WO2017203812A1

WO2017203812A1 - Fuel supply pump

Info

Publication number: WO2017203812A1
Application number: PCT/JP2017/011297
Authority: WO
Inventors: 俊亮有冨; 菅波　正幸; 樋熊　真人; 越坂　敦
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2016-05-27
Filing date: 2017-03-22
Publication date: 2017-11-30
Also published as: JP6685176B2; JP2017210935A

Abstract

The objective of the present invention is to provide: a suction valve which has a simple structure requiring a small number of man-hours for processing and ensures a sufficient flow path cross-sectional area so as to enable highly accurate flow rate control by preventing increase in pressure loss even when the flow rate of discharge fuel is high; and a low-cost fuel supply pump using the suction valve. The abovementioned objective can be achieved by a fuel supply pump provided with a pump body having a pressurization chamber formed therein, and with a suction valve disposed on the suction side of the pressurization chamber, the fuel supply pump being further provided with: an overlap part which is disposed between the pressurization chamber and the suction valve and which overlaps with the suction valve in the axial direction of the suction valve; and a plurality of fixation parts which, on a side closer to an outer periphery than an outer-periphery-side surface of the overlap part, are integrally formed with the overlap part, and fix the overlap part, wherein a first flow path is formed between the outer-periphery-side surface of the overlap part and a housing part disposed at a side further closer to the outer periphery than the outer-periphery-side surface of the overlap part, the first flow path is connected to a second flow path on a side closer to the pressurization chamber than a pressurization-chamber-side surface of the overlap part, and the first flow path and the second flow path are formed so as to be contiguously connected by the housing part.

Description

Fuel supply pump

The present invention relates to a fuel supply pump provided with a suction valve.

Conventionally, various proposals have been made regarding the flow path structure connecting the suction valve and the pressurizing chamber. Among them, for example, Japanese Patent Application Laid-Open No. 2010-169080 discloses a structure in which a plurality of through holes are provided in the circumferential direction of the stopper member of the suction valve to form a flow path to the pressurizing chamber. Japanese Patent Application Publication No. 2013-512399 discloses a structure in which an annular clearance is provided on the outer periphery of the suction valve stopper to form a flow path to the pressurizing chamber.

JP 2010-169080 A Special table 2013-512399 gazette

Recently, vigorous efforts have been made to reduce the internal combustion engine's output, fuel efficiency and cost. In response to this, fuel supply pumps are strongly required to have a large flow rate and high pressure of discharged fuel corresponding to high output and low fuel consumption, to improve its control accuracy, and to reduce processing man-hours corresponding to low cost. Yes. Among these, the intake valve is one of the most important parts for satisfying these required performances, and improving the performance is an important issue. Thus, as an example of increasing the flow rate of discharged fuel and improving the flow rate control accuracy, there is a flow channel structure as shown in Patent Document 1. In this structure, a sufficient flow path cross-sectional area is secured by providing a plurality of through-holes so that pressure loss does not increase before and after the flow path even when the discharged fuel is increased in flow rate.

However, in this case, the number of processing steps increases with the number of through holes, and the cost may increase. Furthermore, as an example of securing the channel cross-sectional area with a simpler structure, there is a channel structure as shown in Patent Document 2. In this structure, a sufficient cross-sectional area is ensured by making the outer periphery of the suction valve stopper an annular passage. On the other hand, since the suction valve stopper needs to have a function of regulating the displacement of the valve body, it needs to be fixed to the pump body or the like. However, the method is not disclosed in this structure, and there is a possibility that the function as the suction valve stopper cannot be sufficiently achieved.

Therefore, an object of the present invention is to provide a suction valve that can secure a sufficient flow path cross-sectional area with a simple structure with few processing steps, and a low-cost fuel supply pump to which the suction valve is applied.

In order to solve the above problems, the present invention includes a pump body 1 in which a pressurizing chamber 11 is formed, and a suction valve 30 disposed on the suction side of the pressurizing chamber 11. In the fuel supply pump, the overlapping portion 32d that is disposed between the pressurizing chamber 11 and the suction valve 30 and overlaps the suction valve 30 in the suction valve axial direction, and on the outer peripheral side of the outer peripheral side surface of the overlapping portion. A plurality of fixing portions 32c that are formed integrally with the overlapping portion and fix the overlapping portion 32d, and are arranged on the outer peripheral side of the outer peripheral side surface of the overlapping portion 32d and the outer peripheral side surface of the overlapping portion 32d. A first flow path 32e is formed between the housing portion 31c, the first flow path 32e is connected to the second flow path 32f on the pressurizing chamber side with respect to the pressurizing chamber side surface of the overlapping portion 32d, and the first flow path 32e is connected to the second flow path 32f. 1 channel 3 e and the second flow path 32f is formed so as to be connected in succession by the housing part 31c.

According to the present invention, it is possible to provide a suction valve that can secure a sufficient flow path cross-sectional area with a simple structure with few processing steps, and a low-cost fuel supply pump to which the suction valve is applied. Other configurations, operations, and effects of the present invention will be described in detail in the following examples.

It is sectional drawing of the fuel supply pump which implements Example 1 and 2. FIG. 1 is an overall configuration of a system that implements

Embodiments

1 and 2. It is sectional drawing at the time of fuel supply pump attachment which implements Example 1 and 2. FIG. It is sectional drawing in the suction | inhalation process of the solenoid valve which implements Example 1 and 2. FIG. It is sectional drawing at the time of the discharge process of the solenoid valve which implements Example 1 and 2, and electricity supply. It is sectional drawing at the time of the discharge process of the solenoid valve which implements Example 1 and 2, and no electricity supply. It is a perspective view of the suction valve stopper which implements Example 1. FIG. It is the longitudinal cross-sectional view and 45 degree | times cross-sectional view of the suction valve periphery flow path which implement Example 1. FIG. It is a perspective view of the suction valve stopper which implements Example 2. FIG. It is the longitudinal cross-sectional view and 45 degree | times cross-sectional view of the flow path around the suction valve which implements Example 2. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a diagram showing an example of the overall configuration of a fuel supply system including a fuel supply pump to which the present invention can be applied. First, the configuration and operation of the entire system will be described with reference to this figure.
In FIG. 2, a portion 1 surrounded by a broken line indicates a fuel supply pump main body, and the mechanisms and components shown in the broken line indicate that the fuel supply pump main body 1 is integrally incorporated. Fuel is fed from the fuel tank 20 to the fuel supply pump main body 1 via the feed pump 21, and pressurized fuel is sent from the fuel supply pump main body 1 to the injector 24 side. The engine control unit (control unit) 27 takes in the fuel pressure from the pressure sensor 26 and controls the feed pump 21, the electromagnetic coil 43 in the fuel supply pump main body 1, and the injector 24 in order to optimize this.

In FIG. 2, the fuel in the fuel tank 20 is first pumped up by a feed pump 21 based on a control signal S 1 from an engine control unit (control unit) 27, pressurized to an appropriate feed pressure, and fed through a suction pipe 28. 1 low-pressure fuel inlet (suction joint) 10a. The fuel that has passed through the low-pressure fuel suction port 10a reaches the suction port 31b of the electromagnetic suction valve 300 that constitutes the variable capacity mechanism via the pressure pulsation reducing mechanism 9 and the suction passage 10d. The pressure pulsation reducing mechanism 9 communicates with the annular low-pressure fuel chamber 7a, which makes the pressure variable in conjunction with the plunger 2 that reciprocates by an engine cam mechanism (not shown). The pulsation of the fuel pressure sucked into the suction port 31b is reduced.

The fuel that has flowed into the suction port 31 b of the electromagnetic suction valve 300 passes through the suction valve 30 and flows into the pressurizing chamber 11. The valve position of the intake valve 30 is determined by controlling the electromagnetic coil 43 in the fuel supply pump main body 1 based on the control signal S2 from the engine control unit (control unit) 27. In the pressurizing chamber 11, the reciprocating power is given to the plunger 2 by an engine cam mechanism (not shown). Due to the reciprocating motion of the plunger 2, fuel is sucked from the suction valve 30 in the lowering process of the plunger 2, and the sucked fuel is pressurized in the lifting process of the plunger 2, and the pressure sensor 26 is mounted via the discharge valve mechanism 8. Fuel is pumped to the common rail 23. Thereafter, the injector 24 injects fuel into the engine based on a control signal S3 from the engine control unit (control unit) 27.

The discharge valve mechanism 8 provided at the outlet of the pressurizing chamber 11 includes a discharge valve sheet 8a, a discharge valve 8b that contacts and separates from the discharge valve sheet 8a, and a discharge that urges the discharge valve 8b toward the discharge valve sheet 8a. It is comprised by the valve spring 8c etc. According to the discharge valve mechanism 8, the discharge valve 8b opens when the internal pressure of the pressurizing chamber 11 is higher than the pressure on the discharge passage 12 downstream of the discharge valve 8b and overcomes the drag determined by the discharge valve spring 8c. The pressurized fuel is pumped from the pressurizing chamber 11 to the discharge passage 12 side.

2, 30 is a suction valve, 35 is a rod for controlling the position of the

suction valve

30, 36 is an anchor portion, 33 is a suction valve spring, 40 is a rod biasing spring, 41 is an anchor portion biasing spring. According to this mechanism, the intake valve 30 is urged in the valve closing direction by the intake valve spring 33, and is urged in the valve opening direction by the rod urging spring 40 via the rod 35. Further, the anchor portion 36 is biased in the valve closing direction by an anchor portion biasing spring. The valve position of the suction valve 30 is controlled by driving the rod 35 by the electromagnetic coil 43.

As described above, the fuel supply pump 1 is configured such that the electromagnetic coil 43 in the fuel supply pump main body 1 is controlled by the control signal S2 given to the electromagnetic intake valve 300 by the engine control unit (control unit) 27, and the common rail is connected via the discharge valve mechanism 8. The fuel flow rate is discharged so that the fuel pumped to 23 becomes a desired supply fuel.

In the fuel supply pump 1, the pressurizing chamber 11 and the common rail 23 are communicated by a relief valve 100. The relief valve 100 is a valve mechanism arranged in parallel with the discharge valve mechanism 8. In the relief valve 100, when the pressure on the common rail 23 side exceeds the set pressure of the relief valve 100, the relief valve 100 is opened and the fuel is returned to the pressurizing chamber 11 of the fuel supply pump 1, whereby the pressure in the common rail 23 is increased. Prevent abnormal high pressure conditions.

The relief valve 100 forms a high-pressure channel 110 that communicates the discharge passage 12 on the downstream side of the discharge valve 8b in the fuel supply pump body 1 and the pressurizing chamber 11, and is provided so as to bypass the discharge valve 8b. It is what was done. The high-pressure channel 110 is provided with a relief valve 102 that restricts the flow of fuel in only one direction from the discharge channel to the pressurizing chamber 11. The relief valve 102 is pressed against the relief valve seat 101 by a relief spring 105 that generates a pressing force, and the pressure difference between the pressure chamber 11 and the high-pressure channel 110 is determined by the relief spring 105. If it becomes above, it is set so that the relief valve 102 may leave | separate from the relief valve seat 101, and may open.

As a result, when the common rail 23 has an abnormally high pressure due to a failure of the electromagnetic suction valve 300 of the fuel supply pump 1 or the like, the differential pressure between the discharge passage 110 and the pressurizing chamber 11 becomes equal to or higher than the valve opening pressure of the relief valve 102. Then, the relief valve 102 is opened, and the fuel having an abnormally high pressure is returned from the discharge passage 110 to the pressurizing chamber 11 to protect the high-pressure section piping such as the common rail 23.

FIG. 1 is a diagram showing a specific example of a fuel supply pump body 1 that is mechanically integrated. According to this figure, a plunger 2 that reciprocates (in this case, up and down) by an engine cam mechanism (not shown) in the central height direction shown in the figure is arranged in the cylinder 6, A pressurizing chamber 11 is formed.

Further, according to this figure, the mechanism on the electromagnetic suction valve 300 side is disposed on the left side of the center of the figure, and the discharge valve mechanism 8 is disposed on the right side of the center of the figure. In the upper part of the figure, a low-pressure fuel suction port 10a, a pressure pulsation reduction mechanism 9, a suction passage 10d, and the like are disposed as a fuel suction side mechanism. Further, a plunger internal combustion engine side mechanism 150 is described in the lower center portion of FIG. The plunger internal combustion engine side mechanism 150 is a portion that is embedded and fixed in the internal combustion engine body as shown in FIG. Note that the relief valve 100 mechanism is not shown in the display cross section of FIG. The relief valve 100 mechanism can be displayed in a display section at a different angle, but since it is not directly related to the present invention, explanation and display are omitted.

2 will be described later in detail. First, attachment of the attachment root will be described with reference to FIG. FIG. 3 shows a state in which the mounting root (plunger internal combustion engine side mechanism) 150 is embedded and fixed in the internal combustion engine body. However, in FIG. 3, since the attachment root 150 is described as a center, description of other parts is omitted. In FIG. 3, reference numeral 90 denotes a thick portion of the cylinder head of the internal combustion engine. An attachment root attaching hole 95 is formed in advance in the cylinder head 90 of the internal combustion engine. The attachment root portion mounting hole 95 is configured with a two-stage diameter according to the shape of the attachment root portion 150, and the attachment root portion 150 is fitted and disposed in the root portion attachment hole 95.

In addition, the mounting root 150 is airtightly fixed to the cylinder head 90 of the internal combustion engine. In the example of the airtight fixing arrangement of FIG. 3, the fuel supply pump is in close contact with the plane of the cylinder head 90 of the internal combustion engine using a flange 1 e provided in the pump body 1 and fixed with a plurality of bolts 91.
In addition, the mounting flange 1e is welded to the pump body 1 at the welded portion 1f to form an annular fixed portion. In this embodiment, laser welding is used for welding the welded portion 1f. Further, an O-ring 61 is fitted into the pump body 1 for sealing between the cylinder head 90 and the pump body 1 to prevent engine oil from leaking to the outside.

The plunger root 150 arranged in an airtight manner in this manner is provided with a tappet 92 that converts the rotational movement of the cam 93 attached to the camshaft of the internal combustion engine into a vertical movement and transmits it to the plunger 2 at the lower end 2b of the plunger 2. It has been. The plunger 2 is pressure-bonded to the tappet 92 by the spring 4 through the retainer 15. Thereby, the plunger 2 is reciprocated up and down with the rotational movement of the cam 93.

A plunger seal 13 held at the lower end of the inner periphery of the seal holder 7 is installed in a state in which the plunger seal 13 slidably contacts the outer periphery of the plunger 2 in the lower part of the cylinder 6 in the figure. The fuel can be sealed even when the plunger 2 slides to prevent the fuel from leaking to the outside. At the same time, lubricating oil (including engine oil) for lubricating the sliding portion in the internal combustion engine is prevented from flowing into the pump body 1.

As shown in FIG. 3, the plunger root 150 arranged in an airtight manner reciprocates within the cylinder 6 as the plunger 2 inside the plunger 2 rotates. Returning to FIG. 1, description will be given of the operation of each part accompanying this reciprocating motion. In FIG. 1, a cylinder in which a fuel supply pump main body 1 guides the reciprocating motion of a plunger 2 and has an end (upper side in FIG. 1) formed in a bottomed cylindrical shape so as to form a pressurizing chamber 11 therein. 6 is attached. Further, the pressurizing chamber 11 is connected to an electromagnetic suction valve 300 for supplying fuel and a discharge valve mechanism 8 for discharging fuel from the pressurizing chamber 11 to the discharge passage. A plurality of communication holes 6b are provided to communicate the groove 6a with the pressurizing chamber.

The cylinder 6 is press-fitted and fixed to the fuel supply pump main body 1 at the outer diameter, and is sealed with a press-fitted portion cylindrical surface so that fuel pressurized from the gap with the fuel supply pump main body 1 does not leak to the low pressure side. In addition, the cylinder 6 has a small-diameter portion 6 c at the outer diameter on the pressurizing chamber side. When the fuel in the pressurizing chamber 11 is pressurized, the cylinder 6 exerts a force on the low pressure fuel chamber 10c side. However, by providing the pump body 1 with the small diameter portion 1a, the cylinder 6 is pulled out on the low pressure fuel chamber 10c side. To prevent that.
By bringing the surfaces into contact with a plane in the axial direction, in addition to the sealing of the contact cylindrical surface of the fuel supply pump main body 1 and the cylinder 6, it also functions as a double seal.

A damper cover 14 is fixed to the head of the fuel supply pump main body 1. The damper cover 14 is provided with a suction joint 51 and forms a low-pressure fuel suction port 10a. The fuel that has passed through the low-pressure fuel suction port 10a passes through the filter 52 fixed inside the suction joint 51, and reaches the suction port 31b of the electromagnetic suction valve 300 via the pressure pulsation reducing mechanism 9 and the low-pressure fuel flow path 10d. .

The suction filter 52 in the suction joint 51 serves to prevent foreign matter existing between the fuel tank 20 and the low-pressure fuel inlet 10a from being absorbed into the fuel supply pump by the flow of fuel.

The plunger 2 has a large-diameter portion 2a and a small-diameter portion 2b, so that the volume of the annular low-pressure fuel chamber 7a increases and decreases by the reciprocating motion of the plunger. The volume increase / decrease is communicated with the low-pressure fuel chamber 10 by the fuel passage 1d (FIG. 3), so that when the plunger 2 is lowered, the pressure is reduced from the annular low-pressure fuel chamber 7a to the low-pressure fuel chamber 10; A fuel flow is generated from the fuel chamber 10 to the annular low-pressure fuel chamber 7a. As a result, the flow rate of fuel into and out of the pump in the pump suction process or return process can be reduced, and the function of reducing pulsation is provided.

The low pressure fuel chamber 10 is provided with a pressure pulsation reducing mechanism 9 for reducing the pressure pulsation generated in the fuel supply pump from spreading to the fuel pipe 28 (FIG. 2). When the fuel that has once flowed into the pressurizing chamber 11 is returned to the suction passage 10d (suction port 31b) through the suction valve body 30 that is opened again for capacity control, it is returned to the suction passage 10d (suction port 31b). Pressure pulsation occurs in the low pressure fuel chamber 10 due to the fuel. However, the pressure pulsation reducing mechanism 9 provided in the low-pressure fuel chamber 10 is formed of a metal damper in which two corrugated disk-shaped metal plates are bonded together on the outer periphery and an inert gas such as argon is injected inside. The pressure pulsation is absorbed and reduced as the metal damper expands and contracts. Reference numeral 9b denotes a mounting bracket for fixing the metal damper to the inner peripheral portion of the fuel supply pump main body 1, and since it is installed on the fuel passage, a plurality of holes are provided to allow fluid to freely flow between the front and back of the mounting bracket 9b. I can do it.

The discharge valve mechanism 8 provided at the outlet of the pressurizing chamber 11 includes a discharge valve sheet 8a, a discharge valve 8b that contacts and separates from the discharge valve sheet 8a, and a discharge valve spring that urges the discharge valve 8b toward the discharge valve sheet 8a. 8c, a discharge valve holder 8d that accommodates the discharge valve 8b and the discharge valve seat 8a. The discharge valve sheet 8a and the discharge valve holder 8d are joined by welding at a contact portion 8e to form an integral discharge valve mechanism 8. Forming. A stepped portion 8f that forms a stopper that restricts the stroke of the discharge valve 8b is provided inside the discharge valve holder 8d.

In FIG. 1, when there is no fuel differential pressure in the pressurizing chamber 11 and the fuel discharge port 12, the discharge valve 8b is pressed against the discharge valve seat 8a by the urging force of the discharge valve spring 8c and is in a closed state. Only when the fuel pressure in the pressurizing chamber 11 becomes higher than the fuel pressure in the fuel discharge port 12, the discharge valve 8 b opens against the discharge valve spring 8 c, and the fuel in the pressurization chamber 11 is discharged from the fuel discharge port. 12 is discharged to the common rail 23 through a high pressure. When the discharge valve 8b is opened, it comes into contact with the discharge valve stopper 8f, and the stroke is limited. Accordingly, the stroke of the discharge valve 8b is appropriately determined by the discharge valve stopper 8d. As a result, the stroke is too large, and the fuel discharged at high pressure to the fuel discharge port 12 due to the delay in closing the discharge valve 8b can be prevented from flowing back into the pressurizing chamber 11 again, and the efficiency of the fuel supply pump is reduced. Can be suppressed. In addition, when the discharge valve 8b repeats opening and closing movements, the discharge valve 8b is guided on the inner peripheral surface of the discharge valve holder 8d so as to move only in the stroke direction. By doing so, the discharge valve mechanism 8 becomes a check valve that restricts the flow direction of fuel.

Next, the structure on the electromagnetic suction valve 300 side, which is the main part of the present invention, will be described with reference to FIGS. 4 shows the state in the suction process among the steps of suction, return, and discharge in the pump operation, and FIGS. 5 and 6 show the state in the discharge process. First, the structure on the electromagnetic suction valve 300 side will be described with reference to FIG. The structure on the electromagnetic suction valve 300 side is mainly composed of a suction valve part A mainly composed of the suction valve 30, a solenoid mechanism part B mainly composed of the rod 35 and the anchor part 36, and an electromagnetic coil 43. First, the intake valve portion A includes an intake valve 30, an intake valve seat 31, an intake valve stopper 32, an intake valve biasing spring 33, and an intake valve holder 34. Among these, the suction valve seat 31 is cylindrical, and has a seat portion 31a in the axial direction on the inner peripheral side and a plurality of suction passage portions 31b radially about the cylindrical axis.

The intake valve holder 34 has claws in two or more directions radially, and the outer peripheral side of the claws is fitted and held coaxially on the inner peripheral side of the intake valve seat 31. Further, a suction valve stopper 32 having a cylindrical shape and a collar shape at one end is fitted and held on the inner peripheral cylindrical surface of the suction valve holder 34.

The suction valve urging spring 33 is disposed on the inner peripheral side of the suction valve stopper 32 in a small diameter part for stabilizing one end of the spring coaxially, and the suction valve 30 is inhaled with the suction valve seat part 31a. Between the valve stoppers 32, a suction valve biasing spring 33 is fitted into the valve guide portion 30b. The suction valve urging spring 33 is a compression coil spring and is installed so that the urging force acts in a direction in which the suction valve 30 is pressed against the suction valve seat portion 31a. It is not limited to the compression coil spring, and any form may be used as long as it can obtain an urging force, and a leaf spring having an urging force integrated with the suction valve may be used.

By configuring the suction valve portion A in this way, in the pump suction process, the fuel that has passed through the suction passage 31b and entered the interior passes between the suction valve 30 and the seat portion 31a, and the suction valve 30 The fuel passes through between the outer peripheral side and the claw of the suction valve holder 34, passes through the passage of the fuel supply pump main body 1 and the cylinder, and flows the fuel into the pressurizing chamber. Further, in the pump discharge process, the intake valve 30 performs contact sealing with the intake valve seat portion 31a, thereby fulfilling the function of a check valve that prevents backflow of fuel to the inlet side.

In order to smooth the movement of the suction valve 30, a passage 32 a is provided in order to release the hydraulic pressure on the inner peripheral side of the suction valve stopper according to the movement of the suction valve 30.

The axial movement amount 30e of the suction valve 30 is limited by the suction valve stopper 32. This is because if the amount of movement is too large, the reverse flow rate increases due to a response delay when the intake valve 30 is closed, and the performance as a pump decreases. The restriction of the movement amount can be defined by the axial shape and size of the suction valve seat 31a, the suction valve 30, and the suction valve stopper 32, and the fixed position.

The suction valve stopper 32 is provided with a protrusion 32b so that the contact area with the suction valve stopper 32 is reduced when the suction valve 32 is open. This is because the intake valve 32 is likely to be separated from the intake valve stopper 32 during the transition from the open state to the closed state, that is, the valve closing response is improved. When there is no annular protrusion, that is, when the contact area is large, a large squeeze force acts between the intake valve 30 and the intake valve stopper 32, and the intake valve 30 is difficult to be separated from the intake valve 32.

The suction valve 30, the suction valve seat 31a, and the suction valve stopper 32 are made of a heat-treated martensitic stainless steel that has high strength, high hardness, and excellent corrosion resistance in order to repeatedly collide with each other. The suction valve spring 33 and the suction valve holder 34 are made of austenitic stainless steel in consideration of corrosion resistance.

Next, the solenoid mechanism B will be described. The solenoid mechanism part B includes a rod 35 that is a movable part, an anchor part 36, a rod guide 37 that is a fixed part, an outer core 38, a fixed core 39, a rod biasing spring 40, and an anchor part biasing spring 41.

The rod 35 and the anchor part 36 which are movable parts are configured as separate members. The rod 35 is slidably held in the axial direction on the inner peripheral side of the rod guide 37, and the inner peripheral side of the anchor portion 36 is slidably held on the outer peripheral side of the rod 35. That is, both the rod 35 and the anchor portion 36 are configured to be slidable in the axial direction as long as they are geometrically restricted.

The anchor portion 36 has one or more through holes 36a penetrating in the axial direction of the component in order to move freely and smoothly in the axial direction in the fuel, and eliminates the restriction of movement due to the pressure difference before and after the anchor portion as much as possible. .

The rod guide 37 is inserted in the radial direction on the inner peripheral side of the hole into which the intake valve of the fuel supply pump main body 1 is inserted, and in the axial direction, is abutted against one end portion of the intake valve seat. The outer core 38 that is fixed to the main body 1 by welding and the fuel supply pump main body 1 are arranged in a sandwiched manner. The rod guide 37 is also provided with a through hole 37a penetrating in the axial direction in the same manner as the anchor portion 36, and the pressure of the fuel chamber on the anchor portion side controls the movement of the anchor portion so that the anchor portion can move freely and smoothly. It is configured not to interfere.

The outer core 38 has a thin cylindrical shape on the side opposite to the portion to be welded with the fuel supply pump main body, and is fixed by welding in such a manner that the fixed core 39 is inserted on the inner peripheral side thereof. A rod urging spring 40 is arranged on the inner peripheral side of the fixed core 39 with the narrow diameter portion as a guide, the rod 35 comes into contact with the suction valve 30, and the suction valve is pulled away from the suction valve seat portion 31a, that is, suction. Energizing force is applied in the valve opening direction.

The anchor portion biasing spring 41 is disposed so as to apply a biasing force to the anchor portion 36 in the direction of the rod collar portion 35a while inserting one end into a cylindrical central bearing portion 37b provided on the center side of the rod guide 37 and maintaining the same axis. It is said. The movement amount 36e of the anchor portion 36 is set to be larger than the movement amount 30e of the intake valve 30. This is because the intake valve 30 is surely closed.

Since the rod 35 and the rod guide 37 slide with each other and the rod 35 repeatedly collides with the intake valve 30, a heat-treated martensitic stainless steel is used in consideration of hardness and corrosion resistance. The anchor portion 36 and the fixed core 39 use magnetic stainless steel to form a magnetic circuit, and the rod urging spring 40 and the anchor portion urging spring 41 use austenitic stainless steel in consideration of corrosion resistance.

According to the above configuration, the intake valve portion A and the solenoid mechanism portion B are configured by organically arranging three springs. The suction valve biasing spring 33 configured in the suction valve unit A, the rod biasing spring 40 and the anchor unit biasing spring 41 configured in the solenoid mechanism unit B correspond to this. In this embodiment, any spring uses a coil spring, but any spring can be used as long as it can obtain an urging force.

The relationship between these three spring forces is constituted by the following equation.
(Equation 1) Rod biasing spring 40 force> Anchor portion biasing spring 41 force + suction valve biasing spring 33 force + force for closing the suction valve by fluid (1)
Due to the relationship of the expression (1), the rod 35 acts as a force f1 in the direction in which the intake valve 30 is pulled away from the intake valve seat portion 31a, that is, in the direction in which the valve opens, due to each spring force when no current is applied. From the equation (1), the force f1 in the direction in which the valve opens is expressed by the following equation (2).
(Equation 2)
f1 = Rod biasing spring force− (anchor portion biasing spring force + suction valve biasing spring force + force for closing the suction valve by fluid) (2)

Finally, the configuration of the coil part C will be described. The coil portion C includes a first yoke 42, an electromagnetic coil 43, a second yoke 44, a bobbin 45, a terminal 46, and a connector 47. A coil 43 in which a copper wire is wound around the bobbin 45 is disposed so as to be surrounded by the first yoke 42 and the second yoke 44, and is molded and fixed integrally with a connector which is a resin member. The respective ends of the two terminals 46 are respectively connected to both ends of the copper wire of the coil so as to be energized. Similarly, the terminal 46 is molded integrally with the connector, and the remaining end can be connected to the engine control unit side.

The coil part C is fixed by press-fitting the hole at the center of the first yoke 42 into the outer core 38. At that time, the inner diameter side of the second yoke 44 is in contact with the fixed core 39 or close to a slight clearance.

Both the first yoke 42 and the second yoke 44 are made of magnetic stainless steel in order to constitute a magnetic circuit and in consideration of corrosion resistance, and the bobbin 45 and the connector 47 are made of high strength heat resistant resin in consideration of strength characteristics and heat resistance characteristics. . The coil 43 is made of copper, and the terminal 46 is made of brass plated with metal.

By configuring the solenoid mechanism part B and the coil part C as described above, the outer core 38, the first yoke 42, the second yoke 44, the fixed core 39, the anchor part 36, as shown by the arrow part in FIG. When a magnetic circuit is formed and a current is applied to the coil, a magnetic attractive force is generated between the fixed core 39 and the anchor portion 36, and a force attracted to each other is generated. In the outer core 38, the axial portion where the fixed core 39 and the anchor portion 36 generate the magnetic attractive force is made as thin as possible, so that almost all of the magnetic flux passes between the fixed core 39 and the anchor portion 36. The magnetic attractive force can be obtained efficiently.

When the magnetic attraction force exceeds the force f1 in the direction in which the valve of formula (2) opens, the movement of the anchor portion 36, which is a movable portion, together with the rod 35 to the fixed core 39, and the core 39 and the anchor portion 36 makes contact and allows contact to continue.

According to the above configuration of the fuel supply pump according to the present invention, the operation is performed as follows in each step of suction, return, and discharge in the pump operation.

First, the inhalation process will be described. In the suction process, the plunger 2 moves in the direction of the cam 93 (the plunger 2 is lowered) by the rotation of the cam 93 in FIG. That is, the position of the plunger 2 is moved from the top dead center to the bottom dead center. When in the suction process state, for example, referring to FIG. 1, the volume of the pressurizing chamber 11 increases and the fuel pressure in the pressurizing chamber 11 decreases. In this step, when the fuel pressure in the pressurizing chamber 11 becomes lower than the pressure in the suction passage 10d, the fuel passes through the suction valve 30 in the open state, and the communication hole 1b provided in the fuel supply pump main body 1 and the cylinder It passes through the outer

peripheral passages

6 a and 6 b and flows into the pressurizing chamber 11.

The positional relationship of each part on the electromagnetic suction valve 300 side in the suction process is shown in FIG. 4 and will be described with reference to FIG. In this state, the electromagnetic coil 43 remains in a non-energized state and no magnetic biasing force is acting. Therefore, the suction valve 30 is pressed against the rod 35 by the urging force of the rod urging spring 40 and remains open.

Next, the return process will be described. In the returning step, the plunger 2 moves in the upward direction by the rotation of the cam 93 in FIG. That is, the plunger 2 position starts to move from the bottom dead center to the top dead center. At this time, the volume of the pressurizing chamber 11 decreases with the compression motion after the suction in the plunger 2, but in this state, the fuel once sucked into the pressurizing chamber 11 is again sucked through the suction valve 30 in the valve open state. Since the pressure is returned to the passage 10d, the pressure in the pressurizing chamber does not increase. This process is called a return process.

In this state, when a control signal from the engine control unit (control unit) 27 is applied to the electromagnetic suction valve 300, the process returns from the return process to the discharge process. When the control signal is applied to the electromagnetic suction valve 300, a magnetic attractive force is generated in the coil part C, and this acts on each part. FIG. 5 shows the positional relationship of the respective parts on the electromagnetic suction valve 300 side when the magnetic attractive force is applied, and this will be described with reference to FIG. In this state, a magnetic circuit is formed by the outer core 38, the first yoke 42, the second yoke 44, the fixed core 39, and the anchor portion 36. When a current is applied to the coil, magnetic attraction is performed between the fixed core 39 and the anchor portion 36. A force is generated and a force that is attracted to each other is generated. When the anchor portion 36 is sucked by the fixed core 39 which is a fixed portion, the rod 35 moves in a direction away from the intake valve 30 by the locking mechanism of the anchor portion 36 and the rod collar portion 35a. At this time, the suction valve 30 is closed by the biasing force of the suction valve biasing spring 33 and the fluid force caused by the fuel flowing into the suction passage 10d. After closing the valve, the fuel pressure in the pressurizing chamber 11 rises with the upward movement of the plunger 2, and when the pressure exceeds the pressure at the fuel discharge port 12, high-pressure discharge of fuel is performed via the discharge valve mechanism 8, and to the common rail 23. Supplied. This process is called a discharge process.

That is, the compression process of the plunger 2 (the ascending process from the lower start point to the upper start point) includes a return process and a discharge process. And the quantity of the high-pressure fuel discharged can be controlled by controlling the energization timing to the coil 43 of the electromagnetic suction valve 300. If the timing of energizing the electromagnetic coil 43 is advanced, the ratio of the return process in the compression process is small and the ratio of the discharge process is large. That is, the amount of fuel returned to the suction passage 10d is small and the amount of fuel discharged at high pressure is large. On the other hand, if the timing of energization is delayed, the ratio of the return process in the compression process is large and the ratio of the discharge process is small. That is, the amount of fuel returned to the suction passage 10d is large, and the amount of fuel discharged at high pressure is small. The energization timing to the electromagnetic coil 43 is controlled by a command from the engine control unit (control unit) 27.

By configuring as described above, the amount of fuel discharged at high pressure can be controlled to the amount required by the internal combustion engine by controlling the timing of energizing the electromagnetic coil 43.

FIG. 6 shows the positional relationship of each part on the electromagnetic suction valve 300 side in the discharge process. Here, a diagram of a non-energized state in which the energization of the electromagnetic coil 43 is released in a state where the suction valve is closed after the pressure in the pressurizing chamber has sufficiently increased is shown. In this state, in preparation for the next cycle process, a system is in place to effectively generate and act the next magnetic attractive force. This structure is characterized by the establishment of this system.

In this embodiment, a case where the suction valve holder 34 is integrated with the suction valve stopper 32 and the flow path structure of the present invention is formed by the shape thereof will be described as an example. The shape of the suction valve stopper 32 in this embodiment is shown in FIG. The purpose of this embodiment is to secure a sufficient flow path cross-sectional area with a simple structure with a small number of processing steps, and to prevent an increase in pressure loss even when the flow rate of discharged fuel is increased. The detailed structure for this will be described below. As a result, it is possible to provide an electromagnetic suction valve that realizes highly accurate flow rate control and a low-cost fuel supply pump to which it is applied.

The suction valve stopper 32 is provided with a fixed portion 32c on the outermost periphery thereof, and this portion is fitted and held in the inner peripheral cylindrical surface of the housing portion 31c. Further, a disc-like overlapping portion 32d is provided near the center portion, and the suction valve 30 is arranged on the side surface.

FIG. 8 shows a cross-sectional view of the suction valve portion A when the suction valve stopper 32 shown in FIG. 7 is assembled. A vertical sectional view is shown in the upper stage, and a 45 degree sectional view is shown in the lower stage. The overlapping portion 32d is disposed between the pressurizing chamber 11 and the suction valve 30 and overlaps the suction valve 30 in the suction valve axial direction, and is formed integrally with the overlapping portion 32d on the outer peripheral side of the outer peripheral side surface of the overlapping portion 32d. And a plurality of fixing portions 32c for fixing the overlapping portion 32d. And the 1st flow path 32e is formed between the outer peripheral side surface of the overlap part 32d, and the housing part 31c arrange | positioned further on the outer peripheral side rather than the outer peripheral side surface of the overlap part 32d, and the 1st flow path 32e is the overlap part 32d. The first flow path 32e and the second flow path 32f are formed so as to be continuously connected by the housing portion 31c while being connected to the second flow path 32f closer to the pressurization chamber than the side surface of the pressurization chamber. Further, the plurality of fixing portions 32c are configured to be positioned on the pressure chamber side with respect to the suction valve side surface of the overlapping portion 32d, and the outer peripheral side surface of the overlapping portion 32d and the suction valve side of the plurality of fixing portions 32c are arranged. A first flow path 32e is formed by the surface, and a second flow path 32f that connects the first flow path 32e and the pressurizing chamber 11 is formed between adjacent fixing portions 32d.

By adopting this configuration, it is possible to form a flow path without carrying out drilling with a large number of processing steps, and it is possible to fix the suction valve stopper 32 to the housing portion 31c, which is advantageous in terms of cost reduction. is there.

Further, the thickness of the plurality of fixed portions 32c in the suction valve axial direction is configured to be thinner than the thickness of the overlapping portion 32d in the suction valve axial direction, and the surface on the pressure chamber side of the plurality of fixed portions 32c is You may comprise so that it may be located in the suction valve side rather than the surface by the side of the pressurization chamber of the overlap part 32d.

The flow path cross-sectional area of the second flow path 32f is smaller than the first flow path 32e by the fixed portion 32c, and the contribution to the pressure loss is large. As described above, by reducing the thickness of the plurality of fixing portions 32c, the axial distance of the second flow path 32f that greatly contributes to pressure loss can be shortened, which is advantageous from the viewpoint of reducing pressure loss. .

Further, as assumed in the present embodiment, a part of the overlapping portion 32d comes into contact with the suction valve 30 so that the suction valve stopper 32 restricts the movement in the valve opening direction, or the overlapping portion 32d. However, you may comprise so that the spring holding | maintenance part 32h which hold | maintains the suction valve spring 33 which urges | biases the suction valve 30 in the valve closing direction may be formed. Further, with respect to the fixing method of the suction valve stopper 32, the plurality of fixing portions 32d have a press-fit portion 32i that is press-fitted into the inner peripheral surface of the hole 1c formed in the pump body 1 or the inner peripheral surface of the housing portion 31c on the outer peripheral side. To prepare for. The overlapping portion 32d and the plurality of fixing portions 32c are preferably formed of a pressed part or a forged part.

This makes it possible to simplify the structure of the intake valve portion A by consolidating a plurality of functions in the intake valve stopper 32 and effectively utilizing the space. In addition, by forming the suction valve stopper 32 by a press manufacturing method or a forging manufacturing method that requires fewer processing steps than hole processing, the processing steps can be reduced, which is advantageous from the viewpoint of cost reduction.

Further, regarding the arrangement of the fixing portion 32c, the plurality of fixing portions 32c are arranged at a predetermined interval in the circumferential direction on the outer peripheral side of the outermost peripheral end portion of the outer peripheral side surface of the overlapping portion 32d, and the second flow path 32f is overlapped. It forms in the outer peripheral side rather than the outermost peripheral edge part of the outer peripheral side surface of the part 32d. Further, the outermost peripheral end portion of the outer peripheral side surface of the overlapping portion 32 c is configured to be positioned on the outer peripheral side with respect to the outermost peripheral end portion of the outer peripheral surface of the suction valve 30.

By doing so, it is possible to prevent the fuel flow from the pressurizing chamber 11 from directly hitting the suction valve 30 and increasing the fluid force in the valve closing direction to cause erroneous valve closing. Thereby, the improvement of flow control accuracy can be achieved.

Overall, using the configuration of this embodiment ensures a sufficient flow path cross-sectional area with a simple structure with few processing steps, and prevents an increase in pressure loss even when the flow rate of discharged fuel is increased. It is possible to provide an intake valve that realizes a proper flow rate control and a low-cost fuel supply pump to which the intake valve is applied.

In the present embodiment, a modification of the first embodiment will be described. FIG. 9 shows the shape of the suction valve stopper 32 according to the present embodiment. With respect to the shape of the first embodiment shown in FIG. 7, a feature is that a portion (shown by a dotted line) between a plurality of adjacent fixing portions 32c is excluded.
FIG. 10 shows a cross-sectional view of the suction valve portion A when the suction valve stopper 32 shown in FIG. 9 is assembled. A vertical sectional view is shown in the upper stage, and a 45 degree sectional view is shown in the lower stage. The plurality of fixing portions 32c are configured to be positioned on the pressure chamber side with respect to the suction valve side surface of the overlapping portion 32d, and the outer peripheral side surface of the overlapping portion 32d and the suction valve side surface of the plurality of fixing portions 32c Thus, the first flow path 32e is formed, and the second flow path 32f that connects the first flow path 32e and the pressurizing chamber 11 is formed between the adjacent fixing portions 32c. The plurality of fixing portions 32c overlap with the inner peripheral surface of the plurality of fixing portions 32c in the suction valve axial direction, and the space 32g is closer to the pressurizing chamber than the pressurizing chamber side surface of the overlapping portion 32d. The space 32g is formed so as to form a part of the second flow path 32f.
By doing so, the second flow path 32f is enlarged in the radial direction more than the projected area seen from the axial direction, and a larger cross-sectional area can be secured with a simple structure, which is advantageous for reducing pressure loss. It is.

Further, in forming these shapes, the plurality of fixing portions 32c are formed by pressing the plurality of fixing portions 32c toward the axial pressure chamber side with respect to the overlapping portion 32d by a press manufacturing method or a forging manufacturing method. Is configured to be arranged closer to the pressurizing chamber than the surface of the overlapping portion 32d on the pressurizing chamber side. Alternatively, the plurality of fixing portions 32c are configured so that substantially all of the fixing portions 32c are arranged closer to the pressurizing chamber side than the end portion on the pressurizing chamber side of the surface of the overlapping portion 32d on the pressurizing chamber side.
By doing so, it is possible to form a plurality of fixing portions 32c and spaces 32g simultaneously with the formation of the flow path, and to reduce the number of processing steps.
Further, the suction valve stopper 32 may be provided with a spring holding portion 32h as in the case of the first embodiment. In this case, the overlapping portion 32d has a recess 32j that is recessed toward the pressurizing chamber on the inner peripheral side, and holds the spring 33 that biases the suction valve 30 in the valve closing direction in the recess 32j. And the recessed part end part most formed in the pressurizing chamber side in the recessed part 32j and the fixing | fixed part end part formed in the most pressurizing chamber side in the some fixing | fixed part 32c are substantially the same in the suction valve axial direction. It forms in a position, or it forms so that the direction of a recessed part edge part may be located in the pressurization chamber side rather than a fixed part edge part.
In this way, a plurality of functions can be integrated into the suction valve stopper and the structure can be simplified, and the recess 32j can be formed simultaneously with the flow path formation by a press manufacturing method or a forging manufacturing method. This is advantageous from the viewpoint of cost reduction.

In general, if the configuration of this embodiment is used, the flow passage cross-sectional area is secured larger than that of the first embodiment with a simple structure with fewer processing steps, and even when the flow rate of discharged fuel is increased, the pressure loss is reduced. It is possible to provide an intake valve that prevents the increase and realizes highly accurate flow rate control, and a low-cost fuel supply pump to which the intake valve is applied.

Although all the explanations are finished above, the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. In addition, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

1: Pump body 2: Plunger 6: Cylinder 7: Seal holder 8: Discharge valve mechanism 9: Pressure pulsation reduction mechanism 10a: Low pressure fuel inlet 11: Pressurization chamber 12: Fuel outlet 13: Plunger seal 27: Engine control unit (Control part)
30: Suction valve 31: Suction valve seat 32: Suction valve stopper 33: Suction valve spring 35: Rod 36: Anchor part 38: Outer core 39: Fixed core 40: Rod biasing spring 41: Anchor part biasing spring 43: Electromagnetic coil

Claims

In a fuel supply pump comprising a pump body in which a pressurizing chamber is formed, and a suction valve arranged on the suction side of the pressurizing chamber,
An overlapping portion that is disposed between the pressurizing chamber and the suction valve and overlaps the suction valve in the suction valve axial direction, is formed integrally with the overlapping portion on the outer peripheral side of the outer peripheral side surface of the overlapping portion, A plurality of fixing portions for fixing the overlapping portion;
A first flow path is formed between the outer peripheral side surface of the overlapping portion and the housing portion disposed further on the outer peripheral side than the outer peripheral side surface of the overlapping portion, and the first flow path is a side surface of the pressure chamber of the overlapping portion. The fuel supply pump is formed so as to be connected to the second flow path closer to the pressurizing chamber and to be continuously connected to the first flow path and the second flow path by the housing portion.
The fuel supply pump according to claim 1, wherein
The plurality of fixing portions are configured to be positioned on the pressure chamber side with respect to the suction valve side surface of the overlapping portion, and the outer peripheral side surface of the overlapping portion and the suction valve side surface of the plurality of fixing portions; In the fuel supply pump, the first flow path is formed, and the second flow path is formed between the adjacent fixing portions to communicate the first flow path and the pressurizing chamber.
In a fuel supply pump comprising a pump body in which a pressurizing chamber is formed, and a suction valve arranged on the suction side of the pressurizing chamber,
An overlapping portion that is disposed between the pressurizing chamber and the suction valve and overlaps the suction valve in the suction valve axial direction, is formed integrally with the overlapping portion on the outer peripheral side of the outer peripheral side surface of the overlapping portion, A plurality of fixing portions for fixing the overlapping portion;
The plurality of fixing portions are configured to be positioned on the pressure chamber side with respect to the suction valve side surface of the overlapping portion, and the outer peripheral side surface of the overlapping portion and the suction valve side surface of the plurality of fixing portions; Thus, a fuel supply pump in which a first flow path is formed and a second flow path is formed between the adjacent fixing portions to communicate the first flow path and the pressurizing chamber.
The fuel supply pump according to claim 3.
The plurality of fixing portions are formed at a position overlapping the inner peripheral surface of the plurality of fixing portions in the suction valve axial direction, and a space is formed closer to the pressurizing chamber than the pressurizing chamber side surface of the overlapping portion, A fuel supply pump in which the space forms part of the second flow path.
The fuel supply pump according to claim 1 or 3,
The thickness of the plurality of fixed portions in the suction valve axial direction is configured to be thinner than the thickness of the overlapping portions in the suction valve axial direction, and the surfaces of the plurality of fixed portions on the pressure chamber side are overlapped with each other. A fuel supply pump configured to be positioned closer to the suction valve than the surface of the pressurizing chamber.
The fuel supply pump according to claim 1 or 3,
The plurality of fixing portions are fuel supply pumps arranged closer to the pressurizing chamber than the surface of the overlapping portion on the pressurizing chamber.
The fuel supply pump according to claim 5, wherein
The plurality of fixed portions are fuel supply pumps in which substantially all of the plurality of fixed portions are arranged closer to the pressurizing chamber side than the end portion on the pressurizing chamber side of the surface of the overlapping portion on the pressurizing chamber side.
The fuel supply pump according to claim 1 or 3,
The fuel supply pump is a suction valve stopper that restricts movement of the suction valve in the valve opening direction.
The fuel supply pump according to claim 1 or 3,
The fuel supply pump including a spring holding portion that holds a spring that biases the suction valve in a valve closing direction.
The fuel supply pump according to claim 1 or 3,
The plurality of fixed portions are arranged at a predetermined interval in the circumferential direction on the outer peripheral side than the outermost peripheral end portion of the outer peripheral side surface of the overlapping portion,
The fuel supply pump in which the second flow path is formed on the outer peripheral side of the outermost peripheral end portion of the outer peripheral side surface of the overlapping portion.
The fuel supply pump according to claim 1 or 3,
The plurality of fixing portions are arranged closer to the pressurizing chamber than the surface of the overlapping portion on the pressurizing chamber side, and the overlapping portion is positioned at a position overlapping the inner peripheral surface of the plurality of fixing portions in the suction valve axial direction. A fuel supply pump in which a space is formed in the pressurizing chamber side of the surface of the pressurizing chamber and the space communicates with the second flow path.
The fuel supply pump according to claim 1 or 3,
The overlapping portion and the plurality of fixed portions are fuel supply pumps formed of pressed parts or forged parts.
The fuel supply pump according to claim 1 or 3,
The plurality of fixed portions are fuel supply pumps having press-fitting portions, which are press-fitted into holes formed in the pump body, on an outer peripheral side.
The fuel supply pump according to claim 1 or 3,
A fuel supply pump configured such that an outermost peripheral end portion of an outer peripheral side surface of the overlapping portion is positioned on an outer peripheral side with respect to an outermost peripheral end portion of an outer peripheral surface of the suction valve.
The fuel supply pump according to claim 1 or 3,
The overlapping portion has a concave portion recessed on the inner circumferential side toward the pressurizing chamber side, and holds a spring that biases the suction valve in the valve closing direction in the concave portion,
The end of the recessed portion formed closest to the pressurizing chamber in the recessed portion and the end of the fixed portion formed closest to the pressurizing chamber in the plurality of fixed portions are formed at substantially the same position in the suction valve axial direction. Or a fuel supply pump formed such that the end of the recess is positioned closer to the pressurizing chamber than the end of the fixed part.