JPS6312836A - Injection rate control device for fuel injection pump - Google Patents

Abstract

PURPOSE:To improve startability especially during the cold, by a method wherein, in a device, containing an electrostriction type actuator in a varying volume chamber communicated to a pump chamber, a spring, through the force of which the electrostriction type actuator is energized in a contraction direction, is formed by a temperature sensing member. CONSTITUTION:After a fuel injection pump 1 pressurizes fuel sucked in a pump chamber 2 through rotating reciprocation movement of a plunger 6, the fuel is distributed and fed through a distribution passage 14 and a deliver valve 15 to each fuel injection valve 13. An injection rate control device 3 is coupled directly to the pump chamber 2, and the control device varies a fuel injection factor by expanding and contracting the volume of the varying volume chamber 26 on the left of a piston 22 through expansion and contraction of a varying volume chamber 26. In this case, a disc spring 23, through the force of which the piston 22 contained in the varying volume chamber 26 is energized rightward, is formed by a shape memory alloy, and during the cold, the disc spring 23 is functioned simply as a plastic body, and serves to slightly impede an increase in a pressure in the pump chamber 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection rate control device provided in a fuel injection pump of a diesel engine.

[Conventional technology]

As a fuel injection pump, due to the plunger's IJI,
Some pumps have a configuration in which the pump chamber is expanded to absorb fuel into the pump chamber, and the pump chamber is contracted to discharge the fuel inside the pump chamber to the outside. Now,
In order to sufficiently increase the maximum injection amount and improve the responsiveness of the injection action in such a fuel injection pump, the present applicant proposed an injection rate control device in Japanese Patent Application Laid-Open No. 61-25925. This injection rate control device includes a casing having a variable volume chamber communicating with a pump chamber, an electrostrictive actuator housed within the casing and expanding and contracting the variable volume chamber by expanding and contracting, and an electrostrictive actuator housed within the variable volume chamber. It is equipped with a disc spring that biases the electrostrictive actuator in the direction of contraction. That is, the disc spring constantly compresses the electrostrictive actuator, thereby preventing the variable volume chamber from expanding and sufficiently increasing the fuel pressure in the pump chamber when the plunger moves forward to compress the pump chamber.

[Problem that the invention seeks to solve]

In the fuel injection pump having the above injection rate control device,
Since the fuel pressure in the pump chamber tends to rise when the plunger advances, a problem arises in that the injection rate is high and the injection period is too short during a cold start, resulting in insufficient startability. Conventionally, it has been known to warm up the combustion chamber before starting using glow plugs, etc. to improve ignition performance at startup, but in cold weather in cold regions, using glow plugs alone is not sufficient. be.

[Means for solving problems]

In the injection rate control device according to the present invention, the spring provided in the variable volume chamber has a temperature sensing member, and biases the electrostrictive actuator to the contraction side when the temperature is higher than the transformation temperature corresponding to the completion of warm-up of the engine. , the electrostrictive actuator is not substantially energized when the temperature is lower than the transformation temperature.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows an injection rate control device 3 according to an embodiment of the present invention, and this injection rate control device 3 is provided directly connected to a pump chamber 2 of a distribution type fuel injection pump 1.

First, the configuration of the fuel injection pump l will be explained.

A plunger 6 slidably supported within a cylinder bore 5 of the casing 4 performs rotational reciprocating motion in synchronization with 1/2 of the engine speed. That is, the rotation of the engine is transmitted to a drive shaft (not shown) via gears or a timing belt, the plunger 6 is rotationally driven coaxially by this drive shaft, and the face cam 7 engages with the roller 8. This causes reciprocating motion. Face cam 7 is honey (
(not shown) is always biased to the left in the figure and engaged with the roller 8, and the reciprocating motion of the plunger 6 is performed by rotating around the axis and following the shape of the cam surface of the face cam 7. be exposed. The plunger 6 has one distribution port 9 and the same number of intake ports 10 and 10 as the number of engine cylinders on its outer circumference.
', and a pump chamber 2 is formed between the tip surface of the plunger 6 and the cylinder bore 5.

The casing 4 is formed with a low pressure chamber 11, an intake passage 12 communicating the low pressure chamber 11 with the cylinder bore 5, and a distribution passage 14 through which each external injection valve 13 can pass through the cylinder bore 5. The same number of distribution passages 14 as the number of engine cylinders are provided, and a delivery valve 15 is provided in each of them. The delivery valve 15 can be opened against the force of the spring 16, and has a function as a check valve and a suction valve.

However, when the plunger 6 moves to the left and the pump chamber 2 expands, one of the suction ports 10 is connected to the suction passage 12, and the fuel in the low pressure chamber 11 is sucked into the pump chamber 2, and vice versa. When the plunger 6 moves to the right and the pump chamber 2 is pressurized, the distribution boat 9 is connected to one of the distribution passages 14, and the fuel in the pump chamber 2 is delivered to the outside. Fuel delivery begins when the plunger 6 starts moving to the right, and then the plunger 6 moves to the right and the spill port 17 opens to the spill ring 1.
The process ends when the right end surface of 8 is opened into the low pressure chamber 11. Here, the spill port 17 is an opening provided in the plunger 6 for communicating between the pump chamber 2 and the low pressure chamber 11, and the spill ring 18 has a short cylindrical shape,
A plunger 6 slides through the inner hole. The fixing position of the spill ring 18 can be changed using a lever 19, and the amount of fuel discharged from the pump chamber 2 can be changed depending on the position of the spill ring 18.

The lever 19 is interlocked with an accelerator lever (not shown).

Next, the configuration of the injection rate control device 3 will be explained.

The injection rate control device 3 includes, from the right in the figure, an electrostrictive actuator 21, a piston 22, and a disc spring 23 in a casing 20.
, and is configured to house a distance piece 24.

The casing 20 is in the form of a cylinder with a bottom, i.e. bag-like, and is connected to the injection pump 1 by an external thread 29 at its open end.
The installation is fixed.

The electrostrictive actuator 21 has a thin disc shape (φ15 x t
About 50 electrostrictive elements of O.5) are laminated to form a cylindrical shape. This electrostrictive element is a ceramic material called PZT, whose main component is lead zirconate titanate, and when a voltage of about 500 V is applied in the thickness direction,
It stretches by about μm. If 50 of these elements are stacked and 500V is applied in the thickness direction of each element, a total elongation of 50 μm can be obtained. If this voltage is removed or a slight negative voltage is applied, the film will shrink by 50 μm and return to its original length.

Further, when an axial compressive load is applied to the electrostrictive actuator 21, a voltage proportional to the magnitude of the load is generated in each electrostrictive element. That is, a voltage of 500V is generated by a load of 500kg. The properties of these electrostrictive elements and electrostrictive actuators are known.

When this voltage is increased to 1.0 cm, the entire electrostrictive actuator 21 is shrunk in the axial direction. That is, when the electrostrictive actuator 21 is short-circuited while a load of 500 kg is applied to the piston 22, a contraction of 50 μm occurs. Operations such as application of voltage to the electrostrictive actuator 21 at a predetermined time, shorting, opening, etc. are controlled by a controller 100, which is an external control circuit, via a lead wire 25.

The expansion and contraction action of the electrostrictive actuator 21 is transmitted to the piston 22, and the volume of the variable volume chamber 26 defined by the piston 22, the distance piece 24, and the casing 20 is expanded or contracted. The disc spring 23 is housed in the variable volume chamber 26, is made of a shape memory alloy as will be described in detail later, and biases the electrostrictive actuator 21 in a direction of compression. The distance piece 24 is disc-shaped and has a through hole 27 at its center. The diameter of the distance piece 24 is -1 rotation larger than the diameter of the piston 22, and when the male thread 29 of the casing 20 is tightened, it is sandwiched between the casing 20 and the casing 4 to form a seal. The variable volume chamber 26 communicates with the pump chamber 2 via a through hole 27.

An O-ring 28 is disposed around the outer periphery of the piston 22 so that the pressure in the variable volume chamber 26 does not leak to the electrostrictive actuator 21 side via the piston 22.

The shape memory alloy constituting the disc spring 23 is a temperature sensing member, and has a plastic function and an elastic function at a preset transformation temperature. As shown in FIG. 2, there is a proportional relationship between the oil temperature or water temperature of the engine and the fuel temperature inside the pump, and the transformation temperature of the disc spring 23 is determined by the fuel temperature inside the fuel injection pump 1 expressed by the oil temperature or water temperature. The temperature is set to correspond to the warm-up completion temperature.

After warming up, the disc spring 23 functions as an elastic body and constantly biases the electrostrictive actuator 21 in the compression direction, so that the fuel in the pump chamber 2 is under sufficient pressure during machining. , a decrease in the maximum injection amount and a delay in the injection timing are prevented.

On the other hand, when cold, the disc spring 23 functions as a plastic body since the temperature is below the transformation temperature. Therefore, the disk spring 23 is mechanically in a free length state with almost no load, and does not substantially compress the electrostrictive actuator 21. Therefore, in this case, when the plunger 6 moves forward to contract the pump chamber 2, the fuel in the pump chamber 2 flows into the variable volume chamber 26 and compresses the electrostrictive actuator 21. pressure rise is slightly hindered. FIG. 3 shows the fuel pressure in the pump chamber 2 when a disk spring 23 made of a shape memory alloy is used (solid line A) and the fuel pressure inside the pump chamber 2 when a normal disk spring is used (broken line B). As can be understood from this figure, according to this embodiment, the fuel pressure rises and falls relatively slowly, and the maximum value of the fuel pressure is also low. Therefore, as long as the operating conditions of the engine are determined, the fuel injection amount remains the same, so as shown in FIG. (Actual % iC), according to the conventional injection pump, fuel injection is performed for a short period of time at a relatively long injection rate (dashed line D). Fuel injection is performed, which improves ignitability and achieves slow combustion, resulting in good starting performance.

Note that the same effect as in the above embodiment can be obtained even if a coil spring made of a shape memory alloy is used in place of the disc spring 23. Further, a snap-action type bimetal 30 as shown in FIG. 5 may be used in place of the disc spring 23. In this bimetal 30, the central portion 31 protrudes above the transformation temperature,
The central portion 31 becomes flat at temperatures above the transformation temperature.

FIG. 6 shows another embodiment. In the second embodiment, a thermowax 32 enclosed in a deformable cover 35 made of rubber or the like with excellent heat resistance is provided on the surface of the piston 22 on the variable volume chamber 26 side. A cylindrical wax plate 33 with a bottom is provided on the outside of the wax plate 35 . The wax plate 33 is slidably fitted onto the outer circumferential surface of the piston 22, and a disc spring 34 formed from a normal spring material is disposed between the bottom surface of the wax plate 33 and the distance piece 24. .

The thermowax 32 is a temperature sensing member, and expands as the temperature rises, but is set so that the elastic force of the disc spring 34 is not transmitted to the piston 22 until the engine is warmed up. That is, after warming up, the thermowax 32 expands sufficiently, and the disc spring 34 expands to the wax plate 33.
and compresses the piston 22 and electrostrictive actuator 21 via the thermowah 32. Therefore, this configuration also provides the same effects as those of the above embodiment.

(Effects of the Invention) As described above, according to the present invention, it is possible to perform fuel injection with a low injection rate and a long injection period when the engine is cold, and therefore it is possible to improve the startability of the engine when the engine is cold.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a fuel injection pump to which an embodiment of the present invention is applied, Fig. 2 is a graph showing the relationship between engine oil temperature or water temperature and fuel temperature in the fuel injection pump, and Fig. 3 is a graph showing the relationship between engine oil temperature or water temperature and fuel temperature in the fuel injection pump. Graph showing the temporal change in fuel pressure in the pump chamber, Figure 4 is a graph showing the temporal change in the injection rate of the fuel injection pump, Figure 5 is a cross-sectional view showing the snap-action bimetal, and Figure 6 is the main body. FIG. 7 is a sectional view of main parts showing another embodiment of the invention. 1... Fuel injection pump, 2... Pump chamber, 3...
...Injection rate control device, 20...Casing, 21
...Electrostrictive actuator, 23, 30, 34...Spring, 26...Variable volume chamber. 1. Fuel injection pump 23 Baoko 26/Variable volume chamber

Claims (1)

[Claims] 1. A fuel injection pump for an internal combustion engine, which expands a pump chamber to absorb fuel into the pump chamber through reciprocating motion of a plunger, and contracts the pump chamber to discharge fuel in the pump chamber to the outside. a casing having a variable volume chamber communicating with the chamber; an electrostrictive actuator housed within the casing to expand and contract the variable volume chamber by expanding and contracting; and an electrostrictive actuator housed within the variable volume to expand and contract the variable volume chamber; In an injection rate control device for a fuel injection pump equipped with a spring biased in a direction of contraction,
The spring has a temperature sensing member that biases the electrostrictive actuator toward the contraction side when the temperature is higher than the transformation temperature corresponding to the completion of warm-up of the engine, and substantially biases the electrostrictive actuator when the temperature is lower than the transformation temperature. An injection rate control device for a fuel injection pump, characterized in that it does not energize.