V-type eight-cylinder engine

Abstract

To provide a V-type eight-cylinder engine capable of suppressing lateral vibration of 1.5-order rotation without disturbing engine balancing design.SOLUTION: The V-type eight-cylinder engine includes eight cylinders arranged separately on left and right banks LB, RB, and the cylinders of each bank LB, RB are fired at unequal intervals. In the V-type eight-cylinder engine, left and right fuel pumps 9L, 9R provided on the left and right banks LB, RB are installed at an angle θp wider than an angle between engine valves arranged on both sides of the left and right banks LB, RB.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a V8 engine. [Background technology]

[0002] Conventionally, there are known inventions relating to balancer structures for V-type engines (for example, Patent Document 1 below). The balancer structure for a V-type engine described in Patent Document 1 has a configuration in which a balancer shaft is journaled and supported in parallel with the crankshaft of the V-type engine.

[0003] By rotating in the opposite direction to the crankshaft but at the same speed, the balancer shaft can cancel the inertial couple that causes vibration in a 60-degree V8 engine, thereby reducing vibration and noise. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-042230 Summary of the Invention [Problem to be solved by the invention]

[0005] In a V8 engine, the crossplane crankshaft causes unequal firing intervals between the left and right banks, resulting in 1.5th order left-right vibrations, which cause vehicle body vibration and idle vibration. However, changing the geometry of the existing engine, or the arrangement and operating order of the valve train as a countermeasure, can disrupt the engine balancing design.

[0006] The present disclosure provides a V8 engine that can suppress 1.5th order left-right vibrations of rotation without disrupting the engine balancing design. [Means for solving the problem]

[0007] One aspect of the present disclosure provides a V8 engine in which eight cylinders are arranged in left and right banks and the cylinders in each bank are ignited at unequal intervals, and left and right fuel pumps provided in the left and right banks are installed at a wider angle than engine valves arranged on both sides of the left and right banks. [Effects of the Invention]

[0008] According to the above-described aspects of the present disclosure, it is possible to provide a V8 engine that can suppress 1.5th order left-right vibrations of rotation without disturbing the engine balancing design. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram showing an embodiment of a V8 engine according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing the fuel supply system of the V8 engine in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the invention will be described with reference to the drawings.

[0011] FIG. 1 is a schematic diagram of a V8 engine 1 according to the present disclosure. The V8 engine 1 of this embodiment is a vehicle engine that is installed in, for example, an automobile. The V8 engine 1 has a left bank LB and a right bank RB, with eight cylinders 2 arranged in the left and right banks LB and RB, and the cylinders 2 in each of the banks LB and RB are ignited at unequal intervals. In the illustrated example, the bank angle, which is the angle between the left and right banks LB and RB, is 90°, but the bank angle is not limited to 90° and may be, for example, 60°.

[0012] The V8 engine 1 includes, for example, a cylinder block CB in which each cylinder 2 is formed, pistons 3 provided in each cylinder 2 so as to be able to reciprocate, a crankshaft 4 provided at the bottom of the V8 engine 1, and a connecting rod 5. One end and the other end of the connecting rod 5 are connected to the pistons 3 and the crankshaft 4, respectively, and the connecting rod 5 converts the reciprocating motion of the pistons 3 into the rotational motion of the crankshaft 4.

[0013] The V8 engine 1 also includes a cylinder head CH disposed on top of the cylinder block CB, engine valves 6 provided in each cylinder 2, left and right intake camshafts 7L, 7R, and left and right exhaust camshafts 8L, 8R. A combustion chamber CC is formed in the space within the cylinder 2 between the bottom surface of the cylinder head CH and the upper end surface of the piston 3.

[0014] The cylinder head CH is provided with an intake port IP and an exhaust port EP that communicate with the combustion chamber CC in each cylinder 2. Air from outside the V8 engine 1 is introduced into the combustion chamber CC through the intake port IP, and exhaust gas generated in the combustion chamber CC is discharged to the outside of the V8 engine 1 through the exhaust port EP.

[0015] The engine valves 6 include, for example, intake valves 6i that open and close intake ports IP and exhaust valves 6e that open and close exhaust ports EP. In the illustrated example, the exhaust valves 6e are arranged inside the left and right banks LB and RB, and the intake valves 6i are arranged outside the left and right banks LB and RB. Note that the exhaust port EP and the exhaust valves 6e, and the intake port IP and the intake valves 6i may be arranged inversely to those in the illustrated example.

[0016] The engine valves 6, such as the intake valves 6i, arranged on both sides of the left and right banks LB and RB, are arranged at an angle θv that is wider than the bank angle of the left and right banks LB and RB. Each engine valve 6 has a valve spring 61 that biases the engine valve 6 in a valve closing direction, and a rocker arm 62.

[0017] The left and right intake camshafts 7L, 7R each have a valve cam 71 and are rotatably supported adjacent to the rocker arms 62 of the left and right intake valves 6i. Similarly, the left and right exhaust camshafts 8L, 8R each have a valve cam 81 and are rotatably supported adjacent to the rocker arms 62 of the left and right exhaust valves 6e. The left and right intake camshafts 7L, 7R and the left and right exhaust camshafts 8L, 8R are rotated by power transmitted from the crankshaft 4 via timing belts (not shown).

[0018] Rotation of the left and right intake camshafts 7L, 7R rotates the valve cam 71, which presses the rocker arm 62 of the intake valve 6i at a predetermined timing. As a result, the intake valve 6i reciprocates, repeatedly opening against the biasing force of the valve spring 61 and closing due to the biasing force of the valve spring 61 at a predetermined cycle.

[0019] Furthermore, as the left and right exhaust camshafts 8L, 8R rotate, the valve cam 81 rotates and presses the rocker arm 62 of the exhaust valve 6e at a predetermined timing. As a result, the exhaust valve 6e performs reciprocating motion, repeatedly opening against the biasing force of the valve spring 61 and closing due to the biasing force of the valve spring 61 at a predetermined cycle.

[0020] Fig. 2 is a schematic diagram showing the fuel supply system of the V8 engine 1 of Fig. 1. The fuel supply system of the V8 engine 1 includes, for example, a fuel tank T, a supply passage S, a feed pump P, a filter F, left and right fuel pumps 9L, 9R, and left and right fuel injection devices 10L, 10R.

[0021] The fuel tank T stores fuel such as gasoline, diesel, ethanol, etc. A supply passage S connects the fuel tank T to the suction ports 9s of the left and right fuel pumps 9L, 9R, for example. A feed pump P is provided in the supply passage S and pumps the fuel stored in the fuel tank T through the supply passage S to the suction ports 9s of the left and right fuel pumps 9L, 9R. A filter F is provided in the supply passage S and removes foreign matter from the fuel as it passes through.

[0022] The left and right fuel pumps 9L and 9R are provided in the left bank LB and the right bank RB, respectively. Each of the fuel pumps 9L and 9R includes, for example, a cylinder 91, a plunger 92, a spring 93, an electromagnetic spill valve 94, and an electromagnetic solenoid 95.

[0023] The cylinder 91 accommodates a plunger 92 so that the plunger 92 can reciprocate. The cylinder 91, together with the plunger 92 and an electromagnetic spill valve 94, forms a pressurization chamber PC that pressurizes the fuel. For example, one end of the plunger 92 is accommodated in the cylinder 91, and the other end abuts against pump cams 82 provided on the left and right exhaust camshafts 8L, 8R. The pump cam 82 has, for example, a triangular shape with rounded corners.

[0024] A spring 93 biases the plunger 92 toward the pump cam 82. The electromagnetic spill valve 94 is provided so as to be capable of reciprocating motion so as to open and close the space between the fuel suction port 9s and the pressurization chamber PC. An electromagnetic solenoid 95 reciprocates the electromagnetic spill valve 94 when a voltage is applied thereto.

[0025] When the exhaust camshafts 8L, 8R of each fuel pump 9L, 9R rotate and the pump cam 82 rotates, the plunger 92 is pushed into the cylinder 91 against the biasing force of the spring 93, and the volume of the pressurization chamber PC decreases. At this time, by closing the electromagnetic spill valve 94 at a predetermined timing, each fuel pump 9L, 9R can pressurize the fuel to a predetermined pressure.

[0026] Furthermore, when the exhaust camshafts 8L, 8R of the fuel pumps 9L, 9R rotate and the pump cam 82 rotates further, the plunger 92 is pushed toward the pump cam 82 by the biasing force of the spring 93, and the volume of the pressurization chamber PC increases. At this time, by opening the electromagnetic spill valve 94, the fuel pumps 9L, 9R can introduce fuel into the pressurization chamber PC.

[0027] As described above, in the fuel pumping process in which each fuel pump 9L, 9R repeatedly introduces and pressurizes fuel into the pressurization chamber PC, the plunger 92 reciprocates at a predetermined cycle along the central axis in accordance with the rotation of the pump cam 82. As a result, pressurized fuel is discharged from the discharge ports of the left and right fuel pumps 9L, 9R to the left and right fuel injectors 10L, 10R.

[0028] In the V8 engine 1 of this embodiment, the left and right fuel pumps 9L, 9R provided in the left and right banks LB, RB are installed at a wider angle θp than the engine valves 6 arranged on both sides of the left and right banks LB, RB.

[0029] Specifically, as shown in Fig. 1, the engine valves 6 arranged on both sides of the left and right banks LB and RB are left and right intake valves 6i that are installed at an angle θv that is wider than the bank angle. In contrast, the angle θp of the left and right fuel pumps 9L and 9R, that is, the angle θp between the central axes of the plungers 92 that constitute the left and right fuel pumps 9L and 9R shown in Fig. 2, is wider than the angle θv between the central axes of the intake valves 6i provided on both sides of the left and right banks LB and RB shown in Fig. 1, and is arranged closer to horizontal (180°).

[0030] Each fuel injection device 10L, 10R includes, for example, a delivery pipe 11 provided in the cylinder head CH and a fuel injection valve 12 that injects fuel into the combustion chamber CC. The delivery pipe 11 supplies high-pressure fuel pumped from each fuel pump 9L, 9R to the fuel injection valve 12. The fuel injection valve 12 opens when energized and injects high-pressure fuel into the combustion chamber CC. The cylinder head CH also includes an ignition plug 21 that ignites a mixture of fuel injected from the fuel injection valve 12 into the combustion chamber CC and air drawn into the combustion chamber CC from the intake port IP.

[0031] The fuel supply system of the V8 engine 1 is controlled by a controller C, which is an electronic control unit (ECU). Based on detection signals from various sensors that detect the operating state of the V8 engine 1, the controller C controls the electromagnetic solenoids 95 of the left and right fuel pumps 9L, 9R, and the fuel injection valves 12 and spark plugs 21 of each cylinder 2. In this way, the controller C supplies an amount of fuel according to the operating state to the combustion chamber CC and controls the combustion timing of the air-fuel mixture in the combustion chamber CC.

[0032] In conventional V8 engines, 1.5th order rotational vibrations occur due to unequal firing intervals in each cylinder on the left and right banks. Specifically, in V8 engines that use a crossplane crankshaft, the unequal firing intervals in each cylinder on the left and right banks cause the horizontal components of the opening and closing motion of the engine valves on the left and right banks to reinforce each other rather than cancel each other out. As a result, 1.5th order rotational unbalance remains in the engine body.

[0033] When a V8 engine is mounted on a vehicle, the 1.5th order left-right vibrations overlap with the unit's suspension resonance and power plant resonance, inducing vehicle body vibration. As a result, in order to avoid vibrations, restrictions arise such as changing the idle speed setting in order to change the frequency of the unit's vibration source.

[0034] In contrast, the V8 engine 1 of this embodiment is a V8 engine in which eight cylinders 2 are arranged in left and right banks LB and RB, and the cylinders 2 of each bank LB, RB are ignited at unequal intervals. In the V8 engine 1 of this embodiment, the left and right fuel pumps 9L, 9R provided in the left and right banks LB, RB are installed at an angle θp wider than the engine valves 6 arranged on both sides of the left and right banks LB, RB.

[0035] With this configuration, in the V8 engine 1 of this embodiment, the plungers 92 of the left and right fuel pumps 9L, 9R reciprocate so as to cancel out 1.5th-order rotational lateral vibrations. In other words, the phases of the plungers 92 of the left and right fuel pumps 9L, 9R can be made to have an anti-phase relationship so as to cancel out the 1.5th-order rotational component of the lateral inertial force caused by the opening and closing movement of the valve train, such as the engine valves 6. As a result, the 1.5th-order rotational lateral vibrations of the V8 engine 1 are canceled out and reduced by the reciprocating motion of the plungers 92 of the left and right fuel pumps 9L, 9R.

[0036] More specifically, by using a pump cam 82 with a three-lobe structure that rotates 0.5 times per rotation of the crankshaft 4, it is possible to generate a 1.5-order reciprocating motion in the plungers 92 of the left and right fuel pumps 9L, 9R that offsets the 1.5-order lateral vibrations. Furthermore, in order to obtain an offsetting force by the reciprocating motion of the plungers 92 with respect to the phase of the lateral unbalanced force that oscillates periodically with the opening and closing timing of the valve train such as the engine valves 6, the phase of the lift curve of the plungers 92 can be controlled by setting the lobe phase (shape) of the pump cam 82 to a design target value. Furthermore, it is possible to adjust the generated inertial force by adjusting the mass and stroke of the plungers 92, etc.

[0037] Therefore, according to this embodiment, it is possible to provide a V8 engine 1 that can suppress 1.5th order left and right vibrations of rotation without disturbing the engine balancing design.

[0038] The preferred embodiments of the present invention have been described above in detail. However, the present invention is not limited to the above-described embodiments. Various modifications or substitutions may be applied to the above-described embodiments without departing from the scope of the present invention. [Explanation of symbols]

[0039] 1 V8 engine 2-cylinder LB Left bank (bank) RB Right Bank (Bank) 6 Engine Valves 9L fuel pump 9R fuel pump θp angle θv angle

Claims

[Claim 1] A V8 engine in which eight cylinders are arranged in left and right banks and the cylinders in each bank are ignited at unequal intervals, The left and right fuel pumps provided in the left and right banks are installed at a wider angle than the engine valves arranged on both sides of the left and right banks. V8 engine.

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