JP3037398B2 - Distribution type fuel injection pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable prestroke type distribution type fuel injection pump.

[Prior Art] Generally, in a distribution type fuel injection pump, a fuel injection rate is adjusted by changing a pre-stroke, and the injection rate has a great effect on the performance of a diesel engine. Therefore, it is important to make the print stroke variable, and various types of prestroke variable type distribution type fuel injection pumps have been conventionally proposed. For example, JP-A-61-187959, JP-A-61-6946.
No. 5, JP-A-62-21470, JP-A-61-192534, and JP-A-1-95570.

[Problem to be Solved by the Invention] However, each of the distribution type fuel injection pumps described in the above publication requires new parts in order to make the prestroke variable. For this reason, there have been problems such as an increase in the price of the pump and an increase in the size of the pump.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is possible to make the pre-stroke variable, and it is also possible to make the pre-stroke variable type distribution fuel without increasing the price and increasing the size. It is an object to provide an injection pump.

Means for Solving the Problems In order to achieve the above object, the present invention provides a plunger rotatably and reciprocally provided in a barrel hole and pressurizing fuel in a fuel pressurizing chamber during forward movement. And a timer mechanism for delaying or advancing the reciprocating timing of the plunger according to the pressure of the pump chamber. In the distribution type fuel injection pump, a return port communicating with the pump chamber is opened on the inner peripheral surface of the barrel hole. At the same time, a return slit communicating with the fuel pressurizing chamber and facing / separating from the return port with the rotation of the plunger is formed on the outer peripheral surface of the plunger. Are arranged so as to change from the opposed state to the separated state at the beginning of the forward movement of the plunger.

[Operation] In the initial stage of the forward movement of the plunger, when the return port and the return slit face each other, the fuel in the fuel pressurized chamber pressurized by the plunger flows into the pump chamber through the return slit and the return port. And therefore
In a state where the return port and the return slit face each other,
Even if the plunger moves forward, fuel pressurization is not substantially performed. That is, no fuel injection is performed. Thereafter, when the return port and the return slit are separated from each other with the rotation of the plunger, the fuel in the fuel pressurizing chamber does not flow out to the pump chamber, and the substantial pressurization of the fuel by the plunger starts.

As is apparent from the above description, the forward stroke of the plunger from the start of the forward movement of the plunger until the return port and the return slit are switched to the separated state is the pre-stroke.

Here, the cam angle at the time when the return port and the return slit are switched from the opposed state to the separated state is constant irrespective of whether the timer mechanism is in the advanced or retarded state.

On the other hand, the forward movement start timing of the plunger is advanced when the timer is advanced, and is delayed when the timer is delayed. Therefore, when the timer is advanced, the rotation angle (cam angle) of the plunger from when the plunger starts moving forward to when the return port and the return slit are switched to the separated state increases. As a result, the pre-stroke increases. Conversely, when the timer is retarded, the cam angle between the time when the plunger starts moving forward and the time when the return port and the return slit are switched to the separated state becomes smaller. As a result, the pre-stroke is reduced.

[Embodiment] FIGS. 1 to 5 show an embodiment of the present invention.
This will be described with reference to the drawings.

FIG. 1 shows a distribution type fuel injection pump according to the present invention, and reference numeral 1 denotes a pump housing. Inside the pump housing 1, a pump chamber 2 filled with fuel is formed. The fuel in the pump chamber 2 is supplied from a fuel tank 5 by a feed pump 4 rotated and driven by a drive shaft 3, and the pressure in the pump chamber 2 is equal to the rotation speed of the drive shaft 3, that is, the rotation speed of the diesel engine. It changes according to.

A barrel 6 is fixed to the side wall of the pump housing 1 with its axis oriented in the horizontal direction. The barrel 6 has a barrel hole 6a extending from one end face facing the pump chamber 2 toward the other end face. This barrel hole 6a
, One end of the plunger 7 is slidably and rotatably inserted. The other end of the plunger 7 projects into the pump chamber 2, and a cam disk 8 is provided integrally therewith. The cam disk 8 is provided on the drive shaft 3
Are connected so as to be relatively movable in the axial direction and to rotate integrally. In addition, the cam disk 8 includes a spring 9
, Butted against the roller 10a of the roller holder 10. Therefore, when the drive shaft 3 rotates, the cam disk 8 reciprocates, and the plunger 7 reciprocates.

It should be noted that the forward movement speed of the plunger 7 by the cam disk 8 is low at the beginning of the forward movement and becomes high after the middle of the forward movement as is apparent from FIG.

In the above configuration, when the plunger 7 moves forward (moves to the right in FIG. 1), unless the return port 6d and the return slit 7f described later are formed, the fuel in the fuel pressurizing chamber 11 is simultaneously discharged. Pressurized. The pressurized fuel is delivered through a vertical hole 7a, a horizontal hole 7b and an outlet slit 7c formed in the plunger 7, an outlet port 6b formed in the barrel 6, and a discharge passage 1a formed in the pump housing 1. It is pumped to the valve 12 and from there to a fuel injection nozzle (not shown).
Then, the fuel is injected into the combustion chamber of the engine.

During the forward movement of plunger 7, cut-off port
When 7d is exposed from the control sleep 13 to the pump chamber 2, the fuel in the fuel pressurizing chamber 11 flows into the pump chamber 2 through the vertical hole 7a and the cutoff port 7d. by this,
The substantial pressurization of the fuel by the plunger 7 ends, and the fuel injection ends.

The position of the control sleep 13 is controlled by the tension of the governor spring 15 adjusted by the control lever 14 and the governor sleep 17 of the fly weight 16 which opens and closes as the engine speed (speed of the drive shaft 3) increases and decreases. Is adjusted via the governor lever assembly 18, and the position of the control sleeve 13 adjusts the fuel injection amount.

When the plunger 7 moves back, the fuel in the pump chamber 2 is sucked and introduced into the fuel pressurizing chamber 11 through the inflow passage 1b of the pump housing 1, the inlet port 6c of the barrel 6, and the inlet slit 7e of the plunger 7. You.

As is well known, the outlet port 6b and the inlet slit 7e are formed as many as the number of cylinders of the engine (four in this embodiment), and are arranged at equal intervals in the circumferential direction. On the other hand, one outlet slit 7c and one inlet port 6c are formed.

A timer mechanism 19 is provided at the lower end of the pump housing 1.
(FIG. 1 shows an actual timer mechanism 19).
It is shown rotated 90 °). This timer mechanism 19
Is configured similarly to the well-known one, and has a cylinder bore 19
A timer piston 19b is provided slidably on a. The inside of the cylinder hole 19a is divided into a high-pressure chamber 19c and a low-pressure chamber 19d by the timer piston 19b. High pressure chamber
19c is communicated with the pump chamber 2 through a communication hole 19e formed in the timer piston 19b. Meanwhile, low pressure chamber
In 19d, the ball piston 19b is moved from the low pressure chamber 19d side to the high pressure chamber 19c.
A timer spring 19f biasing toward the side is provided.

In the above configuration, when the pressure in the pump chamber 2 increases with an increase in the engine speed, the pressure in the high-pressure chamber 19c increases. Therefore, the timer piston 19b is moved from the high-pressure chamber 19c side against the urging force of the timer spring 19f. It is displaced to the low pressure chamber 19d side. Conversely, when the engine speed decreases, the timer piston 19b is displaced from the low-pressure chamber 19d toward the high-pressure chamber 19c. The displacement of the timer piston 19b is transmitted to the roller holder 10 via the rod 20, and when the timer piston 19b is displaced toward the low-pressure chamber 19d, the roller holder 10 is rotated in the opposite direction to the rotation direction of the cam disk 8. It is rotationally displaced in the direction and is in the advanced angle state. As a result, the forward movement start timing of the peranger 7 is advanced. Conversely, when the timer piston 19b is displaced toward the high pressure chamber 19c, the roller holder
10 is rotationally displaced in the same direction as the rotational direction of the cam disk 8,
Becomes retarded. As a result, the forward movement start timing of the plunger 7 is delayed.

FIG. 4 shows the lift amounts of the plunger 7 at the time of maximum advance, middle advance and maximum retard, respectively, by curves C, D, and E.
Are denoted by, the curves C, D, respectively theta ₁ cam angle is at the forward movement start of _E, theta _2, has become theta _3. Here, a _{Θ 1 <Θ 2 <Θ 3} .

The above configuration is the same as that of a conventional distribution type fuel injection pump, but in the distribution type fuel injection pump of the present invention, a return port 6d and a return slit 7f are formed to obtain a prestroke.

The same number of return ports 6 d as the number of cylinders of the engine are formed in the barrel 6. One end of each return port 6d is a barrel 6
The other end is opened to the inner peripheral surface of the cylinder hole 6a. The openings of the return port 6d on the inner circumferential surface of the cylinder 6a are located at the same position in the axial direction of the cylinder hole 6a, but are spaced at equal intervals in the circumferential direction. In addition,
In this embodiment, as apparent from FIGS. 2 and 3, each return port 6d is arranged at the same position in the circumferential direction of the outlet port 6b and the barrel 6.

On the other hand, the return slit 7f is
One is formed. The return slit 7f is communicated with the vertical hole 7a through the horizontal hole 7g, and is further communicated with the fuel pressurizing chamber 11.

The return port 6d and the return slit 7f are arranged so as to oppose and separate from each other as the plunger 7 rotates. In addition, the switching from the facing state to the separated state is performed at an early stage of the forward movement of the plunger 7. In particular, in this embodiment, the switching from the opposed state to the separated state is performed at the timing of starting the forward movement of the plunger 7 at the maximum retardation (cam angle # ₃ ).

In the distribution type fuel injection pump having the above-described configuration, in a state where the return port 6d and the return slit 7f face each other, even if the plunger 7 starts to move forward, the fuel in the fuel pressurizing chamber 11 passes through the vertical hole 7a and the horizontal hole 7a. Hole 7g, return slit 7f and return port
It flows out into the pump chamber 2 through 6d. Therefore, no fuel pressurization is performed. Return port 6d and return slit
When 7f is switched from the opposed state to the separated state, substantial pressurization of the fuel by the plunger 7 starts. As is apparent from this content, the distance that the plunger 7 moves forward between the time when the plunger 7 starts moving forward and the time when the return port 6d and the return slit 7f are switched from the opposed state to the separated state is the pre-stroke. .

Here, the cam angle when the return port 6d and the return slit 7f are switched from the opposed state to the separated state is always constant regardless of whether the timer mechanism is in the advanced state or the retarded state. In this embodiment, the cam angle at the time of switching to the separated state is $ ₃ .

On the other hand, as shown in FIG. 4, the forward movement start timing of the plunger 7 is advanced when the timer mechanism 19 is advanced, and is delayed when the timer mechanism 19 is delayed. Therefore, when the timer mechanism 19 is in the advanced state, the cam angle from the start of the forward movement of the plunger 7 to the time when the return port 6d and the return slit 7f are switched to the separated state increases. Therefore, the pre-stroke increases. Conversely, the timer mechanism
When 19 is in the retarded state, the pre-stroke decreases.

In this embodiment, a pre-stroke distance PS ₁ which plunger 7 is forward movement at the maximum advance angle between the cam angle (Θ ₃ -Θ _1), a plunger between the cam angle (Θ ₃ -Θ ₂₎ The forward travel distance PS ₂ is the pre-stroke at the time of intermediate advance. At the time of maximum retardation, the forward movement start time of the plunger 7, the return port 6d and the return slit 7f
The timing of switching to the separated state is the cam angle カ ム
Since there is a match at ₃ , there is no pre-stroke, and the fuel is pressurized at the same time that the plunger 7 starts going forward.

As described above, in this distribution type fuel injection pump, by forming the return port 6d and the return slit 7f, the pre-stroke can be changed according to the advance amount of the timer mechanism 19. In addition, regarding this pre-stroke, the switching timing of the return port 6d and the return slit 7f from the opposed state to the separated state is determined by the model of the distribution type fuel injection pump or the model of the diesel engine using the distribution type fuel injection pump. A desired pre-stroke amount can be obtained by appropriately changing the pre-stroke amount. For example, the fourth
As shown by the one-dot chain line in the figure, if the switching time to the separated state (cam angle # ₄ ) is made earlier than the forward movement start time of the plunger 7 at the maximum retardation, as shown by the one-dot chain line in FIG. It is possible to obtain a pre-stroke from a state where the advance is slightly advanced from the maximum retard. Also, as shown by the broken line in FIG.
If the timing of switching to the separated state (cam angle # ₅ ) is later than the timing of starting the forward movement of the plunger 7 at the time of the maximum retard, a predetermined peri-stroke can be obtained from the time of the maximum retard.

Further, only the return port 6d and the return slit 7f are formed to obtain the pre-stroke, and no new parts are required. Therefore, it is possible to prevent the distribution type fuel injection pump from increasing in size or from increasing production costs.

Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.

For example, in the above embodiment, the return port 6d is arranged at the same position as the discharge port 6b in the circumferential direction of the barrel 6, but may be arranged at a different position. In short, the return port 6d and the return slit 7f may be arranged so that the switching from the opposed state to the separated state is performed in the initial stage of the forward movement of the plunger 7.

In the above embodiment, the return port 6d is connected to 4
(Same number as the number of engine cylinders) and return slit
Although one piece 7f is formed, only one return port 6d may be formed and four return slits 7f may be formed. in this case,
Of course, the four return slits 7f should be arranged at equal intervals in the circumferential direction of the plunger 7.

Further, in the above embodiment, the pre-stroke amount is configured to increase as the engine speed increases. For example, a timer mechanism that retards as the pressure in the pump chamber 2 increases. Is used, the pre-stroke amount can be configured to decrease as the engine speed increases.

[Effects of the Invention] As described above, according to the distribution type fuel injection pump of the present invention, the return port and the return slit that switch from the opposed state to the separated state at the beginning of the forward movement of the plunger are formed. Not only can the pre-stroke be changed, but also no new parts are required, so that the distribution-type fuel injection pump can be prevented from increasing in size or increasing production costs. An effect is obtained such that the pre-stroke can be continuously changed according to the advance amount.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, FIG.
FIG. 3 is an enlarged sectional view taken along arrows II-II and III-III of FIG. 1, and FIG. 4 is a lift characteristic of a plunger, a change characteristic of a communication area between a discharge port and a discharge slit, and a return port. FIG. 5 is a view showing a change characteristic of a communication area with a return slit, and FIG. 5 is a view showing a relationship between an advance amount and a pre-stroke. 1. Pump housing, 2. Pump room, 6. Barrel, 6a
... Barrel hole, 6d ... Return port, 7 ... Plunger, 7f ... Return slit, 11 ... Fuel pressurizing chamber, 19 ... Timer mechanism.

Claims (1)

(57) [Claims] 1. A plunger rotatably and reciprocally provided in a barrel hole for pressurizing fuel in a fuel pressurizing chamber during forward movement, and a reciprocating timing of the plunger is delayed according to a pressure of a pump chamber. In a distribution type fuel injection pump having a timer mechanism for advancing an angle, a return port communicating with a pump chamber is opened on an inner peripheral surface of the barrel hole, and an outer peripheral surface of the plunger is communicated with the fuel pressurizing chamber. And a return slit which faces and separates from the return port with the rotation of the plunger, and arranges the return port and the return slit such that they change from the opposed state to the separated state at the beginning of the forward movement of the plunger. A distribution type fuel injection pump characterized by being provided.