JPH08177670A - Fuel injection pump for diesel engine - Google Patents

Abstract

PURPOSE: To generate a low injection pressure in a low injection amount and a high injection pressure in a high injection amount similarly to a 2-stage cam, by enabling an injection pressure to rise and a cam surface pressure to reduce to be also formable relating to a multicylinder engine of such as six cylinders having a small degree of freedom for forming a cam profile, while a maximum cam speed can be suppressed. CONSTITUTION: In a characteristic of an unequal speed cam, it has the first cam part (a), increasing a cam speed from 0 by fixed ratio in accordance with rotating the unequal speed cam in a period of θ0 to θ1 cam rotary angle. The cam has the second cam part (b) of increasing a cam speed V along a secondary curve as cam acceleration α increases to obtain a maximum value Vmax in the next period of θ1 to θ2. The cam has the third cam part (c) connected to a rear end of the second cam part to gradually decrease the cam speed V in the next θ2 to θ3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed fuel injection pump which adjusts the fuel injection rate according to the operating condition of a diesel engine.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection device for supplying fuel to an automobile diesel engine, Japanese Patent Laid-Open No. 2-2986.
There is a technique disclosed in Japanese Patent No. 35. With this technology, 1
A distributed fuel injection pump of the type in which the plunger of the book is reciprocally moved while rotating to distribute and pressure-feed the fuel to the fuel injection valve is used. As a mechanism for reciprocating the plunger, a cam plate provided with a non-constant speed cam (cam face) having the cam characteristics shown in FIG. 13 is used. FIG.
6 is a graph showing a relationship between a change in cam lift amount (cam profile) with respect to a cam speed of a non-uniform cam and a cam speed with respect to a cam angle. From the figure, the cam lift amount increases as the cam speed increases, but since the cam used is a non-uniform cam with a non-uniform cam profile,
The cam speed at each cam angle also changes. That is, the cam speed changes according to the use area of the non-uniform speed cam.

The reason why this non-uniform speed cam is used is to change the injection rate pattern. The characteristic of the cam speed with respect to the rotation angle of the non-uniform speed cam increases in a region (t0 to t1) in which the upstream speed increases at a constant rate, and in a middle ratio at a constant rate at which the rate of increase is smaller than the increasing rate of the preceding stage. The area (t1 to t2) is set (or has a constant speed). Further, this characteristic is that in the middle area, the area where the speed linearly increases at a constant rate toward the maximum value (t2 to t3), and the latter area where the speed decreases from the maximum value at a predetermined rate (after t3). And each area is 1
The shape follows the next curve (straight line).

This cam speed is a factor that determines the moving speed of the plunger. The cam plate and the plunger are pressed against each other by a spring, and the unequal speed cams are provided in the same number as the number of cylinders of the engine.

[0005]

However, in a conventional multi-cylinder engine such as a six-cylinder engine, since the space on the cam plate is limited, the effective angle at which the cam profile can be formed is narrowed. Forming such a non-uniform speed cam has a difficult problem. Further, since the linear curve is used, the areas are essentially discontinuous and the cam shape is concave, so that the plunger does not follow the cam, which causes problems such as jumping. However, as a result, problems such as wear have occurred. Further, in order to increase the fuel injection pressure, a cam having a high cam speed is provided so as to provide a region (t2 to t3) where the velocity linearly increases at a constant rate toward the maximum value in the middle region. Need to profile. However, in this case, the fuel pressure in the high pressure chamber of the plunger increases, and the cam surface pressure increases due to the reaction force, resulting in a problem of reduced reliability.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a fuel injection pump capable of suppressing the maximum cam speed, increasing the injection pressure, and reducing the cam surface pressure. Further, it can be formed for a multi-cylinder engine such as a 6-cylinder having a low degree of freedom for forming a cam profile, and also has a low injection amount, a low injection pressure and a high injection amount as in the conventional two-stage cam. The object of the present invention is to provide a fuel injection pump capable of increasing the injection pressure.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention draws fuel into a high pressure chamber by reciprocating motion of a plunger in response to the rotation of a non-uniform speed cam, pressurizes the fuel, and pressurizes the fuel. The fuel that is pumped to the outside for a predetermined period, and the pumping speed of the fuel can be adjusted by changing the moving speed of the plunger according to the characteristics of the cam speed with respect to the rotation angle of the non-uniform speed cam. In the injection pump, the cam characteristics of the non-uniform velocity cam are as follows: the first cam part where the cam speed increases from 0 at a predetermined rate, and the cam speed that increases the cam acceleration following the rear end of the first cam part. Is non-1
The gist of the present invention is to provide a second cam portion that increases along the following curve to obtain the maximum value and a third cam portion that is connected to the rear end of the second cam portion and that reduces the cam speed.

The non-linear curve referred to in the present invention excludes a straight line and includes, for example, a quadratic curve. Two
The following curve means a conic curve obtained as an intersection (cut) of a plane and a right circular cone, and includes an ellipse, a circle, a hyperbola, and a parabola obtained by the intersection angle. That is, the quadratic curve is represented by the following binary quadratic equation.

Ax ² + by ² + 2cxy + dx + ey + f = 0 (however, not a = b = c = 0) Further, the non-linear curve includes a catenary curve, standard normal curve, cycloid, etc. Any curve that does The catenary curve is expressed by the following equation.

Y = acosh (x / a) (where a is a constant)

[0011]

With the above construction, if the cam speed is made to follow the non-linear curve in the second cam portion, that is, the acceleration is increased, the injection pressure at the pump end rises in the latter period, and Even if the cam speed decreases thereafter, the pressure still remains due to the inertial force of the fuel. Therefore, the pressure in the high pressure chamber of the plunger does not rise so much, for example, the pressure in the vicinity of the injection valve connected to the fuel injection pump can be increased, and thus the high fuel injection pressure can be obtained without increasing the cam surface pressure. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a fuel injection rate control device for a vehicle diesel engine will be described with reference to FIGS.
Follow the instructions below.

As shown in FIG. 2, the fuel injection rate control device is
It is composed of a fuel injection pump (hereinafter referred to as an injection pump) 1 and a fuel injection valve 21 attached to each cylinder of a diesel engine. The injection pump 1 in this embodiment has one
This is a distribution type fuel injection pump of a type in which the plunger 12 of the book is reciprocally moved while rotating to distribute and pressure-feed the fuel to each fuel injection valve 21. As shown in FIG. 2, the injection pump 1
A drive shaft 4 drivingly connected to the engine 3 is inserted through a lower portion of the housing 2. A rotor 5a of a vane-type feed pump (also shown in FIG. 2 in a state of being expanded by 90 degrees) 5 as a pump main body is integrally rotatably mounted on the drive shaft 4. The feed pump 5 sucks the fuel in the fuel tank 6 through a segmenter (water separator) 7 and a filter 8,
It discharges to the pump chamber 9 provided in the housing 2.

At the lower part of the housing 2, a cylinder 11 is mounted on the same axis as the drive shaft 4,
Plunger 12 is slidably fitted therein.
The space between the plunger 12 and the cylinder 11 is a pressure chamber 13 as a high pressure chamber. The drive shaft 4 and the plunger 12 are connected by a coupling 14. By this connection, the plunger 12 can rotate integrally with the drive shaft 4 and can relatively move with respect to the drive shaft 4 in the axial direction (left-right direction in the drawing).

A roller ring 15 centering on the drive shaft 4 is rotatably attached to the lower portion of the housing 2. On the surface of the roller ring 15 on the plunger 12 side, a plurality of rollers 16 are supported at equal angles on the same circumference centered on the drive shaft 4. On the other hand, a cam plate 17 is integrally rotatably attached to the base end portion (left end portion in the drawing) of the plunger 12. On the surface of the camu plate 17 on the drive shaft 4 side, as many non-constant speed cams 17a as the number of cylinders of the engine 3 are formed. The plunger 12 and the cam plate 17 are constantly pressed against the roller 16 by the spring 18.
Then, the rotational force of the drive shaft 4 is the coupling 1
By being transmitted to the cam plate 17 via 4,
The cam plate 17 and the plunger 12 reciprocate in the left-right direction in the drawing while rotating. Due to this reciprocal movement, the fuel in the pressure chamber 13 is pressurized and depressurized.

In order to introduce the fuel in the pump chamber 9 into the pressure chamber 13, the housing 2 and the cylinder 11 are formed with an intake passage 19 for connecting the pressure chamber 13 and the pump chamber 9 with each other. Corresponding to the suction passage 19, the plunger 12
The same number of intake grooves 20 as the number of cylinders of the engine 3 are formed on the outer periphery of the front end of the engine. The fuel in the pump chamber 9 is moved when the plunger 12 moves (returns) to the left in the drawing to decompress the pressure chamber 13, and when one of the suction grooves 20 coincides with the suction passage 19, the pressure chamber 13 Inhaled into.

The plunger 12 is provided with a fuel passage 22 and a distribution port 23 for distributing the fuel in the pressure chamber 13 to the cylinders of the engine 3 for pressure feeding. A distribution passage 24 is formed in the cylinder 11 and the housing 2 so as to correspond to the distribution port 23. A delivery valve 25 is arranged in the middle of each distribution passage 24, and a fuel injection valve 21 is connected via a fuel pipe 26.

In the injection stroke (pressure feeding stroke) following the suction stroke, the rotation of the plunger 12 closes the suction groove 20. When the plunger 12 further rotates, the non-uniform velocity cam 17a rides on the roller 16, the plunger 12 moves (forward) in the right direction in the drawing, and the pressure chamber 13 is pressurized. The pressurized fuel is distributed in the distribution port 23 through the distribution passage 24.
Distribution port 23, distribution passage 24,
It is pressure-fed to the fuel injection valve 21 through the delivery valve 25 and the fuel pipe 26, and is injected into each cylinder from here.

A spill port 27 is formed in the plunger 12 and a spill ring 28 is slidably fitted over the plunger 12 to terminate the fuel injection. The spill port 27 was blocked by the spill ring 28 as the plunger 12 moved further after the injection stroke.
However, the process ends when it comes out of the spill ring 28 and is opened into the pump chamber 9. At this time, the pressurized fuel overflows from the spill port 27, and the pressure of the fuel sharply drops. Due to this decrease, the pressure feeding of the fuel ends, and the fuel injection from the fuel injection valve 21 also stops.

The fuel injection amount is determined by the distance of the plunger 12 which moves from the start to the end of pressurization of fuel. The fuel injection amount is adjusted by changing this distance. In this adjustment, since the stroke of the reciprocating motion of the plunger 12 is constant, the position of the spill ring 28 in the axial direction is changed. In the housing 2, the operating condition of the engine 1 (rotational speed, load, etc.)
In order to adjust the position of the spill ring 28 accordingly, a centrifugal force type governor mechanism 29 is incorporated.

An overflow valve 31 having an orifice is attached to the upper portion of the housing 2, and the valve 31
The fuel tank 6 and the fuel tank 6 are connected by an overflow pipe 32. Then, excess fuel in the pump chamber 9 passes through the overflow valve 31 and the overflow pipe 32 in order and is returned to the fuel tank 6.

A timer 33 which operates by the pressure of the fuel in the pump chamber 9 is built in the lower portion of the housing 2. The timer 33 adjusts the position of the roller ring 15 with respect to the rotation direction of the drive shaft 4 so that the timing at which the non-uniform speed cam 17a engages with the roller 16, that is, the timing of the reciprocating motion of the cam plate 17 and the plunger 12 is controlled. It is for adjusting and controlling the fuel injection timing.

In addition to the basic structure of the fuel injection pump 1, in this embodiment, the characteristic of the non-uniform speed cam 17a (cam speed V with respect to the cam rotation angle θ) is set as follows. This characteristic is a factor that determines the oil feed rate of the fuel injection pump 1. As shown in FIG. 1, the cam rotation angle is θ 0 to θ.
In the period of 1, the cam speed is the first cam portion a which increases from 0 at a constant rate as the non-uniform speed cam 17a rotates. In the next period of θ1 to θ2, the cam speed V increases along a quadratic curve (a parabola in this embodiment) as a non-linear curve so that the cam acceleration α increases, and the maximum value Vmax is reached.
The second cam portion b for obtaining Also, the following θ2-θ3
Is a third cam portion c which is connected to the rear end of the second cam portion B and whose cam speed V gradually decreases. The third cam portion c has an inflection point P on the way so that it appears in the cam acceleration α.

Next, the fuel injection valve 21 for atomizing the fuel that has been sent under high pressure from the injection pump 1 and injecting it into the fuel chambers of the diesel engine will be described. As shown in FIGS. 3 and 4, the fuel injection valve 21 includes a nozzle holder 35 that is elongated in the vertical direction. A spacer 36 and a nozzle body 37 are arranged below the nozzle holder 35 in a stacked state. Spacer 36 and nozzle body 3
7 is attached to the nozzle holder 35 by a retaining nut 38 screwed onto the outer periphery of the lower portion of the nozzle holder 35.

An oil passage 39 is formed in the nozzle holder 35, the spacer 36 and the nozzle body 37. Oil passage 39
The upper end of is open to the upper end surface of the nozzle holder 35.
Further, the lower end of the oil passage 39 has an oil sump 4 below the nozzle body 37.
It is open at 0. The oil sump 40 communicates with the lower surface side of the nozzle body 37 via a plurality of injection holes 41 (see FIG. 4). A taper surface 41a is formed between the oil passage 40 and the injection hole 41, the taper surface 41a becoming narrower toward the lower side. Then, when the high-pressure fuel from the injection pump 1 is supplied to the fuel injection valve 21,
The fuel passes through the oil passage 39 and the oil sump 40 in this order and the injection hole 41.
Can be spouted from outside.

In the nozzle body 37 and the spacer 36,
A nozzle needle 42 for opening and closing the injection hole 41 is incorporated. The nozzle needle 42 includes a main body 43 and upper and lower shafts 44 and 45. The main body 43 has a rod shape and is slidably inserted into the nozzle body 37.
The lower end surface of the body 43 faces the oil sump 40, and the pressure of the fuel in the oil sump 40 acts on the lower end surface as a force to push the nozzle needle 42 upward.

A shaft portion 44 protruding upward from the main body portion 43 is slidably inserted in the spacer 36. In addition, a seat surface 45a that comes into contact with and separates from the tapered surface 41a is formed at the tip of the shaft portion 45 that projects downward from the main body portion 43.

A shaft portion 44 protruding upward from the spacer 36
A pressure pin 47 is attached to the. A first spring 49 is interposed in a compressed state between the pressure pin 47 and a guide sleeve 48 incorporated in a substantially central portion of the nozzle holder 35. The first spring 49 constantly urges the nozzle needle 42 in the valve closing direction (downward in the drawing). Due to this bias, FIG.
As shown in (a), the seat surface 45a has the taper surface 41.
When it comes into contact with a, the communication between the oil passage 39 and the injection hole 41 is cut off and the fuel injection is stopped. At this time, the main body 4
3 is spaced downward from the spacer 36 by a length Lb.

On the other hand, at the time of fuel injection, the nozzle needle 42 rises and the seat surface 45a is separated upward from the tapered surface 41a. Then, when the valve body is lifted by the length Lb from the closed state, the body portion 43 contacts the spacer 36.

A push rod 50 is attached to the guide sleeve 48.
Is movably inserted in the vertical direction. The push rod 50 is located on the same straight line as the nozzle needle 42. A second spring 51 is arranged inside the guide sleeve 48 in a compressed state, and the push rod 50 is always urged downward by the second spring 51.

When the nozzle needle 42 is closed, the pressure pin 47 is spaced downward from the push rod 50 by a length La (<Lb). Therefore, the biasing force of the second spring 51 is not applied to the pressure pin 47 and the nozzle needle 42. When the nozzle needle 42 rises by the length La, the pressure pin 47 contacts the push rod 50. When the moving amount of the nozzle needle 42 exceeds the length La, the urging force of the second spring 51 is applied to the nozzle needle 36. In this embodiment, the pressure pin 47, the guide sleeve 48,
The first spring 49, the push rod 50 and the second spring 51 constitute a valve opening pressure adjusting mechanism A.

In this embodiment, the fuel pressure required to start raising the nozzle needle 42 in the valve closed state is set to the first value.
The valve opening pressure P1 is defined as the second valve opening pressure P2, which is the pressure of the fuel required to start again raising the nozzle needle 42 that is in contact with the push rod 50 via the pressure pin 47. The first valve opening pressure P1 is, for example, 200 Kg
It is desirable to set it to about / cm ² . In addition, the second valve opening pressure P2 is set to the non-constant speed cam 1 in order to obtain a necessary fuel injection period.
It is desirable to set it according to the degree of increase in fuel pressure corresponding to a predetermined portion of the cam speed V of 7a.

In the above fuel injection valve 21, the injection pump 1
The nozzle needle 4 according to the pressure P of the fuel supplied from
The movement amount of 2 (lift amount L) is determined. In the oil sump 40, when the fuel pressure acting on the nozzle needle 42 is lower than the first valve opening pressure P1, the seat surface 45a is pressed against the tapered surface 41a. The fuel pressure is the first valve opening pressure P1
Above, the nozzle needle 42 begins to rise,
The seat surface 45a is separated from the tapered surface 41a. The rise continues until the pressure pin 47 contacts the push rod 50. After the contact, the rise of the nozzle needle 42 is stopped while the fuel pressure is lower than the second valve opening pressure P2.
Further, when the fuel pressure rises and becomes higher than the second valve opening pressure P2, the nozzle needle 42 rises again. This rise continues until the body portion 43 of the nozzle needle 42 contacts the spacer 36.

Further, the fuel injection valve 21 has the flow rate characteristic shown in FIG. This flow rate characteristic is almost the same as the general flow rate characteristic of the Hall type injection valve. The vertical axis of FIG. 5 indicates that pressurized air is used instead of fuel in the oil passage 39 of the fuel injection valve 21.
Is the flow rate Q of the pressurized air ejected from the ejection hole 41 when being supplied to the. As is apparent from FIG. 5, in the period in which the lift amount L is 0 to La, the flow rate Q increases almost proportionally as the lift amount L increases. In a period in which the lift amount L is larger than La, the flow rate Q rises in a curve and then becomes a substantially constant flow rate.

Now, the operation of the fuel injection rate control device constructed as described above will be described. Here, since the fuel passage 22 is interposed between the fuel injection pump 1 and the fuel injection valve 21, the pressure of the fuel pumped from the fuel injection pump 1 is slightly delayed, that is, the phase in the actual measurement. The oil reaches the oil sump 40 with a delay. Therefore, there is a time delay between the pressure Pp at the outlet of the fuel injection pump 1 (the portion immediately downstream of the delivery valve 25) and the pressure Pn at the oil sump 40.

When the drive shaft 4 of the fuel injection pump 1 rotates by receiving the driving force from the diesel engine,
The rotational force of the cam plate 1 is transmitted through the coupling 14.
7 is transmitted. Due to this transmission, the cam plate 17 and the plunger 12 are reciprocally driven in the left-right direction in FIG. 2 while rotating.

During the intake stroke in which the plunger 12 moves to the left in FIG. 2, one of the intake grooves 20 and the intake port 19 are aligned, and the fuel from the pump chamber 9 is taken into the intake passage 19,
It is sucked into the pressure chamber 13 through the suction groove 20. After that, the communication between the suction passage 19 and the suction groove 20 is cut off, and the distribution port 23 and any one of the distribution passages 23 are aligned.

When the plunger 12 further rotates, the non-uniform speed cam 17a rides on the roller 16 and the plunger 1
2 moves to the right in FIG. 2, and the pumping stroke is started. When the engagement position of the non-uniform velocity cam 17a with respect to the roller 16 is in the region of θ0 to θ1 at the cam rotation angle θ, the moving speed of the plunger 12 increases at a constant rate over time. With this increase, the volume of the pressure chamber 13 gradually decreases, and the fuel in the pressure chamber 13 is pressurized. The high-pressure fuel is pressure-fed to the fuel injection valve 21 via the distribution passage 24, the delivery valve 25, and the fuel pipe 26. Therefore, in this period, both the fuel pressures Pp and Pn increase with the passage of time.

At this time, the pressure Pn of the fuel in the oil sump 40
Is lower than the first valve opening pressure P1, the seat surface 45a
Is pressed against the tapered surface 41a, and the nozzle needle 42 is closed. Therefore, fuel is not injected from the fuel injection valve 21. At this time, the lift amount L and the injection rate are both “0”.

The engaging position of the non-uniform speed cam 17a with respect to the roller 10 becomes the place of the cam rotation angle θ of θ1, and when the time Δt corresponding to the phase delay elapses from that timing, the fuel pressure Pn in the oil sump 40 becomes the first. The valve opening pressure P1 is reached.
Then, in the fuel injection valve 21, the first spring 4
The nozzle needle 42 is pushed upward against the biasing force of 9, and the seat surface 45a is separated from the tapered surface 41a,
Fuel injection is started. Along with this, the lift amount L and the injection rate start to increase.

After the start of fuel injection, the cam speed V increases so that the cam acceleration α increases as the cam acceleration α becomes longer during the period until the engagement position of the non-uniform velocity cam 17a with respect to the roller 16 reaches the cam rotation angle θ2. To increase. Therefore, the plunger 1
The moving speed of No. 2 also increases at an accelerating rate, and the fuel pumping speed also increases at an accelerating rate. At this time, the pressure in the pressure chamber 13 of the plunger 12 does not rise so much, and the fuel pressure Pn in the oil sump 40 rises due to the inertial force of the fuel which is accelerated and fed.

Then, after the fuel pressure Pn in the oil sump 40 becomes higher than the first valve opening pressure P1, it further increases and rapidly becomes the second valve opening pressure P2. Therefore, the fuel is atomized by the high pressure injection.

By the way, since the fuel injection valve 21 is of a type having two valve opening pressures P1 and P2, the oil sump 40
After the internal fuel pressure Pn exceeds the first valve opening pressure P1, the nozzle needle 42 rises until the pressure pin 47 contacts the push rod 50 (until the predetermined valve opening position is reached). However, when the nozzle needle 42 rises by the length La and the pressure pin 47 comes into contact with the push rod 50, the urging force of the second spring 51 is newly applied to the nozzle needle 42 thereafter. Therefore, during the period when the fuel pressure Pn is lower than the second valve opening pressure P2,
The lift amount L of the nozzle needle 42 is kept constant (La).

When the fuel pressure Pn in the oil sump 40 further rises and reaches the second valve opening pressure P2, both springs 49, 5
The nozzle needle 42 rises again against the biasing force of 1. Then, when the lift amount L increases and exceeds La, the flow rate increases as the lift amount L increases, and then becomes a constant amount. Along with this, the injection rate increases. The ascent of the nozzle needle 42 stops when the main body 43 abuts the spacer 36. After that, when the spill port 28 is opened during the compression stroke of the plunger 12, the fuel inside the pressure chamber 13 is depressurized and the fuel injection from the fuel injection valve 21 is stopped. That is, even if the plunger 12 moves forward, the fuel pressure in the pressure chamber 13 does not rise while the spill port 28 is open, and fuel injection from the fuel injection valve 21 is not performed.

In the above description, the cam rotation angle θ is θ1 at the start timing of the fuel pumping period in the fuel injection pump 1.
However, this is based on the case where the engine speed is at medium speed rotation or high speed rotation.

Next, FIG. 7 and FIG. 7 show the results of measurement of the static oil feed rate between the embodiment of the fuel injection rate control device configured as described above and the comparative example in which the cam profile of the non-uniform speed cam is different. It shows in FIG.

The static oil feed rate is a measurement result when the fuel pressure feed period (fuel injection amount) is made different, that is, when the load is changed, at low engine speed, medium speed, and high speed. .

The first embodiment (E in FIGS. 7 and 8)
1) is provided with a non-constant speed cam 17a having the cam profile shown in FIG. 1 (also shown in FIG. 9). In the second embodiment (indicated by E2), the cam profile of the non-uniform velocity cam is shown in FIG. The non-uniform velocity cam of the second embodiment includes a first cam portion a, a second cam portion b, and a third cam portion c, and the second cam portion b is the first embodiment.
Unlike the first embodiment, only the shape along a hyperbola is different from the first embodiment, and the cam acceleration in the second cam portion b increases toward the cam speed Vmax.

FIG. 11 shows a cam profile of a non-uniform speed cam of Comparative Example 1 (indicated by S1) which is a conventional technique. This non-constant speed cam of the prior art has a front cam portion d whose cam speed increases linearly at a constant rate, and a rear cam portion which follows the front cam portion d and exceeds a cam speed Vmax and then decreases at a constant rate. And part e.

FIG. 12 shows Comparative Example 2 (indicated by S2) and shows a cam profile corresponding to the non-uniform speed cam disclosed in Japanese Patent Laid-Open No. 2-298635. This non-constant speed cam of the prior art linearly increases the cam speed linearly at a constant rate, and the rate at which the cam speed f increases after the preceding cam section f is slower than the preceding cam section f. It is provided with an ascending middle stage cam part g and a rear stage cam part h that decreases at a constant rate after exceeding the cam speed Vmax.

Further, in FIGS. 9 to 12, the same reference numerals are given to the same parts for each pressure feeding period (fuel injection amount). Pumping period (fuel injection amount) H1 (5 mm ³ / s
t) is H2 (1
5 mm ³ / st), H3 (35 mm ³ / st), and H4 (55 m
m ³ / st) indicates the cases of low load, medium load, and high load at medium speed, respectively, and the pumping period (fuel injection amount) H
No. 5 (60 mm ³ / st) shows the case of full load at high speed. Note that (mm ³ / st) means the fuel injection amount per stroke of the plunger 12.

FIG. 7A is a graph of the static oil feed rate of the example and the comparative example at a high load, that is, the pumping period is H4, and FIG. 7B is an example at a medium load, that is, the pumping period is H3. The static oil feed rate graph of the comparative example, (c) is a low load, that is, a graph of the static oil feed rate of the example and the comparative example when the pumping period is H2. FIG. 8A is a graph of the static oil feed rate of the example and the comparative example at full load, that is, the pumping period of H5, and FIG. 8B is an extremely low load, that is, the example and comparative example of the pumping period of H1. 2 is a graph of the static oil transfer rate of

7 (a), (b), (c) and FIG.
As is clear from (a) and (b), Example 1 (E1),
It can be seen that the static oil feed rate of the fuel injection pump 1 is lower than that of the comparative example 1 (S1) and the comparative example 2 (S2) in each of the example 2 (E2).

Next, in FIG. 6, the horizontal axis represents time and the vertical axis represents the injection rate (mm ³ / deg). Further, FIG. 6A shows that the engine speed is medium speed and the pressure feeding period (fuel injection amount) H
The injection rate waveforms of Example 1 (E1: indicated by a dotted line) and Comparative Example 1 (S1: indicated by a solid line) in the case of No. 4 are overlapped in a state where the injection start timings are matched. FIG. 6B shows the first embodiment when the engine speed is medium speed and the pressure feeding period is the fuel injection amount: 10 mm ³ / st.
The injection rate waveforms of E1 (indicated by a dotted line) and Comparative Example 1 (S1: indicated by a solid line) are overlapped with the injection start timings being matched.

From FIGS. 6 (a) and 6 (b), the first embodiment (E
It was confirmed that when the fuel injection amount was 10 mm ³ / st in 1), the maximum injection rate was low, but the injection period was long. In addition, the pressure feeding period (fuel injection amount:
In the case of 55 mm ³ / st) H4, the maximum injection rate is Example 1 (E
1) and Comparative Example 1 (S1) are the same, and Example 1 (E
It was confirmed that 1) had a lower initial injection rate.

FIG. 6 (c) shows Comparative Example 1 (S1: indicated by the solid line) and Comparative Example 2 (in the case where the engine speed is medium speed and the pumping period is the fuel injection amount: 10 mm ³ / st). S
(2: indicated by a dotted line), the injection rate waveforms are overlapped in a state where the injection start timings are matched. Comparative Example 2
In comparison with Comparative Example 1, the initial injection rate is high and does not satisfy the preferable injection rate. Further, Comparative Example 2 is disclosed in JP-A-2-
Although it corresponds to the technology of No. 298635, when it is attempted to embody it in a 6-cylinder engine, the cam distribution angle becomes 60 degrees on the cam plate 17. Then, in the non-uniform speed cam shown in FIG. 13, a region X where the cam speed is slow
Compared to T, the increase in cam speed in the area ZT where the cam speed is high is small. For this reason, in the case of a direct injection color diesel engine, the static oil feed rate at high speed is required to some extent in order to cope with high pressure, and therefore it is necessary to set a low cam speed range XT to a high level. As a result, the rising portion of the area ZT where the cam speed is high cannot be configured from the cam speed lower side. On the other hand, even if the first and second embodiments are embodied in a 6-cylinder engine, such a situation does not occur and can be dealt with.

In summary, although the static oil transfer rate in Example 1 is low, the actual injection rate in the high load range is the same as that of Comparative Example 1 which is a conventional example, and in the low load range. It was confirmed that the injection rate was as low as the static oil transfer rate.

As an ideal injection rate, a low load low injection rate and a high load high injection rate are required, and the injection rate waveform shows that the initial injection is low at a high load and the maximum injection rate is high. It satisfies the sharp cut.

Therefore, from the above, if the second cam portion b of the first embodiment is configured so that the acceleration increases so that the cam speed V follows a parabola, the above-mentioned shap cut is satisfied, and fuel injection is performed. It has been confirmed from FIG. 6 (a) that the injection pressure of the pump 1 increases in the latter period, and even if the cam speed V decreases thereafter, the pressure increase remains due to the inertial force of the fuel. Therefore, the plunger 12
It is possible to increase the pressure in the vicinity of the fuel injection valve 21 connected to the fuel injection pump 1 without the pressure inside the pressure chamber 13 rising too much. As a result, a high fuel injection pressure can be obtained without increasing the cam surface pressure. As a result, since the cam speed can be suppressed as compared with the conventional case, the cam surface pressure becomes lower than the conventional case, and pitching and seizure which hinder the reliability when the cam surface pressure rises are prevented, and the reliability is improved.

In the first embodiment, two valve opening pressures P1 and P2 are set.
Since it is used in combination with the fuel injection valve 21 provided with, it is possible to change the initial fuel injection rate pattern, and thereby the optimum injection rate pattern can be obtained. As a result, it is possible to reduce noise and improve exhaust gas (both low NOx and low smoke) by the optimum injection rate pattern.

The present invention is not limited to the above embodiment, but can be carried out as follows. (A) In the above embodiment, the fuel injection valve 21 is of the two-spring nozzle type, but a single hole nozzle, a multi-hole nozzle, a pintle nozzle, a throttle nozzle or the like may be used.

The term "injection rate" as used in this specification means the time ratio of the injection amount injected from the fuel injection valve. The technical idea grasped from the above-mentioned embodiment other than the claims described in the scope of claims will be described together with effects. (1) Following the first cam portion where the cam speed increases from 0 at a predetermined rate and the rear end of the first cam portion, the cam speed increases along the non-linear curve so that the cam acceleration increases, A cam plate for a fuel injection pump of a diesel engine having a second cam portion that obtains a maximum value and a third cam portion that is connected to the rear end of the second cam portion and that reduces the cam speed. By incorporating this cam plate into the fuel injection pump, it is possible to obtain a fuel injection pump that can suppress the maximum cam speed, increase the injection pressure, and reduce the cam surface pressure.

[0063]

As described in detail above, according to the present invention,
The maximum cam speed can be suppressed, the injection pressure can be increased, and the cam surface pressure can be reduced. Further, it can be formed for a multi-cylinder engine such as a 6-cylinder having a low degree of freedom for forming a cam profile, and also has a low injection amount, a low injection pressure and a high injection amount as in the conventional two-stage cam. Thus, it is possible to increase the injection pressure.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a cam rotation angle, a cam speed, a cam acceleration, and a cam lift of a non-uniform speed cam in a fuel injection pump of one embodiment.

FIG. 2 is a sectional view of a distribution type fuel injection pump.

FIG. 3 is a sectional view of a fuel injection valve.

FIG. 4 shows a lower end portion of the fuel injection valve, (a) is a partially enlarged sectional view showing a closed state of a nozzle needle, and (b) is a partially enlarged sectional view showing an opened state of a nozzle needle.

FIG. 5 is a characteristic diagram showing a relationship between a lift amount of a nozzle needle and a flow rate of pressurized air.

FIG. 6 shows injection rate waveforms of one example and a comparative example,
(A) is an injection rate waveform at medium speed and high load, (b) is an injection rate waveform at medium speed and low load, and (c) is an injection rate waveform between comparative examples.

7A and 7B are graphs showing static oil transfer rates at medium speeds of Examples and Comparative Examples, where FIG. 7A is a graph of static oil transfer rates under high load, and FIG. 7B is static oil transfer under medium load. Rate graph,
(C) is a graph of a static oil feed rate.

8A and 8B are graphs showing static oil transfer rates of Examples and Comparative Examples, where FIG. 8A is a graph of static oil transfer rate at an extremely low load during idling, and FIG. 8B is a static oil transfer rate at full load. Oil rate graph.

FIG. 9 is a characteristic diagram of a cam rotation angle and a cam speed of the fuel injection pump for showing the pressure feeding period in one embodiment,
(A) is a characteristic diagram of a pumping period at an extremely low load, (b) is a characteristic diagram of a pumping period at a medium load, and (c) is a characteristic diagram of a pumping period at a full load.

FIG. 10 is a characteristic diagram of a cam rotation angle and a cam speed of a fuel injection pump for showing a pressure feeding period in another embodiment, FIG. 10A is a characteristic diagram of a pressure feeding period at an extremely low load, and FIG. Is a characteristic diagram of the pumping period at medium load, and (c) is a characteristic diagram of the pumping period at full load.

FIG. 11 is a characteristic diagram of a cam rotation angle and a cam speed of a fuel injection pump for showing a pressure feeding period in one comparative example,
(A) is a characteristic diagram of a pumping period at an extremely low load, (b) is a characteristic diagram of a pumping period at a medium load, and (c) is a characteristic diagram of a pumping period at a full load.

FIG. 12 is a characteristic diagram of a cam rotation angle and a cam speed of a fuel injection pump for showing a pressure feeding period in another comparative example, FIG. 12A is a characteristic diagram of a pressure feeding period at an extremely low load, and FIG. Is a characteristic diagram of the pumping period at medium load, and (c) is a characteristic diagram of the pumping period at full load.

FIG. 13 is a graph showing a cam speed and a cam lift of a conventional non-uniform speed cam.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel injection pump, 11 ... Cylinder, 13 ... Pressure chamber as a high pressure chamber, 17 ... Cam plate, 17a ... Unequal speed cam, 21 ... Fuel injection valve, a ... 1st cam part, b ... 2nd cam part , C ... Third cam portion.

Claims (1)

[Claims] 1. A fuel is sucked into a high pressure chamber by a reciprocating motion of a plunger in response to the rotation of a non-uniform velocity cam to pressurize the fuel, and the pressurized fuel is pressure-fed outside for a predetermined period. Depending on the characteristics of the cam speed with respect to the cam rotation angle,
In a fuel injection pump capable of adjusting a pressure feeding speed of the fuel by changing a moving speed of the plunger, a cam characteristic of the non-uniform speed cam is that a first cam portion whose cam speed increases from 0 at a predetermined rate. After the rear end of the first cam portion, the cam speed increases along the non-linear curve so that the cam acceleration increases, and the second cam portion that obtains the maximum value and the rear end of the second cam portion A fuel injection pump for a diesel engine configured to include a third cam portion that is connected and has a reduced cam speed.