GB2291138A

GB2291138A - Fuel injection pump having a bearing assembled without play

Info

Publication number: GB2291138A
Application number: GB9512781A
Authority: GB
Inventors: Toshio Fujimura; Noboru Watanabe; Toshikazu Watanabe; Tadashi Nishiwaki; Masato Tsuzuki
Original assignee: Toyota Motor Corp; NipponDenso Co Ltd
Current assignee: Denso Corp; Toyota Motor Corp
Priority date: 1994-07-08
Filing date: 1995-06-22
Publication date: 1996-01-17
Anticipated expiration: 2015-06-22
Also published as: DE19524676C2; GB9512781D0; GB2291138B; DE19524676A1; JPH0821330A

Description

1 "FUEL INJECTION PUMP HAVING A BEARING ASSEMBLED WITHOUT PLAY" The

present invention generally relates to fuel injection pumps and, more particularly, to a fuel injection pump which pumps fuel by means of a rotation of a rotor which is rotatably supported by a bearing in ahousing.

Japanese Laid-Open Patent Application No.62- 265423 discloses a fuel injection pump having a rotor which rotates to pump fuel. The pumping of the fuel is performed by a plunger which is reciprocated by a camming action of an inner cam provided around a rotor which receives the plunger. An end of the plunger contacts a can provided on an inner surface of the inner cam. The plunger is displaced in a radial direction of the rotor by pump the fuel by suction and discharge stroke of the plunger.

In the above-mentioned fuel injection pump, a driving shaft transmits rotational force from an engine so as to rotate the rotor. The driving shaft is rotatably supported by a radial bearing provided in the housing. The radial bearing is assembled by press fitting an inner race of the radial bearing onto an outer surface of the driving shaft and by press fitting an outer race of the radial bearing into the housing. In this construction, once the drive shaft is assembled in the housing together with the radial bearing, it is difficult to remove them from the housing. However, each part of the fuel injection pump must be easily disassembled in order to provide proper maintenance.

In order to achieve an easy disassembling, the bearing may be loosely fitted into the housing instead of 1 press fitting it. However, if the bearing is loosely fitted, the bearing may have play, i.e., unwanted movement, relative to the drive shaft and the housing. Accordingly, there is a problem in that smooth rotation of the driving shaft and the rotor connected to the driving shaft is not achieved, resulting in a decrease in a service life of the fuel injection pump.

It is a general object of the present invention to provide a fuel injection pump in which the above- discussed problem is eliminated.

A more specific object of the present invention is to provide a fuel injection pump in which a bearing rotatably supporting a drive shaft connected to a rotor has no play during pump operation and the bearing is is capable of being easily removed from a housing and the drive shaft.

In order to achieve the above-mentioned object, there is provided a fuel injection pump comprising a driving shaft and a first housing member and a second housing member. The drive shaft is rotatably supported by a bearing and the second housing member assembled to the first housing member so as to define a space in which the drive shaft and the bearing are accommodated, the fuel injection pump being characterized in that:

the bearing is positioned substantially between the first housing member and the second housing member, a first side of the bearing facing the first housing member and a second side of the bearing facing the second housing member, the bearing being fit on the drive shaft and being fit to one of the first housing member and the second housing member, wherein the fit of the bearing, the drive shaft and one of the first housing member and the second housing member; and 1 fixing means provided for fixing the bearing to one of the first housing member and the second housing member so that the bearing is removable from one of the first housing member and the second housing member.

In one embodiment of the present invention, the fixing means is an elastic member provided between the bearing and one of the first housing member and the second housing member. The elastic member is compressed when the second housing member is assembled to the first housing member so as to press the bearing to the first housing member or the second housing member. The elastic member may be an annular wave washer provided between an outer circumferential surface of the bearing and an inner surface of the first housing member. 15 In one embodiment, an adjusting screw is provided on the first housing member. The adjusting screw presses an outer circumferential surface of the bearing and the elastic member is positioned substantially opposite to the adjusting screw. 20 In one embodiment of the present invention, the bearing is fastened onto one of the first housing member and the second housing member by a screw. In one embodiment of the present invention the fixing means comprises a screw and an elastic member. The elastic member is fastened to one of the first housing member and the second housing member. A portion of the elastic member presses the bearing against the one of the first housing member and the second housing member.

In one embodiment of the present invention, the fixing means comprises a taper provided on an outer circumferential surface of the bearing and a corresponding taper provided on one of the first housing member or the second housing member.

1 In one embodiment of the present invention, the fixing means comprises a tapered surface provided on an outer circumferential surface of the bearing and an elastic member provided in a space defined by the tapered surface, the second housing member and an inner surface of the first housing member.

In one embodiment of the present invention, the fixing means comprises the bearing which includes an outer race, an inner race and rollers rolling between a first surface of the outer race and a second surface of the inner race. The first surface and the second surface are slanted with respect to the rotational axis of the bearing. The rollers have a cylindrical shape.

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

FIG.1 is a cross-sectional view of a first embodiment of a fuel injection pump according to the present invention; FIG.2 is a cross-sectional view taken along a line II-II in FIG.1; FIG.3 is an enlarged cross-sectional view of a part of the first embodiment of the fuel injection pump according to the present invention; FIG.4 is a cross-sectional view of a part of a second embodiment of the fuel injection pump according to the present invention; FIG.5A is a cross-sectional view of a part of a third embodiment of the fuel injection pump according to the present invention; FIG.5B is a cross-sectional view taken along a line B-B in FIG. 5A; FIG.6 is an enlarged cross-sectional view of a 1 part of a fourth embodiment of the fuel injection pump according to the present invention; FIG.7 is an enlarged cross-sectional view of a part of a fifth embodiment of the fuel injection pump according to the present invention; FIG.8 is an enlarged cross-sectional view of a part of a sixth embodiment of the fuel injection pump according to the present invention; FIG.9 is an enlarged cross-sectional view of a part of a seventh embodiment of the fuel injection pump according to the present invention; FIG.10 is an enlarged cross-sectional view of a part of an eighth embodiment of the fuel injection pump according to the present invention; FIG.11 is an enlarged cross-sectional view of a part of an ninth embodiment of the fuel injection pump according to the present invention; FIG.12 is an enlarged cross-sectional view of a part of a tenth embodiment of the fuel injection pump according to the present invention; FIG.13 is an enlarged cross-sectional view of a part of a eleventh embodiment of the fuel injection pump according to the present invention; FIG.14 is an enlarged cross-sectional view of a part of a twelfth embodiment of the fuel injection pump according to the present invention; and FIG.15A is an enlarged cross-sectional view of a part of a thirteenth embodiment of the fuel injection pump according to the present invention; FIG.15B is an illustration for explaining forces generated in a bearing shown in FIG. 15A.

A description will now be given, with reference to FIG.1, of an entire structure of the inner cam type

1 fuel injection pump 1 according to the present invention.

In FIG.1, the fuel injection pump 1 comprises a housing 10 as a main body. The housing 10 accommodates each part of the fuel injection pump 1 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 and a constant pressure valve 60 are connected to a discharge head 11.

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.

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 1 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 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 - 8 1 the predetermined pressure.

In the fuel chamber 12 of the housing 10, 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.

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 10 by a bushing 13 and a ball bearing 14. The bushing 13 is provided an end of the housing 10, and the ball bearing 14 is provided inside the housing 10. 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 10. 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, 1 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 10 and a rotor 83 having a plurality of vanes 82. The fuel supplied from an inlet port 84 communicating with the fuel inlet is 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 1 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 is rotated in synchronization with a rotation of the crank shaft of the engine, the fuel inlet gallery 17.

communicateswith 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 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 1 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 1 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 1 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 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 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 110. This results in less freedom in 1 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 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.

1 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 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 1 has a timer device 130 which varies an angular position of the cam ring 110 relative to the housing 10. That is, the cam ring 110 is rotatably provided in the housing 10, 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 30 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 1 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 can 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 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 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. 15 A more detailed description will now be given, with reference to FIG.3 which is an enlarged crosssectional view of a part of the first embodiment of the fuel injection pump according to the present invention. Since many parts, such as the drive shaft 70, 20 the rotor 90 and the can ring 110, are accommodated in a space defined by the housing 10 (corresponding to a first housing member) and a discharge head 11, the discharge head 11 (corresponding to a second housing member) is required to be easily removed from the housing 10 for maintenance. The radial ball bearing 14 is also required to be easily removed from the housing 10. Accordingly, in this embodiment, and also in all other embodiments described below, the radial ball bearing 14 is assembled by being loosely fitted into the housing 10 instead of having a tight press fit.

When the plungers 96a to 96d are pressed by the cam ring 11-0, a uniform pressing force is not always applied to the plungers 96a to 96d due to tolerance in 1 dimensions of related parts of the pump. Accordingly, a side force is exerted on the rotor 90. Additionally, when a highly pressurized fuel is directed to the fuel outlet port 93, a reaction force, which is also a side force, is exerted on the rotor 90. If the radial ball bearing 14 is merely loosely fitted onto the drive shaft 70 and is loosely fitted into the housing 10, there a small gap exists between the drive shaft 70 and the radial ball bearing 14 and also between the radial ball bearing 14 and the housing 10. Accordingly, the rotor 90 and the drive shaft 70 may vibrate during an operation due to the abovediscussed side forces.

In the present embodiment, the play of the radial ball bearing 14 relative to the housing 10 is eliminated by providing an elastic member 5 between a side surface of the radial ball bearing 14 and the discharge head 11. When the discharge head 11 is assembled to the housing 10, the elastic member 5 is compressed. The radial ball bearing 14 is pressed by an elastic force of the elastic member 5. Thus, movement of the radial ball is restricted. In this construction, there is no play of the radial ball bearing 14 and, thus, smooth rotation of the drive shaft 70 and the rotor 90 is achieved while maintaining easy removal of the drive shaft 70 and the radial ball bearing 14.

It should be noted that although the elastic member 5 is provided between the side surface of the radial ball bearing 14 and the discharge head 11, the elastic member 5 may instead be provided between a side surface of the radial ball bearing 14 and the housing 10. In this embodiment, the elastic member 5 is made of a nonmetallic material such as rubber. Alternatively, the elastic member may be in the form of a metal spring member 1 such as a wave washer or a C-cross section ring.

A description will now be given, with reference to FIG.4, of a second embodiment of the fuel injection pump according to the present invention. In FIG.4, parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted. The second embodiment has a construction which is the same as that of the first embodiment except for the elastic member 5.

In the second embodiment, the elastic member 5 of the first embodiment is replaced by the 0-ring 8. The 0-ring 8 is provided between the side surface of the radial ball bearing 14 and the discharge head 11. The radial ball bearing 14 is securely fixed to the housing 10 is by a pressing force generated by the 0-ring 8. Accordingly, the 0-ring 8 not only eliminates the play of the radial ball bearing 14 but also provides a seal between the discharge head 11 and the housing 10. In this embodiment, the same effect as in the first embodiment can be achieved while the same number of parts is maintained.

A description will now be given, with reference to FIGS.5A and 5B, of a third embodiment of the fuel injection pump according to the present invention. In FIGS.5A and 5B, parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted. The second embodiment has a construction the same as that of the first embodiment except for the elastic member 5.

In the third embodiment, the elastic member 5 of the first embodiment is substituted by a wave washer 150. That is, the wave washer 150 is provided between an outer circumferential surface of the radial ball bePring 14 and the housing 10. The play of the radial ball bearing 14 is 1 eliminated due to the radial ball bearing 14 being securely fixed to the housing 10 by an elastic force exerted by the wave washer 150. Additionally, the wave washer 150 serves to absorb tolerance variations of the inner diameter of the housing 10. Thus, a high degree of precision in machining the housing 10 is not required.

A description will now be given, with reference to FIG.6, of a fourth embodiment of the fuel injection pump according to the present invention. The view of FIG.6 corresponds to the view shown in FIG.5B. In FIG.6, parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted. The fourth embodiment has a construction the same as that of the third embodiment except for the wave washer 150.

In the fourth embodiment, elastic members 151 and 152 are provided betweenan outer circumferential surface of the radial ball bearing 14 and the housing 10.

Additionally, an adjusting screw 153 is provided exteriorly of the housing 10 so as to press the radial ball bearing 14. The radial ball bearing 14 is supported by the two elastic members 151 and 152 and the screw 153.

The radial ball bearing 14 is securely fixed to the housing 10 by the pressing forces of the elastic members 151 and 152. Thus, there is no play of the radial ball bearing 14 relative to the housing 10. In this embodiment, a stronger pressing force can be obtained as compared with the third embodiment using the wave washer 150. Thus, further smoothing of the rotation of the shaft 70 can be achieved.

A description will now be given, with reference to FIG.7, of a fifth embodiment of the fuel injection pump according to the present invention. In FIG.7, parts that 1 are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

The fifth embodiment has a construction the same as that of the first embodiment except that an outer race of the radial ball bearing 14 is fixed to the housing 10 by screws 161 instead of an elastic member such as the. elastic member 5. In this construction, the radial ball bearing 14 can be securely fixed to the housing 10 with a high degree of accuracy while permitting easy removal simply by unfastening the screws 161.

A description will now be given, with reference to FIG.8, of a sixth embodiment of the fuel injection pump according to the present invention. In FIG.8, parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

The sixth embodiment has a construction the same as that of the fifth embodiment except that the outer race of the radial ball bearing 14 is fixed to the discharge head 11, instead of the housing 10, by the screws 161. In this construction, the radial ball bearing 14 can be securely fixed to the discharge head 11 with a high degree of accuracy while permitting easy removal simply by unfastening the screws 161.

A description will now be given, with reference to FIG.9, of a seventh embodiment of the fuel injection pump according to the present invention. In FIG.9, parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

The seventh embodiment has a construction the same as that of the fifth embodiment except that an outer 1 race of the radial ball bearing 14 is fixed to the housing 10 by fixing screws 163 via an elastic member 162 instead of the screws 161 which directly fixes the radial ball bearing 14 to the housing 10. That is, the fixing screws 5 163 fasten the elastic member 162 to the housing 10 so that the elastic member 162 is interposed between the head of the screen and the housing 10 and pressed against the side surface of the radial ball bearing 14. In this construction, the radial ball bearing 14 can be securely fixed to the housing 10 in a highly accurate position, and is easily removed by unfastening the fixing screws 162. In this embodiment, tolerance variation in the dimensions of a portion of the housing 10 in the axial direction of the drive shaft 70, which receives the radial ball bearing 14, can be absorbed by the elasticity of the elastic member 162. Thus, high degree of accuracy is not required during machining the housing 10.

A description will row be given, with reference to FIG.10, of an eighth embodiment of the fuel injection pump according to the present invention. In FIG.10, parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

The eighth embodiment has a construction the same as that of the seventh embodiment except that an outer race of the radial ball bearing 14 is fixed to the discharge head 11 instead of the housing 10. That is, the fixing screws 163 fasten the elastic member 162 to the discharge head 11 so that the elastic member 162 is pressed against the side surface of the radial ball bearing 14. In this embodiment, the radial ball bearing 14 can be securely fixed to the discharge head 11 in an accurate position as in the prior embodiment, and is 1 easily removed by unfastening the fixing screws 162. In this embodiment, tolerance variations in the portion of the discharge head 11 extending in the axial direction of the drive shaft 70, which receives the radial ball bearing 14, can be absorbed by the elasticity of the elastic member 162. Thus, great accuracy is not required for machining the discharge head 11.

A description will now be given, with reference to FIG.11, of a ninth embodiment of the fuel injection pump according to the present invention. In FIG.11, parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

The ninth embodiment has a construction the same as that of the first embodiment except that the elastic member 5 is not provided and instead the radial ball bearing 14 is fitted onto the drive shaft 70 by means of a taper fitting. More specifically, an inner surface of an inner race 14b of the radial ball bearing 14 is tapered, and a portion of the drive shaft 70, onto which portion the radial ball bearing 14 is fitted, is correspondingly tapered. The discharge head 11 contacts the side surface of the outer race 14a so as to press the radial ball bearing 14 in the axial direction of the drive shaft 70.

When the outer race of the radial ball bearing 14 is pressed by the discharge head 11, the radial ball bearing 14 moves toward the larger diameter side of the taper. Thus, the inner race of the radial ball bearing 14 is expanded radially outwardly due to the taper action and, thereby, the outer race is expanded outwardly. Accordingly, the play of the radial ball bearing 14 is eliminated by pressing the discharge head 11 to the outer race of the radial ball bearing 14 when the discharge head 1 is assembled to the housing 10.

In this construction, the radial ball bearing 14 can be removed easily when the discharge head 11 is removed from the housing because the radial ball bearing 14 is not fastened by a separate mechanical means. In this embodiment, no additional part such as an elastic member or a fixing member is needed and, thus, the play of the radial ball bearing is eliminated by a simple construction.

A description will now be given, with reference to FIG.12, of a tenth embodiment of the fuel injection pump according to the present invention. In FIG.12 parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions is thereof will be omitted.

In this embodiment, the outer race of the radial ball bearing 14 is taper fitted to the housing 10. When the outer race is pressed by the discharge head 11, the outer race is compressed radially inwardly due to the taper action. Thus, the inner race is compressed radially inwardly. Accordingly, the play of the radial ball baring 14 is eliminated when the discharge head 11 is pressed toward the radial ball bearing 14.

A description will now be given, with reference to FIG.13, of an eleventh embodiment of the fuel injection pump according to the present invention. In FIG.13 parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

This embodiment has a construction the same as that of the tenth embodiment except that the taper is provided between the outer race of the radial ball bearing 14 and the discharge head 11 instead of the housing 10.

1 That is, the outer race of the radial ball bearing 14 is taper fitted to the discharge head 11. When the outer race is pressed by the discharge head 11, the outer race is compressed radially inwardly due to the taper action.

Thus, the inner race is compressed radially inwardly. Accordingly, the play of the radial ball baring 14 is eliminated when the radial ball bearing 14 is pressed by the discharge head 11.

A description will now be given, with reference to FIG.14, of a twelfth embodiment of the fuel injection pump according to the present invention. In FIG.14 parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

In this embodiment, the outer race of the radial ball bearing 14 is tapered. An elastic member 170 is provided in a space between the tapered portion of the outer race of the radial ball bearing 14 and the housing 10. The elastic member 170 contacts the end of the discharge head 11 so that the elastic member 170 is compressed when the discharge head 11 is assembled to the housing 10. Accordingly, the outer race of the radial ball bearing 14 is compressed radially inwardly by the taper action. Thus, the play of the radial ball baring 14 is eliminated when the discharge head 11 is pressed to the radial ball bearing 14.

A description will now be given, with reference to FIGS.15A and 15B, of a thirteenth embodiment of the fuel injection pump according to the present invention.

In FIGS.15A and 15B parts that are the same as the parts shown in FIGS.1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

In this embodiment, a roller bearing 180 is used 1 to rotatably support the drive shaft 70. The roller bearing 180 comprises an outer race 180a, an inner race 180b and rollers 180c which are slantingly interposed between the outer race 180a and the inner race 180b. That is, an inner circumferential surface of the outer race 180a, i.e., the surface on which the rollers 180c roll, is tapered. Similarly, a circumferential surface of the - inner race 180b, on which surface the rollers 180c roll, is tapered. The rollers 180c are tapered forward to the right direction shown in the figure.

In the roller bearing 180, a circumferential length of the circumferential surface of the outer race 180a decreases toward the side on which the discharge head 11 is located. Similarly, a circumferential length of the circumference surface of the inner surface 180b decreases toward the side on which the discharge head 11 is located.

Accordingly, when the rollers 180c roll between the circumferential surfaces of the outer race 180a and the inner surface 180b, the left side part of each of the rollers 180c, which left side part is opposite from the discharge head 11, must roll faster than the right side.

In operation, each of the rollers 180c tends to move toward the left direction as shown by arrow A in FIG.15B.

As a result, when the roller bearing 180 is in operation, the inner race 180b is pressed by the rollers 180c toward the left, and the outer race 180a is moved toward right due to a reaction force. That is, the outer race 180a is pressed against the discharge head 11 and the inner race 180b is pressed against the housing 10. Accordingly, the play of the roller bearing 180 is eliminated when iring operation.

Additionally, since the outer race 180a and the inner race 180b have tapered surfaces, if the outer race 1 180a moves relative to the inner race 180b, the outer race 180a slightly expands radially and the inner race 180b slightly compresses radially. Accordingly, play of the roller bearing 180 can be eliminated by pressing the outer race 180a against the discharge head 11 when it is assembled to the housing 10.

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

Claims

1 WE CLAIM:

1. A fuel injection pump comprising a driving shaft and a first housing member and a second housing member, said drive shaft rotatably supported by a bearing, said second housing member assembled to said first housing member so as to define a space in which said drive shaft and said bearing are accommodated, said fuel injection pump being characterized in that:

said bearing is positioned substantially between said first housing member and said second housing member, a first side of said bearing facing said first housing member and a second side of said bearing facing said second housing member, said bearing being fit on said drive shaft and being fit to one of said first housing member and said second housing member, wherein said fit of said bearing provides play between said bearing, said drive shaft and one of said first housing member and said second housing member; and fixing means is provided for fixing said bearing to one of said first housing member and said second housing member so that said bearing is removable from one of said first housing member and said second housing member.

2. The fuel injection pump as claimed in claim 1, characterized in that said fixing means is an elastic 1 member provided between said bearing and one of said first housing member and said second housing member.

3. The fuel injection pump as claimed in claim 2, characterized in that said elastic member is provided between a side surface of said bearing and said second housing member, said elastic member being compressed by said second housing member being secured to said first housing member.

4. The fuel injection pump as claimed in claim 2, characterized in that said elastic member is provided in a space defined by a side surface of said bearing, said second housing member and an inner surface of said first housing member, said elastic member being compressed and providing a seal between said first housing member and said second housing member.

5. The fuel injection pump as claimed in claim 2, characterized in that said elastic member is provided between an outer circumferential surface of said bearing and an inner surface of said first housing member.

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6. The fuel injection pump as claimed in claim 5, characterized in that said elastic member is an annular wave washer.

7. The fuel injection pump as claimed in claim 5, characterized in that said fixing means further comprising an adjusting screw provided in said first housing member, said adjusting screw pressing said outer circumferential surface of said bearing, said elastic member positioned substantially opposite to said adjusting screw.

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8. The fuel injection pump as claimed in claim 1, characterized in that said fixing means is a screw for fixing said bearing to one of said first housing member and said second housing member.

9. The fuel injection pump as claimed in claim 1, characterized in that said fixing means comprises a screw and an elastic member, said elastic member fixed to one of said first housing member and said second housing member, a portion of said elastic member pressing said bearing against the one of said first housing member and said second housing member.

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10. The fuel injection pump as claimed in claim 1, characterized in that said fixing means comprises a taper provided on an outer circumferential surface of said bearing and a corresponding taper provided on one of said first housing member and said second housing member.

11. The fuel injection pump as claimed in claim 1, characterized in that said fixing means comprises a tapered surface provided on an outer circumferential surface of said bearing and an elastic member provided in a space defined by said tapered surface, said second housing member and an inner surface of said first housing member.

12. The fuel injection pump as claimed in claim 1, characterized in that said fixing means comprises said bearing which includes an outer race, an inner race and rollers rolling between a first surface of said outer race and a second surface of said inner race, said first surface and said second surface being slanted with respect to the rotational axis of said bearing, said rollers having a tapered cylindrical shape.

13. The 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 through 15B.