Fuel delivery structure for cylinder injection engine

Abstract

To provide a fuel delivery structure for a cylinder injection engine capable of approximately coping with increase of fuel injection pressure and a center injection system while suppressing cost increase.SOLUTION: A fuel delivery structure for the cylinder injection engine includes a cylinder head 2, a cylinder head cover 3, an injector 4 for injecting fuel into a combustion chamber of the cylinder head 2, and a fuel delivery pipe 5 for forcibly feeding and supplying the fuel to the injector 4, where the fuel is injected directly to the combustion chamber to cause combustion with spark ignition, the cylinder head cover 3 being made of metal, the injector 4 being arranged right above the cylinder head cover 3 and the combustion chamber, the fuel delivery pipe 5 being arranged to be connected to the injector 4 right above the injector 4, and fixed to the cylinder head cover 3.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a spark ignition engine mounted on a vehicle, and more particularly to a fuel delivery structure for a direct injection engine that injects fuel directly into a combustion chamber. [Background technology]

[0002] Patent Document 1 describes an invention related to an internal combustion engine (spark ignition engine such as a gasoline engine) including a cylinder head provided with a plurality of injectors, a plurality of injector tubes into which the plurality of injectors are respectively inserted, and a plurality of ignition plug tubes into which a plurality of ignition plugs are respectively inserted, a head cover attached to the cylinder head, and a fuel delivery pipe for supplying fuel to the plurality of injectors. In the internal combustion engine described in Patent Document 1, the injector holder is connected to the fuel delivery pipe in a first region between the first end and the first injector through hole, and in a second region between the second end and the second injector through hole. The first region and the second region are formed to have lower rigidity than a third region between the first injector through hole and the second injector through hole. This relieves stress generated in the injector holder due to the difference in thermal expansion between the fuel delivery pipe and the injector holder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-85382 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the internal combustion engine described in Patent Document 1 is an in-cylinder injection (direct injection) engine that injects fuel directly into the combustion chamber with an injector, and is a so-called center injection type direct injection engine in which the injector is arranged almost directly above the combustion chamber. Patent Document 1 also discloses a fuel delivery structure for the direct injection engine. Another example of such a direct injection engine and fuel delivery structure in which the injector is arranged directly above is shown in FIG. 1. The direct injection engine 100 shown in FIG. 1 includes a resin cylinder head cover 101. The cylinder head cover 101 incorporates a cam carrier (or cam housing) 102, and is attached to a cylinder head 103 together with the cam carrier 102. In the fuel delivery structure for this direct injection engine 100, four injectors 105 and a fuel delivery pipe 106 are attached to the upper surface of the cylinder head cover 101 via a metal injector holder 104. A high-pressure fuel pump 107 is connected to one end of the fuel delivery pipe 106 , and fuel pumped from the fuel pump 107 is supplied to each injector 105 via the fuel delivery pipe 106 .

[0005] In the direct injection engine 100 of the center injection type as described above, the injector 105 is disposed immediately above the combustion chamber (not shown) of the cylinder head 103, between the intake valve (not shown) and the exhaust valve (not shown), and close to the spark plug (not shown). This is advantageous for forming a stratified mixture in the combustion chamber. In addition, since the injector 105 is embedded inside the cylinder head, the operating sound of the injector 105 is less likely to be emitted to the outside. In addition, by adopting the resin cylinder head cover 101, the direct injection engine 100 can be made lighter and have improved sound insulation. On the other hand, in the fuel delivery structure of the direct injection engine 100, in order to compensate for the strength and rigidity of the resin cylinder head cover 101 in response to the high pressure of the fuel injection pressure, the injector holder 104 and the cam carrier 102 made of an aluminum alloy are used. Therefore, compared with a conventional direct injection engine that does not support the high pressure of the fuel injection pressure or the center injection type, the number of parts increases, which causes an increase in costs.

[0006] This invention has been devised with an eye on the technical challenges described above, and aims to provide a fuel delivery structure for a direct injection engine that can appropriately accommodate increased fuel injection pressure and center injection methods while suppressing or reducing costs. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a fuel delivery structure for a cylinder injection engine comprising a cylinder head, a cylinder head cover attached to the cylinder head and covering an upper surface of the cylinder head, an injector that injects fuel into a combustion chamber of the cylinder head, and a fuel delivery pipe that pressure-feeds and supplies the fuel to the injector, the fuel being directly injected into the combustion chamber and burned by spark ignition, the cylinder head cover being made of metal, the injector being disposed directly above the cylinder head cover and the combustion chamber, the fuel delivery pipe being disposed directly above the injector so as to be connected to the injector and fixed to the cylinder head cover. It is characterized by the above.

[0008] In addition, the fuel delivery pipe in the present invention may have a main pipe portion extending in the flow direction of the mainstream of the fuel, and may be configured to be fixed to the cylinder head cover at predetermined positions on both the left and right or top and bottom sides of the main pipe portion centered on the longitudinal direction.

[0009] The fuel delivery pipe in the present invention may be fixed to the cylinder head cover at diagonal brace positions on both the left and right or top and bottom sides centered on the longitudinal direction. Effect of the Invention

[0010] The engine targeted by this invention is, for example, a spark ignition engine, such as a gasoline engine, and is a direct injection engine in which fuel is directly injected into the combustion chamber by an injector. The engine is a so-called center injection direct injection engine in which the injector is disposed almost directly above the combustion chamber of the cylinder head. In the fuel delivery structure of the direct injection engine of this invention, the fuel delivery pipe is disposed almost directly above the injector and connected to the injector. The fuel delivery pipe is attached and fixed to a metal cylinder head cover. Since the metal cylinder head cover has higher strength and rigidity than a resin cylinder head cover, it is possible to eliminate parts such as an injector holder, a cam carrier, or a cam housing that are used together with the resin cylinder head cover. Therefore, even when high strength and rigidity are required in response to an increase in the fuel injection pressure, it is possible to reduce the number of parts compared to the case of using a resin cylinder head cover while appropriately ensuring the strength and rigidity to hold the center injection injector.

[0011] In addition, in the fuel delivery structure of the direct injection engine of the present invention, the fuel delivery pipe as described above is fixed to the cylinder head cover at a plurality of locations on both sides of the center line (main pipe) in the longitudinal direction of the main pipe extending in the fuel flow direction. For example, the fuel delivery pipe is fixed to the cylinder head cover at positions that are symmetrical left and right or up and down with the center line of the main pipe as the axis of symmetry. Alternatively, the fuel delivery pipe is fixed to the cylinder head cover at diagonal brace positions on both left and right or up and down with respect to the center line of the main pipe as described above. Therefore, the fuel delivery pipe takes the form of a so-called double-fixed beam at the support portion with the cylinder head cover, and vibration and displacement of the fuel delivery pipe can be suppressed compared to when the fuel delivery pipe is fixed on only one side (so-called cantilever beam form). As a result, the input of vibration load from the fuel delivery pipe to the injector and the cylinder head cover can be reduced.

[0012] Therefore, according to the fuel delivery structure for a direct injection engine of the present invention, it is possible to appropriately accommodate increased fuel injection pressure and a center injection system while suppressing or reducing costs. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view for explaining the problems with the conventional technology, showing an example of a center-injection type direct-injection engine that employs a resin cylinder head cover and has an injector positioned almost directly above the combustion chamber of the cylinder head. [Diagram 2] FIG. 2 is a diagram for explaining the fuel delivery structure of the direct injection engine of the present invention, and is a perspective view showing the cylinder head of the direct injection engine and a metallic cylinder head cover. [Diagram 3] FIG. 3 is a diagram for explaining the fuel delivery structure of the direct injection engine of the present invention, and is a perspective view showing the basic structure of an injector. [Figure 4] FIG. 4 is a diagram for explaining the fuel delivery structure of the direct injection engine of the present invention, and is a perspective view showing the basic structure of a fuel delivery pipe. [Diagram 5] FIG. 5 is a diagram for explaining the fuel delivery structure of the cylinder injection engine of the present invention, and is a perspective view showing a state in which a fuel delivery pipe is attached to a metal cylinder head cover. [Figure 6] FIG. 6 is a diagram for explaining the fuel delivery structure of the direct injection engine of the present invention, and is a top view showing a state in which a fuel delivery pipe is attached to a metal cylinder head cover. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings. Note that the following embodiment is merely an example of a specific embodiment of the present invention, and is not intended to limit the present invention.

[0015] The direct injection engine in the embodiment of the present invention is typically a spark ignition engine that uses gasoline or other fuels such as LP gas, alcohol, or hydrogen, and in particular is a direct injection (direct injection) engine that directly injects fuel into the combustion chamber. Furthermore, the direct injection engine that is the subject of the embodiment of the present invention is a so-called center injection direct injection engine in which an injector that injects fuel is disposed almost directly above the combustion chamber, as will be described later. And, as shown in Fig. 2, the direct injection engine (hereinafter, engine) 1 in the embodiment of the present invention includes a metallic cylinder head cover 3 that covers the upper surface of a cylinder head 2.

[0016] The cylinder head cover 3 is made of metal, such as an aluminum alloy or a magnesium alloy, and has higher strength and rigidity than the resin cylinder head cover 101 in the direct injection engine 100 shown in Fig. 1. For example, in the example shown in Fig. 2, an aluminum alloy cylinder head cover 3 produced by aluminum die casting is used. As shown in Fig. 2, the cylinder head cover 3 is formed with an injector mounting hole 3a for mounting an injector 4, which will be described later, and a boss 3b for a fastening bolt for fixing a fuel delivery pipe 5, which will be described later.

[0017] The injector mounting holes 3a are through holes formed at predetermined positions on the cylinder head cover 3 corresponding to the positions of the injectors 4 installed directly above the combustion chambers (not shown) formed in the cylinder head 2. In the example shown in Fig. 2, the cylinder head cover 3 is provided with the injector mounting holes 3a at four positions corresponding to the four injectors 4, respectively.

[0018] The fastening bolt boss 3b is a boss-shaped portion for attaching the fuel delivery pipe 5 to the cylinder head cover 3 by fastening a bolt. A screw hole (not shown) for screwing in a fastening bolt (not shown) is formed in the fastening bolt boss 3b.

[0019] Furthermore, the fastening bolt bosses 3b are formed at positions corresponding to the fastening bolt bosses 5c formed on the fuel delivery pipe 5, which will be described later. That is, the fastening bolt bosses 3b of the cylinder head cover 3 are provided at predetermined positions on both the left and right or both the top and bottom sides centered on the longitudinal direction of the main pipe portion 5a of the fuel delivery pipe 5 (the direction in which the fuel flows or is supplied in the fuel delivery pipe 5), as will be described later.

[0020] In addition, the cylinder head cover 3 is formed with an ignition plug arrangement hole 3c for fixing an ignition plug (not shown), and bolt holes 3d for attaching the cylinder head cover 3 to the cylinder head 2 by bolting.

[0021] As described above, the resin cylinder head cover 101 as shown in FIG. 1 contributes to weight reduction and sound insulation of the direct injection engine 100. However, the resin cylinder head cover 101 is disadvantageous in terms of strength and rigidity compared to a metal cylinder head cover. In the direct injection engine 100, for example, in order to cope with high fuel injection pressure, the cylinder head cover 101 is required to have high strength and rigidity compared to a conventional port injection type engine. In addition, by adopting the above-mentioned center injection method, the space for arranging the injector 105 on the cylinder head cover 101 is reduced, and as a result, the strength margin of the cylinder head cover 101 is also reduced. Therefore, in the direct injection engine 100 employing the resin cylinder head cover 101, the injector holder 104 and the cam carrier 102 are used to compensate for the strength and rigidity of the resin cylinder head cover 101, which results in an increase in the number of parts, which is a factor in increasing costs.

[0022] In contrast, in the engine 1 according to the embodiment of the present invention, by adopting a metal cylinder head cover 3 having high strength and rigidity, it is possible to eliminate parts such as the injector holder 104 and the cam carrier 102, compared to the resin cylinder head cover 101 shown in Fig. 1. Therefore, it is possible to appropriately ensure the strength and rigidity of the cylinder head cover 3 even when dealing with higher fuel injection pressures and the special structure of the center injection system. Also, it is possible to reduce the number of parts and achieve cost reduction, compared to the direct injection engine 100 adopting the resin cylinder head cover 101 as shown in Fig. 1.

[0023] The fuel delivery structure of the cylinder injection engine in the embodiment of the present invention includes an injector 4 and a fuel delivery pipe 5, as shown in FIGS.

[0024] The injector 4 is a component that injects fuel into the combustion chamber of the cylinder head 2. As described above, the engine 1 in the embodiment of the present invention is a direct injection engine with a center injection system. Therefore, the injector 4 is disposed directly above (directly above in the vertical direction) the cylinder head cover 3 and the combustion chamber in the cylinder head 2.

[0025] As shown in Fig. 3, the injector 4 basically has the same configuration as a conventional "center injection type injector." That is, the injector 4 has a main body (nozzle holder) 4a that is substantially straight, and an injector mounting portion 5b of a fuel delivery pipe 5 (described later) is connected to its upper end 4b, through which high-pressure fuel is supplied from the fuel delivery pipe 5. The injector 4 has a valve mechanism (not shown) formed inside the main body 4a, including a solenoid (not shown) and a plunger (not shown). An injection nozzle portion 4c that injects fuel directly into the combustion chamber of the cylinder head 2 is formed at the tip (lower end) of the main body 4a.

[0026] In the example shown in Fig. 3, the injector 4 is equipped with a nozzle holder clamp 4d. The nozzle holder clamp 4d clamps and connects the upper end 4b of the injector 4 to the injector mounting portion 5b of the fuel delivery pipe 5. The nozzle holder clamp 4d is also configured to press the injector 4 toward the cylinder head 2 by the elastic force of a spring (not shown). For this reason, for example, when the engine 1 is started, when the fuel injection pressure is relatively low, the movement of the injector 4 due to the combustion pressure can be suppressed, and the airtightness between the injector 4 and the cylinder head 2 can be improved. In addition, the vibration and noise caused by the movement of the injector 4 can be reduced.

[0027] The fuel delivery pipe 5 pressure-feeds high-pressure fuel discharged from a fuel pump (not shown) to the injectors 4. In the example shown in Fig. 4, an injector 4 is installed in each of four injector mounting holes 3a formed in the cylinder head cover 3, and the fuel delivery pipe 5 distributes and supplies fuel to the four injectors 4.

[0028] 4, the fuel delivery pipe 5 basically has the same structure as a conventional "fuel delivery pipe for a direct injection engine." That is, it has a main pipe section 5a having a straight pipe shape with a predetermined length according to the number of injectors 4 that supply fuel, and an injector attachment section 5b.

[0029] The main pipe section 5a is a tubular member that is connected to the fuel pump and extends in the direction of flow of the main flow of the fuel discharged from the fuel pump. Therefore, the length direction of the main pipe section 5a corresponds to the flow direction (or supply direction) DL of the main flow of the fuel in the fuel delivery pipe 5.

[0030] The injector attachment portion 5b is a boss-shaped portion branched off from the main pipe portion 5a, and is used to connect and attach the injector 4. As described above, the upper end portion 4b of the injector 4 is attached to the injector attachment portion 5b using the nozzle holder clamp 4d.

[0031] In the example shown in Fig. 4, the fuel pressure sensor 6 is attached near the center in the longitudinal direction of the main pipe section 5a of the fuel delivery pipe 5. The fuel pressure sensor 6 detects the pressure of the high-pressure fuel injected from the injector 4. In the example shown in Fig. 6, which will be described later, the fuel pressure sensor 6 is attached near the tip end (the end on the right side in Fig. 6) in the longitudinal direction of the main pipe section 5a of the fuel delivery pipe 5.

[0032] Furthermore, the fuel delivery pipe 5 in this embodiment of the present invention is disposed so as to be connected to the upper end 4b of the injector 4 directly above (directly above in the vertical direction) the injector 4. In this state, the fuel delivery pipe 5 is fixed to the metallic cylinder head cover 3.

[0033] In order to fix the fuel delivery pipe 5 to the cylinder head cover 3 as described above, a fastening bolt boss 5c is formed in the fuel delivery pipe 5. The fastening bolt boss 5c is a boss-shaped portion for attaching the fuel delivery pipe 5 to the cylinder head cover 3 by fastening with a bolt. As shown in Figures 4 and 5, the fastening bolt boss 5c is formed with a bolt hole (through hole) 5d for inserting the fastening bolt 7.

[0034] The fastening bolt bosses 5c are provided in the longitudinal direction of the main pipe portion 5a of the fuel delivery pipe 5, that is, at predetermined positions on both the left and right or the top and bottom sides centered on the fuel flow direction (or fuel supply direction) DL in the fuel delivery pipe 5 as shown in Figs. 4, 5, and 6. In the fuel delivery structure of the direct injection engine according to the embodiment of the present invention, for example, the fastening bolt bosses 5c are formed at positions symmetrical on the left and right or the top and bottom sides with the fuel flow direction DL in the fuel delivery pipe 5 as the axis of symmetry. In the example shown in Fig. 6, the fastening bolt bosses 5c are formed at the positions of the diagonal braces on both the top and bottom sides centered on the fuel flow direction DL in the fuel delivery pipe 5. In other words, the fuel delivery pipe 5 is fixed to the cylinder head cover 3 at the positions of the diagonal braces on both the left and right or the top and bottom sides centered on the center line (i.e., the flow direction DL) in the longitudinal direction of the main pipe portion 5a.

[0035] Therefore, the fuel delivery pipe 5 has a so-called double-sided fixed beam configuration at the support portion with the cylinder head cover 3, which can suppress vibration and displacement of the fuel delivery pipe 5 compared to the conventional case where the fuel delivery pipe 5 is fixed only on one side (so-called cantilever configuration), and thus can reduce the input of vibration load from the fuel delivery pipe 5 to the injector 4 and the cylinder head cover 3.

[0036] As described above, in the fuel delivery structure for a direct injection engine in the embodiment of the present invention, the fuel delivery pipe 5 is arranged almost directly above the injector 4 and connected to the injector 4 for a so-called center injection type direct injection engine 1. The fuel delivery pipe 5 is attached and fixed to the metal cylinder head cover 3. The metal cylinder head cover 3 has higher strength and rigidity than the "resin cylinder head cover" shown as the prior art. Therefore, for example, parts such as the "injector holder", the "cam carrier" or the "cam housing" adopted together with the "resin cylinder head cover" can be eliminated. Therefore, for example, even when high strength and rigidity are required in response to the increase in fuel injection pressure, the number of parts can be reduced compared to the case where the "resin cylinder head cover" is adopted while appropriately ensuring the strength and rigidity for holding the center injection type injector 4.

[0037] Therefore, according to the fuel delivery structure for a direct injection engine in the embodiment of the present invention, it is possible to appropriately accommodate increased fuel injection pressure and center injection methods while suppressing or reducing costs. [Explanation of symbols]

[0038] 1. Direct injection engine (center injection type direct injection engine) 2. Cylinder head 3 Cylinder head cover 3a Injector arrangement hole (formed in the cylinder head cover) 3b Boss for fastening bolt (formed on cylinder head cover) 3c Spark plug hole (formed in the cylinder head cover) 3d Bolt holes (formed in the cylinder head cover) 4 Injectors 4a (Injector) Body (Nozzle Holder) 4b (Top end of injector) 4c (injector) nozzle 4d (Injector) Nozzle Holder Clamp 5 Fuel delivery pipe 5a (Fuel delivery pipe) main section 5b Injector mounting part (of fuel delivery pipe) 5c (Fuel delivery pipe) Boss for fastening bolt 5d (Fuel delivery pipe) bolt hole (through hole) 6. Fuel Pressure Sensor 7 Fastening bolts 100 [Prior Art] (Center Injection Type) Direct Injection Engine 101 [Prior Art] Plastic cylinder head cover 102 [Prior Art] Cam carrier (or cam housing) 103 [Prior Art] Cylinder Head 104 [Prior Art] Injector Holder 105 [Prior Art] Injector 106 [Prior Art] Fuel delivery pipe 107 [Prior Art] Fuel Pump DL Fuel flow direction (supply direction)

Claims

1. A fuel delivery structure for a cylinder injection engine comprising: a cylinder head; a cylinder head cover attached to the cylinder head and covering an upper surface of the cylinder head; an injector for injecting fuel into a combustion chamber of the cylinder head; and a fuel delivery pipe for supplying the fuel to the injector by pressure transfer, the fuel being directly injected into the combustion chamber and burned by spark ignition, The cylinder head cover is made of metal. The injector is disposed directly above the cylinder head cover and the combustion chamber, The fuel delivery pipe is disposed so as to be connected to the injector directly above the injector and is fixed to the cylinder head cover. A fuel delivery structure for a direct injection engine.

2. 2. A fuel delivery structure for a cylinder injection engine according to claim 1, The fuel delivery pipe is The fuel supply pipe has a main pipe portion extending in a direction of flow of the fuel, The main pipe portion is fixed to the cylinder head cover at predetermined positions on both sides of the main pipe portion in the longitudinal direction. A fuel delivery structure for a direct injection engine.

3. 3. A fuel delivery structure for a cylinder injection engine according to claim 2, The fuel delivery pipe is fixed to the cylinder head cover at the positions of the braces on both sides of the longitudinal direction. A fuel delivery structure for a direct injection engine.

Images