Patent Application
20210254588
The present disclosure relates to a high pressure fuel pump and a fuel supply system having the high pressure fuel pump.
Previously, a high pressure fuel pump is widely used in, for example, a fuel supply system of an internal combustion engine while the high pressure fuel pump is configured to deliver fuel, which is suctioned into a pressurizing chamber from a low pressure fuel pump through a suction passage, to a supply destination after pressurizing the fuel in the pressurizing chamber with a plunger.
With respect to the high pressure fuel pump of the positive displacement type discussed above, JP2002-521616A (corresponding to U.S. Pat. No. 6,345,608B1) discloses a technique of controlling closing timing, which is timing of closing a connection between the suction passage and the pressurizing chamber in a delivery stroke, by using a control valve. Here, the delivery stroke is defined as a stroke, in which the plunger is driven toward a delivery side for delivering the fuel out of the pressurizing chamber upon pressurization of the fuel. According to the disclosed technique of JP2002-521616A (corresponding to U.S. Pat. No. 6,345,608B1), the fuel of the pressurizing chamber is pressurized by the plunger and is returned to the suction passage before the closing timing during the delivery stroke for delivering the fuel out of the pressurizing chamber upon pressurization. With respect to this point, according to the disclosed technique of JP2002-521616A (corresponding to U.S. Pat. No. 6,345,608B1), the amount of returned fuel, which is returned from the pressurizing chamber to the suction passage, can be highly accurately controlled by changing the amount of returned fuel through the control of the closing timing.
However, it is found that the energy, which is used to suction the fuel from the low pressure fuel pump into the pressurizing chamber through the suction passage, is excessively lost according to the technique disclosed in JP2002-521616A (corresponding to U.S. Pat. No. 6,345,608B1). Hereinafter, this disadvantage will be described.
First of all, at a time point, which is before the closing timing during the delivery stroke, as shown in
In this backflow generating state, when the suction stroke starts, as shown in
The present disclosure is made in view of the above disadvantage, and it is an objective of the present disclosure to provide a high pressure fuel pump and a fuel supply system, which can limit the energy loss.
Hereinafter, a technical means of the present disclosure for achieving the above objective will be described.
According to a first aspect of the present disclosure, there is provided a high pressure fuel pump for delivering fuel, which is suctioned into a pressurizing chamber from a low pressure fuel pump through a suction passage, to a supply destination after pressurizing the fuel in the pressurizing chamber with a plunger, the high pressure fuel pump comprising: a pump body that forms the suction passage and the pressurizing chamber and slidably supports the plunger; and a control valve that opens a connection between the suction passage and the pressurizing chamber in a suction stroke, during which the plunger is driven toward a suction side for suctioning the fuel into the pressurizing chamber, while the control valve controls closing timing, at which the connection between the suction passage and the pressurizing chamber is closed by the control valve in a delivery stroke, during which the plunger is driven toward a delivery side for delivering the fuel out of the pressurizing chamber upon pressurization of the fuel, wherein: the pump body forms a release passage that is communicated with the suction passage; and the release passage relieves the fuel, which is pressurized by the plunger, from the pressurizing chamber before the closing timing during the delivery stroke.
Furthermore, according to a second aspect of the present disclosure, there is provided a fuel supply system comprising: a low pressure fuel pump that delivers fuel; and a high pressure fuel pump that delivers the fuel, which is suctioned into a pressurizing chamber from the low pressure fuel pump through a suction passage, to a supply destination after pressurizing the fuel in the pressurizing chamber with a plunger, wherein the high pressure fuel pump includes: a pump body that forms the suction passage and the pressurizing chamber and slidably supports the plunger; and a control valve that opens a connection between the suction passage and the pressurizing chamber in a suction stroke, during which the plunger is driven toward a suction side for suctioning the fuel into the pressurizing chamber, while the control valve controls closing timing, at which the connection between the suction passage and the pressurizing chamber is closed by the control valve in a delivery stroke, during which the plunger is driven toward a delivery side for delivering the fuel out of the pressurizing chamber upon pressurization of the fuel, wherein: the pump body forms a release passage that is communicated with the suction passage; and the release passage relieves the fuel, which is pressurized by the plunger, from the pressurizing chamber before the closing timing during the delivery stroke.
Before the closing timing during the delivery stroke according to the first and second aspects of the present disclosure, the fuel, which is pressurized by the plunger, tends to return from the pressurizing chamber to the suction passage. However, this fuel is relieved into the release passage communicated with the suction passage, so that the generation of the backflow of the fuel in the suction passage can be alleviated. Therefore, the returning of the fuel is limited at the connection between the pressurizing chamber and the suction passage after the closing timing during the delivery stroke of the first embodiment, so that the generation of the backflow of the fuel at the suction passage can be alleviated continuously since the time before the closing timing. In this way, the suction passage, in which the generation of the backflow can be alleviated at the time of starting the suction stroke in the first and second aspects of the present disclosure, is in the forward flow generating state where the flow of the fuel from the low pressure fuel pump toward the pressurizing chamber is eased. In this forward flow generating state, the fuel pressure for filling the fuel into the pressurizing chamber through the suctioning of the fuel at the suction stroke with the limited time period, and the energy for suctioning the fuel into the pressurizing chamber through the suction passage can be minimized at the low pressure fuel pump. Thereby, the energy loss can be limited.
The present disclosure, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:
Hereinafter, various embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following respective embodiments, similar structural elements are indicated by the same reference signs and may not be redundantly described. In a case where only a part of a structure is described in each of the following embodiments, the rest of the structure of the embodiment may be the same as that of previously described one or more of the embodiments. Besides the explicitly described combination(s) of structural components in each of the following embodiments, the structural components of different embodiments may be partially combined even though such a combination(s) is not explicitly described as long as there is no problem.
As shown in
The fuel tank 3 stores fuel to be supplied to the internal combustion engine 1. The low pressure fuel pump 4 is an electric pump that is driven by supplying the electric power to the electric pump. The low pressure fuel pump 4 suctions the fuel in the inside of the fuel tank 3. The low pressure fuel pump 4 pressurizes the suctioned fuel to a predetermined low pressure value (e.g., about 0.4 MPa) and then discharges the pressurized fuel to feed the fuel to the high pressure fuel pump 10 that is located at an outside of the fuel tank 3. The low pressure filter 5 has a filter element, which is placed in an inside of the low pressure filter 5 and filters the fuel that is discharged from the low pressure fuel pump 4. In this way, the low pressure filter 5 captures foreign objects, which are mixed in the fuel at the time of feeding the fuel from the inside of the fuel tank 3 to the low pressure filter 5.
The high pressure fuel pump 10 is a mechanical pump that is driven by a crank torque outputted from a crankshaft 1a of the internal combustion engine 1. The high pressure fuel pump 10 suctions the fuel, which is pumped from the low pressure fuel pump 4 and is filtered through the low pressure filter 5. The high pressure fuel pump 10 pressurizes the suctioned fuel to a predetermined high pressure value (e.g., about 250 MPa) and then discharges the pressurized fuel to deliver the fuel to the common rail 6 (serving as a supply destination). At the high pressure fuel pump 10, a fuel delivery amount (i.e., a fuel discharge amount), which is discharged from the high pressure fuel pump 10, is controlled by supplying the electric power to each of a plurality of control valves 11 that are installed in the high pressure fuel pump 10.
The common rail 6 shown in
The ECU 8, which is also referred to as a control device or a controller, includes a microcomputer as a main component thereof. The ECU 8 is connected to the low pressure fuel pump 4, the control valves 11 of the high pressure fuel pump 10, and the fuel injection valves 7. The ECU 8 controls the operation of these connected subjects 4, 11, 7, which are connected to the ECU 8.
The high pressure fuel pump 10, which is applied to the fuel supply system 2, includes a pump body 12, a pump filter 13, a relief valve 14, a drive cam 15, a plurality of movable units 16, a plurality of discharge valves 17 and the plurality of control valves 11, as shown in
The casing 12a is made of metal and is formed in a form of a hollow block. The casing 12a forms a cam receiving chamber 120 and a plurality of internal pressure variable chambers 121. The cam receiving chamber 120 is formed in a form of a cylindrical hole. In the present embodiment, the number of the internal pressure variable chambers 121 is two (i.e., there is provided a pair of internal pressure variable chambers 121). The internal pressure variable chambers 121 are respectively configured in a form of a cylindrical hole such that central axes of the internal pressure variable chambers 121 are perpendicular to a central axis of the cam receiving chamber 120 and intersect with each other at substantially a right angle. Each internal pressure variable chamber 121 extends from an outer peripheral portion of the cam receiving chamber 120 to an outer surface 12as of the casing 12a.
As shown in
The casing 12a and the cylinders 12b, which cooperate with each other to serve as the pump body 12, also cooperate with each other to form a suction passage 124, a plurality of release passages 125 and a plurality of discharge passages 126 shown in
The common passage portion 124b is formed at a location that is between the cylinders 12b in the casing 12a. The common passage portion 124b extends from the outer peripheral portion of the cam receiving chamber 120 to a predetermined location in the casing 12a. In the present embodiment, the number of the branch passage portions 124c is two (i.e., there is provided a pair of branch passage portions 124c). Each branch passage portion 124c is branched from the common passage portion 124b to the pressurizing chamber 122a of the corresponding cylinder 12b. An upstream part 124cu of each branch passage portion 124c is formed at the location between the cylinders 12b in the casing 12a. The upstream part 124cu of each branch passage portion 124c extends between the corresponding internal pressure variable chamber 121 and the common passage portion 124b. A downstream part 124cl of each branch passage portion 124c extends from a corresponding location of the casing 12a, which is displaced away from the location between the cylinders 12b. The downstream part 124cl of each branch passage portion 124c extends between the corresponding internal pressure variable chamber 121 and the corresponding valve installation hole 123.
With the above-described extending structure, the suction passage 124 extends through the cam receiving chamber 120 and then the respective internal pressure variable chambers 121 at the location on the upstream side of the downstream parts 124cl of the respective branch passage portions 124c. Therefore, in the first embodiment, the fuel, which is pumped from the low pressure fuel pump 4, can be drawn into the inlet passage portion 124a, the cam receiving chamber 120, the common passage portion 124b, the upstream part 124cu of each branch passage portion 124c, each internal pressure variable chamber 121, and the downstream part 124cl of each branch passage portion 124c in this order.
In the present embodiment, the number of the release passages 125 is two (i.e., there is provided a pair of release passages 125). Each release passage 125 extends from the corresponding cylinder 12b to the location between the cylinders 12b in the casing 12a. Each release passage 125 extends between the corresponding valve installation hole 123 and the cam receiving chamber 120. A passage cross sectional area of each release passage 125 is set to be equal to or larger than a passage cross sectional area of the downstream part 124cl of the corresponding branch passage portion 124c. With the above-described construction, each release passage 125 is formed to implement the passage cross sectional area, which is equal to or larger than the passage cross sectional area of the downstream part 124cl of the corresponding branch passage portion 124c that is located on an opposite side of a control valve 11 (described later in detail), which is opposite from the release passage 125, while the control valve 11 is installed in the corresponding valve installation hole 123.
In the present embodiment, the number of the discharge passages 126 is two (i.e., there is provided a pair of discharge passages 126). Each discharge passage 126 is formed to extend from the corresponding cylinder 12b to a predetermined location of the casing 12a. Each discharge passage 126 extends from the pressurizing chamber 122a of the corresponding slide hole 122 to a discharge pipe that projects from the casing 12a to the outside of the casing 12a. Each discharge passage 126 is communicated with the pressure accumulation chamber of the common rail 6 through a fuel passage in a pipe joined to the discharge pipe.
A drain passage 127 and a relief passage 128, which are shown in
The pump filter 13 is placed at an upstream part of the inlet passage portion 124a, which is on an upstream side of a branch point where the relief passage 128 is branched from the inlet passage portion 124a. The pump filter 13 filters the fuel, which is pumped from the low pressure fuel pump 4, through the filter element of the pump filter 13. Therefore, the pump filter 13 captures foreign objects, which are mixed in the fuel at the time of feeding the fuel from the low pressure filter 5 to the pump filter 13.
The relief valve 14 is installed to the relief passage 128. The relief valve 14 is a pressure regulating valve that operates mechanically. The relief valve 14 opens when the pressure of the fuel, which is pumped by the low pressure fuel pump 4, is increased to an abnormal value, which is deviated from a normal value (a normal range), at the pump operation time to discharge the pumped fuel to the passages 128, 127, 3a and the fuel tank 3, thereby reducing the pressure of the discharged fuel.
As shown in
In the present embodiment, the number of the movable units 16 is two (i.e., there is provided a pair of movable units 16). Each movable unit 16 includes a roller 160, a tappet 161, a plunger 162, a spring seat 163 and a compression coil spring 164. Each of these constituent components of the movable unit 16 is made of metal. The plunger 162 of each movable unit 16 is received in and extends in the corresponding internal pressure variable chamber 121 and the slide hole 122. The remaining constituent components of each movable unit 16, which are other than the plunger 162, are received in the corresponding internal pressure variable chamber 121.
The roller 160 of each movable unit 16 is shaped into a cylindrical form that is substantially parallel to the central axis of the drive cam 15 and is substantially perpendicular to the central axis of the corresponding internal pressure variable chamber 121. The roller 160 of each movable unit 16 is in rolling contact with the outer peripheral surface 15a of the drive cam 15 in a state where the roller 160 makes line contact with the outer peripheral surface 15a of the drive cam 15 along the central axis of the drive cam 15.
The tappet 161 of each movable unit 16 includes two members 161a, 161b that cooperate with each other and are assembled together in a form of a bottomed cylindrical tubular body that extends substantially perpendicular to the central axis of the drive cam 15 and is coaxial with the corresponding internal pressure variable chamber 121. The tappet 161 of each movable unit 16 is placed such that an opening of the tappet 161 is directed toward the corresponding slide hole 122. The tappet 161 of each movable unit 16 is fitted to and is slidably supported by an inner peripheral surface of the corresponding internal pressure variable chamber 121, so that the tappet 161 can reciprocate in the axial direction. The tappet 161 of each movable unit 16 holds the corresponding roller 160 such that the roller 160 can rotate relative to the tappet 161 and can reciprocate integrally with the tappet 161.
The plunger 162 of each movable unit 16 is shaped into a cylindrical rod form that is substantially perpendicular to the central axis of the drive cam 15 and is coaxial with the internal pressure variable chamber 121. The plunger 162 of each movable unit 16 is fitted to and is slidably supported by an inner peripheral surface of the corresponding slide hole 122, so that the plunger 162 can reciprocate in the axial direction. The plunger 162 of each movable unit 16 is inserted into an inside of a peripheral wall portion (i.e., the tubular member 161a) of the tappet 161 and contacts a bottom wall portion (i.e., the plate member 161b) of the tappet 161. The plunger 162 of each movable unit 16 defines the pressurizing chamber 122a in the corresponding slide hole 122 at an opposite side that is opposite from the tappet 161.
The spring seat 163 of each movable unit 16 is held by the corresponding plunger 162 such that the plunger 162 can reciprocate integrally with the spring seat 163. The compression coil spring 164 of each movable unit 16 is clamped between the corresponding cylinder 12b and the spring seat 163 of the movable unit 16. The compression coil spring 164, which is held at the clamping point of the movable unit 16 and is placed in a resiliently deformed state, urges the plunger 162 against the bottom wall portion (i.e., the plate member 161b) of the tappet 161 and urges the roller 160 against the outer peripheral surface 15a of the drive cam 15.
With this urging structure, the plunger 162 of each movable unit 16, which is in a suction stroke, is driven toward a suction side for suctioning the fuel into the corresponding pressurizing chamber 122a in response to the rotation of the drive cam 15, so that the plunger 162 is moved downward between the top dead center and the bottom dead center. The tappet 161 of each movable unit 16, which is driven in response to progress of the suction stroke, increases the inflow volume of the fuel into the corresponding internal pressure variable chamber 121, so that the internal pressure of the internal pressure variable chamber 121 is reduced.
In contrast, the plunger 162 of each movable unit 16 in a delivery stroke is driven toward a delivery side for delivering the fuel out of the corresponding pressurizing chamber 122a upon pressurization of the fuel in response to the rotation of the drive cam 15, so that the plunger 162 is moved upward between the bottom dead center and the top dead center. The tappet 161 of each movable unit 16, which is driven in response to the progress of this delivery stroke, reduces the inflow volume of the fuel into the corresponding internal pressure variable chamber 121, so that the internal pressure of the corresponding internal pressure variable chamber 121 is increased.
In the present embodiment, as shown in
In the present embodiment, as shown in
In the present embodiment, as shown in
The operation of the high pressure fuel pump 10 having the above-described structure will now be described. The high pressure fuel pump 10 is operated when the ECU 8 starts an electric power supply control operation of the high pressure fuel pump 10 together with an electric power supply control operation of the low pressure fuel pump 4 and an electric power supply control operation of the respective control valves 11 in response to starting of the internal combustion engine 1 upon turning on of a power switch at the vehicle.
In the high pressure fuel pump 10, the delivery stroke of one of the pressurizing chambers 122a and the delivery stroke of the other one of the pressurizing chambers 122a are alternately and continuously executed one after another and are thereby completely shifted, i.e., deviated from each other with respect to the execution timing thereof. However, the operation at each of these pressurizing chambers 122a is substantially identical. Therefore, the operation of only one of the pressurizing chambers 122a will be representatively described.
With reference to
First of all, at the suction stroke shown in
Next, in the pre-stroke period ΔTp of the delivery stroke shown in
Next, in the pressurizing period ΔTa in the delivery stroke shown in
Thus, at the subsequent suction stroke, as shown in
Now, effects and advantages of the first embodiment will be described.
The fuel, which is pressurized by the plunger 162, tends to return from the pressurizing chamber 122a into the suction passage 124, at the time before the closing timing Tc during the delivery stroke according to the first embodiment. However, this fuel is relieved to the release passage 125, which is communicated with the suction passage 124, so that the generation of the backflow of the fuel can be alleviated at the suction passage 124. Therefore, the returning of the fuel is limited at the connection between the pressurizing chamber 122a and the suction passage 124, which is closed by the control valve 11, after the closing timing Tc in the delivery stroke of the first embodiment, so that the generation of the backflow of the fuel at the suction passage 124 can be alleviated continuously since the time before the closing timing Tc. In this way, the suction passage 124, in which the generation of the backflow can be alleviated at the time of starting the suction stroke of the first embodiment, is in the forward flow generating state where the flow of the fuel from the low pressure fuel pump 4 toward the pressurizing chamber 122a is eased. In this forward flow generating state, the fuel pressure for filling the fuel into the pressurizing chamber 122a through the suctioning of the fuel at the suction stroke with the limited time period, and the energy for suctioning the fuel into the pressurizing chamber 122a through the suction passage 124 can be minimized at the low pressure fuel pump 4. Thereby, the energy loss can be limited.
Furthermore, according to the first embodiment, in the suction passage 124 that passes through the internal pressure variable chamber 121, in which the internal pressure is increased in response to the progress of the delivery stroke, at the location on the upstream side of the communicating connection of the suction passage 124 relative to the release passage 125, the increased internal pressure of the internal pressure variable chamber 121 can exert the flow resistance against the return fuel flow from the pressurizing chamber 122a. Thereby, in addition to the relieving function for relieving the return fuel flow at the release passage 125, the backflow generation alleviating effect can be enhanced. Thus, the reliability with respect to the advantage of limiting the energy loss can be improved.
As shown in
In the present embodiment, the number of the individual passage portions 2127b is two (i.e., there is provided a pair of individual passage portions 2127b). Each individual passage portion 2127b extends from the corresponding release passage 125 to the merging passage portion 2127c that is common to the individual passage portions 2127b. In other words, each release passage 125 is directly connected to the corresponding individual passage portion 2127b in the drain passage 2127. A flow restricting portion 2127a is formed at an intermediate part of each individual passage portion 2127b such that a passage cross-sectional area of the flow restricting portion 2127a is reduced in comparison to a passage cross-sectional area of the corresponding release passage 125. Specifically, in the present embodiment, the number of the flow restricting portions 2127a is two (i.e., there is provided a pair of flow restricting portions 2127a). The merging passage portion 2127c extends from a downstream end of each of the individual passage portions 2127b to the drain pipe that projects from the casing 12a to the outside of the casing 12a.
As discussed above, according to the second embodiment, the passage cross-sectional area of at least the corresponding portion of the drain passage 2127, which is directly connected to the corresponding release passage 125, is reduced in comparison to the passage cross-sectional area of the corresponding release passage 125. Specifically, the passage cross-sectional area of at least the corresponding portion of the drain passage 2127, to which the fuel can be drained from the corresponding release passage 125, is reduced in comparison to the passage cross-sectional area of the release passage 125. Accordingly, air, which is accumulated in the suction passage 124 and the pressurizing chambers 122a during the stop period (non-operating period) of the low pressure fuel pump 4, is pressurized upon restarting of the operation of the low pressure fuel pump 4 and can be discharged into the release passages 125 and the drain passage 2127 in this order. Thus, it is possible to limit a deterioration in a fuel filling performance for filling the fuel into the pressurizing chambers 122a, which would be otherwise caused by interfering of the suctioning of the fuel into the suction passage 124 and the pressurizing chambers 122a by the accumulated air. Therefore, it is possible to limit the energy loss and the deterioration in the delivery performance of the fuel from each pressurizing chamber 122a.
As shown in
The release passage 3125 of the third embodiment under the above definitions extends between the two valve installation holes 123 as if the two release passages 125 of the first embodiment are joined together. In this way, the release passage 3125 is communicated with the downstream part 124cl of the primary branch passage portion 124c through the primary control valve 11 and is also communicated with the downstream part 124cl of the secondary branch passage portion 3124c through the secondary control valve 3011. The release passage 3125 extends from the corresponding cylinder 12b to the location between the cylinders 12b in the casing 12a. Furthermore, on the upstream side of the corresponding downstream part 124cl, which forms the communicating connection relative to the release passage 3125, at each branch passage portion 124c, 3124c, the suction passage 124 passes through the common cam receiving chamber 120 and then passes through each internal pressure variable chamber 121.
According to the third embodiment, the fuel of the primary pressurizing chamber 122a, which is pressurized by the plunger 162 before the closing timing Tc during the delivery stroke at the primary pressurizing chamber 122a, tends to return to the primary branch passage portion 124c that is branched toward the primary pressurizing chamber 122a in the suction passage 124. At this time, when the suction stroke is executed in the secondary pressurizing chamber 3122a, in which the timing of executing the delivery stroke is shifted from the timing of executing the delivery stroke in the primary pressurizing chamber 122a, the secondary branch passage portion 3124c, which is branched toward the secondary pressurizing chamber 3122a, receives a suction pressure from the secondary pressurizing chamber 3122a through the communicating connection between the secondary branch passage portion 3124c and the secondary pressurizing chamber 3122a that is opened. Particularly, in the secondary pressurizing chamber 3122a, which is designed such that the secondary pressurizing chamber 3122a and the primary pressurizing chamber 122a execute the delivery stroke in turn, the suction stroke must be executed, so that the secondary branch passage portion 3124c is likely to receive the suction pressure for a relatively long period of time.
Therefore, in the third embodiment, the suction pressure is conducted from the secondary branch passage portion 3124c to the primary branch passage portion 124c through the release passage 3125 that is communicated with the primary and secondary branch passage portions 124c, 3124c. In this way, the fuel, which tends to return from the primary pressurizing chamber 122a to the primary branch passage portion 124c, is drawn by the conducted suction pressure and is thereby likely relieved into the release passage 3125, so that the backflow generation alleviating effect in the suction passage 124 can be enhanced.
This enhanced backflow generation alleviating effect can be similarly implemented before the closing timing Tc during the delivery stroke at the secondary pressurizing chamber 3122a because of a similar principle, which is substantially the same as the principle discussed above with reference to the primary pressurizing chamber 122a except that the secondary pressurizing chamber 3122a is used in place of the primary pressurizing chamber 122a.
Specifically, in the third embodiment, the fuel of the secondary pressurizing chamber 3122a, which is pressurized by the plunger 162 before the closing timing Tc during the delivery stroke at the secondary pressurizing chamber 3122a, tends to return to the secondary branch passage portion 3124c, which is branched toward the secondary pressurizing chamber 3122a in the suction passage 124. At this time, when the suction stroke is executed in the primary pressurizing chamber 122a, in which the timing of executing the delivery stroke is shifted from the timing of executing the delivery stroke in the secondary pressurizing chamber 3122a, the primary branch passage portion 124c, which is branched toward the primary pressurizing chamber 122a, receives a suction pressure from the primary pressurizing chamber 122a through the communicating connection between the primary branch passage portion 124c and the primary pressurizing chamber 122a that is opened. Particularly, in the primary pressurizing chamber 122a, which is designed such that the primary pressurizing chamber 122a and the secondary pressurizing chamber 3122a execute the delivery stroke in turn, the suction stroke must be executed, so that the primary branch passage portion 124c is likely to receive the suction pressure for a relatively long period of time.
Therefore, the suction pressure is conducted from the primary branch passage portion 124c to the secondary branch passage portion 3124c through the release passage 3125 that is communicated with the primary and secondary branch passage portions 124c, 3124c. In this way, the fuel, which tends to return from the secondary pressurizing chamber 3122a to the secondary branch passage portion 3124c, is drawn by the conducted suction pressure and is thereby likely relieved into the release passage 3125, so that the backflow generation alleviating effect in the suction passage 124 can be enhanced.
Therefore, according to the third embodiment, the reliability with respect to the advantage of limiting the energy loss can be improved.
As shown in
As discussed above, according to the fourth embodiment, the passage cross-sectional area of at least the portion of the drain passage 4127, which is directly connected to the release passage 3125, is reduced in comparison to the passage cross-sectional area of the release passage 3125. Specifically, the passage cross-sectional area of at least the corresponding portion of the drain passage 2127, to which the fuel can be directly drained from the release passage 3125, is reduced in comparison to the passage cross-sectional area of the release passage 3125. Accordingly, the air, which is accumulated in the suction passage 124 and the pressurizing chambers 122a, 3122a during the stop period (the non-operating period) of the low pressure fuel pump 4, is pressurized upon restarting of the operation of the low pressure fuel pump 4 and can be discharged into the release passage 3125 and the drain passage 4127 in this order. Thus, it is possible to limit the deterioration in the fuel filling performance for filling the fuel into the pressurizing chambers 122a, 3122a, which would be otherwise caused by interfering of the suctioning of the fuel into the suction passage 124 and the pressurizing chambers 122a, 3122a by the accumulated air. Therefore, it is possible to limit the energy loss and the deterioration in the delivery performance of the fuel from each pressurizing chamber 122a, 3122a.
As shown in
Therefore, in the fifth embodiment, the fuel, which is pumped from the low pressure fuel pump 4, can be suctioned through the inlet passage portion 124a, the cam receiving chamber 120, the common passage portion 124b, the upstream part 124cu of each branch passage portion 124c, 3124c, and the downstream part 124cl of each branch passage portion 124c, 3124c in this order. Furthermore, in the fifth embodiment, the fuel, which is pumped from the low pressure fuel pump 4, can be fed to the cam receiving chamber 120, the common passage portion 124b, the upstream part 124cu of each branch passage portion 124c, 3124c, and each internal pressure variable chamber 121 in this order. Thereby, the suction passage 5124 of the fifth embodiment supplies the fuel to each pressurizing chamber 122a, 3122a while the suction passage 5124 bypasses each internal pressure variable chamber 121 at the location on the upstream side of the corresponding downstream part 124cl, which forms the communicating connection relative to the release passage 3125, in each branch passage portion 124c, 3124c.
According to the fifth embodiment discussed above, in the suction passage 5124 that bypasses each internal pressure variable chamber 121, in which the internal pressure is increased and decreased upon the driving of the movable unit 16 including the plunger 162, at the location on the upstream side of the communicating connection of the suction passage 5124 relative to the release passage 3125, it is less likely that foreign objects, which are generated through the driving of the movable unit 16, are mixed into the fuel. Thus, it is possible to limit the deterioration in the backflow generation alleviating effect that would be caused by clogging of the release passage 3125 with the foreign objects mixed into the fuel in the suction passage 5124. As a result, the energy loss can be limited for a relatively long period of time.
Furthermore, according to the fifth embodiment, the branch passage portions 124c, 3124c of the suction passage 5124 can be collectively formed between the cylinders 12b in the pump body 12, so that this arrangement can contribute to the size reduction of the pump body 12.
As shown in
In the sixth embodiment, which is constructed in the above described manner, the fuel, which is pumped from the low pressure fuel pump 4, can be drawn into the inlet passage portion 124a, the cam receiving chamber 120 and each branch passage portion 124d, 6124 in this order. Additionally, in the sixth embodiment, the fuel, which is pumped from the low pressure fuel pump 4, can be fed to the cam receiving chamber 120, the common passage portion 124b, each branch passage portion 124c, 3124c having only the upstream part 124cu, and each internal pressure variable chamber 121 in this order. The suction passage 6124 of the sixth embodiment supplies the fuel to each pressurizing chamber 122a, 3122a while the suction passage 6124 bypasses each internal pressure variable chamber 121 at the location on the upstream side of the corresponding branch passage portion 124d, 6124d, which forms the communicating connection relative to the release passage 3125.
According to the sixth embodiment, in the suction passage 6124 that bypasses each internal pressure variable chamber 121, in which the internal pressure is increased and decreased upon the driving of the movable unit 16 including the plunger 162, at the location on the upstream side of the communicating connection of the suction passage 6124 relative to the release passage 3125, it is less likely that the foreign objects, which are generated through the driving of the movable unit 16, are mixed into the fuel. Thus, it is possible to limit the deterioration in the backflow generation alleviating effect that would be caused by clogging of the release passage 3125 with the foreign objects mixed into the fuel in the suction passage 6124. As a result, the energy loss can be limited for a relatively long period of time.
Furthermore, according to the sixth embodiment, each branch passage portion 124d, 6124d of the suction passage 6124 can be placed at any location that is displaced from the location between the cylinders 12b in the pump body 12, so that this arrangement can contribute to the size reduction of the pump body 12.
As shown in
In addition, a branch passage portion 7125b is added in the release passage 7125. This branch passage portion 7125b extends from an intermediate part of the communication passage portion 7125a, which is located between the branch passage portions 124e, 7124e, to the outer peripheral portion of the cam receiving chamber 120. Thereby, the common release passage 7125, which is common to the two pressurizing chambers 122a, 3122a, extends from the branch passage portion 7125b to the cam receiving chamber 120 and is thereby connected to the common drain passage 127 through the cam receiving chamber 120. The branch passage portion 7125b is formed at the location that is between the cylinders 12b in the casing 12a.
In the seventh embodiment discussed above, the fuel, which is pumped from the low pressure fuel pump 4, can be drawn into the inlet passage portion 7124a and the respective branch passage portions 124e, 7124e. Furthermore, in the seventh embodiment, the fuel, which is relieved from each branch passage portion 124e, 7124e to the communication passage portion 7125a of the release passage 7125, can be fed to the branch passage portion 7125b, the cam receiving chamber 120, the common passage portion 124b, each branch passage portion 124c, 3124c having only the upstream part 124cu, and each internal pressure variable chamber 121 in this order. Thus, the suction passage 7124 of the seventh embodiment supplies the fuel to each pressurizing chamber 122a, 3122a while the suction passage 7124 bypasses the cam receiving chamber 120 and each internal pressure variable chamber 121 at the location on the upstream side of the corresponding branch passage portion 124e, 7124e, which forms the communicating connection relative to the release passage 7125.
According to the seventh embodiment discussed above, in the suction passage 7124 that bypasses the cam receiving chamber 120, which receives the drive cam 15 for driving each of the plungers 162, at the location on the upstream side of each communicating connection of the suction passage 7124 relative to the release passage 7125, it is less likely that foreign objects, which are generated through the driving of the plungers 162, are mixed into the fuel. Thus, it is possible to limit the deterioration in the backflow generation alleviating effect that would be caused by clogging of the release passage 7125 with the foreign objects mixed into the fuel in the suction passage 7124. As a result, the energy loss can be limited for a relatively long period of time.
Furthermore, according to the seventh embodiment, in the suction passage 7124 that bypasses each internal pressure variable chamber 121, in which the internal pressure is increased and decreased upon the driving of the movable unit 16 including the plunger 162, at the location on the upstream side of the communicating connection of the suction passage 7124 relative to the release passage 7125, it is less likely that foreign objects, which are generated through the driving of the movable unit 16, are mixed into the fuel. Thus, it is possible to limit the deterioration in the backflow generation alleviating effect that would be caused by clogging of the release passage 7125 with the foreign objects mixed into the fuel.
As shown in
As discussed above, in the suction passage 124 of the eighth embodiment, in which the backflow of the fuel is limited by the respective backflow limiting valves 8018, it is possible to enhance the backflow generation alleviating effect besides the relieving function of the release passage 3125 for relieving the return fuel from the respective pressurizing chambers 122a, 3122a. Thus, the reliability with respect to the advantage of limiting the energy loss can be improved.
As shown in
In each flow restricting portion 9125a that has a reduced passage cross-sectional area at an intermediate part of the corresponding release passage 9125, which is located on the suction passage 124 side of the cam receiving chamber 120, this passage cross-sectional area is increased in comparison to the passage cross-sectional area of the flow restricting portion 127a of the drain passage 127. In other words, in the intermediate part of the drain passage 127, at which the flow restricting portion 127a is formed, the passage cross-sectional area is reduced in comparison to the passage cross-sectional area of the flow restricting portion 9125a of each release passage 9125.
In the ninth embodiment discussed above, the effects and advantages, which are similar to those of the first embodiment, can be achieved. Furthermore, in the ninth embodiment, the release passages 9125 are connected to the drain passage 127 through the cam receiving chamber 120, which receives the drive cam 15 for driving the plungers 162. In this way, the fuel, which is relieved from the pressurizing chamber 122a to the release passage 9125, can be further relieved to the cam receiving chamber 120, which has a relatively large volume, so that it is possible to reduce pressure pulsations generated in the flow of this fuel. Accordingly, it is possible to limit occurrence of an incident, in which the backflow generation alleviating effect at the suction passage 124 is interfered due to the fuel pressure pulsation, and thereby it is possible to limit the energy loss, which is caused by this interference.
Furthermore, according to the ninth embodiment, each flow restricting portion 9125a (serving as a release flow restricting portion) is formed by reducing the passage cross-sectional area of the corresponding portion of the corresponding release passage 9125 that is located on the suction passage 124 side of the cam receiving chamber 120 (i.e., on the side of the cam receiving chamber 120, at which the suction passage 124 is placed). Under this construction, the fuel of the pressurizing chamber 122a can be easily relieved into the cam receiving chamber 120, which has the lower internal pressure in comparison to the release passage 9125, through the release passage 9125. Thereby, the backflow generation alleviating effect for the fuel can be enhanced at the suction passage 124, so that the reliability with respect to the advantage of limiting the energy loss can be improved.
Furthermore, in the ninth embodiment, at least the portion of the drain passage 127, which is indirectly connected to each release passage 9125 through the cam receiving chamber 120, has the reduced passage cross-sectional area that is reduced in comparison to the passage cross-sectional area of the flow restricting portion 9125a of the release passage 9125. Specifically, the passage cross-sectional area of at least the portion of the drain passage 127, which can indirectly drain the fuel from each release passage 9125 through the cam receiving chamber 120, is reduced in comparison to the passage cross-sectional area of the flow restricting portion 9125a. Accordingly, the air, which is accumulated in the suction passage 124 and the pressurizing chambers 122a during the stop period (the non-operating period) of the low pressure fuel pump 4, is pressurized upon restarting of the operation of the low pressure fuel pump 4 and can be discharged into the release passages 9125, the cam receiving chamber 120, and the drain passage 127 in this order. Thus, it is possible to limit the deterioration in the fuel filling performance for filling the fuel into the pressurizing chambers 122a, which would be otherwise caused by interfering of the suctioning of the fuel into the suction passage 124 and the pressurizing chambers 122a by the accumulated air. Therefore, it is possible to limit the energy loss and the deterioration in the delivery performance of the fuel from each pressurizing chamber 122a.
In addition, in the high pressure fuel pump 9010 of the ninth embodiment, as shown in
As shown in
Here, like in the seventh embodiment, the suction passage 7124 supplies the fuel to each pressurizing chamber 122a, 3122a while the suction passage 7124 bypasses the cam receiving chamber 120 and each internal pressure variable chamber 121 at the location on the upstream side of the communicating connection of the suction passage 7124 relative to the release passage 10125. In this way, in a flow restricting portion 10125a that has a reduced passage cross-sectional area at the branch passage portion 7125b of the intermediate part of the release passage 10125, which is located on the suction passage 7124 side of the cam receiving chamber 120, the passage cross-sectional area of the flow restricting portion 10125a is increased in comparison to the passage cross-sectional area of the flow restricting portion 127a of the drain passage 127. In other words, in the intermediate part of the drain passage 127, at which the flow restricting portion 127a is formed, the passage cross-sectional area is reduced in comparison to the passage cross-sectional area of the flow restricting portion 10125a of the release passage 10125.
In the tenth embodiment discussed above, effects and advantages, which are similar to those of the seventh embodiment, can be achieved. Furthermore, in the tenth embodiment, the release passage 10125 is connected to the drain passage 127 through the cam receiving chamber 120, which receives the drive cam 15 for driving the plungers 162. In this way, a portion of the fuel, which is relieved from the pressurizing chamber 122a, 3122a to the release passage 10125, can be further relieved to the cam receiving chamber 120, which has the relatively large volume, so that it is possible to reduce the pressure pulsations generated in the flow of this fuel. Accordingly, it is possible to limit occurrence of the incident, in which the backflow generation alleviating effect at the suction passage 7124 is interfered due to the fuel pressure pulsation, and thereby it is possible to limit the energy loss, which is caused by this interference.
Furthermore, according to the tenth embodiment, the flow restricting portion 10125a (serving as the release flow restricting portion) is formed by reducing the passage cross-sectional area of the corresponding portion of the release passage 10125, which is located on the suction passage 7124 side of the cam receiving chamber 120. Under this construction, a portion of the fuel of the pressurizing chamber 122a, 3122a can be easily relieved into the cam receiving chamber 120, which has the lower internal pressure in comparison to the release passage 10125, through the release passage 10125. Thereby, the backflow generation alleviating effect for the fuel can be enhanced at the suction passage 7124, so that the reliability with respect to the advantage of limiting the energy loss can be improved.
Furthermore, in the tenth embodiment, at least the portion of the drain passage 127, which is indirectly connected to the release passage 10125 through the cam receiving chamber 120, has the reduced passage cross-sectional area that is reduced in comparison to the passage cross-sectional area of the flow restricting portion 10125a of the release passage 10125. Specifically, the passage cross-sectional area of at least the portion of the drain passage 127, which can indirectly drain the fuel from the release passage 10125 through the cam receiving chamber 120, is reduced in comparison to the passage cross-sectional area of the flow restricting portion 10125a. Accordingly, the air, which is accumulated in the suction passage 7124 and the pressurizing chambers 122a, 3122a during the stop period (the non-operating period) of the low pressure fuel pump 4, is pressurized upon restarting of the operation of the low pressure fuel pump 4 and can be discharged into the release passages 10125, the cam receiving chamber 120, and the drain passage 127 in this order. Thus, it is possible to limit the deterioration in the fuel filling performance for filling the fuel into the pressurizing chambers 122a, 3122a, which would be otherwise caused by interfering of the suctioning of the fuel into the suction passage 7124 and the pressurizing chambers 122a, 3122a by the accumulated air. Therefore, it is possible to limit the energy loss and the deterioration in the delivery performance of the fuel from each pressurizing chamber 122a, 3122a.
As shown in
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The embodiments of the present disclosure have been described. However, the present disclosure is not necessarily limited to these embodiments and may be applied to various other embodiments and combinations of the above embodiments and/or the various other embodiments within a scope of the present disclosure.
Specifically, in a first modification with respect to the first to third and ninth embodiments, the suction passage 5124 and the primary and secondary branch passage portions 124c, 3124c of the fifth embodiment may be used. In a second modification with respect to the first to third and ninth embodiments, the primary and secondary branch passage portions 124c, 3124c of the suction passage 6124 and the other primary and secondary branch passage portions 124d, 6124d of the suction passage 6124 of the sixth embodiment may be used.
In a third modification with respect to the first, second and fourth embodiments, the primary and secondary branch passage portions 124c, 3124c of the suction passage 7124 and the other primary and secondary branch passage portions 124e, 7124e of the suction passage 7124 of the seventh embodiment may be used. In a fourth modification with respect to the ninth and tenth embodiments, the primary and secondary branch passage portions 124c, 3124c each having both of the upstream part 124cu and the downstream part 124cl of the suction passage 124 of the first embodiment may be used.
In a fifth modification with respect to the first to third, fifth to seventh, ninth, tenth, fifteenth and sixteenth embodiments, as shown in
In a seventh modification with respect to the first, second and ninth embodiments, the time period of executing the delivery stroke in the one of the pressurizing chambers 122a may be partially or completely overlapped with the time period of executing the delivery stroke in the other one of the pressurizing chambers 122a. In an eighth modification with respect to the third to eighth and thirteenth embodiments, the time period of executing the delivery stroke in the one of the pressurizing chambers 122a, 3122a may be partially overlapped with the time period of executing the delivery stroke in the other one of the pressurizing chambers 122a, 3122a.
In a ninth modification with respect to the seventh and tenth embodiments, as shown in
In a tenth modification with respect to the seventh and tenth embodiments, as shown in
In an eleventh modification with respect to the seventh and tenth embodiments, as shown in
In a thirteenth modification with respect to the ninth, eleventh and twelfth embodiments, the release passages 9125 (i.e., the release passages 125 of the first embodiment), each of which does not have the flow restricting portion 9125a, may be used. In a fourteenth modification with respect to the first to sixteenth embodiments, the valve opening degree may be adjusted by the control valve 11 in the pre-stroke period ΔTp of the delivery stroke.
In a fifteenth modification with respect to the first to sixteenth embodiments, the valve opening degree may be changed by the control valve 11 at the pre-stroke period ΔTp of the delivery stroke and also the suction stroke. In a sixteenth modification with respect to the first to sixteenth embodiments, the passage cross-sectional area of the drain passage 127, 2127, 4127 at any location along the extent of the drain passage 127, 2127, 4127 (i.e., any location in a longitudinal direction, or a passage direction of the drain passage 127, 2127, 4127) may be reduced in comparison to the passage cross-sectional area of the release passage 125, 3125, 7125, 9125, 10125.
In a seventeenth modification with respect to the first to sixteenth embodiments, the mechanical pump or the electric pump, which is provided in the high pressure fuel pump 10, 2010, 3010, 4010, 5010, 6010, 7010, 8010, 9010, 10010, 11010, 12010, 13010, 14010, 15010, 16010, may be used as the low pressure fuel pump 4. In an eighteenth modification with respect to the first to sixteenth embodiments, the high pressure fuel pump 10, 2010, 3010, 4010, 5010, 6010, 7010, 8010, 9010, 10010, 11010, 12010, 13010, 14010, 15010, 16010 may be used in the fuel supply system 2 that supplies gasoline, which serves as the fuel, to a gasoline engine, which serves as the internal combustion engine 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-122433 | Jun 2017 | JP | national |
| 2018-4238 | Jan 2018 | JP | national |
This is a continuation application of U.S. application Ser. No. 15/962,210, filed Apr. 25, 2018, which claims priority to and incorporates herein by reference Japanese Patent Application No. 2017-122433 filed on Jun. 22, 2017 and Japanese Patent Application No. 2018-004238 filed on Jan. 15, 2018.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15962210 | Apr 2018 | US |
| Child | 17246804 | US |
