JPS62248866A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To obtain the simple structure at a low cost by installing an urging means for urging an injection plunger to the first pressure chamber side into which the fuel in the injection quantity is supplied, thus avoiding the need of a regulator. CONSTITUTION:The position of all injection plunger 12 which determines the fuel accommodation quantity in the first and the second pressure chambers 14 and 16 is determined according to the pressure applied from the both pressure chambers 14 and 16 and the necessary time. In other words, unless the fuel pressure having a certain pressure difference larger than the fuel pressure supplied from the first pressure chamber 14 is always supplied into the injection plunger 12 from the second pressure chamber 16, the fuel quantity for the injection in the second pressure chamber 16 can not be determined correctly. Since, even if an equal fuel pressure is supplied into the both pressure chambers 14 and 16 by a spring 17 for urging the injection plunger 12 to the first pressure chamber 14 side, a prescribed pressure difference is generated in the injection plunger 12, the fuel quantity in the second pressure chamber 16 can be set always correctly by only supplying the fuel for a desired time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fuel injection pump suitable for electronically controlling the fuel injection amount and fuel injection timing of an engine.

[Prior Art] Conventionally, as a fuel injection pump, for example, Japanese Patent Laid-Open No. 57-5
As shown in No. 6660, the pressure chamber that is compressed as the pump rotates is divided into two by a free piston (injection plunger), one pressure chamber is supplied with fuel according to the amount of injection, and the other pressure chamber is The part includes a configuration for supplying fuel according to the injection timing, that is, a first opening/closing means for liquid suction and a first pressurizing chamber communicating with the pressurizing mechanism, a second opening/closing means for liquid suction, and a discharge for liquid discharge. a second pressurizing chamber communicating with the passage, and disposed between the first pressurizing chamber and the second pressurizing chamber,
The pressurization am includes a free piston capable of transmitting hydraulic pressure between the pressurization chambers, and the pressurization am has a compression period in which pressure is compressed in a restrictive manner according to the rotation, and a period in which fuel is supplied to at least one of the pressurization chambers. The structure is configured to alternately generate a suction stroke that allows fuel to flow in a non-restrictive manner when the liquid is injected into the first pressurizing chamber and the second pressurizing chamber. A configuration of a fuel injection pump that controls the discharge timing and discharge area is known.

Furthermore, since the above fuel injection pump requires multiple opening/closing means to set the fuel injection timing and injection amount, a fuel injection pump with a single opening/closing means has been proposed (Japanese Patent Application No. 151796/1989). ).

[Problems to be Solved by the Invention] However, since fuel must flow into at least one side of the free piston in an accurate amount, the fuel supplied to the first pressurizing chamber and the second pressurizing chamber is The differential pressure between the two had to be precisely controlled, and each pressure had to be precisely regulated.

Therefore, two precise regulators for regulating fuel pressure are required for each pressurizing chamber, resulting in problems such as an increase in engine weight and an increase in the number of parts due to a complicated configuration.

Therefore, the present invention aims to solve the above problems and employs the following configuration.

[Means for Solving the Problems] That is, the gist of the present invention is to provide a compression chamber that receives compression as the drive shaft rotates, a pressure chamber that communicates with the compression chamber, and a slider in the pressure chamber. a first pressure chamber that is movably fitted and communicates with the compression chamber, and a second pressure chamber that does not communicate with the compression chamber;
an injection plunger that divides the pressure chamber; an injection timing adjustment device that controls the timing of a rise in fuel pressure in the first pressure chamber; and an injection amount adjustment device that controls the amount of fuel in the second pressure chamber. In the fuel injection pump, the injection plunger is further connected to the first pressure chamber (ll11).
The fuel injection pump is characterized in that it includes a biasing means for biasing the fuel injection pump to the fuel injection pump.

Here, the injection timing adjustment means includes, for example, a means for closing a pressure-releasing passage with an on-off valve, and the injection amount adjustment means includes, for example, a means for closing a passage through which fuel flows with an on-off valve. Examples include means for opening and closing. Further, as the biasing means, there may be mentioned a means using a spring or a repulsive force of the same polarity of a magnet.

[Operation] The fuel capacity of the first pressure chamber and the second pressure chamber is determined by the position of the injection plunger that separates the first pressure chamber and the second pressure chamber. The position of the injection plunger is determined by the pressure received from the first pressure chamber and the second pressure chamber and the time period at which the injection plunger is received. That is, unless a fuel pressure that is always higher than the fuel pressure from the first pressure chamber by a certain pressure difference is supplied from the second pressure chamber to the plunger, the amount of fuel for injection within the second pressure chamber cannot be accurately determined. However, by providing a biasing means for biasing the injection plunger toward the first pressure chamber, even if the same fuel pressure is supplied to both pressure chambers, a predetermined pressure difference is maintained in the injection plunger by the biasing means. Therefore, the amount of fuel in the second pressure chamber can always be accurately set simply by supplying fuel for a desired period of time.

Next, the present invention will be explained in detail. The present invention is not limited to these, but includes various embodiments without departing from the gist thereof.

[Embodiment] Figs. 1 to 4 show a fuel injection pump according to an embodiment of the present invention, in which Fig. 1 is a longitudinal sectional view of the fuel injection pump in its fuel suction stroke, and Fig. 2 is a longitudinal sectional view of the fuel injection pump in its fuel discharge stroke. 3 is a sectional view taken along line AA in FIG. 1, and FIG. 4 is a sectional view taken along line BB in FIG. 1. However, each process is different.

In FIG. 1, at least a pair of pressure-feeding plungers 3 are fitted into a radial hole 2 of a shaft (drive shaft) 1 that rotates in synchronization with the engine, and a roller shoe 4 and a roller are attached to the outer ends of the pressure-feeding plungers 3. 5 is provided, and the shaft 1
rotates with. As shown in FIG. 4, a roller ring 6 is attached to the outer periphery of the roller 5 with a housing 7, and the roller 5 is in contact with the inner surface of the roller ring 6 having a cam shape.

The shaft 1 is rotatably supported on the inner peripheral surface of a bearing 8 fitted in a housing 7 and a bushing 10 attached to a housing 9, and performs rotational movement. The shaft 1 has an injection plunger 12 slidably fitted in the central axial hole 11 of the shaft 1, and communicates with a compression chamber 13 which is compressed by the pressure-feeding plunger 3. A first pressure chamber 14 formed adjacent to the end surface of the injection plunger 12, and between the injection plunger 12 and a plug 15 screwed and fixed in an oil-tight manner to the right end of the axial hole 11 to prevent fuel leakage. A second pressure chamber 16 is provided. A spring 17 is disposed in the second pressure chamber 16 , one end of the spring 17 engages with the plug 15 , the other end engages with the injection plunger 12 , and the injection plunger 12 is connected to the first pressure chamber 14 . It gives an urging force towards.

The first pressure chamber 14 communicates with seven intake fuel passages 18 provided in the shaft 1, the number of which is the same as the number of engine cylinders. Passage 2 provided in
0 and selectively form a suction passage.

In addition, as shown in FIG. 2, the first pressure chamber 14 has the same number of control passages 21 as the number of engine cylinders provided in the shaft 1.
During the fuel discharge stroke, the bushing 10 selectively communicates with the fuel passage 22 provided in the bushing 10 to form a discharge control passage.

In FIG. 1, the second pressure chamber 16 communicates with the same number of intake fuel passages 23 as the number of engine cylinders provided in the shaft 1, and during the fuel intake stroke, the second pressure chamber 16 communicates with the intake fuel passages 23 provided in the shaft 1. The suction passage is selectively communicated with the suction passage.

In FIG. 3, the second pressure chamber 16 communicates with a passage 24 installed in the plug 15 and a discharge fuel passage 25 installed in the shaft 1.
It selectively communicates with a passage 26 installed in the housing 9 and a passage 27 installed in the housing 9 to form a discharge passage.

A valve holder 29 is attached to the housing 9 for attaching a delivery pipe (not shown) that communicates with the passage 27 and includes a suction valve 28 therein.

An injection plunger 1 is attached to the shaft 1 during the fuel discharge stroke.
A spill hole 30 is provided which communicates with the first pressure chamber 14 immediately before or when the plug 2 contacts the plug 15. Passage 32, room 33
and communicates with a passage 34 installed in the housing 7.

In FIG. 1, a solenoid valve 41 is disposed in the housing 9, and communication between the fuel passage 22 provided in the bush 10 and the fuel passage 42 provided in the housing 9 is established.
Perform a cutoff.

Fuel at the same pressure is supplied to the passage 20 and the passage 42 from a fuel pumping device (not shown).

A pulser 43 is fixed to the shaft 1, and the rotation speed of the shaft 1 is detected by a rotation speed sensor 44.

As shown in FIG. 4, the fuel injection pump of this embodiment has a suction stroke θ1 in which fuel is sucked by clockwise rotation of the shaft 1, and a discharge stroke θ2 in which fuel is compressed and discharged.

Incidentally, since FIG. 4 shows a fuel injection pump for a four-cylinder engine as an example, the inner periphery of the roller ring 6 is also structured to have four cam shapes corresponding to each cylinder at each of the four divided positions.

Next, the operation will be explained.

In FIG. 1, in the suction stroke θ1 of the pressure-feeding plunger 3, the passage 18 and the passage 19 communicate with each other, and further the passage 22 and the passage 23 communicate with each other.

The fuel is supplied to the first pressure chamber 14 from the passage 20 through the passage 19 and the passage 18 through a fuel tank, a fuel filter, a settler, and a fuel pumping device (not shown). 41 , the passage 22 and the passage 23 to the second pressure chamber 16 . That is, fuel is supplied to both the first pressure chamber 14 and the second pressure chamber 16 at the same fuel pressure.

However, the injection plunger 12 is pressed toward the first pressure chamber by a spring 17 within the second pressure chamber 16 . Therefore, although the supplied pressure remains the same, the injection plunger 12 moves to the left in the figure, and the amount of fuel filling the second pressure chamber 16 increases. This amount of movement depends on the opening time of the solenoid valve 41 and the repulsive force of the spring 17.

At this time, the pressure-feeding plunger 3 receives fuel pressure and moves along the inner surface of the roller ring 6 in the direction of the arrow in the figure.

On the other hand, in the discharge stroke θ2, as shown by the arrow in FIG. Communication between the passage 23 and the passage 23 is cut off.

Further, the passage 21 and the passage 22 communicate with each other, and as shown in FIG. 3, the passage 25 and the passage 26 communicate with each other, and further, the spill hole 30 and the passage 31 communicate with each other.

Then, due to the movement stroke of the pressure-feeding plunger 3, the pressure in the first pressure chamber 14 increases, so the injection plunger 12 moves to the right in the figure, and accordingly, the second pressure chamber 1
The pressure inside 6 also increases.

Therefore, the fuel in the second pressure chamber 16 passes through the passage 24, the passage 25, the passage 26, the passage 27, the suction valve 28, and the valve holder 29, and then passes through a delivery pipe (not shown).
It is injected from a nozzle (not shown).

At the end of the discharge, the injection plunger 12 closes the plug 1
5, the spill hole 30 communicates with the first pressure chamber 14, so the pressure in the first pressure chamber 14 rapidly decreases, and the injection ends.

As understood from the above operation description, the second pressure chamber 16
The fuel inside the injection plunger 1 from the start to the end of discharge.
Since the fuel is injected by the amount of movement stroke of By controlling the amount of fuel supplied to the engine, the injection amount can be controlled.

A method of controlling the injection amount will be explained.

In FIG. 1, during the suction stroke θ1 of the pressure-feeding brusher 3, fuel is supplied to the second pressure chamber 16 via the solenoid valve 41. That is, by controlling the opening period of the electromagnetic valve 41, the amount of fuel supplied to the second pressure chamber 16 can be controlled.

As shown in FIG. 5, the output of a reference position sensor (not shown) that detects the position of the piston or cam of the engine or the position of the cam of the fuel injection pump is used as a reference signal, and the time T2 from this reference signal is shown in the figure. When a valve opening signal is given to the solenoid valve 41 based on the calculation result, the solenoid valve 41 opens and then the rotation of the shaft 1 cuts off the communication between the passage 22 and the passage 23. During this period, fuel is supplied to the second pressure chamber 16.

If the opening timing of the solenoid valve 41 is advanced to the time t2a,
The fuel supply period to the second pressure chamber 16 becomes longer, the supply amount increases, and the fuel injection amount increases.

Conversely, if the valve opening timing is delayed and performed at time t2b, the fuel supply period will be shortened and the fuel injection amount will be reduced.

As can be seen from the above description, by controlling the opening timing of the electromagnetic valve 41, the fuel supply period to the second pressure chamber 16 can be controlled, and the fuel injection amount can be controlled.

A method of controlling fuel injection timing will be explained.

As shown in FIG. 2, when the solenoid valve 41 is open during the discharge stroke θ2 of the pressure-feeding plunger 3, the fuel in the first pressure chamber 14 is transferred to the passage 21 and the passageway 21 due to the movement stroke of the pressure-feeding plunger 3. 22, a solenoid valve 41, and a passage 42 to flow out.

Thereafter, as shown in FIG. 5, the discharge stroke θ2
When the electromagnetic valve 41 is closed at the intermediate position P, that is, after a time T1 from the reference signal, the pressure in the first pressure chamber 14 increases and the injection plunger 12 moves to the right in the figure.

As shown in FIG. 3, the fuel in the second pressure chamber 16 is forced into a nozzle (not shown) through the passage 24, passage 25, passage 26, passage 27, suction valve 28, and valve holder 29, and is injected. Ru.

If the closing timing of the electromagnetic valve 41 is advanced and the valve is closed at the position Pa, that is, at time tla, the timing at which the injection plunger 12 moves to the right in the figure is advanced, and the injection timing is advanced.

Conversely, if the valve closing timing is delayed and the valve is closed at the position pb, that is, at the time tib, the timing at which the injection plunger 12 moves to the right will be delayed, and the injection timing will be delayed.

In this manner, by controlling the closing timing of the electromagnetic valve 41 during the discharge stroke θ2 of the pressure-feeding plunger 3, the pre-stroke of the pressure-feeding plunger 3 is changed, so that the injection timing can be controlled.

Since this embodiment is configured as described above, the opening time of the solenoid valve 41 is simply adjusted in accordance with the repulsive force of the spring 17 during the fuel intake stroke θ1 by the pressing force of the spring 17 on the injection plunger 12. The desired amount of fuel to be injected can be achieved just by

In the above embodiment, for the purpose of improving fuel efficiency, the compression volume may be reduced by limiting the communication timing as described below.

That is, although the passage 21 and the passage 22 are normally in communication throughout the entire period of the discharge stroke θ2 shown in FIG. It is sufficient to keep the solenoid valve 41 in communication for a period from the clearest angle at which the solenoid valve 41 may be closed to the most retarded angle. Therefore, only during this period, the passage 21 and the passage 22 are communicated, and during the entire period or a part of the other discharge stroke θ2, the opening length of the boat of each passage 21 and 22 is adjusted.
If the communication between the passage 21 and the passage 22 is cut off, the pressurized volume communicating with the first pressure chamber 14 compressed by the pressure-feeding plunger 3 during the discharge stroke θ2 will be reduced, and the pressure will be removed from the second pressure chamber 16. The pressure of the discharged fuel will also increase. This state is shown in FIG.

It is the discharge stroke θ2 in which the cam lift of the pressure-feeding plunger 3 increases from time tll to time t15, and the period during which the solenoid valve 41 may be closed is from time tll to time t.
13, first, at the beginning of the discharge stroke θ2, the solenoid valve 41 is in the open state, so the fuel injection pressure does not increase. When the solenoid valve 41 closes at time t12, the fuel pressure begins to rise. Until time t13, the passage 21 and the passage 22 remain in communication and are compressed, so that the pressure increases relatively rapidly. Fuel injection starts immediately after this time t12. Next, at time t13, the passage 21
Communication between the passage 22 and the passage 22 is cut off. The compressed volume then decreases and the pressure begins to rise rapidly. After this, time t14
The movement of the injection plunger 12 causes the first pressure chamber 14 to
Since the spill hole 30 opens, the pressure of the fuel drops rapidly and the injection of fuel stops. In this way, the time point t15 is reached, and the pressure-feeding plunger 3 switches to the fuel suction side stroke.

The fuel pressure when the passage 21 and the passage 22 are in communication throughout the discharge stroke θ2 is shown by a dotted line in FIG. 6. In comparison, when the compression volume is decreased from time t13, ,
It can be seen that the pressure increases with an even larger gradient from time t13. For example, although it differs depending on the fuel injection pump and engine, from time tll to time t15, the pump angle is 4
If the angle is 5°, time tll to time t13 are set at around 10°.

In this way, the fuel injection pressure can be higher, so that the particle size of the fuel droplets sprayed into the cylinders of the engine is smaller, improving the combustion efficiency and resulting in better fuel economy. can.

The closing timing of the solenoid valve 41 is determined by calculating the time T1 from the reference signal using a computer (not shown), as shown in FIG. 5, and applying a valve closing signal to the solenoid valve 41 based on the calculation result. This causes the valve to close.

In the embodiments described above, the opening/closing means is constituted by a seat valve type solenoid valve, but a spool valve type solenoid valve may also be used. Further, in the above embodiments, the fuel compression mechanism is constructed using an inner cam system, but it can also be constructed using other compression systems, such as a face cam system or an outer cam system.

Furthermore, in the above-described embodiment, the passage 22 is used as a common passage for the suction stroke θ1 and the discharge stroke θ2, and the fuel amount and injection timing are adjusted with one solenoid valve, so the device is simplified. However, a solenoid valve may be provided for adjusting the fuel amount and for adjusting the injection timing, and with such a configuration, if the switching interval between opening and closing of the solenoid valve becomes extremely short,
This results in a more accurate response.

Further, the suction passage and the discharge passage communicating with the first pressure chamber 14 and the second pressure chamber 16 may be other types as long as they communicate with each other as explained in the above operation.

[Effects of the Invention] The present invention is provided with a biasing means for biasing the injection plunger toward the first pressure chamber. There is no need for a regulator to maintain the fuel pressure with the pressure chamber at a predetermined pressure and a predetermined differential pressure, making it possible to provide a fuel injection pump with a simple structure and low cost, reducing the weight of the engine and the number of parts. can.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a fuel injection pump according to an embodiment of the present invention during the fuel suction stroke, FIG. 2 is a vertical cross-sectional view during the fuel discharge (compression) stroke, and FIG. 3 is a cross-section taken along line A-A in FIG. figure,
Figure 4 is the same <B-B sectional view, Figure 5 is a timing chart showing the correspondence between the reference signal, cam lift change, and opening/closing of the solenoid valve in response to changes in cam angle, and Figure 6 is cam lift in response to changes in cam angle. Timing charts showing the correspondence between changes in the timing, opening/closing of the solenoid valve, and fuel injection pressure are shown. 1... Shaft 3... Pressure feeding plunger 12... Injection plunger 13... Compression chamber 14... First pressure chamber 16... Second pressure chamber 17... Spring 18, 19, 20. 21.22.23.24゜25.2
6.27,3L 32,34,42゛...Passage 30...Spill hole 33...Chamber 41...Solenoid valve

Claims (1)

[Scope of Claims] 1. A compression chamber that receives compression as the drive shaft rotates; a pressure chamber that communicates with the compression chamber; and a first compression chamber that is slidably fitted into the pressure chamber and communicates with the compression chamber. one pressure chamber and a second pressure chamber that does not communicate with the compression chamber,
an injection plunger that divides the pressure chamber; an injection timing adjustment device that controls the timing of a rise in fuel pressure in the first pressure chamber; and an injection amount adjustment device that controls the amount of fuel in the second pressure chamber. A fuel injection pump, further comprising urging means for urging the injection plunger toward the first pressure chamber. 2. The injection timing adjustment means includes a control passage communicating with the first pressure chamber, a fuel passage selectively communicating with the control passage, an opening/closing means for the fuel passage, and an intake passage selectively communicating with the first pressure chamber. a suction passage, the injection amount adjusting means communicating with the second pressure chamber;
The fuel injection pump according to claim 1, comprising a fuel passage selectively communicating with the suction passage, a means for opening and closing the fuel passage, and a discharge passage selectively communicating with the second pressure chamber. 3. The fuel passage that selectively communicates with the control passage that communicates with the first pressure chamber and the fuel passage that selectively communicates with the suction passage that communicates with the second pressure chamber are one common passage, and the injection timing 3. The fuel injection pump according to claim 2, wherein the adjusting means and the injection amount adjusting means share one opening/closing means. 4 The control passage communicating with the first pressure chamber and the fuel passage selectively communicating with the control passage are connected during the period from the most advanced angle to the most retarded angle of fuel injection during the period in which the compression chamber is under compression. 3. The fuel injection pump according to claim 1 or 2, wherein the fuel injection pump is in communication for a predetermined period including the period of time and is shut off for another period.