JP2001073906A - High pressure piping for fuel injection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel consumption and exhaust performance and reduce cost thereby obtain high practicability, by obtaining required fuel pressure from an engine starting time and carrying out sufficient atomization of fuel injection from a fuel injection valve. SOLUTION: A fuel injection device of engine is provided with common rail type fuel piping 6 which stores fuel supplied from a high pressure pump and introduces the fuel to a fuel injection valve of each of cylinders. In the fuel injection device, a movable member 11 which can varies volume inside the fuel piping 6 is provided, the movable member 11 or an actuator of the movable member 11 is constituted of a shape member alloy 13, and a control circuit 16 is provided with operates the movable member 11 by energizing to the shape memory alloy 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-pressure pipe for fuel injection of an engine.

[0002]

2. Description of the Related Art In a fuel injection device of an engine requiring a high injection pressure, such as a direct injection engine, a common rail type fuel pipe for accumulating fuel sent from a high pressure pump and leading the fuel to a fuel injection valve of each cylinder is provided. However, in this case, when starting the engine, it is difficult to obtain a sufficient fuel pressure due to a decrease in the pressure at the time of stoppage and a delay in the rise of the discharge pressure of the high-pressure pump.

[0003] Therefore, there is a type in which a mechanical piston is arranged in a fuel pipe, and the piston is pushed into the fuel pipe by a coil spring to increase the pressure in the fuel pipe. As a result, the required fuel pressure is obtained at the time of starting the engine, the fuel injected from the fuel injection valve is sufficiently atomized, and the exhaust performance at the time of starting is improved (JP-A-10-274130, etc.). reference).

[0004]

However, such a conventional example requires a stopper for regulating the operating range of the coil spring at normal times, an electromagnetic solenoid for operating the stopper, and the like. In addition to being complicated, it requires a large space, is expensive, and is not practical.

An object of the present invention is to solve such a problem by using a shape memory alloy.

[0006]

According to a first aspect of the present invention, there is provided a fuel injection device for an engine having a common rail type fuel pipe for accumulating fuel sent from a high pressure pump and leading the fuel to fuel injection valves of respective cylinders. A movable member for changing the volume in the pipe is provided, and the movable member or the actuator of the movable member is made of a shape memory alloy, and a control circuit for operating the movable member by energizing the shape memory alloy is provided.

According to a second aspect of the present invention, in a fuel injection device for an engine having a common rail type fuel pipe for accumulating fuel sent from a high pressure pump and leading the fuel to fuel injection valves of each cylinder, the volume in the fuel pipe is variable. A control for winding a linear shape memory alloy on the outer periphery of the piston so as to tighten the piston in the direction of decreasing the volume in the fuel pipe around the outer periphery of the piston, and controlling the energization of the linear shape memory alloy Circuit.

In a third aspect based on the second aspect, a strain gauge is attached to the linear shape memory alloy so that the pressure in the fuel pipe can be detected by the strain gauge.

In a fourth aspect based on the second and third aspects, the control circuit controls a voltage and a time for energizing the linear shape memory alloy in accordance with the pressure in the fuel pipe.

According to a fifth aspect of the present invention, in the second aspect, a check valve for allowing only the fuel from the high-pressure pump to flow into the discharge side of the high-pressure pump, and a connecting pipe connecting each fuel injection valve to the fuel pipe. Non-return valves that allow only the flow of fuel from the fuel pipe are provided in the sections, and the piston can be operated as a pump by repeatedly energizing the linear shape memory alloy and stopping the energization.

According to a sixth aspect of the present invention, there is provided a fuel injection system for an engine having a common rail type fuel pipe for accumulating fuel sent from a high pressure pump and leading the fuel to fuel injection valves of each cylinder. It is made of a memory alloy, and the shape memory alloy contracts in a direction of decreasing the volume in the fuel pipe by energizing the shape memory alloy.

According to a seventh aspect of the present invention, in the sixth aspect, a check valve for permitting only the inflow of fuel from the high-pressure pump to a discharge side portion of the high-pressure pump, and a connecting pipe for connecting each fuel injection valve with the fuel pipe. Non-return valves that allow only the flow of fuel from the fuel pipe are provided in the sections, and the shape memory alloy can be operated as a pump by repeating the energization and the stop of the energization of the shape memory alloy.

[0013]

According to the first to fourth and sixth aspects of the present invention, a higher injection pressure of the fuel injection valve is obtained than at the time of starting the engine, the injected fuel is sufficiently atomized, and the fuel efficiency and the exhaust performance are improved. On the other hand, since the fuel in the fuel pipe is pressurized by the shape memory alloy, the structure can be simplified, the space can be hardly taken, and the cost can be reduced.

According to the fifth and seventh aspects, when the fuel pressure in the fuel pipe does not reach the set fuel pressure or the fuel pressure rises slowly due to the energization of the shape memory alloy,
The fuel pressure can be increased by repeating the energization and the energization stop of the shape memory alloy.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a fuel system of a direct injection type engine. 1 is a fuel tank, 2 is a low-pressure fuel pump, 3 is a filter, 4 is a low-pressure pressure regulator, and 5 is a fuel sent from the low-pressure fuel pump 2. High-pressure fuel pump driven by an engine, which boosts the pressure and sends it to the common rail fuel pipe 6;
Denotes a high pressure regulator, and 8 denotes a fuel injection valve of each cylinder connected to the common rail fuel pipe 6.

The fuel from the high-pressure fuel pump 5 is stored in the common rail fuel pipe 6 at a set pressure of the high-pressure pressure regulator 7 and is injected from each fuel injection valve 8 into each cylinder.

As shown in FIG. 2 and FIG.
A plurality of slots 10 having a predetermined length are formed at equal intervals in the circumferential direction along the pipeline as shown in FIG.
1 is slidably fitted via a seal 12 so that high-pressure fuel in the pipe 6 does not leak outside in the radial direction of the pipe 6.

Then, on the outer periphery of these pistons 11,
A wire 13 made of a shape memory alloy is wound along the longitudinal direction of the piston 11 and the pipe 6 in a state in which these outer circumferences are projected somewhat outward from the outer peripheral surface of the common rail fuel pipe 6.

The wire 13 contracts when the temperature of the wire 13 exceeds the transformation temperature, and expands to the original length when the temperature falls below the transformation temperature. The wire 13 is formed of a shape memory alloy such as Ti-Ni, Cu-Zn-Al. Is done.

A connection terminal 14 is provided at an end of the wire 13, and is connected to a control circuit 16 via a wiring 15. When the voltage of the power supply 17 is applied to the wire 13, the temperature of the wire 13 rapidly rises due to the heat generated by itself (heating with current resistance) and contracts. Due to this contraction, each piston 11 is tightened and moved in a direction to reduce the volume of the common rail fuel pipe 6, and the fuel in the common rail fuel pipe 6 is pressurized.

Further, since the fuel in the common rail fuel pipe 6 is pressurized by the contraction of the wire rod 13,
The strain gauge 1 detects the expansion and contraction of the wire 13 as a pressure sensor for detecting the fuel pressure in the common rail fuel pipe 6.
8 is pasted.

The control circuit 16 controls the power supply to the wire 13 based on the signal of the strain gauge 18 at the time of starting the engine and starts the engine.

Next, the contents of the control will be described. As shown in FIG. 4, when the ignition switch is turned on, the signal of the strain gauge 18 is read in step 1 and the fuel pressure Pc in the common rail fuel pipe 6 is detected.

In step 2, the fuel pressure Pc is compared with a set fuel pressure Pinit. When the fuel pressure Pc is lower than the set fuel pressure Pinit, the process proceeds to Step 3.

In step 3, the energizing voltage and energizing time to the wire 13 are calculated. In this case, the lower the fuel pressure Pc, the higher the energization voltage and the longer the energization time.

In step 4, the voltage of the power supply 17 is set to the calculated energizing voltage, and the wire 1
3 and return to step 1.

Then, the fuel pressure Pc becomes equal to the set fuel pressure Pinit.
Then, the routine proceeds to step 5, where the engine is started (starter driving, fuel injection of the fuel injection valve 8 is started, etc.).

With this configuration, when the engine is started, the fuel pressure Pc in the common rail fuel pipe 6 is set to the set fuel pressure.
When it is lower than Pinit, a voltage is applied to the wire 13 made of the shape memory alloy according to the fuel pressure Pc, the temperature of the wire 13 rises, and the wire 13 contracts. Due to the contraction of the wire 13, each piston 11 is tightened and moved in a direction to decrease the volume of the common rail fuel pipe 6, the fuel in the common rail fuel pipe 6 is pressurized, and the fuel pressure Pc reaches the set fuel pressure Pinit. Then, the engine is started. FIG. 5 shows the fuel pressure Pc in the common rail fuel pipe 6.
The following shows an example of the rise.

Therefore, a high injection pressure of the fuel injection valve 8 is obtained from the time of engine start, and the engine is operated in a state in which the injected fuel is sufficiently atomized, thereby ensuring good fuel efficiency and exhaust performance. can do.

On the other hand, a wire 13 made of a shape memory alloy is wound around the outer periphery of the piston 11 which makes the volume of the common rail fuel pipe 6 variable, and the volume of the common rail fuel pipe 6 is reduced by contraction of the wire 13 due to energization. Because of the configuration that reduces and pressurizes the fuel in the common rail fuel pipe 6,
The structure can be simplified, the space can be hardly taken, and the cost can be reduced.

When the wire 13 is energized, the fuel pressure Pc in the common rail fuel pipe 6 is increased by the set fuel pressure Pini.
When the pressure does not reach t, or when the fuel pressure Pc rises slowly, the fuel pressure Pc is increased by repeatedly energizing and stopping the energization of the wire 13, that is, expanding and contracting the wire 13, and operating the piston 11 as a pump. May be. However, in this case, as shown in FIG.
A check valve 20 that permits only the inflow of fuel from the high-pressure fuel pump 5 into the discharge side of the fuel tank, and a fuel inflow from the common rail fuel pipe 6 into each connecting pipe portion 21 that connects the common rail fuel pipe 6 and each fuel injection valve 8. A check valve 22 that allows only one is provided.

FIG. 6 shows a second embodiment in which a part of a common rail fuel pipe 30 is formed of a shape memory alloy.
By energizing the shape memory alloy, the volume in the common rail fuel pipe 30 is reduced.

In this case, a shape memory alloy (for example, Ti—Ni, Cu—Zn—A) is connected to one end of the common rail fuel pipe 30.
1) is attached. The inside of the pipe 31 and the inside of the pipe 30 are communicated, and the end of the pipe 31 is closed.
Wiring 32 for energizing the tube 31 is connected to both ends of the tube 31, and energization of the tube 31 is controlled by a control circuit.

When the tube 31 is energized, the temperature of the tube 31 rises and the tube 31 contracts in the direction of the pipe, and the contraction pressurizes the fuel in the common rail fuel pipe 30.

According to this, the structure becomes extremely simple.
A strain gauge for detecting the expansion and contraction of the tube 31 is attached to the outer periphery of the tube 31 and can be used as a pressure sensor for detecting the fuel pressure in the common rail fuel pipe 30.

FIG. 7 shows a third embodiment. In the second embodiment, the check valve 4 which allows only the fuel from the high-pressure fuel pump to flow into the discharge side of the high-pressure fuel pump is used.
Each of the connection pipe portions 41 connecting the fuel injection valves to the 0 and common rail fuel pipes 30 is provided with a check valve 42 that allows only fuel to flow from the common rail fuel pipe 30.

In this way, when the fuel pressure Pc in the common rail fuel pipe 30 does not reach the set fuel pressure Pinit or when the fuel pressure Pc rises slowly due to the energization of the tube material 31, the tube material 31 is energized and energized. The fuel pressure Pc can be increased by stopping the operation, that is, repeating the expansion and contraction of the tube 31 and operating the tube 31 as a pump.

[Brief description of the drawings]

FIG. 1 is a fuel system diagram of a first embodiment.

FIG. 2 is a sectional view of a main part.

FIG. 3 is a configuration diagram showing a cross section taken along line AA of FIG. 2 and a control system.

FIG. 4 is a control flowchart.

FIG. 5 is a characteristic diagram showing an example of a rise in fuel pressure.

FIG. 6 is a sectional view of a main part of the second embodiment.

FIG. 7 is a sectional view of a main part of a third embodiment.

[Explanation of symbols]

 Reference Signs List 5 high-pressure fuel pump 6 common rail fuel pipe 8 fuel injection valve 11 piston 13 wire 16 control circuit 17 power supply 18 strain gauge 20,22 check valve 30 common rail fuel pipe 31 pipe 40,42 check valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norioto Nakao 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Yoshihiko Ishii 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. F term (reference) 3G066 AA07 AB02 AC09 AD12 BA03 BA05 BA12 BA17 BA61 BA67 CB01 CB09 CB13S CB13U CD15 CD22 CD25 CD26 DB01 DC18

Claims (7)

[Claims] 1. A fuel injection device for an engine having a common rail type fuel pipe for accumulating fuel sent from a high pressure pump and guiding the fuel to a fuel injection valve of each cylinder, wherein a movable member having a variable volume in the fuel pipe. Wherein the movable member or the actuator of the movable member is made of a shape memory alloy, and a control circuit for operating the movable member by energizing the shape memory alloy is provided. 2. A fuel injection device for an engine having a common rail type fuel pipe for accumulating fuel sent from a high pressure pump and leading the fuel to a fuel injection valve of each cylinder, wherein a piston for changing a volume in the fuel pipe is provided. A linear shape memory alloy is wound around the outer periphery of the piston so as to tighten the piston in the direction of decreasing the volume in the fuel pipe, and a control circuit is provided for controlling energization of the linear shape memory alloy. A high pressure pipe for fuel injection characterized by the above. 3. The fuel injection high-pressure pipe according to claim 2, wherein a strain gauge is attached to the linear shape memory alloy, and the pressure in the fuel pipe can be detected by the strain gauge. 4. The fuel injection system according to claim 2, wherein the control circuit controls a voltage and a time for energizing the linear shape memory alloy in accordance with a pressure in the fuel pipe. High pressure piping. 5. A check valve for permitting only inflow of fuel from the high-pressure fuel pump to a discharge side portion of the high-pressure fuel pump, and a connecting pipe portion connecting the fuel pipe and each fuel injection valve to a fuel pipe from the fuel pipe. 3. The fuel according to claim 2, wherein check valves that allow only inflow are provided, and the piston is operable as a pump by repeating energization of the linear shape memory alloy and stoppage of energization. High pressure pipe for injection. 6. A fuel injection device for an engine having a common rail type fuel pipe which accumulates fuel sent from a high pressure pump and guides the fuel to a fuel injection valve of each cylinder, wherein a part of the fuel pipe is formed of a shape memory alloy. A high-pressure fuel injection pipe characterized in that the shape memory alloy contracts in the direction of decreasing the volume in the fuel pipe by energizing the shape memory alloy. 7. A check valve for permitting only inflow of fuel from the high-pressure fuel pump to a discharge side portion of the high-pressure fuel pump, and a connecting pipe portion connecting each fuel injection valve with each fuel injection valve, for supplying fuel from the fuel pipe to each connection pipe. Providing check valves each allowing only inflow, energizing the shape memory alloy, by repeating energization stop,
The high pressure fuel injection pipe according to claim 6, wherein the shape memory alloy is operable as a pump.