JPH06159180A - Distribution type fuel injection pump - Google Patents

Abstract

PURPOSE:To provide a distribution type fuel injection pump where the wear and seizure of a distribution rotor can be prevented, and the spill performance is excellent. CONSTITUTION:As a diesel engine is started, the fuel is fed by means of a wane feed pump 19 from a fuel tank 17 to a feed gallery 51 through a non- return valve 23. This fuel is introduced into a plunger chamber 41 through the suction stroke of a plunger 39 in a distribution rotor 37, and successively, into a distribution passage 52 provided in a distribution head 47 through a distribution passage 52 of the distribution rotor 37 through the distribution stroke of the plunger 39, and injected from the nozzle. On the other hand, when an infection quantity control valve 59 is opened, and communication is made with a spill passage 57, the high pressure fuel in the plunger chamber 41 is overflowed and introduced into a cam chamber 27, and the pressure is reduced to provide the low pressure fuel. This low pressure fuel is then re-introduced into the vane feed pump 19 through a fuel recycling passage 63.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed fuel injection pump.

[0002]

2. Description of the Related Art Conventionally, as a distribution type fuel injection pump,
For example, as shown in JP-A-3-50374,
An overflow control type inner cam type distribution type fuel injection pump has been known (see FIG. 3). According to this distributed fuel injection pump, the high pressure fuel supplied from the fuel tank 101 to the feed gallery 103 via the feed pump 102 is reciprocated by the plunger 104 following the cam ridges in the inner cam ring 105. Distribution rotor 10
7, the fuel is sucked into the plunger chamber 111 from the suction passage 109, and then compressed, and the fuel is pressure-fed and distributed from the distribution passage 113 to each cylinder. Then, the solenoid valve 115 communicates and cuts off the spill passage 117 and the feed gallery 103 during the distribution stroke to control the overflow amount of the fuel and control the injection amount.

In this overflow metering type, the plunger chamber 111 must be constantly filled with fuel in order to obtain a predetermined injection characteristic. Here, the fuel can be roughly classified into the injected fuel distributed from the nozzles to the respective cylinders via the delivery valve 121 and the fuel other than the injection that overflows from the spill port 119 and the spill passage 117. Of these, fuel other than injection must be effectively reused from an economical point of view. Therefore, in the above-mentioned distributed fuel injection pump, the spill passage 117 is provided in the feed gallery 10.
3 to communicate the fuel other than the injection with the plunger chamber 111 again.
It has a structure that can be reused by inhaling it.

[0004]

However, according to the above distribution type fuel injection pump, the fuel that has passed through the spill passage 117 flows into the feed gallery 103 as an overflow of high pressure (up to 80 MPa) and the feed pump 1
Backflow to 02. Then, the load due to the high-pressure fuel flowing back into the feed pump 102 mounted at the tip of the distribution rotor 107 acts as an unbalanced load on the tip of the distribution rotor 107,
An excessive load will be applied locally.

Similarly, the load due to the high-pressure fuel flowing into the feed gallery 103 applies an excessive load to the distribution rotor 107 through the suction passage 109 communicating with the feed gallery 103. As a result, cylinder 1
23 and the distribution rotor 107 clearance (usually several μ
m) is locally reduced, and the cylinder 123 and the distribution rotor 1
There is a possibility that the frictional force with 07 increases and wear or seizure occurs. Further, the fuel other than the injection from the spill passage 117 overflows into the feed gallery 103 maintained at the feed pump discharge pressure of several MPa, so that the pressure difference between the fuel in the spill passage 117 and the fuel in the feed gallery 103 is increased. There was a problem that it decreased and deteriorated the spill performance.

Further, at the same time as solving the above problems, it has been desired to effectively reuse the fuel overflowed from the spill passage 117 other than the injection without using complicated piping. Therefore, in order to solve the above problems, the first invention,
An object of the present invention is to provide a distribution type fuel injection pump that prevents wear and seizure of a distribution rotor and does not deteriorate spill performance. In addition to the object of the first invention, the second invention aims to provide a distributed fuel injection pump that effectively reuses fuel other than the overflowed injection.

[0007]

In order to solve the above problems, in the distribution type fuel injection pump of the first invention, the feed pump sucks the low-pressure fuel in the fuel tank from the upstream side, increases the pressure, and discharges it to the downstream side. The plunger reciprocates following the cam surface provided with the cam ridges, so that the plunger is sucked and compressed into the plunger chamber and pressure-distributed from the distribution rotor to each cylinder of the internal combustion engine. In the distributed fuel injection pump in which the spill passage is opened from the spill passage, the spill passage communicates with an upstream side of the feed pump.

The distribution type fuel injection pump of the second aspect of the invention is different from the distribution type fuel injection pump of the first aspect of the invention in that the feed passage is provided in a fuel passage that connects the suction port of the feed pump and the fuel tank. A check valve for preventing return of fuel to the fuel tank is provided near the suction port of the pump, and the spill passage has a suction port of the feed pump more than a position where the check valve is installed in the fuel passage. The point is that they are in communication with the side.

[0009]

In the distribution type fuel injection pump of the first invention having the above structure, first, the feed pump sucks the low-pressure fuel in the fuel tank provided outside from the suction port on the upstream side, increases the pressure, and discharges it from the discharge port. To do. Next, when the plunger reciprocates following the cam surface provided with the cam peak, this high-pressure fuel is sucked into the plunger chamber and further compressed to a high pressure (up to 80 MPa), and is pressure-fed and distributed from the distribution rotor to each cylinder. To be done. After that, the high-pressure fuel other than the injection in the plunger chamber overflows from the spill passage and is transferred to the upstream side of the feed pump, that is, the position where the low-pressure fuel exists. Therefore, the high-pressure fuel overflowing from the spill passage does not pressurize the distribution rotor in a direction orthogonal to its rotation axis, and is reduced in pressure by coming into contact with the low-pressure fuel on the upstream side of the pump. .

On the other hand, in the distributed fuel injection pump of the second invention, in addition to the operation of the first invention, the fuel other than the injection overflowed from the spill passage does not return to the fuel tank and is continuously sucked into the intake port of the feed pump. Is inhaled from and is supplied to the plunger chamber.

[0011]

EXAMPLES The present invention will be described below with reference to an overflow adjustment type inner cam type distribution type fuel injection pump (hereinafter referred to as "injection pump").
An embodiment embodied as 10 will be described with reference to the drawings. As shown in FIG. 1, the present embodiment mainly comprises a drive shaft 11, a vane feed pump 19, an inner cam ring 29, and a distribution rotor 37.

As shown in FIG. 1, the drive shaft 11
Is inserted into the pump housing 13 and is rotatably supported by the bearing 15 in synchronization with the rotation of a diesel engine (not shown) as an internal combustion engine. Distribution rotor 3
A vane feed pump 19 (indicated by 90 ° development in FIG. 1) is provided at a substantially tip portion of 7. The vane feed pump 19 has a suction port 19a and a discharge port 19c. The fuel passage 21 extending from the fuel tank 17 is
A fork 21a is formed from the middle in the pump 10 and communicates with the suction port 19a. A check valve 23 for preventing the fuel from returning to the fuel tank 17 is installed in the fuel passage 21 on the fuel tank 17 side from the fork 21a in the pump 10. The check valve 23 opens when the pressure on the suction port side of the vane feed pump is lower than the set pressure, and closes when the pressure is higher than the set pressure. Further, the discharge port 19c of the vane feed pump 19 communicates with a feed gallery 51 described later via the fuel supply passage 25. And the vane feed pump 19
When the rotor 19e rotates in synchronization with the rotation of the drive shaft 11, the low-pressure fuel in the fuel tank 17 provided outside the injection pump 10 is sucked up from the suction port 19a and discharged as pressurized fuel from the discharge port 19c. It is supplied to the feed gallery 51.

Further, as shown in FIG. 1, the tip of the drive shaft 11 reaches a cam chamber 27 provided at the base end of the pump housing 13, and the left end of a distribution rotor 37, which will be described later, is located in the cam chamber 27. It has a structure capable of rotating integrally with the distribution rotor 37 by engaging with the parts. Therefore, the distribution rotor 37 also rotates in synchronization with the rotation of the diesel engine.

An inner cam ring 29 is provided in the cam chamber 27.
Is installed so that its outer surface slidably contacts the inner surface of the cam chamber 27. FIG. 2 shows a cross section taken along the line AA of FIG. In FIG. 2, a pair of cylindrical holes 37a orthogonal to each other are formed in the distribution rotor 37, and a pair of plungers 39 are slidably housed in the cylindrical holes 37a in an oil-tight state. A plunger chamber 41 is formed by the. A shoe 43 is arranged at the outer end of each plunger 39, and a roller 45 is attached to the shoe 43.
Is rotatably held. The outer surface of the roller 45 is in contact with a cam surface 29a provided on the inner circumference of the inner cam ring 29 and having a plurality of cam lobes. Then, based on the rotation of the distribution rotor 37, the roller 45 causes the inner cam ring 2 to move.
9 slides on the cam surface 29a on the inner circumference of the roller 45.
Moves reciprocally in the radial direction of the inner cam ring 29 along the cam surface 29 a, and this reciprocating motion is transmitted to the plunger 39 via the shoe 43. In this reciprocal movement, the stroke in which the plunger 39 moves outward in the radial direction of the distribution rotor 37 is the suction stroke, and the stroke in which the plunger 39 moves inward in the radial direction is the pumping and distribution stroke.

Further, in FIG. 1, the right end portion of the distribution rotor 37 is rotatably supported in a cylinder 49 installed in the distribution head 47 at a position facing the drive shaft 11. The clearance between the cylinder 49 and the distribution rotor 37 is adjusted to 4 to 5 μm. on the other hand,
The distribution head 47 is provided with an annular feed gallery 51 so as to surround the cylinder 49. The cylinder 49 has a plurality of intake passages 49a communicating with the feed gallery 51, a plurality of distribution passages 49b for supplying fuel to each cylinder of the engine, and a plurality of spill passages 49c.
Are formed. Each distribution passage 49c has a distribution head 47.
Is connected to each nozzle 55 via a delivery valve 53 for supplying fuel to each cylinder of the engine via a distribution passage 52 provided in the. On the other hand, at the right end of the distribution rotor 37, a suction port 37b communicating with the plunger chamber 41,
A distribution port 37c and a spill port 37d are formed, and each suction passage 49a and each distribution passage 49b provided in the cylinder 49 based on the rotation of the distribution rotor 37.
And the spill passage 49c.

A spill passage 49c provided in the cylinder 49
Communicates with a spill passage 57 provided in the distribution head 47. The spill passage 57 is provided with an injection amount control valve 59 and a differential pressure valve 61 on the way, and communicates with the cam chamber 27 via these. Further, the cam chamber 27 is provided with a fuel reuse passage 63 communicating with the upstream side of the vane feed pump 19. The injection amount control valve 59 is controlled by the ECU 69 on the basis of input signals from an accelerator sensor 65 and an engine speed sensor 67 provided outside the injection pump 10, and connects and disconnects the spill passage 57 during the distribution stroke. The pressurized fuel is made to overflow and the injection amount is controlled. The differential pressure valve 61 is a check valve for transferring fuel only from the injection amount control valve 59 toward the cam chamber 27, and is installed to obtain a constant injection characteristic. Further, the cam chamber 27 has a volume sufficiently larger than that of the spill passage 57. In addition, the fuel reuse passage 63 is connected between the check valve 23 and the fork 21 a provided in the fuel passage 21.

The discharge side and the suction side of the vane feed pump 19 are connected via a pressure adjusting valve 71 so that the discharge pressure can be adjusted. The operation of the injection pump 10 of the present embodiment configured as above will be described below.

With the rotation of the diesel engine, the drive shaft 11 rotates and the vane feed pump 19 drives, so that low-pressure fuel is introduced from the fuel tank 17 into the fuel passage 21 and passes through the check valve 23 to reach the vane feed pump. It is sucked into the suction port 19a of the valve 19, is pressurized to a high pressure, and is discharged from the discharge port 19c. The discharged high-pressure fuel is introduced into the fuel supply passage 25 and supplied to the feed gallery 51. The fuel in the feed gallery 51 is transferred to the cylinder 4 by the suction stroke of the plunger 39 in the distribution rotor 37.
9 is introduced into the plunger chamber 41 via the suction passage 49a provided in the No. 9 and the suction port 37b provided in the distribution rotor 37. Subsequently, the high pressure fuel in the plunger chamber 41 is further increased in pressure by the distribution stroke of the plunger 39, and reaches the distribution head 47 via the distribution port 37c provided in the distribution rotor 37 and the distribution passage 52 provided in the cylinder 49. It is introduced into the distribution passage 52 provided and is ejected from the nozzle via the delivery valve 53.

On the other hand, when the ECU 69 opens the injection amount control valve 59 to connect the spill passage 57, the plunger chamber 4
The high-pressure fuel (up to 80 MPa) in 1 overflows, which stops the fuel injection from the nozzle 55. The overflowed high-pressure fuel is introduced into the cam chamber 27 via the differential pressure valve 61.
At this time, due to the reason that the volume of the cam chamber 27 is sufficiently larger than that of the spill passage 57 and that the inside of the cam chamber 27 is filled with the low pressure fuel, when the high pressure fuel reaches the cam chamber 27, the expansion effect, The pressure decreases due to contact with the low-pressure fuel and becomes low-pressure fuel. This low-pressure fuel is then introduced into the fuel passage 21 via the fuel reuse passage 63.
At this time, the fuel reuse passage 63 is communicated between the check valve 23 and the forked passage 21a in the fuel passage 21, and therefore is not returned to the fuel tank 17 provided outside the injection pump 10, It is immediately sucked into the suction port 19a of the vane feed pump 19.

The embodiment described in detail above has the following effects. (1) By the high-pressure fuel overflowing from the spill passage 49c reaching the cam chamber 27 having a larger capacity than the spill passage 57 and expanding, and coming into contact with the low-pressure fuel filled in the cam chamber 27, The pressure is lowered. That is, since the pressure difference between the fuel in the cam chamber 27 and the fuel in the spill passage 49c can be maintained sufficiently large, the spill performance does not deteriorate. (2) Since the high-pressure fuel overflowing from the spill passage 49c does not apply pressure in the direction perpendicular to the axis of the distribution rotor 37 or the drive shaft 11, it affects the clearance between the cylinder 49 and the distribution rotor 37. There is no. As a result, there is no risk of wear and seizure of the distribution rotor 37. (3) The high pressure fuel overflowing from the spill passage 49c causes the cam chamber 2
When it reaches 7, the inner cam ring 29
However, since the plunger 39 slides on the cam surface 29a provided inside the inner cam ring 29 and reciprocates in the radial direction, the reciprocation of the plunger 39 is not affected. That is, it does not affect the performance of the injection pump 10. (4) The fuel other than the fuel injected through the spill passage 49c is sucked into the vane feed pump 19 and used again without returning to the fuel tank 17. Therefore, the fuel tank 1
Compared with the case of returning to 7, the piping is easy and the risk of fuel leakage is reduced.

Although the present embodiment has been described above, it is needless to say that the present invention is not limited to this embodiment and can be implemented in various modes without departing from the spirit of the present invention. . For example, although the inner cam type distribution type fuel injection pump is described as an example in the present embodiment, the present invention may be applied to a face cam type distribution type fuel injection pump. Further, in the present embodiment, the high pressure fuel overflowing from the spill passage 49c is once introduced into the cam chamber 27 to reduce the pressure, but without passing through the cam chamber 27, the check valve 23 and the two-pronged valve are provided in the fuel passage 21. It may be introduced between the passage 21a (that is, on the upstream side of the vane feed pump 19). In this case, the spill performance is not deteriorated because the pressure is reduced by contact with the low pressure fuel existing in the fuel passage 21.

[0022]

As described in detail above, according to the distribution type fuel injection pump of the first invention, it is possible to prevent wear and seizure of the distribution rotor, and the deterioration of the spill performance is prevented. On the other hand, in addition to the effect of the first invention, the distributed fuel injection pump of the second invention can effectively reuse the fuel other than the injection overflowed from the spill passage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an overflow adjustment type inner cam type distribution type fuel injection pump of the present embodiment.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view of a conventional overflow control type inner cam type distribution type fuel injection pump.

[Explanation of symbols]

10 ... Injection pump, 11 ...
Drive shaft, 13 ... Pump housing,
17 ... Fuel tank, 19 ... Vane feed pump, 23 ... Check valve, 25 ... Fuel supply passage, 27 ... Cam chamber, 29
... Inner cam ring, 29a ... Cam surface, 37 ... Distribution rotor, 39
... Plunger, 41 ... Plunger room,
47 ... Dispensing head, 49 ... Cylinder,
49c ... Spill passage, 51.
..Feed gallery, 57 ... Spill passage, 59 ... Injection amount control valve, 63
... Fuel reuse passage,

Claims (2)

[Claims] 1. A feed pump sucks low-pressure fuel in a fuel tank from an upstream side, increases its pressure and discharges it to a downstream side, and a plunger reciprocates following a cam surface provided with a cam mountain, A distribution type fuel injection pump in which high pressure fuel in the plunger chamber is released from a spill passage after suction / compression in the plunger chamber and pressure distribution from the distribution rotor to each cylinder of the internal combustion engine, wherein the spill passage is upstream of the feed pump. Distributor type fuel injection pump characterized in that it is communicated to the side. 2. A check valve for preventing fuel from returning to the fuel tank is provided near a suction port of the feed pump in a fuel passage that connects the suction port of the feed pump and the fuel tank. The distributed fuel injection pump according to claim 1, wherein the spill passage communicates with a suction port side of the feed pump with respect to a position where the check valve is installed in the fuel passage.