JPH041320Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement of a fuel injection pump having a speed timer mechanism that adjusts the amount of advance of fuel injection according to the engine speed.

(Prior Art) As shown in Japanese Utility Model Application No. 57-78740, a fuel injection pump is generally provided with a speed timer mechanism for adjusting the fuel injection advance amount according to the engine rotation speed. This speed timer mechanism is defined by a timer piston that is slidably inserted into a cylinder formed in a housing, and one end surface of the timer piston, and is supplied with hydraulic pressure that increases according to the pump rotation speed. The timer piston is equipped with a high pressure chamber and a return spring that urges the timer piston toward the high pressure chamber, and when the engine speed increases, that is, the pump speed increases, the oil pressure supplied to the high pressure chamber increases, and the timer piston moves to the return spring. , and the injection advance amount is set in accordance with this displacement position. The manner in which the injection advance amount changes with respect to the engine speed is linearly changed.

By the way, the relationship between the injection advance amount and the engine speed is not necessarily linear, but is generally different between a low speed range and a high speed range. In other words, in the pre-chamber type, as shown in Figure 4, it is desirable that the degree of change in the injection advance amount with respect to the engine speed be relatively small in the low speed range in order to reduce _NO In view of smoke, it is desirable that the degree of change be relatively large in the high rotation range. In addition, in the case of a direct injection type, in order to deal with the momentum of the swirl that changes depending on the engine speed, the degree of change is determined as shown in Fig. 5 from the relationship of fuel efficiency, output, harmful components, etc. It is hoped that the relationship will be the opposite of that of the subchamber type.

In this way, although the requirements for the degree of change in the injection advance amount relative to the engine speed differ between the low engine speed range and the high engine speed range, conventional speed timer mechanisms cannot meet this demand. ,
Some kind of countermeasure is desired. Of course, it is also possible to electronically control the injection advance amount using a separate electromagnetic actuator, but this would be extremely expensive.

(Purpose of the invention) The present invention was developed in consideration of the above-mentioned circumstances, and by devising a conventional mechanical speed timer mechanism, the degree of change in the amount of injection advance with respect to the engine speed can be determined by the engine speed. It is an object of the present invention to provide a fuel injection pump that can be made different depending on the rotation range.

(Structure of the invention) In order to achieve the above-mentioned purpose, the present invention has the following structure. That is, a timer piston is slidably inserted into a cylinder formed in the housing, and a high pressure chamber is defined on one end surface of the timer piston and is supplied with hydraulic pressure that increases according to the pump rotation speed. A fuel injection pump having a speed timer mechanism including a return spring that urges the timer piston toward the high pressure chamber, wherein the high pressure chamber is disposed between an outer circumferential wall of the timer piston and an inner circumferential wall of the cylinder. A relief passage for relief to the low pressure side is formed, and the timer piston is configured to function as a valve body for communicating and cutting off the high pressure chamber with the low pressure side via the relief passage. The high pressure chamber is configured to communicate with the low pressure side via the relief passage only when the piston is in a predetermined movement region.

With this configuration, when the high pressure chamber is not communicated with the low pressure side via the relief passage, the degree of change in the injection advance amount with respect to the engine speed becomes relatively large. In a state where the high pressure chamber is communicated with the low pressure side via the high pressure chamber, the degree of change in the amount of injection advance with respect to the engine speed becomes relatively small. The timing at which the high pressure chamber communicates with the low pressure side via the relief passage can be set in an appropriate engine rotation range by taking into account the displacement position of the timer piston, which changes depending on the engine rotation speed. Therefore, it is possible to obtain a device that can be used as a direct injection type or a subchamber type.

(Example) Hereinafter, an example in which the present invention is applied to a four-cylinder diesel engine will be described based on the attached drawings.

In FIG. 1, A indicates a so-called VE type distribution type fuel injection pump. To explain this, a plunger 3 is rotatably and slidably inserted into a barrel 2 integrated into a housing 1. has been done. Further, a drive shaft 4 is rotatably held in the housing 1 in series with the plunger 3, and the drive shaft 4 supports a vane type pump 5 in addition to the plunger 3.
A governor mechanism 6, which will be described later, is rotatably driven. Of course, the drive shaft 4 is
It is rotationally driven by an engine (not shown).

A fuel storage chamber B filled with fuel discharged from the pump 5 is formed in the housing 1, and this fuel storage chamber B is opened into the barrel 2 through an intake passage 8. Inside this barrel 2, a pressure chamber D is defined by a plunger 3, and on the outer periphery of the tip of the plunger 3, four intake slits 9 corresponding to the number of cylinders are provided at intervals in the circumferential direction. When the intake slit 9 is aligned with the intake passage 8 according to the rotational and sliding position of the plunger 3, fuel is supplied to the pressure chamber D. Further, a discharge passage 10 that is always open to the pressure chamber D is formed in the plunger 3, and one discharge port 11 that is continuous with the discharge passage 10 and opens on the side surface of the plunger 3 is formed. Four distribution ports 12 corresponding to the number of cylinders are opened on the circumferential surface of the barrel 2 at intervals in the circumferential direction, and the discharge ports 11 are distributed according to the rotation and sliding position of the plunger 3. Mouth 12
It is now being communicated sequentially. Of course, each distribution port 12 is connected to a fuel injection nozzle provided in each cylinder of the engine through a connection port 13 through a pipe (not shown).

With the above-described configuration, the plunger 3
is the pressure chamber D depending on its rotation and sliding.
(expansion of the pressure chamber D and communication of the intake slit 9 with the suction passage 8) and pressure feeding of fuel within the pressure chamber D (communication between the discharge port 11 and the distribution port 12), Fuel is pumped to the fuel injection nozzles in a predetermined order. In order to set the sliding position according to the rotational position of the plunger 3, a cam plate 15 is integrated with the plunger 3, and four cams corresponding to the number of cylinders protruding from the cam plate 15 are provided. By sequentially abutting the surface 15a against the roller 16, it is possible to assume a predetermined sliding position according to its rotational position. This roller 16 is slightly displaced in the circumferential direction of the cam plate 15 via a rod 19 by a timer piston 18 of a speed timer mechanism 17 that is displaced in response to fuel pressure from the pump 5, as will be described later. As a result, the fuel injection timing is advanced according to the engine speed.

Note that the speed timer mechanism 17 and the pump 5
For ease of understanding, in FIG. 1, the direction is deviated by 90° from the plunger 3, as is commonly done.

To adjust the amount of fuel to the fuel injection nozzle, a control sleeve 20 that is slidably fitted around the outer circumference of the plunger 3, a lever mechanism 21, a spring 2, etc.
2 by operating the control lever 23. That is, plunger 3
is formed with a relief port 24 that is continuous with the discharge passage 10 and opens into the fuel storage chamber B, and the opening timing of this relief port 24 (the effective stroke of the plunger 3) determines the relative displacement of the control sleeve 20 with respect to the plunger 3. Adjusted by Also, this control sleeve 2
The position of 0 is also adjusted by the governor mechanism 6 described above, and therefore the gear 25 that meshes with the gear 25A integrated with the drive shaft 4.
A flyweight 26 is provided to rotate integrally with respect to B, and the flyweight 26 corresponds to the engine rotation speed, that is, the rotation speed of the drive shaft 4.
The displacement amount of 6 is the shaft 27 holding the gear 25B.
The signal is transmitted to the lever mechanism 21 via a sleeve 28 which is slidable.
Note that the lever mechanism 21 is held by a throttle plate 29 that adjusts the amount of fuel supplied to the intake passage 8. Further, the suction passage 8 is opened and closed by an electromagnetic cut-off valve 30.

Since the configuration of the above-mentioned parts is already known, further detailed explanation will be omitted. Next, the part of the speed timer mechanism 17 which is a characteristic part of the present invention will be explained.

First, FIG. 2 shows an embodiment for use as a sub-chamber type device having the characteristics shown in FIG. 4. The speed timer mechanism 17 includes a cylinder 31 formed in the housing 1, and a timer piston 18 is slidably inserted into the cylinder 31. This timer piston 18
Therefore, inside the cylinder 31, the timer piston 1
High pressure chamber E on one end surface of 8 (right end side in Figure 2)
However, a low pressure chamber F is also defined on the other end surface side.
High-pressure oil pressure from the fuel storage chamber B is constantly introduced into the high-pressure chamber E through an inflow path 32 formed in the timer piston 18. Also,
As shown in FIG.
3, it is constantly connected to the low pressure side, that is, the inlet side of the pump 5. The timer piston 18 is urged toward the high pressure chamber E (to the right in FIG. 2) by a return spring 34 disposed within the low pressure chamber F.

The outer peripheral wall of the timer piston 18 and the cylinder 3
A relief passage 35 extending in the axial direction of the timer piston 18 is formed between the cylinder 31 and the inner peripheral wall of the cylinder 31 by forming a groove in the inner peripheral wall of the cylinder 31 . This relief passage 35 is made shorter than the entire length of the outer circumferential wall of the timer piston 35, and when the timer piston 18 is at the right stroke end in FIG.
are positioned inward from each end of the timer piston 18. One end 35a side of the relief passage 35 is always communicated with the high pressure chamber E through a communication port 36 formed in the timer piston 18, regardless of the displacement position of the timer piston 18. The other end 35b side of the relief passage 35 is communicated with the low pressure chamber F via a communication port 37 formed in the timer piston 18. When the relief passage 35 is stroked to the left by l ₁ , it is closed by the housing 1, and communication of the relief passage 35 with the low pressure chamber F is cut off.

Note that 38 and 39 in FIG. 2 are cover members that close the openings at both ends of the cylinder 31 and substantially constitute a part of the housing 1.

In the above configuration, the pump 5 is rotationally driven by the engine, and fuel is supplied to the high pressure chamber E at a pressure corresponding to the rotation speed of the pump 5, that is, the engine rotation speed. Therefore, the timer piston 18 is
It is displaced to the left in FIG. 2 against the return spring 34 to a position corresponding to this fuel pressure (engine speed), and an injection advance amount is set according to this displaced position.

Here, in the low rotation range of the engine, the fuel pressure supplied to the high pressure chamber E is small, so the timer piston 18 only makes a stroke displacement of less than _l1 to the left from its return position, and the high pressure chamber E It is communicated with the low pressure side via the passage 35. Therefore, the degree of change in the injection advance amount with respect to the engine speed is relatively small as shown in the left side of FIG. ₄ NE1. From this state, when the engine speed becomes higher than NE ₁ , the timer piston 18 moves more than l ₁ stroke to the left from its return position, so that the communication between the high pressure chamber E and the low pressure chamber F via the relief passage 35 is interrupted. will be cut off.
As a result, as shown on the right side of FIG. 4 NE ₁ , the degree of change in the injection advance amount with respect to the engine speed becomes large. In this way, in the low engine speed range and the high engine speed range, the degree of change in the amount of injection advance with respect to the engine speed changes with NE ₁ as the boundary, making it suitable for the pre-chamber type. be done.

Figure 3 shows an example of a direct injection type that has the characteristics shown in Figure 5, and the same components as those in Figure 2 are given the same reference numerals. Therefore, the explanation will be omitted. In this embodiment, the low pressure chamber F and the relief passage 35 are
The communication port 37 allows constant communication regardless of the displacement position of the timer piston 18. Further, a communication passage 36 for communicating the high pressure chamber E and the relief passage 35 is connected to the timer piston 18.
The relief passage 35 is moved only when the stroke is displaced by l ₂ or more against the return spring 34.
It is formed so that the high pressure chamber E and the high pressure chamber E are communicated with each other.
With this configuration, as is already clear from the explanation with reference to FIG.
Figure NE ₂ or less (stroke displacement of the timer piston 18 is l ₂ or less), the degree of change in the injection advance amount _with respect to the engine speed is relatively large; ₂ or higher), this degree of change is considered to be relatively small.

In the above embodiment, the relief passage 35 is formed in the form of a groove on the inner peripheral wall of the cylinder 31, but it may be formed in the outer peripheral wall of the timer piston 18.

(Effects of the invention) As is clear from the above, the invention has the following effects:
By effectively utilizing the conventional mechanical speed timer mechanism as is, the degree of change in the injection advance amount relative to the engine speed can be optimally set according to the engine speed.

[Brief explanation of the drawing]

FIG. 1 is an overall sectional view showing an example of a fuel injection pump to which the present invention is applied. FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1, showing an embodiment when used as an auxiliary chamber type. FIG. 3 is an enlarged sectional view of a main part corresponding to FIG. 2, showing an embodiment when used as a direct injection type. FIG. 4 is a diagram showing the required characteristics for the sub-chamber type. FIG. 5 is a diagram showing required characteristics in a direct injection type. A...Fuel injection pump, B...Fuel storage chamber, 1
... Housing, 17 ... Speed timer mechanism,
18...Timer piston, 31...Cylinder, 3
2...Inflow path, 33...Communication path, 34...Return spring, 35...Relief path, 36,3
7...Communication port.

Claims (1)

[Claims for Utility Model Registration] A timer piston that is slidably inserted into a cylinder formed in a housing, and a hydraulic pressure that is defined on one end surface of the timer piston and increases in accordance with the pump rotation speed is supplied. In a fuel injection pump having a speed timer mechanism, the speed timer mechanism includes a high pressure chamber that presses the timer piston toward the high pressure chamber, and a return spring that biases the timer piston toward the high pressure chamber, the fuel injection pump having the following structure: between an outer circumferential wall of the timer piston and an inner circumferential wall of the cylinder. A relief passage for relieving the high pressure chamber to the low pressure side is formed, and the timer piston functions as a valve body for communicating and blocking the high pressure chamber with the low pressure side via the relief passage. A fuel injection pump characterized in that the high pressure chamber is communicated with the low pressure side via the relief passage only when the timer piston is in a predetermined movement range.