JPH0777131A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To improve the increasing rate of injection pressure and the injection ratio of fuel on the way of injection of fuel, and reduce easily a harmful material included in exhaust gas with a simple structure. CONSTITUTION:When rise of a plunger 13 is started and a feed hole 12a is closed by the outer wall of the plunger 13, pressurizing of fuel in first and second pressurizing chambers 21, 22 is started. When the capacity of the first pressurizing chamber 21 is set as V1 and the capacity of the second pressurizing chamber 22 is set as V2, the relation of a pressurized fuel capacity is V1+V2. When pressurized fuel pressure is overcame energization force of a compressing coil spring 34 and a valve 33 is lifted, feed of fuel is started toward a fuel injection valve. Furthermore, when the plunger 13 is raised, and the fuel passage 14e of a spacer 14 is closed by the inner wall of the plunger 13, the capacity of pressurized fuel becomes the capacity V1 of the first pressurizing chamber 21. Therefore, the increasing rate of fuel injection pressure is raised on the way of fuel injection, and the increasing rate of an injection ratio is increased in association with its increase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for a diesel engine, and more particularly to a structure of a pressurizing chamber during a pressure feeding process by a plunger.

[0002]

2. Description of the Related Art Conventionally, a fuel injection pump shown in FIG. 7 is known as a fuel injection pump for supplying high-pressure fuel to a fuel injection valve. The cylinder 42 is fixed to the housing 41 with bolts 45, and the plunger 43 is housed inside the cylinder 42 so as to be slidable in the axial direction. Pressure chamber 61 formed by cylinder 42, plunger 43, and delivery valve 50 and fuel chamber 41 formed in housing 41
A feed hole 42a communicating with a is formed in the cylinder 42. The delivery valve 50 has a plunger 4
3 is fixed in the cylinder 42 on the fuel downstream side. The valve seat 52 is locked to the shoulder portion 42 b of the cylinder 42 by screwing the holder 54 to the cylinder 42. The valve 51 is biased to the valve seat 52 by a compression coil spring 53 whose one end is fixed to a holder 54.

In the fuel injection pump shown in FIG. 7, the plunger 43 starts to move up by the driving force of a cam shaft (not shown). When the upper end surface 43a of the plunger 43 closes the feed hole 42a, the fuel in the pressurizing chamber 61 is pressurized, and when the pressure of the pressurized fuel overcomes the biasing force of the compression coil spring 53, the valve 51 is lifted. Fuel is supplied to the fuel injection valve. Plunger 43 rises further,
When the plunger lead 43b communicates with the feed hole 42a, the pressure feeding process ends. Since the volume of the pressurizing chamber 61 decreases and increases at a constant rate as the plunger 43 moves up and down, the fuel injection pressure during the suction pressure feeding process is
As shown by the dotted line 102 in FIG. 8, it increases and decreases at a constant rate. The fuel injection ratio (hereinafter, “fuel injection ratio” is referred to as “injection ratio”) is shown in FIG.
As shown by the dotted line 104 of FIG.

In Japanese Utility Model Publication No. 1-28298, when the engine speed increases and the pressure in the pressurizing chamber exceeds a certain value, the piston-like member provided in the plunger descends, and By increasing the volume of the pressure chamber and lowering the fuel injection pressure, the increase of NOx at the time of middle-high speed rotation of the engine is reduced. However, the plunger makes one reciprocation (1 cycle) regardless of the engine speed.
The pattern of fuel injection pressure and injection rate during
02 and 104.

[0005]

In order to reduce NOx, particulates, smoke and the like contained in the exhaust gas of the diesel engine, the solid line 101 and the solid line 1 in FIG.
As shown in 03, an ideal pattern is one in which the increase rate of the injection pressure and the injection rate in the initial injection period a is lower than the injection pressure and the increase rate of the injection rate in the intermediate injection period b to the latter period b. It is generally known to be. However, the injection rate pattern of the fuel injection pump shown in FIG. 7 and Japanese Utility Model Publication 1-28298 is different from this ideal injection rate pattern. On the other hand, the storage pressure type electronically controlled fuel injection pump has an advantage that the injection rate pattern can be freely controlled, but has a problem that the device becomes complicated and the cost becomes high.

The present invention has been made to solve the above problems, and increases the rate of increase of the fuel injection pressure and the injection rate from the middle of fuel injection, and it is easily contained in the exhaust gas with a simple structure. An object of the present invention is to provide a fuel injection pump that reduces harmful substances that are generated.

[0007]

SUMMARY OF THE INVENTION A fuel injection pump according to the present invention for solving the above-mentioned problems includes a cylinder having a slide hole for holding a plunger reciprocally and slidably, and a pump housing for containing the cylinder. A fuel gallery, which is formed by the cylinder and the pump housing, to which fuel is supplied, a cylinder portion protruding into the sliding hole of the cylinder, and a flange portion fixing the cylinder portion to the cylinder, A spacer having a fuel passage that communicates the inside and the outside of a wall forming the tubular portion, and an axial wall extending from one end of the plunger facing the flange portion, the outer wall of the tubular portion being slidable. A bottomed hole for holding, one end surface of the plunger, a part of the sliding hole of the cylinder, a part of the outer wall of the cylindrical part of the spacer, and a part of the flange part. A first pressurizing chamber, a second pressurizing chamber formed by the inner wall of the tubular portion and the bottomed hole, and a cylinder formed in the cylinder to communicate the fuel gallery with the first pressurizing chamber. And a plunger lead formed on the outer wall of the plunger and configured to communicate the first pressurizing chamber and the feed hole when the pressurization of the fuel by the rise of the plunger is completed. , The first pressurizing chamber and the second pressurizing chamber are pressurized until the plunger closes the feed hole until the fuel passage is closed, and the plunger lead closes the fuel passage after the plunger closes the fuel passage. Only the first pressure chamber is pressurized until it communicates with the feed hole.

[0008]

In the fuel injection pump of the present invention, the first pressurizing chamber and the second pressurizing chamber are pressurized until the middle of fuel injection, and thereafter only the first pressurizing chamber is pressurized to increase the fuel pressurizing volume. By decreasing, the rate of increase of the injection pressure and the injection rate is increased during the fuel injection.

[0009]

Embodiments of the present invention will be specifically described with reference to the drawings. 1 and 2 show the configuration of an embodiment of a fuel injection pump according to the present invention. As shown in FIG. 1, the fuel injection pump 1 includes a cylinder 11, a plunger 13, a spacer 14, and a delivery valve 30 in a housing 11.
Are housed.

An annular fuel chamber 11a is formed on the inner wall of the housing 11, and low-pressure fuel is supplied to the fuel chamber 11a from a fuel pump (not shown). Cylinder 12
Are fixed to the housing 11 with bolts 15. A feed hole 12a is formed on the side wall of the cylinder 12 to connect the fuel chamber 11a and a first pressure chamber 21 described later. The fuel escape passage 12b is provided in the feed hole 12
1 so as to pass through the side wall from the outer wall of the cylinder 12 which is located below the fuel tank 11a and faces the fuel chamber 11a.
And extends in an obliquely downward direction and communicates with an annular groove 12c formed in the circumferential direction of the inner wall of the cylinder 12.

The plunger 13 is supported by the inner wall of the cylinder 12 so as to be slidable in the axial direction, and has a cylindrical bottomed hole 13a which is open toward the first pressurizing chamber 21 in the axial direction.
The plunger lead 13b has a U-shaped cross section and extends downward from the first pressure chamber 21 side of the outer wall by a predetermined length, and further extends obliquely downward. A rectangular groove 13c is formed on the outer wall below the plunger lead 13b in the circumferential direction, and the escape passage 13
d connects the bottomed hole 13a and the groove 13c.

The spacer 14 includes a disk portion 14a and a cylindrical portion 1
4b and the disc portion 14a are integrally formed with each other.
It is locked to the shoulder portion 12d. Four fuel passages 14c are formed in the disc portion 14a so as to penetrate the disc portion 14a. The fuel passage 14a faces the first pressurizing chamber 21 on the fuel upstream side, and faces the fuel passage 32a of the valve seat 32 described below on the fuel downstream side. The outer diameter of the cylindrical portion 14b is slightly smaller than the inner diameter of the bottomed hole 13a of the plunger 13, and the cylindrical portion 14b is fitted in the bottomed hole 13a with a minute gap. The cylindrical portion 14b is formed with a cylindrical bottomed hole 14d that opens toward the plunger 13 in the axial direction, and a fuel passage 14e that penetrates the side wall of the cylindrical portion 14b and communicates with the bottomed hole 14d.

The first pressurizing chamber 21 has an inner wall of the cylinder 12,
The second pressurizing chamber 22 is defined by one end surface of the plunger 13 and the outer wall of the spacer 14, and the second pressurizing chamber 22 is formed by the bottomed hole 13 a of the plunger 13 and the bottomed hole 14 d of the spacer 14. In the delivery valve 30, as shown in FIG. 1, the male screw portion 31 a of the holder 31 is the female screw portion 12 of the cylinder 12.
The valve seat 32 is brought into contact with the spacer 14 by being screwed to e. The valve 33 is housed in a holder 31 and a valve seat 32, and a spacer 14 is formed by a compression coil spring 34 whose one end is fixed to the holder 31.
Biased to the side.

The holder 31 has a large-diameter fuel passage 31b formed on the upstream side of the fuel, and a small-diameter fuel passage 31c formed following the large-diameter fuel passage 31b, and penetrates the holder 31 in the axial direction. The valve 33 includes a large diameter portion 33a on the fuel downstream side and a small diameter portion 33b on the fuel upstream side. A large diameter fuel passage 33c is formed inside the large diameter portion 33a, a small diameter fuel passage 33d is formed inside the small diameter portion 33b following the large diameter fuel passage 33c, and penetrates the valve 33 in the axial direction. The small diameter portion 33b is slidably fitted into the fuel passage 32a penetrating the valve seat 32, and the urging force of the compression coil spring 34 causes the boundary portion between the large diameter portion 33a and the small diameter portion 33b to be located downstream of the fuel in the valve seat 32. It can come into contact with the end face 32b on the side. The large diameter passage 33c houses the stopper 35, the ball 36, and the piston 37. The stopper 35 is fixed on the fuel downstream side of the large-diameter fuel passage 33c, and a fuel passage 35a is formed so as to penetrate the stopper 35 in the axial direction.
The ball 36 is in contact with the recess 37a of the piston 37. The piston 37 is biased by a compression coil spring 38 having one end fixed at the boundary between the large-diameter fuel passage 33c and the small-diameter fuel passage 33d, so that the ball 36 is brought into contact with the valve seat 35b of the stopper 35.

The operation of the fuel injection pump 1 will be described below with reference to FIGS. The fuel injection pump 1 is
The plunger 13 makes one reciprocation (one stroke) in the cylinder 12 in four steps of suction, start of pressure feeding, pressure feeding, and end of pressure feeding. Inhalation process The plunger 13 is at the bottom dead center as shown in FIG. 3, and the fuel supplied from the fuel pump (not shown) is supplied to the fuel chamber 11a.
Is sucked into the first pressurizing chamber 21 through the feed hole 12a. Further, the fuel sucked into the first pressurizing chamber 21 passes through the fuel passage 14e and has bottomed holes 14d and 13a.
Is sucked into the second pressurizing chamber 22 constituted by.

As shown in FIG. 4, when the plunger 13 starts to move up due to the driving force of a cam (not shown) and the outer wall of the plunger 13 closes the feed hole 12a, the first pressurizing chambers 21 and 2 are pressed.
The fuel in 2 begins to be pressurized. When the volume of the first pressurizing chamber 21 is V ₁ and the volume of the second pressurizing chamber 22 is V ₂ , the volume of fuel to be pressurized is V ₁ + V ₂ . When the pressure of the pressurized fuel overcomes the biasing force of the compression coil spring 34 and lifts the valve 33, the fuel passage 14c, the fuel passage 32
Supply of fuel to the fuel injection valve is started through a, the large diameter fuel passage 31b, and the small diameter fuel passage 31c.

Pumping As shown in FIG. 5, when the plunger 13 is further raised and the inner wall of the plunger 13 closes the fuel passage 14e of the spacer 14, the groove 13b of the plunger 13 comes into communication with the groove 12c of the cylinder 12. The fuel in the first pressurizing chamber 21 is not sucked into the second pressurizing chamber 22 through the fuel passage 14e, and the fuel in the second pressurizing chamber 22 rises from the bottomed hole 13a as the plunger 13 rises. 13d, groove 13
b, it is returned to the fuel chamber 11a via the fuel passage 12b.
Therefore, the volume of fuel to be pressurized is only the volume V ₁ of the first pressurizing chamber 21.

When the volume V ₁ + V ₂ is formed so as to be the same as the volume of the pressurizing chamber 61 of the conventional fuel injection pump shown in FIG. 7, the plunger 13 closes the feed hole 12a and then the plunger 13 moves the fuel passage 14e. In the period a shown in FIG. 8 until closing the injection pressure, the injection pressure and the injection rate draw substantially the same loci as the dotted line 102 indicating the conventional injection pressure and the dotted line 104 indicating the conventional injection rate. And the plunger 13
When the fuel passage 14e is closed, the volume of fuel pressurized is V
Since it is only ₁ , plunger lead 13b after period a
During the period b until the communication with the feed hole 12a,
The injection pressure and the injection rate are the solid lines 101 and 103 in FIG.
A trace substantially close to the ideal pattern shown in (1) is drawn, and it sharply rises and the peak value becomes higher than those of the conventional dotted lines 102 and 104.

After the end of the pressure feeding As shown in FIG. 6, when the plunger 13 further rises and the plunger lead 13b communicates with the feed hole 12a, the plunger lead 13b and the feed hole 12a.
The fuel in the first pressurizing chamber 21 is allowed to escape to the fuel chamber 11a via, and the pressurization of the fuel ends. The injection pressure and the injection rate start to decrease, and the plunger 13 returns to the bottom dead center.

In this embodiment, the spacer 14 is the only component newly added in comparison with the conventional fuel injection pump.
By slightly modifying the conventional cylinder and plunger, it is possible to reduce harmful substances contained in the exhaust gas by a mechanical control method without changing the size of the conventional fuel injection pump.

[0021]

According to the fuel injection pump of the present invention described above, since the volume of the pressurizing chamber is reduced during the process of pumping the plunger, the rate of increase in the fuel injection pressure increases during the fuel injection. However, along with this, the rate of increase in the injection rate increases. Therefore, N contained in the exhaust gas
Generation of harmful substances such as Ox, particulates and smoke is easily reduced, and air pollution due to exhaust gas can be mitigated.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a fuel injection pump according to the present invention.

FIG. 2 is a perspective view showing a cylinder, a plunger, and a spacer of an embodiment of the fuel injection pump according to the present invention.

FIG. 3 is a sectional view showing a suction process of an embodiment of a fuel injection pump according to the present invention.

FIG. 4 is a cross-sectional view showing a step of starting pressure feeding of an embodiment of the fuel injection pump according to the present invention.

FIG. 5 is a cross-sectional view showing a pressure feeding process of an embodiment of the fuel injection pump according to the present invention.

FIG. 6 is a cross-sectional view showing a pressure feeding end step of an embodiment of the fuel injection pump according to the present invention.

FIG. 7 is a sectional view showing a fuel injection pump according to a conventional example.

FIG. 8 is a characteristic diagram showing a relationship between ideal injection pressure and injection rate and suction pressure feeding time, and a relationship between injection pressure and injection rate of a conventional fuel injection pump and suction pressure feeding time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection pump 11 Pump housing 11a Fuel chamber (fuel gallery) 12 Cylinder 12a Feed hole 12b Escape passage 12c Groove 13 Plunger 13a Bottomed hole 13b Plunger lead 13c Groove 13d Escape passage 14 Spacer 14a Disk part (flange portion) 14b (Cylinder) 14d Bottomed hole 14e Fuel passage 21 First pressurizing chamber 22 Second pressurizing chamber 30 Delivery valve

Claims (1)

[Claims] 1. A fuel which is formed by the cylinder and the pump housing, the cylinder having a slide hole for holding the plunger reciprocatingly and slidably, the pump housing housing the cylinder, and the fuel to which the fuel is supplied. A gallery, a spacer having a cylinder portion protruding into the sliding hole of the cylinder, a flange portion fixing the cylinder portion to the cylinder, and a spacer having a fuel passage communicating between the inside and outside of a wall forming the cylinder portion, A bottomed hole formed so as to extend in the axial direction from one end of the plunger facing the flange portion and slidably holding an outer wall of the tubular portion; one end surface of the plunger and the sliding of the cylinder; A first pressurizing chamber formed by a part of the hole, a part of the outer wall of the cylindrical portion of the spacer, and a part of the flange portion, and an inner wall of the cylindrical portion and the bottomed hole. A second pressurizing chamber, and the fuel gallery and the first gallery formed in the cylinder.
A feed hole communicating with the pressurizing chamber and an outer wall of the plunger are formed so as to communicate the first pressurizing chamber with the feed hole when the pressurization of the fuel by the rise of the plunger is completed. A plunger lead, which pressurizes the first pressurizing chamber and the second pressurizing chamber until the plunger closes the feed hole until the fuel passage is closed, and the plunger closes the fuel passage. Until the plunger lead communicates with the feed hole, only the first pressurizing chamber is pressurized.