JPS592776B2 - fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to injection pressure control of a distributed fuel injection pump such as a diesel engine.

In conventional diesel engines, a fuel injection pump configured as shown in FIG. 1 is known in order to variably control the fuel injection timing according to the engine speed (Japanese Patent Application Laid-Open No. 1983-1996). (See No. 85049).

Fuel is sucked from a pump main body inlet (fuel inlet) 1 by a feed pump 3 driven by a drive shaft 2.

After the supply pressure of the fuel discharged from the feed pump 3 is controlled by a pressure regulating valve 4, it is supplied to a pump chamber 5 inside the pump housing.

The fuel in the pump chamber 5 lubricates the operating parts and is simultaneously sent to the high pressure plunger pump 6.

The pump plunger 7 is fixed to an eccentric disk 8 and is driven by the drive shaft 2 via a joint 2A.

The eccentric disk 8 has the same number of face cams 9 as the number of engine cylinders, and reciprocates by a predetermined cam lift while rotating over rollers 11 disposed on a roller ring 10.

Therefore, the pump plunger 7 reciprocates while rotating, and as a result of this reciprocating movement, the fuel sucked from the suction port 12 is transferred from the distribution port 13 to the delivery valve 1.
4 to an injection nozzle (not shown).

The amount of fuel injected is determined by the spill port 1 formed in the plunger 7.
The spill port 15 is determined by the position of the spill ring 16 that covers the spill port 5.
When the pump opens, high pressure fuel is released into the inside of the pump housing 5, and the pumping is completed.

The position of the spill ring 16 is controlled via the link lever 19 by the movement of the governor mechanism 18 driven by the rotation of the drive shaft 2, and the amount of fuel injection is increased or decreased in accordance with the engine speed.

The fuel injection timing is controlled by changing the timing at which the face cam 9 rides on the row 211 and moves the plunger 7 to the right, that is, by rotating the roller ring 10.

Since fuel is injected when the face cam 9 of the eccentric disc 8 rides up on the roller 11, for example, if the low sill ring 10 is rotated in the opposite direction to the rotating direction of the disc 8, there is a timing when the face cam 9 rides on the roller 11. Since this becomes earlier, the fuel injection timing relative to the engine crank angle becomes earlier.

In order to rotate the low ring 10, the roller ring 1 is
0 is connected to a plunger 21 via a driving pin 20.

The fuel pressure of the pump chamber 5 is introduced to the end face pressure chamber 23 of the plunger 21 sliding in the cylinder 22 through the passage 24, and the low pressure chamber 25 on the opposite side of the trench is connected to the suction side of the feed pump 3. Although the state is close to negative pressure, the spring 26
The plunger 21 is pushed back by the elastic force.

Note that the figure shows a state in which the axis of the plunger 21 has been rotated by 9 (j'), which actually coincides with the tangential direction of rotation of the low sill ring 10 as shown in FIG. 6, which will be described later.

Similarly, for convenience of explanation, the axis of the feed pump 3 is also 90
Those rotated once are shown simultaneously in the same drawing.

Since the fuel pressure in the pump chamber 5 increases in proportion to the rotational speed of the feed pump 3, the plunger 21 is pushed to the left as the engine rotational speed increases, and this causes the rotation of the eccentric disc 8 and the roller in the opposite direction. Rotate the ring 10,
It acts to gradually advance the injection timing.

Therefore, the face cam 9 controls the roller 1 at the fuel injection timing.
1, and the injection amount is determined by the period from the injection amount until the spill pole 15 opens.

Therefore, depending on the pressure increase characteristic of the plunger chamber at the time when the face cam 9 rides on the roller 11, it is determined whether the amount of injection is large at the beginning or small at the beginning.

However, in the conventional device, the cam shape of the face cam 9 has to be adjusted only by adjusting the position of the spill ring (sleeve) 16 to supply from a small flow rate at idling to a high flow rate at full load. It was set in a fixed manner to meet the requirements for large flow rates.

Therefore, as shown in FIG. 2, at the time of small flow rate A, the necessary fuel was injected into the cylinders of the engine within an extremely short period of time t1.

Note that t2 in the figure indicates the end of injection at a large flow rate.

In this way, due to the fixed cam shape of the face cam 9, the injection pressure fluctuation characteristics per cycle are fixed as shown in the figure regardless of the engine load and engine speed, and the injection rate cannot be controlled. At times, the injection rate (the rate of pressure increase corresponding to the crank angle) cannot be lowered, resulting in a problem in that combustion noise and emissions cannot be lowered.

This invention was made by focusing on these conventional problems, and it is possible to variably control the injection rate to the optimal value at all times according to the engine operating condition without changing the cam shape of the face cam of the eccentric disc. The purpose is to solve the above-mentioned problems by configuring this.

The present invention will be explained below based on some examples.

FIG. 3 is a sectional view showing an embodiment of the present invention.

First, the configuration will be described. A cylinder chamber 31 that communicates with the atmosphere or the pump body 1 through a port 30 is coaxially provided on the right side of the drawing, facing a high-pressure side oil chamber (pressure chamber) 23.

A piston 32 as a piston device that receives the pressure of the pressure chamber 23 in the chamber 31, a seat plate (sliding body) 34 driven by a threaded rod 33, and a space between the flange 35 of the piston 32 and the seat plate 34. The interposed springs 36 are arranged so as to be freely slidable.

The piston 32 is slidably supported in a hole penetrating the cylinder wall, and is biased toward the high pressure chamber 23 by a spring 36 whose set load changes with displacement of the seat plate 34.

The rod 33 is an actuator that changes the set load of the spring 36 via the seat plate 34.
An electric motor 40 that is in contact with the back surface of the motor 4 and is screwed into the nozzle 37 and rotates reversibly via a pair of spur gears 38 and 39.
is driven by the motor, spirals in the axial direction, and then stops.

The electric motor 40 is a control unit) (control circuit) 4
1 controls the drive.

The control unit 41 controls engine load and engine rotation! , the cooling water temperature, the set load of the spring 36, etc. are input to determine the operating state, and a drive signal is output to the electric motor 40 so that the injection rate becomes an optimal value according to the operating state.

Thereby, the set load of the spring 36 is set to an optimal value depending on the operating condition.

The set load of the spring 36 is detected by a piezoelectric element (or pressure sensing element such as a strain gauge) 42 installed between the spring 36 and the seat plate 34, and is input to the control unit 41 as a feedback signal.

Note that since the set load of the spring 36 changes relatively depending on the distance between the piston 32 and the seat plate 34,
As shown in FIG. 4, the distance between the piston 32 and the seat plate 34 can also be detected indirectly by electrically detecting the sliding resistance of the potentiometer 43.

A conductive contact 44 of this potentiometer 43 was attached to the piston 32, which was supported so as not to rotate by a guide (not shown), and a resistor 45, which housed the contact 44 so as to be freely slidable, was also supported so as not to rotate. The resistance value, which is attached to the sheet plate 34 and changes depending on the positional relationship between the contact point 44 and the resistor 45, is input as a feedback value to the control unit 41 through the lead wire 46 and the connector pin 47.

48 is an insulator. Further, as the potentiometer 43, a magnetoresistive element, a capacitive element, or the like can also be used.

The rest of the configuration is the same as the conventional device shown in FIG. 1, so a description thereof will be omitted.

Next, the effect will be explained.

When a low-speed, low-load operating state is reached, the control unit 41, which determines this state based on detection signals of the engine load and engine speed, outputs a drive signal, causing the electric motor 40 to rotate and the seat plate 34 to retreat to the right in the figure. Spring 36
The set load of is set weakly.

At this time, the control unit 41 calculates the drive time and rotation direction of the electric motor 40 so as to achieve a pre-stored set load value, and performs feedback control using detection signals from the piezoelectric element 42 and the potentiometer 43.

When the face cam 9 rides on the roller 11 due to the rotation of the eccentric disk 8, the plunger 21 receives a reaction force in the same direction as the rotation direction of the eccentric disk 8 (to the right in the figure) via the driving pin 20.

As a result, the pressure in the pressure chamber 23 increases, this pressure is applied to the pressure receiving surface (end surface) of the piston 32, and when this receiving pressure overcomes the set load of the spring 36, the piston 32 moves to the right in the figure.

This movement causes the volume of the pressure chamber 23 to increase,
As the pressure in the pressure chamber 23 decreases and the plunger 21 moves to the right in the figure, the roller 1 is moved through the driving pin 20.
First, it moves in the direction of rotation of the eccentric disk 8, that is, in the direction of rotation of the pump plunger 7.

Due to the movement of the roller 11, the rising speed of the fuel injection pressure is absorbed and changed, and the pressure peak shifts to a later discharge timing.

When the eccentric disc 8 rotates and exceeds the maximum lift part of the face cam 9, the cam lift amount decreases, and when the fuel pressure in the pressure chamber 23 starts to decrease, the spring 36
Since the piston 32 moves to the left in the figure due to the urging force, its injection pressure (discharge pressure) rapidly decreases.

Therefore, the injection pressure characteristics in the low-speed, low-load operating state are already shown by the broken line in FIG. 5, and the injection rate, that is, the rate of pressure rise, is appropriately lower at the initial stage than that of the conventional device shown by the solid line a.

As a result, combustion noise and emissions at low speeds and low loads can be reduced, improving driving performance.

Also, during high-load operation, the seat plate 34 is moved to the left in the figure, so the set load of the spring 36 becomes stronger.
Since the pressure in the pressure chamber 23 increases and the characteristics return to those shown by the solid line a in FIG. 5, the injection rate can be sufficiently increased to obtain high output.

As described above, according to the present invention, the fuel injection rate can be finely adjusted according to the operating conditions, and the operating performance can be improved.

FIG. 6 shows another embodiment.

This example uses the actuator (rod) of the previous example.
33, an oil chamber 49 is provided at the back of the seat plate 34, and the volume of the oil chamber 49 is changed by the control hydraulic pressure introduced into this oil chamber 49 to fully adjust the position of the seat plate 34.
The set load is controlled.

The control oil pressure is controlled by the newly installed second feed pump 5.
A hydraulic pressure of 0 is generated through a hydraulic pressure adjustment device 51 consisting of a solenoid valve or the like.

The burr that did not enter the oil chamber 49 returns to the low pressure side from the return passage 52.

The hydraulic pressure adjustment device 51 increases or decreases the hydraulic pressure depending on the operating state based on a drive signal from the control unit 41. For example, at low speed and low load, the hydraulic pressure is decreased to lower the set load of the spring 36.

Therefore, the structure is simplified and the same effects as in the previous embodiment can be obtained.

In the embodiment shown in FIG. 7, instead of the hydraulic pressure adjustment device 51 of the previous embodiment, a return passage 52 downstream of an inlet 53 provided in the oil chamber 49 has an effective area that can be varied or opened/closed depending on the operating state. A solenoid valve 54 is provided.

The electromagnetic valve 54 expands and contracts its needle valve 55 in response to a drive signal from the control unit 41. For example, at low speed and low load, the needle valve 55 is shortened to increase the effective area of the return passage 52 and reduce the pressure in the oil chamber 49. let

Note that it is desirable that the pressure from the second feed pump 50 is applied in a direction in which the needle valve 55 closes the return passage 52.

It is a 56u orifice.

The embodiment shown in FIGS. 8A and 8B is based on the solenoid valve 54 of the embodiment described above.
Instead, a control valve (on-off valve) 57 driven by the electric motor 40 is installed in the return passage 52 near the downstream of the inlet 53.
It is an intervening one.

The control valve 57 has a cylindrical shape that is directly connected to the rotating shaft of the electric motor 40, and has a radial through hole 58 at its tip.

Since the through hole 58 is inserted into the return passage 52, the opening area of the through hole (orifice) 58 changes depending on the rotation angle of the control valve 57, and the flow of oil into the oil chamber 49 can be controlled. can.

The orifice 59 provided at the inlet 53 of the oil chamber 49 is intended to reduce the outflow of oil when the roller 11 and face cam 7 are engaged.

FIG. 9 shows an embodiment in which injection characteristics somewhat different from those of the embodiment shown in FIG. 3 can be obtained.

In this embodiment, a sub-piston 60 having a smaller diameter than the piston 32 of the previous embodiment is inserted concentrically and freely slidably, the piston 32 and the sub-piston 60 constitute a piston device, and the sub-piston A sub-spring 6 having a weaker spring constant than the spring 36 is provided between the spring 60 and the seat plate 34.
1 is inserted.

The secondary piston 60, which is biased toward the left side in the figure by the secondary spring 61, has a 7 flange portion 6 that receives the fuel pressure in the pressure chamber 23.
2 is formed.

The eccentric disc 8 rotates and the face cam 9
When engages with the roller 11, their interaction tends to move the plunger 21 to the right in the figure via the driving pin 20, so that the pressure in the pressure chamber 23 increases and acts on both pistons 32 and 60. However, the sub spring 61, which has a weak spring constant, bends first, and after the sub piston 61 has completely moved to the right in the figure, the main piston 32 moves to the right, and the pressure in the pressure chamber 23 changes in two stages.

Therefore, as shown by the broken line in FIG. 10, a two-stage pressure change characteristic is obtained, compared to the pressure change characteristic (solid line a) of the above embodiment.

This makes it possible to further reduce the initial injection pressure and perform appropriate fuel control.

As explained above, according to this invention, the hydraulic pressure in the end face pressure chamber of the plunger connected to the driving pin is variably controlled via the piston and the spring according to the operating condition, so that fuel injection is possible. The combustion rate can be finely adjusted depending on the operating conditions, and effects such as reducing combustion noise especially at low speeds and low loads can be obtained.

[Brief explanation of drawings]

Figure 1 is a sectional view of the conventional device, Figure 2 is its injection characteristic diagram,
FIG. 3 is a sectional view of one embodiment of the present invention, FIG. 4 is a sectional view of another embodiment, FIG. 5 is an injection characteristic diagram of the embodiment of the present invention, and FIGS. 8A is a cross-sectional view of a main part of another embodiment, FIG. 8B is a perspective view of the control valve of FIG. 8A, and FIG.
The figure is a sectional view of a main part of another embodiment, and FIG. 10 is an injection characteristic diagram of the embodiment of FIG. 9. 7... Pump plunger, 8... Eccentric disc, 9... Face cam, 11... Roller, 16... Spill ring, 20... Driving pin, 21... Plunger, 23...・Pressure chamber, 31・
...Cylinder chamber, 32...Piston, 33...Rod, 34...Seat plate, 36...Spring, 40
...Electric motor, 41...Control unit,
42... Piezoelectric element, 43... Potentiometer,
49... Oil chamber, 50... Second feed pump, 5
1... Pressure adjustment device, 52... Return passage, 54
... Solenoid valve, 57 ... Control valve, 58 ... Through hole (
orifice), 60... sub-piston, 61... sub-spring.

Claims (1)

[Scope of Claims] 1. A fuel injection pump in which a low ring for adjusting fuel injection timing is connected to a plunger via a driving pin, and the plunger is displaced in accordance with the fuel pressure in a pressure chamber. A pressure chamber that receives a reaction force acting on the pressure chamber is provided with a piston device that moves in a direction to release the increased pressure when the pressure in the pressure chamber increases, and a spring that biases the piston device in the direction of the pressure increase. A fuel injection pump characterized by being provided with a control means for changing a set load according to operating conditions. 2. A sliding body in contact with the end surface of the spring for which the control means urges the piston device toward the pressure chamber; a driving means for mechanically or hydraulically advancing and retracting the sliding body; and a driving means for bringing the driving means into an engine operating state. 2. The fuel injection pump according to claim 1, further comprising means for controlling based on a corresponding signal. 3. The piston device includes a piston that receives fuel pressure in a pressure chamber, and a sub-piston coaxially and slidably housed in the piston, and includes a sub-spring that urges the sub-piston in the pressure increasing direction. The fuel injection pump according to claim 2, characterized in that: