JP3800932B2 - High pressure fuel pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-pressure fuel pump that supplies fuel to a fuel injection valve of an automobile engine at a high pressure.
[0002]
[Prior art]
A conventional high-pressure fuel pump is described in, for example, Japanese Patent Application Laid-Open No. 2-176158. This high-pressure fuel pump operates along the cam profile of the cam, sucks fuel into the pressurized chamber, and is operated by a plunger that discharges it to the engine and a solenoid, and an intake solenoid valve that supplies fuel into the pressurized chamber And. This solenoid valve is operated by a solenoid so that it can be used when an automobile engine rotates at high speed.
[0003]
In this conventional high-pressure fuel pump, the maximum pressure point of the suction and discharge strokes (discharge strokes) comes to the first half during one rotation of the cam profile. This increases the fuel pressure in the pressurization chamber in a short time and pressurizes the pressure to a level that can keep the solenoid valve closed, thereby making it possible to cope with high-speed driving of the vehicle and shorten the time until the solenoid valve closes. However, a large discharge amount of high-pressure fuel can be discharged.
[0004]
[Problems to be solved by the invention]
In this type of fuel pump, as a means for opening and closing a suction valve that sucks and discharges fuel, a type operated by a solenoid as in the above-described prior art, and a valve pressed against a valve seat by a spring, There is a type that opens and closes the valve by pressure difference.
[0005]
Of these types, especially in the case of a valve using a spring, when the engine of a vehicle equipped with a fuel pump rotates at high speed, the rotational speed of the cam does not match the opening / closing speed of the suction valve, and the flow reverses from the suction valve side. There is a problem that the amount of fuel increases. In this case, it is conceivable to enlarge the pump in order to ensure a discharge amount that is equal to or greater than the reverse flow rate of the fuel. However, when the pump becomes larger, the load on the engine that drives the pump increases correspondingly, and fuel consumption decreases. There's a problem.
[0006]
By the way, the cam profile of the above-described conventional high-pressure fuel pump is effective when combined with a solenoid operated valve, a so-called electromagnetic valve, but the same effect is obtained when combined with a valve using a spring. The possibility of having
[0007]
That is, the above-described conventional fuel pump using a solenoid valve can be closed at an arbitrary timing by inputting a signal to the solenoid valve. In total, when the cam speed is maximum, the valve operation cannot follow the cam speed, and the reverse flow rate of the fuel increases.
[0008]
An object of the present invention is to provide a high-pressure fuel pump that can reduce the reverse flow rate of fuel, and that can produce low vibration and low noise without the appearance of higher-order vibration components .
[0009]
[Means for Solving the Problems]
The object is to provide a pressurizing chamber that communicates with a fuel suction passage and a discharge passage, a plunger that reciprocates in the pressurization chamber by the shape of a rotating cam, a suction valve that opens and closes the suction passage, and the discharge passage. In the high-pressure fuel pump having a discharge valve that opens and closes the cam, the cam has a cam acceleration that suppresses the cam acceleration from the bottom dead center in the discharge stroke from the bottom dead center to the top dead center to a small positive value. A first cam portion, and a second cam portion that gradually increases after the first cam portion and then gradually decreases and then decreases to a negative acceleration. This is achieved by providing a cam profile in which the first-order cam angle derivative of the cam acceleration is substantially zero .
[0010]
A pressurizing chamber communicating with the fuel suction passage and the discharge passage; a plunger that reciprocates in the pressurization chamber by the shape of a rotating cam; a suction valve that opens and closes the suction passage; and the discharge passage. A high-pressure fuel pump including a discharge valve that includes an elastic member that presses the plunger against the urging force of the cam, and the cam is in a discharge stroke from the bottom dead center to the top dead center. The first cam portion in which the cam acceleration from the bottom dead center is suppressed to a small positive value, and the cam acceleration is greatly increased following the first cam portion, and then gradually decreased to lower the negative acceleration. And the negative cam acceleration up to the top dead center following the second cam portion is substantially the same as the limit acceleration at which the cam and the plunger are not separated even at the maximum reciprocating frequency of the plunger. The first cam angle derivative of the cam acceleration at the bottom dead center and the top dead center is substantially 0, and the plunger has an intake stroke from the top dead center to the bottom dead center. This is achieved by providing a cam profile having an acceleration curve symmetrical to the cam acceleration and top dead center of the discharge stroke .
[0012]
A pressurizing chamber communicating with the fuel suction passage and the discharge passage; a plunger that reciprocates in the pressurization chamber by the shape of a rotating cam; a suction valve that opens and closes the suction passage; and the discharge passage. A high-pressure fuel pump including a discharge valve that includes an elastic member that presses the plunger against the urging force of the cam, and the cam is in a discharge stroke from the bottom dead center to the top dead center. A first cam portion in which the cam acceleration from the bottom dead center is set to a substantially constant positive value; and a second cam portion that gradually decreases the cam acceleration and monotonously decreases to a negative acceleration following the first cam portion; Furthermore, the negative cam acceleration up to the top dead center following the second cam portion is set to a substantially constant negative value, and the cam and the plunger are moved at the negative acceleration even at the maximum reciprocating frequency of the plunger. As long as they are not separated A third cam portion having substantially the same value as the acceleration of the stroke, and in the intake stroke from the top dead center to the bottom dead center, the acceleration acceleration curve symmetrical to the cam acceleration and the top dead center of the discharge stroke is provided. This is achieved by having a cam profile having .
[0013]
Further, the maximum peak position of the cam speed may be set between approximately 1/3 and 1/2 of the discharge stroke section .
[0014]
The intake valve is an automatic valve that opens and closes depending on the fuel pressure in the pressurizing chamber, and may be any valve that closes when the fuel pressure in the pressurizing chamber increases during the discharge stroke .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the high-pressure fuel pump uses a valve that opens and closes in synchronism with the reciprocating motion of the plunger, a so-called check valve. Since this valve cannot be closed at an arbitrary timing, there is a slight delay in closing the plunger. For example, the intake valve does not close immediately after the plunger enters the discharge stroke, and the fuel pressurized by the plunger during this time flows back to the outside of the pressurization chamber through the intake valve. The discharge amount of the pump is reduced by the amount of the reverse flow, and the volumetric efficiency particularly at high rotation tends to be reduced.
[0016]
Therefore, simply using the above-described conventional cam for the high-pressure fuel pump of the present invention increases the cam speed in the ineffective zone until the suction valve closes, so the reverse flow rate to the suction side increases and the discharge amount decreases. There is a risk of inviting.
[0017]
First, a general high-pressure fuel pump will be described with reference to the drawings.
[0018]
FIG. 1A is a longitudinal sectional view showing a high-pressure fuel pump. FIG. 1B is a partial cross-sectional view of the engine showing a state in which the high-pressure fuel pump is attached to the engine. FIG. 2 is a configuration diagram showing an engine fuel supply apparatus using a high-pressure fuel pump.
[0019]
In FIG. 1 (a), a fuel suction passage 10, a discharge passage 11, and a pressurizing chamber 12 are formed in the pump body 1. In the pressurizing chamber 12, a plunger 2 that is a pressurizing member is slidably held by a cam 100. Reference numeral 3 denotes a lifter that holds the tip of the spring 4 and the plunger 2. The lifter 3 is always in contact with the cam profile of the cam 100. Reference numeral 20 denotes a seal member for sealing the plunger 2 and the inside of the pressurizing chamber 12 of the pump body 1. The suction passage 10 and the discharge passage 11 are provided with a suction valve 5 and a discharge valve 6, which are pressed against the valve seat by springs 5a and 6a, respectively, and serve as check valves that restrict the direction of fuel flow. The pump body 1 composed of these components is collectively referred to as a high-pressure fuel pump 101.
[0020]
In FIG.1 (b), 73 is an engine cover, and accommodates a piston, an engine cam, etc. inside. Reference numeral 72 denotes an engine cam shaft, to which the cam 100 is directly connected. A high pressure fuel pump 101 is attached to a part of the engine cover 73.
[0021]
Thus, the rotation of the engine cam shaft 72 causes the cam 100 to rotate, and the plunger 2 in the high-pressure fuel pump 101 moves up and down. Such a high-pressure fuel pump is called a single-cylinder plunger pump.
[0022]
In FIG. 2, the fuel indicated by the arrow is regulated to a constant pressure by the low-pressure pressure regulator 52 and guided from the tank 50 to the fuel inlet of the high-pressure fuel pump 101 via the low-pressure pump 51 and the low-pressure pipe 9. The The fuel sucked into the high-pressure fuel pump 101 is pressurized by the rotation of the cam 100 provided in the engine 71 and is pumped to the common rail 53 from the fuel discharge port. The fuel pressure in the common rail 53 is held at a substantially constant pressure by the high pressure regulator 55. The injectors 54 are attached to the common rail 53 according to the number of cylinders of the engine. The injector 54 injects fuel into the engine 71 by a signal from an engine control unit (ECU). A pressure sensor 56 detects the pressure of the common rail 53, and the ECU controls the opening and closing of the intake valve according to the pressure.
[0023]
The operation of the high-pressure fuel pump configured as above will be described.
[0024]
In FIG. 1A, since the lifter 3 provided at the lower end of the plunger 2 is pressed against the cam 100 by a spring 4, the plunger 2 has a cam profile of the cam 100 rotated by an engine camshaft ( The volume in the pressurizing chamber 12 is changed by reciprocating following the outer shape.
[0025]
The intake valve 5 and the discharge valve 6 are both automatic valves that open and close in synchronism with the reciprocating movement of the plunger 2. During the intake stroke, the discharge valve 6 is closed due to a decrease in fuel pressure in the pressurizing chamber 12. The suction valve 5 is opened and fuel is sucked into the pressurizing chamber 12. During the discharge stroke, the suction valve 5 is closed by the increase of the fuel pressure in the pressurizing chamber 12, the discharge valve 6 is opened, and the fuel is pumped to the common rail 53 shown in FIG.
[0026]
The single cylinder plunger pump described above has the advantages of simple structure and low cost. However, since the intake valve 5 and the discharge valve 6 are held only by the pressing force of the spring 4, both the valve opening and closing are delayed. Both cause a decrease in the discharge rate.
[0027]
That is, there is a delay corresponding to the movement distance associated with the opening and closing of the valve. For example, even if the plunger 2 enters the discharge stroke from the suction stroke, the suction valve 5 is not closed immediately, and the discharge flow rate is reduced by the amount of fuel flowing back from the pressurizing chamber 12 to the suction passage 10 side. In particular, when the vehicle is traveling at high speed, the cam rotates at a high speed, so that the vertical movement cycle of the plunger is shortened, the influence of the valve closing delay becomes more prominent, and the volumetric efficiency is lowered.
[0028]
If the volumetric efficiency is low, it is necessary to increase the displacement volume of the pump itself in order to secure the maximum discharge amount, which increases the driving torque and deteriorates the fuel consumption of the engine. Therefore, improvement in volumetric efficiency at high rotation is one of the important issues for a single cylinder plunger pump.
[0029]
Therefore, in the present invention, while the suction valve 5 is still open immediately after the start of the discharge stroke, the upward flow rate of the plunger 2 is suppressed to reduce the flow rate of backflow from the suction valve 5, and the plunger 2 is lifted after the suction valve 5 is closed. The speed is increased.
[0030]
Therefore, in the present invention, the cam profile of the cam 100 is such that the maximum peak of the cam speed is between approximately 1/3 and 1/2 of the discharge stroke section as shown in FIG.
[0031]
FIG. 3 is a view showing an example of a triple cam in which the plunger is reciprocated three times by one rotation of the cam provided with the present invention.
[0032]
In FIG. 3, assuming that the bottom dead center of the plunger 2 is a cam rotation angle of 0 °, the maximum peak of the cam speed is at a position of about 20 ° to 30 ° in this case and about 30 ° to 45 ° in the case of a double cam. To enter. As a result, the rise of the cam speed is moderately suppressed, so the theoretical flow rate (= plunger cross-sectional area x speed) in the section where the intake valve closes late and becomes invalid discharge decreases, and the section where effective discharge occurs after the discharge valve is opened The theoretical flow rate at will increase. In addition, since the fuel pressure increase speed is sufficiently secured, the discharge valve can be quickly opened, and the section where the invalid discharge is performed can be sufficiently shortened. Accordingly, the discharge flow rate is increased, and the volumetric efficiency can be improved particularly at high rotation.
[0033]
Hereinafter, the present invention will be described in more detail with reference to FIGS. 4, 5, and 6.
[0034]
FIG. 4 shows a comparison between the cam profile shown in FIG. 3 and other cam profiles.
[0035]
In FIG. 4, the thick line indicates the cam A of the present invention, the thin line indicates the cam B whose speed peak is 1/3 of the discharge stroke interval, the dotted line indicates a sine wave cam, and the speed peak is The cam C is shown as a half position of the discharge stroke section.
[0036]
Since the sine wave of the cam C has a large absolute value of the negative cam acceleration near the top dead center, the inertial force of the reciprocating motion part including the plunger 2 also increases, and the cam 100 is lifted between the cam 100 and the lifter 3 at high rotation. As a result, the inertial force is larger than the contact force, and jumping occurs to cause the two to separate.
[0037]
Jumping should be avoided because it causes noise generation and deterioration of durability, and the cam C is practically unusable. In order to avoid jumping using the cam C, it is necessary to increase the spring force, which causes adverse effects such as a decrease in durability due to an increase in Hertz stress on the contact surface and a deterioration in fuel consumption due to an increase in driving torque.
[0038]
Next, the discharge flow rate characteristics of the pump when the cams A and B are used are shown in FIG.
[0039]
In FIG. 5, the horizontal axis represents the pump rotation speed, and the vertical axis represents the time-averaged discharge flow rate. As described above, the single-cylinder plunger pump shows a tendency that the volumetric efficiency decreases as the rotation speed increases, and the actual discharge flow rate decreases with respect to the theoretical flow rate. There is little way to fall, and high volumetric efficiency can be maintained up to high rotation. The reason for this will be described with reference to FIG.
[0040]
In FIG. 6, the time history waveform of each part of the pump at the time of high rotation is shown. The case of cam A is indicated by a thick line, and the case of cam B is indicated by a thin line. As shown in the drawing, the suction valve 5 is still open even when the cam enters the discharge stroke from the suction stroke, and the flow rate of the pressure applied by the plunger 2 during this time passes through the suction valve 5 to the suction passage 10 side. Backflow. For this reason, the discharge flow rate decreases.
[0041]
Furthermore, there is a delay from when the intake valve 5 is closed to when the discharge valve 6 is opened, and the sum of both delays is an ineffective section that does not contribute to discharge. At the time of high rotation, since the time per stroke becomes short, this invalid section increases relatively, and the volumetric efficiency decreases. The reason for the delay in closing the suction valve 5 is that the pressure in the pressurizing chamber 12 does not drop immediately after the plunger 2 starts to move down, and it takes time to move the suction valve itself from open to closed. Because. The reason for the delay in opening the discharge valve 6 is that it takes time for the pressurizing chamber pressure to rise to the pressure in the discharge passage 11 downstream of the discharge valve.
[0042]
Here, since the cam A of the present invention has a speed peak behind the cam B, the speed in the invalid section is kept low. For this reason, the theoretical flow rate in the invalid interval proportional to the speed, that is, the invalid flow rate that flows backward to the suction side decreases, and conversely, the theoretical flow rate increases in the interval in which effective discharge occurs after the discharge valve is opened. The discharge flow rate of the cam A is increased by the difference in the invalid flow rate. When the ineffective section is short and the rotation is low, the difference between the two is small. However, when the ineffective section is high and the rotation is high, the difference gradually increases, resulting in a difference in flow characteristics as shown in FIG.
[0043]
From the above, it can be seen that, in order to improve the volumetric efficiency, it is effective to place the peak position of the cam speed as far back as possible and keep the cam speed in the invalid section low.
[0044]
However, if the peak position is set too far, the increase in the pressure in the pressurizing chamber after closing the intake valve is delayed, and in particular, the opening delay of the discharge valve is increased. As a result, the invalid section itself becomes long, and conversely, the discharge flow rate decreases.
[0045]
That is, the peak position of the cam speed cannot be too early or too late, and the range of about 1/3 to 1/2 of the discharge stroke section is most appropriate. When the speed peak comes before the 1/3 position, the rise of the cam speed becomes too fast like the cam B, so that the invalid flow rate increases and the discharge flow rate decreases. On the other hand, when it is behind 1/2, the increase in fuel pressure in the pressurized chamber is delayed, the delay in closing the intake valve, the delay in opening the discharge valve is increased, and the ineffective section itself is lengthened, which also leads to a decrease in the discharge flow rate. . 1/3 to 1/2 is an appropriate range for achieving both reduction of the ineffective flow rate and shortening of the ineffective section.
[0046]
Incidentally, since the cam speed is obtained by integrating the cam acceleration, it is necessary to appropriately set the cam acceleration in order to operate the cam speed. As described above, the sine wave cam in FIG. 4 was inappropriate in that jumping occurred, but taking a large absolute value of the negative cam acceleration near the top dead center like the sine wave cam is as follows. It is difficult from a point.
[0047]
First, in the vicinity of the top dead center, the force of the return spring 4 of the plunger is the strongest, so the Hertz stress acting on the cam surface is also increased. In order to reduce the Hertz stress, either the spring force is lowered or the cam radius near the top dead center is increased. First, in order to reduce the spring force, the negative absolute value of the cam acceleration is decreased. Thus, it is necessary to reduce the inertial force of the reciprocating portion so that the cam 100 and the lifter 3 do not separate even with a weak spring force. In order to increase the radius of curvature, it is also necessary to decrease the negative absolute value of the cam acceleration or increase the cam base circle. Of these, the base circle cannot be made very large from the viewpoint of miniaturization. Therefore, in order to ensure the durability by keeping the Hertz stress within a certain tolerance, the negative absolute value of the cam acceleration near top dead center must be reduced. There is no choice but to do.
[0048]
For this reason, it becomes difficult to decelerate the cam speed in a short section, and the deceleration section becomes longer (the acceleration section becomes shorter). As a result, the maximum peak position of the cam speed tends to be before 1/3 of the discharge stroke section. is there.
[0049]
For this reason, the cam shown in FIG. 3 is a first one in which the cam acceleration from the bottom dead center is suppressed to a small positive value in order to set the maximum peak position of the cam speed to 1/3 to 1/2 of the discharge stroke section. Following the cam portion {circle over (1)}, a second cam portion {circle around (2)} is provided that gradually increases the cam acceleration and then decreases to a negative acceleration, and further up to the top dead center following the second cam portion. A third cam portion {circle around (3)} is provided in which the negative cam acceleration is approximately the same as the limit acceleration at which the cam and plunger are not separated even at the maximum reciprocating frequency of the plunger, and the plunger extends from the top dead center to the bottom dead center. In the intake stroke, the cam profile has a target acceleration curve {circle over (3)}, {circle over (2)}, {circle over (1)} with respect to the cam acceleration and top dead center of the discharge stroke.
[0050]
By reducing the negative cam acceleration to near the limit over a wide range near the top dead center, it becomes possible to decelerate the cam speed in a short section, so the cam speed peak position (= acceleration 0) can be easily discharged. It can arrange | position after 1/3 of an area. If the acceleration near the top dead center is set to a simple constant acceleration, it becomes like the cam B in FIG. 4, and since the sufficient deceleration cannot be obtained, the deceleration section becomes long and the speed peak is reduced to 1/3 or later. It becomes difficult to place.
[0051]
Here, the limit acceleration indicated by a dotted line refers to a limit acceleration in which the spring force and the inertial force are balanced, and jumping does not occur even at the maximum operation speed of the pump. Further, the minimum acceleration value in FIG. 3 is naturally determined by a lower limit value due to the allowable value of the Hertz stress of the cam and the size limit of the base circle, and the value of the spring force is determined in accordance with this and the magnitude of the limit acceleration. Is decided.
[0052]
As described above, by reducing the negative cam acceleration as much as possible, suppressing the cam acceleration from the bottom dead center to a low level, and re-acceleration from the middle, the cam speed rise can be further suppressed. Therefore, the maximum cam speed peak can be taken backwards. However, when the peak position is behind ½, the discharge amount is reduced. Therefore, the acceleration value, the re-acceleration interval, etc. are appropriately adjusted to be approximately 1/3 to 1/2 of the discharge stroke interval. Try to reach the peak cam speed. At this time, since the cam speed at the top dead center and the bottom dead center is 0, the positive and negative areas of the cam acceleration need to be the same.
[0053]
Preferably, the cam acceleration at the bottom dead center is made continuous, that is, the first-order cam angle derivative (jerk) of the cam acceleration at the bottom dead center is set to zero. As a result, the change in inertial force is continuous, so that high-order vibration components do not appear, and low vibration and low noise can be achieved. In addition, it becomes easy to take measures against noise.
[0054]
In the cam of FIG. 3 described above, in order to keep the cam speed in the invalid section as low as possible, the acceleration curve is set to be low and the acceleration is resumed from the middle. Such re-acceleration is not performed, and the cam acceleration may be monotonously decreased from the bottom dead center to the top dead center as shown in FIG.
[0055]
FIG. 7 is a cam showing another embodiment of the present invention.
[0056]
In FIG. 7, following the first cam portion in which the cam acceleration from the bottom dead center is set to a substantially constant positive value, a second cam portion that gradually decreases the cam acceleration and monotonously decreases to a negative acceleration is provided. Furthermore, the negative cam acceleration up to the top dead center following the second cam portion is set to a substantially constant negative value, and the negative acceleration is substantially the same value as the limit acceleration at which the cam and the plunger are not separated even at the maximum reciprocating frequency of the plunger. In the intake stroke from the top dead center to the bottom dead center, the cam profile having a target acceleration curve with respect to the cam acceleration of the discharge stroke and the top dead center is provided. . Preferably, the jerk at the bottom dead center is set to 0 as in the cam of FIG.
[0057]
Compared with the cam of FIG. 3, although the rise of the cam speed is slightly increased, a practically sufficient discharge performance can be ensured. In addition, since the acceleration of the cam becomes smoother as the re-acceleration is not performed, there is an advantage that it is more advantageous in terms of vibration and noise. As shown in the figure, it is more practical to increase the negative acceleration in the vicinity of the top dead center slightly from the limit acceleration to allow for jumping.
[0058]
FIG. 8 is a diagram for explaining the cam of FIG. 3 and the cam of FIG. 7 according to an embodiment of the present invention.
[0059]
In FIG. 8, the strength of the frequency component of the cam acceleration is shown. The horizontal axis is the vibration order, and the vertical axis is the power spectrum. Since both cams have no discontinuous portions in the acceleration waveform, there are very few high-order vibration components, and both can be pumps with low vibration and low noise. The cam of FIG. 7 is slightly inferior in volume efficiency to the cam of FIG. 3, but is superior in terms of vibration and noise because the change in inertial force proportional to the change in acceleration is smooth, and the higher-order vibration components are further reduced. There is an advantage. Which cam is used depends on whether the emphasis is placed on volumetric efficiency or vibration / noise, and it can be said that there is no difference between superiority and inferiority.
[0060]
As shown in FIG. 1, the cam 100 according to an embodiment of the present invention has the same structure as that of the engine cam shaft 72 and can be added to the cam shaft 72, thereby simplifying the configuration and reducing the cost. There is. In this example, the high-pressure fuel pump 101 is fixed to the engine cover 73 and the cam 100 is pressed against the lifter 3. However, the pump may be attached to the engine block or the like, and the attachment direction is upward, downward, lateral, etc. It can be installed in either direction. Of course, the cam 100 may be built in the pump body 1, and power transmission from the engine cam shaft may be performed via a coupling or the like.
[0061]
As described above, according to the present invention, the high-pressure fuel pump 101 can obtain a high volumetric efficiency over a wide range from the low rotation range to the high rotation range, so that it is high even when the engine is fully open during high-speed running. Sufficient fuel can be supplied with pressure, and the motion performance of a vehicle equipped with this engine is improved. Since the volumetric efficiency is high, it is possible to reduce the displacement of the pump while ensuring the necessary discharge flow rate, and the driving torque is reduced to improve the fuel efficiency.
[0062]
Furthermore, since the cam 100 of the present invention can be configured to minimize the absolute value of the negative cam acceleration near the top dead center, the radius of curvature of the cam is increased, the Hertz stress is reduced, and the durability is improved. Or since the base circle of the cam can be made small while keeping the Hertz stress within an allowable value, the pump becomes small and can be easily arranged in the engine room. At the same time, the driving torque also decreases, so the fuel efficiency of a vehicle equipped with this pump is improved.
[0063]
【The invention's effect】
According to the present invention, it is possible to provide a high-pressure fuel pump that can obtain high volumetric efficiency in a wide range from a low rotation range to a high rotation range, is small, has high torque efficiency, and has little vibration and noise.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a structure of a general high-pressure fuel pump.
FIG. 2 is an overall configuration diagram of an engine fuel supply apparatus using a general high-pressure fuel pump.
FIG. 3 is a view showing an embodiment of a cam according to the present invention.
FIG. 4 is a diagram showing a difference in shape between a cam and another cam according to an embodiment of the present invention.
FIG. 5 is a graph showing a discharge flow rate characteristic of a high-pressure fuel pump according to an embodiment of the present invention.
FIG. 6 is a diagram showing the reason for the difference in flow characteristics depending on the cam shape.
FIG. 7 is a view showing a cam provided with another embodiment of the present invention.
FIG. 8 is a diagram showing a frequency component of cam acceleration according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Pump main body, 2 ... Plunger, 3 ... Lifter, 4 ... Spring, 5 ... Suction valve, 5a ... Spring, 6 ... Discharge valve, 6a ... Spring, 10 ... Suction flow path, 11 ... Discharge flow path, 12 ... Addition Pressure chamber, 20 ... seal, 50 ... fuel tank, 51 ... low pressure pump, 52 ... low pressure regulator, 53 ... common rail, 54 ... injector, 55 ... high pressure regulator, 57 ... low pressure piping, 71 ... engine, 72 ... engine cam Shaft, 73 ... engine cover, 100 ... cam, 101 ... high pressure fuel pump.

Claims (5)

A pressure chamber communicating with the fuel suction passage and the discharge passage; a plunger that reciprocates in the pressure chamber according to the shape of a rotating cam; a suction valve that opens and closes the suction passage; and a discharge that opens and closes the discharge passage. In a high-pressure fuel pump with a valve,
The cam includes a first cam portion in which the cam acceleration from the bottom dead center in a discharge stroke from the bottom dead center to the top dead center is suppressed to a small positive value, and a cam following the first cam portion. A second cam portion that gradually decreases and then decreases to a negative acceleration after greatly increasing the acceleration, and the first-order cam angle derivative of the cam acceleration at the bottom dead center and the top dead center is substantially zero. A high-pressure fuel pump comprising a cam profile . A pressure chamber communicating with the fuel suction passage and the discharge passage; a plunger that reciprocates in the pressure chamber according to the shape of a rotating cam; a suction valve that opens and closes the suction passage; and a discharge that opens and closes the discharge passage. In a high-pressure fuel pump with a valve,
An elastic member for pressing the plunger against anti biasing force of the cam,
It said cam includes a first cam portion to which the plunger is suppressed cam acceleration from the bottom dead center in the discharge stroke leading to the top dead center to a positive small value from the bottom dead center, mosquitoes following the first cam portion gradually decreasing having a second cam portion which descends to the negative acceleration Rutotomoni, the second said plunger negative cam acceleration up to top dead center following the cam portion after greatly increased the beam acceleration The third cam portion has a value that is substantially the same as the limit acceleration at which the cam and the plunger do not separate even at the highest reciprocating frequency, and the first-order cam angle derivative of the cam acceleration at the bottom dead center and the top dead center is approximately 0, and in a suction stroke to reach the bottom dead center the plunger from the top dead center, characterized by comprising a cam profile having a symmetrical acceleration curve with respect to the cam acceleration and top dead center of the discharge stroke High pressure fuel pump. A pressure chamber communicating with the fuel suction passage and the discharge passage; a plunger that reciprocates in the pressure chamber according to the shape of a rotating cam; a suction valve that opens and closes the suction passage; and a discharge that opens and closes the discharge passage. In a high-pressure fuel pump with a valve,
An elastic member for pressing the plunger against anti biasing force of the cam,
The cam includes a first cam portion in which the cam acceleration from the bottom dead center in a discharge stroke from the bottom dead center to the top dead center is set to a substantially constant positive value, and a cam acceleration following the first cam portion. gradually and a second cam portion which is decreased monotonically decreases to a negative acceleration, with further negative substantially constant value negative cam acceleration up to top dead center following the second cam portion, A third cam portion having a negative acceleration substantially equal to a limit acceleration at which the cam and the plunger are not separated even at the maximum reciprocating frequency of the plunger; and the plunger is changed from a top dead center to a bottom dead center. high-pressure fuel pump, characterized in that it comprises a cam profile having a symmetrical acceleration curve with respect to the top dead center and the cam acceleration of the previous SL discharge stroke in the suction stroke throughout. The cam, the high-pressure fuel pump according to any one of claims 1 to 3, characterized in that a between about 1 / 3-1 / 2 of the discharge stroke interval the maximum peak position of the cam speed. The suction valve, said an automatic valve opened and closed by the fuel pressure in the pressurizing chamber, one of the claims 1 to 4 fuel pressure in the pressure chamber during the ejection stroke, characterized in that the closing by raising high-pressure fuel pump according to any one of claims.

Images