JPS623167A - Fuel injection valve for internal-combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel injection valve for an internal combustion engine.

[Conventional technology]

In order to suppress the generation of noise and vibration and reduce fuel consumption in internal combustion engines, especially diesel engines, it is necessary to appropriately control the fuel injection rate according to the operating conditions of the engine.

In order to control the fuel injection rate, each fuel injection valve is equipped with a piezoelectric element, and the expansion action of the piezoelectric element generates fuel pressure that biases the needle in the valve-closing direction and spring pressure that biases the needle in the valve-closing direction. A fuel injection valve in which the opening pressure of a needle is controlled in accordance with the operating state of an engine is known (see Japanese Patent Laid-Open No. 59-231170).

[Problem that the invention seeks to solve]

However, with this fuel injection valve, the valve opening pressure of the needle is controlled for each fuel injection valve, so if a large number of fuel injection valves are provided, complicated control is required.
Moreover, a problem arises in that the valve opening pressure of the needle varies from fuel injection valve to fuel injection valve. , [Means for Solving the Problems] In order to solve the above problems, the present invention includes a control hydraulic chamber that biases the needle in the valve closing direction, and the control hydraulic chamber is connected via a pressure regulating valve. It is connected to a control oil supply pump and controls a pressure regulating valve to control the oil pressure in the control oil pressure chamber and thereby control the valve opening pressure of the needle.

〔Example〕

Referring to FIG. 1, 1 is a fuel injection valve, 2 is a fuel injection valve main body, 3 is a spacer, 4 is a nozzle, 5 is a nozzle holder for fixing the spacer 3 and the nozzle 4 to the fuel injection valve main body 2, Reference numeral 6 indicates a fuel inlet, and 7 indicates a nozzle hole. A needle 8, a pressure pin 9, and a control rod 10 arranged in series are slidably inserted into the nozzle 4, spacer 3, and fuel injection valve body 2. A conical pressure receiving surface 11 is formed in the intermediate portion of the needle 8, and a needle pressurizing chamber 12 is formed around this pressure receiving surface 11. This needle pressurizing chamber 12 is connected to the fuel inlet 6 via a fuel passage 13, and on the other hand to the nozzle hole 7 via an annular fuel passage 14 formed around the needle 8. The pressure pin 9 that comes into contact with the upper end surface of the needle 8 has an enlarged portion 15 , and a compression spring 16 is inserted between the enlarged portion 15 and the fuel injection valve body 2 . Therefore, the needle 8 is always urged in the valve closing direction by the spring force of the compression spring 16.

A large diameter hole 17 and a small diameter hole 18 are formed in the fuel injection valve body 2 and are aligned with each other, and the upper end of the control rod 10 projects into the small diameter hole 18 . A pressure receiving piston 19 is in contact with the upper end of the control rod 10 . On the other hand, a large-diameter piston 20 and a small-diameter piston 21 that are integrally formed are slidably inserted into the large-diameter hole 17 and the small-diameter hole 18, respectively, and these large-diameter piston 20 and small-diameter piston 21 increase the hydraulic pressure. A servo piston 22 is formed for this purpose. A control oil pressure chamber 23 is formed between the small diameter piston 21 and the pressure receiving piston 19, and a control oil introduction chamber 24 is formed above the large diameter piston 20.

As shown in FIG. 1, a fuel supply pump 30 and a control oil supply pump 31 are provided for supplying fuel and control oil to the fuel injection valve 1. The fuel supply pump 30 is connected to the fuel inlet 6 of the fuel injection valve 1 via an injection timing control valve 32 and a constant volume accumulator 33. On the other hand, the control oil supply pump 31 is connected to the control oil introduction chamber 24 of the fuel injection valve 1 via a pressure regulating valve 34 on the one hand, and to the control oil pressure chamber 23 via a port 25 that opens into the control oil pressure chamber 23 on the other hand. Concatenated. The control oil supply pump 31 is composed of, for example, a vane pump, and the pressure regulating valve 34 returns a part of the pressurized control oil discharged from the control oil supply pump 31 to the suction port of the control hydraulic pump 31, thereby controlling the control oil introduction chamber 24 and The pressure of control oil supplied into the control hydraulic chamber 23 is controlled. Note that fuel is used here as control oil. The fuel supply pump 30, the injection timing control valve 32, the control oil supply pump 31, and the pressure regulating valve 34 are common to all the fuel injection valves 1, and therefore, one each is provided.

As shown in FIG. 1, a compression spring 26 is inserted between the large diameter piston 20 and the fuel injection valve body 2.

When the pressure in the control oil introduction chamber 24 is low, the servo piston 22 does not descend due to the spring force of the compression spring 26, and at this time the servo piston 22 is in the position shown in FIG. Therefore, at this time, the control oil pressure in the control oil pressure chamber 23 acts on the pressure receiving piston 19. The control hydraulic pressure acting on the pressure receiving piston 19 is applied to the needle 8 via the control rod 10 and the pressure pin 9.

Therefore, a force in the needle closing direction due to the compression spring 16 and a force in the needle closing direction due to the control oil pressure act on the needle 8. In this way, if the control oil pressure changes, the valve opening pressure of the needle 8 changes, and the fuel injection rate changes. When the pressure in the control oil introduction chamber 24 is low, that is, when the control oil pressure regulated by the pressure regulating valve 34 is low, the servo piston 22 does not descend due to the spring force of the compression spring 26, as described above.
At this time, the valve opening pressure of the needle 8 is equal to the control oil pressure in the control oil pressure chamber 23, that is, the pressure regulating valve 34.
It increases as the control oil pressure regulated by increases.

On the other hand, the control oil pressure in the control oil introduction chamber 24 becomes high and the valve boat 25 is closed, and at this time the servo piston
' and the servo piston 22 resists the compression spring 26, and due to the pressure increasing action of the lower stone 22, the control oil pressure in the control oil pressure chamber 23 becomes higher than the control oil pressure in the control oil introduction chamber 24. Next, as the control oil pressure in the control oil pressure introduction chamber 24 increases, the control oil pressure in the control oil pressure chamber 23 increases. Therefore, as shown in FIG. 3, the valve opening pressure P of the needle 8 increases rapidly when the control oil pressure P0 in the control oil introduction chamber 24 exceeds the constant pressure P.

By the way, the optimum needle opening pressure P for the engine load has the same shape as the curve shown in FIG. That is, the optimal valve opening pressure P
When the engine load is small, it gradually increases as the engine load increases, and when the engine load is large, it increases rapidly as the engine load increases. Therefore, when using the fuel injection valve 1 shown in FIG. 1, the optimum valve opening pressure P can be achieved by controlling the control oil pressure in the control oil introduction chamber 24 in proportion to the engine load.
can be ensured, and thus the needle opening pressure P can be easily controlled. Further, by using the servo piston 22, a large valve opening pressure can be applied to the needle 8 with a low control oil pressure, and there is an advantage that a small and low pressure control oil supply pump 31 is sufficient.

FIG. 2 shows a portion of the fuel supply pump 30 and the injection timing control valve 32. The fuel supply pump 30 has a housing 40 thereof.
a plunger 4 slidably and rotatably inserted therein;
1 and a pressurizing chamber 42 defined by a plunger 41. The plunger 41 is rotated by an engine via a drive mechanism (not shown) and reciprocated in the axial direction. A pressurized fuel outflow hole 43 is formed inside the plunger 41, and a fuel inflow groove 44 is formed on the outer peripheral surface of the plunger 41. The housing 40 also includes a pressurized fuel outflow port 45 that can communicate with the pressurized fuel outflow hole 43.
, and a fuel inflow boat 4 that can communicate with the fuel inflow groove 44
6 is formed, and the pressurized fuel outflow port 45 is connected to the fuel inlet 6 of the fuel injection valve l via the accumulator 33. When the plunger 41 rotates and descends, the fuel inflow boat 46 opens into the fuel inflow groove 44, and the fuel flows into the pressurized chamber 4.
Supplied within 2 days. Next, when the plunger 41 rotates and rises, and the fuel inflow boat 46 is closed by the plunger 41, the pressurized chamber 4 is closed as the plunger 41 moves upward.
When the pressurized fuel outflow hole 43 communicates with the pressurized fuel outflow port 45ζ, the pressurized fuel in the pressurized chamber 42 flows through the pressurized fuel outflow hole 43 and the pressurized fuel outflow port 45.
, Akiemulator 33, fuel inlet 6 and fuel passage 1
3 into the needle pressurizing chamber 12. This pressurized fuel acts on the pressure receiving surface 11 of the needle 8, causing the needle 8 to
A force in the needle valve opening direction is applied to the needle, and when this force in the needle valve opening direction exceeds the needle valve opening pressure, fuel is injected from the nozzle hole 7. Note that the needle opening pressure at this time is controlled by the pressure regulating valve 34 as described above.

On the other hand, as shown in FIG. 2, the injection timing control valve 32 has a small diameter hole 50 and a large diameter hole 51 arranged in alignment therein,
An overflow control valve 52 is slidably inserted into the small diameter hole 50 . The overflow control valve 52 includes a large-diameter portion 53 that is slidable within the small-diameter hole 50 and a valve body 54 that can open and close the connecting portion between the small-diameter hole 50 and the large-diameter hole 51 . Large diameter portion 53 and valve body 54
An overflow chamber 55 is formed between the two, and this overflow chamber 55 is connected to the pressurizing chamber 42 via an overflow path 56. On the other hand, a fuel discharge chamber 57 is formed in the large diameter hole 51, and this fuel discharge chamber 57 is connected to the fuel inflow hole 46 via a fuel return passage 58. A spring chamber 59 is formed in the small diameter hole 50 on the opposite side of the overflow chamber 55 with respect to the large diameter portion 53 of the overflow control valve 52 , and a compression spring 60 for pressing the overflow control valve 52 is formed in the spring chamber 59 . is inserted. The pressurized fuel leaking into the spring chamber 59 is discharged into the fuel discharge chamber 57 through a fuel discharge passage 61 formed in the overflow control valve 52 .

On the other hand, a spacer 62 is fitted into the injection timing control valve 32, and this spacer 62 is driven by a drive device 63 fixed to one end of the injection timing control valve 32 during injection.

It is fixedly supported within the period control valve 32. Spacer 62
A control rod 64 is slidably inserted into the control rod 64, and a control rod 64 is formed in the overflow control valve 52 and communicates the blocked fuel discharge passage 61 with the fuel discharge chamber 57. 1' fuel discharge passage 65
is formed. One end of the control rod 64 is connected to the overflow control valve 52.
The other end of the control rod 64 protrudes beyond the spacer 62. 'The drive device 63 has a hydraulic piston 67 slidably arranged in its housing 66, and a piezoelectric element 68 is inserted between the hydraulic piston 67 and the housing 66. This piezoelectric element 68 has a laminated structure in which a large number of thin plate-like piezoelectric elements are laminated, and when a voltage is applied to this piezoelectric element 68, the piezoelectric element 68 causes longitudinal strain due to an electrostrictive effect, that is, Extends in the longitudinal direction. Although the amount of elongation is a small amount, for example, about 50 μm, the response is extremely good, and the response time from application of voltage to elongation is 80 μs.
It is about ec. When the voltage application is stopped, the piezoelectric element 68 immediately contracts.As shown in FIG.
is pressed toward the piezoelectric element 68. A pressurizing chamber 70 is formed between the hydraulic piston 67 and the spacer 62, and the control rod 64 projects into this pressurizing chamber 70. A fuel passage 71 is formed within the hydraulic piston 67, and this fuel passage 71 is connected to the pressurizing chamber 70 on the one hand via a check valve 72 that allows flow only toward the pressurizing chamber 70, and on the other hand, the fuel passage 71 is connected to the pressurizing chamber 70 through a check valve 72 that allows flow only toward the pressurizing chamber 70. 66 and a fuel passage 73 formed within the spacer 62 .

When the application of voltage to the piezoelectric element 68 is stopped, the piezoelectric element 68 contracts, and the hydraulic piston 67 moves to the left by the spring force of the disc spring 69. At this time, the overflow control valve 52 is operated by the control rod 64 due to the spring force of the compression spring 60.
At the same time, it moves to the left, and the valve body 54 opens to communicate the overflow chamber 55 with the fuel discharge chamber 57. Therefore, even if the plunger 41 of the fuel supply pump 30 rises at this time, the pressure chamber 42
Since the fuel in the pressurizing chamber 42 is discharged into the fuel discharge chamber 57 via the overflow passage 56 and the overflow chamber 55, the fuel in the pressurizing chamber 42 is not pressurized, and thus the plunger 41 Even if the formed pressurized fuel outflow hole 43 communicates with the pressurized fuel outflow boat 45, fuel injection from the fuel injection valve 1 is not performed.

Next, when a voltage is applied to the piezoelectric element 68, the piezoelectric element 68 expands, and as a result, the hydraulic piston 67 moves to the right, so that the fuel in the pressurizing chamber 7o is pressurized.

When the fuel pressure in the pressurizing chamber 70 becomes high, the control rod 64
moves to the right, which causes the overflow control valve 52 to move to the right against the compression spring 60, and the valve body 54 closes the overflow chamber 55 as shown in FIG. Therefore, when the plunger 41 of the fuel supply pump 30 rises at this time, the fuel in the pressurizing chamber 42 is pressurized, and the needle pressurizing chamber 12 of the fuel injection valve 1 is pressurized.
When the fuel pressure inside increases, fuel injection occurs. On the other hand, when the application of voltage to the piezoelectric element 68 is stopped, the piezoelectric element 68 contracts, the valve element 54 of the overflow control valve 52 opens as described above, and the injection stops. At this time, the fuel in the fuel discharge chamber 57 flows through the fuel passages 73, 72 and the check valve 72.
The pressurizing chamber 70 is replenished through the pressurizing chamber 70.

As mentioned above, the response of the piezoelectric element 68 is fast;
Therefore, the fuel injection timing and fuel injection completion timing can be accurately controlled. Further, when the present invention is applied to, for example, a four-cylinder diesel engine, four pressurized fuel outflow ports 45 shown in FIG. 2 are formed on the housing 40 at equal angular intervals, and each pressurized fuel outflow port 45 is It is connected to each fuel injection valve 1.

Further, in this case, the plunger 41 is reciprocated four times during one rotation. Therefore, regardless of the number of fuel injection valves 1, the fuel supply pump 30 and injection timing control valve 32 each have -
It is enough to set it biased.

As shown in FIG. 1, the injection timing control valve 32 and the pressure regulating valve 34 are connected to an electronic control unit 80 and are controlled by an output signal of the electronic control unit 80. The electronic control unit 80 consists of a digital computer, which includes a ROM (read-on memory) S2, a RAM (random access memory) 83, a CPU (microprocessor) 84, an input port 85 and an output, which are interconnected by a bidirectional bus 81. A boat 86 is provided. A rotation speed sensor 87 is connected to the input port 85, and a load sensor 88 and a water temperature sensor 89 are further connected to the input port 85 via corresponding AD converters 90 and 91, respectively. On the other hand, the output boat 86 is connected to the piezoelectric element 68 of the injection timing control valve 32 and the solenoid of the pressure regulating valve 34 via corresponding drive circuits 92 and 93. The rotational speed sensor 87 generates a number of output pulses proportional to the engine rotational speed, and the engine rotational speed is calculated from these output pulses. The load sensor 88 generates an output voltage proportional to the amount of depression of the accelerator pedal, and the load is calculated from this output voltage. Water temperature sensor 89 generates an output voltage proportional to the engine cooling water temperature. The electronic control unit 80 controls the injection timing control valve 32 and the pressure regulating valve 34 to achieve the optimum injection timing and optimum needle opening pressure based on the engine speed, load, and water temperature.

As described above, by using the piezoelectric element 68 to control the injection timing control valve 32, pilot injection becomes possible. The pilot injection control will be explained below.

Referring to FIG. 1, a needle lift detector 94 is disposed within the spacer 3 of the fuel injection valve 1.

This needle lift detector 94 is located at the enlarged portion 1 of the pressure pin 9.
5 and the needle lift detector 94, that is, an output voltage proportional to the lift of the needle 8 is generated. A needle lift detector 94 is connected to one input terminal of a comparator 96 via an AD converter 95. A reference voltage is applied to the other input terminal of the comparator 96, and the output terminal of the comparator 96 is connected to the input port 85.
connected to. When the output voltage of the needle lift detector 94 becomes larger than a predetermined voltage, that is, when the lift amount of the needle 8 becomes larger than the predetermined lift amount, the output voltage of the comparator 96 becomes a high level. Become.

Next, fuel injection control when performing pilot injection will be explained with reference to FIGS. 5 and 6.
;Te.

Ru. Referring to FIG. 5, first, in step 100, the output signal of the rotation speed sensor representing the engine rotation speed N,
Output signal of load sensor 88 representing load and water temperature T
The output signal of the water temperature sensor 89 is taken in. Next, in step 101, it is determined whether the operating state is such that pilot injection is required, and if pilot injection is required, the process proceeds to step 102.

In step 102, the engine speed N, load and water temperature T are
The optimum pilot injection start timing τa is calculated from τa, and then in step 103 a biloft flag is set. Next, in step 104, the main injection start timing τC and the main injection completion timing τ are determined from the engine speed N, load, and water temperature T.
d is calculated, and in step 105 τa, τC9τ
d is output to the output port 86.

When the biloft injection starts τa, a voltage E is applied to the piezoelectric element 68 as shown in FIG. 4(b), and pressurized fuel is supplied to the fuel injection valve l. As a result, Figure 4 (
As shown in a), the needle 8 rises, and the output voltage V of the needle lift detector 94 rises. When the needle 8 rises, pyro-/) injection is started. When the output voltage V of the needle lift detector 94 exceeds a predetermined voltage v0, the output voltage of the comparator 96 becomes a high level, and when the output voltage of the comparator 96 becomes a high level, the sixth
The interrupt routine shown in the figure is executed. In FIG. 6, first, in step 110, it is determined whether the pilot flag is set.

When the pilot flag is set, the process proceeds to step 111, where the application of voltage to the piezoelectric element 68 is stopped, and the pilot injection is stopped.

Next, in step 112, the pilot flag is reset. Next, when the main injection start time τC comes, the timing shown in Fig. 4 (b
), a voltage is applied to the piezoelectric element 68,
Main injection takes place. At this time, since the pilot flag has been reset, the main injection continues until the main injection completion time τd even if the output voltage V of the needle lift detector 94 exceeds vo.

〔Effect of the invention〕

Since the needle opening pressure can be freely controlled, the optimum injection rate can be obtained depending on the engine operating condition.

Further, even when a plurality of fuel injection valves are provided, the opening pressure of each fuel injection valve can be controlled by one pressure regulating valve, so the injection control device can be simplified.

[Brief explanation of the drawing]

Fig. 1 is an overall view of the fuel injection bag device, Fig. 2 is a side sectional view of a part of the fuel supply pump and the injection timing control valve, Fig. 3 is a diagram showing the needle opening pressure, and Fig. 4 is a biloft. The diagrams illustrating injection control, FIGS. 5 and 6, are flowcharts for executing pilot injection control. 1...Fuel injection valve, 8...Needle, 10...
・Control rod, 22... Servo piston, 23.
... Control oil pressure chamber, 31 ... Control oil supply pump, 34
...Pressure regulating valve.

Claims (1)

[Claims] Equipped with a control hydraulic chamber that biases the needle in the valve closing direction,
The internal combustion engine is configured such that the control hydraulic chamber is connected to a control oil supply pump via a pressure regulating valve, and by controlling the pressure regulating valve, the hydraulic pressure in the control hydraulic chamber is controlled and the valve opening pressure of the needle is controlled. fuel injection valve.