JPS6022063A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To improve the injection cut state and prevent after-dripping or after- injection by a method wherein a valve device, which finishes the injection by relieving a pressure chamber for controlling an injection amount into a low pressure side upon the termination of pressurizing stroke of a plunger, is provided in the pump. CONSTITUTION:A free piston 27 and a fixed bulkhead 28 are accommodated in a cylinder 21a, formed axially in a rotary shaft 21 having a pair of plungers cooperating reciprocally with the internal surface cam of a cam ring, and the inside of the cylinder 21a is defined into two pressure chambers 31, 32 for injection timing control and injection amount control by the free piston 27. The pressure cahmber 32 for controlling the injection amount is communicated with a circumferential groove 54, formed on the sliding surface of the free piston 27, through a path 55. Fuel in the pressure chamber 32 is relieved to the low pressure side to finish the injection instantaneously in case the circumferential groove 54 coincides with a relief path 61 for the low pressure side upon finishing the injection by the rightward movement of the free piston 27 in the fuel injection timing.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a fuel injection pump, and more particularly to a fuel injection pump suitable for a distribution type fuel injection pump for an internal combustion engine.

BACKGROUND TECHNOLOGY For example, distribution type fuel injection pumps that forcefully feed injected fuel to a fuel-injected multi-cylinder internal combustion engine have conventionally been pumps of the so-called Bosch VE type or Roque type, in which a plunger that sucks in and pumps fuel also rotates and reciprocates. A so-called CAV type is known in which a plunger disposed within a reshaft and freely movable in the radial direction is reciprocated by an inner cam ring.

These conventional injection pumps require some kind of servo mechanism to control the injection amount and injection timing, but this servo mechanism has the disadvantage of being complicated and expensive, and the electronic control circuit for this is also expensive. It was complicated and expensive. In addition, the correspondence between the mechanical position of the servo mechanism and the injection amount or injection timing as the controlled object lacks accuracy at the initial assembly stage, and it is difficult to obtain sufficient accuracy due to wear and tear of various moving parts due to use over time. Met.

Therefore, in an attempt to eliminate these inconveniences, the Japanese Patent Publication No. 5
An injection pump as seen in Japanese Patent No. 7-56660 has been proposed. This is shown in FIGS. 1 and 2.

This device incorporates a plunger 2 into a rotary shaft l that rotates in synchronization with the engine's moderate rotation, and moves this in the centrifugal direction by centrifugal force of rotation, and a cam ring 3
The pump is pressed in the cardiac direction to perform a pumping action. □ Two pressure chambers 5, 6 are formed within the rotary shaft 1 using the free piston 4 as a partition wall, and one pressure chamber 5 and the plunger chamber 7 are in communication with each other. Further, the other pressure chambers 6 communicate with discharge passages 10 arranged for each pressure chamber. Each pressure chamber 5.6 is provided with an electromagnetic on-off valve 8.9 that controls the amount of fuel intake. Fuel is introduced into each pressure chamber 5.6 in accordance with the valve period.

Therefore, its operation is such that when the plunger 2 is pushed in the center direction by the inner cam 3A of the cam ring 3 during the pumping stroke θ of the plunger 2 shown in FIG. The free piston 4 is moved to the right in the figure through the fuel. Therefore, the fuel in the other pressure chamber 6 is fed under pressure toward the discharge passage 10 and is used for injection.

Here, the fuel injection timing is determined according to the amount of fuel introduced into one pressure chamber 5, and the fuel injection amount is determined according to the amount of fuel introduced into the other pressure chamber 6. That is, the fuel pressure path of the plunger 2 is at the position closest to the center of rotation of the plunger 2, that is, at the time of maximum cam lift of the cam ring 3, but in reality, the path of the fuel pressure feed to the pressure chamber 5 is at an appropriate position of the free piston 4 at the end of the pressure stroke. A relief passage 12 is provided to open and relieve the fuel in the pressure chamber 5 to the low pressure side, and therefore, when the relief passage 12 is opened, the rightward movement of the free piston 4 is interrupted despite the pumping movement of the plunger 2. The fuel injection is then terminated.

Regarding the injection timing, the radial position of the plunger 2 is determined depending on the amount of fuel introduced into the pressure chamber 5.
In the next pumping stroke, the timing at which the cam ring 3 starts pressing the plunger 2 in the center direction changes, thereby providing an injection start timing that corresponds to the amount of fuel introduced into the pressure chamber 5.

However, according to such a conventional injection pump, since the injection path is determined by relieving the fuel in one pressure chamber 5 related to the injection timing to the relief passage 12 as described above, the other pressure chamber 6 The major drawback was that the extremely inconvenient phenomenon of internal pressure not decreasing at all was unavoidable.

In other words, if we look at the injection path process microscopically, one pressure chamber 5
When the internal pressure is released and relieved by opening the passage 12, the free piston 4 moves backward in the figure to the left due to the difference in force between the two pressure chambers 5.6 on both sides of the free piston 4, closing the relief passage 12 again. . Then, the pressure in the pressure chamber 5 increases again due to the plunger 2 in the pressure feeding stroke, causing the free piston 4 to move to the right again. Therefore, the fuel pressure in the other pressure chamber 6 increases and pushes open the delivery valve (not shown) installed in the discharge passage 10, causing the fuel to be discharged from the injection nozzle, resulting in a repeated after-injection or after-sag phenomenon as shown in FIG. It appears. This makes injection failure difficult and causes a large amount of unburned components to be contained in the exhaust gas, which causes deterioration of fuel efficiency.

<Object of the Invention> In view of the above-mentioned disadvantages of the conventional fuel injection pump, the present invention is intended to solve these problems, and to provide a fuel injection pump that eliminates after-sag or after-injection and improves injection cut-off. With the goal.

A further object of the present invention is to prevent the above-mentioned problems from occurring, such as damage to the fuel injection pump in the injection path area.

(Root of the invention) In order to achieve the above object, the present invention provides an injection timing control pressure chamber equipped with a first opening/closing valve for controlling the fuel intake amount, and a second opening/closing valve for controlling the fuel intake amount. a pressure chamber for controlling an injection amount that is equipped with a valve and connected to a discharge passage in a pressure feeding stroke; a free piston that partitions the side pressure chamber; a rotary shaft that includes the side pressure chamber and the free piston therein; and the rotary shaft. a plunger that is freely movable in the radial direction of the rotary shaft and sucks in and pumps fuel between the injection timing control pressure chamber; and a cam ring that has an inner cam that presses the plunger in the center direction. In a fuel injection pump that controls fuel injection timing and injection amount based on the amount of fuel sucked into each of the pressure chambers, the injection amount control pressure chamber is relieved to a low pressure side at the end of a pumping stroke of the plunger. A valve device for terminating the injection is provided to reduce the fuel pressure in the injection amount control pressure chamber at the end of the injection to a pressure sufficiently lower than the injection nozzle opening pressure to improve injection cutoff.

According to the second invention, in addition to the above invention, a second valve device is provided which relieves the pressure chamber for controlling the injection timing to the low pressure side after the valve opening timing of the valve device, and the injection timing in the compression stroke is improved. Prevents lightning pressure from increasing in the control pressure chamber.

<Example> Embodiments of the present invention will be described below based on the drawings.

4 and 5 show an embodiment in which the present invention is applied to a distribution type fuel injection pump, which has a rotary shaft 21 rotated by a drive shaft (not shown) that rotates in synchronization with engine rotation. A pair of plungers 22 are provided at one end of the rotary shaft 21 and slidably fit into the radial holes. A roller 23 is disposed outside the plunger 22 and held by a roller sash 24. These plungers 22, rollers and rollers 24
rotates with the rotary shaft 21 and the plunger 22
is biased in the centrifugal direction.

A cam ring 25 having an inner cam 25a is fixedly attached to the outer periphery of the roller 23 to a pump housing (not shown). In this respect, it is completely different from a conventional fuel injection pump using an inner cam ring, in which the cam ring is rotatably adjustable in the circumferential direction to control the injection timing. The rotary shaft 21 is a sleeve 2 fixed to the pump housing.
Perform rotational movement within 6.

A cylinder 21a formed in the axial direction within the rotary shaft 21 is provided with a free piston 27 that can freely slide in the axial direction and a fixed partition 28, and a spring 29 tensioned between these The piston 27 is elastically biased toward the right in the figure.

The inside of the cylinder 21a is partitioned by the free piston 27 into, for example, a first pressure chamber 31 for controlling injection timing and a second pressure chamber 32 for controlling injection amount on the other side.

Among these, the first pressure chamber 31 has a control chamber 31A communicating with the plunger chamber 30 and a spring chamber 31B in which the spring 29 is housed, and includes passages 33a and 33b provided in the lower shaft 21 and a sleeve. Both chambers 31A and 31B are communicated via a groove 33c provided on the inner circumference. The communication between the groove 33c and the passages 33a and 33b is cut off in the suction stroke region of the plunger 22 by rotation of the rotary shaft 21. In addition, the control room 31A is connected to the rotary shirt 1-21 through one of the suction boats 34 formed in the radial direction for the number of cylinders.
During the plunger suction stroke, the suction passage 3 in the sleeve 26
5 are connected. Fuel in a fuel tank (not shown) is introduced into the suction passage 35 via a pressure-regulated electromagnetic on-off valve 36 of the rear section 1.

The spring chamber 31B communicates with a low pressure chamber in the pump housing via a spill boat 37 in the rotary shaft 21 and a relief passage 38 in the sleeve 21, which are positioned to coincide with the plunger suction stroke.

Therefore, in the first pressure chamber 31 during the suction stroke, only the control chamber 31A is formed as an effective pressure chamber by blocking the communication groove 33C, and the spring chamber 31B has no restriction on volume change via the spill boat 37 and the relief passage 28.

The spring chamber 31B further communicates with a low pressure chamber in the pump housing via a spill boat 41 formed in the rotary shirt 1-21 and a relief passage 42 formed in the sleeve 26. The spill boat 41 and the relief passage 42 coincide with each other at the end of the plunger feeding stroke, and as the free piston 27 moves to the right in the figure, the spill boat 41 opens into the spring chamber 31B from the left end surface. Therefore, the free piston 27 and the spill boat 41 constitute a kind of valve device.

The second pressure chamber 32 is formed between the free piston 27 and the stop horn 44, and is formed between one of the suction boats 45 provided radially on the rotary shaft 21, the same number as the number of cylinders, and the suction boat 45 provided on the sleeve 26. When the passage 46 and the passage 46 coincide with each other, the fuel in the fuel tank is regulated to a low pressure and introduced through a second electromagnetic on-off valve 47 installed in the suction passage 46.

Further, the fuel pressurized in the second pressure chamber 32 is passed through a delivery valve through a discharge passage 51 formed in the lower cylinder shaft 21 and through pressure feeding passages 52 formed radially in the sleeve 26, the same number as the number of cylinders. , is supplied to an injection nozzle (not shown) arranged for each cylinder, and subjected to injection.

The second pressure chamber 32 further communicates with a circumferential groove 54 formed in the sliding surface of the free piston 27 via a passage 55.

When the escape passage 61 formed by the rotary shaft 21 and the sleeve 26 and the circumferential groove 54 coincide with each other as the free piston 27 moves to the right at the end of the plunger pressure stroke, the second pressure chamber 32 Relieve the internal pressure to the low pressure side and end the injection. Therefore, the free piston 27 and the relief passage 61 still constitute a valve mechanism.

Here, the communication timing between the circumferential groove 54 and the relief passage 61 is set to be before the communication timing with the control chamber 31B of the spill boat 41.

The stopper 44 has a passage 6 which communicates the passage 55 with the second pressure chamber 32 while in contact with the free piston 27.
It has 2.

Both the first and second electromagnetic on-off valves 36.47 have a valve body 64 that closes the suction passage 35.46 by the elastic force of a spring 63, and when the excitation coil 65 is energized, the valve body 64 The valve is opened by being lifted against the elastic force of a spring 63. Further, the electromagnetic on-off valves 36 and 47 are controlled to open at the optimum timing by a control device such as a microcomputer (not shown) which inputs and calculates engine operating conditions such as engine speed and engine load as well as engine cooling water temperature. Ru.

Next, the operation of the above structure will be explained with reference to FIG. 6 and FIG. FF17.

1 Suction Stroke - Figure 4 shows the suction stroke. When the rotary shaft 21 rotates in synchronization with the engine rotation, the plunger 22 rotates and centrifugal force acts, moving in the centrifugal direction and closing the plunger chamber 30. Attempting to inhale fuel (intake stroke θ in Figure 5)
1).

At this time, the electromagnetic on-off valve 36 is energized and the valve body 64 is opened.
When the valve is lifted and opened, fuel is sucked into the first pressure chamber 31 (control chamber 31A), and the plunger 22 is allowed to move in the centrifugal direction by an amount corresponding to the amount of sucked fuel. Therefore, the position of the plunger 22 in the semi-i direction is regulated while the plunger 22 is not in contact with the inner cam 25a of the cam ring 25 (actually, the roller holder 24 and the plunger 22 are not in contact). Of course, in order to obtain the maximum injection amount, during the plunge 22,
It is movable until it is restrained by the inner cam 25a, and the amount of fuel sucked into the control chamber 31A may be increased accordingly.

On the other hand, since the communication groove 33c is blocked and the spill boat 37 and the relief passage 38 are in communication with each other, the spring chamber 31B
The pressure is low. In this state, the electromagnetic on-off valve 47
When the valve is opened, fuel is supplied into the second pressure chamber 32 by a foot pump (not shown), and the free piston 27 moves from the contact position with the stopper 44 to the left in the figure against the elastic force of the spring 29. will be moved. This free piston 2
The distance moved to the left by 7 corresponds to the amount of fuel introduced into the second pressure chamber 32 . Which electromagnetic on-off valve 36.47
The opening time of both valves is controlled by a command signal from a control device (not shown) so as to introduce an amount of fuel according to the operating state of the engine.

-Pushing stroke- Next, when moving to the pumping stroke (θ2 in FIG. 5) shown in the engine and FIG.
The communication with each other, the communication between the spill boat 37 and the relief passage 38, and the communication between the circumferential groove 54 and the relief passage 61 are respectively cut off, and the communication groove 33C and the passage 33A133B coincide with each other, so that the control chamber 31A and the spring chamber 31B is connected.

Here, the plunger 22 is pressed in the center direction by the inner cam 25a of the cam ring 25, but the inner cam 25a
The cam lift of the inner cam 25a does not function effectively until the plunger 22 comes into substantial contact with the plunger 22, and therefore the plunger 22 does not enter the pumping stroke.

When the inner cam 25a and the plunger 22 substantially contact each other, the plunger 22 moves in the center direction, and the plunger chamber 30
The fuel and fuel inside the spring chamber 31B is fed under pressure to the spring chamber 31B via the control chamber 31A and the communication groove 33C. Therefore, at this stage, the control room 3
1A and the spring chamber 31B function as a first pressure chamber 3I, and press the free piston 27 to the right in the figure. Therefore, the fuel in the second pressure chamber 32 is injected into the corresponding combustion chamber from an injection nozzle via a delivery valve (not shown) through a discharge passage 51 and a pressure feeding passage 52 that selectively communicates with the discharge passage 51.

As the free piston 27 moves to the right and reaches the injection path timing shown in FIG. The fuel inside is relieved to the low pressure side (as a result, the pressure inside the injection pipe (not shown) leading to the injection nozzle decreases rapidly (see Fig. 7), and injection ends. Therefore, no after-injection of fuel or after-fluttering occurs.

At the same time or a little later than this, Figure 6 1cI
Since the spill boat 41 faces the spring chamber 31B from the left end of the free piston 27 as shown in FIG. 2, even if the plunger 22 pumps fuel from this point on, the fuel is only relieved to the low pressure side. Therefore, the first pressure chamber 31
The free piston 27 can be moved to the right until it comes into contact with the stopper 44 without the internal pressure rising too much, and breakage of the various pressure receiving parts can be prevented.

By lowering the pressure in both the first and second pressure chambers 31 and 32 to a predetermined pressure in this manner, the pressure can be made uniform to a predetermined value regardless of the engine operating state, and variations in injection pressure can be prevented.

As is clear from the above, the amount of fuel in the control chamber 31A is determined by the opening period of the first electromagnetic on-off valve 36, which in turn determines the radial position of the plunger 22, which determines the injection start timing. .

The injection path is determined by matching the circumferential groove 54 formed in the free piston 27 with the relief passage 61.

Therefore, the injection amount is determined by the effective stroke of the free piston 27 at the start of injection, that is, the left end position of the free piston 27. It will be determined by the amount of fuel introduced into the pressure chamber 32.

These facts indicate that an arbitrary injection rate can be obtained by freely controlling the opening and closing timing of the two electromagnetic on-off valves 36 and 47.

In this embodiment, the first pressure chamber 31 is divided into a control chamber 31A and a spring chamber 31B, but this is because the amount of fuel introduced into the second pressure chamber 32 for controlling the injection amount affects the injection timing. It has been devised so as not to affect the system, and does not necessarily require a separate configuration.

That is, by partition wall, spring 29 and passages 33a, 33b.
Alternatively, the communication groove 33'c may be omitted, and the first pressure chamber 3I may be replaced by only the control chamber 31A of this embodiment. With this configuration, the free piston 27 moves to the left in accordance with the amount of fuel for injection amount control introduced into the second pressure chamber 32, so that the injection timing control is controlled for the first pressure chamber 31 by this amount. Even if the amount of fuel introduced is constant, the position of the plunger 22 moves away in the centrifugal direction.

In other words, since the injection path is constant, the injection timing is advanced by the fuel amount for injection amount control, and in addition to this, the first pressure chamber 3
The amount of fuel introduced into the plunger 22 causes the position of the plunger 22 to further slide in the centrifugal direction.

In the above embodiment, the passage 55, the circumferential groove 54, and the relief passage 61 serve as a valve device that relieves the injection amount control pressure chamber 32 to the low pressure side at the end of the pressure stroke of the plunger 22 to terminate the injection. A groove may be formed on the cylinder 21a side, and instead of the passage 55, a similar structure in which a groove is cut in the axial direction of the circumferential surface of the free piston 27 can be adopted.

Further, a valve device for relieving the injection timing control pressure chamber to the low pressure side is formed by the free piston 27, the spill port 41, and the relief passage 42. For example, the first pressure chamber 3I
It is clear that it is also possible to adopt a configuration in which the pump is protected by providing a relief valve device that opens and relieves the pressure when the internal pressure abnormally increases above a predetermined value. .

<Effects of the Invention> As described above, according to the first invention of the present application, the injection path is performed by relieving the injection amount control pressure chamber to the low pressure side at the end of the pressure stroke during plunging. The pressure inside the pipe leading to the nozzle is rapidly reduced, making it possible to improve injection cutoff and prevent fuel from dripping. As a result, it is possible to reduce the content of unburned components in the exhaust gas, improve fuel efficiency, and prevent engine malfunctions.

Further, according to the second invention of the present application, in addition to the above, after the injection path is completed, the pressure chamber for controlling the injection timing is relieved to the low pressure side, so that an abnormal pressure increase in the pressure chamber after the end of injection is prevented, and the pump This can prevent damage to the various pressure-receiving parts.

[Brief explanation of the drawing]

Figure 1 is a vertical sectional view showing an example of a conventional injection pump, Figure 2 is a vertical sectional view showing an example of a conventional injection pump.
The figure is a cross-sectional view taken along the arrow ■-■ as above, FIG. 3 is a graph showing the injection rate characteristics of the conventional injection pump, FIG. 4 is a vertical cross-sectional view of the main part showing an embodiment of the present invention, and FIG. is a cross-sectional view taken along the line V-V of the same as above, and FIG. 6 is a longitudinal cross-sectional view showing the operating characteristics of the same example as above, (Al indicates the plunger pumping stroke, iB+ indicates the injection path state, and tc+ indicates the injection path state. , FIG. 7 is a graph showing the pipe internal pressure and injection rate characteristics according to this example. 21... Rotary shaft 22... Plunger 2
5...Cam ring 25a...Inner cam 27...
- Free piston 31... First pressure chamber (pressure chamber for controlling injection timing) 32... Second pressure chamber (pressure chamber for controlling injection amount) 36... First electromagnetic on-off valve 41... - Spill boat 42... Relief passage 47... Second electromagnetic on-off valve 51... Discharge passage 54... Circumferential groove 55.
...Aisle 61...Escape passage Fig. 1 Fig. 2 Fig. 3 Fig. Time Fig. 4 Down □ Force - One right jb 41 Fig. 5 5 --44 Fig. 7 Time

Claims (1)

[Scope of Claims] A pressure chamber for controlling an injection quantity that is connected to the rotary shaft, a free piston that partitions the side pressure chamber, a rotary shaft that includes the side pressure chamber and the free piston inside, and a rotary shaft that is freely movable in the radial direction of the rotary shaft. a plunger that sucks in and pressure-feeds fuel between the injection timing control pressure chamber provided therein; and a cam ring having an inner cam that presses the plunger in the center direction. In a fuel injection pump that controls fuel injection timing and injection amount based on the fuel amount, the fuel injection pump is provided with a valve device that relieves the injection amount control pressure chamber to a low pressure side at the end of the pressure stroke of the plunger to terminate injection. A fuel injection pump characterized by: (2) The valve device is formed in a passage that opens on the sliding surface of the free piston and constantly communicates with the pressure chamber for controlling the injection amount, and on an inner wall surface of the cylinder on which the free piston slides. and a passage communicating with the low pressure side, and the inner passage relieves the injection amount control pressure chamber to the low pressure side when the inner passage coincides with the end of the pressure stroke of the plunger. The fuel injection pump according to item 1. (3) A pressure chamber for injection timing control equipped with a first on-off valve that controls the amount of fuel intake, and a second on-off valve that controls the amount of fuel intake, and a pressure chamber that controls the fuel intake stroke. a pressure chamber for controlling the injection amount connected to the discharge passage at the rotary shaft; a free piston partitioning the side pressure chamber; a rotary shaft having the side pressure chamber and the free piston therein; and a rotary shaft movable in the radial direction. a plunger provided on the low reshaft for sucking and pumping fuel between the injection timing control pressure and the p-chamber; and a cam ring having an inner cam that presses the plunger in the center direction. In a fuel injection pump that controls fuel injection timing and injection amount based on the amount of fuel sucked into a pressure chamber, the injection amount control pressure chamber is relieved to a low pressure side at the end of a plunger's pressure stroke to perform injection. A fuel injection pump comprising: a first valve device for terminating the valve; and an ff12 valve device for relieving an injection timing control pressure chamber to a low pressure side after the valve opening timing of the valve device.