Patent Description:
In hydraulic equipment such as pumps, a direct-acting relief valve that regulates a relief pressure by a spring for pushing a valve body is widely adopted, and it is known that the opening angle of the seat surface affects the seating performance and sealing performance of the valve body (for example, see PTL <NUM>).

In this PTL <NUM>, there is the description "most of the valve portion of the valve body is a ball or a ball shape, <NUM>° to <NUM>° are preferable for the opening angle of the seat surface on which the valve seats from the meaning of improving both the seating performance and sealing performance, and usually set to <NUM>°". PTL <NUM> shows a high pressure pump which includes a pressurization portion, a discharge portion, a body portion, a valve member, an urging member, valve hold member and a limiting portion. The body portion includes a relief passage, an inlet, a valve seat, and an outlet. The valve member includes a large diameter portion and a small diameter portion. The small diameter portion is located between the valve seat and the large diameter portion and has an outer diameter smaller than an outer diameter of the large diameter portion. The valve hold member surrounding and holding the large diameter portion. The limiting portion capable of limiting a motion of the valve hold member in a separation direction.

In the technique disclosed in PTL <NUM>, the opening angle of the seat surface (called a seat angle) is defined. However, if the relief pressure (called the set valve opening pressure) is not set properly, the sealing performance cannot be maintained, and leakage may occur, leading to cavitation erosion.

An object of the invention is to provide a fuel supply pump that suppresses cavitation erosion in the relief valve seat portion when the pressure is increased.

The aforementioned object is solved by the invention according to the independent claim <NUM>. Further preferred developments are described by the dependent claims. In particular, the relief valve mechanism includes a seat portion and a relief valve seated on the seat portion, and sets a set discharge pressure to <NUM> MPa or more. A seat angle of the seat portion is formed to be <NUM>° to <NUM>°, and a set valve opening pressure of the relief valve mechanism is set to <NUM> MPa or more than the set discharge pressure.

According to the invention, it is possible to provide a fuel supply pump that suppresses cavitation erosion in the relief valve seat portion when the pressure is increased. Objects, configurations, and effects besides the above description will be apparent through the explanation on the following embodiments.

Hereinafter, embodiments of the invention will be described using the drawings. In the following description, the vertical direction in the drawings may be specified and described, but this vertical direction does not mean the vertical direction when a fuel supply pump is mounted.

<FIG> is a configuration diagram illustrating an example of a fuel supply system including a fuel supply pump. A portion surrounded by a broken line indicates a pump body <NUM> of the fuel supply pump, and the mechanisms/components illustrated in the broken line are integrally assembled in the pump body <NUM> of the fuel supply pump.

The fuel of a fuel tank <NUM> is pumped up by a feed pump <NUM> on the basis of a signal from an engine control unit (ECU) <NUM>. The fuel is pressurized to an appropriate feed pressure to be passed through a suction pipe <NUM>, and sent to a low-pressure fuel suction port 10a of the fuel supply pump. The fuel passing from the low-pressure fuel suction port 10a through a suction joint <NUM> reaches a suction port 31b of an electromagnetic suction valve mechanism <NUM> of a capacity variation mechanism through a pressure pulsation damping mechanism <NUM> and a suction passage 10d.

The fuel flowing to the electromagnetic suction valve mechanism <NUM> passes through a suction valve <NUM> and flows into a pressurizing chamber <NUM>. A plunger <NUM> is applied with power of a reciprocating motion by a cam mechanism <NUM> (see <FIG>) of an engine. In a downward stroke of the plunger <NUM>, the fuel is sucked from the suction valve <NUM> by the reciprocating motion of the plunger <NUM>. The fuel is pressurized in an upward stroke. The pressurized fuel is sent through a discharge valve mechanism <NUM> to a common rail <NUM> on which a pressure sensor <NUM> is mounted.

On the common rail <NUM>, an injector <NUM> (so-called direct injector) for directly injecting fuel into a cylinder of an engine (not illustrated) and a pressure sensor <NUM> are mounted. The direct injectors <NUM> are mounted in accordance with the number of cylinders (cylinders) of the engine, open and close according to control signals from the ECU <NUM>, and inject fuel into the cylinders. The fuel supply pump (fuel supply pump) of this embodiment is applied to a so-called direct injection engine system in which the injector <NUM> directly injects fuel into a cylinder of the engine.

When an abnormally high pressure is generated in the common rail <NUM> due to a failure of the direct injector <NUM> or the like, and the differential pressure between the pressure of a fuel discharge port <NUM> of the fuel supply pump and the pressure of the pressurizing chamber <NUM> is equal to or more than the valve opening pressure of a relief valve mechanism <NUM>, a relief valve <NUM> opens. In this case, the abnormally high pressure fuel of the common rail <NUM> passes through the inside of the relief valve mechanism <NUM>, and is returned from a relief passage 200a to the pressurizing chamber <NUM>. This makes it possible to protect the common rail <NUM> (high-pressure pipe). This system is called a high pressure return system.

The fuel supply pump of this embodiment will be described with reference to <FIG>, <FIG> and <FIG>. <FIG> is a cross-sectional view illustrating a cross section of the fuel supply pump of this embodiment, which is parallel to the center axial direction of the plunger <NUM>. <FIG> is a horizontal cross-sectional view when viewed from above the fuel supply pump of this embodiment. <FIG> is a cross-sectional view of the fuel supply pump of this embodiment viewed from a direction different from <FIG>.

Although the suction joint <NUM> is provided on the side surface of the body in <FIG>, the invention is not limited to this, and is also applicable to a fuel supply pump in which the suction joint <NUM> is provided on the upper surface of a damper cover <NUM>. The suction joint <NUM> is connected to a low-pressure pipe for supplying fuel from the fuel tank <NUM> of the vehicle, and the fuel flowing from the low-pressure fuel suction port 10a of the suction joint <NUM> flows through a low-pressure flow path formed inside the pump body <NUM>. At the inlet of a fuel passage formed in the pump body <NUM>, a suction filter (not illustrated) press-fitted into the pump body <NUM> is provided, and the suction filter prevents foreign substances present between the fuel tank <NUM> and the low-pressure fuel suction port 10a from flowing into the fuel supply pump.

The fuel flows upward from the suction joint <NUM> in the axial direction of the plunger, and flows into the low-pressure fuel chamber <NUM> formed by an upper damper portion 10b and a lower damper portion 10c illustrated in <FIG>. The low-pressure fuel chamber <NUM> is formed by being covered by a damper cover <NUM> attached to the pump body <NUM>. The fuel whose pressure pulsation has been reduced by the pressure pulsation damping mechanism <NUM> in the low-pressure fuel chamber <NUM> reaches the suction port 31b of the electromagnetic suction valve mechanism <NUM> via the low-pressure fuel flow path 10d. The electromagnetic suction valve mechanism <NUM> is attached to a lateral hole formed in the pump body <NUM> and supplies a desired flow rate of fuel to the pressurizing chamber <NUM> through a pressurizing chamber inlet flow path 1a formed in the pump body <NUM>. An O-ring <NUM> is fitted to the pump body <NUM> to seal between a cylinder head <NUM> and the pump body <NUM>, and prevents engine oil from leaking out.

As illustrated in <FIG>, a cylinder <NUM> for guiding the reciprocating motion of the plunger <NUM> is attached to the pump body <NUM>. The cylinder <NUM> is fixed to the pump body <NUM> on the outer peripheral side by press fitting and swaging. The surface of the cylindrical press-fitting portion of the cylinder <NUM> seals so as not to leak the pressurized fuel from the gap between the cylinder <NUM> and the pump body <NUM> to the low-pressure side. The upper end surface of the cylinder <NUM> is brought into contact with the plane of the pump body <NUM> in the axial direction to form a double sealing structure in addition to the sealing of the cylindrical press-fitting portion between the pump body <NUM> and the cylinder <NUM>.

In the lower end of the plunger <NUM>, there is provided a tappet <NUM> which converts a rotation motion of a cam <NUM> mounted in a cam shaft of the internal combustion engine into an up-down motion, and transmits the up-down motion to the plunger <NUM>. The plunger <NUM> is tightly pressed to the tappet <NUM> by a spring <NUM> through a retainer <NUM>. With this configuration, the plunger <NUM> can make a reciprocating motion in the vertical direction according to the rotation motion of the cam <NUM>.

In addition, a plunger seal <NUM> held in the lower end portion of the inner periphery of a seal holder <NUM> is placed to come into slidable contact with the outer periphery of the plunger <NUM> in the lower portion in the drawing of the cylinder <NUM>. With this configuration, when the plunger <NUM> slides, the fuel in an auxiliary chamber 7a is sealed, and prevented from flowing into the internal combustion engine. At the same time, the plunger seal <NUM> prevents lubricating oil (also including the engine oil) for lubricating the sliding portion in the internal combustion engine from flowing into the pump body <NUM>.

As illustrated in <FIG>, the pump body <NUM> is formed with a lateral hole for mounting the electromagnetic suction valve mechanism <NUM>, a lateral hole for mounting the discharge valve mechanism <NUM> at the same position in the plunger axial direction, a lateral hole for further mounting the relief valve mechanism <NUM>, and a lateral hole for mounting a discharge joint 12c. The discharge joint 12c is inserted into the lateral hole of the pump body <NUM> and fixed by welding at a welding portion <NUM>. The fuel pressurized in the pressurizing chamber <NUM> via the electromagnetic suction valve mechanism <NUM> flows through a discharge passage 12b via the discharge valve mechanism <NUM>, and is discharged from the fuel discharge port <NUM> of the discharge joint 12c.

The discharge valve mechanism <NUM> (<FIG> and <FIG>) provided in the outlet side of the pressurizing chamber <NUM> is configured by a discharge valve seat 8a, a discharge valve 8b which comes into contact with or separates from the discharge valve seat 8a, a discharge valve spring 8c which biases the discharge valve 8b toward the discharge valve seat 8a, a discharge valve plug 8d, and a discharge valve stopper 8e which determines a stroke (moving distance) of the discharge valve 8b.

The discharge valve plug 8d and the pump body <NUM> are joined by the welding portion <NUM>, and this joining portion shuts off the inside space through which fuel flows and the outside. The discharge valve seat 8a is joined to the pump body <NUM> by a press-fitting portion <NUM>.

In a state where there is no differential pressure between the fuel pressure of the pressurizing chamber <NUM> and the fuel pressure of a discharge valve chamber 12a, the discharge valve 8b is tightly pressed to the discharge valve seat 8a by the urging force of the discharge valve spring 8c, and enters a valve-closed state. Only when the fuel pressure of the pressurizing chamber <NUM> becomes larger than that of the discharge valve chamber 12a, the discharge valve 8b is opened against the discharge valve spring 8c. Then, a high-pressure fuel in the pressurizing chamber <NUM> is discharged to the common rail <NUM> through the discharge valve chamber 12a, the fuel discharge passage 12b, and the fuel discharge port <NUM>. When being opened, the discharge valve 8b comes into contact with the discharge valve stopper 8e, and the stroke is restricted.

Therefore, the stroke of the discharge valve 8b is appropriately determined by the discharge valve stopper 8e. With this configuration, it is possible to prevent the fuel discharged at a high pressure to the discharge valve chamber 12a from flowing back into the pressurizing chamber <NUM> because of delay in the close of the discharge valve 8b due to excessively large stroke. Therefore, deterioration in efficiency of the fuel supply pump can be suppressed. In addition, when the discharge valve 8b repeatedly opens and closes, the discharge valve 8b is guided by the outer peripheral surface of the discharge valve stopper 8e such that the discharge valve 8b moves only in the stroke direction.

As described above, the pressurizing chamber <NUM> is configured by the pump body <NUM>, the electromagnetic suction valve mechanism <NUM>, the plunger <NUM>, the cylinder <NUM>, and the discharge valve mechanism <NUM>. As illustrated in <FIG> and <FIG>, the fuel supply pump according to this embodiment uses a mounting flange 1b provided on the pump body <NUM> to closely adhere to the plane of the cylinder head <NUM> of the internal combustion engine, and is fixed by a plurality of bolts (not illustrated).

The relief valve mechanism <NUM> includes a seat member <NUM>, the relief valve <NUM>, a relief valve holder <NUM>, a relief spring <NUM>, and a holder member <NUM>. The relief valve mechanism <NUM> is a valve that is configured to operate when an abnormally high pressure occurs due to some problem in the common rail <NUM> or a member near before. When the pressure in the common rail <NUM> or the member near before becomes high, the valve is opened to return the fuel to the pressurizing chamber <NUM>. Therefore, it is necessary to maintain the valve-closed state below a predetermined pressure, and has the very strong spring <NUM> to oppose high pressure.

The electromagnetic suction valve mechanism <NUM> will be described with reference to <FIG> is an enlarged cross-sectional view of the electromagnetic suction valve mechanism of this embodiment, illustrating a cross section parallel to the driving direction of the suction valve, and a cross-sectional view illustrating a state where the suction valve is opened.

In the non-energized state, the suction valve <NUM> is operated in the valve open direction by a strong rod urging spring <NUM>, so that it is a normally open type. If a control signal from the ECU <NUM> is applied to the electromagnetic suction valve mechanism <NUM>, the current flows to an electromagnetic coil <NUM> through a terminal <NUM>. When a current flows through the electromagnetic coil <NUM>, a movable core <NUM> is attracted in the valve closing direction on a magnetic attraction surface S by the magnetic attraction force of a magnetic core <NUM>. The rod urging spring <NUM> is disposed in a concave portion formed in the magnetic core <NUM> and urges a flange portion 35a. The flange portion 35a is engaged with the concave portion of the movable core <NUM> on the side opposite to the rod urging spring <NUM>.

The magnetic core <NUM> is configured to be in contact with a lid member <NUM> that covers the electromagnetic coil chamber in which the electromagnetic coil <NUM> is disposed. When the movable core <NUM> is attracted and moved by the magnetic core <NUM>, the movable core <NUM> is engaged with the flange portion 35a of a rod <NUM>, and the rod <NUM> moves together with the movable core <NUM> in the valve closing direction. Between the movable core <NUM> and the suction valve <NUM>, a valve closing urging spring <NUM> for urging the movable core <NUM> in the valve closing direction, and a rod guide member <NUM> for guiding the rod <NUM> in the opening and closing valve direction are arranged. The rod guide member <NUM> forms a spring seat 37b of the valve closing urging spring <NUM>. Further, the rod guide member <NUM> is provided with a fuel passage 37a, which allows the fuel to flow into and out of the space in which the movable core <NUM> is disposed.

The movable core <NUM>, the valve closing urging spring <NUM>, the rod <NUM> and the like are contained in an electromagnetic suction valve mechanism housing <NUM> fixed to the pump body <NUM>. Further, the magnetic core <NUM>, the rod urging spring <NUM>, the electromagnetic coil <NUM>, the rod guide member <NUM>, and the like are held in the electromagnetic suction valve mechanism housing <NUM>. The rod guide member <NUM> is mounted to the electromagnetic suction valve mechanism housing <NUM> on the side opposite to the magnetic core <NUM> and the electromagnetic coil <NUM>, and includes the suction valve <NUM>, a suction valve urging spring <NUM>, and a stopper <NUM>.

The suction valve <NUM>, the suction valve urging spring <NUM>, and the stopper <NUM> are provided on a side of the rod <NUM> opposite to the magnetic core <NUM>. The suction valve <NUM> is formed with a guide portion 30b projecting toward the pressurizing chamber <NUM> and guided by the suction valve urging spring <NUM>. The suction valve <NUM> moves in the valve open direction (the direction away from a valve seat 31a) by the gap of a valve body stroke 30e with the movement of the rod <NUM>, and becomes a valve open state. The fuel is supplied from a supply passage 10d to the pressurizing chamber <NUM>. The guide portion 30b stops moving by colliding with the stopper <NUM> fixed by being pressed into the housing (the rod guide member <NUM>) of the electromagnetic suction valve mechanism <NUM>. The rod <NUM> and the suction valve <NUM> are separate and independent structures. The suction valve <NUM> closes the flow path to the pressurizing chamber <NUM> by contacting the valve seat 31a of a valve seat member <NUM> disposed on the suction side, and opens the flow path to the pressurizing chamber <NUM> by separating from the valve seat 31a.

When the plunger <NUM> moves in the direction (lower direction) of the cam <NUM> and enters a suction stroke state while the cam <NUM> of <FIG> rotates, the volume of the pressurizing chamber <NUM> is increased and the fuel pressure in the pressurizing chamber <NUM> is lowered. When the electromagnetic coil <NUM> is de-energized during this suction stroke, the sum of the urging force of the rod urging spring <NUM> and the fluid force due to the pressure in the suction passage 10d becomes larger than the fluid force due to the fuel pressure in the pressurizing chamber <NUM>. Thus, the suction valve <NUM> is urged by the rod <NUM> in the valve open direction to be in the valve open state.

When the plunger <NUM> reaches the bottom dead center and completes the suction stroke, the plunger <NUM> starts to move upward. Herein, the electromagnetic coil <NUM> keeps a non-energized state, and a magnetic urging force does not operate. The volume of the pressurizing chamber <NUM> is reduced according to the compression movement of the plunger <NUM>. However, in this state, the fuel once sucked into the pressurizing chamber <NUM> returns to the suction passage 10d through the opening of the suction'valve <NUM> which enters the valve open state again. Therefore, the pressure of the pressurizing chamber <NUM> is not increased. This stroke is called a returning stroke.

Thereafter, by turning on the energization of the electromagnetic coil <NUM> at a desired timing, the magnetic attraction force is generated as described above, so that the rod <NUM> moves in the valve closing direction together with the movable core <NUM>, and a tip portion of the rod <NUM> is separated from the suction valve <NUM>. In this state, the suction valve <NUM> is a check valve that opens and closes according to the differential pressure, and is closed by the urging force of the suction valve urging spring <NUM>. After the suction valve <NUM> is closed, the plunger <NUM> is raised, so that the volume of the pressurizing chamber <NUM> is reduced, and the fuel is pressurized. This is called a compression stroke. When the fuel in the pressurizing chamber <NUM> is pressurized and the pressure of the fuel exceeds the sum of the fuel pressure in the discharge valve chamber 12a and the urging force of the discharge valve spring 8c, the discharge valve 8b opens to discharge the fuel.

The amount of the discharging high-pressure fuel can be controlled by controlling timing for energizing the electromagnetic coil <NUM> of the electromagnetic suction valve mechanism <NUM>. If the timing for energizing the electromagnetic coil <NUM> is set to be advanced, the ratio of the returning stroke in the compression stroke becomes small, and the ratio of the discharge stroke becomes large. In other words, the fuel returning to the suction passage 10d becomes less, and the high-pressure fuel discharged to the common rail <NUM> becomes large. On the other hand, if the energizing timing is set to be delayed, the ratio of the returning stroke in the compression stroke becomes large, and the ratio of the discharge stroke becomes small. In other words, the fuel returning to the suction passage 10d becomes large, and the high-pressure fuel discharged to the common rail <NUM> becomes less. The timing for energizing the electromagnetic coil <NUM> is controlled by a command from the ECU <NUM>.

As described above, it is possible to control the amount of high-pressure fuel to be discharged as much as the internal combustion engine requires by controlling the timing for energizing the electromagnetic coil <NUM>.

In the low-pressure fuel chamber <NUM>, the pressure pulsation damping mechanism <NUM> is provided to reduce the propagation of the pressure pulsation generated in the fuel supply pump to a fuel pipe <NUM>. Above and below the pressure pulsation damping mechanism <NUM>, an upper damper portion 10b and the lower damper portion 10c are provided at intervals. In a case where the fuel flown into the pressurizing chamber <NUM> returns to the suction passage 10d through the suction valve <NUM> which enters the valve open state again to control the volume, the pressure pulsation is generated in the low-pressure fuel chamber <NUM> by the fuel returned to the suction passage 10d. However, the pressure pulsation damping mechanism <NUM> provided in the low-pressure fuel chamber <NUM> is formed by metal diaphragm damper formed by bonding two disk-like metal plates of a corrugate shape at the outer periphery and with an inert gas such as argon injected therein, so that the pressure pulsation is absorbed and reduced as the metal damper expands and contracts. Reference numeral 9a denotes a mounting bracket for fixing the metal damper to the inner peripheral portion of the pump body <NUM>, and is provided on the fuel passage. The support part with the damper is not a whole circumference but a part, so that the fluid can freely flow between the front and back of the mounting bracket 9a.

The plunger <NUM> includes a large diameter portion 2a and a small diameter portion 2b. The volume of the auxiliary chamber 7a is increased or decreased according to the reciprocating motion of the plunger <NUM>. The auxiliary chamber 7a is connected to the low-pressure fuel chamber <NUM> by a fuel passage 10e (see <FIG>). The fuel flows from the auxiliary chamber 7a to the low-pressure fuel chamber <NUM> when the plunger <NUM> descends. The fuel flows from the low-pressure fuel chamber <NUM> to the auxiliary chamber 7a when the plunger ascends.

With this configuration, the fuel flow rate to the inside and outside of the pump in the suction stroke or the returning stroke of the pump can be reduced, and the pressure pulsation generated in the fuel supply pump is reduced.

Further, the operation of the relief valve mechanism will be described in detail. As illustrated in <FIG>, the relief valve mechanism <NUM> includes the seat member <NUM>, the relief valve <NUM>, the relief valve holder <NUM>, the relief spring <NUM>, and a relief spring stopper <NUM>.

The relief valve <NUM>, the relief valve holder <NUM>, and the relief spring <NUM> are sequentially inserted into the seat member <NUM>, and the relief spring stopper <NUM> is fixed by press fitting or the like. The pressing force of the relief spring <NUM> is defined by the position of the relief spring stopper <NUM>. The set valve opening pressure of the relief valve <NUM> is set to a prescribed value by the pressing force of the relief spring <NUM>. The unitized relief valve mechanism <NUM> is fixed to the pump body <NUM> by press fitting or the like as illustrated in <FIG>. Further, although the unitized relief valve mechanism <NUM> is illustrated in <FIG>, the invention is not limited to this.

The fuel supply pump needs to pressurize the fuel to a very high pressure of several MPa to several tens of MPa. In this embodiment, the maximum discharge pressure (for example, <NUM> MPa) that can be discharged by the fuel supply pump in normal operation is defined as the set discharge pressure. The set valve opening pressure of the relief valve <NUM> needs to be set to be equal to or higher than the set discharge pressure. This is because if the set valve opening pressure is set below the set discharge pressure, the relief valve <NUM> will open even if the fuel is normally pressurized by the fuel supply pump. This malfunction of the relief valve <NUM> may cause cavitation erosion near the seat portion of the seat member <NUM>, decrease in discharge amount, decrease in energy efficiency, and the like. Further, even when the set valve opening pressure is set to be equal to or higher than the set discharge pressure, if the difference is small, the contact surface pressure of the seat portion 201a decreases, fuel leakage may occur, and cavitation erosion may occur. The degree of cavitation erosion becomes more serious as the fuel pressure increases, so this is a problem that became particularly apparent when the set discharge pressure is set high to <NUM> MPa compared to the related art where the set discharge pressure is set less than <NUM> MPa.

From the above, it is necessary to set the set valve opening pressure of the relief valve <NUM> to be higher than the set discharge pressure by a certain set value. However, this leads to an increase in the maximum pressure of the common rail <NUM> when an abnormally high pressure is generated and the relief valve <NUM> opens to release the fuel. In order to suppress the maximum pressure of the common rail <NUM>, it is an important issue to suppress the increase in valve opening pressure to the necessary minimum. That is, in this embodiment, it is an object to simultaneously reduce the maximum pressure of the common rail <NUM> when opening the abnormally high pressure while suppressing the cavitation erosion in the seat portion of the relief valve <NUM> at the time of high pressure (for example, <NUM> MPa).

This embodiment for solving these problems will be described with reference to <FIG>. The upper part of <FIG> illustrates a cross-sectional view of the relief valve mechanism <NUM> of this embodiment, and the lower part illustrates an enlarged cross-sectional view of the vicinity of a seat portion 201a surrounded by a frame line. The ball-shaped relief valve <NUM> and the conical slope formed on the seat member <NUM> contact each other to form a linear seat portion 201a. Here, the angle between the conical slopes is defined as a seat angle 201b. The lower side in the drawing is the upstream side across the seat portion 201a, and the set discharge pressure acts in the direction to open the relief valve <NUM>. Against this, the valve opening pressure is set by the load of the relief spring <NUM> from the downstream side. The relief valve <NUM> is pressed against the seat member <NUM> due to the difference between the valve opening pressure and the set discharge pressure, and a contact surface pressure is generated in the seat portion 201a.

If the difference between the two is not sufficient, the contact surface pressure is also insufficient, which may cause fuel leakage and cavitation erosion.

<FIG> illustrates a contact surface pressure generated in the seat portion 201a with respect to the difference between the valve opening pressure and the set discharge pressure (called a valve opening pressure margin). As the valve opening pressure margin increases, the seat contact surface pressure also increases. If the valve opening pressure margin is the same, the contact surface pressure decreases as the seat angle 201b increases. This is because, of the axial force pressing the relief valve <NUM> against the seat member <NUM>, the normal force acting on the conical slope becomes smaller as the seat angle becomes larger. With respect to the contact surface pressure determined in this manner, a required surface pressure for preventing fuel leakage is determined by the fuel pressure for sealing, that is, the set discharge pressure, and the required surface pressure becomes larger as the set discharge pressure increases.

Therefore, in this embodiment, there is provided the relief valve mechanism <NUM> which includes the seat portion 201a and the relief valve <NUM> seated on the seat portion 201a. In the method of manufacturing the fuel supply pump in which the set valve opening pressure of the relief valve mechanism <NUM> is set to be higher than the set discharge pressure by a set value, the relief valve mechanism <NUM> is manufactured such that the set value becomes larger as the seat angle 201b of the seat portion 201a increases when the set discharge pressure is the same. That is, when manufacturing a fuel supply pump with a set discharge pressure of <NUM> MPa, the difference (set value) between the set valve opening pressure and the set discharge pressure is set to be high as the seat angle 201b of the seat portion 201a increases. Further, when the seat angle 201b of the seat portion 201a is the same, the relief valve mechanism <NUM> is manufactured such that the set value becomes larger as the set discharge pressure increases. Further, this set value is synonymous with the above-mentioned valve opening pressure margin.

In this way, by setting the set valve opening pressure according to the seat angle 201b and the set discharge pressure, it is expected that fuel leakage is prevented by maintaining the contact surface pressure of the seat portion 201a, and as a result, cavitation erosion is suppressed. In addition, the set valve opening pressure can be reduced as the seat angle 201b is reduced and the set discharge pressure is lowered, and the maximum pressure of the common rail <NUM> can be expected to be reduced when the abnormally high pressure is released.

<FIG> illustrates a range in which the seat angle 201b and the valve opening pressure margin are satisfied, taking the case where the set discharge pressure is <NUM> MPa as an example. It has been found that cavitation erosion may occur particularly when the set discharge pressure is <NUM> MPa. Here, a case will be described in which the valve opening pressure margin needs to be kept within <NUM> MPa due to the restriction of the maximum pressure determined by the withstand pressure allowable value of each part. In this case, as illustrated in <FIG>, it is necessary to reduce the seat angle 201b to about <NUM>° in order to maintain the required surface pressure for sealing the fuel pressurized to <NUM> MPa.

That is, in this embodiment, the fuel supply pump includes the relief valve mechanism <NUM> which includes the seat portion 201a and the relief valve <NUM> seated on the seat portion 201a and sets the set discharge pressure to <NUM> MPa with the seat angle 201b as a median value. In the fuel supply pump, the seat angle 201b of the seat portion 201a is formed to be <NUM>° to <NUM>°, and the set valve opening pressure of the relief valve mechanism <NUM> is <NUM> MPa or larger than the set discharge pressure.

By doing this, even in a case where the set discharge pressure is <NUM> MPa in which cavitation erosion starts to become particularly severe due to high pressure, it can be expected that the fuel leakage is prevented by maintaining the contact surface pressure of the seat portion 201a, and eventually cavitation erosion is prevented.

A second embodiment of the invention will be described using <FIG> illustrates changes in the pressure of the pressurizing chamber <NUM> and the pressure of the discharge port <NUM> with the passage of time. Since the fuel supply pump periodically repeats discharge and suction, the internal pressure pulsates with respect to the set discharge pressure, especially at high rotation speeds. Therefore, it is possible to prevent cavitation erosion more reliably by adding the pulsating component to the set discharge pressure used in the first embodiment to set the valve opening pressure margin. Next, the difference between the pressure behavior of each part and the relief valve system will be described. In the discharge process, the pressure of the pressurizing chamber <NUM> is almost equal to the pressure of the discharge port <NUM>, and in the suction process, the pressure of the pressurizing chamber <NUM> decreases, but the pressure of the discharge port <NUM> maintains the same pressure as the set discharge pressure.

Here, in the case of the high pressure return system, even if the pressure of the discharge port <NUM> acts on the upstream side of the relief valve <NUM> in the discharge process, the pressure of the pressurizing chamber <NUM> acts on the downstream side so as to oppose it, so that it is possible to maintain the seat contact surface pressure. On the other hand, since the pressure of the pressurizing chamber <NUM> is lowered in the suction process, the seat contact surface pressure is reduced most when the pressure of the discharge port <NUM> is maximized in the suction process.

Therefore, it is desirable that the seat surface pressure is maintained at or above the allowable surface pressure in this state.

On the other hand, in the case of a low pressure return system, which is not part of the invention, the pressure of the pressurizing chamber <NUM> does not act on the downstream side of the relief valve <NUM>, so that the seat contact surface pressure is reduced most when the pressure of the discharge port <NUM> becomes maximum in the discharge process. Therefore, it is desirable that the seat surface pressure is maintained at or above the allowable surface pressure in this state. From the above, in the case of the high pressure return system, it is desirable to define the difference between the maximum pressure value of the discharge port <NUM> and the set valve opening pressure in the suction process as the valve opening pressure margin. Further, in the case of the low pressure return system, it is desirable to define the difference between the maximum pressure value of the discharge port <NUM> and the set valve opening pressure in the discharge process as the valve opening pressure margin.

That is, the fuel supply pump of this embodiment includes the pressurizing chamber <NUM> for pressurizing the fuel. In a case where the relief valve mechanism <NUM> is configured to open the relief valve when the pressure difference between the pressure on the discharge side of the pressurizing chamber <NUM> (the pressure of the discharge port <NUM>) and the pressure of the pressurizing chamber <NUM> becomes larger than the set valve opening pressure (in the case of the high pressure return system), it is desirable to set the set discharge pressure as the maximum pressure value on the discharge side of the pressurizing chamber <NUM> in the suction stroke. On the other hand, in a case where the relief valve mechanism is configured to open the relief valve when the pressure difference between the pressure on the discharge side of the pressurizing chamber <NUM> and the pressure on the suction side of the pressurizing chamber <NUM> becomes larger than the set valve opening pressure (in the case of the low pressure return system, which is not part of the invention), it is desirable to set the set discharge pressure as the maximum pressure value on the discharge side of the pressurizing chamber <NUM> in the compression stroke. The suction side of the pressurizing chamber <NUM> in the case of the low pressure return system may be a low pressure space such as the low-pressure fuel chamber <NUM> formed by the lower damper portion 10c, the auxiliary chamber 7a, or a space communicating with the suction port 31b of the electromagnetic suction valve mechanism <NUM> in <FIG>.

In other words, in the case of the high pressure return system, in the method of manufacturing the fuel supply pump of this embodiment, the relief valve mechanism <NUM> is configured to open the relief valve when the pressure difference between the pressure on the discharge side of the pressurizing chamber <NUM> and the pressure of the pressurizing chamber <NUM> becomes larger than the set valve opening pressure, and the set discharge pressure is set as the maximum pressure value on the discharge side of the pressurizing chamber <NUM> in the suction stroke. Further, in the case of the low pressure return system, which is not part of the invention, in the method of manufacturing the fuel supply pump of this embodiment, the relief valve mechanism <NUM> is configured to open the relief valve when the pressure difference between the pressure on the discharge side of the pressurizing chamber <NUM> and the pressure on the suction side of the pressurizing chamber <NUM> becomes larger than the set valve opening pressure, and the set discharge pressure is set as the maximum pressure value on the discharge side of the pressurizing chamber <NUM> in the compression stroke.

By doing so, it can be expected that fuel leakage is prevented by maintaining the contact surface pressure of the seat portion 201a even when the pressure acting on the relief valve <NUM> pulsates with respect to the set discharge pressure, and as a result, cavitation erosion is more reliably prevented.

As described above, the fuel supply pump of this embodiment includes the relief valve mechanism <NUM> described above. The relief valve mechanism <NUM> is configured to return fuel to the pressurizing chamber <NUM> or the low-pressure passage (the low-pressure fuel chamber <NUM>, the suction passage 10d, or the like) in a case where the fuel of the discharge port <NUM> on the downstream side of the discharge valve mechanism <NUM> exceeds a set pressure.

As described above, in addition to the relief valve mechanism <NUM>, this embodiment can be applied to functional components for satisfying the performance of the fuel supply pump, for example, the electromagnetic suction valve mechanism <NUM> and the discharge valve mechanism <NUM>, and also applicable even other functional components.

Claim 1:
A fuel supply pump, comprising:
a pressurizing chamber (<NUM>) that pressurizes fuel,
a relief valve mechanism (<NUM>) that includes a seat portion (201a) and a relief valve (<NUM>) seated on the seat portion (201a), characterized in that a set discharge pressure of the fuel supply pump is set to <NUM> MPa or more,
a seat angle (201b) being an angle between conical slopes of the seat portion (201a) is formed to be <NUM>° to <NUM>°, and a set valve opening pressure of the relief valve mechanism (<NUM>) is set to <NUM> MPa or larger than the set discharge pressure,
wherein the relief valve mechanism (<NUM>) is configured to open the relief valve (<NUM>) when a pressure difference between a pressure on a discharge side of the pressurizing chamber (<NUM>) and a pressure of the pressurizing chamber (<NUM>) becomes larger than the set valve opening pressure, and
wherein the set discharge pressure is set as a maximum pressure value on the discharge side of the pressurizing chamber (<NUM>) in a suction stroke.