GB2290834A

GB2290834A - Inner cam type fuel injection pump having first and second passages for fuel inlet and outlet

Info

Publication number: GB2290834A
Application number: GB9512625A
Authority: GB
Inventors: Shunsuke Yasunishi; Naoyuki Tuduki; Kouichi Nagaya
Original assignee: Toyota Motor Corp; NipponDenso Co Ltd
Current assignee: Denso Corp; Toyota Motor Corp
Priority date: 1994-06-29
Filing date: 1995-06-21
Publication date: 1996-01-10
Anticipated expiration: 2015-06-21
Also published as: DE19523578A1; GB9512625D0; GB2290834B; DE19523578C2

Description

1 - 2290834 1 "INNER CAM TYPE FUEL INJECTION PUMP HAVING A ROTOR HAVING

FIRST AND SECOND PASSAGES FOR FUEL INLET AND OUTLET" The present invention generally relates to fuel injection pumps and, more particularly, to an inner cam type fuel injection pump suitable for diesel engines.

The inner cam type fuel injection pump has a rotor provided inside of an inner cam fixed to a housing.

The rotor rotates at one half of the rotational speed of an engine with which the fuel injection valve is associated. The rotor has a plunger movable in a radial direction of the rotor. The plunger is pressed via a roller and a roller shoe by a camming action of a cam surface formed on an inner surface of the rotor. Thus, the plunger reciprocates inside the rotor to pressurize the fuel supplied to a fuel injection nozzle.

More specifically, the plunger reciprocates in accordance with a change in height of the cam surface of the inner cam when the rotor is rotated relative to the housing. Accordingly, the fuel in a pump chamber provided on the inner side of the plunger is pressurized when the plunger moves toward the center of the rotor. This pressurization corresponds to an angular position of the rotor relative to the inner cam. The pressurized fuel is distributed to a fuel injection nozzle provided to each of the cylinders of a diesel engine when the cylinder is in a compression process, that is, the piston is in a compression stroke.

In the above-mentioned conventional fuel injection valve, a fuel inlet passage and a fuel outlet passage must be provided so as to introduce fuel into the pump chamber and to discharge the fuel from the pump 1 chamber. Additionally, it is preferable to provide a fuel spill passage so as to control injection timing of the fuel. That is, the fuel in the pump chamber can be pressurized only when the fuel spill passage is closed.

Japanese Laid-Open Patent Application No.61 96168 discloses an example of the conventional inner cam type fuel injection pump. This fuel injection valve has a rotor having a through hole, as a main fuel passage, extending from a pump chamber to an end of the rotor in a longitudinal direction of the rotor. The above-mentioned fuel inlet passage, fuel outlet passage and fuel spill passage are branched from the through hole. The fuel inlet passage, the fuel outlet passage and the fuel spill passage are open at an outer circumferential surface of the rotor, and a fuel supply port, a fuel discharge port and fuel unload port are provided at respective positions of a cylinder receiving the outer circumferential surface of the rotor.

In the above-mentioned conventional inner cam type fuel injection pump, since the main passage is provided by forming a through hole from an end of the rotor to the pump chamber, an opening of the through hole at the end of the rotor must be sealed by a plug. That is, the opening of the through hole at the end of the rotor should be eliminated if it is possible to form the main fuel passage without forming the through hole.

Additionally, since the fuel inlet passage, the fuel outlet passage and the fuel spill passage are separately provided in the rotor of the abovementioned fuel injection pump, the total length of the fuel passage increases. Thus, a relatively large dead volume of the fuel passage, which must be reduced as small as possible, is formed. If the dead volume is large, a good fuel 1 pressurizing efficiency cannot be obtained.

Accordingly, as mentioned above, there is a problem in that the conventional fuel injection pump does not satisfy the requirements for cost reduction and performance optimization.

It is a general object of the present invention to provide an improved and useful fuel injection pump in which the above-mentioned problem is eliminated.

A more specific object of the present invention is to provide an inner cam type fuel injection pump having a rotor which has an inlet passage and an outlet passage for fuel, at least a part of the inlet passage being commonly used as a part of the outlet passage so as to minimize total length of the fuel passages. 15 Another object of the present invention is to provide an inner cam type fuel injection pump having a rotor which has a fuel passage leading to a pump chamber, the fuel passage not needing a seal plug to close an end of the fuel passage. 20 Another object of the present invention is to provide an inner cam type fuel injection pump having a rotor which has a spill passage having a minimum length. In order to achieve the above- mentioned objects, there is provided according to one aspect of the present invention an inner cam type fuel injection pump comprising a rotor and a cylinder receiving the rotor, said rotor having a pump chamber in which fuel is pressurized and a fuel inlet port and a fuel outlet port provided on an outer circumferential surface thereof each of which communicates with said pump chamber, said cylinder rotatably supporting said rotor and having at least one fuel supply port and at least one fuel outflow port, fuel being introduced into said pump chamber at charge stroke 1 through said fuel supply port and fuel inlet port, and fuel pressurized in said pump chamber being discharged at discharge stroke through said fuel outflow port and fuel outlet port, said inner cam type fuel injection pump being characterized in that:

each of said fuel inlet port and said fuel outlet port communicates with said pump chamber via a first fuel passage and/or a second fuel passage, said first fuel passage connecting said fuel inlet port to said fuel outlet port, said second fuel passage connecting said pump chamber to one of said fuel inlet port and said fuel outlet port.

Additionally, there is provided according another aspect of the present invention an inner cam type fuel injection pump comprising a rotor and a cylinder receiving the rotor, said rotor having a pump chamber in which fuel is pressurized and a fuel inlet port and a fuel outlet port provided on an outer circumferential surface thereof each of which communicates with said pump chamber, said cylinder rotatably supporting said rotor and having at least one fuel supply port and at least one fuel outflow port, fuel being introduced into said pump chamber at charge stroke and fuel pressurized in said pump chamber being discharged at discharge stroke, said rotor comprising a fuel passage communicating with said fuel outlet port and said cylinder further comprising a fuel spill passage communicating with said fuel passage so that a part of fuel pressurized in said pump chamber is returned to a fuel tank via said fuel passage and said fuel spill passage, said inner cam type fuel injection pump being characterized in that:

said fuel passage is formed as an annular groove provided on an outer circumference surface of said rotor; 1 and said rotor has a first portion and a second portion having a diameter smaller than that of said first portion so that said fuel outlet port and said annular groove are provided on said second portion.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

FIG.1 is a cross-sectional view of an embodiment of an inner cam type fuel injection pump according to the present invention; FIG.2 is a cross-sectional view taken along line II-II of FIG.1; FIG.3 is a cross-sectional view of an example of a rotor provided in an inner cam type fuel injection pump; FIG.4 is a cross-sectional view of a rotor provided in the inner cam type fuel injection pump shown in FIGA; FIG.5 is a cross-sectional view of a variation of the rotor shown in FIGA; and FIG.6 is a cross-sectional view of another variation the rotor shown in FIG.4.

A description will now be given, with reference to FIG.1, of an entire structure of the inner cam type fuel injection pump 10 according to the present invention.

In FIG.1, the fuel injection pump 10 comprises a housing 11 as a main body. The housing 11 accommodates each part of the fuel injection pump 10 including a fuel chamber 12 in which fuel is filled. An overflow valve 20 a spill valve 30, a fuel return valve 40, an accumulator 50 and a constant pressure valve 60 are connected to the housing 11.

1 The overflow valve 20 communicates with the fuel chamber 12 so as to prevent the fuel chamber 12 from being over pressurized. The overflow valve 20 has a check valve comprising a ball valve 22 and a spring 24 pressing the ball valve 22. The overflow valve 20 returns fuel in the fuel chamber 12 to a fuel tank when an excessive amount of fuel is supplied. In this embodiment, an opening pressure 2 of the overflow valve is about 0.8kg/cm The spill valve 30 comprises a solenoid valve in which a valve body 32 is moved by an electromagnetic force generated by an electromagnetic coil 31. The spill valve controls communication between the fuel return valve 40 and a fuel inlet gallery 17. The valve body 32 of the spill valve 30 is biased upwardly, and an upper end thereof abuts an end of a rod 34 and a stopper 36 which is biased by a spring 35. The rod 34 transmits the electromagnetic force generated by the electromagnetic coil 31 to the valve body 32.

When the valve body 32 is seated on a valve seat 37, that is, when the spill valve 30 is closed, fuel pressure is applied only to a side surface of the valve body 32. On the other hand, when the valve body 32 is separated from the valve seat 37, the pressure of the fuel is applied to a bottom surface of the valve body 32 as well as the side surface thereof. That is, when the rod 34 presses the valve body 32 due to the electromagnetic force generated by the electromagnetic coil 31, the valve body 32 is moved toward the valve seat 37 against a biasing force of the spring 33. Thus, the valve body 32 is seated on the valve seat 37 to move the spill valve 30 to a closed position. When the electromagnetic force exerted on the rod 34 is released, the valve body 32 is moved upwardly by the biasing force of the spring 33 1 against the biasing force of the spring 35. Thus, the spill valve 30 is moved to an open position. At this position, since pressure of the fuel is applied to the end surface of the valve body 32, a larger opening is obtained as the pressure of the fuel is higher.

The return valve 40 is provided for returning fuel discharged from the spill passage when the spill valve is open by appropriately reducing the pressure of the fuel to be returned. The return valve 40 comprises, similarly to the spill valve 30, a ball valve 42 and a spring 44 biasing the ball valve 42.

The accumulator 50 is provided for eliminating pulsation of the fuel in the fuel inlet gallery 17. The accumulator 50 comprises a piston 52 and a spring 54 which biases the piston 52. The piston 52 is displaced in accordance with a pressure change in the fuel in the fuel chamber 12 communicating with the fuel inlet gallery 17.

The constant pressure valve 60 is provided between a fuel outflow port 102 and a fuel injection valve provided to each cylinder of the engine. When pressure of the fuel in the fuel outflow port 102 exceeds a predetermined pressure, the fuel is supplied to the fuel injection valve therethrough. The constant pressure valve 60 maintains the pressure of fuel on the fuel injection valve side at a predetermined pressure if the pressure of the fuel in the fuel outflow port 102 is reduced less than the predetermined pressure.

In the fuel chamber 12 of the housing 11, there is provided a driving shaft 70, a vane type fuel feed pump (hereinafter simply referred to as a fuel feed valve) 80, a rotor 90, a cylinder 100 and a cam ring 110. The driving shaft 70 is rotated at a speed of one half of the rotational speed of the crank shaft of the engine. The 1 fuel feed pump 80 is driven by the driving shaft 70 to feed fuel to the fuel chamber 12. The rotor 90 is also driven by the drive shaft 70. The rotor has a large diameter portion and a small diameter portion. The small diameter portion of the rotor is received by the cylinder 100. The cam ring 110 surrounds the large diameter portion of the rotor 90.

The drive shaft 70 is rotatably supported in the housing 11 by a bushing 13 and a ball bearing 14. The bushing 13 is provided an end of the housing 11, and the ball bearing 14 is provided inside the housing 11. In order to reduce a friction force between the bushing 13 and the driving shaft 70, fuel is supplied to a gap formed between the bushing 13 and the drive shaft 70. The fuel is supplied to the gap from a fuel inlet 15 via a passage 16. Additionally, an oil seal 18 is provided adjacent to the end of the bushing 13 which faces outside so as to prevent leakage of the fuel supplied to the gap.

A pulsator 120 having a plurality of protrusions 121 is fitted on the end of the drive shaft 70 which is positioned inside the housing 11. Additionally, an angular displacement sensor 122 is attached to the cam ring 110. The angular displacement sensor 122 senses proximity of each of the protrusions 121 and outputs a pulse signal. That is, in the present embodiment. an angular displacement of the drive shaft 70 and, therefore angular displacement of the rotor 90 is measured by counting the number of pulse signals output from the angular displacement sensor 122.

The fuel feed pump 80 comprises a vane pump having an outer wall attached to the housing 11 and a rotor 83 having a plurality of vanes 82. The fuel supplied from an inlet port 84 communicating with the fuel 1 inlet 15 is pressurized by means of vanes 82 rotated by the rotor 83. The pressurized fuel is discharged through a fuel outlet port 85.

The rotor 90 is rotatably supported by the cylinder 100, and coupled to the driving shaft 70. The rotor 90 has a pump chamber 91 inside the large diameter portion. The smaller diameter portion of the rotor 90 has a first fuel passage 94 and a second fuel passage 95. The first fuel passage communicates a fuel inlet port 92 to a fuel outlet port 93. The second fuel passage 95 communicates the fuel inlet port 92 to the pump chamber 91. Four plungers 96a to 96d (refer to FIG.2) are provided in the pump chamber 91. The plungers reciprocate in radial directions of the rotor 90. Additionally, an annular groove 97 is formed on an outer circumferential surface of the rotor 90. The annular groove 97 is slightly displaced from the fuel outlet port 93 in the axial direction of the rotor 90.

The cylinder 100 has six fuel supply ports 101 (only two of them are shown in FIG.1) and six fuel outflow ports 102 (only one of them is shown in FIG.1). Each of the fuel supply ports 101 is opened at an inner surface of the cylinder 100, and communicates with the fuel inlet gallery 17 which communicates with the fuel discharge port 85 of the fuel feed pump 85. Each of the fuel outflow ports 102 is open at the inner surface of the cylinder and communicates with the constant pressure valve 60. The number of the fuel supply ports 101 and the number of the fuel outflow ports 102 correspond to the number of cylinders provided in the engine. In this embodiment, the number of cylinders is six. Accordingly, when the rotor 90 is rotated in synchronization with a rotation of the crank shaft of the engine, the fuel inlet gallery 17 1 communicates with the fuel inlet port 92 of the rotor 90, and the fuel outlet port 93 communicates, in turn, with the constant pressure valves 60.

A spill passage 103 is provided in the cylinder 100 so as to provide communication between the annular groove 97 formed on the outer circumferential surface of the rotor 90 and the spill valve 30. Since the annular groove 97 is formed circumferentially, the annular groove 97 is always in communication with the spill valve 30 regardless of the angular position of the rotor 90.

A description will now be given, with reference to FIG.2, of the structure of the pump chamber 91 and adjacent parts thereto.

The fuel injection pump 10 pressurizes the fuel by means of the four plungers 96a to 96d which are provided in the rotor 90 and driven by cams formed on the cam ring 110. Since the fuel injection pump 10 is associated with the engine having six cylinders, six cams are formed on an inner surface of the cam ring 110 in a uniform interval as shown in FIG.2. The cams are positioned so that the plungers 96a to 96d are moved inwardly at the same time. Rollers 99a to 99d are provided on outer ends of the plungers 96a to 96d via roller shoes 98a to 98d, respectively, so that the ends of the plungers 96a to 96d smoothly slide on the cams.

In the above-mentioned construction, while the rotor 90 is rotated one turn, each of the plungers 96a to 96d reciprocates six times. That is, while the crank shaft of the engine is rotated two turns, six pressurizations of fuel are carried out at a uniform interval. During this period, the fuel supply ports 101 are communicated to the fuel inlet port 92 when the plungers 96a to 96d are not moved inwardly by the cam 1 acting. The fuel outflow ports 102 are communicated to the fuel outlet ports 93 immediately before the plungers 96a to 96d are moved inwardly by the cam action.

When one of the fuel supply ports 101 communicates to the fuel inlet port 92, a centrifugal force and a pressure of the fuel supplied by the fuel feed pump 80 are applied to each of the plungers 96a to 96d. Thus, the fuel is introduced into the pump chamber 91. Thereafter, the communication between one of the fuel supply ports 101 and the fuel inlet port 92 is interrupted. Then, the plungers 96a to 96d are moved inwardly by the cam action so that one of the fuel outflow ports 102 is communicated to the fuel outlet port 93. Accordingly, if the spill valve 30 is closed, the fuel pressurized by the plungers 96a to 96d is supplied to the constant pressure valve 60.

If the spill valve 30 is open when the fuel is pressurized by the plungers 96a to 96d, the fuel discharged from the pump chamber 91 returns the fuel tank via the spill valve 30. Accordingly, the pressure of the fuel does not become high and, thus, the fuel is not supplied to the cylinders of the engine through the constant pressure valve 60. That is, if the spill valve 30 is not provided, a period of injection of fuel to each of the cylinders is determined only by a cam profile of the cam ring 100. This results in less freedom in controlling the period of fuel injection. On the other hand, when the spill valve 30 is provided as is in the present embodiment, fuel injection is not performed as long as the spill valve 30 is open even when the fuel is pressurized in the pump chamber 91. Accordingly, a start time for injection of fuel can be controlled by controlling switching of the spill valve 30 from an open 1 position to a closed position. Additionally, an end time of the injection of fuel can be controlled by controlling switching of the spill valve 30 from the closed position to the open position.

As mentioned above, in the present embodiment, the annular groove 97 is provide on the rotor 90. The spill passage 103 is provided in the cylinder 100, and the spill valve 30 is provided to control communication of the spill passage 103. This is to provide the above-mentioned control of a period for injection of fuel.

In order to control the period of injection of fuel with great accuracy, the amount of fuel spilled by the spill valve 30 should be as much as possible. This may be achieved by increasing the cross section of the valve body 32, or increasing stroke of the valve body 32.

However, this results in an increase in size of the spill valve 30 and a longer response time of the spill valve 30.

In the present embodiment, the above-mentioned problems are eliminated by providing the spring 33 which biases the stopper 36 for the valve body 32. That is, degree of opening of the spill valve 30 is greater as the pressure of the fuel is increased. Accordingly, by using the spill valve 30, an effective spill operation can be performed at an initial stage of a spill operation without increasing in size of the spill valve 30 and increasing in the response time.

In the spill operation performed by the spill valve 30, a negative pressure may be generated in the first fuel passage 94 and the second fuel passage 95 due to inertia of the fuel flowing into the spill valve 30.

If this condition happens, the amount of fuel introduced into the pump chamber 91 is varied, resulting in decrease in accuracy of the amount of fuel to be injected. In 1 order to eliminate this problem, a portion of the fuel to be returned to the fuel tank is returned to the fuel inlet gallery 17. Additionally, the accumulator 50 is provided which communicates with the fuel inlet gallery 17. That is, if an excessive amount of fuel is spilled due to inertia, a portion of the fuel is returned to the fuel inlet gallery 17 to increase the pressure therein, and a pulsation generated due to the return of the fuel is absorbed by the accumulator 50. Thus, a sufficient amount of fuel can always be introduced into the pump chamber 91.

In addition to the above-mentioned construction, the fuel injection pump 10 has a timer device 130 which varies an angular position of the cam ring 110 relative to the housing 11. That is, the cam ring 110 is rotatably provided in the housing 11, and receives a rod 133 which is interposed between timer pistons 131 and 132. The timer pistons 131 and 132 are slidable in the timer device 130. In FIG.2, a high pressure chamber 134 communicating with the fuel discharge port 85 of the fuel feed pump 80 is formed on the right side of the timer piston 131. A low pressure chamber communicating with the fuel inlet port 84 of the fuel feed pump 80 is formed on the left side of the timer piston 132. A spring 136 is provided in the low pressure chamber 135 to bias the timer piston 132 toward the right in FIG.2. The high pressure chamber 134 and the low pressure chamber 135 communicate each other via a conduit (not shown in the figures). Communication between the low pressure chamber 134 and the high pressure chamber 135 is controlled by a solenoid valve 140 shown in FIG.1. The cam ring 110 is rotated in accordance with a pressure difference between the low pressure chamber 134 and the high pressure chamber 135. In this embodiment, an angular displacement of the cam ring 110 is controlled by 1 a duty ratio control of the solenoid valve 140.

According to the above-mentioned construction of the timer device 130, an angular position of the cam ring 110 relative to an angular position of the rotor 90, that is, the crank shaft of the engine, can be changed. Accordingly, timing control for injecting fuel can be changed in addition to the action of the spill valve 30.

In a fuel injection pump using a plunger to pressurize fuel, such as the fuel injection pump 10 according to the present invention, a higher efficiency for delivering pressurized fuel is obtained as speed of the plunger is increased. In order to increase the speed of the plunger, a sharp profile cam must be used. However, the profile of the cam is limited so as to obtain smooth movement of the plunger. Accordingly, the speed of the plunger cannot be increased without limitation.

In order to increase the efficiency for delivering pressurized fuel, it is effective to minimize a pressure loss generated in fuel passages. This means that a dead volume, which is an unnecessary volume, should be eliminated to increase the efficiency for delivering pressurized fuel.

FIG.3 shows an example of the rotor 90 which can be used for the fuel injection pump 10. The rotor 90 shown in FIG.3 has a main fuel passage 150 which is bored from the left end (as shown in the drawing) of the rotor 90. The main fuel passage 150 passes through the pump chamber 91 and extends to a middle of the smaller diameter portion of the rotor 90. A branch passage 151 extends from the main fuel passage 150 toward a position corresponding to the fuel supply ports 101. A branch passage 152 extends from the main fuel passage 150 toward a position corresponding to the fuel spill passage 103. A 1 fuel outlet port 153 is provided which communicates with the fuel outflow port 102 when the rotor 90 is at a predetermined angular position. An annular groove 153 is provided which communicates with the branch passage 152.

A fuel outlet groove 154 is extended from a portion of the annular groove 153 to connect the annular groove 154 to the fuel inlet ports 102.

When the rotor is rotated to a predetermined position in which the branch passage 151 matches one of the fuel supply ports 101, the pump chamber 91 communicates with the fuel supply port 101 via the branch passage 151 and a part of the main fuel passage 150.

Thus, fuel is introduced into the pump chamber 91. When the rotor is rotated to a predetermined angular position at which the fuel outlet groove 154 matches one of the fuel outflow ports 102, the pump chamber 91 communicates with the fuel outflow port 102 via the branch passage 150, the branch passage 152, and the annular groove 153. Thus, fuel is discharged toward the constant pressure valve 60.

The pump chamber 91 is always communicated with the spill passage 103 via the main fuel passage 150 and the annular groove 154 regardless of the angular position of the rotor 20. Accordingly, a control of a period for injecting fuel can be performed by the spill valve 30.

In the rotor 90 shown in FIG.3, there is a dead volume in passages for fuel as compared to the rotor 90 shown in FIG.4. Additionally, in the rotor shown in FIG.3, a seal plug 155 must be provided to seal an end of the main fuel passage 150 A description will now be given of the rotor 90 shown in FIG.4 used to the fuel injection pump shown in FIG.1. The rotor 90 shown in FIG.4 has a first fuel passage 94 and a second fuel passage 95 instead of the 1 main fuel passage 150 and the branch passages 151 and 152.

The first fuel passage 94 is provided to directly communicate the fuel outlet port 93 to the fuel inlet port 92. The second fuel passage 95 is provided to directly connect the fuel inlet port 92 to the pump chamber 91.

Additionally, the first fuel passage 94 and the second fuel passage 95 are straight. In this construction, the second fuel passage 95 is commonly used as an inlet passage and an outlet passage. Accordingly, no passage is needed other than the first fuel passage 94 and the second fuel passage 95. This configuration of the passages for fuel is considered to have a minimum length in total and, thus, a dead volume is substantially eliminated.

The first fuel passage 94 can be formed by boring from either the fuel inlet port 92 or the fuel outlet port 93. The second fuel passage is formed by boring from the fuel inlet port 92 toward the pump chamber 91. Accordingly, a sealing means like the seal plug 155 provided in the rotor 90 shown in FIG.3 is not needed for the rotor 90 shown in FIG.4. Accordingly, the number of parts and assembling processes are reduced while efficiency for delivering pressurized fuel is increased.

A description will now be given of a variation of the rotor 90 shown in FIG.4. FIG.5 is a cross sectional view of a rotor 160 which is a variation of the rotor 90 shown in FIG.4.

The rotor 160 has the configuration the same as that of the rotor 90 shown in FIG.4 except that the diameter of a portion to which an annular groove 161 and the fuel outlet port 93 are provided is made smaller than a portion to which the fuel inlet port 92 is provided.

According to this configuration, a length of the annular groove 161 is shorter than the annular groove 97 of the 1 rotor 90 shown in FIG.4. Accordingly, the total length of the fuel passages of the rotor 160 is shorter than that of the rotor 90 shown in FIG.4 and, thus, the efficiency for delivering pressurized fuel is further increased.

It should be noted that, as shown in FIGA, 4 and 5, the fuel passage from the fuel inlet port to the constant pressure valve 60 is formed along a straight line so that the fuel inlet port 92, the fuel outlet port 93 and the fuel outflow port 101 are aligned on a straight line. This minimizes pressure losses generated in the fuel passage. Although, in the present embodiment, the fuel inlet port 92 is

communicated to the pump chamber 91 by the second fuel passage 95, the fuel outlet port 93 may be communicated to the pump chamber 91 when the fuel outlet port 93 is positioned closer to the pump chamber 91 than the fuel inlet port 92.

In this case, the fuel supply port 101 is eliminated as shown in FIG.6. The spill passage 103 serves as the fuel supply port, and the annular groove 97 or 161 is used as the fuel inlet port.

The present invention is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present invention.

- 18

Claims

1 WE CLAIM:

1. An inner cam type fuel injection pump comprising a rotor and a cylinder receiving the rotor, said rotor having a pump chamber in which fuel is pressurized and a fuel inlet port and a fuel outlet port provided on an outer circumferential surface thereof each of which communicates with said pump chamber, said cylinder rotatably supporting said rotor and having at least one fuel supply port and at least one fuel outflow port, fuel being introduced into said pump chamber at charge stroke through said fuel supply port and fuel inlet port, and fuel pressurized in said pump chamber being discharged at discharge stroke through said fuel outflow port and fuel outlet port, said inner cam type fuel injection pump being characterized in that:

2. The inner cam type fuel injection pump as claimed in claim 1, characterized in that said fuel inlet port is provided closer to said pump chamber than said 1 fuel outlet port and said second fuel passage is provided between said fuel inlet port and said pump chamber.

3. The inner cam type fuel injection pump as claimed in claim 1 or 2, characterized in that each of said first fuel passage and said second fuel passage comprises a straight opening.

4. The inner cam type fuel injection pump as claimed in any one of claims 1 to 3, characterized in that said second fuel passage is formed by boring from one of said fuel inlet port and said fuel outlet port.

5. The inner cam type fuel injection pump as claimed in any one of claims 1 to 4, wherein said rotor further comprises an annular groove on an outer circumferential surface communicating with said fuel outlet port and said cylinder further comprises a fuel spill passage communicating with said annular groove so that a part of fuel pressurized in said pump chamber is returned to a fuel tank via said annular groove and said fuel spill passage, said inner cam type fuel injection pump being characterized in that:

said rotor has a first portion and a second 1 portion having a diameter smaller than that of said first portion so that said fuel outlet port and said annular groove are provided on said first portion.

6. An inner cam type fuel injection pump comprising a rotor and a cylinder receiving the rotor, said rotor having a pump chamber in which fuel is pressurized and a fuel inlet port and a fuel outlet port provided on an outer circumferential surface thereof each of which communicates with said pump chamber, said cylinder rotatably supporting said rotor and having at least one fuel supply port and at least one fuel outflow port, fuel being introduced into said pump chamber when said fuel inlet port connects with said fuel supply port and fuel pressurized in said pump chamber being discharged when said fuel outflow port connects with said fuel outlet port, said rotor further comprising a fuel passage communicating with said fuel outlet port and said cylinder further comprising a fuel spill passage communicating with said fuel passage so that a part of the fuel pressurized in said pump chamber is returned to a fuel tank via said fuel passage and said fuel spill passage, said inner cam type fuel injection pump being characterized in that: said fuel passage is formed as an annular groove provided on an outer circumferential surface of said rotor; and 30 said rotor has a first portion and a second portion having a diameter smaller than that of said first portion so that said fuel outlet port and said annular groove are provided on said second portion.

1

7. The inner can type fuel injection pump as constructed and arranged to operate as substantially hereinbefore described with reference to and as illustrated in the accompanying drawings of FIGS.1, 2, 4 and 5.