JP2003184698A - Fuel supply pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply pump capable of stopping force-feeding of fuel from a plunger chamber even when an engine rotates at high speed. <P>SOLUTION: This fuel supply pump comprises proportional control valves 16, 17 controlling the flow rate of fuel supplied from a feed pump 40 to a plunger chamber 28; an overflow valve 18 installed in the middle of a first return passage 68 communicating the proportional control valves 16, 17 with a fuel tank 47 and restraining pressure rising of fuel supplied to the proportional control valves 16, 17; and an orifice 19 installed in the middle of a second return passage 69 communicating the plunger chamber 28 with downstream of the overflow valve 18 and reducing the cross section area of fuel flow returning to the fuel tank side. A check valve 20 is installed to the second return passage 69 downstream of the orifice 19, so as to avoid fuel flow from the downstream of the orifice 19 to the orifice side. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply pump, and more particularly to a fuel supply pump suitable as a supply pump for a common rail type fuel injection device. FIG. 9 is a circuit diagram of a conventional common rail type fuel injection device. [0003] A fuel supply pump 211 used in this common rail type fuel injection device is a feed pump 240 for supplying fuel from a fuel tank 47 to a plunger chamber 228.
And the plunger chamber 228 from the feed pump 240
Control valve 216 for controlling the flow rate of fuel supplied to
A part of the fuel supplied from the feed pump 240 to the proportional control valve 216 is provided in the first return passage 268 connecting the proportional control valve 216 and the fuel tank 47 to the fuel tank 47, Overflow valve 21 for suppressing an increase in pressure of fuel supplied to control valve 216
8, plunger chamber 228 and overflow valve 21
A throttle 219 is provided in the middle of the second return passage 269 connecting the downstream side of the fuel tank 8 and the flow path of the fuel returning to the fuel tank 47 side. In this fuel supply pump, the flow rate of fuel supplied to plunger chamber 228 by feed pump 240 is controlled by proportional control valve 216. Proportional control valve 216
The fuel that has been prevented from flowing into the plunger chamber 228 is returned to the fuel tank 47 through the first return passage 268. However, even when the proportional control valve 216 is fully closed, the flow of fuel cannot be completely stopped, so that fuel leaks from upstream to downstream of the flow control valve 216. Therefore, even if the pumping of the fuel from the plunger chamber 228 is stopped in this state, the pumping cannot be stopped because the leaked fuel continues to be supplied to the plunger chamber 228. Therefore, the common rail controlled by the rotation speed and the accelerator opening degree There is a problem that the pressure in 48 becomes larger than the target value. To resolve this inconvenience,
The return passage 269 is provided. The fuel leaked from the proportional control valve 216 in the second return passage 269 flows into the first return passage 268 and returns to the fuel tank 47 through the first return passage 268. In this way, the leaked fuel is not supplied to the plunger chamber 228, so that the pumping of the fuel from the plunger chamber 228 can be stopped. The throttle 219 provided in the second return passage 269 determines the flow rate of the fuel returned to the fuel tank 47 via the second return passage 269. [0006] The feed pump 240
Is driven by an engine (not shown), the fuel discharge amount per unit time of the feed pump 240 is proportional to the engine speed. Therefore, when the engine is running at high speed, the supply of fuel by the feed pump 240 becomes excessive, and the amount of fuel returned to the fuel tank 47 via the first return passage 268 increases. At this time,
Since the passage cross-sectional area of the first return passage is not sufficiently large with respect to the flow rate of the fuel returned to the fuel tank 47,
The pressure in the return passage 268 may increase and become higher than the pressure in the second return passage 269. As a result, the fuel flows backward from the first return passage 268 to the second return passage 269, and the fuel to be returned to the fuel tank 47 is supplied to the plunger chamber 228. In this state, the pumping of the fuel from the plunger chamber 228 cannot be stopped. The present invention has been made in view of such circumstances, and an object thereof is to provide a fuel supply pump capable of stopping the fuel supply from the plunger chamber even when the engine is running at a high speed. It is. According to a first aspect of the present invention, there is provided a fuel supply pump for supplying fuel from a fuel tank to a plunger chamber.
A flow control means for controlling a flow rate of the fuel supplied from the feed pump to the plunger chamber; and a flow control means provided in a first return passage connecting the flow control means and the fuel tank. An overflow valve for returning a part of the fuel supplied to the control means to the fuel tank and suppressing a rise in the pressure of the fuel supplied to the flow rate control means; and an overflow valve connecting the plunger chamber and the downstream of the overflow valve. And a throttle that is provided in the middle of the second return passage and reduces a cross-sectional area of the flow of the fuel returning to the fuel tank side, wherein the throttle is provided in the second return passage downstream of the throttle. And a check valve for preventing a flow of fuel from a downstream side of the throttle to the throttle side. As described above, since the check valve is provided in the second return passage, even if the engine rotates at a high speed and the pressure in the first return passage increases, the second return passage is moved from the first return passage to the second return passage. Backflow of fuel to the return passage is prevented by the check valve. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a fuel supply pump according to an embodiment of the present invention. FIG. 1 is a conceptual view of a cross section taken along line II in FIG. 2, FIG. 2 is a front view of the fuel supply pump, and FIG. FIG. 4 is a left side view of the fuel supply pump shown in FIG. 1, FIG. 5 is a right side view of the fuel supply pump, FIG. 6 is a sectional view taken along line VI-VI of FIG. 2, and FIG. FIG. 8 is an enlarged sectional view of a part of the fuel supply pump, and FIG. 8 is a circuit diagram of a common rail type fuel injection device including the fuel supply pump. The fuel supply pump according to this embodiment is used as a supply pump of a common rail type fuel injection device, and as shown in FIG. 8, sucks fuel from a fuel tank 47, pressurizes the fuel, and connects the common rail 48 to an injector 49. Supply high pressure fuel to The fuel supply pump comprises a high-pressure pump 5 and a feed pump 40. The high-pressure pump 5 includes a housing 6, a shaft 7, a cam 8, a plunger 9, a tappet 10, first and second spring receivers 11, 12, a spring 13, an IO valve 14, a valve holder 15, a first and a first. 2 are provided with two proportional control valves (flow control means) 16 and 17, an overflow valve 18, an orifice (throttle) 19, and a check valve 20. The housing 6 has a housing body 61, a front housing 62, a rear housing 63, and a plunger barrel 64. The housing body 61 is formed with four holes 61a extending in the height direction, and these holes 61a are arranged in parallel along the axial direction of the shaft 7. A ring-shaped projection 61b is formed on the inner peripheral surface of the hole 61a. In the lower part of the housing main body 61, a cam accommodating chamber 61c communicating with the hole 61a is formed. The front housing 62 closes an opening on the front surface of the housing main body 61. Rear housing 6
Reference numeral 3 denotes an opening on the rear surface of the housing body 61. The plunger barrel 64 is substantially cylindrical, and has a large diameter portion 64a, a small diameter portion 64b, a flange portion 64c,
It has a valve accommodation hole 64d, a plunger accommodation hole 64e, a passage portion 64f, and a passage portion 64g, and is inserted into each of the four holes 61a. The large diameter portion 64a is arranged above the convex portion 61b, and the small diameter portion 64b connected to the lower end of the large diameter portion 64a is arranged below the convex portion 61b. The flange portion 64c is connected to the upper end of the large diameter portion 64a. The flange portion 64c is fixed to the upper end surface of the housing main body 61 by bolts 31 and nuts 32. The valve housing hole 64d is formed in an upper part of the plunger barrel 64. The plunger housing hole 64e is formed at a lower portion of the plunger barrel 64, has a smaller diameter than the valve housing hole 64d, and communicates with the valve housing hole 64d. Passage 64f
Is formed in the large-diameter portion 64a, and a second supply passage 67 described later is formed.
Part of The passage portion 64g is formed in the large diameter portion 64a. A passage portion 64g of the plunger barrel 64 disposed on the front side of the housing main body 61 forms a part of a second return passage 69 described later. As shown in FIG. 1, the housing 6 is formed with first and second supply passages 66 and 67 and first and second return passages 68 and 69, respectively. The first supply passage 66 includes a passage portion 66a and a passage portion 66b. The passage portion 66a has a valve insertion portion 66c. The valve insertion portion 66c communicates with a passage portion 67a described later. The passage portion 66b is a valve insertion portion 66
d. The valve insertion portion 66d is provided with a passage portion 67 described later.
b. The first supply passage 66 has an inflow port 6
The fuel sent from the feed pump 40 flows through 1d. The second supply passage 67 includes a passage portion 67a, a passage portion 67b, a passage portion 67c, and passage portions 67d and 67d.
7e, 67f, 67g and the passage portion 64f of the plunger barrel 64 described above. One end of the passage portion 67 a is closed by the ball 23. One end of the passage portion 67 b is closed by the ball 24. Passage 67
c passes under the first return passage 68 and passes through the passage portion 6
7a and the passage portion 67b. Passage portions 67d, 67
e denotes first and second plunger chambers 28-
The passage portion 64f and the passage portion 67a of the plunger barrel 64 forming the components 1, 28-2 are connected. Passage portion 67f,
67g is a third and fourth plunger chamber 2 described later, respectively.
The passage portion 64f of the plunger barrel 64 constituting 8-3 and 28-4 is connected to the passage portion 67b. The fuel that has passed through the first and second proportional control valves 16 and 17 flows through the second supply passage 67. The first return passage 68 has a passage portion 68a.
And the overflow valve insertion portion 68b and the passage portion 68
c. Passage portion 68a communicates with first and second passage portions 66a, 66b. The overflow valve insertion portion 68b communicates with the passage portion 68a. One end of the passage portion 68c is inserted into the overflow valve insertion portion 68b.
The other end communicates with the outflow port 61e. The second return passage 69 includes the passage portion 64g, the passage portion 69a, the passage portion 69b, and the passage portion 6 described above.
9c. The passage portion 69a connects the passage portion 64g and the passage portion 69b. The passage portion 69b is the passage portion 69
The diameter is larger than c. One end of the passage portion 69b is the ball 2
5 closed. One end of the passage portion 69c communicates with the passage portion 69b, and the other end communicates with the overflow valve insertion portion 68b of the first return passage 68. The tip of the shaft 7 passes through the front housing 62. The shaft 7 is a bearing (not shown)
And is rotatably supported by the front housing 62 via the. The rear end of the shaft 7 is a rear housing 63
And is connected to the feed pump 40. The shaft 7 is connected to the rear housing 6 via a bearing (not shown).
3 rotatably supported. Four cams 8 are mounted on the shaft 7 so as to be located below the respective plunger accommodating holes 64e. The cam 8 is substantially triangular. The mounting angle of the cam 8 with respect to the shaft 7 increases by 90 degrees from the frontmost cam 8 toward the rear. The plunger 9 has a plurality of plunger receiving holes 64e.
Are slidably inserted into each of them. A plunger chamber 28 is formed between the upper end surface of the plunger 9 and the lower end surface of the IO valve 14. The plunger chamber 28 at the end of the housing 6 on the side of the feed pump is referred to as a first plunger chamber 28-1, and the second plunger chamber 28-2 and the third plunger chamber are sequentially arranged in the order toward the shaft tip. 28-3 and a fourth plunger chamber 28-4. The tappet 10 is disposed in each hole 61a so as to be vertically movable. The tappet 10 includes a slider 101, a pin 102, a roller 103, and a bush 104.
And A spring receiving housing portion 101a is formed above the slider 101, and a roller housing portion 101b is formed below the slider 101. The pin 102 is attached to the lower portion of the slider 101 in parallel with the shaft 7 and penetrates the roller housing 101b. Roller 103
The bush 104 is rotatably attached to the pin 102. The first spring supports 11 are arranged at the upper ends of the respective annular recesses 65. The second spring supports 12 are mounted on the lower ends of the plungers 9, respectively, and are housed in the spring receiving housings 101a of the sliders 101, respectively. The spring 13 is disposed between the first spring receiver 11 and the second spring receiver 12, and biases the plunger 9 and the tappet 10 toward the cam 8 via the second spring receiver 12. I have. As shown in FIG. 7, the IO valve 14 is housed in a valve housing hole 64d of the plunger barrel 64. The IO valve 14 includes a valve body 141, an outlet valve 142, an inlet valve 143, and a spring 1
44. The valve body 141 has a chamber 141a, an inflow passage 141b, a communication passage 141c, an insertion hole 141d, and an outflow passage 141e. The fuel supply direction is switched in the chamber 141a. The inflow passage 141b communicates the chamber 141a with the passage portion 64f of the second supply passage 67. A seat surface 141f is formed at one end of the inflow passage 141b. The communication path 141c connects the chamber 141a and the plunger chamber 28. The insertion hole 141d is formed at the upper center of the valve body 141, and communicates with the chamber 141a. Insertion hole 1
A seat surface 141g is formed at one end of 41d. The outflow passage 141 e of the valve body 141 disposed on the front side of the housing main body 61 is provided with a plunger barrel 64.
64g. The outlet valve 142 has a valve portion 142a.
, A neck 142b, an insertion portion 142c, and a mounting portion 142d. The valve portion 142a is provided on the seat surface 14 of the valve body 141.
1 g, and opens and closes a discharge passage 145 described later.
The neck 142b is provided on the lower surface of the valve 142a.
The outer diameter of the neck portion 142b is the valve portion 142a and the insertion portion 142c.
Smaller than the outer diameter of The insertion portion 142c is provided on the neck portion 142b, and is slidably inserted into the insertion hole 141d. Blade portions 142e are formed at equal intervals along the circumferential direction on the outer peripheral portion of the insertion portion 142c, and a groove 142f is formed between the blade portions 142e. The groove 142f and the insertion hole 14
A discharge passage 145 is formed with the inner peripheral surface of 1d. An insertion hole 142g is formed at the center of the insertion portion 142c. The mounting part 142d is formed on the upper surface of the valve part 142a. The inlet valve 143 has a valve part 143a and a mounting part 143b, and most of the parts are inserted into the insertion holes 142g of the outlet valve 142. Valve part 1
The distal end of 43a protrudes from the insertion hole 142g, and is placed on the seating surface 141f of the valve body 141.
Open and close b. The mounting part 143b is provided on the upper surface of the valve part 143a. The spring 144 is mounted on the mounting portion 143b of the inlet valve 143, and
It is housed in the second insertion hole 142g. The spring 144 constantly urges the inlet valve 143 toward the seat surface 141f. The valve holder 15 comprises a holder body 151, a spring seat 152 and a spring 153. The holder body 151 has a plunger barrel 64.
Female screw 64i formed on the upper part of the valve housing hole 64e
To fix the valve body 141 of the IO valve 14 to the plunger barrel 64. The holder body 151 has an accommodation hole 151a and a discharge passage 151b. The accommodation hole 151a is formed in the center of the lower part of the holder main body 151. The outlet valve 142 is accommodated in the accommodation hole 151a so as to be vertically movable. The discharge passage 151b is formed in the center of the upper part of the holder main body 151, and communicates with the housing hole 151a. The spring seat 152 has a housing hole 151a.
Is housed in The spring seat 152 is the mounting part 1
52a and a discharge passage 152b. Discharge passage 1
52b is connected to the discharge passage 151b. The spring 153 is housed in the housing hole 151a.
One end thereof is a mounting portion 142 of the outlet valve 142.
d, and the other end is mounted on the mounting portion 152a of the spring seat 152. The spring 153 constantly urges the valve portion 142a of the outlet valve 142 toward the seat surface 141g of the valve body 141. The first proportional control valve 16 has a valve portion 161. The valve part 161 has an inflow hole 161a and an outflow hole 161b. The valve portion 161 is inserted into the valve insertion portion 66c of the first supply passage 66, and controls the flow rate of fuel flowing from the first supply passage 66 to the second supply passage 67. The second proportional control valve 17 has a valve portion 171. The valve part 171 has an inflow hole 171a and an outflow hole 171b. The valve portion 171 is inserted into the valve insertion portion 66d of the first supply passage 66, and controls the flow rate of fuel flowing from the first supply passage 66 to the second supply passage 67. The overflow valve 18 has a valve portion 181. The valve portion 181 has an inflow hole 181a and an outflow hole 181b.
And The valve portion 181 is inserted into the overflow valve insertion portion 68b of the first return passage 68 to maintain the pressure in the first supply passage 66 within a predetermined range. The orifice 19 is connected to the second return passage 69
Is arranged in the passage portion 69b. The orifice 19 determines the flow rate of fuel returning to the fuel tank 47 through the second return passage 69 per unit time. This amount is the amount of fuel that leaks from the first supply passage 66 to the second supply passage 67 through the valve portions 161 and 171 per unit time when the first and second proportional control valves 16 and 17 are fully closed. It is almost equal to the flow rate. The check valve 20 is disposed in the passage portion 69b of the second return passage 69. The check valve 20 includes a flat valve 201 and a spring 202. Flat valve 20
1 is disposed downstream of the orifice 19, and the orifice 1
9 is opened and closed (the second return passage 69). The spring 202 is disposed downstream of the flat valve 201 and constantly biases the flat valve 201 toward the orifice 19. Next, the operation of this embodiment will be described. When the shaft 7 is driven and rotated by an engine (not shown), the cam 8 rotates together with the shaft 7. The roller 103 of the tappet 10 always contacts the cam surface 8a of the cam 8 by the urging force of the spring 13. Therefore, when the cam 8 rotates, the roller 103 relatively rolls on the cam surface 8a. Since the cam surface 8a has undulation, when the roller 103 rolls on the cam surface 8a, the tappet 10 moves up and down according to the undulation of the cam surface 8a. This tappet 10
The plunger 9 moves up and down by the up and down movement of. Since the feed pump 40 is connected to the shaft 7, when the shaft 7 rotates, the feed pump 40 is also driven, sucks fuel from the fuel tank 47,
The fuel is supplied to the plunger chamber 28. When the plunger 9 moves downward from the top dead center, the pressure in the chamber 141a decreases and the inlet valve 1
43, the back pressure applied to the inflow passage 141 is relatively reduced.
The pressure in b increases. When the pressure in the inflow passage 141b becomes relatively high, the fuel in the inflow passage 141b pushes up the inlet valve 143 against the back pressure of the inlet valve 143 and the urging force of the spring 144. As a result,
The valve portion 143a of the inlet valve 143 has a seat surface 141f.
And the inflow passage 141b opens. When the inflow passage 141b is opened, the fuel from the feed pump 40 is supplied to the first and second supply passages 66,6.
7, is supplied to the plunger chamber 28 through the inflow passage 141b, the chamber 141a, the communication passage 141c, and the like. This state continues until the plunger 9 reaches the bottom dead center. When the plunger 9 moves upward from the bottom dead center, the pressure in the chamber 141a increases, and the inlet valve 1
43 increases, and the inflow passage 141 relatively moves.
The pressure in b decreases. Therefore, the fuel in the inflow passage 141b pushes up the inlet valve 143,
Since the resultant force of the back pressure applied to the inlet valve 143 and the urging force of the spring 144 is larger, the valve portion 143a of the inlet valve 143 is pressed against the seat surface 141f. As a result, the inflow passage 141b is closed. When the inflow passage 141b is closed and the plunger 9 moves further upward, the pressure in the chamber 141a further increases, and the back pressure applied to the outlet valve 142 is reduced by the urging force of the spring 153 of the valve holder 15 and the outlet valve 1
It becomes greater than the resultant force with the pressure downstream of 42. As a result, the valve portion 142a of the outlet valve 142 is
41 g, the discharge passage 145 opens. When the discharge passage 145 is opened, the plunger chamber 2
The fuel pressurized at 8 is supplied to the common rail 48 through the communication passage 141c, the chamber 141a, the discharge passages 145, 152b, 151a and the like. This state continues until the plunger 9 reaches the top dead center. The common rail 48 distributes the supplied fuel and supplies it to each injector 49. Injector 49
Injects fuel into a cylinder bore (not shown) based on a signal from a control unit (not shown). From the feed pump 40 to the plunger chamber 28
The amount of fuel supplied to the first and second proportional control valves 1
The valves 6 and 17 are adjusted by controlling the flow rate of fuel flowing from the first supply passage 66 to the second supply passage 67 per unit time at the valve portions 161 and 171. Excess fuel in the first supply passage 66 is returned to the fuel tank 47 through the first return passage 68. Since the amount of fuel supplied from the feed pump 40 to the first supply passage 66 is greater than the amount of fuel flowing from the first supply passage 66 to the second supply passage 67, the fuel is provided in the first return passage 68. The overflow valve 18 is normally open. The overflow valve 18 used in such a state functions to keep the pressure in the first supply passage 66 within a predetermined range. When the first and second proportional control valves 16 and 17 are in the fully closed state, the flow of fuel cannot be completely stopped, and the fuel flows from the first supply passage 66 to the second supply passage 67. Leaks. The fuel leaked to the second supply passage 67 is supplied to the second return passage 69 and the first return passage 68
Through the fuel tank 47. Since the feed pump 40 is driven by the engine via the shaft 7, the feed pump 4
The fuel discharge amount of 0 is proportional to the engine speed. Thus, when the engine rotates at a high speed, the supply of fuel to the first supply passage 66 becomes excessive, and a large amount of fuel is returned to the fuel tank 47 through the first return passage 68. At this time, the pipe 46 connecting the first return passage 68 and the fuel tank 47 corresponds to the flow rate of the fuel returned to the fuel tank 47.
Is not large enough and the pipe 46 is very long, the pressure in the first return passage 68 may be higher than the pressure in the second return passage 69. However, even if the pressure in the first return passage 68 becomes higher than the pressure in the second return passage 69, the check valve 20 is provided in the second return passage 69, so that the fuel is No backflow. Next, the effect of this embodiment will be described. Since the check valve 20 is provided in the second return passage 69, even if the engine rotates at a high speed and the fuel flows backward from the first return passage 68 to the second return passage 69, the flow of the fuel does not change. Can be prevented by the check valve 20. For this reason, since unnecessary fuel does not flow into the plunger chamber 28, the pumping of fuel from the plunger chamber 28 can be stopped. Although this embodiment is a fuel supply pump for a common rail type fuel supply device, the present invention can be used as a fuel supply pump other than the common rail type fuel supply device. As described above, according to the fuel supply pump of the first aspect, even when the engine is running at a high speed, the pumping of fuel from the plunger chamber can be stopped.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual view of a fuel supply pump according to a first embodiment of the present invention, which is a cross section taken along line II in FIG. FIG. 2 is a front view of a fuel supply pump. FIG. 3 is a plan view of a fuel supply pump. FIG. 4 is a left side view of the fuel supply pump shown in FIG. 1; FIG. 5 is a right side view of the fuel supply pump. FIG. 6 is a sectional view taken along the line VI-VI in FIG. 2; FIG. 7 is an enlarged sectional view of a part of the fuel supply pump. FIG. 8 is a circuit diagram of a common rail type fuel injection device including a fuel supply pump. FIG. 9 is a circuit diagram of a conventional common rail fuel injection device. [Description of Signs] 5 High pressure pump 16 First proportional control valve 17 Second proportional control valve 18 Overflow valve 19 Orifice 20 Check valve 28 Plunger chamber 40 Feed pump 47 Fuel tank 68 First return passage 69 Second Return passage

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kazuya Kubota             Saitama Prefecture Higashi Matsuyama City             Shikisha Bosch Automotive System             Inside F term (reference) 3G066 AA07 AB02 AC09 AD04 BA17                       CA19 CA34 CA35 CA36 CB16                       CE13 DB13

Claims (1)

Claims: 1. A feed pump for supplying fuel from a fuel tank to a plunger chamber, a flow control means for controlling a flow rate of fuel supplied from the feed pump to the plunger chamber, and the flow control A part of the fuel supplied from the feed pump to the flow rate control means is provided to the fuel tank, and is provided to the flow rate control means. An overflow valve for suppressing an increase in fuel pressure, and a second return passage connecting the plunger chamber and the downstream of the overflow valve, and reducing a cross-sectional area of the flow of fuel returning to the fuel tank side. A throttle provided in the second return passage downstream of the throttle;
A fuel supply pump comprising a check valve for preventing a flow of fuel from a downstream side of the throttle to the throttle side.