JP2506746Y2 - Pilot injection device for fuel injection pump - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to a pilot injection device for a fuel injection pump, which is provided in communication with a pressurizing chamber of the fuel injection pump and performs pilot injection prior to main injection of fuel.

[Prior art]

A pilot injection device for a fuel injection pump that performs pilot injection prior to main injection of fuel and performs main injection when a small amount of fuel is ignited in order to reduce combustion noise and improve ignitability of diesel engines has been known. Has been. As such a technique, for example, an apparatus described in JP-A-61-129456 is proposed. In this pilot injection device, the fuel in the pressure chamber pressurized by the plunger of the fuel injection pump is introduced into the expansion chamber by moving the pressure relief member biased by the spring at a predetermined pressure or higher to introduce pilot injection. While performing, the bypass hole, which is intermittently shielded by the plunger, communicates with the expansion chamber by the bypass, so that the expansion chamber is decompressed in a non-injection magnetic field. By the way, the pilot injection amount of the pilot injection device is determined by the valve opening pressure of the accumulation rate piston as a pressure relief member. That is, when the valve opening pressure falls below the predetermined pressure, the pilot injection end timing is advanced and the pilot injection amount is reduced. This valve opening pressure decreases when the residual pressure of the fuel in the accumulation rate chamber as the expansion chamber when the accumulation rate piston is closed is high. Since the fuel viscosity decreases when the fuel temperature becomes relatively high, the fuel in the accumulation chamber easily flows out through the gap between the sliding portion between the cylinder and the accumulation piston. By the way, the fuel viscosity increases as the fuel temperature decreases. Therefore, when the fuel temperature becomes relatively low, less fuel flows through the gap of the sliding portion. As a result, the residual pressure of the fuel in the accumulation rate chamber increases, the valve opening pressure decreases, and the pilot injection amount decreases. Therefore, as in the above-described conventional technique, it is also devised to prevent the fuel in the accumulation rate chamber from flowing out through a bypass and reduce the pressure during non-fuel injection to prevent fluctuations in the pilot injection amount.

[Problems to be solved by the device]

However, in the above-mentioned conventional technique, the fuel in the accumulation rate chamber is discharged at the time of non-fuel injection by the bypass opened and closed by the constantly rotating plunger. For this reason, there is a possibility that the timing at which the fuel in the accumulation chamber flows out may vary greatly due to manufacturing errors and the like, and since both the fuel injection pump and the pilot injection device need to be machined, the structure becomes complicated. there were. An object of the present invention is to improve only the structure of the pilot injection device to reduce the residual pressure in the accumulation rate chamber and prevent the fluctuation of the pilot injection amount.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a fuel injection in which pilot injection is performed by an accumulation rate piston slidably provided in a cylinder formed between a pressure chamber and a low pressure fuel chamber of a fuel injection pump. In a pilot injection device of a pump, the accumulation rate piston is provided with a first pressure reducing fuel passage communicating with the low pressure fuel chamber, and the cylinder is configured such that the accumulation rate piston communicates between the pressurizing chamber and the accumulation rate chamber. A second pressure-reducing fuel passage communicating the first pressure-reducing fuel passage with the accumulation chamber is provided at a position where the first pressure-reducing fuel passage is cut off. The gist of the present invention is to provide a one-way valve that allows only the flow of fuel from the reduced pressure fuel passage 1 toward the low pressure fuel chamber. .

[Action]

According to the pilot injection device of the fuel injection pump of the present invention configured as described above, when the pressure of the pressurizing chamber rises, the accumulating piston moves to connect the pressurizing chamber and the accumulating chamber. Perform pilot injection. Then, when the pressure in the pressurizing chamber decreases and the accumulation rate piston cuts off the communication between the pressurizing chamber and the accumulation rate chamber, the second depressurized fuel passage provided in the cylinder and the first depressurizing fuel provided in the accumulation rate piston are provided. Since the pressure-reduced fuel passage communicates with each other, the accumulation rate chamber and the low-pressure fuel chamber communicate with each other, and the fuel in the accumulation rate chamber flows out to the low-pressure fuel chamber. Therefore, the pressure in the accumulation rate chamber is reduced to a pressure corresponding to the pressure in the low pressure fuel chamber. Further, since the low-pressure fuel chamber and the first depressurized fuel passage are shut off by the check valve, even if the pressure in the low-pressure fuel chamber fluctuates, the influence thereof does not reach the accumulation rate chamber.

【Example】

First Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 and 2 show the pilot injection device of the first embodiment, and FIG. 3 shows a fuel injection pump to which this pilot injection device is attached. First, the configuration of the fuel injection pump to which the pilot injection device of the present embodiment is attached will be described with reference to FIG. In the drawing, reference numeral 1 denotes a well-known distribution type fuel injection pump, in which a cam plate 13 connected to a dry shaft 12 through a coupling in a pump housing 11, and a rotary and reciprocating motion integrally with the cam plate 13. A pump plunger 14 is provided. The pump plunger 14 is arranged in the pump housing 16 and pressurizes the fuel in the pressurizing chamber 17 flowing from the suction port 15. Pump plunger
The pressurized fuel is supplied to each distribution passage 14 at a predetermined timing.
A distribution port 14a that distributes the fuel to 18 and sends the fuel under pressure to each cylinder of the diesel engine through a delivery pipe 19 and a spill port 14b that overflows the pressurized fuel are provided. Next, 31 is a spill ring that opens and closes the spill port 14b, and adjusts the overflow timing of the fuel pressurized by the pump plunger 14 to control the fuel injection amount. This spill ring 31 is supported by a supporting lever 32, and a governor sleeve 34 that responds to the movement of the flyweight 33 and
It is actuated by a control lever 35 interlocked with the accelerator pedal and a tension lever 37 that moves via a governor spring 36, and is moved according to the vehicle speed and the depression amount of the accelerator pedal. Next, 38 is a feed pump that supplies fuel into the pump housing 11, and 39 is a timer that is operated according to the fuel pressure in the pump housing 11 and controls the fuel injection timing. Further, 20 is the pilot injection device of the present embodiment provided in communication with the pressurizing chamber 17, and this pilot injection device
20 is activated when the fuel pressure in the pressurizing chamber 17 is increased by the movement of the pump plunger 14 (pressurizing stroke) and fuel injection is performed, and the fuel pressure in the pressurizing chamber 17 is temporarily reduced to temporarily. Specifically, the fuel injection is stopped, the pilot injection is performed, and then the main injection is performed. The configuration of this pilot injection device 20 is shown in FIG.
This will be described in detail with reference to FIG. First, as shown in FIG. 1, the pilot injection device 20 communicates with the pressurizing chamber 17 of the fuel injection pump 1, and has a body 43 that incorporates a cylinder 42 into which the accumulation rate piston 41 is fitted. It is composed of a cap 45 screwed via 44 and a spacer 46 interposed between the body 43 and the cap 45. The body 43 is provided with a screw portion 47 provided on the outer periphery of the tip,
It is attached to the fuel injection pump 1. The cylinder 42 has a small hole 48,
An accumulation rate chamber 51, which communicates with the pressure chamber 17 of the fuel injection pump 1 via the communication passage 49 and is shielded from the pressure chamber 17 by the seat portion 50 formed at the tip of the accumulation piston 41, is provided. The fuel filled in the accumulation rate chamber 51 is the head taper surface 41a of the accumulation rate piston 41.
Exert pressure on. A back pressure chamber 52 is formed by the cap 45 and the spacer 46. Inside the back pressure chamber 52, a pressure pin 53 interlocking with the accumulation rate piston 41 is arranged, and a return spring 54 as a biasing member for biasing the pressure pin 53 toward the pressurizing chamber 17 is also provided. It is arranged. Further, inside the back pressure chamber 52, a pressure pin stopper 55 that restricts the movement amount of the pressure pin 53 is arranged. The pressure pin stopper 55 is the pressure pin 53.
Is adjusted by the shim 56 so that the movement amount of the is slightly smaller than the movement amount of the accumulation rate piston 41. In addition, the set load of the return spring 54 is
Set by 57. A screw 58 is screwed to the rear end of the cap 45 via a gasket 59. A return chamber 60 is formed between the rear end of the accumulation rate piston 41 and the spacer 46, and the return chamber 60 is provided with a gap 61 between the accumulation rate piston 41 and the spacer 46 and a back pressure chamber 52. , To the return passages 62 and 63.
The return passages 62 and 63 communicate with the inside of the pump housing 11 of the fuel injection pump 1 as a low-pressure fuel chamber via a passage (not shown). A check valve 66 is attached to the return passage 63 provided in the body 43 to allow only the flow from the return chamber 60 into the pump housing 11. A cutout portion 41b is provided at the rear end of the accumulation rate piston 41. The cutout portion 41b and the cylinder
A first depressurized fuel passage 64 is formed between the inner surface of 42 and the inner surface. The first depressurized fuel passage 64 is connected to the return chamber 60.
Is in communication with. Further, the cylinder 42 has a leak passage 65a communicating with the accumulation chamber 51 and the leak passage 6a.
A second depressurized fuel passage 65 formed from a leak passage 65b communicating with 5a is provided. And the leak passage 65b
Is open to the sliding surface of the accumulation rate piston 41 in the cylinder 42. The opening position of the leak passage 65b is set by the seat portion 50 of the accumulation rate piston 41 when the communication between the accumulation rate chamber 51 and the pressurization chamber 17 is blocked.
When the leak passage 65b communicates with the first depressurized fuel passage 64 and the accumulation rate piston 41 moves in the direction of the spacer 46 so that the accumulation rate chamber 51 and the pressurization chamber 17 communicate with each other, the leakage passageway 65b causes the accumulation rate piston 41 to move. It is set at a position where it is closed by the outer peripheral surface of and is blocked from the first depressurized fuel passage 64. Next, the operation of the pilot injection device 20 will be described. When the pump plunger 14 of the fuel injection pump 1 is driven rightward in FIG. 3 by the cam plate 13, the fuel in the pressurizing chamber 17 is pressurized and the distribution port 14 in the pump plunger 14 is pressurized.
It is pressure-fed to the fuel injection nozzle of the diesel engine through the distribution passage 18 via a. In this way, in the initial stage when the pressure feeding of the fuel is started, the initial fuel injection (pilot injection) is performed from the fuel injection nozzle, but the fuel pressure in the pressurizing chamber 17 depends on the return spring 54 of the pilot injection device 20. When the set pressure is exceeded, the accumulation rate piston 41 moves to the right in FIG. 1 and separates from the seat portion 50.
Then, since the accumulation chamber 51 communicates with the pressurizing chamber 17, the fuel pressure receiving area of the accumulation piston 41 increases from the end face to the head tapered face 41a.
The accumulation rate piston 41 rapidly moves to the right in FIG. 1 and stops when the pressure pin 53 contacts the pressure pin stopper 55. As described above, during the movement of the accumulation rate piston 41, the fuel pressure in the pressurizing chamber 17 once drops, so the pressure feeding of the fuel is temporarily stopped. Eventually, when the accumulation rate piston 41 comes into contact with the spacer 46 and stops, the fuel is pumped again by the movement of the pump plunger 14 of the fuel injection pump 1, and the main injection is performed. After that, when the spill port 14b is opened by the spill ring 31 by the movement of the pump plunger 14, the fuel in the pressurizing chamber 17 overflows into the pump housing 11 and the pressure in the pressurizing chamber 17 decreases, and the main injection is performed. Ends. At this time, the pressure in the pressurizing chamber 17 decreases, so that the accelerating force of the return spring 54 causes the accumulation rate piston 41 to return to the position where the seat portion 50 abuts. By the way, as described above, when the residual pressure in the accumulation rate chamber 51 varies due to the fuel viscosity and the like, the pilot injection amount also varies. Therefore, in this embodiment, the first depressurization fuel passage 64 and the second depressurization fuel passage 65 cause the accumulation rate to increase. The residual pressure in the chamber 51 is kept constant. The operation will be described below. First, the main injection described above ends and the pressure in the pressurizing chamber 17 decreases, and the urging force of the return spring 54 causes the accumulation rate piston 41 to return to the position where it abuts against the seat portion 50, and the accumulation rate chamber 51. When the communication between the pressure chamber 17 and the pressure chamber 17 is cut off, the second depressurized fuel passage 65 (leak passage 65
Since b) communicates with the first depressurized fuel passage 64, the residual fuel in the accumulation rate chamber 51 remains in the second depressurized fuel passage 65.
(Leak passages 65a, 65b), the first pressure reducing fuel passage 64, the return chamber 60, the gap 61 between the accumulation rate piston 41 and the spacer 46, the back pressure chamber 52, the return passages 62, 63, and the check valve 66. Positively flows into the pump housing 11 of the fuel injection pump 1. Therefore, the accumulation rate room
The residual pressure in 51 is reduced and becomes almost constant regardless of the fuel viscosity. Further, at this time, since the check valve 66 is provided in the return passage 63, the residual pressure in the accumulation rate chamber 51 is reduced by the check valve 66.
Is determined by the valve opening pressure, and is less affected by the pressure in the pump housing 11 that fluctuates depending on the engine speed, engine load, etc., and the residual pressure in the accumulation chamber 51 can be made constant. Further, the fuel pressure in the pressurizing chamber 17 is controlled by the pilot injection device 20.
When the accumulation rate piston 41 moves to the right in FIG. 1 by exceeding the pressure set by the return spring 54 of
The second depressurized fuel passage 65 (leakage passage 65b) is closed by the outer peripheral surface of the accumulation rate piston 41 and cut off from the first depressurized fuel passage 64, so that the pressure in the pressurizing chamber 17 is moved by the movement of the pump plunger 14. Rises and the main injection can be performed. The pressure in the pressurizing chamber 17 decreases when the main injection ends,
When the accumulation rate piston 41 returns to the position where it contacts the seat portion 50, the above-mentioned second depressurized fuel passage 65 is formed.
Since the (leak passage 65b) communicates with the first depressurized fuel passage 64, the residual fuel in the accumulation chamber 51 positively flows out into the pump housing 11 of the fuel injection pump 1 and the inside of the accumulation chamber 51. Residual pressure becomes almost constant. As described above, in the present embodiment, the residual fuel in the accumulation rate chamber 51 can be positively discharged into the pump housing 11 of the fuel injection pump 1 to make the residual pressure in the accumulation rate chamber 51 constant. In addition to being able to achieve the operation, the second pressure reducing fuel passage 65 provided in the cylinder 41 of the pilot injection device 20 and the first pressure reducing fuel passage 64 formed by the cutout portion 41b of the accumulation rate piston 41 can be used. Since it is simply combined with, the structure is simple and it is possible to prevent the performance from greatly varying due to manufacturing errors or the like. (Second Embodiment) FIG. 4 shows a second embodiment of the present invention. In the first embodiment, the first depressurized fuel passage 64 is formed by the cutout portion 41b of the accumulation rate piston 41, so that the second
When the accumulation rate piston 41 rotates due to the reciprocating movement, the communication may be interrupted because the width of the communication portion with the reduced pressure fuel passage 65 (leak passage 65b) is narrow. Therefore, it is necessary to provide the accumulation rate piston 41 with a detent. The second embodiment does not require this detent. As shown in FIG. 4, in the second embodiment, the rear end portion of the accumulation rate piston 41 is reduced in diameter over the entire circumference to reduce the diameter of the small diameter portion.
By using 41c, a ring-shaped first depressurized fuel passage 64 is formed between the inner peripheral surface of the cylinder 42 and the cylinder 41. This prevents the communication with the leak passage 65b from being blocked even if the accumulation rate piston 41 rotates. (Third Embodiment) FIG. 5 shows a third embodiment of the present invention. Fifth
In the third embodiment shown in the drawing, the opening portion of the inner peripheral surface of the cylinder 42 of the leak passage 65b forming the second depressurized fuel passage 65 is formed over the entire inner peripheral surface of the cylinder 42. The first pressure reducing fuel passage 64 provided in the accumulation rate piston 41 is formed of ports 64a, 64b, 64c bored in the accumulation rate piston 41.
Is communicated with the opening of the leak passage 65b at a position where the accumulation piston 41 abuts the seat portion 50, and is blocked by the inner peripheral surface of the cylinder 42 at a position where the accumulation piston 41 abuts the spacer 46. Has been drilled in position. Also according to this embodiment, the accumulation rate piston 41
Rotation of the second depressurized fuel passage 65 (leak passage 65
It is possible to prevent the communication between b) and the first depressurized fuel passage 64 from being blocked. Further, since the first pressure reducing fuel passage 64 is formed in the accumulation rate piston 41, the area of the sliding surface between the accumulation rate piston 41 and the cylinder 42 can be increased, so that the inclination of the accumulation rate piston 41 can be prevented. At the same time, the surface pressure of the sliding surface is reduced, and the durability is also improved. Further, also in the second and third embodiments described above, the residual fuel in the accumulation rate chamber 51 is positively flown into the pump housing 11 of the fuel injection pump 1 to positively accumulate it.
The structure that enables the residual pressure in the cylinder 51 to be constant and achieves its operation is the cylinder of the pilot injection device 20.
Since the second depressurized fuel passage 65 provided in 41 and the first depressurized fuel passage 64 formed in the accumulation rate piston 41 are simply combined, the structure is simple and
It is possible to prevent the performance from being greatly varied due to manufacturing error or the like. Further, in the above-described embodiment, the low pressure chamber inside the pump housing 11 of the fuel injection pump 1 is used as the low pressure fuel chamber.
Alternatively, for example, a fuel tank or the like where the fuel pressure is relatively low and pressure fluctuation is small may be used. The embodiment of the present invention has been described above, but the present invention is not limited to this embodiment, and various embodiments are included within the scope of the claims of the utility model. is there.

[Effect of device]

As described above, according to the present invention, in the pilot injection device of the fuel injection pump that performs the pilot injection by the accumulation rate piston, the accumulation rate piston can slide with the first pressure reducing fuel passage provided in the accumulation rate piston. The second pressure reducing fuel passage provided in the cylinder accommodated in the cylinder reduces the residual pressure in the accumulation rate chamber when the accumulation rate piston cuts off the accumulation rate chamber from the pressure chamber of the fuel injection pump, and Since the stop valve prevents the pressure in the low-pressure fuel chamber from affecting the accumulation rate chamber, the residual pressure in the accumulation rate chamber can be set to a substantially predetermined pressure regardless of the fuel viscosity, etc. In addition to being able to prevent it, the structure is simple and it is possible to prevent the performance from being greatly varied due to manufacturing errors. It can be.

[Brief description of drawings]

1 to 3 are views showing a first embodiment of the present invention. FIG. 1 is a sectional view showing the overall construction of a pilot injection device, and FIG. 2 is a schematic view of the pilot injection device of FIG. 3 is an enlarged cross-sectional view of a portion of the fuel injection pump to which the pilot injection device is attached, FIG. 4 is an enlarged cross-sectional view of a main portion of the pilot injection device of the second embodiment, and FIG.
It is a principal part expanded sectional view of the pilot injection device of an Example. 1 ... Fuel injection pump 11 ... Pump housing (low pressure fuel chamber) 17 ... Pressurization chamber 20 ... Pilot injection device 41 ... Accumulation rate piston 42 ... Cylinder 51 ... Accumulation rate chamber 54 ... Return spring ( Urging member) 64: first depressurized fuel passage 65: second depressurized fuel passage

Claims (1)

(57) [Scope of utility model registration request] 1. A cylinder formed between a pressurizing chamber and a low-pressure fuel chamber of a fuel injection pump, an accumulating chamber provided in the cylinder in the vicinity of a communicating portion with the pressurizing chamber, and a cylinder sliding on the cylinder. The urging member, which is movably fitted and urges in the direction of the pressurizing chamber, blocks the communication between the pressurizing chamber and the accumulating chamber and increases the fuel pressure in the pressurizing chamber. A pilot injection device for a fuel injection pump, comprising: an accumulation rate piston that moves against an urging member and that communicates the pressurization chamber and the accumulation rate chamber with each other; A first depressurized fuel passage communicating with the cylinder is provided, and at the position where the accumulation rate piston blocks the communication between the pressurization chamber and the accumulation rate chamber in the cylinder. A second pressure reducing fuel passage is provided which communicates the first pressure reducing fuel passage with the accumulation chamber, and the first pressure reducing fuel passage is provided in the middle of the passage extending from the first pressure reducing fuel passage to the low pressure fuel chamber. A pilot injection device for a fuel injection pump, which is provided with a check valve that allows only the flow of fuel from the low pressure fuel chamber to the low pressure fuel chamber.