Engine piston, engine and engine control method

Abstract

The present invention belongs to the technical field of engines, and discloses an engine piston, an engine and an engine control method. The engine piston comprises a piston body, a center boss and a first annular boss are provided on the top of the piston body, a lower combustion pit is formed between the center boss and the first annular boss, an upper combustion pit is formed on the outer peripheral side of the first annular boss on the piston body; a second annular boss is provided on the side wall of the center boss. Along the axial direction of the piston body, the distance between the highest point of the first annular boss and the lowest point of the lower combustion pit is the first distance h1; the distance between the first contour line and the lowest point of the lower combustion pit is the first distance h1; the distance between the convex point of the second annular boss and the lowest point of the lower combustion pit is the second distance h2; h2<h1. When the engine is running at low load, the loading capacity of the engine can be effectively improved; when the engine is running at high load, the phenomenon of engine performance deterioration can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engines, and in particular to an engine piston, an engine and an engine control method. Background Art

[0002] The diesel generator set is mainly composed of a diesel engine and a generator. The diesel engine is connected to the generator through a transmission system. The diesel engine converts the heat energy generated by the combustion of diesel into mechanical energy to drive the generator, and the generator converts the mechanical energy into electrical energy. A turbocharger is integrated on the diesel engine, and the exhaust gas of the diesel engine is passed into the turbocharger to drive the turbocharger to operate, so that the turbocharger presses air into the cylinder of the diesel engine.

[0003] Among them, during transient sudden acceleration, diesel can be instantly sprayed into the cylinder, but the turbocharger has a lag, especially when the diesel engine is started and under low-load operation, the intake air volume will lag behind the intake fuel volume significantly, affecting the improvement of the diesel engine's transient capability. Therefore, how to improve the air utilization rate and the mixed combustion effect under limited air conditions to improve the work capacity is one of the keys to improving the diesel engine's transient capability.

[0004] At present, the prior art usually adjusts the structural characteristics of the combustion chamber of the diesel engine and / or the specific injection method to achieve the purpose of improving the air utilization rate and the mixed combustion effect. However, the air utilization rate and mixed combustion effect of the diesel engine when the engine is running at low load need to be further improved; secondly, the diesel engine has a small amount of fuel injection under low load conditions and a large amount of fuel injection under high load conditions. Optimizing the air utilization rate and mixed combustion effect of the diesel engine under low load conditions often causes the performance of the diesel engine to deteriorate under high load conditions. Summary of the invention

[0005] The object of the present invention is to provide an engine piston, an engine and an engine control method to solve the above problems existing in the prior art.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] An engine piston comprises a piston body, wherein a center boss and a first annular boss are provided on the top of the piston body; a lower combustion pit is formed between the center boss and the first annular boss; an upper combustion pit is formed on the outer peripheral side of the first annular boss on the piston body;

[0008] A second annular protrusion is convexly provided on the side wall of the central protrusion;

[0009] Along the axial direction of the piston body, the distance between the highest point of the first annular protrusion and the lowest point of the lower combustion pit is the first distance h1; the distance between the first contour line and the lowest point of the lower combustion pit is the first distance h1, and the first contour line is the connecting contour line of the second annular protrusion and the center boss, which is away from the lowest point of the lower combustion pit; the distance between the protrusion vertex of the second annular protrusion and the lowest point of the lower combustion pit is the second distance h2; h2

[0010] As a preferred embodiment of the above-mentioned engine piston, when the piston body is located at the top dead center, a combustion chamber is formed between the engine cylinder head and the top of the piston body; along the axial direction of the piston body, the distance between the top of the combustion chamber and the lowest point of the lower combustion pit is the combustion chamber height h; h1=(0.43~0.5)h.

[0011] As a preferred solution of the above engine piston, the diameter of the piston body is D;

[0012] The diameter of the first contour line D1=(0.2-0.25)D;

[0013] The diameter D2 of the second contour line is (0.3-0.35)D, and the second contour line is a connecting contour line of the connecting contour lines of the second annular protrusion and the central boss close to the lowest point of the lower combustion pit.

[0014] As a preferred solution of the above engine piston, the diameter of the piston body is D;

[0015] Along the radial direction of the piston body, the diameter D3 corresponding to the farthest end of the lower combustion pit away from the central axis of the piston body is (0.45-0.6)D.

[0016] As a preferred solution of the above engine piston, a groove is provided on the top of the piston body, the groove is located on the outer peripheral side of the first annular protrusion, and the groove forms the upper combustion pit;

[0017] Along the axial direction of the piston body, the distance between the lowest point of the upper combustion pit and the lowest point of the lower combustion pit is a fourth distance h4, h4

[0018] As a preferred solution of the above engine piston, the diameter of the piston body is D;

[0019] ​​Along the radial direction of the piston body, the diameter D4 corresponding to the farthest end of the upper combustion pit away from the central axis of the piston body is (0.76-0.83)D.

[0020] An engine comprises a cylinder head, an engine block and a fuel injector, wherein a cylinder chamber is formed between the cylinder head and the engine block, and the engine further comprises the above-mentioned engine piston, wherein the piston body is slidably arranged in the cylinder chamber, and when the piston body is located at the top dead center, a combustion chamber is formed between the cylinder head and the top of the piston body; the fuel injector is arranged on the cylinder head and is used to inject fuel into the combustion chamber;

[0021] Along the axial direction of the piston body, when the piston body is at the top dead center, the distance between the point where the central oil beam hits the wall when it enters the lower combustion pit and the lowest point of the lower combustion pit is a third distance h3; h3<h2.

[0022] As a preferred solution of the above engine, h3=(0.7~0.8)h1.

[0023] An engine control method is used to be implemented in the above engine, and the engine control method includes:

[0024] When the engine is running at low load, determine whether the fuel can be completely sprayed within the preset injection duration based on the total injection amount and the current rail pressure;

[0025] If the fuel can be completely sprayed within the preset injection duration, spraying fuel into the combustion chamber according to the preset injection start crank angle and the preset injection duration;

[0026] If the fuel cannot be completely sprayed within the preset injection duration, the crankshaft angle for starting the injection and the injection duration are adjusted according to the total injection amount, the current rail pressure and the preset injection duration; the injection rate during the current injection within the preset injection duration is adjusted; and fuel is sprayed into the combustion chamber according to the adjusted crankshaft angle for starting the injection, the adjusted injection duration and the adjusted injection rate.

[0027] As a preferred solution of the above engine control method, the corresponding crankshaft angle when the central oil beam hits the wall at the highest point of the throat of the lower combustion pit is k°CA;

[0028] The crankshaft angle range corresponding to the preset injection duration is: -(|k|+A)°CA~|k|°CA;

[0029] The preset crankshaft angle for starting fuel injection is: -(|k|+A)°CA;

[0030] Among them, A is a positive number.

[0031] As a preferred solution of the above engine control method, the step of adjusting the crankshaft angle for starting injection and the injection duration according to the total injection amount, the current rail pressure and the preset injection duration includes:

[0032] The amount of fuel that cannot be completely sprayed within the preset injection duration is calculated based on the total injection amount, the current rail pressure and the preset injection duration;

[0033] The crankshaft angle for starting the injection is preliminarily determined based on the amount of fuel that cannot be sprayed out = -(|k|+A+B)°CA;

[0034] Determine whether the preliminarily determined crankshaft angle for starting fuel injection this time is ahead of the limit fuel injection advance angle corresponding to the explosion pressure limit;

[0035] If the preliminarily determined crankshaft angle for starting injection this time is ahead of the limit injection advance angle corresponding to the explosion pressure limit, the crankshaft angle for starting injection this time is determined to be equal to the limit injection advance angle corresponding to the explosion pressure limit, and the crankshaft angle range corresponding to the duration of this injection is determined to be: the limit injection advance angle corresponding to the explosion pressure limit ~ |k | °CA;

[0036] If the preliminarily determined crankshaft angle for starting injection this time is after the limit injection advance angle corresponding to the explosion pressure limit, the crankshaft angle for starting injection this time is determined to be -(|k|+A+B)°CA, and the crankshaft angle range corresponding to the injection duration this time is determined to be: -(|k|+A+B)°CA~|k|°CA;

[0037] Among them, B is a positive number.

[0038] As a preferred solution of the above engine control method, the specific steps of adjusting the injection rate during the preset injection duration during the current injection include:

[0039] The injection rate during the current injection is adjusted to be ≥ (the maximum injection rate during the current injection*C); wherein 0.5≤C<1.

[0040] As a preferred solution of the above engine control method, when the engine is running at high load, it is determined whether to adjust the crankshaft angle for starting fuel injection this time according to the engine fuel consumption and the exhaust smoke density of the engine;

[0041] If the crankshaft angle for starting fuel injection is not adjusted, fuel is injected into the combustion chamber according to the preset crankshaft angle for starting fuel injection;

[0042] If the crankshaft angle for starting fuel injection is adjusted, the crankshaft angle for starting fuel injection is adjusted according to the engine fuel consumption and the exhaust smoke density of the engine; fuel is injected into the combustion chamber according to the adjusted crankshaft angle for starting fuel injection.

[0043] As a preferred solution of the above engine control method, when the engine is running at high load, the injection rate of each injection within the preset injection duration is adjusted to ≤ (maximum injection rate of each injection*F); wherein 0.5≤F<1.

[0044] Beneficial effects of the present invention:

[0045] The present invention provides an engine piston, an engine and an engine control method. By convexly providing a second annular protrusion on the side wall of the central boss and setting h3<h2

[0046] Since the total fuel injection amount is relatively large when the engine is running at high load, by setting h3<h2

[0047] Therefore, when the engine is running at low load, it can effectively improve the air utilization rate and combustion effect, and can effectively improve the engine's loading capacity; when the engine is running at high load, it can effectively reduce the phenomenon of engine performance deterioration, thereby effectively improving the engine's working performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a structural schematic diagram of a combustion chamber provided by a specific embodiment of the present invention;

[0049] Figure 2 is a dimensional diagram of a combustion chamber provided by a specific embodiment of the present invention;

[0050] Figure 3 is a fuel distribution diagram of a combustion chamber provided by a specific embodiment of the present invention;​​

[0051] Figure 4 The process of the engine control method provided by the specific embodiment of the present invention is Figure 1 ;

[0052] Figure 5 The process of the engine control method provided by the specific embodiment of the present invention is Figure 2 ;

[0053] Figure 6 The process of the engine control method provided by the specific embodiment of the present invention is Figure 3 ;

[0054] Figure 7 The process of the engine control method provided by the specific embodiment of the present invention is Figure 4 ;

[0055] Figure 8 It is a comparison diagram of cylinder pressure curves before and after optimization when the engine is running at low load provided by a specific embodiment of the present invention;

[0056] Fig. 9 It is a comparison diagram of instantaneous heat release rate curves before and after optimization when the engine is running at low load provided by a specific embodiment of the present invention;

[0057] Fig.10 This is a diagram showing the atomization and diffusion effect of the central oil beam in the lower combustion pit before optimization at 0°CA provided by a specific embodiment of the present invention;

[0058] Fig.11 This is a diagram showing the atomization and diffusion effect of the optimized central oil beam in the lower combustion pit at 0°CA provided by a specific embodiment of the present invention;

[0059] Fig.12 This is a combustion effect diagram of the lower front combustion pit at 40°CA provided by a specific embodiment of the present invention;

[0060] Fig.13 This is a combustion effect diagram of the optimized lower combustion pit at 40°CA provided by a specific embodiment of the present invention;

[0061] Fig.14 It is a comparison diagram of in-cylinder pressure curves before and after optimization when the engine is running at high load provided by a specific embodiment of the present invention;

[0062] Fig.15 It is a comparison diagram of instantaneous heat release rate curves before and after optimization when the engine is running at high load provided by a specific embodiment of the present invention.

[0063] In the figure:

[0064] 11. Central boss; 12. Lower combustion pit; 13. Upper combustion pit; 14. Second annular protrusion;

[0065] 2. Combustion chamber. DETAILED DESCRIPTION

[0066] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0067] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0068] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0069] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0070] The present invention provides an engine piston, such as Figure 1-3As shown, the engine piston includes a piston body, a center boss 11 and a first annular protrusion are provided on the top of the piston body, a lower combustion pit 12 is formed between the center boss 11 and the first annular protrusion, and an upper combustion pit 13 is formed on the outer peripheral side of the first annular protrusion on the piston body. A second annular protrusion 14 is provided on the side wall of the center boss 11. Along the axial direction of the piston body, the spacing between the highest point of the first annular protrusion and the lowest point of the lower combustion pit 12 is a first spacing h1. Along the axial direction of the piston body, the spacing between the first contour line and the lowest point of the lower combustion pit 12 is a first spacing h1, and the first contour line is a connecting contour line of the connecting contour line of the second annular protrusion 14 and the center boss 11 that is far away from the lowest point of the lower combustion pit 12. The spacing between the protrusion vertex of the second annular protrusion 14 and the lowest point of the lower combustion pit 12 is a second spacing h2. h2

[0071] The present invention also provides an engine, including a cylinder head, an engine block and an injector, wherein a cylinder chamber is formed between the cylinder head and the engine block, and the engine also includes the above-mentioned engine piston. The piston body is slidably disposed in the cylinder chamber. When the piston body is located at the top dead center, a combustion chamber 2 is formed between the cylinder head and the top of the piston body. The injector is disposed in the cylinder head for injecting fuel into the combustion chamber 2. Along the axial direction of the piston body, when the piston body is located at the top dead center, the distance between the point where the central oil beam hits the wall when it enters the lower combustion pit 12 and the lowest point of the lower combustion pit 12 is a third distance h3; h3<h2. That is, h3<h2

[0072] By protruding a second annular protrusion 14 on the side wall of the central boss 11, and setting h3<h2

[0073] ​​​Since the total fuel injection amount is relatively large when the engine is running at high load, by setting h3<h2

[0074] Therefore, by adopting the engine piston, when the engine is running at low load, the air utilization rate and combustion effect can be effectively improved, and the engine loading capacity can be effectively improved; when the engine is running at high load, the phenomenon of engine performance deterioration can be effectively reduced, thereby effectively improving the working performance of the engine.

[0075] Specifically, the loading capacity of the engine refers to the output power that the engine can achieve under specified conditions. Low-load operation of the engine refers to the engine speed being less than the rated speed, and / or the engine operating power being less than the set operating power threshold. High-load operation of the engine refers to the engine speed being equal to the rated speed, and the engine operating power being greater than or equal to the set operating power threshold. Specifically, for a diesel generator, after the engine speed increases to the rated speed, the engine speed is constant at the rated speed. Among them, the set operating power threshold is an empirical value obtained from a large number of previous tests, or the set operating power threshold is an artificially set power threshold. In this embodiment, the exemplary setting of the set operating power threshold is 25% of the rated power of the engine.

[0076] Preferably, if Figure 2 As shown, along the axial direction of the piston body, the distance between the top of the combustion chamber 2 and the lowest point of the lower combustion pit 12 is the combustion chamber height h. h1=(0.43~0.5)h. h3=(0.7~0.8)h1. With such a configuration, the depth of the lower combustion pit 12 is deeper, and the point where the central oil beam hits the wall when the piston body is at the top dead center is located in the lower combustion pit 12 and close to the uppermost area in the lower combustion pit 12, so that the fuel injected into the lower combustion pit 12 can be better atomized and diffused in the lower combustion pit 12, based on the blocking effect of the second annular protrusion 14, so that the effect of the fuel on the air in the lower combustion pit 12 can be further improved, so that the combustion heat release in the lower combustion pit 12 is more concentrated, so that the loading capacity of the engine when running at low load can be further improved.

[0077] More preferably, if Figure 2 ​As shown in FIG. 1 , the apex of the second annular protrusion 14 is located at the same height as the farthest end of the lower combustion pit 12 away from the central axis of the piston body. Compared with the apex of the second annular protrusion 14 being lower than the farthest end of the lower combustion pit 12 away from the central axis of the piston body, the combustion heat release concentrated area occupied by the second annular protrusion 14 in the lower combustion pit 12 can be reduced as much as possible. Figure 3 As shown, the shadow in the lower combustion pit 12 is the approximate concentrated distribution position of the fuel in the lower combustion pit 12; secondly, it is convenient to process the second annular protrusion 14. In this embodiment, it is preferred that the cross section of the second annular protrusion 14 is in the shape of an arc. As an alternative, the convex apex of the second annular protrusion 14 is higher than the farthest end of the lower combustion pit 12 away from the central axis of the piston body. It can be understood that when the convex apex of the second annular protrusion 14 is higher than the farthest end of the lower combustion pit 12 away from the central axis of the piston body, the cross section of the second annular protrusion 14 is arc-shaped, but not arc-shaped.

[0078] Among them, Figure 2 As shown, the diameter of the piston body is defined as D. The diameter of the first contour line is D1, and the first contour line is the connecting contour line of the second annular protrusion 14 and the central boss 11, which is far away from the lowest point of the lower combustion pit 12. The diameter of the second contour line is D2, and the second contour line is the connecting contour line of the second annular protrusion 14 and the central boss 11, which is close to the lowest point of the lower combustion pit 12. Along the radial direction of the piston body, the corresponding diameter at the farthest end of the lower combustion pit 12 away from the central axis of the piston body is D3. Along the radial direction of the piston body, the corresponding diameter at the farthest end of the upper combustion pit 13 away from the central axis of the piston body is D4.

[0079] Preferably, if Figure 2 As shown, D1=(0.2~0.25)D. D2=(0.3~0.35)D. D3=(0.45~0.6)D. In this way, combined with the first spacing h1 and the third spacing h3, when the engine is running at a low load, it is possible to prevent most of the fuel injected into the lower combustion pit 12 from diffusing along the side wall of the central boss 11 to the central area of ​​the combustion chamber 2, so that the fuel injected into the lower combustion pit 12 can be atomized, diffused and burned in the lower combustion pit 12 as much as possible.

[0080] Preferably, if Figure 1-3As shown, a groove is provided on the top of the piston body, and the groove is located on the outer peripheral side of the first annular protrusion, and the groove forms an upper combustion pit 13. Along the axial direction of the piston body, the distance between the lowest point of the upper combustion pit 13 and the lowest point of the lower combustion pit 12 is a fourth distance h4, h4 Figure 3 As shown, the shadow in the upper combustion pit 13 is the approximate concentrated distribution position of the fuel in the upper combustion pit 13, so that the fuel injected into the upper combustion pit 13 can be atomized, diffused and burned in the upper combustion pit 13 as much as possible, which can effectively improve the air utilization rate of the fuel in the upper combustion pit 13, and can effectively improve the combustion effect of the mixed combustion of the fuel and the air in the upper combustion pit 13, so that the combustion heat release in the upper combustion pit 13 is more concentrated, thereby further improving the loading capacity of the engine.

[0081] Specifically, Figure 3 The shadow in the lower combustion pit 12 is the approximate concentrated distribution position of the fuel in the lower combustion pit 12; Figure 3 The shadow in the upper combustion pit 13 in the figure is the approximate concentrated distribution position of the fuel in the upper combustion pit 13. Figure 3 It can be seen that by setting the second annular protrusion 14, when the engine is running at low load, the fuel injected into the lower combustion pit 12 is basically concentrated in the shadow area of ​​the lower combustion pit 12. When the engine is running at high load, the protrusion height of the second annular protrusion 14 has a small hindering effect on the fuel injected into the lower combustion pit 12 to diffuse along the side wall of the central boss 11 to the central area of ​​the combustion chamber 2, and the fuel can diffuse along the side wall of the central boss 11 to the central area of ​​the combustion chamber 2. By setting h4

[0082] Preferably, if Figure 2 ​​As shown, D4=(0.76~0.83)D. With such a configuration, the diameter D4 corresponding to the farthest end of the upper combustion pit 13 away from the central axis of the piston body is larger. When the engine is running at high load, the air in the clearance space above the upper combustion pit 13 can be fully utilized, thereby effectively ensuring the loading capacity of the engine when running at high load. Among them, the clearance space refers to the gap space between the cylinder head and the upper part of the upper combustion pit 13.

[0083] Specifically, Figure 2 As shown, along the axial direction of the piston body, the distance between the farthest end of the upper combustion pit 13 away from the central axis of the piston body and the lowest point of the lower combustion pit 12 is a fifth distance h5, h1<h5<h.

[0084] It is understandable that if Figure 2 As shown, according to the combustion chamber height h, the third spacing h3, and the diameter D3 corresponding to the point where the central oil beam hits the wall of the lower combustion pit 12 when the piston body is at the top dead center, the injection angle of the central oil beam can be calculated, so that the cone angle range of the injection hole on the injector can be determined. The fuel is injected into the combustion chamber 2 from the injection hole of the injector. Among them, the specific structure of the injector belongs to the prior art and will not be repeated here.

[0085] The present invention also provides an engine control method, which is used to be implemented in the above-mentioned engine.

[0086] The engine control method includes:

[0087] The preset crankshaft angle for starting fuel injection and the preset fuel injection duration are determined in advance based on the crankshaft angle when the central oil beam hits the highest point of the throat of the lower combustion pit 12.

[0088] When the piston body is at the top dead center, the corresponding crankshaft angle when the central oil beam enters the lower combustion pit 12 and hits the wall is 0°CA.

[0089] The crankshaft angle corresponding to the collision between the central oil beam and the highest point of the throat of the lower combustion pit 12 is k°CA. Wherein, k is a positive or negative value. Specifically, before the piston body reaches the top dead center, the crankshaft angle k corresponding to the collision between the central oil beam and the highest point of the throat of the lower combustion pit 12 is a negative value. After the piston body reaches the top dead center, the crankshaft angle k corresponding to the collision between the central oil beam and the highest point of the throat of the lower combustion pit 12 is a positive value. It can be understood that the value of k is different for engines of different specifications.

[0090] The crankshaft angle range corresponding to the preset injection duration is: -(|k|+A)°CA~|k|°CA.

[0091] The preset crankshaft angle for starting fuel injection is: -(|k|+A)°CA. Wherein, A is a positive number. |k| refers to the absolute value of k. It can be understood that fuel injection starts before the piston body reaches the top dead center.

[0092] The preset end-injection crankshaft angle is: |k|°CA.

[0093] In this embodiment, A=7 is set as an example. The fuel will not directly hit the wall during the initial injection, and the fuel will start to hit the wall after the crankshaft angle changes by about 7°CA. Therefore, in this embodiment, the preset crankshaft angle for starting injection is -(|k|+7)°CA. It can be understood that for engines of different specifications, the value of A is different. The value of A is related to the crankshaft angle from the fuel injection to the fuel hitting the wall.

[0094] like Figure 4 and Figure 5 As shown, when the engine is running at low load, the engine control method also includes:

[0095] S100. Obtain the total fuel injection amount and the current rail pressure.

[0096] S200: Determine whether the fuel can be completely injected within a preset injection duration according to the total injection amount and the current rail pressure.

[0097] If the fuel can be completely sprayed within the preset injection duration, step S300 is executed.

[0098] S300, injecting fuel into the combustion chamber 2 according to a preset fuel injection start crankshaft angle and a preset fuel injection duration.

[0099] It can be understood that the crankshaft angle range corresponding to the preset injection duration is: -(|k|+A)°CA~|k|°CA, the preset crankshaft angle for starting injection is: -(|k|+A)°CA, and when the piston body is at the top dead center, the point where the central oil beam hits the wall when it enters the combustion chamber is located in the lower combustion pit 12. For low-load operation of the engine, fuel injection begins during the movement of the piston body to the top dead center, and a small part of the injected fuel is injected into the upper combustion pit 13, and most of it is injected into the lower combustion pit 12. During the movement of the piston body from the top dead center to the bottom, the fuel is roughly injected into the lower combustion pit 12, so that most of the total fuel injection amount is injected into the lower combustion pit 12, and a small part is injected into the upper combustion pit 13, thereby better improving the effect of utilizing the air in the lower combustion pit 12, and the combustion in the lower combustion pit 12 is more concentrated, which can further improve the loading capacity of the engine when running at low load.

[0100] Secondly, since h1=(0.43~0.5)h, h3=(0.7~0.8)h1, the depth of the lower combustion pit 12 is relatively deep, and when the piston body is at the top dead center, the point where the central oil beam is injected into the lower combustion pit 12 and hits the wall is located in the lower combustion pit 12 and in the lower combustion pit 12 near the top area. For low-load operation of the engine, most of the fuel injected into the lower combustion pit 12 can be better atomized and diffused in the lower combustion pit 12, and based on the blocking effect of the second annular protrusion 14, the effect of the fuel utilizing the air in the lower combustion pit 12 can be further improved, so that the combustion heat release in the lower combustion pit 12 is more concentrated, thereby further improving the loading capacity of the engine when running at low load.

[0101] Secondly, since h4

[0102] If the fuel cannot be completely sprayed within the preset injection duration, step S400 is executed.

[0103] S400, adjusting the crankshaft angle for starting injection and the duration of this injection according to the total injection amount, the current rail pressure and the preset injection duration; adjusting the injection rate during the preset injection duration of this injection; and injecting fuel into the combustion chamber 2 according to the adjusted crankshaft angle for starting injection, the adjusted injection duration and the adjusted injection rate.

[0104] Specifically, Figure 4 and Figure 5 As shown, the specific steps of adjusting the crankshaft angle for starting injection and the injection duration according to the total injection amount, the current rail pressure and the preset injection duration include:

[0105] S410: Calculate the amount of fuel that cannot be completely injected within the preset injection duration according to the total injection amount, the current rail pressure and the preset injection duration.

[0106] ​Specifically, the amount of fuel that can be injected within the preset injection duration is calculated based on the current rail pressure and the preset injection duration. The difference between the total injection amount and the amount of fuel that can be injected within the preset injection duration is calculated, which is the amount of fuel that cannot be injected within the preset injection duration. Among them, the specific calculation method for calculating the amount of fuel that can be injected within the preset injection duration based on the current rail pressure and the preset injection duration belongs to the prior art, so it will not be repeated here.

[0107] S420. Preliminarily determine the crankshaft angle for starting the injection of fuel at this time = -(|k|+A+B)°CA based on the amount of fuel that cannot be completely injected.

[0108] Specifically, the value of B is obtained from the first table according to the amount of fuel that cannot be completely sprayed. The first table is formed by the amount of fuel that cannot be completely sprayed and the value of B. The first table is an empirical table obtained from a large number of previous tests. B is a positive number.

[0109] S430, judging whether the preliminarily determined crankshaft angle for starting injection this time is ahead of the limit injection advance angle corresponding to the explosion pressure limit. The limit injection advance angle corresponding to the explosion pressure limit is an empirical value obtained from a large number of previous tests. Under different engine loads, the limit injection advance angle corresponding to the explosion pressure limit is different. The explosion pressure limit refers to the maximum explosion pressure value corresponding to the structural strength of the engine.

[0110] If the preliminarily determined crankshaft angle for starting the injection this time is ahead of the limit injection advance angle corresponding to the explosion pressure limit, step S440 is executed.

[0111] S440, determining that the crankshaft angle for starting the current injection is equal to the limit injection advance angle corresponding to the explosion pressure limit, and determining that the crankshaft angle range corresponding to the current injection duration is: the limit injection advance angle corresponding to the explosion pressure limit ~|k|°CA.

[0112] If the preliminarily determined crankshaft angle for starting the injection this time is after the limit injection advance angle corresponding to the explosion pressure limit, step S450 is executed.

[0113] S450, determine the crankshaft angle for starting the current injection = -(|k|+A+B)°CA, and determine the crankshaft angle range corresponding to the current injection duration is: -(|k|+A+B)°CA to |k|°CA.

[0114] The specific steps of adjusting the injection rate during the preset injection duration of this injection include:

[0115] The injection rate of this injection within the preset injection duration is adjusted to be ≥ (maximum injection rate of this injection*C), wherein 0.5≤C<1.

[0116] It can be understood that by adjusting the time of starting fuel injection earlier and adjusting the injection rate within the preset injection duration during this fuel injection to be larger, the total fuel injection amount can be sprayed as much as possible within the current injection duration, and the fuel injected into the combustion chamber 2 can be roughly injected into the lower combustion pit 12, thereby further making the combustion in the lower combustion pit 12 more concentrated, so that when the engine is running at low load, the engine's loading capacity can be further improved.

[0117] In this embodiment, an exemplary setting is: the injection rate during the preset injection duration during the current injection is adjusted to be equal to the maximum injection rate during the current injection*0.5.

[0118] Specifically, the single injection process of the injector is as follows: when the injector starts to inject, the injection rate gradually increases from zero to the maximum injection rate and stabilizes to the maximum injection rate; when the injector ends injection, the injection rate gradually decreases from the maximum injection rate to zero.

[0119] like Figure 6 and Figure 7 As shown, when the engine is running at high load, the engine control method also includes:

[0120] S500: Obtain engine fuel consumption and engine exhaust smoke density.

[0121] Specifically, engine fuel consumption refers to the average value of the total amount of fuel consumed during engine operation.

[0122] Specifically, the exhaust smoke density of the engine is monitored by a smoke density sensor.

[0123] The S600 determines whether to adjust the crankshaft angle for starting fuel injection based on the engine fuel consumption and the exhaust smoke density of the engine.

[0124] Specifically, step S600 includes:

[0125] Determine whether the engine fuel consumption is greater than or equal to the set fuel consumption; determine whether the engine exhaust smoke is greater than or equal to the set smoke value. The set fuel consumption is an empirical value obtained from a large number of previous tests, and the set smoke value is an empirical value obtained from a large number of previous tests.

[0126] If the engine fuel consumption is less than the set fuel consumption, and the exhaust smoke density of the engine is less than the set smoke density value, the crankshaft angle for starting the fuel injection this time is not adjusted, and step S700 is executed.

[0127] S700, fuel is injected into the combustion chamber 2 according to the preset fuel injection crankshaft angle.

[0128] If the engine fuel consumption is greater than or equal to the set fuel consumption, and / or the exhaust smoke density of the engine is greater than or equal to the set smoke density value, the crankshaft angle for starting the fuel injection this time is adjusted and step S800 is executed.

[0129] S800, adjusting the crankshaft angle for starting fuel injection this time according to the engine fuel consumption and the engine exhaust smoke density; and injecting fuel into the combustion chamber 2 according to the adjusted crankshaft angle for starting fuel injection.

[0130] Specifically, Figure 6 and Figure 7 As shown, the specific steps of adjusting the crankshaft angle for starting fuel injection this time according to the engine fuel consumption and the exhaust smoke density of the engine include:

[0131] S810, preliminarily determine the crankshaft angle for starting the fuel injection this time = -(|k|+A+E)°CA based on the engine fuel consumption and the engine exhaust smoke density. That is, adjust the time for starting the fuel injection in advance to improve the mixing effect of fuel and air, reduce the engine fuel consumption, and reduce the engine exhaust smoke density.

[0132] Specifically, the value of E is obtained from the second table according to the engine fuel consumption and the exhaust smoke density of the engine. The second table is formed by the engine fuel consumption, the exhaust smoke density of the engine and the value of E. The second table is an empirical table obtained from a large number of previous tests. E is a positive number.

[0133] S820, judging whether the preliminarily determined crankshaft angle for starting injection this time is ahead of the limit injection advance angle corresponding to the explosion pressure limit. The limit injection advance angle corresponding to the explosion pressure limit is an empirical value obtained from a large number of previous tests. Under different engine loads, the limit injection advance angle corresponding to the explosion pressure limit is different. The explosion pressure limit refers to the maximum explosion pressure value corresponding to the structural strength of the engine.

[0134] If the preliminarily determined crankshaft angle for starting the injection this time is ahead of the limit injection advance angle corresponding to the explosion pressure limit, step S830 is executed.

[0135] S830: Determine the limit injection advance angle corresponding to the crankshaft angle for starting the injection this time = the explosion pressure limit.

[0136] If the preliminarily determined crankshaft angle for starting the injection this time is after the limit injection advance angle corresponding to the explosion pressure limit, step S840 is executed.

[0137] S840: Determine the crankshaft angle for starting fuel injection this time = -(|k|+A+E)°CA.

[0138] Preferably, when the engine is running at high load, the injection rate of each injection during the preset injection duration is adjusted to be ≤ (maximum injection rate of each injection*F). Wherein, 0.5≤F<1. That is, during the execution of steps S700 and S800, the injection rate of each injection during the preset injection duration is adjusted to be ≤ (injection rate of each injection*F).

[0139] With such arrangement, when the engine is running at high load, the amount of fuel injected into the lower combustion pit 12 within a preset injection period can be effectively reduced. The second annular protrusion 14 is arranged in conjunction with the lower combustion pit 12, and the height of the second annular protrusion 14 has a small hindering effect on the diffusion of the fuel injected into the lower combustion pit 12 along the side wall of the center boss 11 to the central area of ​​the combustion chamber 2. This can further avoid the phenomenon that too much fuel is injected into the lower combustion pit 12 within the preset injection period, resulting in excessive fuel concentration in the lower combustion pit 12 and greater exhaust smoke from the engine, thereby further reducing the phenomenon of performance deterioration when the engine is running at high load.

[0140] Secondly, with such arrangement, when the engine is running at high load, combined with the structural characteristics of the upper combustion pit 13, h4

[0141] Secondly, for high-load operation of the engine, since D4=(0.76~0.83)D, the diameter D4 corresponding to the farthest end of the upper combustion pit 13 away from the central axis of the piston body is larger, so that the fuel can make full use of the air in the clearance space above the upper combustion pit 13, thereby further ensuring the loading capacity of the engine when running at high load.

[0142] In this embodiment, an exemplary setting is: when the engine is running at high load, the injection rate during the preset injection duration of each injection is adjusted to be equal to the maximum injection rate of each injection*0.5.

[0143] Therefore, by adopting the engine control method, when the engine is running at low load, the air utilization rate and combustion effect can be further improved, and the engine's loading capacity can be further improved; when the engine is running at high load, the phenomenon of engine performance deterioration can be further reduced, and the engine's loading capacity can be guaranteed when running at high load, thereby further improving the engine's working performance.

[0144] ​Specifically, during the operation of the engine, it is determined in real time whether the engine speed is less than the set speed; and it is determined in real time whether the engine power is greater than or equal to the set operating power threshold. If the engine speed is equal to the set speed, and the engine power is greater than or equal to the set operating power threshold, it is determined that the engine is running at high load. If the engine speed is less than the set speed, and / or the engine power is less than the set operating power threshold, it is determined that the engine is running at low load. The set speed is the rated speed of the engine.

[0145] Specifically, in this embodiment, taking |k|=7 as an example, the crankshaft angle range corresponding to the preset injection duration is: -14°CA to 7°CA; the preset crankshaft angle for starting injection is: -14°CA.

[0146] Depend on Figure 8 It can be clearly seen that when the engine is running at low load, after the crankshaft angle is -6°CA, the in-cylinder pressure of the engine increases significantly after optimization. Fig. 9 It can be clearly seen that when the engine is running at low load, the instantaneous heat release rate of fuel combustion is significantly increased after the optimization after the crankshaft angle is -8°CA. This effectively improves the loading capacity of the engine when running at low load. The in-cylinder pressure of the engine refers to the cylinder pressure in the part of the cylinder chamber of the engine that is connected to the combustion chamber 2.

[0147] contrast Fig.10 and Fig.11 It can be clearly seen that at 0°CA, the atomization and diffusion effect of the optimized central oil beam in the lower combustion pit 12 is significantly improved.

[0148] contrast Fig.12 and Fig.13 It can be clearly seen that at 40°CA, the combustion area in the lower combustion pit 12 is greatly expanded, which effectively improves the air utilization rate. For low-load operation of the engine, the second annular protrusion 14 can effectively prevent the combustion area in the lower combustion pit 12 from further spreading to the central area of ​​the combustion chamber 2.

[0149] Specifically, in this embodiment, when the engine is running at low load, the air utilization rate is increased by 14%, the engine loading capacity is enhanced by 9%, and the exhaust temperature of the engine is increased by 20°C to 30°C.

[0150] Depend on Fig.14 It can be clearly seen that when the engine is running at high load, the in-cylinder pressure of the engine remains basically the same before and after optimization. Fig.15 It can be clearly seen that when the engine is running at high load, the instantaneous heat release rate of fuel combustion remains basically the same before and after optimization, which effectively reduces the phenomenon of performance deterioration when the engine is running at high load.

[0151] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An engine control method, wherein the engine comprises a cylinder head, an engine block, an injector and an engine piston, wherein a cylinder chamber is formed between the cylinder head and the engine block, and the engine piston comprises a piston body, wherein a center boss (11) and a first annular boss are provided on the top of the piston body; a lower combustion pit (12) is formed between the center boss (11) and the first annular boss; and an upper combustion pit (13) is formed on the outer peripheral side of the first annular boss on the piston body; and the method is characterized in that: A second annular protrusion (14) is convexly provided on the side wall of the central protrusion (11); Along the axial direction of the piston body, the distance between the highest point of the first annular protrusion and the lowest point of the lower combustion pit (12) is a first distance h1; the distance between the first contour line and the lowest point of the lower combustion pit (12) is the first distance h1, and the first contour line is a connecting contour line of the connecting contour lines of the second annular protrusion (14) and the central boss (11) that is far away from the lowest point of the lower combustion pit (12); the distance between the protrusion vertex of the second annular protrusion (14) and the lowest point of the lower combustion pit (12) is a second distance h2; h2<h1; The piston body is slidably disposed in the cylinder chamber, and when the piston body is at the top dead center, a combustion chamber (2) is formed between the cylinder head and the top of the piston body; the fuel injector is disposed on the cylinder head and is used to inject fuel into the combustion chamber (2); along the axial direction of the piston body, when the piston body is at the top dead center, the distance between the point where the central oil beam hits the wall of the lower combustion pit (12) and the lowest point of the lower combustion pit (12) is a third distance h3; h3<h2; The engine control method comprises: When the engine is running at low load, determine whether the fuel can be completely sprayed within the preset injection duration based on the total injection amount and the current rail pressure; If the fuel can be completely sprayed within the preset fuel injection duration, then fuel is sprayed into the combustion chamber (2) according to the preset fuel injection start crank angle and the preset fuel injection duration; If the fuel cannot be completely sprayed within the preset injection duration, the crankshaft angle for starting the injection and the injection duration are adjusted according to the total injection amount, the current rail pressure and the preset injection duration; the injection rate during the current injection within the preset injection duration is adjusted; and the fuel is sprayed into the combustion chamber (2) according to the adjusted crankshaft angle for starting the injection, the adjusted injection duration and the adjusted injection rate.

2. The engine control method according to claim 1, characterized in that: When the piston body is located at the top dead center, a combustion chamber (2) is formed between the engine cylinder head and the top of the piston body; along the axial direction of the piston body, the distance between the top of the combustion chamber (2) and the lowest point of the lower combustion pit (12) is the combustion chamber height h; h1=(0.43-0.5)h.

3. The engine control method according to claim 1, characterized in that: The diameter of the piston body is D; The diameter of the first contour line D1=(0.2-0.25)D; The diameter D2 of the second contour line is (0.3-0.35)D, and the second contour line is a connecting contour line of the connecting contour lines of the second annular protrusion (14) and the central boss (11) close to the lowest point of the lower combustion pit (12).

4. The engine control method according to claim 1, characterized in that: The diameter of the piston body is D; Along the radial direction of the piston body, the diameter D3 corresponding to the farthest end of the lower combustion pit (12) away from the central axis of the piston body is (0.45-0.6)D.

5. The engine control method according to any one of claims 1 to 4, characterized in that: A groove is provided on the top of the piston body, the groove is located on the outer peripheral side of the first annular protrusion, and the groove forms the upper combustion pit (13); Along the axial direction of the piston body, the distance between the lowest point of the upper combustion pit (13) and the lowest point of the lower combustion pit (12) is a fourth distance h4, h4 < h1; the angle between the line between the lowest point of the upper combustion pit (13) and the highest point of the first annular protrusion and the plane perpendicular to the axial direction of the piston body is α, 0° < α < 15°.

6. The engine control method according to any one of claims 1 to 4, characterized in that: The diameter of the piston body is D; Along the radial direction of the piston body, the diameter D4 corresponding to the farthest end of the upper combustion pit (13) away from the central axis of the piston body is (0.76-0.83)D.

7. The engine control method according to claim 1, characterized in that: h3=(0.7~0.8)h1.

8. The engine control method according to claim 1, characterized in that: The corresponding crankshaft angle when the central oil beam hits the wall at the highest point of the throat of the lower combustion pit (12) is k°CA; The crankshaft angle range corresponding to the preset injection duration is: -(|k|+A)°CA~|k|°CA; The preset crankshaft angle for starting fuel injection is: -(|k|+A)°CA; Among them, A is a positive number.

9. The engine control method according to claim 8, characterized in that: The steps of adjusting the crankshaft angle for starting injection and the duration of injection according to the total injection amount, the current rail pressure and the preset injection duration include: The amount of fuel that cannot be completely injected within the preset injection duration is calculated according to the total injection amount, the current rail pressure and the preset injection duration; The crankshaft angle for starting the injection is preliminarily determined based on the amount of fuel that cannot be sprayed out = -(|k|+A+B)°CA; Determine whether the preliminarily determined crankshaft angle for starting fuel injection this time is ahead of the limit fuel injection advance angle corresponding to the explosion pressure limit; If the preliminarily determined crankshaft angle for starting injection this time is ahead of the limit injection advance angle corresponding to the explosion pressure limit, the crankshaft angle for starting injection this time is determined to be equal to the limit injection advance angle corresponding to the explosion pressure limit, and the crankshaft angle range corresponding to the duration of this injection is determined to be: the limit injection advance angle corresponding to the explosion pressure limit ~ |k | °CA; If the preliminarily determined crankshaft angle for starting injection this time is after the limit injection advance angle corresponding to the explosion pressure limit, the crankshaft angle for starting injection this time is determined to be -(|k|+A+B)°CA, and the crankshaft angle range corresponding to the injection duration this time is determined to be: -(|k|+A+B)°CA~|k|°CA; Among them, B is a positive number.

10. The engine control method according to any one of claims 8 to 9, characterized in that: The specific steps of adjusting the injection rate during the preset injection duration during the current injection include: The injection rate during the current injection is adjusted to be ≥ (the maximum injection rate during the current injection*C); wherein 0.5≤C<1.

11. The engine control method according to any one of claims 8 to 9, characterized in that: When the engine is running at high load, whether to adjust the crankshaft angle for starting fuel injection this time is determined based on the engine fuel consumption and the exhaust smoke density of the engine; If the crankshaft angle for starting fuel injection is not adjusted, fuel is injected into the combustion chamber (2) according to the preset crankshaft angle for starting fuel injection; If the crankshaft angle for starting fuel injection is adjusted, the crankshaft angle for starting fuel injection is adjusted according to the fuel consumption of the engine and the exhaust smoke density of the engine; fuel is injected into the combustion chamber (2) according to the adjusted crankshaft angle for starting fuel injection.

12. The engine control method according to any one of claims 8 to 9, characterized in that: When the engine is running at high load, the injection rate of each injection during the preset injection duration is adjusted to be ≤ (maximum injection rate of each injection*F); wherein 0.5≤F<1.

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