INNER-CAM TYPE DISTRIBUTION FUEL INJECTION PUMP

Abstract: An inner-cam type distribution fuel injection pump has a lubricating system (42, 43) for lubricating the interior of a cam chamber (32) defined by an inner cam (14) and a rotor (7) with a lubricating oil having a viscosity higher than the viscosity of fuel oil. The pump is structured to prevent the fuel oil from leaking into the lubricating oil.

Description: The present invention relates to an inner-cam type distribution fuel injection pump and, more particularly, to an inner-cam type distribution fuel injection pump actuated by an inner cam having an inner peripheral cam profile, wherein lubricating condition is improved in a cam chamber which is formed by the inner cam and a rotor rotatable in the inner cam. Fuel economy is a current social need which has given rise to the demand for fuel injection pumps capable of injecting fuel at higher levels of pressures. To cope with this demand, in the fields of distribution type fuel injection pump for diesel engines, a pump actuating mechanism has been proposed which employs an inner cam which has an inner peripheral cam surface in place of ordinary face cam having an outer peripheral cam surface. An example of this type of fuel injection pump actuating mechanism is disclosed in Japanese Patent Unexamined Publication No. 61-96168. This type of fuel injection pump has a rotor having a radial bore which slidably receives a plunger. As the rotor rotates, the plunger is driven by the cam profile on the inner peripheral surface of the cam so as to reciprocatingly move within the radial bore thereby sucking, pressurizing and injecting fuel. In general, the rotor can have a plurality of such radial bores and plungers so that this type of fuel injector is suitable for attaining a high fuel injection pressure. Recently, attempts have been made to use a composite fuel composed of kerosene and alcohol, instead of light oil which has been conventionally used as a diesel engine fuel oil. Obviously, a higher fuel injection pressure requires the fuel injection pump to work under severer conditions and, hence, improved durability of fuel injection pump is becoming a critical demand. More specifically, the increased fuel injection pressure of the fuel injection pump actuated by an inner cam naturally increases the pressure at which the plungers are urged against the cam profile of the inner cam, resulting in a significant increase in the load applied to the inner cam, rollers which are held in sliding contact with the inner cam and roller shoes which rotatably carry the rollers. In conventional fuel injection pumps of the type described, the lubrication in cam chamber accommodating these sliding parts has relied solely upon the fuel. Such a lubricating method, however, cannot provide a required lubricating effect particularly when the pump operates under a heavy load, i.e., at a high injection pressure. Thus, wear of the sliding parts tend to grow rapidly due to inferior lubricating condition, causing unfavorable effect on the pump characteristic and durability of the pump. Furthermore in document US-A-4 662 825 there has been disclosed a generic pump for supplying pressurized fuel. In the case of this fuel supplying pump, it is provided that fuel leaking past the plunger is returned to the transfer pump, a leaking-through of fuel into the lubricating system can particularly not be avoided reliably when the fuel pump operates under the condition of heavy load, i.e. under a high injection pressure. This is always a major disadvantage when a dilution of the lubricant oil cannot be tolerated. It is the object of the invention to provide an inner-cam type distribution fuel injection pump, wherein the interior of the cam chamber accomodating the inner cam and the rotor is lubricated with a lubricant having a higher viscosity than the fuel injected, thus providing a lubricating condition good enough to enable the fuel injection pump to operate under a heavy load. This problem is solved by the features of claim 1. According to the features in the characterizing part of claim 1, the low-pressure fuel passage leads through a pressure control valve to a low-pressure side of the fuel feed pump so as to maintain the pressure in said low-pressure fuel passage at a level equal to or slightly higher than the pressure in a lubricant passage leading to the low-pressure lubricant chamber. Due to this arrangement, a leaking-through of fuel into the lubricating system of the fuel injection pump is also prevented effectively under the conditions of a high injection pressure. In operation, the rotor of the fuel supply pump is driven by the drive shaft relative to the inner cam so that the plungers, which are received in an oil-tight manner in the radial bores formed in the rotor, reciprocatingly move within the radial bores as the outer ends of the plungers follow the cam profile on the inner peripheral surface of the cam as a result of rotation of the rotor, whereby the fuel is sucked, pressurized and injected. In addition, the interior of the cam chamber defined by the inner cam and the rotor is lubricated by a lubricating oil which has a viscosity higher than that of the fuel. The sliding parts such as the inner cam, rollers, roller shoes and plungers are, therefore, satisfactorily lubricated even when the pump works under a high pressure. This contributes to an improvement in the durability of the fuel injection pump and facilitates the use of composite fuels such as a mixture of kerosene and alcohol. In addition, the inner-cam type distribution fuel injection pump of the invention can be designed to prevent the lubricating oil in the cam chamber from coming into the fuel through the fuel collection passage, as is the case of the arrangement according to the second and third aspects of the invention, thus suppressing tendency for the fuel filters to clog. The subclaims 2 to 7 include advantageous further developments of the invention. The features and advantages of the present invention will become more apparent from the following description of the preferred embodiments with reference to the accompanying drawings. Fig. 1 is a schematic sectional view of a first embodiment of a inner-cam type distribution fuel injection pump in accordance with the present invention. Fig. 2 is a sectional view taken along line II-II in Fig. 1; Fig. 3 is a side elevational view of a portion of the fuel injection pump showing particularly a roller and a roller shoe; Fig. 4 is a sectional view taken along line IV-IV in Fig. 3; Fig. 5 is a sectional view of a different example of a timer; Fig. 6 is a sectional view of a pressure control valve incorporated in the first embodiment; Fig. 7 is a sectional view of a modification of the pressure control valve; and Fig. 8 is a schematic sectional view of a second embodiment of the inner-cam type fuel injection pump in accordance with the present invention. The construction and operation of the fuel injection pump of the present invention will be fully understood from the following description of the preferred embodiments. Fig. 1 is a schematic sectional view of a first embodiment of the inner-cam type fuel injection pump designed for use in a diesel engine, while Fig. 2 is a sectional view taken along line II-II in Fig. 1. As will be seen from these figures, this embodiment of the fuel injection pump is of solenoid-actuated spill control type and is provided with a fuel feed pump 1. The construction of this fuel injection pump will be outlined with referenced to the flow of the fuel. The feed pump 1 is designed to suck the fuel up from a fuel tank 2. The fuel suction line leading from the fuel tank 2 has a fuel filter 1A and a fuel booster pump 1B which can suck the fuel from the fuel tank 2 in such a manner as to compensate for a drop of the fuel pressure across the fuel filter 1A. The sucked fuel is then supplied to a pressure control valve 3 which controls the fuel pressure and subsequently into the gallery 5 within a head 4. The fuel in the gallery 5 is introduced into a plunger chamber 9 defined by plungers 8, through a passage 6a formed in a cylinder 6 and through a passage 7a formed in a rotor 7. The rotor 7 is received in the cylinder 6 for rotation in sliding contact therewith and is rotatably supported by bearings 10 so as to be driven by an engine which is not shown. A plurality of radial cylindrical bores 7A are formed in the rotor 7 and open in the outer peripheral surface of the rotor 7. Each plunger 8 carries at its radially outer end a roller shoe 12 which in turn rotatably carries a roller 13. An inner cam 14 having a cam contour or profile on the inner peripheral surface thereof receives the rollers 13. Since the plunger is always urged radially outward by the pressure of the fuel, the roller 13 on the outer end of each plunger 8 is always held in contact with the cam profile of the inner cam 14. Therefore, as the rotor 7 rotates, the roller 13 on each plunger 8 rolls on the cam profile on the inner peripheral surface of the inner cam 14 so that the roller 13 performs a reciprocating motion in the radial direction. This movement of the roller 13 is transmitted to an associated plunger 8 through the roller shoe 12. When the plunger 8 moves radialy outwardly of the rotor 7, the volume of the space behind the plunger is increased to suck the fuel. Thus, the radially outward movement of the plunger 8 corresponds to the suction stroke of the pump. Conversely, a radially inward movement of the plunger 8 is performed by radially inward movement of the roller 13. The positional relationship between the passage 6a in the cylinder 6 and the passage 7a in the rotor 7 is so determined that the communication between both passages is established during a suction stroke in which the plunger moves towards the inner periphery of the inner cam 14 and is interrupted during a pressurizing stroke. The rotor 7 is further provided with a spill port 15 and a discharge port which communicates with the plunger chamber 9. These passages are brought into communication with passages 17 and 18 formed in the cylinder 6 during a discharge stroke of the plunger 8. Solenoid-actuated spill valve 19 is provided at the end of the passage 17 so as to selectively bring the passage 17 into communication with the gallery 5. The spill valve 19 is adapted to be driven by an electronic control unit (ECU) 22 in accordance with a signal indicative of the state of operation of the engine, e.g., a signal from throttle opening sensor 20 or a signal from a crank angle sensor 21. The passage 18 in the cylinder 6 is communicated with the delivery valve 24 through a passage 23 and further with an injection nozzle, i.e., a fuel injector, on the engine through a pipe not shown. In operation, as the rotor 7 rotates by the power derived from the engine, each plunger 8 repeatedly conducts suction strokes in which it suckes fuel through the gallery 5 and the pressurizing strokes in which it pressurizes and delivers fuel to fuel injectors through the delivery valve 24. In synchronization with the stroking of the plungers 8, the solenoid-actuated spill valve 19 controls the timing of spill, i.e., the rate of fuel injection. The timing of fuel injection thus performed is adjustable by timer means. Namely, the inner cam 14 is connected to a timer piston 26 through a slide pin 25 so that it is rotationally displaced by the timer piston so that the phase of the cam 14 is shifted to vary the timing of operation of the plungers and, hence, the timing of injection of the fuel. As shown in Fig. 2, a high pressure fuel chamber 27 is formed on one end of the timer piston 26 and connected to the gallery through the passage 28. A low pressure chamber 29 is formed on the other end of the timer piston 26 and accommodates a spring 30 which urges the timer piston 26 towards the pressure chamber 27. The low-pressure chamber 29 is communicated through a communication hole 31 in the timer piston 26 with a low-pressure lubricant chamber, or cam chamber 32 accomodating the inner cam 14. Therefore, the position of the timer piston 26 is determined by the balance between the forces acting on the timer piston 26 in the opposite directions, i.e., the force generated by the pressure in the pressure chamber 27 and the force which is the sum of the force produced by the spring 30 in the low-pressure chamber 29 and the force generated by the low pressure existing in the low-pressure chamber 29. The pressure chamber 27 of the timer is in communication with the gallery 5 and is adapted to receive the fuel the pressure of which has been regulated by the pressure control valve 3. The pressure determined by the pressure control valve 3 becomes higher as the engine speed increases, so that the timer piston 26 is progressively moved towards the low-pressure chamber 29 in accordance with the rise of the engine speed. A description will be made hereinunder of the construction and operation for lubricating the sliding parts in the cam chamber 32. Each plunger 8 is provided in the sliding surface thereof with an annular groove 34 which serves as a leak fuel collecting passage. Another annular groove 35 serving as a leak fuel collection passage is formed in a portion of the sliding surface of the cylinder 6 between the passage 7a and the cam chamber 32. Furthermore, an annular groove 36 serving as a leak fuel collection groove is formed in a portion of the sliding surface of the timer piston 26 adjacent to the pressure chamber 27. These leak fuel collection grooves 34, 35 and 36 are connected to the fuel suction side of the fuel feed pump 1, i.e., to the low-pressure side of the fuel feed pump, through low-pressure fuel passages 37, 38, 39 and 40. The cam chamber 32 is lubricated in a manner explained below. The cam chamber 32 is supplied with a lubricating oil from a lubricating system of the engine (not shown) through an orifice 41. A part of the lubricating oil is introduced into the space between a pair of bearings 10 which support the rotor 7. The lubricating oil coming out of the gaps between the bearings 10 and the rotor 7 is introduced into the cam chamber 32 directly or indirectly through the passage 42. An oil outlet port 43 out is formed in an lower portion of the cam chamber 32 at the side of the inner cam 14 remote from the orifice 41. The lubricating oil, which is introduced through an oil inlet 43 in via the orifice 41 lubricates the inner cam 14, rollers 13 and the roller shoes 12 so as to lubricate and cool these members. The oil is then discharged through the oil outlet 43. A high pressure is established in the plunger chamber 9 during an injection stroke. A part of pressurized fuel, therefore, leaks from the plunger chamber 9 into the cam chamber 32 through minute gaps between the plungers 8 and the rotor 7. Similarly, a part of fuel leaks into the cam chamber 32 through a minute gap between the rotor 7 and the cylinder 6. If the leaking fuel is allowed to flow into the cam chamber 32, the lubricating oil supplied into the cam chamber 32, which has a much higher viscosity than the fuel, is undesirably diluted and degraded. In the fuel injection pump of the described embodiment, however, the leaking fuel is caught in the leak fuel collection grooves 34 and 35 and does not flow beyond these collection grooves. Namely, since the leak fuel collection grooves 34 and 35 are communicated with the suction side of the feed pump 1, the pressure in these grooves 34 and 35 is almost the same as that in the cam chamber 32, so that no tendency exists for the fuel to flow from these grooves 34 and 35 into the cam chamber 32. It is thus possible to avoid undesirable dilution of the lubricating oil in the cam chamber 32 by the fuel. The pressure in the timer pressure chamber 27, which is controlled by the pressure control valve 3 as explained before, is higher than the pressure in the cam chamber 32. In consequence, the fuel tends to leak from the timer pressure chamber 27 into the cam chamber 32 through a minute gap between the timer piston 26 and the wall of the housing 44. The annular groove 36 in the wall of the housing 44 effectively collects this leaking fuel so as to prevent this leaking fuel from reaching the cam chamber 32. As will be understood from the foregoing description, it is possible to isolate the lubricating oil system from the fuel system almost completely by virtue of the annular grooves 34, 35 and 36, so that a good lubricating condition is always maintained in the cam chamber 32. The inner-cam type distribution fuel injection pump of the described embodiment is provided with an air vent hole 14a formed in a portion of the inner cam 14 near the top end of the inner can 14, as shown in Fig. 2. The position of the vent hole 14a may be freely selected within a region a (see Fig. 2) which is near the top end of the cam chamber 32 and which is devoid of crest of the cam contour. When a plunger has been rotated to this region a . the plunger 8 acting on the inner cam 14 receives the minimum load, so that no problem is caused in regard to the mechanical strength of the inner cam 14 and the roller 13 despite the presence of the vent hole 14a, even though the fuel injection pump is designed and constructed for a very high fuel injection pressure. As will be seen from Figs. 3 and 4, a vent hole 12a and an air vent groove 12b are formed in the roller shoe 12 rotatably carrying the roller 13 which rolls on the cam profile of the inner cam 14 in contact therewith. Trapping of air in the lubricating oil is inevitable because the lubricating oil has a viscosity which is much higher than that of the fuel oil. The vent hole 12a and the vent groove 12b formed in the roller shoe 12 effectively relieve the air trapped by the lubricating oil to the spacer in the upper portion of the cam chamber 32. Namely, air trapped by the lubricating oil and introduced into the roller shoe 12 is allowed to escape upwards through the air vent groove 12b so that the lubricating oil is continuously supplied into the area of sliding contact between the roller shoe 12 and the roller 13 through the communication hole 12a. This arrangement ensures that the roller can be adequately lubricated without any risk of cavitation. The air introduced into the cam chamber 32 is collected in the upper portion of the cam chamber 32 and is discharged through the vent hole 14a formed in the upper portion of the inner cam. The air is then relieved to the oil outlet 43 out. Therefore, any tendency for the roller 13 and the roller shoe 12 to trap air each time they pass the upper portion of the cam chamber 32 is eliminated to ensure good lubrication of the sliding surfaces of the roller 13 and the roller shoe 12. In the illustrated embodiment, although the inner cam 14 and the roller shoe 12 are both provided with vent hole or groove, the arrangement may be modified such that the vent hole or the vent groove is provided only in one of the inner cam 14 and the roller shoe 12. In the described embodiment, in order to ensure lubrication of all the portions of the cam chamber 32, the oil inlet port 43 in and the oil outlet port 43 out are disposed on the diametrically opposite sides of the inner cam 14. This means that a steady flow of lubricating oil is maintained across the inner cam 14 so that the inner cam 14 is effectively lubricated and cooled by fresh lubricating oil. Lubrication is ensured also in the gaps between the bearings 10 and the rotor 7 by virtue of the oil introduction hole which is provided between the pair of bearings 10. Thus, the bearings 10 can support the rotor 7 in improved lubricating condition. A description will be made hereinunder of another example of the timer with specific reference to Fig. 5. The timer shown in this figure employs a different arrangement for introducing the pressure medium into the pressure chamber 27 and the low-pressure chamber 29. In the timer described before, the fuel and lubricating oil are introduced into the pressure chamber 27 and the low-pressure chamber 29, respectively. Since the position of the timer piston 26 is controlled mainly by change in the pressure in the pressure chamber 27, a good response of the timer is obtained by introducing the fuel oil into the pressure chamber 27 because the fuel oil is less viscous and, hence, exhibits a higher controllability than the lubricating oil. In addition, since the pressure of the fuel oil is controlled by the pressure control valve 5 before it is introduced into the pressure chamber through the gallery 5, the pressure in the pressure chamber 27 is always controlled in accordance with the pump speed. On the other hand, the introduction of the lubricating oil into the low-pressure chamber 29 can be conducted simply by providing a communication hole in the timer piston 26. This timer can operate satisfactorily when the ambient temperature is not so low. However, when the ambient air temperature is low as in the case of the use of the engine in a cold district or winter season, the viscosity of the lubricating oil is increased to pose a greater resistance to the sliding movement of the timer piston 26, with the result that the response of the timer is seriously impaired. In order to obviate this problem, the timer shown in Fig. 5 is designed such that the low-pressure chamber 29 also receives the fuel oil. More specifically, in the timer shown in Fig. 5, the passage hole 31 used in the timer described before is eliminated so as to completely isolate the cam chamber 32 and the low-pressure chamber 29 from each other. In addition, an annular groove 45 is formed in the outer peripheral surface of the timer piston 26. The annular groove 45 communicates with the low-pressure chamber 29 through a passage 46. The low-pressure chamber 29 of the timer is therefore communicated with the suction side of the feed pump 1 through the passage 46, the annular groove 45, the annular groove 36 and the fuel passage 39, so that the fuel oil is introduced into the low-pressure chamber. Since the fuel oil generally exhibits only a small rise of viscosity when the temperature is lowered, as compared with lubricating oil, no substantial increase in the sliding resistance of the timer piston 26 is caused even when the air temperature is low, so that the timer can operate satisfactorily even when it is used at a low air temperature as in a cold district. Although the described embodiment of the fuel injection pump has a lubricating system which makes use of the lubricating oil supplied from the lubricating system of the engine, the fuel injection pump of the invention may have a lubricating system which makes use of a lubricating oil stagnant in the cam chamber, independently from the engine lubricating system. A spool valve as a pressure control valve 50 is provided between the fuel passage 40 and a lubricating oil passage 49 which leads to the lubricating oil outlet port 43 out. As shown in a greater scale in Fig. 6, the pressure control valve 50 has a main body 51 having a bore which slidably receives a spool 53. Liquid chambers 55 and 57 are defined on the respective ends of the spool 53. One 55 of these liquid chambers is communicated with the fuel passage 40 through a fuel port 59, while the other liquid chamber 57 communicates with the lubricating oil passage 49 through a lubricating oil port 61. A fuel discharge port 63 is formed in the side wall of the main part 51 of the pressure control valve 50 in communication with the fuel tank 2 through a fuel passage 40a. Similarly, a lubricating oil discharge port 65, which leads to an oil pan 64 through a lubricating oil passage 49a, is formed in the side wall of the main part 51 of the pressure control valve 50. The operation of the pressure control valve 50 is as follows: When the levels of the pressure acting on both sides of the spool 53 are equal, the spool 53 is maintained at a neutral position as illustrated so that both the fuel discharge port 63 and the lubricating oil discharge port 65 are kept closed by the spool 53, whereby the cam chamber 32 and the fuel passage 40 are isolated from the ambient air. Assuming that the pressure of the lubricating oil in the cam chamber 32 has risen to a level higher than the pressure of the fuel in the fuel passage 40, the spool 53 of the pressure control valve 50 is moved upwards as viewed in Fig. 1 so that the lubricating oil passage 49 is allowed to communicate with the lubricating oil discharge port 65 thereby establishing communication between the cam chamber 32 and the oil pan 64, whereby the lubricating oil in the cam chamber 32 is relieved to the oil pan 64 so as to lower the pressure in the cam chamber 32. In consequence, the pressure in the liquid chamber 57 comes down below the pressure of fuel in the liquid chamber 55, so that the spool 53 is moved downwards as viewed in the drawings. This operation of the spool 53 terminates when the levels of the pressure acting on both sides of the spool 53 are equalized, i.e., when the pressure of the lubricating oil in the cam chamber 32 has become equal to the pressure of the fuel in the fuel passage 40. In this state, the pressure in leak fuel collecting grooves such as the annular groove 36 becomes equal to the pressure in the cam chamber 32 so that any tendency for the lubricating oil to leak from the cam chamber 32 into the annular groove 36 through the minute gap between the piston pin 25 and the housing 44 is eliminated. In consequence, clogging of the fuel filter 1A which may otherwise be frequently caused by leakaged lubricating oil can be suppressed. Fig. 7 shows a modification 50A of the pressure control valve 50 of Fig. 6. In this modification, springs 80 and 82 having equal spring constants are disposed in both liquid chambers 55A and 57A so as to stabilize the movement of the spool 53. The pressure control valve 50A may be further modified such that the spring 80 in the liquid chamber 55A communicating with the fuel passage is omitted, while the spring 82 in the other liquid chamber 57A is used. Such a modification can function in the same manner as a check valve which is incorporated in a fourth embodiment of the invention which will be described hereinunder. The same effect is obtainable by designing the pressure control valve such that the pressure receiving area of the spool facing the space leading to the fuel passage is smaller than the area of the other pressure receiving surface. A second embodiment of the present invention will be described hereinunder with specific reference to Fig. 8 in which the same reference numerals are also used to denote the same or equivalent parts and detailed description of such parts or members is omitted. The second embodiment has a check valve 70 which is disposed in the fuel passage 40A for collecting the fuel and the fuel from this check valve 70 is returned to the fuel tank 2. On the other hand, the lubricating oil passage 49A for discharging lubricating oil from the cam chamber 32 is directly connected to the oil pan 64. Since the fuel passage 40A and the lubricating oil passage 49A are both opened to the atmosphere, the pressure levels are substantially the same at the ends of these passages 40A and 49A are both opened to the atmosphere, the pressure levels are substantially the same at the ends of these passages 40A and 49A near the ends thereof open to the atmosphere. However, since the fuel passage 40A has the check valve 70 while the passage 49A is devoid of such a check valve, the pressure in the fuel collecting passage such as annular groove is higher than the pressure of the lubricating oil in the cam chamber 32 by an amount corresponding to the force which is required to open the check valve against a spring thereof, whereby leak of the lubricating oil into the fuel passage is prevented. When the pressure of the fuel supplied by the feed pump 1 into the gallery 5 has been increased to a level higher tan a predetermined level, the pressure control valve 3 operates to return the fuel to the low-pressure side thereby lowering the fuel oil pressure to ordinary level. The pressurized fuel is returned to the annular groove 34 through the passage 40A, the passage 38, the annular groove 35 and the fuel passage 37, so that the fuel pressure in the annular groove 34 is raised to a level higher than the level of the lubricating oil pressure in the cam chamber 32. This undesirably tends to allow the fuel to leak from the annular groove 34 into the cam chamber 32. In this embodiment, however, the leak of the fuel into the cam chamber 32 is prevented by the check valve 70 which blocks the passage for any flow of fluid from the annular groove 34 into the cam chamber 32. If the pressure set to open the check valve 70 is too high, the fuel pressure in the annular groove 34 may rise to an abnormally high level, resulting in leakage of fuel from the annular groove 34 into the cam chamber 32. From this point of view, it is necessary that the opening pressure of the check valve 70 is set at a very low level. for instance, in order to limit the rate of leak of the fuel from the annular groove 34 into the cam chamber 32 to the order of several cubic centimeters per hour, the opening pressure of the check valve 70 should be set at about 0.1 ata.

Claims: An inner-cam type distribution fuel injection pump comprising: a fuel feed pump (1), an inner cam (14) disposed in a housing (44) and having an inner peripheral cam profile, a rotor (7) disposed in said inner cam (14) and driven by a drive shaft, at least one plunger (8) slidably received in a radial bore (7A) formed in said rotor (7), said plunger (8) being capable of moving reciprocatingly in said radial bore (7A) as the radially outer end of said plunger (8) slides on said cam profile thereby sucking, pressurizing and delivering a fuel, at least one high-pressure fuel chamber (9) defined by said at least one plunger (8) and said radial bore (7A), at least one low-pressure lubricant chamber (32) defined by said inner cam (14) and said rotor (7) and at least one annular groove (34) formed along the radial bore (7A) and communicating with a low-pressure fuel passage (40) characterized in that said low-pressure fuel passage (40) leads through a pressure control valve (50, 70) to a low-pressure side of said fuel feed pump (1) so as to maintain the pressure in said low-pressure fuel passage (40) at a level equal to or slightly higher than the pressure in a lubricant passage (49) leading to said low-pressure lubricant chamber (32). An inner-cam type distribution fuel injection pump according to claim 1, characterized in that said pressure control valve is a spool valve (50) for interconnecting said low-pressure fuel passage (40) and said lubricant passage (49) to equalize the levels of pressure in said low-pressure fuel passage (40) and said lubricant passage (49). An inner-cam type distribution fuel injection pump according to claim 1, characterized in that said pressure control valve is a check valve (70) disposed in said low-pressure fuel passage (40) and adapted to allow fuel to flow only to the low-pressure side of said fuel feed pump (1). An inner-cam type distribution fuel injection pump according to one of claims 1 to 3, further comprising a timer means (25, 26, 27, 29) disposed in said housing (44) and capable of rotationally displacing said inner cam (14), wherein said timer means (25, 26, 27, 29) includes a timer piston (26) slidably received in a bore formed in said housing (44), a slide pin (25) through which the movement of said timer piston (26) is transmitted to said inner cam (14), a second high pressure fuel chamber (27) formed on one end of said timer piston (26) and a second low-pressure chamber (29) formed on the other end of said timer piston (26) and adapted to be supplied with a low-pressure fluid, wherein a second annular groove (36) is formed in said housing (44) surface which is in sliding contact with said timer piston (36), said annular groove (36) communicating with said low-pressure fuel passage (40). An inner-cam type distribution fuel injection pump according to claim 4, characterized in that said second low-pressure chamber (29) is supplied with a lubricant from said low-pressure lubricant chamber (32), while said second high-pressure fuel chamber (27) receives the fuel of high pressure determined by the speed of rotation of said drive shaft. An inner-cam type distribution fuel injection pump according to claim 4, characterized in that said second low-pressure chamber (29) is supplied with fuel of a low pressure, while said second high-pressure fuel chamber (27) receives the fuel of high pressure determined by the speed of rotation of said drive shaft. An inner-cam type distribution fuel injection pump according to one of claims 4 to 6, characterized in that the quantity of injection of fuel by said fuel injection pump is controlled by causing the pressurized fuel in said high-pressure fuel chamber (27) to spill by the operation of a solenoid-actuated spill valve (19).

Inventors: HISHINUMA, OSAMU, INOUE, YUTAKA, KATO, NOBUO, MIYATA, YUKINORI, SHIBATA, AKIRA, TANAKA, FUMIAKI
Applicants: NIPPONDENSO CO., LTD.
Application year: 1988
Main classification: F02M41
IPC codes: F02M59, F02M41, F02M63