JPS62288364A - Fuel injection device - Google Patents

Abstract

PURPOSE:To aim at reducing tapping sound during low speed operation while ensuring a high horse power during high speed operation, by giving a cam characteristic having a low speed range at the leading stage and a high speed range at the trailing stage, to a cam device for transmitting rotation of the drive shaft of a fuel injection pump. CONSTITUTION:A drive shaft 4 is fitted in a housing 3 of a fuel injection pump 1 to provide a pressurizing mechanism 6. A cam device 18 is adapted to convert the rotation of the drive shaft into reciprocating motion which is then transmitted to the plunger 8. A cam characteristic having a low speed range at the leading stage and a high speed range at the trailing stage with respect to the cam rotating angle, is given to the cam device 18. There are provided a first spring 1 for setting a first valve opening pressure and a piston for setting a second valve opening pressure. Thus, it is possible to aim at reducing tapping sound during low speed operation while ensuring a high horse power during high speed operation.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a fuel injection device, and particularly to a fuel injection device used in a diesel engine such as an automobile.

(Prior Art) A distribution type fuel injection pump is known as a fuel injection pump used in this type of fuel injection device, and this is disclosed in Japanese Patent Laid-Open No. 60-5
As shown in Publication No. 0268, it has a pressure mechanism in which a plunger is fitted into a cylinder, and the plunger in this pressure mechanism is connected to a drive shaft via a cam device consisting of a cam disk and a roller. The rotary motion of the drive shaft is converted into the reciprocating rotation of the plunger, and fuel is distributed and pumped in accordance with the reciprocating rotation of the plunger.

By the way, in diesel engines, at low speeds and low loads, the injection rate is reduced to produce gentle combustion and reduce knocking noise, while at high speeds and high loads, the injection rate is increased to increase horsepower and reduce emissions such as NoX. There has long been a demand for lowering this.

(Problems to be Solved by the Invention) The cam device in the above-mentioned conventional example has a characteristic that the cam speed changes at a constant rate with respect to the cam rotation angle, and the fuel injection pump has a characteristic that the internal pressure of the injection pipe is In order for the nozzle opening pressure to rise above the nozzle opening pressure and for injection to begin, a predetermined stroke of the plunger is required.

Therefore, regardless of whether the engine speed is low or high, the stroke of the plunger until the start of injection is constant.
The problem was that the part with the highest cam speed was used during injection, resulting in a high injection rate, and the knocking noise was loud at low speeds such as idling and low load. To solve this,
If a cam with a sufficiently long low-speed section is used in the front stage, it is possible to inject using the low-speed section even if the plunger strokes more than a predetermined period. This is impossible with a multi-cylinder engine.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a fuel injection device that can eliminate the above conventional problems and reduce knocking noise at low speeds and low loads while ensuring a high injection rate at high speeds and high loads. This is an issue.

Incidentally, the applicant has previously proposed a fuel injection pump that achieves the same problem in Japanese Patent Application No. 61-9481, but in this, the pressure for delivering fuel from the fuel injection pump in the low speed region is low. Therefore, when using a normal fuel injection valve, the needle valve will not lift to its full extent. For this reason, the 9th
As shown in the figure, it became clear that the needle valve lift fluctuated significantly and the nozzle pressure P fluctuated greatly, resulting in a lack of stability. The present invention attempts to solve the problems of the prior application as well.

(Means for Solving the Problems) However, the feature of the present invention is that the cam device of the fuel injection pump described above has a low speed region at the front stage and a true speed region at the rear stage with respect to the cam rotation angle. Gives certain cam characteristics,
In addition, the fuel injection valve is equipped with a two-stage valve opening pressure mechanism that is set so that the delivery pressure in the low speed region of the fuel injection pump is between the first valve opening pressure and the second valve opening pressure. .

(Function) Therefore, by increasing the residual pressure in the injection pipe, the pressure in the pipe can be made equal to or higher than the nozzle opening pressure at the time of the next injection even when the stroke of the plunger is small. For this reason, the front stage portion of the cam device is used, and since the front stage portion of the cam device is in a low speed region, the injection rate can be lowered at the initial stage of injection. Therefore, the overall injection rate can be lowered at low speeds when the injection amount is small. On the other hand, at high speeds, the rear stage portion of the cam device is used in addition to the front stage portion, and since the rear stage portion of the cam device is in the high speed region, the injection rate becomes high.

In addition, since the injection rate is low in the low speed region, the pressure of fuel delivered from the fuel injection pump is low, but since the fuel injection valve is equipped with a two-stage valve opening pressure mechanism, the pressure at the position corresponding to the first valve opening pressure is low. The needle valve can be fixed, and therefore the above object can be achieved.

(Example) In FIG. 1, the fuel injection pump 1 is, for example, a distribution type,
It has a housing 3 that constitutes a suction space 2, a drive shaft 4 is inserted into this housing 3, a feed pump 5 is attached to this drive shaft 4, and fuel is supplied to the suction space 2 by driving the feed pump 5. It is now being supplied.

Further, the housing 3 is provided with a pressurizing mechanism 6,
This pressurizing mechanism 6 includes a cylinder 7 fixed to the housing 3 and a plunger 8 slidably inserted into the cylinder 7. A high pressure chamber 9 is defined by the plunger 8 and the cylinder 7. are doing. The plunger 8 is connected to the drive shaft 4 via a cam device 18, which will be described below, and is configured to rotate and reciprocate. A number of suction groups 10 corresponding to the number of cylinders are arranged around the tip of the plunger 8 in high pressure chambers 9.
It is formed to be connected to. Furthermore, the housing 3 and the cylinder 7 have one end connected to the aforementioned suction space 2.
a suction passage 11 whose other end opens into the cylinder 7;
is formed, and this suction group 11 is formed when the plunger 8 aligns during the suction stroke and is connected to the suction passage 11 from the suction space 2.
Fuel is sucked into the high pressure chamber 9 through the high pressure chamber 9.

Further, the housing 3 and the cylinder 7 are formed with a number of pressure passages 12 corresponding to the number of cylinders, and one end of the pressure passage 12 is opened into the cylinder 7. On the other hand, one distribution boat 13 is formed on the outer peripheral surface of the plunger 8.

This distribution boat 13 communicates with the high pressure chamber 9 through a vertical hole 14 and a horizontal hole 15 formed in the plunger 8, and during the discharge stroke of the plunger 8, the fuel pressurized in the high pressure chamber 9 is distributed. and is discharged from the pressure feeding passage 12.

The plunger 8 has a spill boat 16 formed in the radial direction for communicating the end of the borehole 14 opposite to the high-pressure chamber with the suction space 2, and a control sleeve 17 is provided outside the portion where the spill boat 16 is formed. By adjusting the axial position of the control sleeve 17, the timing of changing the injection path can be controlled.

The cam device 18 has a cam disk 19 fitted and fixed to the left end of the plunger 8, and the cam disk 19 and the drive shaft 6 are connected to each other via a cross coupling (not shown) to allow movement in the axial direction. ing. Cam surfaces are formed on the periphery of the left side of the cam disk 19 in correspondence with the number of cylinders. The roller 21 strongly contacts this cam surface, and this roller 2
1 is supported by a roller holder 22. Further, the cam disc 19 is attached to the return spring 23 together with the plunger 8.
The cam disk 19 is pressed leftward by the roller 21, and the cam disk 19 rotates while being pressed against the roller 21. As shown in FIG. 4, the cam device 18 has an approximately constant speed V (for example, 0.25
The cam has a cam characteristic divided into a low speed region where the maximum speed of the rear stage is VZ (for example, 0.75+++/sec) and a high speed region where the maximum speed of the rear stage is VZ (for example, 0.75+++/sec).

Note that the roller holder 22 is equipped with, for example, an electronically controlled timer 24.
The timer 24 is connected to the timer 24 so that advance angle control can be performed.

The delivery valve device 25 has an Angleich mechanism, and is provided at the outlet end of the pressure feeding passage 12 and connected to the housing 3.
a holder 26 screwed onto the housing 3; a valve seat body 27 fixed to the housing 3 by the holder 26;
The valve spring 29 is arranged within the pump 26 and presses the valve body 28 against the valve seat body 27. The holder 26 is connected to a fuel injection valve 31, which will be described later, via an injection pipe 30.

As shown in FIGS. 2 and 3, the valve body 28 is
A seat portion 32 is formed on the front end side of the spring receiver to receive the aforementioned valve spring 29, and a seat portion 32 having a surface and a seat surface that comes into contact with the valve seat surface of the valve seat body 27, and the valve seat body 27 is formed on the rear end side. A separate guide portion 33 is formed which slides inside. A suction back collar 34 is formed between the seat portion 32 and the guide portion 33, but this suction back collar 34 is different from the standard one which is circular. A cutout 35 is formed on the periphery, and the Angleich mechanism is configured by the cutout 35. That is, when the engine speed is low, the valve body 28 slowly seats on the valve seat body 27, so that the fuel sucked back from between the notch 35 and the valve seat body 27 escapes to the injection pipe side. However, as the engine speed increases, the valve body 28 seats on the valve seat body 27 at high speed, so it acts as if the notch 35 was not formed, and the amount of suction is the same as normal. This is the amount of sucking back. As a result, as shown in FIG. 5, the residual pressure Pr in the injection pipe decreases as the engine speed N increases.

In this embodiment, the Angleich mechanism is constructed by forming the notch 35 in the suction collar 34, but the mechanism is not limited to this, and any mechanism may be used as long as the suction amount can be adjusted.

The fuel injection valve 31 is, for example, a known two-stage spring type shown in FIG.
is screwed through a cap nut 38. Nozzle 3
7 is provided with a needle valve 39, and a first
The spring receiver 40 is in contact with it. Further, a guide sleeve 41 is fixed within the valve holder 36, and a first spring 42 is elastically mounted between the lower end of the guide sleeve 41 and the first spring receiver 40 described above. A first bushing rod portion 43 extending from the first spring receiver 40 is inserted into the guide sleeve 41 at the bottom, and a second bushing rod portion 45 extending downward from the second spring receiver 44 is inserted into the upper portion. Insert this first
bushing rod part 43 and second bushing rod part 45
A distance NLI is provided between them. Then, the second spring receiver 44 and the above-mentioned valve holder 36
A third spring receiver 46 whose position is adjustable
A second spring 47 is loaded between the two.

Therefore, when the pressure of the fuel entering from the fuel inlet passage 48 connected to the other end of the injection pipe increases, the needle valve 39 is initially pressed by the first spring 42, so the needle valve 39 does not open. When the pressure rises above the set pressure (first valve opening pressure Po+) of the first spring 42, the needle moves against the first spring 42 until the first bushing rod part 43 comes into contact with the second bushing rod part 45. Valve 39 lifts (lift value NL+). When it rises to this point, the setting force of the second spring 47 comes to act on the needle valve 39, so after that the predetermined pressure (second valve opening pressure P.t)
The needle valve 39 does not rise until the second valve opening pressure is reached, and the needle valve 39 rises to full lift) NL, . . . against the first and second springs 42 and 47.

In addition, as another embodiment of the fuel injection valve 31, a central plunger type shown in FIG. 7 may also be used, although this is also a known one.

This is because a piston 49 that receives the pressure of fuel from the fuel inlet passage 48 is slidably provided in the valve holder 36 instead of the second spring of the two-stage spring type described above, and a piston 49 that extends downward from the piston 49 is provided. The bushing rod portion 50 of No. 3 is inserted so as to have a distance N L + from the first spring receiver 43, and the bushing rod portion 50 of the piston 4
The second valve opening pressure P is determined by the difference in pressure receiving area between the pressure stage 9 and the pressure stage in the nozzle 37 (not shown). 2 is set.

Thus, in the fuel injection pump l, when the drive shaft 4 rotates in response to the driving force from the diesel engine, the rotational motion is converted into the rotational reciprocating motion of the plunger 8 via the cam device 18, and the plunger 8 It reciprocates inside the cylinder 7 while rotating.

During the suction stroke in which the plunger 8 retreats, any one of the suction groups 10 and the suction passage 11 are aligned, and fuel is sucked from the suction space 2 into the high pressure chamber 9 via the suction passage 11 and the suction group 10, and then the suction group 10 and the suction passage 11 are cut off. Then, during the next discharge stroke in which the plunger 8 moves forward, as the stroke of the plunger 8 increases, the volume of the high pressure chamber 9 decreases and the pressure of the fuel at the high pressure 9 increases.
and any one of the pressure feeding passages 12 are aligned, so that
The valve body 28 of the delivery valve device 25 opens and fuel is delivered.

As the stroke of the plunger 8 further increases, the spill boat 16 finally comes off the control sleeve 17 and opens into the suction space 2, and the fuel in the high pressure chamber 9 flows into the suction space 2 through the vertical hole 14 of the plunger 8 and the spill boat 16. The fuel is refluxed, and the pressure of the fuel in the high-pressure chamber 9 is rapidly reduced. As a result, the valve body 28 of the delivery valve device 25 seats on the valve seat body 25, and fuel delivery is completed and preparations are made for the next injection. It becomes like this.

As mentioned above, the delivery valve device 25 has an Angleich mechanism, the characteristics of which are shown in FIG. Therefore, when the rotational speed N of the diesel engine is low, such as during idling, the residual pressure Pr in the injection pipe 30 is high and the first valve opening pressure P is reached. In order to obtain I, it is sufficient to increase the upper limit by ΔPr+, and the stroke of the plunger 8 corresponding to this is CLl in FIG. Therefore, injection starts when the cam rotation angle θ is el, and the cam rotation angle θ2 is determined by the position of the control sleeve 17 according to the load of the diesel engine.
The injection ends at the time of . In this case, the load is low so it is quick. ), the cam speed at this time is vl, so the injection rate is correspondingly low.

Therefore, as shown in FIG. 8, in the fuel injection valve 31, the nozzle pressure P8 is higher than the first valve opening pressure Pot, but the second valve opening pressure P is higher than the first valve opening pressure Pot. It will be lower than 2.

Therefore, the needle valve 39 is fixed at the NLI lift, resulting in stable injection.

On the other hand, when the engine speed N is high, the residual pressure P in the injection pipe 30 is low, and in order to obtain the first valve opening pressure POI, ΔPr
z (>ΔPr,), and the corresponding stroke of the plunger 8 is CLz (>CL,). Therefore, the injection starts when the cam rotation angle θ becomes θ3, and ends at the cam rotation angle θ4, which is also determined by the position of the control sleeve 17. In this case, it is slow because the load is high. ), the cam speed during this period is high, including the maximum speed V4, so the injection rate is also high, and fuel is injected from the fuel injection valve 31 at high speed.

Therefore, in the fuel injection valve 31, the nozzle pressure PM is the second valve opening pressure P. 2 or more, the needle valve 39 is fully lifted, and stable injection is also performed.

In this way, at high speed, the injection timing (injection start) is delayed, but this can be corrected by the timer 24.

In the above embodiment, the cam device uses an end cam, but is not limited to this, and may also use a front cam or an inner cam.
The type of injection pump is not limited to a distribution type, but may be a so-called line type.

Further, in the above embodiment, the delivery valve device of the fuel injection pump is provided with an Angleich mechanism, but for example,
0-247049, a known equal pressure valve may be used to maintain the residual pressure in the injection pipe at a high level at all times. When this equal pressure valve is used, only the front stage of the cam device is used due to the small injection amount at low speeds, and the residual pressure in the injection pipe does not decrease at high speeds, but as the injection amount increases, the cam device The high speed region is used to allow high injection rates.

(Effects of the Invention) As described above, according to the present invention, since a cam device having a low speed region in the front stage and a high speed region in the rear stage is used,
At low speeds, injection starts while the stroke of the plunger is small and uses the low speed region of the cam to achieve a low injection rate, and at high speeds it is possible to maintain the high injection rate as before, ensuring horsepower at high speeds while reducing the injection rate at low speeds. It is possible to reduce knocking noise. In addition, we used a fuel injection valve with a two-stage valve opening pressure, and at low speeds, the pressure of the fuel delivered from the fuel injection pump was set between the first valve opening pressure and the second valve opening pressure, so at low speeds The needle valve is fixed at a position corresponding to the first valve opening pressure, so that stable injection can be obtained over the entire area.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view showing the main parts of the delivery valve device used in the above, and Fig. 3 is a perspective view showing the valve body of the delivery valve device used in the above. , FIG. 4 is a cam diagram of the cam device used in the above embodiment, FIG. 5 is a characteristic diagram showing the rotational speed of the fuel injection device and the residual pressure of the injection pipe in the above embodiment, and FIG. is a sectional view of the fuel injection valve used in the above embodiment, FIG. 7 is a sectional view of a fuel injection valve of another embodiment, and FIG. 8 is a fuel injection valve having a two-stage valve opening pressure mechanism according to the present invention. Figure 9 is a characteristic diagram showing the nozzle pressure and needle valve lift versus cam rotation angle when a normal fuel injection valve is used. It is. DESCRIPTION OF SYMBOLS 1... Fuel injection pump, 4... Drive shaft, 6... Pressure mechanism, 7... Cylinder, 8... Plunger, 18
...Cam device, 25... Delivery valve device, 31... Fuel injection valve, 39... Needle valve, 42... First spring, 47... Second spring, 48...・Fuel inlet passage, 49...piston. Figure 4, -m--゛-, Cam rotation angle (e) - Figure 5 Rotation speed (N) → Figure 6 Figure 7 Figure 8 Cam rotation angle (θ) → Figure 9 Cam rotation angle ( e) →

Claims (3)

[Claims] 1. In a fuel injection device that includes a fuel injection pump and a fuel injection valve that injects fuel sent from the fuel injection pump, the fuel injection pump includes a drive shaft, a cylinder, and a plunger fitted into the cylinder. a pressure mechanism, a cam device provided between a plunger of the pressure mechanism and the drive shaft for converting rotation of the drive shaft into reciprocating motion and transmitting the same to the plunger; and a delivery valve device provided in a pressure feeding passage through which fuel is discharged, and the cam device is provided with a cam characteristic in which a low speed region is at the front stage and a high speed region at the rear stage with respect to the cam rotation angle, The fuel injection valve is provided with a two-stage valve opening pressure mechanism that is set so that the delivery pressure of the fuel injection pump in a low speed region is between a first valve opening pressure and a second valve opening pressure. Characteristic fuel injection device. 2. The fuel injection valve according to claim 1, wherein the fuel injection valve has a first spring that sets a first valve opening pressure and a second spring that sets a second valve opening pressure. Device. 3. The fuel injection valve has a first spring that sets a first valve opening pressure, and a piston that receives pressure from a fuel inlet passage to set a second valve opening pressure. The fuel injection device according to item 1.