In-cylinder braking method of engine

Abstract

The invention discloses a braking method in an engine cylinder, which takes 360-degree rotation of an engine crankshaft as a cycle, in two cycles, an exhaust valve is opened once in the initial stage and the final stage of the ascending process of a piston in each cycle, and an intake valve is opened once in the descending process of the piston. By adopting the method, the braking performance of the engine can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of engine control, and in particular relates to an engine cylinder braking method. Background Art

[0002] Heavy commercial vehicles will face various complex road conditions during transportation. Especially when long-distance braking is required at high speeds, or when driving on long downhill sections in mountainous areas, drivers need to brake frequently. Frequent braking will undoubtedly affect the performance of the brakes, causing the braking effect to weaken or even fail. In order to ensure driving safety, engine-assisted braking technology is widely used. Engine-assisted braking technology includes exhaust braking, deflation braking, and engine cylinder braking. Among them, engine cylinder braking has a better braking effect and is the most widely used.

[0003] The existing engine cylinder braking method is studied from two aspects: the local cam profile and the valve opening and closing time. Each engine cycle is braked only once, and the exhaust valve and the intake valve are opened only once in a braking cycle. The above engine cylinder braking method has the following problems: it cannot significantly improve the braking effect and cannot meet the increasingly high braking performance requirements. Summary of the invention

[0004] In order to solve the problem of poor braking performance of existing engine cylinder braking, the present invention proposes an engine cylinder braking method, which can improve the braking performance of the engine.

[0005] The objective of the present invention is achieved through the following technical solutions: The first aspect of the present invention discloses an engine cylinder braking method, comprising the following steps: taking the engine crankshaft rotating 360 degrees as one cycle, in two cycles, the exhaust valve is opened once at the beginning and end of the piston upward process, and the intake valve is opened once during the piston downward process.

[0006] Preferably, in the two cycles, the exhaust valve is opened once at the beginning and the end of the piston upward movement process, and the intake valve is opened once during the piston downward movement process in each cycle, including: In the first cycle, the intake valve opens at a crank angle of 90°-110° and closes at a crank angle of 270°-290°, wherein a crank angle of 0° is at compression top dead center; In the second cycle, the intake valve opens at 450°-470° crankshaft angle and closes at 630°-650° crankshaft angle.

[0007] Preferably, in the two cycles, the exhaust valve is opened once at the beginning and the end of the piston upward movement process, and the intake valve is opened once during the piston downward movement process in each cycle, including: In the first cycle, the exhaust valve is closed at a crank angle of 70°-80°, opened at a crank angle of 200°-210°, closed at a crank angle of 300°-310°, and the exhaust valve is opened at a crank angle of 330°-340°; In the second cycle, the exhaust valve is closed at a crank angle of 430°-440°, opened at a crank angle of 560°-570°, and closed at a crank angle of 660°-670°; the exhaust valve is opened at a crank angle of 690°-700°.

[0008] The beneficial effects of the present invention are: The present invention sets the engine cycle to 2 cycles and performs compression braking once in each cycle, that is, the engine cycle brakes twice, the exhaust valve opens twice and the intake valve opens once in each cycle, thereby effectively improving the braking effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0010] Figure 1 It is a lift curve diagram of the intake and exhaust valves in the engine cylinder braking method of the present invention. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0012] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0014] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0015] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use, or the positions or positional relationships commonly understood by those skilled in the art, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0016] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of 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.

[0017] The first aspect of the present invention discloses an engine cylinder braking method, in which the engine crankshaft rotates 360 degrees as one cycle. In two cycles, the exhaust valve is opened once at the beginning and end of the piston upward process, and the intake valve is opened once during the piston downward process.

[0018] The principle of in-cylinder braking is that when the brake control switch is turned on, the engine exhaust valve will open when the compression stroke approaches the top dead center, and the high-pressure gas formed by the compression stroke will be discharged from the engine cylinder, so that the energy absorbed by the compressed gas in the compression stroke will be released. As the engine repeats the cycle, the mechanical energy of the vehicle when going downhill will be dissipated by the engine compression release action, eventually slowing down the vehicle.

[0019] With the above method, the exhaust valve is opened once during the piston upward movement, i.e., during the compression stroke and the exhaust stroke, respectively, at the beginning and the end of the piston upward movement. The exhaust valve is opened at the beginning of the piston upward movement to allow the gas in the exhaust duct to flow back into the cylinder, increasing the gas volume in the cylinder, thereby enhancing the compression braking effect. The exhaust valve is opened at the end of the piston upward movement to discharge the gas in the cylinder in time, avoiding external work during the subsequent piston downward movement, thereby weakening the braking effect.

[0020] This solution sets the engine cycle to 2 cycles and performs compression braking once in each cycle, that is, the engine cycle is braked twice, the exhaust valve is opened twice and the intake valve is opened once in each cycle, thereby effectively improving the braking effect.

[0021] Specifically, refer to Figure 1 As shown in the figure, taking the 0° crankshaft angle as the compression top dead center as an example, the braking process is as follows. Figure 1 A, B, C, D, and E correspond to the engine's compression top dead center, power bottom dead center, exhaust top dead center, intake bottom dead center, and compression top dead center, respectively.

[0022] In the first cycle, the exhaust valve is closed at 70°-80° crankshaft angle, the intake valve is opened at 90°-110° crankshaft angle, the exhaust valve is opened at 200°-210° crankshaft angle, the intake valve is closed at 270°-290° crankshaft angle, the exhaust valve is closed at 300°-310° crankshaft angle, and the exhaust valve is opened at 330°-340° crankshaft angle.

[0023] In the second cycle, the exhaust valve is closed at a crankshaft angle of 430°-440°, the intake valve is opened at a crankshaft angle of 450°-470°, the exhaust valve is opened at a crankshaft angle of 560°-570°, the intake valve is closed at a crankshaft angle of 630°-650°, the exhaust valve is closed at a crankshaft angle of 660°-670°, and the exhaust valve is opened at a crankshaft angle of 690°-700°.

[0024] By adopting the above method, the braking effect can be further improved by optimizing the opening and closing time of the exhaust valve and the intake valve. Specifically, by optimizing the opening and closing time of the intake valve, the intake volume can be further increased, thereby enhancing the braking effect. By optimizing the first opening and closing time of the exhaust valve, the gas volume in the cylinder can be further increased, thereby enhancing the braking effect; by optimizing the second opening and closing time of the exhaust valve, the compression braking duration can be increased, while avoiding the piston from doing work downward.

[0025] By adopting the above method, through two compression brakings in the engine cycle, the exhaust valve is opened twice during the upward process of the piston, and combined with reasonable valve timing, the braking effect in the engine cylinder will be greatly increased, which can more effectively assist the deceleration braking of heavy commercial vehicles and enhance driving safety.

[0026] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. An engine cylinder braking method, characterized in that: The following steps are involved: The engine crankshaft rotates 360 degrees as one cycle. In the two cycles, the exhaust valve is opened once at the beginning and end of the piston's upward process, and the intake valve is opened once during the piston's downward process.

2. The engine cylinder braking method according to claim 1, characterized in that: In the two cycles, the exhaust valve is opened once at the beginning and end of the piston upward movement process, and the intake valve is opened once during the piston downward movement process in each cycle, including: In the first cycle, the intake valve opens at a crank angle of 90°-110° and closes at a crank angle of 270°-290°, wherein a crank angle of 0° is the compression top dead center; In the second cycle, the intake valve opens at 450°-470° crankshaft angle and closes at 630°-650° crankshaft angle.

3. The engine cylinder braking method according to claim 1, characterized in that: In the two cycles, the exhaust valve is opened once at the beginning and end of the piston upward movement process, and the intake valve is opened once during the piston downward movement process in each cycle, including: In the first cycle, the exhaust valve is closed at a crank angle of 70°-80°, opened at a crank angle of 200°-210°, closed at a crank angle of 300°-310°, and the exhaust valve is opened at a crank angle of 330°-340°; In the second cycle, the exhaust valve is closed at a crank angle of 430°-440°, opened at a crank angle of 560°-570°, and closed at a crank angle of 660°-670°; the exhaust valve is opened at a crank angle of 690°-700°.

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