JPH07189858A - Fuel injection timing control device for unit injector - Google Patents

Abstract

PURPOSE:To enable injection timing control with small driving force by fitting an eccentric collar in a retatively rotatable manner between a rocker shaft and a rocker arm, and thus engaging or disengaging the eccentric collar for the rocker arm. CONSTITUTION:An eccentric collar 34 is fitted relatively rotatable on outer periphery of a rocker shaft 22 fixed in a cylinder head. A supporting hole 231 of a rocker arm 23 is fitted retattively rotatable to an eccentric portion 341 of the eccentric collar 34. When a pin 37 is moved hydraulically to the left, the rocker arm 23 becomes engaged to the eccentric collar 34, so that it swings around the rocker shaft 22. On the other hand, when the pin 37 is moved to the right, the eccentric collar 34 becomes engaged to a fixation member 33 integrated to the rocker shaft 22, so that the rocker arm 23 swings around the eccentric collar 34. Accordingly, by a change in the swing center of the rocker arm 23, pre-stroke of a plunger in the injector, i.e., the fuel injection timing is thus controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a rocker shaft,
The present invention relates to a unit injector including a rocker arm pivotally supported by a rocker shaft and driven to swing by a cam, a plunger reciprocally driven by the rocker arm, and a nozzle for injecting fuel pumped by the plunger.

[0002]

2. Description of the Related Art As such a unit injector, the one described in JP-A-59-39964 is known. According to this unit injector, the rocker shaft having the eccentric portion is rotated by the actuator to move the rocking center of the rocker arm, thereby changing the operation start timing of the plunger and controlling the fuel injection timing.

[0003]

By the way, since the unit injector needs to inject fuel at a high pressure, the descending speed of the plunger driven by the rocker arm is set to a large value. Further, in order to prevent the plunger from jumping during high speed rotation, a spring having a strong elastic force is used as the plunger return spring. For this,
A large load acts on the drive system that transmits the drive force from the camshaft to the plunger, especially on the pivotal support between the rocker shaft and the rocker arm.

However, the above-mentioned conventional structure has a structure in which a rocker arm is pivotally supported on an eccentric part of a rocker shaft which is rotationally driven, and therefore, when the rocker shaft is rotationally driven by an actuator for controlling fuel injection timing, There is a problem that an extremely large load acts on the actuator.

The present invention has been made in view of the above circumstances, and an object thereof is to control the fuel injection timing of a unit injector with a small driving force.

[0006]

In order to achieve the above object, the invention described in claim 1 is a rocker shaft, a rocker arm pivotally supported by the rocker shaft and oscillated by a cam, and a rocker. In a unit injector including a plunger reciprocally driven by an arm and a nozzle for injecting fuel pumped by the plunger, an eccentric collar is relatively rotatable between an outer circumference of a rocker shaft and an inner circumference of a support hole of a rocker arm. It is characterized in that it is fitted and the eccentric collar is connected or disconnected from the rocker arm by the connection switching means.

According to a second aspect of the present invention, in addition to the structure of the first aspect, the coupling switching means is a fixing member fixed to the rocker shaft; and the fixing member is formed in the axial direction of the rocker shaft. A first pin hole; a second pin hole formed in an eccentric collar so as to face the first pin hole; a third pin hole formed in a rocker arm so as to face the second pin hole; A pin slidably fitted in the pin hole and movable between a position engaging with the first pin hole and the second pin hole and a position engaging with the second pin hole and the third pin hole; It is characterized by having.

The invention described in claim 3 is characterized in that, in addition to the configuration of claim 2, the pin is hydraulically driven.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 5 show an embodiment of the present invention. FIG. 1 is a vertical sectional view of a cylinder head portion of a diesel engine, FIG. 2 is an enlarged view of a main portion of FIG. 1, and FIG. Of 3-3
FIG. 4 is a schematic view of the control system, and FIG. 5 is a graph for explaining the operation.

As shown in FIG. 1, a diesel engine E
Includes a cylinder head 2, a cam case 3 and a head cover 4 which are joined to the deck surface of the cylinder block 1 in a stacked state. A piston 6 is slidably fitted in a cylinder 5 formed in the cylinder block 1, and a combustion chamber 8 connected to an intake port 7 is formed between a lower surface of the cylinder head 2 and an upper surface of the piston 6. . Cylinder head 2
A glow plug 9 having a tip protruding into the combustion chamber 8 is provided in the.

A cam shaft 11 having an intake cam 10 is rotatably supported on the cam case 3, and the intake cam 10 is provided with an intake cam follower 1 of an intake rocker arm 13 pivotally supported on the cam case 3 via a rocker shaft 12.
Abut 4. The tip of the intake rocker arm 13 abuts on the upper end of the shaft portion of the intake valve 16 which is slidably supported by the cylinder head 2 and is urged in the valve closing direction by the intake valve spring 15. An exhaust port, an exhaust cam, an exhaust rocker arm, an exhaust cam follower, an exhaust valve spring, and an exhaust valve, which are not shown, are provided so as to overlap the back side of the drawing with respect to the intake system shown in FIG.

When the camshaft 11 rotates in association with the rotation of the crankshaft, the intake valve 16 is opened / closed via the intake cam 10 and the intake rocker arm 13, and the exhaust cam and the exhaust rocker arm are driven. The exhaust valve is opened / closed via this.

The unit injector I is fitted into the mounting seat of the cylinder head 2 from above in a state of being slightly inclined with respect to the axis of the cylinder 5, and is fixed by a bolt 21 so that its lower end projects into the combustion chamber 8. It An intermediate portion of a rocker arm 23 is pivotally supported on a rocker shaft 22 arranged between the upper end of the unit injector I and the upper end of the intake valve 16. The support shaft 2 is provided at one end of the rocker arm 23.
The roller-shaped cam follower 25 supported via
The injector cam 2 fixed to the camshaft 11
Abut on 6.

Next, the structure of the coupling switching means 20 will be described. As is clear from referring to FIGS. 3 and 4 together,
The rocker shaft 22 is non-rotatably supported by bearings 31 and 32 provided on the cylinder head 2. A plate-shaped fixing member 33 is integrally fixed to the rocker shaft 22 so as to be in contact with one bearing 31, and at a position adjacent to the fixing member 33, the inner circumference of the eccentric collar 34 is provided on the outer circumference of the rocker shaft 22. Fits so that they can rotate relative to each other. The eccentric collar 34 includes an eccentric portion 34 ₁ that is eccentric with respect to the axis of the rocker shaft 22 and a flange portion 34 ₂ that faces the fixing member 33, and supports the rocker arm 23 on the outer periphery of the eccentric portion 34 _1. The inner periphery of the hole 23 ₁ is fitted so as to be relatively rotatable. The rocker arm 23 has the other bearing 3
It is urged toward the flange portion 34 ₂ of the eccentric collar 34 via a spring 35 and a washer 36 which are contracted between the two.

The fixing member 33, the flange portion 34 ₂ of the eccentric collar 34, and the rocker arm 23 have a first pin hole 33 ₁ , a second pin hole 34 _3, and a third pin hole 23, respectively.
₂ is formed coaxially. The pin holes 33 ₁ , 34 ₃ ,
A common pin 37 is slidably fitted to 23 ₂ . When the pin 37 is in the left position (retarded state) shown in FIG. 3A, the rocker arm 23 and the eccentric collar 34 are relatively non-rotatably coupled, and the rocker arm 23 swings around the rocker shaft 22. On the other hand, when the pin 37 is in the right position (advanced state) shown in FIG. 3B, the eccentric collar 34 and the fixing member 33 are relatively non-rotatably coupled, and the rocker arm 23 is eccentric to the eccentric portion 34. Swing around ₁

The pin 37 is hydraulically driven. That is, the oil passage 22 formed inside the rocker shaft 22.
₁ extends in the radial direction and the first pin hole 33 ₁ of the fixing member 33
Figure 3 is communicated, by the action of hydraulic pressure to the first pin hole 33 _1, the pin 37 from the position shown in FIG. 3 (B) to
It can be driven to the position (A). A pressing member 39 biased rightward by a spring 38 is slidably supported in the third pin hole 23 ₂ of the rocker arm 23. Therefore, when removing the pressure from the first pin hole 33 ₁ of the fixing member 33, a pin 37 which is pressed by the pressing member 39 which is urged to the right by a spring 38, FIG. 3 from the position of FIG. 3 (A) ( Move to the position of B). Reference numeral 40 denotes a first pin stopper accommodated in the bore 33 ₁ of the fixing member 33, which restricts the rightward movement end of the pin 37.

Incidentally, the first pin hole 33 ₁ and the second pin hole 3
The phases of 4 ₃ and the third pin hole 23 ₂ are set as follows. That is, the eccentric collar 34 and the fixing member 33 are coupled to each other so that they cannot rotate relative to each other, so that the rocker arm 23 becomes eccentric.
The eccentric portion 34 ₁ is swung around, and the cam follower 25 is brought into contact with the maximum lift circle of the injector cam 26 to move the plunger 56 to the maximum stroke. The first pin hole 33 ₁ , the second pin hole 34 _3, and the third pin hole 23 ₂ are aligned on the same straight line so that the pin 37 can slide in this state.

As shown in FIG. 2, the pump portion 50 of the unit injector I includes a pump housing 51 and an adjusting bolt 27 slidably supported on an upper portion of the pump housing 51 and screwed to the other end of the rocker arm 23. A tappet 52 that comes into contact with the lower surface of the pressing member 28 that is swingably provided to the user, a return spring 54 that biases the tappet 52 toward the rocker arm 23, a cylinder 55 fixed inside the pump housing 51, and a cylinder. A plunger 56 slidably fitted to the lower end of the tappet 52 and a pressure chamber 57 formed at the lower end of the plunger 56; A sleeve 58 rotatable integrally with the plunger 56,
A control rack 60 that reciprocates by an actuator 59 (see FIG. 4) to rotate and drive the sleeve 58, and a fuel supply passage 61 that supplies fuel to the pressure chamber 57 are provided.

A fuel supply passage 61 is provided on the side wall of the cylinder 55.
A port 55 ₁ is formed which connects the pressure chamber 57 and the pressure chamber 57. Further, a notch 56 ₁ whose relative positional relationship with the port 55 ₁ is changed by rotation of the plunger 56 is formed at the lower end of the plunger 56.

Nozzle portion 62 of unit injector I
Is a nozzle housing 63 connected to the lower end of the pump housing 51, a spring seat 64 fixed to the upper part of the nozzle housing 63, and a nozzle 65 fixed to the lower part of the nozzle housing 63 so that the lower end extends into the combustion chamber 9. A spool 66 fitted in the inner periphery of the nozzle 65 so as to be vertically movable with a predetermined gap, and a spool 6 accommodated in the spring seat 64.
6, a spring 67 for urging 6 downward, and the pressure chamber 57
And a feed passage 68 that communicates with the gap between the nozzle 65 and the spool 66.

As shown in FIG. 4, fuel is supplied to a plurality of unit injectors I provided for each cylinder 5 of the engine E from a common fuel common passage 61. The sleeve 58 of each unit injector I is rotationally driven in synchronization by a common control rack 60 operated by an actuator 59. Further, oil pumped from the oil pump 29 is supplied to the oil passage 22 ₁ (see FIG. 3) formed inside the rocker shaft 22 of each unit injector I through the solenoid valve 30.

The actuator 59 and the solenoid valve 30
Is connected to and controlled by an electronic control unit U to which signals from the engine speed sensor 71, the water temperature sensor 72, and the accelerator opening sensor 73 are input.

Next, the operation of the embodiment of the present invention having the above construction will be described.

When the engine E is started, the solenoid valve 31
By the by operating pull out the pressure from the oil passage 22 ₁ of the rocker shaft 22, as shown in FIG. 3 (B), the pin 37 by the pressing member 39 which is urged by the resilient force of the spring 38
Is moved to the right to integrate the fixing member 33 and the eccentric collar 34 into an advanced state. As a result, the rocker arm 23 is guided by the eccentric portion 34 ₁ of the eccentric collar 34 and swings around the point b in FIG.

Next, the operation in the case of the advance angle state will be described with reference to the graph of FIG. The graph in Figure 5 is
The horizontal axis represents the rotation angle of the injector cam 26, and the vertical axis represents the cam speed (shown by the solid line) and the cam lift amount (shown by the broken line).

When the injector cam 26 rotates in the direction of the arrow in FIG. 1 and its rotation angle is at the position A in FIG. 5, the cam follower 25 is in contact with the base circle of the injector cam 26, and the cam speed and the cam lift are increased. Both quantities are 0. When the rotation angle of the injector cam 26 reaches the B position, the base circle of the injector cam 26 ends, and the cam lift amount starts to increase, so that the rocker arm 23 starts swinging. As a result, the rocker arm 23 starts to swing, and at the same time, the plunger 56 pressed by the tappet 52 starts to descend.

When the rotation angle of the injector cam 26 reaches the D position, the plunger 5 descends in the cylinder 55.
The lower end of 6 closes the port 55 ₁ connected to the fuel supply passage 61. As a result, the prestroke of the plunger 56 ends and the effective stroke starts, and the plunger 56
The fuel in the pressure chamber 57 compressed on the lower surface of the nozzle passes through the feed passage 68 and the nozzle 65 of the nozzle portion 62 and the spool 66.
Supplied in the gap between. Then, when the pressure of the supplied fuel rises above a predetermined value, the spool 66 rises against the spring 67, whereby the lower end of the nozzle 65 opens and the fuel is injected into the combustion chamber 8. Thus, the fuel injection started when the rotation angle of the injector cam 26 reaches the D position is continued until the rotation angle reaches the F position and the cam lift amount becomes maximum.

As described above, when the engine E is started, the fixing member 33 and the eccentric collar 34 are connected to be in an advanced state, so that the timing of starting fuel injection can be advanced and the starting performance of the engine E can be improved. .

When the warm-up is completed after the engine E is started,
The solenoid valve 30 is activated by a command from the electronic control unit U, and hydraulic pressure acts on the oil passage 22 ₁ of the rocker shaft 22. As a result, as shown in FIG. 3 (A), the pin 37 moves to the left to release the connection between the fixing member 33 and the eccentric collar 34, and the eccentric collar 34 and the rocker arm 23 are connected. In the retarded state, the rocker arm 23 and the eccentric collar 34 are integrated into the rocker shaft 2
It is guided to the outer periphery of 2 and swings around the point a in FIG.

The pin 37 is hydraulically operated to set the retard angle.
Time when moving in the left direction in FIG. 3, the left end of the pin 37 even if it is not immediately fitted to the third pin hole 23 _{and second} rocker arm 23, the phase rocker arm 23 swings matches Then, the pin 37 is fitted into the third pin hole 23 ₂ of the rocker arm 23. At this time, the rocker arm 23 pressed by the pin 37 can temporarily escape to the left while compressing the spring 35.

In the retarded state, the rocker arm 2
Since the swing center of 3 moves from point b to point a in FIG. 2, the other end of the rocker arm 23 slightly moves up as compared with the advanced state. As a result, the elastic force of the return spring 54 causes the tappet 52 to move.
And the plunger 56 is slightly raised as compared with the advanced state.

As a result, the prestroke of the plunger 56 is slightly increased, so that the E position where the lower end of the plunger 56 closes the port 55 ₁ also lags behind the D position in the advanced angle state. It is possible to delay the timing at which the injection of is started. That is, in the retarded state, the prestroke of the plunger 56 increases, and the timing of starting the fuel injection is delayed.

As described above, when the warm-up of the engine E is completed, the rocker arm 23 and the eccentric collar 34 are coupled to set the rocker shaft 22 in the retarded state and the fuel injection start timing is delayed to delay the exhaust gas of the engine E. It is possible to reduce the amount of NO _x and secure the output.

Thus, the pre-stroke of the plunger 56 can be changed and the fuel injection timing can be controlled simply by moving the pin 37 by hydraulic pressure and connecting the eccentric collar 34 to the rocker shaft 22 or the rocker arm 23. . As a result, the driving force can be significantly reduced as compared with the conventional actuator that rotates the rocker shaft to change the rotation center of the rocker arm.

When the plunger 56 is rotated together with the sleeve 58 by driving the control rack 60 with the actuator 59, the positional relationship between the notch 56 ₁ formed at the lower end of the plunger 56 and the port 55 ₁ of the pressure chamber 57 changes. To do. As a result, the timing at which the port 55 ₁ is closed by the plunger 56 changes and the effective stroke of the plunger 56 changes, whereby the fuel injection amount is controlled. The fuel injection amount control by the actuator 59 functions similarly in any of the advanced angle state and the retarded angle state. That is, the notch 56 _{1 of the} plunger 56 and the port 5 of the pressure chamber 57 are activated by the operation of the actuator 59.
When the positional relationship with 5 ₁ changes, both the D position (fuel injection start position in the advanced angle state) and the E position (fuel injection start position in the retarded angle state) move in parallel in the horizontal axis direction in FIG. .

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and various design changes can be made.

For example, turning on the hydraulic pressure acting on the pin 37
To reverse the relationship between OFF and the magnitude of the prestroke, the eccentric direction of the eccentric portion 34 ₁ of the eccentric collar 34 is reversed (that is, the positional relationship between the thick portion and the thin portion of the eccentric portion 34 ₁ is reversed). ) You can set it.

[0039]

As described above, according to the first aspect of the present invention, the eccentric collar is rotatably fitted between the outer periphery of the rocker shaft and the inner periphery of the support hole of the rocker arm so as to be eccentric. By coupling or uncoupling the collar to or from the rocker arm by the coupling switching means, the rocker arm can be swung around the rocker shaft or around the eccentric collar to control the fuel injection timing, and the rocker shaft can be controlled by the actuator. It is possible to control the fuel injection timing with a driving force smaller than that of the rotating one.

According to the invention described in claim 2,
Since the coupling switching means is composed of three pin holes and the pins slidably fitted in these pin holes, the coupling switching means can be constructed with an extremely simple structure.

According to the invention described in claim 3,
By driving the pin hydraulically, the structure of the drive system of the coupling switching means can be simplified.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a cylinder head portion of a diesel engine.

FIG. 2 is an enlarged view of a main part of FIG.

3 is an enlarged sectional view taken along line 3-3 of FIG.

FIG. 4 is a schematic diagram of a control system.

FIG. 5 is a graph illustrating the operation

[Explanation of symbols]

20 coupling switching means 22 rocker shaft 23 rocker arm 23 ₁ support hole 23 ₂ third pin hole 26 injector cam (cam) 33 fixing member 33 ₁ first pin hole 34 eccentric collar 34 ₃ second pin hole 37 pin 56 plunger 65 nozzle

Claims (3)

[Claims] 1. A rocker shaft (22), a rocker arm (23) pivotally supported by the rocker shaft (22) and rockably driven by a cam (26), and a plunger reciprocally driven by the rocker arm (23). (56),
A unit injector having a nozzle (65) for injecting fuel pumped by a plunger (56), comprising a rocker shaft (22) and a rocker arm (2).
The eccentric collar (3) is formed between the inner periphery of the support hole (23 ₁ ) of 3).
Fuel injection timing control in a unit injector, characterized in that the eccentric collar (34) is connected to the rocker arm (23) by the connection switching means (20) so as to be relatively rotatably fitted to the rocker arm (23). apparatus. 2. The coupling switching means (20) is a rocker shear.
A fixing member (33) fixed to the shaft (22); a fixing portion
Formed on the material (33) in the axial direction of the rocker shaft (22)
First pin hole (33₁) And; to the eccentric collar (34)
The first pin hole (33₁) Formed so as to be opposed to
Pin hole (34₃) And the rocker arm (23) with the
2 pin hole (34₃) Formed so as to be opposed to
(23 ₂) And; each of the pin holes (33₁, 34₃, 2
Three₂) Is slidably fitted to the first pin hole (33₁)as well as
Second pin hole (34₃) And the second pin hole (3
Four₃) And the third pin hole (23₂) Engaging position
A pin (37) capable of moving the
The fuel in the unit injector according to claim 1.
Injection timing control device. 3. The fuel injection timing control system for a unit injector according to claim 1, wherein the pin (37) is hydraulically driven.