the air inlet 1411a ranges from 1 mm to 3 mm. Further, the length of the first end 1411 extending along the axial direction of the air inlet 1411a ranges from 1.5 mm to 2.5 mm. More preferably, the length of the first end 1411 extending along the axial direction of the air inlet 1411a is equal to 2 mm. It should be noted that the length of the first end 1411 extending along the axial direction of the air inlet 1411a and the aperture diameter of the first end 1411 directly affect the air intake volume of the air intake passage 141. And when the length of the first end 1411 extending along the axial direction of the air inlet 1411a is too large, in order to meet the above requirements for the angle α between the first projection line 102 and the second projection line 103, it will inevitably lead to an increase in the aperture diameter of the first end 1411, and the increase in the aperture diameter of the first end 1411 may also affect the assembly of the intake manifold 21. Therefore, through the above settings, while ensuring the stability and convenience of the assembly of the intake manifold 21 and the cylinder head 14, the air intake volume in the air intake passage 141 is increased as much as possible, thereby improving the combustion efficiency of the engine 100.

[0039] As Figure 5 shown, as an implementation, the intake and exhaust system 20 further includes a seat ring 22. The seat ring 22 is disposed between the intake manifold 21 and the cylinder head 14. The seat ring 22 is penetrated in the direction from the intake manifold 21 to the cylinder head 14 to form an air delivery passage 221. The air intake passage 141 is in spatial communication with the intake manifold 21 through the air delivery passage 221. The aperture diameter of the air delivery passage 221 decreases in the direction from the cylinder head 14 to the intake manifold 21.

[0040] Since the outlet of the intake manifold 21 or the pipe for outputting gas of the intake manifold 21 is a standard part, in order to avoid the non-correspondence between the outlet of the intake manifold 21 and the air inlet 1411a of the cylinder head 14, the seat ring 22 between the intake manifold 21 and the cylinder head 14 can effectively ensure the air flow transmission between the two, and avoid problems such as air leakage and reduction of gas flow rate.

[0041] Further, the aperture diameter of the end of the air delivery passage 221 facing the cylinder head 14 is greater than or equal to the aperture diameter of the air inlet 1411a, so as to avoid the possibility of the seat ring 22 disturbing the gas at the air inlet 1411a.

[0042] As Figure 3As shown, as an alternative implementation, the cylinder head 14 further includes an exhaust passage 144. The exhaust passage 144 and the intake passage 141 are disposed opposite to each other and respectively face the front and rear sides of the cylinder head 14. One end of the exhaust passage 144 communicates with the combustion chamber 142, and the exhaust gas in the combustion chamber 142 is discharged from the engine 100 through the exhaust passage 144. The end of the exhaust passage 144 facing away from the combustion chamber 142 forms an exhaust port for discharging the exhaust gas from the engine 100, and the end of the exhaust passage 144 facing away from the combustion chamber 142 forms a taper angle that expands outward with the central axis of the exhaust port as the center. Thus, when the exhaust gas is discharged from the engine 100, turbulence is avoided at the exhaust port, thereby improving the exhaust effect.

[0043] As Figure 6 and Figure 7 shown, the engine 100 further includes a transmission mechanism 30. The transmission mechanism 30 is installed in the crankcase 12. The transmission mechanism 30 is used to change the transmission ratio of the engine 100 to meet the traction requirements of the vehicle under different driving conditions, so that the engine 100 works as much as possible under favorable working conditions and meets the possible driving speed requirements. The transmission mechanism 30 is also used to achieve reverse driving to meet the need for the vehicle to reverse. The transmission mechanism 30 is also used to interrupt the power transmission of the engine 100. When the engine 100 starts, idles, the vehicle shifts gears or needs to stop for power output, the power transmission from the engine 100 to the drive wheels is interrupted.

[0044] As an implementation, the crankcase 12 includes an upper housing 121 and a lower housing 122 (as Figure 1 shown). An installation space 124 for installing the transmission mechanism 30 is formed between the upper housing 121 and the lower housing 122. The transmission mechanism 30 includes a shift hub 31, a shift fork 32 and a fork shaft 33. The shift hub 31, the shift fork 32 and the fork shaft 33 are all located in the installation space 124, and the shift hub 31 and the fork shaft 33 are both installed on the crankcase 12.

[0045] Specifically, the shift hub 31 is installed on the upper housing 121 and fixedly connected to the upper housing 121. The shift hub 31 can rotate relative to the upper housing 121 along its circumferential direction. One end of the shift hub 31 is provided with a positioning star wheel 34 connected to the shift hub 31. The positioning star wheel 34 is fixedly connected to the shift hub 31 so that the positioning star wheel 34 rotates synchronously with the shift hub 31.

[0046] A plurality of grooves 311 are provided on the outer peripheral surface of the shift hub 31. The shift fork 32 is disposed below the shift hub 31, and one end of the shift fork 32 is embedded in the grooves 311. The shift fork 32 is in clearance fit with the grooves 311 so that the shift fork 32 can move relative to the shift hub 31. By driving the positioning star wheel 34 to rotate the shift hub 31, the shift fork 32 moves along the extending direction of the grooves 311.

[0047] The shift fork shaft 33 is installed in the upper housing 121 and fixedly connected to the upper housing 121. The shift fork shaft 33 passes through the shift fork 32 and is in clearance fit with the shift fork 32. A reference line 105 parallel to the axis of the shift hub 31 is defined, and the axis of the shift fork shaft 33 is substantially parallel to the reference line 105.

[0048] The transmission mechanism 30 further includes a transmission gear assembly 35. The transmission gear assembly 35 is installed in the lower housing 122. One end of the shift fork 32 facing away from the shift hub 31 is clamped with some gears in the transmission gear assembly 35. When the shift hub 31 rotates, the shift fork 32 moves under the restriction of the groove 311 and drives some gears in the transmission gear assembly 35 to translate along the direction of the reference line 105.

[0049] The transmission mechanism 30 further includes a power transmission assembly 36. The power transmission assembly 36 is arranged between the upper housing 121 and the lower housing 122 and is rotatably connected to the crankcase 12. The power transmission assembly 36 extends substantially along the direction of the reference line 105. The power transmission assembly 36 is in transmission connection with the crankshaft (not shown in the figure) of the engine 100. The transmission gear assembly 35 is arranged on the power transmission assembly 36 and is driven by the crankshaft to drive the power transmission assembly 36 and the transmission gear assembly 35 connected to the power transmission assembly 36 to rotate. Among them, the transmission gear assembly 35 includes a shift gear 351 and a free gear 352. The free gear 352 is in clearance fit with the power transmission assembly 36. The shift gear 351 is splined to the power transmission assembly 36, and the shift gear 351 has a degree of freedom of movement along the direction of the reference line 105. One end of the shift fork 32 facing away from the shift hub 31 is clamped with the shift gear 351. When the positioning star wheel 34 drives the shift hub 31 to rotate, the shift fork 32 moves under the restriction of the groove 311, and then drives the shift gear 351 to move along the direction of the reference line 105. The shift gear 351 meshes with the corresponding free gear 352 to achieve gear selection.

[0050] As Figure 8 shown, specifically, the number of the shift forks 32 is set to several. At least some of the shift forks 32 have a limiting member 321 at one end facing away from the transmission gear assembly 35. The shift fork 32 includes a first shift fork 322 and a second shift fork 323. The first shift fork 322 is provided with the limiting member 321. The first shift fork 322 abuts against the shift hub 31 through the limiting member 321, so that the first shift fork 322 is inclined in a set direction. Among them, the limiting member 321 is configured as a protrusion extending from the first shift fork 322 to the direction of the shift hub 31. It should be noted that one end of the shift fork 32 facing away from the transmission gear assembly 35 is embedded in the groove 311, and the limiting member 321 is located outside the groove 311 and abuts against the outer peripheral surface of the shift hub 31.

[0051] Further, the second shift fork 323 does not have a limiting member 321. When the second shift fork 323 is connected to the shift hub 31, the second shift fork 323 is naturally suspended on the shift fork shaft 33. It should be noted that since the second shift fork 323 is not provided with the same limiting member 321 as the first shift fork 322, when the second shift fork 323 is fixed at the installation position through the shift fork shaft 33, the second shift fork 323 is naturally suspended downward under the influence of gravity.

[0052] As Figure 9 shown, the shift fork shaft 33 includes a first shift fork shaft 331 and a second shift fork shaft 332. The first shift fork 322 and the second shift fork 323 are respectively suspended on the first shift fork shaft 331 and the second shift fork shaft 332. The power transmission assembly 36 includes a power input shaft 361 and a power output shaft 362 that extend substantially along the direction of the reference line 105 (see Figure 7 ), both of which are installed in the crankcase 12 and can rotate relative to the crankcase 12 along their circumferences. The power input shaft 361 is connected to the crankshaft, and the power input shaft 361 is drivingly connected to the power output shaft 362 through a speed change gear assembly 35 to achieve power transmission. The power output shaft 362 transmits the power outside the engine 100 to achieve power transmission to the drive wheels. The first shift fork shaft 331 is located obliquely above the power output shaft 362, and the second shift fork shaft 332 is located directly above the power input shaft 361.

[0053] In the example of the present application, the axial direction of the first shift fork shaft 331 is substantially parallel to the left - right direction of the cylinder head 14, that is, the reference line 105 is parallel to the left - right direction of the cylinder head 14. Therefore, the projection of the axis of the first shift fork shaft 331 along the direction of the reference line 105 on the projection plane 101 is defined as the first projection point, and the projection of the axis of the power output shaft 362 along the direction of the reference line 105 on the projection plane 101 is defined as the second projection point. The extension direction from the first projection point to the second projection point is the set direction 105.

[0054] It should be noted that during the assembly process of the crankcase 12, the shift hub 31, the shift fork 32, and the shift fork shaft 33 are installed on the upper housing 121, the speed change gear assembly 35 is arranged on the power transmission assembly 36, and the power transmission assembly 36 is installed on the lower housing 122. Since the first shift fork shaft 331 is located obliquely above the power output shaft 362, during the process of closing the housing, in order to prevent the first shift fork 322 from being naturally suspended downward under the influence of gravity, which may lead to the need to manually adjust the inclination direction of the first shift fork 322, the extension direction of the first shift fork 322 is changed through the limiting member 321 so that the first shift fork 322 extends along the set direction and can be engaged with a part of the speed change gear assembly 35 installed on the power output shaft 362.

[0055] Through the above settings, the overall assembly efficiency of the engine 100 is improved, and there is no need to manually adjust the extension direction of the first fork 322 during the casing assembly process, thereby enhancing the safety of the engine 100 production process.

[0056] Since the gears of the transmission gear assembly 35 have certain dimensional requirements to meet the strength and transmission ratio of the transmission gear assembly 35, the interval between the power input shaft 361 and the power output shaft 362 is greater than the interval between the first fork shaft 331 and the second fork shaft 332. Therefore, in order to enable the fork shaft 33 to have a more reasonable layout space, by providing a limiting member 321 on the first fork 322 that abuts against the shift hub 31, there is no need to manually adjust the inclination of the first fork 322 along the set direction during the casing assembly process, making the casing assembly of the upper casing 121 and the lower casing 122 more convenient and safer. As an alternative implementation, when the first fork shaft 331 is obliquely above the power output shaft 362 and the second fork shaft 332 is simultaneously obliquely above the power input shaft 361, limiting members 321 can be provided on both the first fork 322 and the second fork 323 to change their respective extension directions, so as to improve the assembly efficiency of the engine 100.

[0057] As Figure 9 shown, as an implementation, elastic members 37 are provided at both ends of the first fork shaft 331 and both ends of the second fork shaft 332, and the first fork shaft 331 and the second fork shaft 332 are in contact with the inner wall of the crankcase 12 through the elastic members 37. The elastic members 37 absorb the vibration transmitted from the crankcase 12 to the fork shaft 33, solving the problem of unsmooth gear shifting of the vehicle.

[0058] Specifically, an assembly gap 1211 is formed between both ends of the first fork shaft 331 and both ends of the second fork shaft 332 and the inner wall of the crankcase 12, and at least a part of the elastic member 37 is located in the assembly gap 1211. Through the reserved assembly gap 1211, it is possible for the fork shaft 33 to move in a direction parallel to the reference line 105, thereby eliminating the influence caused by the vibration of the engine 100.

[0059] More specifically, a receiving groove 333 that is recessed inward is formed at the end of the fork shaft 33, and at least a part of the elastic member 37 is provided in the receiving groove 333. Thereby preventing the elastic member 37 from falling off between the fork shaft 33 and the inner wall of the upper casing 121 along the assembly gap 1211.

[0060] It should be noted that the end of the fork shaft 33 refers to both ends of the fork shaft 33, and the end of the fork shaft 33 being recessed inward means that both ends of the fork shaft 33 are recessed toward the center point of the fork shaft 33.

[0061] As Figure 8 and Figure 9As shown, as an implementation, the speed change mechanism 30 further includes a positioning rocker arm assembly 38. The positioning rocker arm assembly 38 is fixedly installed on the upper crankcase 12, and the positioning rocker arm assembly 38 and the positioning star wheel 34 are installed on the same side of the shift hub 31. The positioning rocker arm assembly 38 abuts against the outer peripheral surface of the positioning star wheel 34. When the speed change mechanism 30 is in any gear position, the rotation of the positioning star wheel 34 is restricted by the positioning rocker arm assembly 38 to prevent the speed change mechanism 30 from being out of gear or failing to engage gears.

[0062] The positioning rocker arm assembly 38 includes a rocker arm 381 and a bearing 382 provided at one end of the rocker arm 381. The bearing 382 is rotatably connected to the rocker arm 381. When the positioning star wheel 34 rotates, the shift hub 31 rotates synchronously with the positioning star wheel 34, and the meshing relationship between the shift gear 351 and the free gear 352 is adjusted through the shift fork 32 to achieve gear shifting. At the same time, the bearing 382 moves along the outer peripheral surface of the positioning star wheel 34 as the positioning star wheel 34 rotates, and applies a continuous force to the positioning star wheel 34 to ensure the stability of the shift hub 31.

[0063] It should be noted that in the related art, generally a roller formed by stamping is provided to abut against the positioning star wheel 34. However, due to the relatively rough outer peripheral surface of the roller formed by stamping, the frictional resistance between the two is large when the positioning star wheel 34 rotates, which easily causes wear to the outer peripheral surface of the positioning star wheel 34, and for the user experience, the gear shifting is not smooth enough. It can be understood that since the outer peripheral surface of the bearing 382 is smoother and the frictional force of the bearing 382 during rolling is smaller, replacing the roller formed by stamping with the bearing 382 reduces the wear between the bearing 382 and the positioning star wheel 34 and makes the gear shifting smoother.

[0064] As Figure 10 and Figure 11 shown, as an implementation, the shift fork 32 is snap-connected to the shift gear 351. The shift fork 32 is used to drive the shift gear 351 to move along the direction of the reference line 105, so that the shift gear 351 meshes with or disengages from the free gear 352. The shift gear 351 has a pawl 3511 extending in the direction towards the free gear 352, and the free gear 352 has an engaging groove 3521 that cooperates with the pawl 3511. It should be noted that the free gear 352 also has a pawl structure 2522 that is basically the same as the pawl 3511. The pawl structures 2522 are arranged along the circumferential direction of the free gear 352, and an engaging groove 3521 for the pawl 3511 to insert is formed between two adjacent pawl structures 2522. When the shift fork 32 drives the shift gear 351 to move along the direction of the reference line 105 until the pawl 3511 is embedded in the engaging groove 3521, the shift gear 351 meshes with the free gear 352, and the two rotate synchronously.

[0065] The shift gear 351 includes a first state and a second state. The first state is the stage before the shift gear 351 meshes with the free gear 352, that is, the stage before the shift gear 351 moves axially along the power transmission assembly 36 until the pawl 3511 is embedded in the engagement groove 3521. The second state is the state where the shift gear 351 and the free gear 352 are in complete meshing and rotating synchronously. When the shift gear 351 is in the first state, the contact area between the pawl 3511 and the engagement groove 3521 is defined as the first area. When the shift gear 351 is in the second state, the contact area between the pawl 3511 and the engagement groove 3521 is defined as the second area, and the second area is larger than the first area. By increasing the contact area between the two, the friction between the shift gear 351 and the free gear 352 is increased to ensure the stability of the meshing between the shift gear 351 and the free gear 352, and to avoid the problem of gear disengagement in the transmission mechanism 30 during the user's driving of the vehicle.

[0066] Specifically, the shift gear 351 includes a gear body 3512 and a pawl 3511 integrally formed with the gear body 3512. The pawl 3511 is in an inverted conical shape, that is, the pawl 3511 has a first end 3511a and a second end 3511b arranged oppositely. The first end 3511a of the pawl 3511 is connected to the gear body 3512, and the second end 3511b of the pawl 3511 can be embedded in the engagement groove 3521 and abuts against one side end face of the engagement groove 3521 (this end face can be the side face of any one of the two pawl structures 3522 that make up the engagement groove 3521, specifically depending on the rotation direction of the shift gear 351). The width of the first end 3511a of the pawl 3511 is smaller than the width of the second end 3511b of the pawl 3511. By providing the inverted conical pawl 3511, when the shift gear 351 is in the second state, there is a larger contact area between the pawl 3511 and the engagement groove 3521.

[0067] Furthermore, the pawls 3511 are evenly distributed along the circumferential direction of the shift gear 351. By providing a plurality of pawls 3511 and engagement grooves 3521, the stability of the meshing between the shift gear 351 and the free gear 352 is improved.

[0068] As an implementation, the inverted conical pawl 3511 has an inclined side wall 3511c, and the cone angle formed by the side wall 3511c ranges from 89° to 90°. Further, the cone angle formed by the side wall 3511c ranges from 89.2° to 89.7°. More preferably, the cone angle formed by the side wall 3511c is equal to 89.5°. Through the above settings, it can effectively avoid the problem that the contact area between the pawl 3511 and the engagement groove 3521 is too small, resulting in insufficient frictional force, and prevent the problem of gear disengagement of the transmission mechanism 30. In addition, it can also avoid the problem that it is difficult to separate the shift gear 351 and the free gear 352 due to too large a cone angle.

[0069] It should be noted that for conventional vehicles, by setting a cone angle in the range of 89° to 90°, the stability when the shift gear 351 and the free gear 352 are engaged can be improved. However, for racing vehicles, since their engines 100 maintain a relatively high speed and need to quickly complete gear shifting in a high-speed environment, the requirement for gear stability is higher. For the engine 100 of the above-mentioned racing vehicles, the pawl 3511 of the shift gear 351 can be set with a larger cone angle, such as in the range of 86° to 89°, so as to ensure the stability of the transmission system.

[0070] Further, the engagement groove 3521 has an inner wall extending along the axial direction of the power transmission component 36, and the extending direction of the inner wall of the engagement groove 3521 is substantially parallel to the extending direction of the reference line 105. Therefore, by only machining the side wall 3511c of the pawl 3511, the frictional force between the pawl 3511 and the engagement groove 3521 can be increased, and the machining difficulty can be reduced.

[0071] Exemplarily, the pawl 3511 is formed by machining.

[0072] It should be understood that for those of ordinary skill in the art, modifications or variations can be made according to the above description, and all such modifications and variations should fall within the protection scope of the appended claims of this application.

Claims

1. An engine, comprising: A crankcase, wherein the crankcase forms an installation space; a speed change mechanism, wherein the speed change mechanism is arranged in the installation space; It is characterized in that The speed change mechanism comprises a shift hub, a shift fork, a shift fork shaft and a speed change gear assembly, wherein the shift hub and the shift fork shaft are both mounted on the crankcase, the shift fork shaft passes through the shift fork and is in clearance fit with the shift fork, one end of the shift fork is connected to the shift hub, and the other end of the shift fork is clamped with the speed change gear assembly; The fork shaft includes a first fork shaft and a second fork shaft, and the shift fork includes a first fork and a second fork, the first fork and the second fork are suspended on the first fork shaft and the second fork shaft respectively, a limit piece is provided at one end of the first fork close to the shift hub, and the first fork abuts against the shift hub through the limit piece so that the first fork tilts along a set direction.

2. The engine according to claim 1, characterized in that The outer circumferential surface of the shift hub has a groove, one end of the shift fork away from the speed change gear assembly is embedded in the groove, and the limiting member is located outside the groove and abuts against the outer circumferential surface of the shift hub.

3. The engine according to claim 1, characterized in that The limiting member is a protrusion extending from the first shift fork toward the shift hub.

4. The engine according to claim 1, characterized in that The speed change mechanism comprises a power input shaft and a power output shaft, the first shift fork shaft is located obliquely above the power input shaft, and the second shift fork shaft is located directly above the power output shaft; A projection plane perpendicular to the first fork shaft is defined, and the projection of the axis of the first fork shaft along the extension direction of the first fork shaft on the projection plane is defined as a first projection point, and the projection of the axis of the power input shaft along the extension direction of the first fork shaft on the projection plane is defined as a second projection point, and the extension direction from the first projection point to the second projection point is the set direction.

5. The engine according to claim 1, characterized in that Both ends of the first fork shaft and both ends of the second fork shaft are provided with elastic members, and the first fork shaft and the second fork shaft abut against the inner wall of the crankcase through the elastic members.

6. The engine according to claim 5, characterized in that An assembly gap is formed between both ends of the first shift fork shaft and the inner wall of the crankcase, and at least a portion of the elastic member is located in the assembly gap.

7. The engine according to claim 6, characterized in that An inwardly recessed receiving groove is formed at the end of the shift fork shaft, and at least a portion of the elastic member is disposed in the receiving groove.

8. The engine according to claim 1, characterized in that The speed change mechanism also includes a positioning star wheel and a positioning rocker arm assembly, wherein the positioning star wheel is arranged at one end of the shift hub and is fixedly connected to the shift hub, and the positioning rocker arm assembly is fixedly installed on the crankcase and abuts against the positioning star wheel, wherein the positioning rocker arm assembly includes a bearing for abutting against the outer edge of the positioning star wheel.

9. The engine according to claim 8, characterized in that The positioning rocker arm assembly comprises a rocker arm, one end of which is connected to the crankcase via a fastener, the rocker arm can rotate around the fastener, and the bearing is arranged at one end of the rocker arm away from the fastener.

10. The engine according to claim 1, characterized in that The speed change gear assembly includes a shift gear and a free gear, the shift fork is engaged with the shift gear, and the shift gear is configured to engage with or disengage from the free gear under the action of the shift fork, the shift gear includes a gear body and an inverted cone-shaped pawl, the pawl is mounted on the gear body and extends from the gear body toward the free gear, the pawl has a first end and a second end, the first end is connected to the gear body, and the width of the first end is smaller than the width of the second end.

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