JPH09177635A - Driving mechanism for unit injector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To independently control an oil feed rate and injection timing of an unit injector, and thereby enhance engine performance. SOLUTION: When an eccentric member 16 is rotated, a rocker arm 15 for an unit injector, which is rotatably supported by a rocker shaft 6, is moved between an unit injector driving cam and an unit injector 12, and an abutting position with the cam is thereby displaced. By this constitution, the aforesaid displacement is identical to the case that the rotational angle of the cam is changed in phase. The rocker arm 15 for the unit injector drives the unit injector 12 by way of a swing arm 18. This constitution thereby allows drive timing for the unit injector 12 to be changed, and an oil feed rate is thereby changed. Injection timing by the unit injector 12 is electronically controlled by a built-in electromagnetic actuator. As mentioned above, the oil feed rate and injection timing of the unit injector 12 are independently controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive mechanism for a unit injector that directly injects fuel into a combustion chamber of an engine.

[0002]

2. Description of the Related Art As a fuel injection device for injecting fuel directly into a combustion chamber of an engine, a fuel injection pump and an injector are integrally formed, and a high-pressure fuel is directly injected into a combustion chamber of the engine by a plunger and incorporated therein. There is an electronically controlled jerk type unit injector in which a fuel injection start timing and a fuel injection end timing (injection timing) are controlled by an electromagnetic actuator (electromagnetic valve). This jerk-type unit injector is easier to achieve high-pressure injection as compared with a row-type injection pump, and has high performance and high basic ability with respect to exhaust gas.

As shown in FIGS. 6 and 7, the driving mechanism of the jerk type unit injector sucks a cam shaft 2 rotatably supported on a cylinder head 1 of an engine and exhaust cams 3 and 4 for driving an exhaust valve. The unit injector driving cam 5 is integrally formed, while the rocker shaft 6 is configured to suck and exhaust the rocker arms 7 and 8 for the exhaust valve and the rocker arm 9 for the unit injector so as to be swingable. When the camshaft 2 rotates, the rocker arms 7 and 8 open intake and exhaust valves 10 and 11 provided in the combustion chamber of the engine, and the rocker arm 9 drives the plunger (piston) 13 of the unit injector 12. Unit injector 1
2 drives the plunger 13 to inject high-pressure fuel into the combustion chamber. The relationship between the rotation angle of the cam 5 and the oil feed rate of the unit injector 12 is as shown in the oil feed rate diagram of FIG.

Further, the unit injector 12 controls the injection start timing (point P) and the injection end timing (point Q), that is, the injection timing, as shown in FIG. 8 by the built-in electromagnetic actuator (electromagnetic valve). The fuel pressure feeding period T can be controlled. The jerk type unit injector 12 is mounted on the cylinder head of the engine for each cylinder and driven by the camshaft 2.

[0005]

In the drive mechanism for the unit injector, the cam 5 for driving the unit injector 12 is attached to the cam shaft 2 for driving the intake and exhaust valves.
Since the cams 3 and 4 for driving the intake and exhaust valves are integrally provided, the phase of only the cam 5 for driving the unit injector cannot be arbitrarily changed. That is, the phase angle of the unit injector driving cam 5 cannot be changed, and the relationship between the cam rotation angle and the oil feed rate is uniquely determined as shown in the oil feed rate diagram of FIG. Therefore, there is a difference in injection pressure depending on the injection timing, and this difference may differ from the difference required from the performance of the engine.

For example, when the engine is operating under a high load, it is better to inject a large amount of fuel and at a high pressure as much as possible. Therefore, it is desirable to inject at a high injection timing and at a high pressure and a high oil transfer rate. However, if the injection start timing is advanced to the point P ', the injection pressure is low and the oil feed rate is low, so that the desired fuel amount cannot be supplied. That is, it is impossible to meet the demand of the engine that the injection timing is early and the injection is to be performed at a high pressure.

On the other hand, in idle operation, in order to reduce noise, it is better to delay the injection timing and to inject at a constant pressure as much as possible, and it is preferable to use a place where the injection pressure in the oil transfer rate diagram is low. However, the conventional jerk type unit injector is not a high pressure because it cannot control the oil feed rate and the injection timing independently, but it is a row type that can independently control the oil feed rate and the injection timing. It has disadvantages in terms of engine performance and exhaust gas compared to injection pumps.

The present invention has been made in view of the above points, and provides a unit injector drive mechanism capable of independently controlling the oil feed rate and the injection timing of the unit injector to improve engine performance. The purpose is to provide.

[0009]

In order to achieve the above object, according to the present invention, an intake / exhaust valve driving cam and a unit injector driving cam are provided rotatably supported on a cylinder head of an engine. A camshaft, a unit injector for injecting fuel into a combustion chamber of the engine, a rocker arm for an intake / exhaust valve having a base end abutting the cam for the intake / exhaust valve and a tip driving the intake / exhaust valve, and a base end for the unit. Drive of a unit injector including a rocker arm for a unit injector that abuts an injector driving cam and drives the unit injector, and a rocker shaft that rockably supports the rocker arm for the intake and exhaust valves and the rocker arm for the unit injector. In the mechanism, the rocker shaft and the rocker arm for the unit injector Between the unit injector rocker arm and the unit injector, and an eccentric member rotatably interposed between the unit injector rocker arm and eccentrically supporting the unit injector rocker arm to displace the contact position with the unit injector cam. And swinging the eccentric member and a swing arm having a correction means for moving the unit injector rocker arm in parallel between the unit injector driving cam and the unit injector while driving the unit injector. And a driving means.

By rotating the eccentric member, the unit injector rocker arm pivotally supported by the rocker shaft is displaced, and the contact position with the unit injector driving cam is displaced. This is the same as changing the phase of the cam rotation angle, and changes the oil feed rate of the unit injector. The driving force of the rocker arm for the unit injector is transmitted to the unit injector via the swing arm. The rocker arm for the unit injector moves in parallel (linearly moves) between the unit injector drive cam and the unit injector after being corrected by the contact surface having substantially the same shape as the eccentric locus of the eccentric member formed on the swing arm. However, the displacement in a direction different from the moving direction is absorbed. As a result, the oil feed rate of the unit injector can be changed. Further, the injection timing of the unit injector is electronically controlled by an electromagnetic actuator incorporated therein. As a result, the oil feed rate of the unit injector and the injection timing can be controlled independently.

[0011]

Embodiments of the present invention will be described below with reference to embodiments. The same members as those in FIG. 6 will be described with the same reference numerals. 1 and 2, intake and exhaust valve driving cams 3, 4 and a unit injector driving cam 5 are integrally formed on a cam shaft 2 which is rotatably supported on a cylinder head 1 of an engine. , The unit injector drive cams 5 are intake and exhaust valve drive cams 3, 4
It is provided between. The rocker shaft 6 is supported on the cylinder head 1 in parallel with the cam shaft 2, and the rocker shafts 7 and 8 for the intake / exhaust valves are swingably rotatable in association with the cams 3 and 4 for driving the exhaust / exhaust valves. It is supported. The rocker arms 7 and 8 are rotatably abutted on the corresponding cams 3 and 4, respectively, by the rollers provided at the respective base ends, and the respective tips are abutted against the intake valve 10 and the exhaust valve 11.

Rocker arm 15 for unit injector
Is rockably supported by a rocker shaft 5 via an eccentric collar 16 in correspondence with the unit injector driving cam 4. In this rocker arm 15, a roller 17 provided at the base end abuts on the cam 4 so that the roller 17 can roll, and a tip end 15a is formed.
Is in contact with the upper surface 18a of the swing arm 18. The swing arm 18 is rotatably pivotally supported by a supporting portion 19 which is arranged below the rocker arm 15 and whose base end is erected on the upper surface of the cylinder head 1. A push pin 20 attached to the tip end of the swing arm 18 serves as a unit injector 12. Is in contact with the upper end surface of the plunger 13.

The swing arm 18 is a rocker arm 15.
The upper surface 18a that abuts the tip 15a is formed in a curved shape that is convex upward. And this curved surface has an eccentric collar 16
Is formed so as to be substantially the same as the eccentric locus associated with the rotation of the. That is, the curved shape of the upper surface 18 a of the swing arm 18 is such that the roller 17 at the base end of the rocker arm 15 abuts on the base circular portion of the cam 5 and the tip portion 15 a abuts on the tip side of the upper surface 18 a of the swing arm 18, When the eccentric collar 16 is rotated in the state in which the plunger 13 of FIG. 2 is at the upper limit (top dead center) position, the rocker arm 15 causes the unit injector drive cam 5 and the unit injector 12 to be parallel to each other. The shape is such that it moves, that is, moves horizontally in the direction of arrow A in the drawing. As a result, rotation of the eccentric collar 16 causes the rocker arm 15 to move the unit injector drive cam 5
When moving (displacement) between the unit injector 12 and the unit injector 12, the vertical displacement of the rocker arm 15, that is, the displacement in a direction different from the moving direction is absorbed.

An arm 16a is formed on the eccentric collar 16 so as to face the base end side of the rocker arm 15, and a hole 16b is formed in the arm 16a in the axial direction. The base end of the shaft 21 is slidably inserted in the hole 16b in the axial direction. On the other hand, on the upper surface of the cylinder head 1, a cylinder 22 is erected obliquely upward in the vicinity of the camshaft 2 so as to face the tip 21a of the shaft 21, and the tip of the rod 23 is the tip 21a of the shaft 21.
Is rotatably connected to. The cylinder 22 does not need to be inclined and may be vertically installed. However, it is effective because it can be arranged in a narrow space by tilting it as shown in the drawing.

The rod 23 of the cylinder 22 contracts due to the spring force of the spring 24 when no hydraulic pressure is applied, and expands against the spring force when hydraulic pressure is applied. Then, the cylinder 22 rotates the eccentric collar 16 via the shaft 21 according to the expansion and contraction of the rod 23, and moves the rocker arm 15 in parallel in the arrow A or B direction. For example, when the rod 23 is retracted as shown by the solid line, the rocker arm 15 is moved to the maximum position in the direction of arrow B as shown in FIG. 3, and the eccentric collar 16 is rotated as it extends to move the rocker arm 15 to arrow A. Move in the direction. The cylinder 22 is connected to a hydraulic pump 27 via an oil passage 25 formed in the cylinder head 1 and an electromagnetic valve 26. The solenoid valve 26 is an on / off control valve and is controlled by an electronic control unit (not shown).

In this way, the unit injector 12
A variable phase mechanism 28 for varying the oil feed rate with respect to the cam rotation angle (phase) of is configured. Since the rocker shaft 6 does not rotate unlike the cam shaft 2, the rocker shaft 6 is not rotated.
By providing the eccentric collar 16 on the camshaft 2, the variable phase mechanism 28 can be simply configured with respect to that provided on the camshaft 2.

The operation will be described below. When the cam shaft 2 rotates as the engine rotates, the cams 3 and 4 rock the rocker arms 7 and 8 to open the intake valve 10 and the exhaust valve 11 at a predetermined timing. At the same time, the cam 5 is the rocker arm 15
Rocks. The rocker arm 15 pushes the plunger 13 of the unit injector 12 via the swing arm 18 as it rocks. As a result, the unit injector 12 pumps high-pressure fuel to the combustion chamber.

In the state where the cylinder 22 is retracted as shown in FIGS. 2 and 3, the rocker arm 15 has the arrow B.
Direction (to the maximum position on the unit injector 12 side. As a result, the rocker arm 15 is delayed in swing timing with respect to the rotation of the cam 5 in the direction of arrow C, and accordingly, the injection of the unit injector 12 is performed. The timing becomes late, and the relationship between the rotation angle (phase) of the cam 5 and the oil feed rate at this time is, for example, the oil feed rate diagram shown by the one-dot chain line in FIG.

When the solenoid valve 26 is energized and switched, and hydraulic pressure is supplied from the hydraulic pump 27 to the cylinder 22 to extend the rod 23, the eccentric collar 16 rotates accordingly, and the rocker arm 15 moves in the direction of arrow A. Move in parallel. As the rocker arm 15 moves in the direction of arrow A, the timing of swinging with respect to the rotation of the cam 5 becomes earlier, and the injection timing of the unit injector 12 also becomes earlier accordingly. The relationship between the rotation angle (phase) of the cam 5 and the oil feeding rate at this time is as shown in the oil feeding rate diagram shown by the solid line in FIG.

When the cylinder 22 further extends and the rocker arm 15 moves to the maximum position in the direction of arrow A as shown in FIG. 4, the swing timing becomes faster with respect to the rotation of the cam 5, and the unit injector accordingly. The injection timing of 12 is advanced. The relationship between the rotation angle (phase) of the cam 5 and the oil feeding rate at this time is as shown in the oil feeding rate diagram shown by the dotted line in FIG. In this way, the unit injector 1
The oil feed rate of 2 can be controlled.

On the other hand, the unit injector 12 controls the injection valve, that is, the injection start timing indicated by the point P and the injection end timing indicated by the point Q on the oil transfer rate diagram of FIG. 5, by controlling the built-in solenoid valve. You can control it freely.
As a result, the oil feed rate of the unit injector 12 and the injection timing can be controlled independently. Moreover,
Since the phase of the cam shaft 2 itself is not changed, the timing of opening the intake / exhaust valves 10, 11 does not change. This makes it possible to inject fuel into the combustion chamber at an oil feed rate and injection timing according to the operating state of the engine.

[0022]

As described above, according to the present invention, it is possible to independently control the oil feed rate and the injection timing of the unit injector, which improves engine performance and reduces fuel consumption and exhaust gas. Improvement is achieved. Moreover, the structure of the drive mechanism is simple, and the increase in cost and the increase in weight can be suppressed.

[Brief description of the drawings]

FIG. 1 is a plan view of essential parts showing an embodiment of a drive mechanism for a unit injector according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged view of a main part of FIG.

FIG. 4 is an explanatory view showing a state in which the rocker arm of FIG. 3 is displaced.

FIG. 5 is a diagram showing an example of an oil feed rate diagram of a unit injector according to the present invention.

FIG. 6 is a partial plan view of a drive mechanism of a conventional unit injector.

FIG. 7 is a cross-sectional view of essential parts taken along the line VII-VII of FIG.

8 is an oil feed rate diagram of the unit injector shown in FIG.

[Explanation of symbols]

 1 Cylinder Head 2 Cam Shaft 3 Intake Valve Driving Cam 4 Exhaust Valve Driving Cam 5 Unit Injector Driving Cam 6 Rocker Shaft 7 Intake Valve Rocker Arm 8 Exhaust Valve Rocker Arm 10 Intake Valve 11 Exhaust Valve 12 Unit Injector 13 Plunger 15 Unit Rocker arm for injector 16 Eccentric collar 18 Swing arm 21 Shaft 22 Hydraulic cylinder 23 Rod 26 Solenoid valve 27 Hydraulic pump 28 Variable phase mechanism

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F16C 3/28 F16C 3/28

Claims (4)

[Claims] 1. A camshaft rotatably supported on a cylinder head of an engine, provided with an intake / exhaust valve driving cam and a unit injector driving cam, and a unit injector for injecting fuel into a combustion chamber of the engine. A rocker arm for an intake / exhaust valve having a base end abutting the intake / exhaust valve cam and a tip driving the intake / exhaust valve; and a unit injector having a base end abutting the unit injector driving cam and a tip driving the unit injector. In a drive mechanism of a unit injector including a rocker arm for rocking, a rocker arm for rocking the intake / exhaust valve rocker arm, and a rocker arm for the unit injector so that the rocker shaft rotates between the rocker shaft and the rocker arm for the unit injector. It is freely intervened and the unit injector An eccentric member that eccentrically supports the cam arm to displace the contact position with the unit injector cam, and drives the unit injector interposed between the unit injector rocker arm and the unit injector, and A unit injector comprising: a swing arm having a correcting means for moving a unit injector rocker arm in parallel between the unit injector driving cam and the unit injector; and a driving means for rotating the eccentric member. Drive mechanism. 2. The correcting means forms a contact surface, with which the tip of the rocker arm for the unit injector of the swing arm abuts, in a shape substantially the same as the eccentric locus of the eccentric member. The drive mechanism for the unit injector according to 1. 3. The unit injector drive mechanism according to claim 1, wherein the drive means is a hydraulic cylinder interposed between the cylinder head and the eccentric member. 4. The drive mechanism for the unit injector according to claim 1, wherein the unit injector includes an electromagnetic actuator that electronically controls injection timing.