JP3918253B2 - Safety device for accumulator fuel injector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a safety device in an accumulator fuel injection apparatus in which high pressure fuel stored in an accumulator chamber or a common rail is injected into a combustion chamber via a fuel injection nozzle provided in each cylinder of an engine. .
[0002]
[Prior art]
Conventionally, fuel is pressurized by a high pressure fuel supply pump driven by an engine or a plunger device and stored in a pressure accumulating chamber called a common rail, and the high pressure fuel in the pressure accumulating chamber or common rail is provided in each cylinder of the engine. A pressure accumulation type fuel injection device in which fuel is injected into a fuel chamber by a fuel injection nozzle is known.
[0003]
The schematic configuration of this type of accumulator fuel injection device will be described with the aid of FIG. 1 showing a vehicular diesel engine including a safety device according to the present invention for convenience, and the above-described configuration shown in FIG. 3 and FIG. This will be described with reference to a sectional view of the safety device.
[0004]
First, in FIG. 1 showing a schematic configuration of a vehicular diesel engine including a pressure accumulating fuel injection device, reference numeral 10 generally indicates the engine, and 12 is an electromagnetically operated fuel injection nozzle provided in each cylinder of the engine. It is. As the fuel injection nozzle 12, for example, one having a structure as disclosed in JP-A-4-241767 and JP-A-4-252860 can be arbitrarily adopted. Each fuel injection nozzle 12 operates in response to the drive output of the control unit or control means 14 and injects fuel into the combustion chamber of each cylinder with an appropriate injection timing and injection amount according to the operating state of the engine 10. The control unit or control means 14 indicates the signal output N _e of the rotation speed sensor 16 that indicates the operating state of the engine, the signal output L _e of the load sensor 18 that detects the amount of depression of the accelerator pedal, and the coolant temperature of the engine 10. In response to the signal output T _w of the temperature sensor 20, the signal output V _h of the vehicle speed sensor 22 for detecting the vehicle speed and other necessary signals, the fuel injection amount and the injection timing are set.
[0005]
The fuel injection nozzle 12 is connected to a pressure accumulating chamber or a common rail 28 via a fuel injection pipe 24 that forms part of the fuel passage and a safety device 26 that will be described in detail later. The pressure accumulating chamber 28 stores high-pressure fuel pressurized by a variable-capacity high-pressure fuel supply pump or plunger device 30 therein. In the accumulator 28, the pressure sensor 32 is provided, the fuel pressure signal P _f of the pressure sensor 32 is supplied to the control unit or control means 14, the control unit or control means 14 the fuel pressure signal P _f In response to this, a drive output is provided to the fuel supply pump or plunger device 30, and as a result, high pressure fuel having a set pressure is stored in the pressure accumulating chamber 28. Instead of the variable capacity fuel supply pump or plunger device 30, a constant capacity pump or plunger device is used to control the opening degree of the reflux amount control valve provided on the discharge side to control the amount of fuel reflux to the fuel tank 34. By controlling, the fuel pressure in the pressure accumulating chamber 28 can also be controlled. The fuel stored in the fuel tank 34 is supplied to the high-pressure fuel supply pump or plunger device 30 by a low-pressure feed pump 36.
[0006]
As shown in FIG. 3, the conventional structure of the safety device 26 includes a hollow cylindrical valve housing 38 screwed into the outer wall of the pressure accumulating chamber 28. A large-diameter hole 40 and a small-diameter hole 42 having a slightly smaller diameter are coaxially provided in the valve housing 38, and the large-diameter hole 40 and the small-diameter hole 42 are connected by a conical portion 44. . The upstream end of the fuel injection pipe 24 is fastened to the opening end of the small-diameter hole 42 by a cap nut 46, and the downstream end of the fuel injection pipe 24 is the electromagnetically operated fuel injection provided in each cylinder of the engine. The fuel inlet of the nozzle 12 is connected.
[0007]
Housed in the large-diameter hole 40 are a slidable floating piston 48 and a cut-off valve made of a ball 50 having a diameter smaller than that of the large-diameter hole 40 but larger than that of the small-diameter hole 42. A spring 52 is inserted into the small-diameter hole 42, and the spring 52 elastically presses the ball 50 toward the pressure accumulating chamber 28 side, that is, the upstream floating piston 48 via a retainer 54.
[0008]
When the combustion injection nozzle 12 of each cylinder is opened for a time set according to the operation state of the engine during the operation of the engine, the fuel that has been filled downstream from the ball 50 in the safety device 26 is injected into the fuel injection. While being injected from the nozzle 12 into the fuel chamber of each cylinder, the high-pressure fuel in the pressure accumulating chamber 28 flows into the large-diameter hole 40 from the fuel inlet passage 56. At this time, the floating piston 48 and the ball 50 are displaced together downstream.
The volume of the large-diameter hole 40 between the center of the ball 50 and the distance X between the circumferential surface with which the ball 50 of the conical portion 44 abuts is formed larger than the maximum injection amount of the fuel injection nozzle 12. Therefore, even if the injection nozzle 12 performs the injection of the maximum injection amount, it is temporarily planned so that the ball 50 does not contact the conical portion 44 and block the communication between the large diameter hole 40 and the small diameter hole 42. .
[0009]
When the injection of the fuel injection nozzle 12 is completed, the ball 50 and the idle piston 48 are returned to the illustrated rest position by the spring 52, and at this time, the fuel in the large-diameter hole 40 causes the oil hole 58 of the idle piston 48 and the outer periphery of the ball 50. And flows downstream of the ball. (Note that a reflected wave generated at the end of fuel injection is propagated into the pressure accumulating chamber 28 in the high-pressure fuel passage including the fuel injection pipe 24, thereby causing variations in the injection timing and injection amount of each cylinder. (A check valve may be installed to prevent this)
[0010]
In the fuel injection device including the safety device 26, a fuel injection pipe 24 of an arbitrary cylinder is damaged, a pipe joint portion such as a cap nut 46 is damaged, or a fuel injection nozzle malfunctions, and a large amount of fuel is generated. When it flows at a time, the ball 50 moves downstream by the distance X or more and engages and engages with the conical portion 44 to close the fuel passage, so that the high pressure fuel from the pressure accumulating chamber 28 is prevented from flowing out. It is configured.
[0011]
The conventional safety device 26 operates effectively when a large amount of fuel suddenly flows out due to a rupture or breakage of the fuel injection pipe 24, but the maximum safety fuel injection amount of the fuel injection nozzle 12 is close thereto. When a large injection amount is injected, the pressure difference between the upstream and downstream sides of the ball 50 causes the ball 50 to malfunction and bite into the conical portion 44, thereby preventing an increase in the output of the engine 10. May stop.
[0012]
Furthermore, there is a problem that it is not possible to stop a small amount of continuous fuel outflow that oozes out from, for example, a slight gap in the pipe joint. This is because the pressure difference between the upstream side and the downstream side of the ball 50 caused by a small amount of continuous fuel outflow is extremely small, and the valve closing position where the ball 50 comes into contact with the conical portion 44 by overcoming the spring 52. This is because it cannot be displaced until.
Even if the amount of fuel leakage in a unit time is very small, the total spillage will of course increase with the accumulation of time, which not only causes a loss of fuel, but also fouls the engine and its surroundings, which is the worst case. There was a risk of fire.
In the figure, reference numeral 60 denotes a plug which is press-fitted into the housing 38 of the safety device 26 and is fixed by caulking to the open end on the pressure accumulating chamber 28 side, and sets the idle position of the floating piston 48 and thus the ball 50. It is.
[0013]
Next, the conventional safety device 26 shown in FIG. 4 does not have the conical portion 44 as shown in FIG. 3 at the connecting portion between the large-diameter hole 40 and the small-diameter hole 42. Alternatively, the cut-off valve 50 does not irreversibly bite into the conical part 44 to block the fuel passage, but the ball 50 is simply brought into contact with the opening end of the small diameter hole 42 to the large diameter hole 40, thereby 3 is different from the safety device 26 shown in FIG. 3 above, except for the fact that the other configuration is substantially different. Are identical. Also, in the safety device 26, just like the safety device 26 in FIG. 3, there is a problem that the engine output is limited or stopped due to a malfunction when the fuel injection amount is large. There is a drawback that a continuous flow based on a small amount of leakage in the fuel passage downstream from the cutoff valve 50 cannot be detected, and leakage cannot be prevented.
[0014]
[Problems to be solved by the invention]
The present invention was devised in view of the above circumstances, such as a fuel injection pipe that constitutes a fuel passage that connects a pressure accumulation chamber or a common rail that stores high-pressure fuel and a fuel injection nozzle provided in each cylinder. A large amount of fuel spillage due to breakage as well as a very small amount of fuel leakage due to slight seal defects in the fuel passage, etc., are reliably responded to prevent wasteful spillage of fuel from the pressure accumulator or common rail The main object of the present invention is to provide a safety device for an accumulator fuel injection device.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a pressure accumulating chamber for accumulating high pressure fuel, a fuel passage for supplying the high pressure fuel in the accumulating chamber to a fuel injection nozzle provided in each cylinder of the engine, and a fuel passage. A cutoff valve that is normally opened and opens the fuel passage, and a damper device connected to the cutoff valve. The damper device has a fuel flow that flows through the cutoff valve so that the fuel injection nozzle It is determined whether the flow is intermittent flow or continuous flow based on leakage, etc., and the cut-off valve is closed during the continuous flow to operate the fuel passage. A safety device for an accumulator fuel injection device is proposed.
[0016]
According to the above configuration, the damper device is connected to the cutoff valve that opens and closes the fuel passage that connects the accumulator chamber or the common rail and the fuel injection nozzle provided in each cylinder of the engine. Intermittent pressure fluctuations in the fuel passage during operation and pressure fluctuations based on continuous fuel flow caused by damage to the fuel passage or leakage from the joint are accurately distinguished and detected. Only in this case, the cut-off valve is closed. As a result, when the fuel injection amount of the engine during normal operation is large, the cutoff valve is not accidentally closed, and fuel outflow due to breakage or leakage of the fuel passage is effectively prevented.
[0017]
In the present invention, the damper device is formed in a valve housing having a piston member coaxially fixed to the cut-off valve and a fuel passage opened and closed by the cut-off valve, and the fuel passage is formed therein. It is preferable to be configured from a damper chamber that is supplied with fuel inside and slidably accommodates the piston member, and between the fuel passage formed in the valve housing and the damper chamber, It is preferable to provide a one-way valve that allows the flow of fuel from the fuel passage side to the damper chamber side.
Furthermore, it is preferable that the piston member is a hollow cylindrical member surrounded on the outer periphery of the cut-off valve, and the damper chamber is an annular chamber that accommodates the piston member with a small gap.
[0018]
With the above preferred configuration, it is possible to provide a compact and compact safety device suitable for being interposed in the accumulator chamber or the fuel passage connecting the common rail and the fuel injection nozzle, and the damper supplied to the damper chamber. Since the fuel itself can be used as the fluid, the structure of the damper device can be simplified.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described below with reference to the schematic configuration diagram of FIG. 1 and the enlarged sectional view of FIG. (Note that the items already described with reference to FIG. 1 in relation to the prior art, and the members and parts substantially the same as or corresponding to those of the conventional safety device 26 shown in FIGS. 3 and 4 are the same. A reference numeral is attached, and a duplicate description is omitted.)
[0020]
In particular, as well shown in FIG. 2, the safety device 26 screwed into the outer wall of the accumulator chamber or common rail 28 storing high-pressure fuel is provided with a valve housing 38. A large-diameter hole 40 and a small-diameter hole 42 that constitute a part of the fuel passage together with the injection pipe 24 and the like are formed in a line on the same axis. A plug 60 having an inflow passage 62 is fixed to the end of the large-diameter hole 40 on the pressure accumulation chamber 28 side by press-fitting or caulking, and the inflow passage 62 communicates with a fuel inlet passage 56 in the pressure accumulation chamber or common rail 28. To do. An upstream end of the fuel injection pipe 24 communicating with the small-diameter hole 42 is fixed to the downstream end of the valve housing 38 by a cap nut 46. The downstream end of the fuel injection pipe 24 is shown in FIG. As shown, the fuel injection nozzle 12 of each cylinder is connected to the fuel inlet.
[0021]
In the large-diameter hole 40, a piston member 64a of a damper device generally indicated by reference numeral 64 is fitted so as to be slidable in the axial direction, and the piston member 64a includes a base portion 64b having a disk shape, A cut-off valve 50 composed of a conical valve arranged in line with the large-diameter hole 40 and the small-diameter hole 42 is screwed and fixed to the central portion of the base portion 64b. A plurality of oil holes 66 communicating with the inflow passage 62 are formed through the base portion 64b in the outer peripheral portion.
[0022]
A ring piston 64c having a hollow cylindrical shape is coaxially projected from the base portion 64b of the piston member 64a toward the downstream side, that is, toward the fuel injection pipe 24. The ring piston 64c has a small diameter hole 42 in the valve housing 38. It is slidably fitted in a hollow cylindrical damper chamber 64d formed so as to be slidable between the ring piston 64c and the damper chamber 64d in the radially outward and inward directions, respectively. t is provided.
[0023]
The vicinity of the downstream end of the damper chamber 64d and the small-diameter hole 42 forming a part of the fuel passage in the valve housing 38 are communicated with each other by a radial communication passage 68. A one-way valve 70 that allows only the flow of fuel from the small-diameter hole 42 side to the damper chamber 64d side is interposed.
[0024]
The one-way valve 70 is slidably accommodated in a valve plug 72 screwed to the valve housing 38, and a spring 74 that normally biases the one-way valve 70 in the closing direction is accommodated in the valve plug 72. Further, in the one-way valve 70, there is always provided a T-type oil passage 76 that allows the damper chamber 64d and the spring accommodating chamber in the valve plug 72 accommodating the spring 74 to communicate with each other.
[0025]
Further, the cut-off valve 50 is seated at the upstream opening end of the small-diameter hole 42, so that the communication between the large-diameter hole 40 and the small-diameter hole 42, that is, the conical surface that blocks the fuel passage in the safety device 26. The valve seat portion 78 is formed, and the large diameter hole 40 is in contact with the base portion 64b to elastically urge the piston member 64a toward the upstream side, that is, the pressure accumulating chamber 28 side. A spring 80 is contracted.
[0026]
In the safety device 26, during normal operation of the engine 10, high-pressure fuel pressurized by the fuel supply pump or plunger device 30 is supplied to the pressure accumulation chamber or common rail 28. When the fuel injection nozzle 12 of each cylinder is opened for a set time at a timing set by the control unit or the control means 14 according to the operating state of the engine 10, the fuel injection pipe 24 and the safety device 26 for each cylinder are included. The high-pressure fuel in the fuel passage is supplied to the fuel chamber of each cylinder, and the engine 10 is operated.
[0027]
Due to the fuel injection for each cylinder, a pressure difference is generated on the upstream and downstream sides of the cutoff valve 50 in the safety device 26, and the cutoff valve 50 is displaced downstream, but is integrated with the cutoff valve 50. The piston member 64a is interlocked, and the ring piston 64c of the piston member 64a slides and displaces in the damper chamber 64d in the valve housing 38 to the downstream side. At this time, a part of the fuel stored in the damper chamber 64d flows out into the large-diameter hole 40 from a minute sliding gap t formed between the ring piston 64c and the damper chamber 64d, so-called. Since the damper action is generated, the cut-off valve 50 does not sit on the valve seat portion 78 even when the fuel injection amount of the fuel injection nozzle 12 is the maximum amount.
[0028]
Therefore, as in the conventional safety device 26 shown in FIGS. 3 and 4, the communication between the large-diameter hole 40 and the small-diameter hole 42 is cut off at the time of maximum fuel injection or a large amount of fuel injection close thereto. Therefore, there is an advantage that the output performance of the engine 10 can be sufficiently exerted without causing problems such as stopping the operation or suppressing the increase in output.
[0029]
When the fuel injection from the fuel injection nozzle 12 is completed, the return spring 80 integrally moves the piston member 64a to the upstream side, that is, the pressure accumulating chamber or the common rail 28 side, and returns to the rest position where it abuts against the plug 60. However, the valve spring 74 is overcome by the pressure drop generated in the damper chamber 64d at this time, and the one-way valve 70 is automatically opened, and the high-pressure fuel in the small diameter hole 42 flows into the damper chamber 64c from the communication path 68. In addition to the spring force of the return spring 80, the return of the cut-off valve 50 to the rest position is promoted.
[0030]
Next, when a small amount of continuous fuel leakage occurs due to insufficient tightening of the joint portion, for example, insufficient tightening of the cap nut 46, or the like in either the pressure accumulating chamber or the fuel passage system from the common rail 28 to the fuel injection nozzle 12. The fuel in the damper chamber 64d flows out through the sliding gap t with the ring piston 64c due to the temporally continuous pressure difference between the upstream side and the downstream side of the cut-off valve 50. Since the off-valve 50 is seated on the valve seat portion 78 and the communication between the large-diameter hole 40 and the small-diameter hole 42 is blocked, fuel leakage downstream from the cutoff valve 50 can be reliably prevented. As a result, it is possible to reliably prevent a fuel loss due to a small amount of leakage for a long time, contamination around the engine room, or in the worst case, a fire that may occur.
[0031]
Further, if a large amount of fuel flows continuously downstream of the cut-off valve 50 due to a breakage or rupture of the fuel injection pipe 24 or a failure of the fuel injection nozzle 12, the cut A large pressure difference is generated between the upstream side and the downstream side of the piston member 64a integrated with the off valve 50. Due to this large pressure difference, the fuel in the damper chamber 64c quickly flows out from the sliding gap t with a squeezing loss, so that the cut-off valve 50 is quickly seated on the valve seat portion 78 and the small diameter hole 42 is formed. As a result, the fuel passage including the large-diameter hole 40 on the upstream side of the cutoff valve 50 and the high-pressure fuel in the accumulator chamber or the common rail 28 are prevented from flowing out.
[0032]
Therefore, a large amount of high-pressure fuel supplied from the damaged fuel passage and the pressure accumulating chamber or common rail 28 and the high-pressure fuel supply pump or plunger device 30 to the pressure accumulating chamber or common rail 28 is ejected into the engine room and In the worst case, there is an advantage that a possible fire can be surely prevented.
[0033]
Further, according to the configuration of FIG. 2, the piston member 64a is disposed integrally and coaxially with the cutoff valve 50, and the ring piston 64c having a hollow cylindrical shape of the piston member 64a is disposed in the valve housing 38. And is slidably fitted in a hollow cylindrical damper chamber 64d coaxially formed on the outer periphery of the small-diameter hole 42, and the fuel itself is supplied as a damper fluid into the damper chamber 64d. Therefore, the safety device 26 can be made small and compact, so that it can be attached to and detached from the pressure accumulating chamber or the common rail 28, in other words, the mountability to the engine can be secured in substantially the same manner as the conventional safety device. it can.
[0034]
In the safety device 26 shown in FIG. 2, the cut-off valve 50 is shown as a conical valve. However, a ball valve or any other valve shape can be appropriately employed as in the conventional device. Further, as the damper device 64 connected to the cut-off valve 50, a hollow cylindrical ring piston 64c disposed coaxially with the cut-off valve 50 and a damper chamber 64d for slidably housing the piston are formed. Although a compact configuration could be realized, one or a plurality of rod-shaped or plunger-shaped damper pistons are connected to the cut-off valve 50, and the damper piston is composed of a normal cylindrical cylinder. An appropriate sliding gap is provided in the damper chamber, and the damper can be changed so as to be slidable together with the valve in a direction parallel to the axis of the cutoff valve 50. Further, as the damper fluid accommodated in the damper chamber, it is most advantageous to use fuel itself, but fluid other than fuel, for example, oil in the engine may be used. Further, in FIG. 2, the safety device 26 is directly attached to the pressure accumulating chamber or common rail 28, but it is obvious that the safety device 26 can be disposed at a proper position in the fuel passage from the pressure accumulating chamber or common rail 28 to the fuel injection nozzle 12.
[0035]
【The invention's effect】
As mentioned above, the safety device for an accumulator fuel injection device according to the present invention supplies an accumulator chamber for accumulating high pressure fuel and the high pressure fuel in the accumulator chamber to fuel injection nozzles provided in each cylinder of the engine. A fuel passage; a cutoff valve that is interposed in the fuel passage and normally opens the fuel passage; and a damper device connected to the cutoff valve, the damper device including the cutoff valve It is determined whether the fuel flow flowing through the fuel is an intermittent flow supplied to the fuel injection nozzle or a continuous flow based on leakage or the like, and the cutoff valve is closed during the continuous flow to When the fuel injection amount of the fuel injection nozzle is the maximum or a large injection amount close to it, the cut-off valve malfunctions and the engine output is limited. There is no problem of stopping, and a large amount of fuel spilled due to leakage from the joint portion of the fuel passage connecting the fuel injection valve and the accumulator of each cylinder, damage to the fuel passage, etc. By clearly detecting the difference from the above and closing the cut-off valve, it is possible to reliably prevent fuel leakage, spillage, etc., and effectively prevent fuel loss, contamination around the engine, or fire. There are benefits that can be prevented.
[0036]
In the above invention, the damper device is formed in a valve housing having a piston member coaxially fixed to the cut-off valve and a fuel passage opened and closed by the cut-off valve. Since the fuel in the fuel passage is supplied and the damper chamber slidably accommodates the piston member, the structure of the safety device can be made small and compact. There is an advantage that the mountability is excellent.
Furthermore, a one-way valve that allows only the flow of fuel from the fuel passage side to the damper chamber side is provided between the fuel passage formed in the valve housing and the damper chamber. There are advantages that the working fluid is used as fuel itself to simplify the structure and that the cut-off valve is returned to the original position or the rest position after fuel injection during normal operation of the engine.
Furthermore, in the present invention, the piston member is a hollow cylindrical member surrounded on the outer periphery of the cutoff valve, and the damper chamber is an annular chamber that accommodates the piston member with a minute gap. As a result, the hollow cylindrical damper device is arranged on the outer periphery of the cutoff valve, and therefore, there is an advantage that the outer dimensions of the safety device can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire accumulator fuel injection device including a safety device according to the present invention.
FIG. 2 is an enlarged cross-sectional view showing a detailed structure of the safety device in FIG.
FIG. 3 is a cross-sectional view showing the structure of a safety device in a conventional accumulator fuel injection device.
FIG. 4 is a cross-sectional view showing another structure of a safety device in a conventional accumulator fuel injection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Engine, 12 ... Fuel injection nozzle, 14 ... Control unit or control means, 24 ... Fuel injection pipe, 26 ... Safety device, 28 ... Accumulation chamber or common rail, 30 ... Fuel supply pump or plunger device, 34 ... Fuel tank, 36 ... feed pump, 38 ... valve housing, 40 ... large diameter hole, 42 ... small diameter hole, 50 ... cutoff valve, 64 ... damper device, 64a ... piston member, 64c ... ring piston, 64d ... damper chamber, 70 ... one way valve.

Claims (2)

A pressure accumulation chamber for storing high-pressure fuel;
A fuel passage for supplying high-pressure fuel in the accumulator chamber to a fuel injection nozzle provided in each cylinder of the engine;
A cut-off valve that is interposed in the fuel passage and normally opens the fuel passage;
A damper device coupled to the cut-off valve,
The damper device is
A piston member that is coaxial with the cutoff valve and is formed in a hollow cylindrical shape so as to be surrounded by the outer periphery of the cutoff valve;
Formed on the outer periphery of the fuel passage in the valve housing that is opened and closed by the cut-off valve, the fuel in the fuel passage is supplied to the inside thereof, and the piston member is slidable with a small gap. Consists of an annular damper chamber for housing,
The damper device is either intermittent stream fuel flow through the cut-off valve is supplied to the fuel injection nozzle, to determine a continuous stream based on leakage or the like, the cut-off when the continuous flow characterized in that it operates to shut off the fuel passage by closing the cutoff valve by flowing out fuel in the damper chamber from the minute clearance by the pressure difference generated between the upstream side and the downstream side of the valve A safety device for an accumulator fuel injection device.   2. A one-way valve that allows only a flow of fuel from the fuel passage side to the damper chamber side is provided between the fuel passage formed in the valve housing and the damper chamber. The safety device of the accumulator fuel injection device described.

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