Internal combustion engine

Abstract

The invention discloses a valve mechanism of an internal combustion engine. The valve mechanism comprises a timing gear, a valve, a valve seat and a valve guide pipe, and is characterized by further comprising a shifting fork, a support, a magnet and a connecting part, wherein the shifting fork is distributed on a shaft body, has a specific phase and corresponds to the valve, the magnet is fixed on the support, and the connecting part is connected with the valve; opening and closing of an air valve are achieved through relative movement between an axial protrusion on a shifting fork on a transmission shaft and a groove in a connecting part, and sealing after the air valve is closed is achieved through cooperation and interaction of a horizontal protrusion on the top of the connecting part and a magnet. The valve spring directly acting on the valve does not exist in the valve mechanism of the internal combustion engine, the phenomenon that when the valve mechanism of the internal combustion engine operates at a high speed, the valve is not closed and is opened by the cam rotating at a high speed is avoided, and the resonance phenomenon generated by the valve spring and the energy loss caused by the valve spring are avoided.

Description

Technical field:

[0001] The present invention relates to an internal combustion engine, and in particular to a valve train of the internal combustion engine. Background technology:

[0002] At present, the valve train of a four-stroke internal combustion engine is composed of a valve train group and a valve group. The valve train group is all the parts from the timing gear to the valve action. Its composition varies depending on the form of the valve train. Its function is to drive the valve to open and close at a fixed time. The composition of the valve group has basically nothing to do with the form of the valve train. When this valve train is working, the valve exists in three states: valve opening process, valve closing process, and valve keeping closed process; the valve opening process is to drive the valve to open directly or indirectly through the rotation of the cam on the camshaft, and compress the valve spring at the same time; the valve closing process is that the valve is driven to close under the tension of the valve spring; the valve keeping closed process is that the valve is kept closed under the pre-tension of the valve spring. Since the forces for opening and closing the valve come from the cam and the valve spring respectively, and the directions of the forces acting on the valve are opposite, it is difficult to achieve perfect coordination when the forces are switched. Usually, when the speed of the internal combustion engine reaches a certain high, the valve is opened by the high-speed rotating cam before it is completely closed, causing the valve to separate from the cam; in addition, when the operating frequency of the valve spring is equal to or an integer multiple of the natural vibration frequency, the valve spring will resonate, and the valve timing will be destroyed during resonance, and the valve will rebound and impact; in addition, since the tension of the valve spring needs to be overcome to open the valve, the valve spring will produce a certain amount of energy loss. Summary of the invention:

[0003] The purpose of the present invention is to overcome the defects of the existing internal combustion engine valve mechanism. By improving the valve transmission method of the internal combustion engine valve mechanism, the two processes of valve opening and valve closing are combined into one process of valve opening and closing, so as to achieve smooth conversion of the direction of the force acting on the valve, eliminate the phenomenon of separation of the mechanism contact parts, eliminate the resonance of the valve spring, and eliminate the energy loss caused by the valve spring.

[0004] Technical solution:

[0005] The valve train of an internal combustion engine of the present invention comprises a timing gear, a valve, a valve guide and a valve seat, and is characterized in that: it also comprises a transmission shaft with a shift fork distributed on the shaft body and corresponding to the valve in a specific phase, a bracket, a magnet fixed on the bracket, and a connecting part connected to the valve; the shift fork is a support arm extending from the inside to the outside of the transmission shaft, and the end of the support arm has an axial protrusion; the bracket is fixed on the cylinder head and is located above the connecting part; one end of the connecting part has a horizontal protrusion, and the other end is connected to at least one of the valves, the middle axial projection of the connecting part is an irregular sector, and its central angle is η, 115°≤η≤145°, the η opening faces the valve, a groove is opened on the disk surface, and the radial projection of the transmission shaft axis intersects perpendicularly with the radial projection of the center line of the bracket, the connecting part and the valve; when the transmission shaft rotates, the axial protrusion at the end of the support arm moves relatively in the groove in some phases, and the fit is a clearance fit, and in other phases, the magnet cooperates with the horizontal protrusion at one end of the connecting part and interacts with each other.

[0006] Beneficial effects:

[0007] The structural feature of the present invention is that the relative movement between the axial protrusion on the shift fork on the transmission shaft and the groove on the connecting part is used to drive the driven part composed of the connecting part and the valve to move up and down, thereby realizing the process from opening to closing of the valve, and the magnet is used to cooperate and interact with the protrusion at one end of the connecting part to realize the sealing after the valve is closed; the two are combined to simplify the valve opening process, closing process, and valve keeping closed state process of the existing internal combustion engine valve mechanism into two parts: the valve "opening and closing" process and the valve "keeping closed state" process. In particular, the present invention realizes the smooth conversion of the direction of the force during the valve opening and closing process. The entire device removes the valve spring directly acting on the valve, so that the valve is effectively controlled during the working process, solves the problem of contact parts detaching when the existing internal combustion engine valve mechanism works at high speed, eliminates the valve spring resonance phenomenon and the energy loss caused by the valve spring.

[0008] 1: Energy consumption of valve spring:

[0009] Known conditions: Complete combustion of 1kg of gasoline can release 46000kj of heat.

[0010] Assumptions: A conventional four-cylinder gasoline engine with four valves in each cylinder runs at 2,000 rpm, with a force of 600N to open each valve and a valve stroke of 10mm for one hour.

[0011] Valve spring energy consumption: = 1 hour * valve working times per minute * number of valves * valve opening force * stroke

[0012] Q (actual valve spring energy consumption) = 60*2000 / 2*16*600*0.01 = 5760 (kj);

[0013] 1L (93# gasoline) = 0.737kg;

[0014] Q(1L-93# gasoline)=46000*0.737=33902(kj);

[0015] Q(actual valve spring fuel consumption) = Q(actual valve energy consumption) / Q(1L-93# gasoline) = 5760 / 33902 = 0.170(L) = 170(ml);

[0016] 2: The influence of resonance on the valve mechanism:

[0017] Due to the existence of valve springs in the existing internal combustion engine valve train, the entire valve train constitutes an elastic system. The operating frequency of the valve spring overlaps with its natural frequency to produce resonance, causing valve rebound impact and affecting the normal operation of the internal combustion engine.

[0018] 3: The impact of high speed on the valve mechanism:

[0019] a: Assume that the speed of an internal combustion engine is 8000 rpm;

[0020] b: Assume that the time it takes for the valve spring to close the valve is 0.02 seconds;

[0021] Because the camshaft speed is half of the crankshaft speed, 8000 / 2 / 60=200 / 3 (rev / second), the time for the camshaft to rotate one circle is 3 / 200 seconds. If the time required for the valve to close under the action of the valve spring tension is greater than 15 thousandths of a second, the valve will not close tightly, and the intake and exhaust valves may even be open, disrupting the normal working cycle of the internal combustion engine. Description of the drawings:

[0022] Figure 1 Schematic diagram of the principle of the present invention;

[0023] Figure 2 Parts diagram of the present invention;

[0024] Figure 3 Assembly diagram of an embodiment of the present invention;

[0025] Figure 4 An exploded view of an embodiment of the present invention;

[0026] Figure 5 Other forms of the present invention 1 assembly diagram;

[0027] Figure 6 Other forms of the present invention 1 Exploded view;

[0028] Figure 7 A schematic diagram of the thrust profile of the valve train of the present invention;

[0029] Figure 8 Schematic diagram of the pressure angle of the valve train of the present invention.

[0030] In the figure, 1 is the timing gear, 2 is the transmission shaft, 2-1 is the axial cylindrical protrusion (roller) on the shift fork, 3 is the connecting part, 3-1 is the top of the connecting part, 3-2 is the groove on the connecting part, 4 is the bracket, 5 is the valve, 6 is the key, 7 is the shaft head lock nut, 9 is the small pin, 10 is the valve guide, 11 is the valve seat, 12 is the magnet, η is the central angle corresponding to the theoretical outline of the groove, η=∠COD, A is the shift fork, and CD is the theoretical outline of the groove. Specific implementation method:

[0031] In the structure of this embodiment, a shift fork with a specific phase is distributed on the transmission shaft, and an axial protrusion is provided on the shift fork. This embodiment realizes the invention by utilizing the protrusion on the shift fork to drive the driven part.

[0032] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown: the active part of the valve train of the internal combustion engine includes a timing gear 1 and a transmission shaft 2, and the driven part includes a connecting part 3 and a valve 5; the valve guide 10 and the valve seat 11 are installed on the cylinder head in a static fit manner.

[0033] Timing gear: In this embodiment, the timing gear 1 is no different from the timing gear used in existing internal combustion engines.

[0034] Transmission shaft: There is an axial cylindrical protrusion 2 - 1 on the fork of the transmission shaft 2 , and the diameter of the protrusion 2 - 1 is equal to the width of the groove 3 - 2 on the connecting part 3 .

[0035] Connection: Figure 2 , Figure 4 As shown: the upper half of the connecting part 3 is a long strip, and the lower half is a crescent shape. The axial projection of the connecting part 3 is an inverted "e" shape, which adopts an asymmetric structure. The connecting part is composed of two inverted "e" shapes. The spacing between the inverted "e" shapes is equal to the axial width of the fork on the transmission shaft 2, and its bottom and top are connected. The lower half of the crescent shape is radially opened with grooves 3-2, and the two grooves 3-2 are opposite and mirror images of each other. The grooves 3-2 are located inside the connecting part 3, and the theoretical contour line CD of the groove is a smooth curve. The central angle corresponding to the theoretical contour line CD of the groove is η, η=∠COD, the η angle opens downward, η+β=360°, 115°≤η≤145°, and there is a vertical hole at the bottom of the connecting part 3. The diameter of the hole is equal to the diameter of the valve stem, and the lower surface of the top 3-1 of the connecting part 3 is a plane.

[0036] Bracket: It is located above the connecting part and fixedly installed on the cylinder head.

[0037] This embodiment is connected in the following manner: Figure 3 As shown: the timing gear 1 is connected to the transmission shaft 2 through a key 6, a keyway and a shaft head lock nut 7; Figure 4 As shown: the shift fork on the transmission shaft 2 is placed in the connecting part 3, and the fork and the connecting part 3 are matched with each other in a clearance fit; the hole at the bottom of the connecting part 3 is matched with the valve stem and is fixedly connected by a pin 9; the magnet 12 is fixedly mounted on the bracket 4, located on the lower surface of the bracket 4 and corresponding to the connecting part 3 one by one.

[0038] When the timing gear 1 drives the transmission shaft 2 to rotate, the top protrusion 3-1 of the connecting part 3 cooperates and interacts with the magnet 12 on the bracket 4 above it, and the valve 5 is in a closed state. At this time, the top protrusion 3-1 of the connecting part 3 and the magnet 12 on the bracket 4 are not attracted and there is still a certain gap. Due to the magnetic force of the magnet 12 on the top protrusion 3-1 of the connecting part 3, the connecting part 3 and the valve 5 produce a movement trend opposite to the opening direction of the valve 5, so that the valve 5 and the valve seat 11 fit tightly, and the sealing of the valve 5 is achieved after the valve 5 is closed. At this time, the rotation angle of the transmission shaft 2 is 360°-η, and the valve 5 is in a closed state within this rotation angle; when the axial cylindrical protrusion 2-1 on the shift fork cooperates with the groove 3-2 on the connecting part 3, the axial cylindrical protrusion 2-1 on the transmission shaft 2 The protrusion 2-1 enters the groove 3-2 on the connecting part 3, and the protrusion 2-1 moves in the groove 3-2. The two are matched in a clearance fit. Since the valve 5 is constrained by the valve guide 10 fixed on the cylinder head in a static fit, the valve 5 and the connecting part 3 can only move along the center line of the valve guide 10. Since the difference between the distance from the point on the theoretical groove contour CD to the axis of the transmission shaft and the radius of gyration OC changes from small to large and then from large to small, when the transmission shaft 2 rotates, the valve 5 gradually opens from the closed state to the maximum lift, and then from the maximum lift to the closed state, completing the opening and closing process of the valve 5. The rotation angle of the transmission shaft 2 in this section is η. Since the sum of the two rotation angles is equal to 360°, as the transmission shaft 2 rotates, it enters the next cycle and repeats itself. [Note: Ф (推程运动角) =η / 2Φ' (回程运动角) =η / 2Ф s ' (近休止角) =βη+β=360°]

[0039] When the axial cylindrical protrusion 2-1 on the transmission shaft 2 fork cooperates with the groove 3-2 on the connecting part 3, when the axial protrusion 3-2 on the transmission shaft 2 fork enters the groove 3-2 of the connecting part 3 and when the axial protrusion 2-1 on the transmission shaft fork separates from the groove 3-2, rigid impact is easily generated, which requires adding a buffer profile to the theoretical profile of the groove. This is also a method often used in the design of cam mechanisms. The theoretical profile of the groove and the buffer profile should meet the following conditions: first, the theoretical profile of the groove and the buffer profile should be continuous, and the tangent of the theoretical profile of the groove at the connection point should be consistent with the tangent of the buffer profile; secondly, the theoretical profile of the groove and the buffer profile are required to have the same curvature to ensure a smooth transition when passing through the connection point to avoid impact and vibration; thirdly, an appropriate gap is maintained between the actual buffer profile and the axial cylindrical protrusion 3-2 on the connecting part 3, and the buffer profile must also meet specific motion laws. In short, the design of the theoretical groove profile and the buffer profile is a key step in the entire mechanism. It is necessary to consider the movement law of the follower, the relationship between the pressure angle of the mechanism and the size of the mechanism, and the selection of appropriate base circle radius and roller radius.

[0040] In addition, in the present invention, when the valve is closed, the top protrusion 3-1 of the connecting portion 3 and the magnet 12 on the bracket 4 are not attracted, and a gap is left between the two without physical contact. Therefore, it constitutes a magnetic spring device, which can simulate the characteristics of a spring to ensure that the valve can fit tightly with the valve seat or the valve seat ring when the valve is closed. This is achieved through the magnetic force of the magnet. The device can also prevent the valve from vibrating when the engine vibrates, thereby maintaining the sealing of the valve and the overall stability of the engine. Although the resistance generated by the magnetic force of the magnet needs to be overcome during the valve opening process, the maximum resistance is only equivalent to the preload of the valve spring during the valve closing period, so it will not cause a large energy loss. (Note: The working temperature in the valve chamber is between 80 and 150 degrees. When using permanent magnets in this temperature environment, it is necessary to select magnetic materials with high thermal stability, such as four-band iron alloys, Sm-Co magnets, etc.) If the magnet 12 on the bracket 4 is an electromagnet, it can also work normally. If the charging period of the electromagnetic coil of the electromagnet is synchronized with the valve closing period of the valve mechanism, during the valve opening process, there is no need to overcome the resistance generated by the magnetic force of the magnet, because the electromagnetic coil of the electromagnet is in a power-off period during this period, and the magnetic force of the magnet is zero. However, this will increase some components such as sensors, making the device complicated.

[0041] In the above-mentioned embodiments, the valve mechanism of the internal combustion engine is connected to one valve by a connecting portion, and it can also be connected to two or more valves of the same type in the same cylinder through a connecting rod or other means.

[0042] The valve mechanism of the internal combustion engine of the present invention realizes light load operation during operation, so the material can be 40Cr, surface quenched to 56-60HRC, or 38CrMoAl, nitrided to 60-67HRC. In this embodiment, materials such as 20Cr, 20CrMn, etc., which are surface quenched to a hardness of 55-60HRC, should also be suitable.

[0043] The above embodiment is characterized in that the shift fork on the transmission shaft rotates, and the relative movement between the shift fork and the groove on the connecting part drives the connecting part to move up and down to drive the valve to open and close. Its structural characteristics are that the structure of the transmission shaft is relatively simple and easy to process and manufacture, and the entire valve mechanism is compact. The disadvantage is that the mass of the connecting part is slightly large and the motion inertia is relatively large. Of course, the implementation method can also adopt other layout arrangements, such as Figure 5 , Figure 6 As shown: there are grooves on both sides of the lower part of the connection part that match the axial cylindrical protrusions on the fork. This layout is beneficial to reducing the mass of the connection part and can reduce the moment of inertia.

[0044] The structural form of the valve train of the internal combustion engine described in the above embodiment and the following description is that each unit adopts a double fork structure, the purpose is to make the operation of the entire mechanism more stable. In fact, each unit can also adopt a single fork structure, which is simpler! But the stability is not as good as the double fork structure. In addition, another feature of this embodiment is that the top of the connecting part cooperates and interacts with the magnet to achieve sealing after the valve is closed.

[0045] The internal combustion engine valve mechanism of the present invention belongs to the category of cam mechanism and is a variant of cam mechanism. In addition, the method of maintaining high-pair contact in the existing internal combustion engine valve mechanism (valve opening and closing) is achieved by force locking, and the force for opening and closing the valve comes from the cam and the valve spring. The method of maintaining high-pair contact in the internal combustion engine valve mechanism of the present invention (valve opening and closing) is achieved by form locking, and the force on the valve comes from the shift fork; when the valve of the existing internal combustion engine valve mechanism is in a closed state, the sealing of the valve is affected by the pre-tensioning force of the valve spring, while the present invention realizes the sealing after the valve is closed by cooperating and interacting with the magnet at the top of the connecting part.

[0046] Regarding the selection of the motion law of the follower in the valve mechanism of an internal combustion engine, the motion law of the valve in the existing valve mechanism of an internal combustion engine generally adopts the fifth-order polynomial motion law (the profile of the cam determines the valve motion law), and the characteristic of the fifth-order polynomial motion law is that it is "suitable for high speed and medium load". The valve mechanism of the internal combustion engine of the present invention does not have a valve spring directly acting on the valve, thereby realizing light load operation. The valve motion law can select the "sinusoidal acceleration motion law", and the characteristic of the sinusoidal acceleration motion law is that it is "suitable for high speed and light load". By changing the valve motion law, the cam profile is improved, thereby improving the ventilation efficiency of the internal combustion engine.

[0047] The extrapolated profile equation is:

[0048] Use the inversion method to establish a coordinate system and find the coordinates of the high-pair contact point; as shown in Figure 7:

[0049] Base circle radius r b ; offset distance e; B0 is the starting point of the push stroke; B is the arbitrary contact point of the high pair (roller center); O is the rotation center; S is the displacement of the follower; the roller radius is r r ; tanθ is the slope of the normal line at point B; h is the stroke.

[0050] BB'=SA'B'=S0A'B=S0-S

[0051]

[0052]

[0053] The coordinates of point B are the coordinates of the roller center:

[0054] The actual profile equation of the groove wall is:

[0055]

[0056]

[0057] Pressure angle: As shown in Figure 8:

[0058] lop=V / ω(point p is the relative instantaneous center) tanα=(e+lop) / (S0-S)

[0059] Because: S0 2 +e 2 =r b 2 So: tanα=(e+lop) / [(r b 2 -e 2 ) 1 / 2 -S]

[0060] Base circle radius;

[0061]

[0062] α<[α](allowable pressure angle)pressure angle range(25°-35°)

[0063]

[0064] S needs to satisfy the law of sinusoidal acceleration motion;

[0065] Right now:

[0066]

[0067]

[0068] Or S satisfies the law of motion of a quintic polynomial;

[0069] Right now:

[0070]

[0071]

[0072] A buffer section needs to be set at the connection between the near rest and the push stroke, and the connection between the return stroke and the near rest. A smooth transition needs to be ensured at the connection between the push stroke and the return stroke. The Camtra plug-in in the SolidWorks software is used to generate the cam.

Claims

1. A valve train for an internal combustion engine comprising a timing gear, a valve, a valve guide, and a valve seat, characterized in that: It also includes a transmission shaft with a shift fork distributed on the shaft body and corresponding to the valve in a specific phase, a bracket, a magnet fixed on the bracket, and a connecting part connected to the valve; the shift fork is a support arm extending from the inside to the outside of the transmission shaft, and the end of the support arm has an axial protrusion; the bracket is fixed on the cylinder head and is located above the connecting part; one end of the connecting part has a horizontal protrusion, and the other end is connected to at least one of the valves, the middle axial projection of the connecting part is an irregular sector, and its central angle is η, the η opening faces the valve, a groove is opened on the disk surface, and the radial projection of the transmission shaft axis intersects perpendicularly with the radial projection of the center line of the bracket, the connecting part, and the valve; when the transmission shaft rotates, the axial protrusion at the end of the support arm moves relatively in the groove in some phases, and the fit is a clearance fit, and in other phases the magnet cooperates and interacts with the horizontal protrusion at one end of the connecting part, and the fit is a clearance fit.

2. The valve train of an internal combustion engine according to claim 1, characterized in that: 115°≤η≤145°.

3. The valve train of an internal combustion engine according to claim 1, characterized in that: The theoretical profile of the groove is a smooth curve.

4. The valve train of an internal combustion engine according to claim 1, characterized in that: The magnet may be a permanent magnet or an electromagnet.

Images