JPH0380975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a device that adjusts fuel injection timing according to engine rotation speed.

<<Prior Art>> Generally, in a compression ignition engine, there is an ignition delay period from when fuel is injected until it ignites, so it is necessary to adjust the fuel injection timing according to increases and decreases in the rotational speed of the engine.

As an advance device for the injection timing in the fuel injection system, a push rod that connects the rocker arm that operates the plunger of the unit injector and the fuel injection cam is brought into contact with a cam follower composed of a swinging arm, and By positioning the cam roller so that the fuel injection cam is in contact with the cam roller, pivoting the swinging arm to the eccentric shaft, and controlling the rotation of the eccentric shaft using the advance drive device, the swinging arm is connected to the fuel injection cam. The injection timing is adjusted by moving forward and backward in the tangential direction of the
49-70031).

<<Problems to be Solved by the Invention>> However, in this advance angle device, the cam follower is composed of a swinging arm, and the swinging arm is pivotally supported on the eccentric shaft. The amount of movement changes sinusoidally, making it impossible to control the advance angle uniformly, resulting in errors.

In addition, since this model uses a tangential cam as the fuel injection cam, the push rod moves up and down continuously and smoothly, resulting in a gentle pressure increase curve within the unit injector, from the start to the end of fuel injection. There were problems in that it took a long time to complete the process and the ejection pressure could not be maintained high.

<Means for Solving the Problems> In the present invention, the fuel injection cam is provided with a cam nose so that a pressure increase change occurs rapidly within the fuel injection pump. The arranged tappet part is moved linearly by an advance angle drive device consisting of a single-acting hydraulic cylinder, and the impact force generated by using a cam nose for the fuel injection cam acts as a disturbance element on the hydraulic cylinder. This is prevented by interposing an excessive flow rate limiting means in the buffer communication path that communicates the pressure oil chamber in the hydraulic cylinder with the double-return spring storage chamber, thereby controlling the fuel injection timing with high precision. This is characterized in that it performs advance angle control and injects fuel at high pressure into the combustion chamber.

<<Operation>> In the present invention, since the fuel injection cam is provided with a cam nose, the plunger of the fuel injection pump can be rapidly pressed. As a result, a certain amount of fuel can be jetted out in a short time, and the jetting force can be increased, so that good atomization can be achieved and the flame propagation speed can be increased.

Further, the tappet disposed between the fuel injection cam and the fuel injection pump is moved linearly by an advance angle drive device consisting of a hydraulic cylinder, and the pressure oil chamber of the hydraulic cylinder and the spring housing chamber are communicated with each other. Since the buffer communication passage is provided with an excessive flow rate limiting means consisting of a check valve, a passage with a narrow cross-sectional area, etc., the inconveniences caused by using a cam nose for the fuel injection cam, i.e., the tappet and fuel injection cam, are reduced. Even if the impact force generated by the contact with the hydraulic cylinder is transmitted to the hydraulic cylinder, the outflow of the pressure oil from the pressure oil chamber is restricted by the excessive flow rate limiting means, so the pressure oil in the pressure oil chamber becomes a cushion. It becomes possible to accurately hold the tappet in a position corresponding to the engine speed.

<<Example>> FIG. 1 is a longitudinal sectional front view of the main parts of a vertical overhead valve type diesel engine, and FIG. 2 is a schematic configuration diagram of the engine.

Diesel engine E has cylinder block 1
A piston 3 is fitted into a cylinder 2 formed in a cylinder 2 so as to be movable up and down, and a valve drive camshaft 4 interlocked with a crankshaft (not shown) is mounted on both sides of the cylinder 2 in the front-rear direction. An intake valve 5 is attached to one valve drive camshaft 4a.
A valve train cam for controlling the opening and closing of the exhaust valve 8 and a fuel injection cam 7 for driving the unit injector 6 are fixed, and a valve train cam for controlling the opening and closing of the exhaust valve 8 is fixed on the other valve train camshaft 4b. It is fixed.

On the top surface of cylinder block 9 of engine E,
An intake valve rocker arm shaft 10 and an exhaust valve rocker arm shaft 11 are fixed, and an intake valve rocker arm 12 and a unit injector drive rocker arm 13 are swingably supported on the intake valve rocker arm shaft 10. An exhaust valve rocker arm 14 is swingably supported on the exhaust valve rocker arm shaft 11.

Locker arm 13 for unit injector drive
is connected to the fuel injection cam 7 via a push rod 15, and a tappet 16 is provided at the base end of the push rod 15.

As shown in FIG. 1, the fuel injection cam 7 has a semi-cylindrical cam nose 17 fixed on its circumferential surface along the cam axis.
The push rod 1 is brought into contact with the tappet roller 18 fixed to the lower end of the tappet 16.
5 is pushed up and the plunger 19 of the unit injector 6 is pressed by the rocker arm 13 to inject fuel into the combustion chamber.

The tappet 16 is configured to be linearly movable in the direction of the circumferential surface of the fuel injection cam 7 by an advance angle drive device D.

The advance angle drive device D includes a transmission member 20 to which the tappet 16 is fitted and fixed, a single-acting hydraulic cylinder 21 operated by lubricating oil pressure of the engine, a piston rod 22 of the hydraulic cylinder 21, and the transmission member 2.
The transmission member 20 and the piston rod 22 are each provided with racks 24 and 25 on their circumferential surfaces. A pinion 26 that meshes with the hydraulic cylinder 21 is formed.
The amount of movement of the piston rod 22 into the movement of the piston rod 22 is converted into the amount of movement of the transmission member 20 via the intermediate member 23, and the cam nose 17 of the fuel injection cam 7 and the tappet roller 18 of the tappet 16 are connected to each other.
The fuel injection timing is adjusted by changing the contact position with the cylinder.

The intermediate transmission member 23 also serves as a transmission shaft to the retardation device of the valve mechanism.

A return spring 27 is disposed in the hydraulic cylinder 21 so as to surround the piston rod 22, and the return spring 27 urges the piston 28 to move back and forth. A pressure oil chamber 31 is formed by separating it from the spring storage chamber 30 by the head 29 of the piston 28, and the pressure oil chamber 31 and the spring storage chamber 30 are communicated with each other through a buffer communication path 32. Excess flow rate limiting means C consisting of a check valve 33 is arranged to prevent pressure oil from flowing from the pressure oil chamber 31 into the spring housing chamber 30 side. In addition, a lubricating oil pump 3 is provided in the spring housing chamber 30.
A lubricating oil passage 35 communicating with the buffer 4 is open, and pressure oil is supplied to the pressure oil chamber 31 through the buffer communication passage 32. In addition, piston head 2
The pressure receiving area S on the pressure oil chamber 31 side of the piston rod 9 is formed to be larger than the cross-sectional area A of the piston rod 22.

In the above fuel injection timing adjustment device, when the engine speed is below a certain value, the spring force of the return spring 27 is stronger than the lubricating oil pressure acting on the pressure oil chamber 31, so the piston 28 is positioned on the retraction side. ing. Therefore, the transmission member 20 is in a state of being advanced toward the cylinder side. When the rotational speed of the engine increases, the hydraulic pressure in the pressure oil chamber 31 increases accordingly, and the spring force of the return spring 27 and the hydraulic pressure are balanced, and the moving force is transmitted through the intermediate transmission member 23. is transmitted to the transmission member 20, and the transmission member moves to the left in the figure. As a result, the tappet 16 also moves to the left in the figure, and the cam nose 17 of the fuel injection cam 7 and the tappet roller 18 of the tappet 16 come into contact with each other at a position slightly above the normal contact position in the direction of rotation of the fuel injection cam 7. , the fuel injection timing becomes earlier.

Since the cam lift amount by the fuel injection cam 7 is obtained by the cam nose 17, an impact force is generated to move the tappet 16 to the right in the figure when the cam nose 17 and the tappet roller 18 come into contact. The impact force is transmitted by the transmission member 20.
The signal is transmitted to the piston 28 of the advance angle drive device D via the intermediate member 23, and the piston 28 attempts to move back and forth. Since the flow rate restriction means C is provided, even if force is applied to the pressure oil chamber 31 from the piston 28 side, the pressure oil in the pressure oil chamber 31 cannot escape quickly, so it acts as a hydraulic cushion. The amount of piston advancement is kept constant and there is no disturbance in fuel injection timing.

Furthermore, since the hydraulic cylinder 21 is used to advance the fuel injection timing, its piston stroke is small, and since the pressure receiving area S of the piston head 29 is larger than the cross-sectional area of the piston rod 22, the pressure is transmitted through the piston rod 22. The impact pressure caused by this decreases, and the displacement of the piston due to compression of the pressure oil becomes negligible.

In addition, as the excessive flow rate limiting means C, an orifice interposed in the middle of the buffer communication passage 32,
It may be a communication groove provided between the piston head 29 and the inner surface of the cylinder, or a passage with a narrow cross-sectional area such as an outer peripheral gap of the piston head 29.

Further, in the above embodiment, the pressure oil is supplied to the pressure oil chamber 31 through the spring housing chamber 30, but the pressure oil supply path to the pressure oil chamber 31 is connected to the hydraulic cylinder 2.
It may be formed on the wall surface of 1 so that pressure oil can be directly supplied to the pressure oil chamber 31.

≪Effects of the Invention≫ In the present invention, the fuel injection cam is provided with a cam nose so that a pressure increase change occurs rapidly within the fuel injection pump, so the operating speed of the plunger of the fuel injection pump becomes faster and of fuel can be ejected in a short period of time. As a result, the ejection force becomes stronger and atomization can be performed well, and the flame propagation speed can be increased.

In addition, since the tappet located between the fuel injection pump and the fuel injection cam is moved linearly by an advance angle drive device consisting of a hydraulic cylinder, the engine rotation speed and the amount of movement of the advance angle device are controlled. Correspondence can be made accurately and easily, and high advance angle control precision can be obtained.

Furthermore, an excessive flow rate limiting means consisting of a check valve or a passage with a narrow cross-sectional area is provided in the buffer communication passage that communicates the pressure oil chamber of the hydraulic cylinder of the advance angle drive device with the return spring storage chamber. Even if the impact force generated by the contact between the tappet and the fuel injection cam is transmitted to the hydraulic cylinder, the excess flow rate limiting means restricts the flow of pressure oil from the pressure oil chamber. acts as a cushion, allowing the tapepet to be held accurately in a position corresponding to the engine speed. This also allows advance angle control to be performed with high precision.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a vertical sectional view of the main part of a vertical overhead valve type diesel engine,
The figure is a schematic configuration diagram of the engine. 7... Fuel injection cam, 16... Tappet, 17
...Cam nose, 18...Tapetsu roller, 21
... Hydraulic cylinder, 22 ... Piston rod, 2
7... Return spring, 29... Piston head, 30
... Spring storage chamber, 31 ... Pressure oil chamber, 32 ... Buffer communication passage, 33 ... Check valve, D ... Advance angle drive device, C ... Excess flow rate limiting means, S ... Pressure receiving of 29 Area, A...cross-sectional area of 22.

Claims (1)

[Claims] 1. The plunger 19 of the fuel injection pump is interlocked and connected to the fuel injection cam 7 via the tappet 16, and the contact point between the tappet 16 and the fuel injection cam 7 is changed as the engine speed increases. In this engine fuel injection timing adjustment device, a tappet roller 18 is disposed on the tappet 16, a cam nose 17 is formed on the fuel injection cam 7, and the tappet 16 is advanced. The device D is configured to be able to move forward and backward in the direction along the circumferential surface of the fuel injection cam 7, and the advance angle drive device D is moved forward and backward by a single-acting hydraulic cylinder 21 that is operated by hydraulic pressure generated according to the engine rotation speed. A return spring 27 configured as shown in FIG.
A buffer communication passage 32 connects the accommodation chamber 30 and the pressure oil chamber 31.
An excessive flow rate limiting means C is provided in this buffer communication passage 32, and the pressure receiving area S of the piston head 29 in the pressure oil chamber 31 is formed to be larger than the cross sectional area A of the piston rod 22. Hydraulic fuel injection timing adjustment device for engines. 2. The hydraulic fuel injection timing adjustment device for an engine according to claim 1, wherein the excessive flow rate limiting means C is a check valve 33. 3. The fuel injection timing adjustment device according to claim 1, wherein the excessive flow rate limiting means C is a passage having a narrow cross-sectional area.