Engine

Abstract

The engine comprises a crankcase and a speed change mechanism, the speed change mechanism comprises a power transmission shaft, a speed change gear assembly and a gear shifting fork, the power transmission shaft is installed in the crankcase, the speed change gear assembly is installed on the power transmission shaft, and the gear shifting fork is connected with the speed change gear assembly in a clamped mode; the change gear assembly comprises a gear shifting gear and a free gear, the gear shifting fork is connected with the gear shifting gear in a clamped mode, and the gear shifting gear can move in the axial direction of the power transmission shaft under the action of the gear shifting fork, so that the gear shifting gear is meshed with or separated from the free gear. The gear shifting gear comprises a gear body and an inverted-cone-shaped pawl, the pawl is installed on the gear body and extends in the direction from the gear body to the free gear, the pawl is provided with a first end and a second end which are oppositely arranged, the first end is connected with the gear body, and the width of the first end is smaller than that of the second end. Through the arrangement, the stability when any two gears in the change gear assembly are meshed is improved.

Description

Technical Field

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

[0002] The engine changes the speed and torque from the engine through a speed-changing mechanism. The speed-changing mechanism can fix or change the transmission ratio of the output shaft and the input shaft in gears. The speed-changing mechanism includes a speed-changing gear assembly. By changing the meshing relationship of the gears in the speed-changing gear assembly, the transmission ratio of the output shaft and the input shaft is changed accordingly.

[0003] Among them, ratchet paws and meshing grooves are respectively arranged on two gears. In traditional engines, there is a problem of gear disengagement under the conditions of rapid acceleration, rapid deceleration or heavy load of the vehicle, that is, the two meshing gears are separated, resulting in the interruption of kinetic energy transmission between the output shaft and the input shaft. 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, in which the speed-changing gear assembly can bear a greater load and has higher stability when the gears are meshed.

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

[0006] An engine includes a crankcase, a speed-changing mechanism, a power transmission shaft, a speed-changing gear assembly and a shift fork. The speed-changing mechanism is installed in the crankcase and includes: a power transmission shaft installed in the crankcase and rotatably connected to the crankcase; a speed-changing gear assembly installed on the power transmission shaft; a shift fork that is clamped with the speed-changing gear assembly. The speed-changing gear assembly includes a shift gear and a free gear. The shift fork is clamped with the shift gear. The shift gear can move axially along the power transmission shaft under the action of the shift fork, so that the shift gear meshes with or disengages from the free gear. The shift gear includes a gear body and a ratchet pawl in an inverted conical shape. The ratchet pawl is installed on the gear body and extends from the gear body towards the free gear. The ratchet pawl has a first end and a second end arranged oppositely. 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.

[0007] Further, the free gear has a meshing groove that cooperates with the ratchet pawl. The shift gear includes a first state and a second state. The first state is the process in which the shift gear meshes with the free gear, and the second state is that the shift gear and the free gear are in mesh and rotate synchronously. When the shift gear is in the first state, the contact area between the ratchet pawl and the meshing groove is defined as the first area. When the shift gear is in the second state, the contact area between the ratchet pawl and the meshing groove is defined as the second area. Among them, the second area is larger than the first area.

[0008] Further, the pawls are uniformly distributed circumferentially along the shift gear.

[0009] Further, the inverted conical pawl has an inclined side wall, and the cone angle formed by the side wall ranges from 89° to 90°.

[0010] Further, the cone angle formed by the side wall ranges from 89.2° to 89.7°.

[0011] Further, the engaging groove has an inner wall extending axially along the power transmission shaft, and the extending direction of the inner wall of the engaging groove is substantially parallel to the axis direction of the free gear.

[0012] Further, the pawl is formed by machining.

[0013] Further, the speed change mechanism includes a shift hub, a plurality of shift forks, and a fork shaft passing through the shift forks. The shift hub and the fork shaft are installed in the crankcase. At least one end of the shift fork facing away from the speed change gear set has a limiting member. The shift fork with the limiting member is defined as the first fork. The first fork abuts against the shift hub through the limiting member, so that the first fork is inclined in a set direction.

[0014] Further, the outer peripheral surface of the shift hub has a number of grooves with specific shapes. One end of the shift fork facing 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 peripheral surface of the shift hub.

[0015] Further, the shift fork includes a second fork. One end of the second fork close to the shift hub is not provided with a limiting member, and the second fork is naturally suspended on the fork shaft.

[0016] The engine improves the pawl of the shift gear, so that the pawl is configured as an inverted cone, and the width of the end of the pawl connected to the gear body is smaller than the width of the end of the pawl facing away from the gear body. In the case of rapid acceleration or deceleration of the vehicle, the meshing relationship between the shift gear and the free gear is made more firm, reducing the risk of the vehicle being out of gear. Description of the Drawings

[0017] Figure 1 Schematic diagram of the overall structure of the engine provided by the embodiment of the present application;

[0018] Figure 2 Schematic diagram of the cylinder head structure 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 For Figure 3 Local enlarged view at A of

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

[0022] Figure 6 A schematic diagram of a partial structure inside the crankcase of the engine provided by the embodiment of the present application;

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

[0024] Figure 8 A schematic diagram of a partial structure of the transmission mechanism of the engine provided by the embodiment of the present application from the first perspective;

[0025] Figure 9 A schematic diagram of a partial structure of the transmission mechanism of the engine provided by the embodiment of the present application from the second perspective;

[0026] Figure 10 For Figure 7 The enlarged partial view at position B of

[0027] Figure 11 A 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 technical solutions in the specific embodiments of the present application will be clearly and completely described below 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 construed 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 such 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 may also be an intervening 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 intervening elements 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 embodiments.

[0031] As Figure 1As shown in the figure, 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 a housing 10, and the housing 10 constitutes the main frame of the engine 100. The housing 10 includes an oil pan 11, a crankcase 12, a cylinder block 13, a cylinder head 14, and a cylinder head cover 15 that are connected in sequence from bottom to top.

[0032] To clearly illustrate the technical solution of the present application, the up-down, left-right, and front-back directions as shown in Figure 2 are also provided as the up-down, left-right, and 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 the fuel-air mixture. The intake manifold 21 communicates with the intake passage 141 and distributes the 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 that are oppositely arranged. The first end 1411 of the intake passage 141 communicates with the air passage of the intake manifold 21 (see Figure 1 ), and the second end 1412 of the intake passage 141 communicates with the combustion chamber 142. The first end 1411 of the intake passage 141 forms an intake port 1411a around it, and the first end 1411 of the intake passage 141 forms a cone 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 2 shown, the end face of the cylinder head 14 connected to the intake manifold 21 is defined as the manifold mounting surface 143. During the initial machining process, the first end 1411 of the intake passage 141 is processed by a machining tool such as a cutting tool or a grinding wheel, 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 from the direction of the intake passage 141 to the intake manifold 21.

[0036] As Figure 3 and Figure 4As shown, as an implementation, 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 becomes too large, affecting 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 portion 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 on 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 As 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 penetrates 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 spatially connected to 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 air 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 air 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 is disposed opposite to the intake passage 141 and faces the front and rear sides of the cylinder head 14 respectively. 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. Thereby, when the exhaust gas is discharged from the engine 100, turbulence is avoided at the exhaust port, and thus the exhaust effect is improved.

[0043] As Figure 6 and Figure 7 As shown, the engine 100 further includes a speed change mechanism 30. The speed change mechanism 30 is installed in the crankcase 12. The speed change 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 operates under favorable working conditions as much as possible and meets the possible driving speed requirements. The speed change mechanism 30 is also used to realize reverse driving to meet the need of the vehicle for reverse driving. The speed change 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 crankcase 121 and a lower crankcase 122 (as Figure 1 shown). An installation space 124 for installing the speed change mechanism 30 is formed between the upper crankcase 121 and the lower crankcase 122. The speed change mechanism 30 includes a shift hub 31, shift forks 32 and shift fork shafts 33. The shift hub 31, shift forks 32 and shift fork shafts 33 are all located in the installation space 124, and the shift hub 31 and the shift fork shafts 33 are both installed on the crankcase 12.

[0045] Specifically, the shift hub 31 is installed on the upper crankcase 121 and fixedly connected to the upper crankcase 121. The shift hub 31 can rotate relative to the upper crankcase 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 with specific shapes are provided on the outer peripheral surface of the shift hub 31. The shift forks 32 are disposed below the shift hub 31, and one end of the shift fork 32 is embedded in the grooves 311. The shift forks 32 are in clearance fit with the grooves 311 so that the shift forks 32 can move relative to the shift hub 31. By driving the positioning star wheel 34 to rotate the shift hub 31, the shift forks 32 move 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 has a 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 speed change mechanism 30 further includes a speed change gear assembly 35. The speed change gear assembly 35 is installed in the lower housing 122, and one end of the shift fork 32 facing away from the shift hub 31 is clamped with some gears in the speed change 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 speed change gear assembly 35 to translate along the direction of the reference line 105.

[0049] The speed change 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 speed change 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 speed change gear assembly 35 connected to the power transmission assembly 36 to rotate. Among them, the speed change gear assembly 35 includes a shift gear 351 and a free gear 352. The free gear 352 has a 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, and at least some of the shift forks 32 have a limiting member 321 at one end facing away from the speed change gear assembly 35. The shift fork 32 with the limiting member 321 is defined as the first shift fork 322. 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 the set direction, wherein, the projection is configured to extend 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 speed change 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 shift fork 32 further includes a second fork 323 without a limiting member 321. When the second fork 323 is connected to the shift hub 31, the second fork 323 is naturally suspended from the fork shaft 33. It should be noted that since the second fork 323 is not provided with the same limiting member 321 as the first fork 322, when the second fork 323 is fixed at the installation position through the fork shaft 33, the second fork 323 is naturally suspended downward under the influence of gravity.

[0052] As Figure 9 shown, the fork shaft 33 includes a first fork shaft 331 and a second fork shaft 332. The first fork 322 and the second fork 323 are respectively suspended from the first fork shaft 331 and the second 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. 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 fork shaft 331 is located obliquely above the power output shaft 362, and the second 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 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 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 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 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 fork 322 from being naturally suspended downward under the influence of gravity, which would lead to the need to manually adjust the inclination direction of the first fork 322, the extension direction of the first fork 322 is changed through the limiting member 321, so that the first 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] With 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 mating process of the crankcase, thereby enhancing the safety of the production process of the engine 100.

[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 mating process of the upper crankcase 121 and the lower crankcase 122, making the mating of the upper crankcase 121 and the lower crankcase 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, an elastic member 37 is provided at the end of the fork shaft 33, and the fork shaft 33 abuts against the inner wall of the upper crankcase 121 through the elastic member 37. The elastic member 37 absorbs the vibration transmitted from the crankcase 12 to the fork shaft 33, or the problem of unsmooth gear shifting.

[0058] Specifically, an assembly gap 1211 is formed between the end of the fork shaft 33 and the inner wall of the upper crankcase 121, 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 brought 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. This prevents the elastic member 37 from falling off between the fork shaft 33 and the inner wall of the upper crankcase 121 along the assembly gap 1211.

[0060] It should be noted that the ends of the fork shaft 33 refer to both ends of the fork shaft 33, and the ends 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.

[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 relatively large when the positioning star wheel 34 rotates, which easily causes wear on the outer peripheral surface of the positioning star wheel 34, and for the user experience, the 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 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 cooperating 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 circumferentially along 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 inserted into 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 engages 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 engagement and rotate 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 them, the frictional force between the shift gear 351 and the free gear 352 is increased to ensure the stability of the engagement 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 which are oppositely arranged. 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 engagement 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 is possible to effectively avoid the problem that the contact area between the pawl 3511 and the engagement groove 3521 is too small, resulting in insufficient friction, and prevent the problem of gear disengagement in the transmission mechanism 30. In addition, it is also possible to 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 ranging from 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 high rotational 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 ranging from 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 friction 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: Crankcase; A speed change mechanism, the speed change mechanism is installed in the crankcase, and the speed change mechanism includes: A power transmission shaft, the power transmission shaft is installed in the crankcase and is rotatably connected to the crankcase; A speed change gear assembly, the speed change gear assembly being mounted on the power transmission shaft; A shift fork, the shift fork being engaged with the speed change gear assembly; It is 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 can move along the axial direction of the power transmission shaft under the action of the shift fork, so that the shift gear is engaged with or separated from the free gear; The shift gear includes a gear body and an inverted cone-shaped pawl, wherein the pawl is mounted on the gear body and extends from the gear body toward the free gear, wherein the pawl has a first end and a second end that are oppositely disposed, wherein the first end is connected to the gear body, and a width of the first end is smaller than a width of the second end.

2. The engine according to claim 1, characterized in that The free gear has an engaging groove that cooperates with the ratchet pawl, and the shift gear includes a first state and a second state. The first state is that the shift gear and the free gear are in the process of meshing, and the second state is that the shift gear and the free gear are in the process of completing meshing and rotating synchronously. When the shift gear is in the first state, the size of the contact surface between the ratchet pawl and the engaging groove is defined as a first area, and when the shift gear is in the second state, the size of the contact surface between the ratchet pawl and the engaging groove is defined as a second area, wherein the second area is larger than the first area.

3. The engine according to claim 1, characterized in that The ratchet pawls are evenly distributed along the circumference of the shift gear.

4. The engine according to claim 1, characterized in that The inverted tapered pawl has an inclined side wall, and the cone angle formed by the side wall ranges from 89° to 90°.

5. The engine according to claim 4, characterized in that The cone angle formed by the side wall ranges from 89.2° to 89.7°.

6. The engine according to claim 2, characterized in that The meshing groove has an inner wall extending in the axial direction of the power transmission shaft, and an extending direction of the inner wall of the meshing groove is substantially parallel to an axial direction of the free gear.

7. The engine according to claim 1, characterized in that The pawl is formed by machining.

8. The engine according to claim 1, characterized in that The speed shifting mechanism includes a shift hub, a plurality of shift forks and a fork shaft passing through the shift forks, the shift hub and the fork shaft are mounted on the crankcase, at least part of the shift forks have a limiter at one end away from the speed gear set, the shift fork with the limiter is defined as a first shift fork, the first shift fork abuts against the shift hub through the limiter, so that the first shift fork tilts along a set direction.

9. The engine according to claim 8, characterized in that The outer circumference of the shift hub has a plurality of grooves of specific shapes, one end of the shift fork away from the speed change gear assembly is embedded in the groove, and the limiter is located outside the groove and abuts against the outer circumference of the shift hub.

10. The engine according to claim 8, characterized in that The shift fork comprises a second shift fork, an end of the second shift fork close to the shift hub is not provided with the limiting member, and the second shift fork is naturally suspended on the shift fork shaft.

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