JPH0425420B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an in-line fuel injection system for a diesel engine.

(Conventional Example) In a conventional in-line fuel injection device, a plurality of plungers are driven by a plurality of cams provided on a camshaft, and the plungers inject fuel into an injection nozzle of a cylinder within a certain area during the upward stroke of the plunger. When pressurizing, for example, the end point of the fuel pumping area (pumping end point) is changed by turning a plunger, thereby changing the effective stroke of fuel pumping and changing the amount of fuel pumped to the injection nozzle (fuel injection amount). was.

However, in conventional devices, (a) the starting point of the fuel pumping area (pumping start point) is constant, and (b) the rising speed of the plunger is approximately constant except near the bottom dead center and top dead center. Due to this, it was not possible to change the fuel injection rate (the amount of fuel injected per unit rotation angle of the camshaft). Therefore, in the past, it has been difficult to obtain good fuel combustion performance in all engine speed-load ranges. That is, for example, if the fuel injection rate is set high in order to reduce blue-white smoke mixed in exhaust gas at low speeds, cavitation or erosion may occur at high speeds and high loads, or multiple injections may occur, resulting in deterioration of combustion performance. On the other hand, if the fuel injection rate is set to a small value, combustion performance at high speeds and high loads will improve, but blue-white smoke will increase at low speeds.

(Object of the Invention) The main object of the present invention is to provide an in-line fuel injection system in which not only the fuel injection amount but also the fuel injection rate can be changed according to engine speed, load, etc. Part of the goal is to make the device more compact.

(Structure of the Invention) The in-line fuel injection device according to the present invention includes (a) a control sleeve fitted to the plunger that can change both the starting point and the ending point of the fuel pumping zone, and (b) after the ascending speed of the plunger gradually increases. (c) A hydraulic timer mechanism is built into the camshaft, and a solenoid valve is provided to operate the timer mechanism. A plurality of cams 42 provided on the outer periphery of a supported cylindrical camshaft 41 drive a plurality of plungers 23, and the plungers 23 pump fuel to the injection nozzle 7 of the cylinder within a certain area during the upward stroke of the plunger 23. In the in-line fuel injection device of the type, a control sleeve 31 that can change both the start and end points of the fuel pumping area is fitted to the plunger 23, and the rising speed of the plunger 23 gradually increases and then gradually decreases after reaching a maximum point. The cam 42 is molded into an irregular shape, and a cam input shaft 44 is supported at both ends on the inner periphery of the cam shaft 41.
A high-pressure chamber 45 and a low-pressure chamber 46, which communicate or are shut off from each other via the timing control valve 13, are defined in an annular space between the intermediate outer periphery of the camshaft 41 and the inner periphery of the camshaft 41, separated by a large diameter portion 43b. It is connected to the camshaft 41 via an outer circumferential spline provided on the side adjacent to the large diameter portion 43b, and is connected to the cam input shaft 44 via an inner circumferential spline, and is connected to the cam input shaft 44 according to the pressure increase in the high pressure chamber 45. A hydraulic timer mechanism 50 is installed in which a sleeve 43 is movable in the direction of advancing the cam 42 in the direction of the torsion angle of the spline, and a timing control valve 13 for operating the timer mechanism 50 is switched. This in-line fuel injection device is characterized in that the fuel injection timing can be corrected after changing the fuel injection rate.

(Example) First, the overall structure of a diesel engine employing the present invention will be briefly described. That is, the first diagram shows the conceptual configuration of the diesel engine of the present invention when viewed from above.
In the figure, 1 is a crankcase, and four cylinders 2, for example, are attached to the crankcase 1 above. A crankshaft is pivotally supported within the crankcase 1, and a flywheel 3 is fixed to the end of the crankshaft that projects from the case 1 to the outside.
Reference numeral 4 designates a housing for a fuel injection pump, and within the housing 4, for example, four injection pumps are provided as will be described later. The discharge port 5 of the injection pump communicates with an injection nozzle 7 provided in each cylinder 2 via a high-pressure pipe 6. 8 is a main actuator according to the present invention;
9 is a sub actuator, both actuators 8,
9 is attached to the housing 4. As will be described in detail later, the main actuator 8 is a mechanism for mainly changing the fuel injection rate, and the sub actuator 9 is a mechanism for changing the fuel injection amount. The secondary actuator 9 corresponds to a conventional governor. both actuators 8,
9 is provided with position sensors 11 and 12, respectively, so that both sensors 11 and 12 can detect the fuel injection rate and the fuel injection amount. Numeral 13 is a timing control valve for operating a timer mechanism, which will be described later. Numeral 14 is a position sensor for the timer mechanism, and the sensor 14 can detect the timing of fuel injection. Also, 15 is the accelerator pedal,
16 is a rotational speed sensor provided on the flywheel 3; 17
are other sensor groups. The sensor group 17 includes, for example, an intake pressure sensor, an intake temperature sensor, a water temperature sensor, a glow current sensor, and the like.

In the present invention, for example, the accelerator pedal 15
The load value and engine rotation speed are calculated from the rotation speed 16 by the CPU 18 (central processing unit) of the microcomputer.
The fuel injection rate, fuel injection amount, and fuel injection timing can be automatically feedback-controlled by the CPU 18 according to these input values and the input values from the sensor group 17. In this case, "feedback control" of course refers to controlling the injection rate and the like while comparing the input values from the aforementioned sensors 11, 12, and 14 with the control target value.

Next, the main parts of the in-line fuel injection system will be explained in detail. FIG. 2 is a partially cutaway side view, of which portions A and B surrounded by two-dot chain lines show a cross section developed at 90°. In FIG. 2, within the housing 4, for example, four fuel injection pumps 20 are arranged, as described above. That is, the housing 4 supports a cylindrical barrel 22 via a cylindrical holder 21, and the upper part of the plunger 23 is fitted into the barrel 22 so as to be able to swing freely. Holder 21 above barrel 22
A well-known delivery valve 24 is installed inside.
A pressurizing chamber 30 (pump chamber) is formed within the barrel 22 between the upper end of the plunger 23 and the delivery valve 24. A spring seat 25 is fixed to approximately the middle portion of the plunger 23 in the longitudinal direction, and a return spring 26 is arranged between the seat 25 and the holder 21. A roller holder 27 is fixed to the lower end of the plunger 23, and the holder 27 pivotally supports a cylindrical roller 29 via a pin 28.

A control sleeve 31 according to the present invention is fitted into the lower part of the plunger 23 so as to be slidable and rotatable. That is, the above-mentioned main actuator 8 has a long control rod 32 extending inside the housing 4 in the left-right direction in FIG. It's fitted. By driving the rod 32 with a solenoid in the main actuator 8, the sleeve 31 can freely slide vertically relative to the plunger 23. Further, the sub actuator 9 has a long control rod 34 extending in the left and right direction inside the housing 4, and a rack 35 provided on the rod 34.
is engaged with the pinion 36 of each sleeve 31. By driving the rod 34 with a solenoid in the sub actuator 9, the sleeve 31 becomes rotatable relative to the plunger 23.

There is an oil leak hole 37 (spill) in the upper part of the sleeve 31.
has been established. Also, two types of leads 38 and 39 are provided on the outer periphery of the plunger at a position approximately corresponding to the sleeve 31.
has been established. That is, the lead 38 is connected to the plunger 23.
The lower part of the plunger 23 projects downward from the sleeve 31 when the plunger 23 is near the bottom dead center. Also, lead 39 is lead 3
The plunger 23 is provided in an inclined position with respect to the center line of the plunger 23, slightly above the plunger 8. Both leads 38 and 39 communicate with the pressurizing chamber 30 via an axial hole (not shown) in the plunger 23.

The cylindrical camshaft 41 has four cams 42 on its outer periphery, and the cams 42 are in contact with the roller 29. The cam 42 is formed into an irregular shape as will be described later. A cam input shaft 44 is fitted into the inner periphery of the camshaft 41 through a timer mechanism 50 consisting of a sleeve 43 and the like so as to be relatively rotatable. That is, a normal spline is provided on the outer circumference of the small diameter portion 43a of the sleeve 43 and on the inner circumference of the camshaft 41, so that the sleeve 43 can only slide freely relative to the camshaft 41. Further, a helical spline is provided on the inner circumference of the small diameter portion 43a and the outer circumference of the cam input shaft 44, so that when the sleeve 43 slides on the cam input shaft 44 and the cam shaft 41, it simultaneously connects the cam input shaft 4.
It is designed to rotate relative to 4. A high-pressure chamber 45 and a low-pressure chamber 46 are provided between the camshaft 41 and the cam input shaft 44, and the large-diameter portion 43b of the sleeve 43 maintains oil tightness between the two chambers 45,46. Both chambers 45 and 46 communicate with each other via an oil passage, and are connected to the timing control valve 1 described above.
3 (electromagnetic valve) can freely shut off the oil passage.

A transfer pump 47 (for example, a vane pump) is provided at the end of the cam input shaft 44 (the left end in FIG. 2). The pump 47 is driven by the input shaft 44 to supply fuel to the pressurizing chamber 30 of each injection pump 20 and the high pressure chamber 45 and low pressure chamber 46 of the timer mechanism 50. The fuel in both chambers 45 and 46 is used as hydraulic oil for the timer mechanism 50. Note that 48 is a discharge port for surplus fuel, and 49 is a fuel tank.

The rotational force of the cam input shaft 44 is transmitted to the camshaft 41 via the sleeve 43, and the plunger 23 is driven by the cam 42 on the camshaft 41 and rises and falls once during one rotation of the camshaft 41. The cam 42 of the present invention will now be described in comparison with FIG. In other words, the horizontal axis in Fig. 3 represents the cam angle (the rotation angle of the camshaft corresponding to the upward stroke of the plunger), and the vertical axis represents the cam speed (the upward speed of the plunger). It becomes zero at dead center. In the present invention, the cam 42 is formed into an irregular shape so that as the cam angle increases, the cam speed gradually increases and then gradually decreases after reaching the maximum point P, as shown by the solid line in FIG. Note that 2 in Figure 3
The dotted chain line represents the relationship between the cam angle and the plunger lift amount.

When the plunger 23 (FIG. 2) begins to rise, the fuel in the pressurizing chamber 30 leaks from the lead 38 into the holder 27, and fuel is not pumped to the injection nozzle. When the cam angle reaches θ ₁ in FIG. 3, the lead 38 is closed by the sleeve 31 and the pressurizing chamber 30
The fuel oil pressure inside increases. Accordingly, the fuel overcomes the resistance of the delivery valve 24, is forced to be sent to the injection nozzle via the discharge port 5 and the above-mentioned high-pressure pipe, and is injected from the nozzle into the cylinder. When the cam angle reaches θ ₂ , the lead 39 communicates with the oil leak hole 37, the fuel in the pressurizing chamber 30 leaks from the hole 37 into the holder 27, and the fuel pumping ends. That is, in the sleeve position shown in FIG. 2, fuel is pumped to the injection nozzle only within the shaded area C ₁ (cam angle area) in FIG. 3, and the cam speed area therebetween is S ₁ to _{S 2} .

Next, when the sleeve 31 is rotated by the sub-actuator 9 from the state shown in FIG. 2, the axial distance between the lead 39 and the oil leak hole 37 changes, thereby reaching the fuel pumping end point θ ₂ shown in FIG. moves, and the fuel injection amount is changed. Furthermore, sleeve 3
Even if you turn 1, the pumping start point θ ₁ does not move.

The main actuator 8 shown in FIG.
1 is slid downward, for example, the fuel pumping start point moves to θ ₃ in FIG. 3, the pumping end point moves to θ ₄ , and the cam speed range during fuel pumping becomes S ₃ to S ₄ .
In this case, since the cam speed range during fuel feeding becomes lower than before, the fuel being forced to be fed to the injection nozzle is biased weaker than before, and the fuel injection rate decreases. Conversely, when the sleeve 31 is slid upward, the cam speed range during fuel pumping increases, and the fuel injection rate increases. Note that if it is necessary to correct the fuel injection timing when changing the injection rate, the timing control valve 13 may be operated. For example, when part of the fuel in the high pressure chamber 45 is released to the low pressure chamber 46 by the valve 13, the sleeve 43 slides to the left in FIG. Rotates relative to the cam input shaft 44.

When embodying the present invention, the timer mechanism 5 in FIG.
0 may be operated using system oil. In that case, the camshaft 41 and the cam input shaft 44 can be lubricated with the system oil. The number of injection pumps 20 and cylinders can be changed freely. The "column fuel injection device" of the present invention includes a cam input shaft, a camshaft, a timer mechanism, a fuel injection pump, a control sleeve, an actuator, a high pressure pipe,
Refers to an assembly consisting of injection nozzles, etc.

(Effects of the Invention) As explained above, according to the present invention, (a) a control sleeve that can change both the starting point (pumping start point) and the end point (pumping end point) of the fuel pumping area is fitted into the plunger; (b) )The cam is shaped differently so that as the cam angle increases, the cam speed gradually increases and then gradually decreases after reaching a maximum point, so the control sleeve changes the cam speed range corresponding to the fuel pumping area, thereby controlling the fuel injection. rate can be changed. Therefore, any engine speed -
It becomes possible to obtain the optimum combustion state in the load range. Also, the fuel injection amount can be changed using the control sleeve as usual. Note that if a normal cam is used as in the past, the cam speed will be approximately constant over a wide area (cam angle range) during the plunger upward stroke, as shown by the broken line X in Figure 3, making it difficult to change the fuel injection rate. The problem is that the width is significantly narrowed.

Furthermore, if the timer mechanism 50 shown in FIG. 2 is operated using system oil and the fuel is supplied from the trusspher pump 47 only to the pressurizing chamber 30 of the injection pump 20, the fuel injection pressure can be increased. can.

Further, according to the present invention, since the cam shaft 41 is supported at both ends by the housing 4, the cam input shaft 44 acts on the plurality of cams 42 of the fuel injection pump 2.
Since it does not receive reaction force during 0 drive and only receives torsional reaction force (moment) from the spline, it can be made smaller in diameter. Moreover, since the camshaft 41 is arranged on a cylinder, its bending strength is almost unchanged.
A hydraulic timer mechanism 50 and a cam input shaft 4 are installed in the shaft center hole.
4 can be provided, and the pump housing 4 is hardly enlarged.

Furthermore, if the fuel injection rate, injection amount, and injection timing are configured to be automatically feedback-controlled by the CPU 18 of the microcomputer as shown in Fig. 1,
The injection rate, injection amount, and injection timing can be easily controlled, quickly, and accurately. By employing the sensor group 17 and controlling the injection rate and the like with reference to data such as the intake pressure and the intake temperature, control performance is further improved.

Also, solenoid actuators 8, 9 (second
If the control sleeve 31 is electronically controlled using the method shown in Fig.), the sleeve 31 can be operated reliably.
The actuators 8 and 9 are also miniaturized. Solenoid valve 13
By using this, the timer mechanism 50 can be operated accurately.

[Brief explanation of drawings]

FIG. 1 is a schematic structural diagram of a diesel engine employing the present invention, FIG. 2 is a cutaway side view of an in-line fuel injection system, and FIG. 3 is a graph showing the relationship between cam angle and cam speed. 23... Plunger, 31... Control sleeve, 41... Camshaft, 42...
cam.

Claims (1)

[Claims] 1 A plurality of plungers 23 are driven by a plurality of cams 42 provided on the outer periphery of a cylindrical camshaft 41 supported at both ends by the housing 4, and the injection nozzle of the cylinder is driven by the plunger 23 within a certain area during the upward stroke of the plunger 23. 7, a control sleeve 31 that can change both the starting point and the ending point of the fuel pumping area is fitted to the plunger 23, and the rising speed of the plunger 23 gradually increases until the maximum point is reached. The cam 42 is formed into an irregular shape so that the shape gradually decreases from A high-pressure chamber 45 and a low-pressure chamber 46, which are communicated with or shut off from each other via the timing control valve 13, are separated by a large-diameter portion 43b, and an outer circumferential spline is provided on the side that continues from the large-diameter portion 43b. The cam shaft 41 is connected to the cam shaft 41 through the spline on the inner circumference, and the cam input shaft 44 is connected to the cam input shaft 44 through a spline on the inner circumference.
A hydraulic timer mechanism 50 is incorporated in which a sleeve 43 is movable in the direction of advancing the torsion angle of the spline.
Timing control valve 1 that operates 0
3. After changing the fuel injection rate by changing the fuel injection rate, the in-line fuel injection device is characterized in that the fuel injection timing can be corrected.