Piston pressure limiting method for eliminating piston engine knock and piston thereof

Abstract

The purpose of the piston pressure limiting method for eliminating piston engine knock and the piston with pressure relief function used therein is to provide a piston pressure limiting method for eliminating piston engine knock and the piston with pressure relief function used therein, which can limit the maximum combustion pressure in the cylinder of the piston engine, prevent the pressure in the engine cylinder from exceeding the set safety value, eliminate the knock that may be generated after the compression ratio of the piston engine is increased, and significantly improve the thermal efficiency of the piston engine. In order to achieve the above-mentioned purpose, the present invention is implemented through the following technical scheme: the piston pressure limiting method for eliminating piston engine knock: installing a piston with a pressure relief function in the combustion chamber of the cylinder of the engine, setting the safety pressure value of the combustion chamber of the cylinder to P1, and setting the pressure value P in the combustion chamber to be less than the safety pressure value P1, the pressure relief function of the piston is not started; setting the pressure value P in the combustion chamber to be greater than or equal to the safety pressure value P1, the pressure relief function of the piston is turned on, and the combustion chamber is relieved to the outside through the piston until the pressure value P in the combustion chamber drops below the safety pressure value P1, and the pressure relief function of the piston is turned off.

Description

Technical Field

[0001] The invention relates to a piston engine, in particular to a piston pressure limiting method for eliminating the knock of a piston engine and a piston thereof. Background Art

[0002] A reciprocating piston engine is a piston engine in which the piston makes reciprocating linear motion in the cylinder and converts the linear motion of the piston into the rotational motion of the crankshaft through the crank-connecting rod power transmission mechanism. The main function of the piston is to withstand the combustion pressure in the cylinder and ensure the reliable sealing of the engine working fluid. Reciprocating piston engines are usually gasoline engines and diesel engines. Gasoline has poor anti-knock performance, and the mixture is prone to deflagration and causes the engine body to detonate, so the ignition method is generally used. At present, the compression ratio of the known gasoline engine is generally between 9 and 12, and the maximum can reach 14. The normal working maximum combustion pressure is about 5MPa; diesel has a low auto-ignition point and better anti-knock performance than gasoline, so diesel engines all use compression ignition. The compression ratio of the known diesel engine is currently generally between 12 and 22, and the maximum can reach 25. Due to different design speeds and different uses, the normal working maximum combustion pressure is 7 to 23MPa: diesel engine detonation is generally called rough work, which can be caused by changes in compression ratio, premature fuel supply, excessive fuel supply, overload operation, etc.

[0003] From the history of engine technology development, the engine has evolved from a gas engine with a compression ratio of zero to a gradually improved compression ratio through continuous evolution, and the engine thermal efficiency has increased to today's gasoline engine thermal efficiency of 30%-40%, and the diesel engine thermal efficiency is generally around 40%-50%. On the other hand, engine emissions will cause environmental pollution, and the main harmful substances emitted are: sulfur oxides (mainly sulfur dioxide SO2), carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC), particulate matter (PM), odor (mainly various incomplete combustion products, such as various aldehydes), carbon dioxide (CO2), etc., as well as noise pollution.

[0004] The development of engines is a process of constantly pursuing improved thermal efficiency. The main means is to increase the compression ratio, but this has brought about an increase in emission pollution and harmful nitrogen oxide (NOx) pollutants. What is more serious is that a larger compression ratio will lead to more intense combustion and produce high temperature and high pressure, which is prone to deflagration and even detonation, resulting in cylinder explosion and damage to the engine.

[0005] A car cylinder explosion will seriously damage the engine and make it scrapped. The explosion of a car while it is in motion is even more harmful, and can cause a fire in the car, traffic accidents, and other hazards to people. Marine diesel engines or diesel engines in power plants, especially large two-stroke diesel engines, have relatively stable load output, relatively high compression ratios, high engine enhancement, and the highest thermal efficiency among piston engines. In the past, cylinder explosion damage and harm to operators have also occurred.

[0006] When designing the geometric compression ratio of automotive engines, especially automotive gasoline engines, it is generally considered that the engine will not explode when the load is large and have a high thermal efficiency. When the vehicle is running normally and the load power is not large, the engine intake volume is small, and the actual compression ratio is less than the geometric compression ratio, so the engine thermal efficiency is lower than the design value.

[0007] As can be seen from the above, the usual technical solution to solve the knock problem is to use a variable compression ratio so that the engine has a higher compression ratio under low-load conditions, and can adjust the compression ratio to control the excessive in-cylinder gas pressure under high-load conditions, thereby preventing knock and improving thermal efficiency. However, the variable compression ratio is based on the compression ratio control of the engine operating conditions, and cannot eliminate the deflagration phenomenon caused by the sudden increase in cylinder pressure under low load conditions; it is more likely to further reduce the cylinder pressure of the low-pressure cycle under high-load conditions, resulting in a decrease in power and economy. There are many solutions for variable compression ratio technology, but they usually require the use of complex electronic control technology and complex mechanical or hydraulic devices, which are difficult to manufacture and have high production costs. Moreover, since its compression ratio changes slowly, it cannot respond promptly to changes in the engine cycle conditions of automobiles and other engines, and cannot prevent the cylinder pressure from rising instantly. Therefore, in order to avoid the occurrence of knock, technicians in this field set the working pressure of the internal combustion engine more conservatively. Taking the gasoline engine used in family cars as an example, the normal working pressure of the engine is usually set to about 60% of the pressure when knock begins to occur. This can effectively prevent the engine from experiencing an instantaneous rise in cylinder pressure and causing knock under the influence of factors such as vehicle load changes, fuel quality, and intake temperature and pressure. This obviously limits the improvement of the compression ratio of existing engines, making it difficult to further improve the thermal efficiency of existing engines. Summary of the invention

[0008] The purpose of the present invention is to provide a piston pressure limiting method and a piston for eliminating piston engine knock, which can limit the maximum combustion pressure in the cylinder of the piston engine, prevent the pressure in the engine cylinder from exceeding a set safety value, eliminate the knock that may be generated after the compression ratio of the piston engine is increased, and significantly improve the thermal efficiency of the piston engine.

[0009] In order to achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions: a piston pressure limiting method for eliminating piston engine knock: a piston with a pressure relief function is installed in the combustion chamber of the engine cylinder, and a safety pressure value P1 is set in the combustion chamber of the cylinder. When the pressure value P in the combustion chamber is set to be less than the safety pressure value P1, the pressure relief function of the piston is not started; whenever the pressure value P in the combustion chamber is greater than or equal to the safety pressure value P1, the pressure relief function of the piston is turned on, and the combustion chamber is relieved to the outside through the piston until the pressure value P in the combustion chamber drops below the safety pressure value P1, and the pressure relief function of the piston is turned off.

[0010] When the piston engine is a gasoline engine, the safety pressure value P1 is 67%-99% of the critical pressure value P0 at which knocking begins to occur in the combustion chamber.

[0011] When the piston engine is a diesel engine, the safety pressure value P1 is set to the maximum pressure value P when a conventional diesel engine with the same displacement and the same fuel is working normally. Z 1.0-1.3 times of.

[0012] The piston with pressure relief function used in the piston pressure limiting method for eliminating piston engine knock comprises a piston body, a pressure relief hole is provided on the piston body, and the two ends of the pressure relief hole are respectively connected to the top end surface and the bottom end surface of the piston body, and the opening and closing actuator of the safety valve is installed in the pressure relief hole. When the pressure at the top end of the piston body is less than the opening pressure of the safety valve, the safety valve is closed and the pressure relief hole is not connected; when the pressure at the top end of the piston body is greater than the opening pressure of the safety valve, the safety valve is opened, so that the top end and the bottom end of the piston body are connected to each other through the pressure relief hole. The pressure relief hole is located at the center of the top end of the piston body. An annular step is provided on the inner peripheral wall of the pressure relief hole, and a safety valve core is provided in the pressure relief hole. An elastic support is provided between the safety valve core and the piston body. The safety valve core can be closely matched with the annular step under the elastic force of the elastic support to close the pressure relief hole. When the pressure at the top end of the piston body is greater than the opening pressure value P1 of the safety valve, the safety valve core can overcome the elastic force of the elastic support, leave the annular step, and make the pressure relief hole conductive. The piston body is provided with a through hole, a safety valve body is installed in the through hole, the safety valve body passes through the through hole, the pressure relief hole is provided on the safety valve body, an annular limit platform is provided at the upper edge of the safety valve body, a nut is provided below the piston body, a vent hole is provided on the nut, and the nut is threadedly matched with the safety valve body. The elastic support member is a coil spring. The elastic support member is a diaphragm spring.

[0013] The method or piston provided by the present invention can limit the pressure in the cylinder of the piston engine, prevent the pressure in the cylinder of the engine from exceeding the set safety value, and can make the pressure in the cylinder of the engine close to the knock pressure, so that the pressure of knocking is not generated during the operation of the engine. While improving the compression ratio, it can also limit the excessively high cylinder pressure of the sudden change working condition, which can not only improve the fuel economy of the low-load working condition, but also comprehensively improve the fuel economy of various load working conditions. The thermal efficiency of the engine is greatly improved and the emission is improved. The present invention can improve the combustion cycle fluctuation of the engine and the combustion unevenness of each cylinder, which is conducive to improving the cold start and idle working condition performance of the engine and improving the low-load performance of the engine. The present invention can miniaturize the engine and reduce the combustion vibration of the engine. The fast dynamic response of the pressure-limiting piston to the combustion pressure is particularly suitable for automobile engines, and is also suitable for engineering machinery engines and diesel generator sets with frequent working condition changes. When applied to the transformation of traditional automobile engines, it only needs to replace the ordinary piston with a pressure-limiting piston, which can save more than 10% of fuel in an integrated manner. The present invention has a simple structure and low cost, and production does not require investment in new production lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the piston with pressure relief function of the present invention;

[0015] Figure 2 It is one of the combustion chamber pressure diagram and piston pressure relief operation timing diagram of the present invention;

[0016] Figure 3 This is the second combustion chamber pressure diagram and piston pressure relief operation timing diagram of the present invention;

[0017] Figure 4a yes Figure 1 One of the schematic diagrams of the piston and safety valve with pressure relief function is shown, in which the piston is at the top dead center;

[0018] Figure 4b yes Figure 1 The second schematic diagram of the piston and safety valve with pressure relief function is shown in the figure, which shows the state of the safety valve opening during the downward movement of the piston;

[0019] Figure 4c yes Figure 1 The third schematic diagram of the piston and safety valve with pressure relief function is shown in which the safety valve is closed during the piston continues to move downward;

[0020] Figure 4d yes Figure 1 The fourth schematic diagram of the piston and safety valve with pressure relief function is shown in the figure, which shows the state where the piston reaches the bottom dead point. DETAILED DESCRIPTION

[0021] The piston pressure limiting method for eliminating piston engine knock is as follows: a piston with a pressure relief function is installed in the combustion chamber of the engine cylinder, a safety pressure value in the cylinder combustion chamber is set to P1, and when the pressure value P in the combustion chamber is set to be less than the safety pressure value P1, the pressure relief function of the piston is not started; whenever the pressure value P in the combustion chamber is greater than or equal to the safety pressure value P1, the pressure relief function of the piston is turned on, and the combustion chamber releases pressure to the outside through the piston until the pressure value P in the combustion chamber drops below the safety pressure value P1, and then the pressure relief function of the piston is turned off.

[0022] The safety pressure value P1 described in the present invention is the maximum working pressure in the combustion chamber of the cylinder when the engine is working. When the pressure value P in the combustion chamber reaches the set safety pressure value P1, the combustion chamber is connected to the outside, and the overpressure exhaust gas that has been burned in the combustion chamber begins to be discharged into the crankcase below the piston body, preventing the pressure in the combustion chamber from continuing to increase. When the combustion chamber is rapidly depressurized, the pressure value P in the combustion chamber remains near the safety pressure value P1 and will not increase significantly. As the piston moves downward, when the pressure value P in the combustion chamber is lower than the safety pressure value P1, the pressure relief function of the piston is restored to the closed state, and the combustion chamber stops depressurizing. The piston engine pressure limiting method described in the present invention can limit a maximum safety pressure value in the combustion chamber of the engine cylinder. When the cylinder pressure of the engine rises instantly due to factors such as vehicle load changes, fuel quality, and intake temperature and pressure, the pressure exceeding the safety pressure value can be automatically discharged, which can prevent the pressure in the combustion chamber of the engine cylinder from exceeding the safety setting value, so that the normal working pressure set by the engine can be increased as much as possible, without considering the problem of detonation caused by the instantaneous increase in pressure or the problem that the cylinder strength is difficult to bear, and greatly improves the compression ratio and thermal efficiency of the engine. The present invention can set the working pressure of the engine to be higher than the normal pressure of similar known engines, avoid the occurrence of knocking, and can increase the compression ratio of the pressure-limited piston engine compared with the known engines, thereby improving the thermal efficiency of the engine.

[0023] It is generally recognized by those skilled in the art that the engine piston and its components together with the cylinder ensure reliable sealing of the engine working fluid, otherwise the piston engine cannot operate normally. The present invention adopts a technical solution of breaking the seal of the piston and its components when the combustion pressure in the combustion chamber exceeds the set pressure, and releasing the pressure through the safety valve, thereby preventing detonation while enabling the engine to operate reliably with higher thermal efficiency, producing unexpected technical effects.

[0024] The present invention can improve the compression ratio while limiting the excessively high cylinder pressure under sudden operating conditions, which can not only improve the fuel economy under low-load conditions, but also comprehensively improve the fuel economy under various load conditions. The thermal efficiency of the engine can be greatly improved and emissions can be improved. The present invention can improve the combustion cycle fluctuations of the engine and the combustion unevenness of each cylinder, which is beneficial to improving the cold start and idle performance of the engine and improving the low-load performance of the engine. The present invention can miniaturize the engine and reduce the combustion vibration of the engine. The rapid dynamic response of the pressure-limiting piston to the combustion pressure is particularly suitable for automobile engines, and is also suitable for engineering machinery engines and diesel generator sets with frequent changes in operating conditions. When applied to the modification of traditional automobile engines, it only needs to replace the ordinary piston with a pressure-limiting piston, which can save more than 10% of fuel in an integrated manner. The present invention has a simple structure and low cost, and production does not require investment in new production lines.

[0025] Figure 2 It is one of the combustion chamber pressure diagrams and piston pressure relief working timing diagrams. The safety pressure value P1 in the figure is greater than the normal pressure value Pz of a conventional known engine with the same displacement and the same fuel, and is close to and less than the knock pressure value P0. Curve AZB is the normal operating pressure curve of a known engine, and the pressure at the highest point Z is the normal working pressure. Curve A-Z'-B is the working pressure curve when a knock occurs in a known engine, and the highest pressure point is Z'. After the pressure-limiting piston is installed in the state of curve A-Z'-B, the operating pressure curve of the pressure-limiting piston engine becomes the ASVB curve.

[0026] When the knock curve A-Z'-B appears due to a sudden increase in the working pressure of the combustion chamber 5 of the engine for some reason, the piston starts the pressure relief function at point S, and the pressure energy in the combustion chamber is quickly released. The pressure value P in the combustion chamber is maintained at the safe pressure value P1 from point S to point V. After point V, the pressure value P in the combustion chamber drops and is lower than the set pressure value P1, and the pressure relief function of the piston is closed. When the pressure in the combustion chamber continues to drop to point B, the engine exhaust valve opens.

[0027] Figure 3 This is the second diagram of the combustion chamber pressure diagram and the piston pressure relief working sequence diagram. Figure 2 The engine works in the non-detonation curve A-Z''-B state. After installing the piston with pressure relief function, the working pressure curve A-Z''-B is the same as the non-detonation curve. The highest pressure point Z'' does not exceed the set pressure. The maximum combustion working pressure is Figure 2 The pressure point Z' is low, but higher than the highest pressure point Z of the known engine in normal operation. The valve operation timing diagram shows that the pressure relief function of the piston is in the closed state during the entire power stroke.

[0028] Figure 4a-4d1 is a schematic diagram of the state of the piston with pressure relief function in the engine power stroke. When the engine is in the power stroke, the safety valve 100 is actuated from the piston top dead center TDC to the bottom dead center BDC, showing the state of the safety valve 100 at four different piston positions. Figure 2 To elaborate in depth, Figure 4a When it is the top dead center, the oil and gas in the combustion chamber have been ignited, and the combustion pressure has not yet risen to the set pressure, and the safety valve 100 is in a closed state; Figure 4b As the piston continues to move downward, the oil and gas in the combustion chamber continue to burn. When the pressure in the combustion chamber rises to point S on the pressure curve, the pressure in the combustion chamber is equal to the set pressure, and the safety valve 100 opens. After combustion, the exhaust gas exceeding the set pressure is discharged into the crankcase through the safety valve 100. The gas flow direction is as follows: Figure 4b As indicated by the arrow; Figure 4c When the piston continues to move downward and the combustion chamber pressure is maintained at the set pressure to point V, the combustion chamber pressure is less than the set pressure, and the safety valve 100 is closed; Figure 4d It is the bottom dead center, the exhaust valve on the cylinder head has been opened to exhaust, and the safety valve 100 is in the closed state.

[0029] Depend on Figure 1 to Figure 4d It can be seen from the content shown that after adopting the pressure limiting method of the present invention, the engine setting pressure can be higher than the normal pressure of the known engine, the compression ratio of the pressure limiting piston engine can be improved, and the thermal efficiency of the engine is improved.

[0030] When the pressure value P in the combustion chamber increases and exceeds the safety pressure value P1, the pressure relief function of the piston starts to work. Although a small part of the gas energy exceeding the safety pressure is lost, the piston pressure curve ASVB is still higher than the pressure curve AZB, and the thermal efficiency is also improved. This is because the known crankshaft connecting rod power transmission mechanism converts the piston force at the top dead center into an output torque equal to zero, and the conversion efficiency gradually increases after the piston leaves the top dead center. A small part of the gas energy lost by the pressure-limiting piston is located near the top dead center. It has no effect on the position with high conversion efficiency far away from the top dead center.

[0031] Since the pressure relief function is directly set on the piston, close to the combustion chamber, it is sensitive to the combustion pressure and only acts according to the working pressure of the combustion chamber, ensuring that the piston engine does not have occasional knocking that causes damage. In addition, the maximum combustion pressure can be well controlled not to exceed the safety pressure in each combustion cycle, solving the problem of cyclic cylinder pressure fluctuation and cylinder pressure unevenness of different cylinders of multi-cylinder engines. The cylinder pressure control method based on each cycle is also conducive to increasing the upper limit of the compression ratio.

[0032] The piston engine increases the compression ratio, which increases the initial combustion temperature of the combustion chamber, which can increase the combustion limit of lean combustible gas. The rapid opening of the pressure relief function reduces the maximum combustion temperature, making the combustion more efficient and gentle, reducing the heat load at the top dead point, and reducing the heat dissipation of the cylinder head.

[0033] The compression ratio of traditional spark ignition gasoline engines is generally low. At the same time, because the throttle is used to control the intake volume to control the output load, the intake volume at low load is less than that at high load, and the actual compression ratio at low load is smaller. The use of a pressure-limiting piston in a gasoline engine can significantly increase the compression ratio, increase the set pressure to close to the knock pressure, and Figure 3 The thermal efficiency of gasoline engines for automobiles with large workload changes has been significantly improved.

[0034] The pressure relief function of the piston can be achieved through a variety of conventional pressure relief valve structures. The structure is extremely simple and it is very easy to modify existing engines. While eliminating detonation, it also eliminates the "cylinder explosion" failure with greater economic losses and safety hazards. The thermal efficiency is more than 10% higher than that of known piston engines.

[0035] When used in a gasoline engine, the safety pressure value P1 of the present invention can be set to 67%-99% of the critical pressure value P0 at which knocking begins in the combustion chamber. The critical pressure value P0 at which knocking begins in the combustion chamber of the engine is determined by factors such as the fuel grade and cylinder diameter used by the engine, and can be measured by existing detection tools. When setting the safety pressure value P1 of a gasoline engine, according to the actual value of the critical pressure value P0 at which knocking occurs measured by the engine of this specification, the closer the safety pressure value P1 is to the critical pressure value P0 of knocking, the longer the engine works in a high compression ratio condition when it is working, which is more conducive to improving the thermal efficiency of the engine. If the safety pressure value P1 of the gasoline engine is set to 67% lower than the critical pressure value P0 at which knocking occurs, the difference between its thermal efficiency and that of the traditional gasoline engine when it is working is not significant, and the effect of improving the thermal efficiency is limited. If the safety pressure value P1 of the gasoline engine is set to the same as or higher than the critical pressure value P0 of knocking, knocking will frequently occur when the engine is working, which should be avoided. In actual production, the safety pressure value P1 can be set within the highest possible range so as to significantly improve the thermal efficiency of the gasoline engine. For example, the safety pressure value P1 of the gasoline engine can be set within the range of 70%-99.99% of the critical pressure value P0 for knocking. In addition, considering the accuracy of the setting of the safety pressure value P1 during the production of the engine piston and the complex working conditions that the engine may encounter during operation, the safety pressure value P1 can be set with an appropriate safety range between the critical pressure value P0 for knocking. For example, the safety pressure value P1 of the gasoline engine can be set within the range of 70%-99% of the critical pressure value P0 for knocking. For engines with frequently changing working conditions such as automotive gasoline engines, the safety range between the safety pressure value P1 and the critical pressure value P0 for knocking can also be appropriately expanded. For example, the safety pressure value P1 of the gasoline engine can be set within the range of 70%-98% of the critical pressure value P0 for knocking.

[0036] The compression ratio of a conventional compression ignition diesel engine is already high. After the intake supercharging is adopted, the heat load is greater and the mechanical strength requirement is higher. In this case, the piston pressure limiting method of the present invention is used to appropriately increase the compression ratio. For example, the set safety pressure value P1 is set to the maximum pressure value P when the conventional diesel engine with the same displacement and the same fuel is working normally. Z It is 1.0-1.3 times of that of traditional diesel engines, and prolongs the time they work in high compression ratio conditions within the range that the mechanical strength of traditional diesel engines can withstand, which not only ensures the cold start performance of compression ignition, but also reduces the maximum explosion pressure and increases the average effective pressure of the engine.

[0037] The piston with pressure relief function used in the piston pressure limiting method for eliminating piston engine knock in the present invention comprises a piston body 2, a pressure relief hole 7 is provided on the piston body 2, and the two ends of the pressure relief hole 7 are respectively connected to the top end surface and the bottom end surface of the piston body 2, and the opening and closing actuator of the safety valve 100 is installed in the pressure relief hole 7. The opening pressure of the safety valve 100 is set to P1. When the pressure at the top end of the piston body 2 is less than P1, the safety valve 100 is closed and the pressure relief hole 7 is not connected; when the pressure at the top end of the piston body 2 is greater than P1, the safety valve 100 is opened, so that the top end and the bottom end of the piston body 2 are connected to each other through the pressure relief hole 7. The safety valve 100 is installed on the piston body 2, close to the combustion chamber, and is sensitive to the combustion pressure. It only acts according to the working pressure of the combustion chamber 5 to ensure that the engine does not have occasional knocks that cause damage.

[0038] The pressure relief hole 7 of the present invention is preferably arranged at the center of the top of the piston body 2. The existing engine fuel injection ignition device 6 is arranged at the center of the cylinder. This structure can ensure that the ignition point of the combustible gas is close to the safety valve 100. When the safety valve 100 is activated, the pressure relief hole 7 discharges the burned exhaust gas, thereby not affecting the complete combustion of the unburned gas in the combustion chamber 5.

[0039] The safety valve 100 of the present invention can adopt various existing structures as the opening and closing actuator, such as a spring-type safety valve, a lever-type safety valve, etc., wherein the preferred structure is: an annular step 11 is provided on the inner peripheral wall of the pressure relief hole 7, a safety valve core 8 is provided in the pressure relief hole 7, an elastic support member 10 is provided between the safety valve core 8 and the piston body 2, and the safety valve core 8 can be closely matched with the annular step 11 under the elastic force of the elastic support member 10 to close the pressure relief hole 7. When the pressure at the top of the piston body 2 is greater than the opening pressure value P1 of the safety valve 100, the safety valve core 8 can overcome the elastic force of the elastic support member 10, leave the annular step 11, and make the pressure relief hole 7 conductive. The safety valve core 8 of this structure directly faces the combustion chamber, and the pressure in the combustion chamber can directly act on the safety valve core 8. When the pressure in the combustion chamber increases, the safety valve core 8 can open the pressure relief function with a slight movement, and the pressure relief hole 7 can be quickly closed when the pressure in the combustion chamber is lower than the safety pressure. It reacts sensitively and directly to the combustion pressure, and has better response speed and reliability.

[0040] In order to reduce the difficulty of manufacturing, maintenance and servicing, the piston of the present invention can be provided with a through hole 12 on the piston body 2, and a safety valve body 3 is installed in the through hole 12. The safety valve body 3 passes through the through hole 12. The pressure relief hole 7 is provided on the safety valve body 3. An annular limit platform is provided at the upper edge of the safety valve body 3 to limit the safety valve body 3 and enhance the sealing performance between the safety valve body 3 and the through hole 12. A nut 9 is provided below the piston body 2, and a vent hole is provided on the nut 9. The nut 9 is threadedly matched with the safety valve body 3, and the elastic support member 10 is in contact with the nut 9. The structure installs the safety valve 100 on the piston body 2 in the form of assembly, which has a simple structure, convenient production, assembly and maintenance, reduces the difficulty of manufacturing the piston body 2 itself, and reduces the processing and assembly costs. When the safety valve 100 is maintained and serviced, the safety valve 100 can be removed from the piston body 2 alone, without replacing the entire piston, and the maintenance cost is also significantly reduced.

[0041] The elastic support member of the present invention can be a variety of elastic components such as a coil spring and a diaphragm spring, which can be flexibly selected according to factors such as the internal space of the pressure relief hole 7 and the shape of the safety valve core 31. When a diaphragm spring is used, it is generally necessary to open an air guide hole on the diaphragm spring. The elastic support members such as the coil spring and the diaphragm spring can be fixed by a nut 9.

[0042] In the figure, 1 is a cylinder, 5 is a combustion chamber, and 6 is a fuel injection ignition device.

Claims

1. A piston pressure limiting method for eliminating piston engine knock, characterized in that: A piston with a pressure relief function is installed in the combustion chamber of the engine cylinder, and the safety pressure value in the cylinder combustion chamber is set to P1. When the pressure value P in the combustion chamber is set to be less than the safety pressure value P1, the pressure relief function of the piston is not started; it is set that whenever the pressure value P in the combustion chamber is greater than or equal to the safety pressure value P1, the pressure relief function of the piston is turned on, and the combustion chamber releases pressure to the outside through the piston until the pressure value P in the combustion chamber drops below the safety pressure value P1, and the pressure relief function of the piston is turned off.

2. The piston pressure limiting method for eliminating piston engine knock according to claim 1, characterized in that: When the piston engine is a gasoline engine, the safety pressure value P1 is 67%-99% of the critical pressure value P0 at which knocking begins to occur in the combustion chamber.

3. The piston pressure limiting method for eliminating piston engine knock according to claim 1, characterized in that: When the piston engine is a diesel engine, the safety pressure value P1 is set to the maximum pressure value P when a conventional diesel engine with the same displacement and the same fuel is working normally. Z 1.0-1.3 times of.

4. The piston with pressure relief function used in the piston pressure limiting method for eliminating piston engine knock as claimed in claim 1, 2 or 3, characterized in that: The invention comprises a piston body (2), wherein a pressure relief hole (7) is provided on the piston body (2), wherein two ends of the pressure relief hole (7) are respectively connected to the top end surface and the bottom end surface of the piston body (2), and an opening and closing actuator of a safety valve (100) is installed in the pressure relief hole (7). When the pressure at the top end of the piston body (2) is less than the opening pressure of the safety valve (100), the safety valve (100) is closed and the pressure relief hole (7) is not connected; when the pressure at the top end of the piston body (2) is greater than the opening pressure of the safety valve (100), the safety valve (100) is opened, so that the top end and the bottom end of the piston body (2) are connected to each other through the pressure relief hole (7).

5. The piston with pressure relief function according to claim 4, characterized in that: The pressure relief hole (7) is located at the center of the top end of the piston body (2).

6. The piston with pressure relief function according to claim 4, characterized in that: An annular step (11) is arranged on the inner peripheral wall of the pressure relief hole (7), a safety valve core (8) is arranged in the pressure relief hole (7), and an elastic support member (10) is arranged between the safety valve core (8) and the piston body (2). Under the elastic force of the elastic support member (10), the safety valve core (8) can closely cooperate with the annular step (11) to close the pressure relief hole (7); when the pressure at the top end of the piston body (2) is greater than the opening pressure value P1 of the safety valve (100), the safety valve core (8) can overcome the elastic force of the elastic support member (10) and leave the annular step (11), so that the pressure relief hole (7) is open.

7. The piston with pressure relief function according to claim 4, characterized in that: The piston body (2) is provided with a through hole (12), a safety valve body (3) is installed in the through hole (12), the safety valve body (3) passes through the through hole (12), the pressure relief hole (7) is provided on the safety valve body (3), an annular limit platform is provided on the upper edge of the safety valve body (3), a nut (9) is provided below the piston body (2), a vent hole is provided on the nut (9), and the nut (9) is threadably matched with the safety valve body (3).

8. The piston with pressure relief function according to claim 6, characterized in that: The elastic supporting member is a coil spring.

9. The piston with pressure relief function according to claim 6, characterized in that: The elastic supporting member is a diaphragm spring.

Images