JP2002048023A - Fuel pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce sliding resistance of an outer gear of a trochoidal gear type fuel pump, and to reduce noise of the pump by delivery pressure pulsation. SOLUTION: Two inner gears 25 and 26 are eccentrically arranged on the inner peripheral side of the outer gear 24 by sandwiching a partition wall 28, and the eccentric directions of both inner gears 25 and 26 are mutually dislocated to the opposite side by 180 deg. so that fuel pressure loads mutually act on the opposite side by 180 deg. to the outer gear 24 from the two inner gears 25 and 26. The tooth number of the outer gear 24 is set to a minimum value '5' of the tooth number of an odd number, the tooth number of the inner gears 25 and 26 is set to a minimum value '4' of the tooth number of an even number so that a rotational phase of the two inner gears 25 and 26 is made different by a half pitch, a phase of a delivery pressure pulsing wave is made different by a half period of the pulsing wave, pressure pulsation is attenuated by interference, a generating frequency area of pump noise is reduced up to a generating frequency area of an engine sound, and the pump noise is masked with the familiar engine sound of a driver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a trochoid gear type fuel pump in which two inner gears are eccentrically arranged on the inner peripheral side of one outer gear.

[0002]

2. Description of the Related Art In recent years, the use of a trochoid gear type fuel pump has been studied in order to improve the fuel discharge performance of a fuel pump mounted on a vehicle. In this trochoid gear type fuel pump, as shown in FIG. 9, an inner gear 3 with external teeth is eccentrically arranged on an inner peripheral side of an outer gear 2 with internal teeth rotatably housed in a cylindrical pump casing 1. At the same time, the two gears 2 and 3
A pump chamber 4 is formed between the teeth of the drive motor (not shown).
By rotating the inner gear 3 to rotate the outer gear 2, the volume of the pump chamber 4 is continuously increased / decreased while moving the pump chamber 4 between the teeth of the two gears 2 and 3 in the rotation direction. To suck and discharge fuel.

[0003]

In such a trochoid gear type fuel pump, fuel is sucked into the pump chamber 4 in a region where the volume of the pump chamber 4 is increased by the rotation of the two gears 2 and 3, and then the trochoid gear is pumped. The fuel in the pump chamber 4 is pressurized and discharged in a region where the volume of the pump chamber 4 decreases. At this time, in the discharge region where the volume of the pump chamber 4 is reduced, the fuel in the pump chamber 4 is pressurized and the fuel pressure (fuel pressure) increases, so that the outer pressure is applied to the outer gear 2 due to the increase in the fuel pressure. . Since the load in the radial direction due to such a rise in the fuel pressure does not occur in the suction region (the suction port side) where the fuel pressure in the pump chamber 4 decreases, the load in the radial direction on the outer gear 2 is limited by the fuel pressure in the pump chamber 4. It acts only on the ascending discharge area (discharge port side), and this becomes an eccentric load, so that a part of the outer gear 2 on the discharge port side is strongly pressed against the inner peripheral surface of the pump casing 1. For this reason, the sliding resistance (friction loss) of the outer gear 2 with respect to the pump casing 1 increases, and accordingly, the load on the drive motor increases, so that the power consumption increases or the fuel discharge performance decreases (the pump rotation speed decreases). Lowering).

A trochoid gear type fuel pump is
Since the volume change of the pump chamber 4 is repeated, a discharge pressure pulsation having a frequency corresponding to the number of teeth of the outer gear 2 is generated, and the pressure pulsation causes the fuel tank, the fuel pipe, the floor panel of the vehicle, and the like to vibrate, thereby causing noise and vibration. There is also a drawback that becomes large.
For this reason, when using a trochoid gear type fuel pump, measures to reduce noise such as installing a pressure pulsation reduction device outside the fuel pump or attaching a sound insulating material to the vehicle body are used to reduce noise and vibration. However, there is a disadvantage that the cost increases.

[0005] The present invention has been made in view of these circumstances, and an object thereof is to reduce the sliding resistance (friction loss) of the outer gear with respect to the pump casing,
An object of the present invention is to provide a fuel pump that can reduce power consumption of a drive motor and improve fuel discharge performance, and can reduce pump noise and vibration due to discharge pressure pulsation at low cost.

[0006]

In order to achieve the above object, a trochoid gear type fuel pump according to a first aspect of the present invention is configured such that two inner gears are overlapped on the inner peripheral side of one outer gear with a partition wall interposed therebetween. While eccentrically arranged in the combined state,
The first feature is that the eccentric directions of both inner gears with respect to the outer gear are shifted to the opposite side by 180 °, and the number of teeth of the outer gear is set to “5” which is the minimum value of the odd number of teeth. The second feature is that the number of teeth is set to "4" which is the minimum value of the number of even teeth.

[0007] In this configuration, the two inner gears disposed on the inner peripheral side of the outer gear have eccentric directions that are one to one another.
Because it is shifted to the opposite side by 80 °, the two inner gears
The fuel pressure rising sides (discharge ports) are shifted by 180 ° from each other. As a result, a load in the outer diameter direction due to a rise in fuel pressure from one inner gear to another outer gear is 1
Since it acts on the opposite side by 80 °, the load in the outer radial direction acting on the outer gear is balanced, and almost no eccentric load acts on the outer gear. For this reason, the outer gear is not strongly pressed against the inner peripheral surface of the pump casing by the fuel pressure, and the sliding resistance (friction loss) of the outer gear with respect to the pump casing becomes smaller than before, and accordingly,
The load on the drive motor is reduced, and power consumption is reduced. Moreover, since the fuel is sucked and discharged by the two inner gears in the outer gear, the fuel discharge performance can be effectively improved in combination with the above-described sliding resistance reduction effect.

In general, in a trochoid gear type fuel pump, the number of teeth of the inner gear should be one less than the number of teeth of the outer gear, but if the number of teeth of the outer gear is even (the number of teeth of the inner gear is odd), 2 The rotation phases of the two inner gears match. In this state, the phases of the pulsation waves of the discharge pressures of the two inner gears match, and when the pressure pulsation wave of one inner gear has a peak (valley), the other also has a peak (valley), so that the pressure pulsation of the two inner gears Amplify each other,
Pump noise / vibration due to pressure pulsation increases.

As a countermeasure, it is conceivable that the number of teeth of the outer gear is an odd number and the number of teeth of the inner gear is an even number which is one less than the number of teeth of the outer gear. If you do this,
The rotation phases of the two inner gears are shifted by a half pitch, and the phases of the pulsation waves of the discharge pressure of the two inner gears are shifted by a half cycle of the pulsation waves. As a result, when the pressure pulsation wave of one inner gear has a peak, the other becomes a valley, and the pressure pulsations of the two inner gears interfere with each other and cancel each other. As a result, the pressure pulsation is reduced, and the pump noise and vibration due to the pressure pulsation are reduced. However, a little pump noise still remains.

[0010] This is considered to be due to the occurrence of a phase shift of the pressure pulsation corresponding to the difference in the length of the fuel discharge passage (mainly the thickness of the outer gear) until the pressure pulsation of the two inner gears interferes. The pump noise generated by this phase shift has a lower sound pressure level than the engine sound,
Since the pump noise is generated in a frequency range higher than the engine sound, during an idle operation in which the engine sound is relatively quiet, the pump noise reaches the driver's ear as a noise different from the engine sound.

To reduce the pump noise, it is conceivable to reduce the thickness of the outer gear to reduce the phase shift of the pressure pulsation. However, if the thickness of the outer gear is reduced,
Since the volume of the pump chamber is reduced and the fuel discharge amount is reduced, it is necessary to increase the pump rotation speed to secure the required discharge amount. However, when the pump rotation speed is increased, the frequency of the discharge pressure pulsation increases, and the pressure pulsation wavelength shortens. Therefore, the thickness of the outer gear is reduced, and the difference between the lengths of the two fuel discharge channels is reduced. Also, the phase shift of the pressure pulsation cannot be reduced, and pump noise occurs due to the phase shift of the pressure pulsation.

Therefore, in claim 1, the number of teeth of the outer gear is set to "5" which is the minimum value of the number of odd-numbered teeth, and the number of teeth of the inner gear is set to "4" which is the minimum value of the number of even-numbered teeth. As described above, the frequency range in which the pump noise (discharge pressure pulsation) is generated is related to the number of teeth of the outer gear. The smaller the number of outer gear teeth, the lower the frequency range in which the pump noise (discharge pressure pulsation) is generated. Therefore, if the number of teeth of both gears is set to the minimum value, the frequency range in which pump noise (discharge pressure pulsation) occurs can be minimized, and the pressure pulsation wavelength can be maximized. Thereby, the phase shift of the pressure pulsation can be minimized, and the pump noise due to the phase shift of the pressure pulsation can be reduced. In addition, the frequency range in which the pump noise is generated can be reduced to the frequency range in which the engine sound is generated during the idling operation, and the pump noise can be made to have the same frequency range as the engine sound during the idling operation. As a result, even during an idling operation in which the engine sound is relatively quiet, the pump noise is masked by the familiar engine sound of the driver to a level that is hardly noticed by the driver, and the problem of the pump noise can be solved.
As a result, conventional noise measures (pressure pulsation reduction device, sound insulation material, etc.) become unnecessary, and low noise and low vibration can be realized at low cost.

Further, as the number of teeth of both gears decreases, the volume of the gap between the teeth of both gears (the capacity of the pump chamber) increases, and the fuel discharge amount per one rotation of the pump increases. Therefore, when the number of teeth of both gears is set to the minimum value, the volume of the pump chamber between the teeth of both gears can be maximized, and the fuel discharge amount per one rotation of the pump can be maximized. Can be As a result, even if the pump rotation speed is reduced, the required discharge amount can be secured, and the pump discharge capacity can be margined, and by lowering the pump rotation speed, pump noise (discharge pressure pulsation) is generated. Since the frequency range can be further reduced and the pressure pulsation wavelength can be further increased, the phase shift of the pressure pulsation can be further reduced, and the effect of reducing pump noise can be further enhanced.

However, as the number of teeth of both gears decreases, the amount of eccentricity of both gears increases, and the mechanical loss (friction loss) increases. As a result, the load on the drive motor increases and the efficiency decreases. .

Therefore, the number of teeth of the outer gear is set to the second smallest number "7" with an odd number of teeth, and the number of teeth of the inner gear is set to the second smallest number "6" with an even number of teeth. It is good. In this way, the amount of eccentricity of both gears can be reduced as compared with the case where the number of teeth of both gears is minimized, so that mechanical loss (friction loss) can be reduced and efficiency can be improved. In addition, it is possible to reduce the phase shift of the pressure pulsation and to lower the frequency of the pump noise, and it is possible to reduce the pump noise to a level at which there is substantially no problem. Incidentally, claim 2
In the configuration of the above, the fuel discharge amount per one rotation of the pump is smaller than the case where the number of teeth of both gears is the minimum value. However, if the pump rotation speed is approximately the same as the conventional one, the required discharge amount is sufficiently secured. be able to.

[0016]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.
Here, FIG. 1 is a longitudinal sectional view showing a cutaway pump section 12 of the fuel pump, FIG. 2 is an AA sectional view of FIG. 1, FIG. 3 is a DD sectional view of FIG. 4, and FIG. FIG. 5 is a bottom view of FIG.
6 is a sectional view taken along line CC of FIG. 3, FIG. 6 is a sectional view taken along line EE of FIG. 3, and FIG.

First, the overall configuration of a trochoid gear type fuel pump will be schematically described with reference to FIG. A trochoid gear type pump section 12 and a motor section 13 are assembled in a cylindrical housing 11 of a fuel pump. At one end (lower end) of the housing 11, a pump cover 14 that covers the lower surface of the pump section 12 is fixed by caulking or the like, and a fuel inlet 15 formed in the pump cover 14 is formed.
Then, fuel in a fuel tank (not shown) is sucked into the pump unit 12. A motor cover 16 that covers the motor unit 13 is fixed to the other end (upper end) of the housing 11 by caulking or the like.
3 are provided with a connector 17 for supplying electricity to the fuel cell 3 and a fuel discharge port 18. The fuel discharged from the pump unit 12 is
The fuel is discharged from the fuel discharge port 18 through a gap between the armature 33 of the motor unit 13 and the magnet 38.

Next, the configuration of the trochoid gear pump 12 will be described with reference to FIGS. Pump section 12
Is formed by closing upper and lower openings of a cylindrical casing 21 with a casing cover 22 and an inner side cover 23, and these components are fixed together with the pump cover 14 in the housing 11 by screwing or the like. An inner cover 23 is sandwiched between the cover 14 and the cylindrical casing 21. One outer gear 24 and two inner gears 25 and 26 are housed in the casing of the pump section 12.

The outer gear 24, the inner gears 25 and 2
6. The inner side cover 23 and the cylindrical casing 21 are formed of a wear-resistant material such as an iron-based sintered metal, and the inner surface (lower surface) of the casing cover 22 and the inner surface (upper surface) of the inner side cover 23 are formed. ) May be subjected to a surface treatment such as a fluororesin coating in order to reduce the sliding resistance to each of the gears 24 to 26.

As shown in FIG. 2, on the inner peripheral side of the outer gear 24 and the outer peripheral side of the inner gears 25 and 26, there are formed internal teeth 24a and external teeth 25a and 26a, respectively.
The number of teeth of 4 is an odd number, and the number of teeth of the inner gears 25 and 26 is formed as an even number smaller by one than the number of teeth of the outer gear 24. Further, in the embodiment (1), the number of teeth of the outer gear 24 is set to “5” which is the minimum value of the number of odd teeth, and the number of teeth of the inner gears 25 and 26 is the minimum value of the number of even teeth. It is set to a certain “4”. Also, the inner gears 25, 2
The tooth thickness of No. 6 is formed to be the same as the tooth thickness of the outer gear 24.

The outer gear 24 is rotatably fitted in a circular hole 27 formed in the cylindrical casing 21.
The thickness dimension (axial dimension) of the outer gear 24 is smaller than the thickness dimension of the cylindrical casing 21 by the side clearance. On the inner peripheral side of the outer gear 24, a partition wall 28 (see FIGS. 1 and 3) that divides a space in the outer gear 24 into two equal parts is formed. This partition wall 28
May be formed integrally with the outer gear 24, or a partition wall 28 formed as a separate component may be fixed to the inner peripheral center portion of the outer gear 24 by joining or the like, or between the two divided outer gears. Alternatively, the outer gear 24 may be formed by interposing a partition wall of another part and integrating these three parts by joining or the like.

On the inner peripheral side of the outer gear 24, two inner gears 25 and 26 are eccentrically arranged so as to overlap with each other with a partition wall 28 interposed therebetween.
The eccentric directions of 5, 26 are offset by 180 ° from each other. And, the teeth 24a of each gear 24, 25, 26,
Five pump chambers 29, 30 (see FIG. 2) are formed between the teeth by engagement or contact of 25a, 26a. In this case, since the inner gears 25 and 26 are eccentric with respect to the outer gear 24, each gear 2
The operation in which the engagement amount of the teeth 24a, 25a, 26a of 4, 25, 26 continuously increases and decreases, and the volume of each pump chamber 29, 30 continuously increases and decreases is repeated with one rotation as a cycle. .

As shown in FIGS. 1 and 3, the inner gear 2
5 and 26 are the casing cover 22 and the pump cover 14.
Are rotatably fitted to and supported by cylindrical bearings 31 and 32 eccentrically press-fit to the opposite sides of each other at an angle of 180 °, and a rotating shaft 34 of an armature 33 of the motor unit 13 is provided inside the cylindrical bearings 31 and 32. It has been inserted. As shown in FIG. 7, the D-shaped connection hole of the gear-shaped coupling 60 is inserted and fitted into the D-cut portion of the rotating shaft 34, and the coupling 60 is formed at the center of the partition wall 28 of the outer gear 24. The rotary shaft 34 and the outer gear 24 are connected so as to be able to transmit rotation by being inserted and fitted into a coupling hole 61 having a coupling shape.

The connecting structure between the rotating shaft 34 of the motor section 13 and the outer gear 24 is not limited to the above-described structure. The D-shaped connecting hole formed in the center of the partition wall 28 of the outer gear 24 is The outer shaft 24 and the rotating shaft 34 of the motor unit 13 may be connected so as to be able to transmit rotation by being inserted and fitted into the D-cut part.

In this case, when the outer gear 24 is rotationally driven by the motor section 13, the inner gears 25 and 26 meshing with the outer gear 24 rotate about the cylindrical bearings 31 and 32 eccentric to 180 ° opposite sides. still,
The radial load of the armature 33 of the motor unit 13 is supported by inserting the rotating shaft 34 into a radial bearing 36 pressed into the center of the casing cover 22, and the load of the armature 33 in the thrust direction is reduced by the pump cover. 14 is supported by a thrust bearing 37 press-fitted inside the center.

The fuel sucked from the fuel suction port 15 of the pump cover 14 is divided in two directions and sucked into the pump chambers 29, 30 of the upper and lower inner gears 25, 26. That is, half of the fuel sucked from the fuel suction port 15 is supplied to the suction port 39 formed in the inner side cover 23 (see FIG. 3).
From the pump chamber 30 of the lower inner gear 26. The remaining half of the fuel sucked through the fuel inlet 15 is supplied to the fuel introduction groove 40 (FIGS.
5) → through hole 41 of the inner side cover 23 (FIG. 3)
→ The through-flow channel 42 of the cylindrical casing 21 (see FIG. 3) → The fuel is introduced into the pump chamber 29 of the upper inner gear 25 through the fuel introduction groove 43 (see FIGS. 3 and 6) on the inner surface of the casing cover 22. .

The pump chamber 3 of the lower inner gear 26
The fuel discharged from 0 is discharged from the discharge port 45 of the inner side cover 23 (see FIG. 1) → the discharge groove 47 on the inner surface of the pump cover 14 (see FIGS. 1 and 5) → the discharge channel 48 (see FIG. 1). The liquid is discharged to the motor section 13 through the path. The discharge channel 48 is formed by the inner side cover 23 and the cylindrical casing 21.
And the casing cover 22 is vertically penetrated.

On the other hand, the pump chamber 2 of the upper inner gear 25
9 is discharged from the discharge port 44 of the casing cover 22 (see FIGS. 1 and 6) to the motor unit 13 side.

In the trochoid gear type fuel pump constructed as described above, when the motor 13 rotates and the outer gear 24 and the inner gears 25 and 26 rotate, each gear 2
The engagement amount of the teeth 24a, 25a, 26a of 4, 25, 26 continuously increases and decreases, and each tooth 24a, 25a, 26
The operation of continuously increasing / decreasing the volume of each of the pump chambers 29 and 30 formed between “a” is repeated with one rotation as a cycle.
Thereby, in the pump chambers 29 and 30 whose volumes are expanded,
In the pump chambers 29 and 30 where the fuel is transferred while sucking the fuel and the volume is reduced, the transferred fuel is supplied to the discharge port 4.
Discharge from 4,45.

At this time, in the discharge region where the volumes of the pump chambers 29 and 30 are reduced, the fuel in the pump chambers 29 and 30 is pressurized to increase the fuel pressure (fuel pressure). Load is applied in the outer diameter direction. The load in the outer diameter direction due to such a rise in fuel pressure is reduced by the pump chamber 2.
Since the pressure does not occur in the suction region where the fuel pressure of the pump chambers 9 and 30 is reduced, the load on the outer gear 24 in the radial direction is limited to the discharge region (the discharge port 4 where the fuel pressure of the pump chambers 29 and 30 increases).
(4, 45 side) only.

In the present embodiment (1), the two inner gears 25 and 26 arranged on the inner peripheral side of the outer gear 24 have their eccentric directions deviated by 180 ° from each other, so that the two inner gears 25 and 26 have the same eccentric direction. 26, the fuel pressure increasing side (discharge ports 44, 45) is shifted by 180 ° from each other.
As a result, the loads F1 and F2 (see FIG. 2) in the radial direction due to the increase in the fuel pressure act on the outer gear 24 from the two inner gears 25 and 26 on one outer gear 24 by 180 ° opposite to each other. Outer radial load F
1 and F2 are balanced so that an eccentric load hardly acts on the outer gear 24. For this reason, the outer gear 24 is not strongly pressed against the inner peripheral surface of the cylindrical casing 21 by the fuel pressure, and the sliding resistance (friction loss) of the outer gear 24 with respect to the cylindrical casing 21 becomes smaller than before, and the motor unit The load of the power supply 13 is reduced, and the power consumption is reduced. In addition, since the fuel is sucked and discharged by the two inner gears 25 and 26 in the outer gear 24, the fuel discharge performance can be effectively improved in combination with the above-described sliding resistance reduction effect.

In general, in a trochoid gear type fuel pump, the number of teeth of the inner gears 25 and 26 may be one less than the number of teeth of the outer gear 24. However, the number of teeth of the outer gear 24 is an even number (the number of teeth of the inner gears 25 and 26). Are odd numbers), the rotational phases of the two inner gears 25 and 26 match. In this state, the phases of the pulsation waves of the discharge pressures of the two inner gears 25 and 26 match, and when the pressure pulsation wave of one of the inner gears has a peak (valley), the other also has a peak (valley).
The pressure pulsations of the two inner gears 25 and 26 amplify each other, and the noise and vibration due to the pressure pulsation increase.

As a countermeasure, the number of teeth of the outer gear 24 is odd, and the number of teeth of the inner gears 25 and 26 is
It is conceivable that the number of teeth is one less than the number of teeth of four.
By doing so, the rotation phases of the two inner gears 25 and 26 are shifted by a half pitch, and the phases of the pulsation waves of the discharge pressure of the two inner gears 25 and 26 are shifted by a half cycle of the pulsation waves. As a result, when the pressure pulsation wave of one of the inner gears has a peak, the other has a valley, and the pressure pulsations of the two inner gears 25 and 26 interfere with each other and cancel each other, thereby greatly reducing the pressure pulsation. Although the pump noise and vibration due to the pressure pulsation are greatly reduced, a little pump noise still remains.

This is because the two inner gears 25, 26
It is considered that a phase shift of the pressure pulsation corresponding to the difference in the length of the fuel discharge passage until the pressure pulsation interferes (mainly the thickness of the outer gear 24) occurs. The pump noise generated by this phase shift has a lower sound pressure level than the engine sound, but is generated in a higher frequency range than the engine sound. The noise reaches the driver's ear as noise different from the engine sound.

In order to reduce the pump noise, it is conceivable to reduce the thickness of the outer gear 24 to reduce the phase shift of the pressure pulsation. However, if the thickness of the outer gear 24 is reduced, the volumes of the pump chambers 29 and 30 become larger. Since the fuel discharge amount decreases and the fuel discharge amount decreases, it is necessary to increase the pump rotation speed to secure the required discharge amount. However, when the pump rotation speed is increased, the frequency of the primary discharge pressure pulsation increases and the wavelength of the primary discharge pressure pulsation decreases, as apparent from the following equation.
Even if the difference between the lengths of the two fuel discharge channels is reduced, the phase shift of the pressure pulsation cannot be reduced, and pump noise due to the phase shift of the pressure pulsation occurs. Primary discharge pressure pulsation frequency = Pump rotation speed (r / min) / 60 x number of outer gear teeth 1
Secondary discharge pressure pulsation wavelength = sound velocity (m / s) / primary discharge pressure pulsation frequency

Therefore, in this embodiment (1), the number of teeth of the outer gear 24 is set to “5”, which is the minimum value of the odd number of teeth, and the number of inner gears 25, The number of teeth of 26 is "4" which is the minimum value of the number of even teeth. As is clear from the above equation,
The frequency range in which the pump noise (primary discharge pressure pulsation) is generated is related to the number of teeth of the outer gear 24. The smaller the number of teeth in the outer gear 24, the lower the frequency range in which the pump noise (primary discharge pressure pulsation) is generated. Therefore, both gears 24, 25, 2
By setting the number of teeth of No. 6 to the minimum value, the frequency range in which pump noise (primary discharge pressure pulsation) occurs can be minimized,
The primary discharge pressure pulsation wavelength can be maximized. Thereby, the phase shift of the primary discharge pressure pulsation can be minimized, and the pump noise due to the phase shift of the pressure pulsation can be reduced.

Further, the frequency range in which the pump noise is generated can be reduced to the frequency range in which the engine sound is generated during idling operation, and the pump noise can be made to have substantially the same frequency range as the engine sound during idling operation. . As a result, even during an idling operation in which the engine sound is relatively quiet, the pump noise is masked by the familiar engine sound of the driver to a level that is hardly noticed by the driver, and the problem of the pump noise can be solved. As a result, conventional noise measures (pressure pulsation reduction device, sound insulation material, etc.) become unnecessary, and low noise and low vibration can be realized at low cost.

Further, as the number of teeth of the two gears 24, 25 (26) decreases, the clearance volume between the teeth of the two gears 24, 25 (26) (the volume of the pump chambers 29, 30) increases. The amount of fuel per hit increases. Therefore, if the number of teeth of both gears 24, 25 (26) is set to the minimum value as in the embodiment (1), the volume of the pump chambers 29, 30 can be maximized, and the number of rotations per pump rotation can be increased. Can maximize the fuel discharge amount. As a result, even if the pump rotation speed is reduced, the required discharge amount can be secured, and the pump discharge capacity can be margined, and by lowering the pump rotation speed, pump noise (discharge pressure pulsation) is generated. Since the frequency range can be further reduced and the pressure pulsation wavelength can be further increased, the phase shift of the pressure pulsation can be further reduced, and the effect of reducing pump noise can be further enhanced.

[Embodiment (2)] By the way, both gears 2
The smaller the number of teeth of 4, 25 (26),
4, 25 (26), the amount of eccentricity increases, and the mechanical loss (friction loss) increases.
Load increases, and the efficiency decreases.

Therefore, in the embodiment (2) of the present invention, as shown in FIG. 8, the number of teeth of the outer gear 24 is an odd number of teeth, the second smallest number "7", and the number of teeth of the inner gears 25 and 26 is Is the second smallest number “6” with an even number of teeth. In this case, the gears 2 and 25 (26) are smaller than the gears 2 and 2 in the embodiment (1) in which the number of teeth is the minimum.
Since the amount of eccentricity of 4, 25 (26) can be reduced, mechanical loss (friction loss) can be reduced and efficiency can be improved.
In addition, since the number of teeth of the two gears 24, 25 (26) is the second smallest, the phase shift of the pressure pulsation can be reduced and the frequency of the pump noise can be reduced. Can be reduced. In the configuration of the embodiment (2), the fuel discharge amount per one rotation of the pump is smaller than that of the embodiment (1) in which the number of teeth of both gears 24 and 25 (26) is the minimum value. If the rotation speed is set to the same level as the conventional one, the required discharge amount can be sufficiently ensured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a fuel pump according to an embodiment (1) of the present invention in a cutaway manner.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a sectional view taken along the line DD of FIG. 4;

FIG. 4 is a bottom view of the fuel pump.

FIG. 5 is a sectional view taken along line BB of FIG. 3;

FIG. 6 is a sectional view taken along the line CC of FIG. 3;

FIG. 7 is a sectional view taken along line EE of FIG. 3;

FIG. 8 is a diagram corresponding to FIG. 2 in the embodiment (1) of the present invention.

FIG. 9 is a view for explaining the structure of a conventional trochoid gear type fuel pump.

FIG. 9 is a sectional view taken along line EE of FIG. 8;

[Explanation of symbols]

11 ... housing, 12 ... pump part, 13 ... motor part,
14 pump cover, 15 fuel inlet, 18 fuel outlet, 21 cylindrical casing, 22 casing cover, 23 internal side cover, 24 outer gear, 24
a ... internal teeth, 25, 26 ... inner gear, 25a, 26a ...
External teeth, 28: Partition wall, 29, 30 ... Pump room, 31, 3
2 ... cylindrical bearing, 34 ... rotating shaft, 39 ... suction port, 40
... Fuel introduction groove, 42 ... Through channel, 43 ... Fuel introduction groove, 4
4, 45 discharge ports, 47 discharge grooves, 48 discharge channels, 60 couplings, 61 connection holes.

[Procedure amendment]

[Submission date] August 10, 2000 (2008.1.
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a fuel pump according to an embodiment (1) of the present invention in a cutaway manner.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a sectional view taken along the line DD of FIG. 4;

FIG. 4 is a bottom view of the fuel pump.

FIG. 5 is a sectional view taken along line BB of FIG. 3;

FIG. 6 is a sectional view taken along the line CC of FIG. 3;

FIG. 7 is a sectional view taken along line EE of FIG. 3;

FIG. 8 is a diagram corresponding to FIG. 2 in the embodiment (2) of the present invention.

FIG. 9 is a view for explaining the structure of a conventional trochoid gear type fuel pump.

[Description of Signs] 11 ... housing, 12 ... pump section, 13 ... motor section,
14 pump cover, 15 fuel inlet, 18 fuel outlet, 21 cylindrical casing, 22 casing cover, 23 internal side cover, 24 outer gear, 24
a ... internal teeth, 25, 26 ... inner gear, 25a, 26a ...
External teeth, 28: Partition wall, 29, 30 ... Pump room, 31, 3
2 ... cylindrical bearing, 34 ... rotating shaft, 39 ... suction port, 40
... Fuel introduction groove, 42 ... Through channel, 43 ... Fuel introduction groove, 4
4, 45 discharge ports, 47 discharge grooves, 48 discharge channels, 60 couplings, 61 connection holes.

Claims (2)

[Claims] An inner gear with external teeth is eccentrically arranged on the inner peripheral side of an outer gear with internal teeth, and a pump chamber formed between the teeth of both gears by meshing both gears is rotated by rotation of both gears. In a fuel pump that sucks and discharges fuel by continuously increasing and decreasing the volume of the pump chamber while moving in the direction, two inner gears are overlapped on the inner peripheral side of one outer gear with a partition wall interposed therebetween. And the eccentric directions of both inner gears with respect to the outer gear are set to one another.
A fuel pump, wherein the number of teeth of the outer gear is five, and the number of teeth of the inner gear is four. 2. A pump chamber formed between teeth of both gears by eccentrically disposing an inner gear with external teeth on the inner peripheral side of an outer gear with internal teeth, and rotating a pump chamber formed between the teeth of both gears by rotation of both gears. In a fuel pump that sucks and discharges fuel by continuously increasing and decreasing the volume of the pump chamber while moving in the direction, two inner gears are overlapped on the inner peripheral side of one outer gear with a partition wall interposed therebetween. And the eccentric directions of both inner gears with respect to the outer gear are set to one another.
A fuel pump, wherein the number of teeth of the outer gear is seven and the number of teeth of the inner gear is six.