JP4985546B2 - Fuel injection nozzle - Google Patents

Description

  The present invention relates to a fuel injection nozzle that injects fuel into a combustion chamber of a diesel engine.

  In order to achieve both low emission and high output in a diesel engine, it is required to change the fuel injection rate in accordance with the operating conditions of the diesel engine. In order to realize this requirement, a fuel injection nozzle capable of changing the nozzle hole area in two stages is known (for example, see Patent Document 1).

  The fuel injection nozzle includes an inner needle and an outer needle. In a low load region where low emission is required, only the outer needle lifts and injects fuel only from some of the injection holes. In the high load region where high output is required, the inner needle is also lifted to inject fuel from a plurality of injection holes.

Further, in this fuel injection nozzle, the piston portion of the outer needle is slidably inserted into a cylinder forming the control chamber, and when the fuel pressure in the control chamber is high, the outer needle is closed by the pressure, When the fuel pressure in the control chamber is switched to a low pressure, the outer needle is opened.
JP 2006-152893 A

  However, in the conventional fuel injection nozzle, since the high pressure fuel pressure is constantly acting on the outer peripheral surface of the cylinder, when the fuel pressure in the control chamber is switched to low pressure, The cylinder is deformed (contracted) due to the pressure difference with the pressure acting on the outer peripheral surface of the cylinder, and the clearance between the outer needle and the cylinder is reduced. As a result, there is a problem in that sliding failure occurs during the lifting of the outer needle, and it is difficult for the outer needle to rise during a high lift, thereby suppressing the injection amount.

  On the other hand, in order to avoid sliding failure, the clearance between the outer needle and the cylinder is increased (usually set to about 2 μm, for example, set to about 10 μm), the outer periphery of the cylinder and the control chamber The pressure in the control chamber is less likely to decrease when the outer needle is raised, and the pressure in the control chamber is likely to rise when the outer needle is lowered. There is. Further, when the outer needle is lowered, the pressure in the control chamber is likely to increase, so that the valve closing speed is increased and the wear resistance performance of the valve seat of the fuel injection nozzle is deteriorated.

  In view of the above points, the present invention prevents a sliding failure of a needle and an increase in leakage from a clearance caused by deformation of a cylinder in a fuel injection nozzle in which a piston portion of a needle is slidably inserted into a cylinder. With the goal.

In order to achieve the above object, according to the first aspect of the present invention, a nozzle body (113) having a nozzle hole (1132, 1133) serving as a fuel outlet and a valve seat (1131) through which the nozzle hole (1132, 1133) opens. ) And a control chamber (117) in which the fuel pressure can be switched between high pressure and low pressure, and a cylinder (115) on which the pressure of the high-pressure fuel acts on the outer peripheral surface, and one end side is in contact with and away from the valve seat (1131) The control chamber (117) includes a needle (111) that opens and closes the nozzle holes (1132, 1133), and a piston portion (1111) formed on the other end is slidably inserted into the cylinder (115 ). The inner peripheral surface of the cylinder (115) when the pressure on the cylinder (115) is equal to the pressure acting on the outer peripheral surface of the cylinder (115) is directed from the side closer to the control chamber (117) toward the far side. The cylinder (115) and the piston portion (1111) when the pressure in the control chamber (117) is equal to the pressure acting on the outer peripheral surface of the cylinder (115) Is configured such that the side closer to the control chamber (117) is larger than the side farther, and the pressure in the control chamber (117) is equal to the pressure acting on the outer peripheral surface of the cylinder (115). The difference between the inner diameter of the cylinder (115) close to the control chamber (117) and the inner diameter of the cylinder (115) far from the control chamber (117) is that when the pressure in the control chamber (117) is switched to a low pressure. The cylinder (115) is set to be equal to the difference between the reduced diameter on the side closer to the control chamber (117) and the reduced diameter on the side far from the control chamber (117) .

  According to this, when the fuel pressure in the control chamber (117) is switched to a low pressure, the cylinder (by the pressure difference between the fuel pressure in the control chamber (117) and the pressure acting on the outer peripheral surface of the cylinder (115) ( 115), the clearance between the needle (111) and the cylinder (115) is greatly reduced on the side closer to the control chamber (117) than on the side farther away. As a result, the clearance closer to the control chamber (117) is reduced. The clearance and the clearance on the far side are substantially equal. Therefore, it is possible to prevent the sliding failure of the needle (111) and the increase in leakage from the clearance due to the deformation of the cylinder (115).

In the invention according to claim 2 , the nozzle body (113) having the nozzle hole (1132, 1133) serving as the fuel outlet and the valve seat (1131) in which the nozzle hole (1132, 1133) opens, and the pressure of the fuel are A control chamber (117) that can be switched between high pressure and low pressure is formed, and a cylinder (115) on which the pressure of high-pressure fuel acts on the outer peripheral surface, and one end side of the control chamber (117) are in contact with and separated from the valve seat (1131). ) And a piston part (1111) formed on the other end side is provided with a needle (111) slidably inserted into the cylinder (115), and the piston part (1111) is provided in the control chamber (117). ), The pressure in the control chamber (117) and the pressure acting on the outer peripheral surface of the cylinder (115) are reduced. The clearance between the cylinder (115) and the piston portion (1111) in the new state is configured such that the side closer to the control chamber (117) is larger than the side farther, and the pressure in the control chamber (117) When the pressure acting on the outer peripheral surface of the cylinder (115) is equal, the outer diameter of the piston portion (1111) closer to the control chamber (117) and the outer diameter farther from the control chamber (117) The difference is that when the pressure in the control chamber (117) is switched to a low pressure, the diameter of the cylinder (115) closer to the control chamber (117) and the diameter smaller than the control chamber (117) are reduced. It is characterized by being set equal to the difference from the quantity .

According to this, the same effect as that of the first aspect of the invention can be obtained. Further , the processing is easier when the outer peripheral surface of the piston part (1111) is conical than when the inner peripheral surface of the cylinder (115) is conical.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a schematic diagram illustrating a configuration of a fuel injection device including a fuel injection nozzle according to the first embodiment.

  As shown in FIG. 1, a fuel injection control device includes a fuel injection valve 1 for injecting fuel into a diesel engine (hereinafter referred to as an engine), a pressure accumulator 2 for storing high-pressure fuel, a fuel tank 3 for storing fuel in a low-pressure state, and a fuel A supply pump 4 that supplies high pressure to the accumulator 2 with the fuel sucked up from the tank 3 and a control circuit (not shown) for controlling the operation of the fuel injection valve 1 and the supply pump 4 are provided.

  The fuel injection valve 1 includes a fuel injection nozzle 11 that injects fuel when the valve is opened, and a drive unit 12 that drives an outer needle 111 and an inner needle 112 of the fuel injection nozzle 11.

  In the fuel injection nozzle 11, a cylindrical outer needle 111 is slidably inserted into a metal bottomed cylindrical nozzle body 113, and a columnar inner needle 112 is slidable in the outer needle 111. Has been inserted.

  A tapered valve seat 1131 is formed on one end side of the nozzle body 113, and a first injection hole 1132 and a second injection hole 1133 for injecting high-pressure fuel into the engine are opened in the valve seat 1131. The first nozzle hole 1132 is located on the upstream side of the second nozzle hole 1133.

 A disc-shaped plate 114 is sandwiched between the nozzle body 113 and the drive unit 12. An enlarged diameter hole 1134 is formed on the other end side of the nozzle body 113, and the inner diameter of the enlarged diameter hole 1134 is set sufficiently larger than the outer diameter of the outer needle 111.

  A tapered seat surface is formed on one end side of the outer needle 111, and the first nozzle hole 1132 opens and closes when the seat surface of the outer needle 111 contacts and separates from the valve seat 1131 as the outer needle 111 reciprocates. Is done.

  One end side of the inner needle 112 protrudes from the outer needle 111, and a tapered seat surface is formed at the protruding portion, and the seat surface of the inner needle 112 moves to the valve seat 1131 as the inner needle 112 reciprocates. The second nozzle hole 1133 is opened and closed by contacting and separating. The other end side of the inner needle 112 protrudes from the outer needle 111, and a collar portion 1121 is formed at the protruding portion.

  A cylindrical cylinder 115 and a first spring 116 are disposed in the enlarged diameter hole portion 1134. The first spring 116 is sandwiched between the outer needle 111 and the cylinder 115, urges the outer needle 111 in the valve closing direction, and presses the cylinder 115 against the plate 114.

  A piston portion 1111 is formed on the other end side of the outer needle 111, and this piston portion 1111 is slidably inserted into the cylinder 115. A control chamber 117 is formed by the inner periphery of the plate 114, the inner periphery of the cylinder 115, the other end of the outer needle 111, and the other end of the inner needle 112. A second spring 118 that urges the inner needle 112 in the valve closing direction is disposed in the control chamber 117. Further, the outer needle 111 and the inner needle 112 are urged in the valve closing direction by the pressure in the control chamber 117.

  The drive unit 12 includes a drive unit body 121, and a high-pressure fuel passage 1211 connected to the pressure accumulator 2 is formed in the drive unit body 121. The high-pressure fuel supplied from the pressure accumulator 2 passes through the high-pressure fuel passage 1211, the through-hole 1141 of the plate 114, the outer space of the cylinder 115, and the like toward the first injection hole 1132 and the second injection hole 1133. It comes to be supplied. Further, the outer needle 111 and the inner needle 112 are urged in the valve opening direction by the pressure of the fuel supplied to the first nozzle hole 1132 and the second nozzle hole 1133 side.

  A branch high-pressure fuel passage 1212 branched from the high-pressure fuel passage 1211 and connected to the control chamber 117 and a low-pressure fuel passage 1213 connecting the control chamber 117 to the fuel tank 3 are formed in the drive body 121. In addition, a control valve 122 that selectively connects the branch high-pressure fuel passage 1212 and the low-pressure fuel passage 1213 to the control chamber 117 is accommodated in the drive unit body 121.

  2 and 3 are enlarged sectional views showing the vicinity of the control chamber 117 in the fuel injection nozzle. More specifically, FIG. 2 shows a state in which the control chamber 117 is connected to the branch high-pressure fuel passage 1212 and the pressure in the control chamber 117 and the pressure acting on the outer peripheral surface of the cylinder 115 are equal. FIG. 3 shows a state where the control chamber 117 is connected to the low pressure fuel passage 1213 and the pressure acting on the outer peripheral surface of the cylinder 115 is higher than the pressure of the control chamber 117.

  In the present embodiment, when the pressure in the control chamber 117 is equal to the pressure acting on the outer peripheral surface of the cylinder 115, the inner peripheral surface of the cylinder 115 is far from the side closer to the control chamber 117 as shown in FIG. It has a conical shape whose diameter decreases toward the side (that is, the side where the piston portion 1111 is inserted). On the other hand, the outer diameter of the piston portion 1111 of the outer needle 111 is constant regardless of the pressure in the control chamber 117 or the pressure acting on the outer peripheral surface of the cylinder 115. Therefore, the clearance between the cylinder 115 and the piston portion 1111 is larger on the side closer to the control chamber 117 than on the far side when the pressure in the control chamber 117 is equal to the pressure acting on the outer peripheral surface of the cylinder 115. Yes. Specifically, the clearance between the cylinder 115 and the piston portion 1111 when the pressure in the control chamber 117 is equal to the pressure acting on the outer peripheral surface of the cylinder 115 is about 2 μm on the side close to the control chamber 117. The distance from the control room 117 is about 10 μm.

  Next, the operation of the fuel injection control device configured as described above will be described. In FIG. 1, a supply pump 4 is driven by an engine and supplies the fuel sucked from the fuel tank 3 to a pressure accumulator 2 at a high pressure. Further, the fuel discharge amount of the supply pump 4 is controlled by the control circuit so that the fuel pressure in the accumulator 2 becomes the target pressure.

  In a state where the control valve 122 connects the branch high-pressure fuel passage 1212 and the control chamber 117, high-pressure fuel is introduced into the control chamber 117, and the outer needle 111 and the inner needle 112 are urged toward the valve close by the pressure. The outer needle 111 and the inner needle 112 are in contact with the valve seat 1131 so that the first nozzle hole 1132 and the second nozzle hole 1133 are closed. At this time, since the pressure in the control chamber 117 and the pressure acting on the outer peripheral surface of the cylinder 115 are equal, the clearance between the cylinder 115 and the piston portion 1111 is far from the side closer to the control chamber 117 as shown in FIG. It is larger than the side.

  On the other hand, when the control valve 122 connects the low pressure fuel passage 1213 and the control chamber 117, the pressure in the control chamber 117 is low (substantially atmospheric pressure), and the outer needle 111 and the inner needle 112 are closed by the pressure. The force energizing is almost zero. The outer needle 111 is urged in the valve opening direction by the pressure of the fuel supplied to the first nozzle hole 1132 and the second nozzle hole 1133, and the outer needle 111 is lifted against the first spring 116, The outer needle 111 is separated from the valve seat 1131 to open the first injection hole 1132, and fuel is injected from the first injection hole 1132.

  Further, the outer needle 111 is engaged with the flange 1121 of the inner needle 112 by the lift of the outer needle 111, and then the outer needle 111 and the inner needle 112 are lifted against the first spring 116 and the second spring 118. Accordingly, the inner needle 112 is also separated from the valve seat 1131 to open the second injection hole 1133, and fuel is injected from the first injection hole 1132 and the second injection hole 1133.

  At this time, due to the pressure difference between the pressure in the control chamber 117 and the pressure acting on the outer peripheral surface of the cylinder 115, the cylinder 115 is deformed so as to be reduced in diameter. Specifically, the deformation amount of the portion of the cylinder 115 facing the control chamber 117 is larger than the deformation amount of the portion where the piston part 1111 is inserted. For this reason, the clearance between the cylinder 115 and the piston portion 1111 is greatly reduced on the side closer to the control chamber 117 than on the far side. 3 indicates the shape of the inner peripheral surface of the cylinder 115 when the pressure in the control chamber 117 and the pressure acting on the outer peripheral surface of the cylinder 115 are equal.

  Here, when the pressure in the control chamber 117 and the pressure acting on the outer peripheral surface of the cylinder 115 are equal, the difference between the inner diameter of the cylinder 115 closer to the control chamber 117 and the inner diameter farther from the control chamber 117 is When the pressure in the control chamber 117 is switched to a low pressure, it is set equal to the difference between the diameter reduction amount on the cylinder 115 nearer to the control chamber 117 and the diameter reduction on the side farther from the control chamber 117. .

  As a result, when the pressure in the control chamber 117 is switched to a low pressure, the clearance on the side closer to the control chamber 117 and the clearance on the far side are substantially equal, as shown in FIG. Then, by setting the clearance when the cylinder 115 is not deformed so that the clearance at this time becomes an appropriate value, the sliding failure of the outer needle 111 due to the deformation of the cylinder 115 and the clearance are eliminated. Increase in leakage can be prevented.

(Second Embodiment)
A second embodiment of the present invention will be described. 4 and 5 are cross-sectional views of the main part showing the vicinity of the control chamber in the fuel injection nozzle according to the second embodiment. More specifically, FIG. 4 shows a state where the pressure in the control chamber 117 is equal to the pressure acting on the outer peripheral surface of the cylinder 115, and FIG. The state when the pressure which acts on the outer peripheral surface of 115 is high is shown.

  In the present embodiment, the control valve 122 (see FIG. 1) acts on the branch high-pressure fuel passage 1212 (see FIG. 1) and the control chamber 117, that is, the pressure in the control chamber 117 and the outer peripheral surface of the cylinder 115. When the pressure is equal, the inner diameter of the cylinder 115 is constant as shown in FIG. On the other hand, the outer peripheral surface of the piston portion 1111 of the outer needle 111 is a cone whose diameter increases from the side closer to the control chamber 117 to the side farther from the pressure acting on the outer peripheral surface of the cylinder 115 or the pressure of the control chamber 117. It is in the shape.

  Therefore, the clearance between the cylinder 115 and the piston portion 1111 is larger on the side closer to the control chamber 117 than on the far side when the pressure in the control chamber 117 is equal to the pressure acting on the outer peripheral surface of the cylinder 115. Yes.

  On the other hand, in a state where the control valve 122 connects the low pressure fuel passage 1213 (see FIG. 1) and the control chamber 117, that is, in a state where the pressure acting on the outer peripheral surface of the cylinder 115 is higher than the pressure in the control chamber 117. Due to the pressure difference between the pressure 117 and the pressure acting on the outer peripheral surface of the cylinder 115, the cylinder 115 is deformed so as to reduce its diameter. Specifically, the deformation amount of the portion of the cylinder 115 facing the control chamber 117 is larger than the deformation amount of the portion where the piston part 1111 is inserted. For this reason, the clearance between the cylinder 115 and the piston portion 1111 is greatly reduced on the side closer to the control chamber 117 than on the far side. 5 indicates the shape of the inner peripheral surface of the cylinder 115 when the pressure in the control chamber 117 and the pressure acting on the outer peripheral surface of the cylinder 115 are equal.

  Here, when the pressure in the control chamber 117 and the pressure acting on the outer peripheral surface of the cylinder 115 are equal, the outer diameter of the piston portion 1111 closer to the control chamber 117 and the outer diameter farther from the control chamber 117 Is set equal to the difference between the reduced diameter on the cylinder 115 side closer to the control chamber 117 and the reduced diameter on the side farther from the control chamber 117 when the pressure in the control chamber 117 is switched to a low pressure. Has been.

  As a result, as shown in FIG. 5, the clearance on the side closer to the control chamber 117 and the clearance on the far side become substantially equal. Then, by setting the clearance when the cylinder 115 is not deformed so that the clearance at this time becomes an appropriate value, the sliding failure of the outer needle 111 due to the deformation of the cylinder 115 and the clearance are eliminated. Increase in leakage can be prevented.

  Further, as in the present embodiment, the process of making the outer peripheral surface of the piston portion 1111 conical is easier than the case of making the inner peripheral surface of the cylinder 115 conical.

(Other embodiments)
In each of the above embodiments, the fuel injection nozzle 11 in which the needle is divided into the outer needle 111 and the inner needle 112 is shown. However, in the present invention, the needle is not divided into the outer needle 111 and the inner needle 112. The present invention can also be applied to the type of fuel injection nozzle 11.

  Moreover, in each said embodiment, although the plate 114 and the cylinder 115 were made into a different body, you may form the plate 114 and the cylinder 115 integrally.

It is a typical figure showing composition of a fuel injection device provided with a fuel injection nozzle concerning a 1st embodiment of the present invention. It is sectional drawing which shows the principal part of the fuel-injection nozzle of FIG. FIG. 3 is a cross-sectional view of a main part of a fuel injection nozzle showing an operating state under operating conditions different from those in FIG. 2. It is sectional drawing of the principal part which shows the fuel-injection nozzle which concerns on 2nd Embodiment of this invention. It is principal part sectional drawing of the fuel-injection nozzle which shows the operation state on the operating conditions different from FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 111 Needle 113 Nozzle body 115 Cylinder 117 Control chamber 1111 Piston part 1131 Valve seat 1132 Injection hole 1133 Injection hole

Claims (2)

A nozzle body (113) having a nozzle hole (1132, 1133) serving as a fuel outlet and a valve seat (1131) in which the nozzle hole (1132, 1133) opens;
A cylinder (115) that forms a control chamber (117) in which the pressure of the fuel can be switched between a high pressure and a low pressure, and on which the pressure of the high-pressure fuel acts on the outer peripheral surface;
One end side contacts and separates from the valve seat (1131) to open and close the nozzle hole (1132, 1133), and a piston portion (1111) formed on the other end side is slidably inserted into the cylinder (115). Needle (111)
The inner peripheral surface of the cylinder in the state the pressure which acts equal to the outer peripheral surface (115) of the pressure and the cylinder (115) of said control chamber (117) is farther from the side close to the control chamber (117) by being formed in a conical shape that the diameter toward the side is small, when the state and equal pressure acting on the outer peripheral surface of the pressure and the cylinder (115) of said control chamber (117), said cylinder (115 ) and the clearance between the piston portion (1111) is a side closer to said control chamber (117) is configured to a size Kunar so than the far side,
When the pressure in the control chamber (117) and the pressure acting on the outer peripheral surface of the cylinder (115) are equal, the inner diameter of the cylinder (115) closer to the control chamber (117) and the control chamber The difference from the inner diameter on the side farther from (117) is the reduced diameter on the side closer to the control chamber (117) in the cylinder (115) when the pressure in the control chamber (117) is switched to a low pressure. The fuel injection nozzle is set to be equal to the difference between the amount and the amount of diameter reduction on the side far from the control chamber (117). A nozzle body (113) having a nozzle hole (1132, 1133) serving as a fuel outlet and a valve seat (1131) in which the nozzle hole (1132, 1133) opens;
A cylinder (115) that forms a control chamber (117) in which the pressure of the fuel can be switched between a high pressure and a low pressure, and on which the pressure of the high-pressure fuel acts on the outer peripheral surface;
One end side contacts and separates from the valve seat (1131) to open and close the nozzle hole (1132, 1133), and a piston portion (1111) formed on the other end side is slidably inserted into the cylinder (115). Needle (111)
The piston portion (1111) is formed in a conical shape whose diameter increases from a side closer to the control chamber (117) to a side farther from the side, so that the pressure in the control chamber (117) and the cylinder (115) are increased. in the state is equal to the pressure acting on the outer peripheral surface of the clearance between said cylinder (115) and said piston unit (1111) is larger than the side is far closer to the control chamber (117) Kunar Configured as
When the pressure in the control chamber (117) and the pressure acting on the outer peripheral surface of the cylinder (115) are equal, the outer diameter of the piston portion (1111) near the control chamber (117) and the The difference from the outer diameter on the side far from the control chamber (117) is the side closer to the control chamber (117) in the cylinder (115) when the pressure in the control chamber (117) is switched to a low pressure. The fuel injection nozzle is set to be equal to the difference between the diameter reduction amount and the diameter reduction amount far from the control chamber (117).

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