JPH0330597Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Field of Application] The present invention relates to a fuel injection timing control device for a distributed fuel injection pump equipped with an atmospheric pressure fluctuation compensation mechanism that corrects deterioration in ignition characteristics due to atmospheric pressure fluctuations. [Prior Art] In general, in a diesel engine, if the fuel injection timing is set to suit the conditions in which the atmospheric pressure is high, such as in a lowland, then the fuel injection timing is set to suit the conditions in which the atmospheric pressure is low, such as in a very high mountain. When operated, the air filling efficiency becomes low and the compression pressure inside the cylinder decreases, resulting in a decrease in the final temperature, which may impair ignition performance and cause a delay in ignition. Therefore, problems such as poor acceleration and generation of white smoke in the exhaust gas may occur. Therefore, it is necessary to make the injection timing of the fuel injection pump relatively earlier when the atmospheric pressure is low than when the atmospheric pressure is high to prevent ignition delay. As a fuel injection timing control device for a distributed fuel injection pump equipped with such an atmospheric pressure fluctuation compensation mechanism,
Conventionally, structures shown in FIGS. 3 and 4 have been proposed. That is, FIG. 3 shows the overall structure of a distribution type fuel injection pump, and in the figure, 1 is a drive shaft driven by a diesel engine. A drive shaft 1 drives a rotary feed pump 3 within a pump housing 2 and also rotates a plunger 4. The feed pump 3 introduces fuel from the fuel tank 5 and supplies it to a fuel chamber 6 within the pump housing 2. The fuel pressure within this fuel chamber 6 increases in accordance with the rotational speed of the engine, that is, the rotational speed of the feed pump 3. The plunger 4 is slidable in the axial direction via a coupling ring 7 and is directly connected to the drive shaft 1, and a face cam 8 as a control member for controlling the fuel injection timing is rotated integrally with the plunger 4. installed on. The plunger 4 is rotated by the cam roller 9 in rolling contact with the face cam 8.
is reciprocated a number of times during one revolution according to the number of cylinders in the engine. When the suction groove 10 formed at the tip of the plunger 4 communicates with the suction port 11 during the suction stroke of the plunger 4, the fuel in the fuel chamber 6 is sucked into the pressure pump chamber 13 through the introduction passage 12. plunger 4
When the fuel in the pressure pump chamber 13 is pressurized during the compression stroke, this pressurized fuel is guided to the communication passage 14 formed in the plunger 4, and when the supply port 15 communicates with the discharge port 16, the injection passage 17 to the injector 18 of the cylinder. Note that 19 is a delivery valve. When the adjuster steering lever 20, which is linked to the vehicle's accelerator, is rotated, the main spring 21
The tension lever 22 is rotated through the tension lever 22, and the spill ring 23 attached to the lower end of the tension lever 22 is moved in the axial direction on the surface of the plunger 4. This spill ring 23 opens and closes a spill port 24 formed in the plunger 4, and controls the amount of fuel supplied to the injector 18. In other words, in FIG. 3, when the spill ring 23 is moved to the right, the opening timing of the spill port 24 is delayed, so the amount of fuel supplied to the injector 18 is increased, and when the spill ring 23 is moved to the left, Since the opening timing of the spill port 24 is advanced, the amount of fuel supplied to the injector 18 is reduced. A drive gear 25 is attached to the drive shaft 1, and this drive gear 25 rotates a driven gear 26. When the rotational speed of the engine increases, the flyweight 27 attached to the driven gear 26 operates to apply thrust to the governor sleeve 28, which pushes the control lever 29. Since the control lever 29 is connected to the spill ring 23, the control lever 29 is connected to the spill ring 23.
Move to the left in the diagram. Therefore, these flyweights 27, governor sleeve 28, and control lever 29 automatically control the fuel injection amount according to the rotational speed of the engine. A cam roller 9 that rolls into contact with the face cam 8
is supported by a roller ring 31 via a roller pin 30. Roller ring 31 is rod 32
It is connected to the timer piston 33 by. As shown in FIG. 4, the timer piston 33 is slidably inserted into a timer cylinder 34 which also serves as a part of the atmospheric pressure compensating housing. a high pressure chamber 35 as an operating pressure chamber;
The pressure is divided into a low pressure chamber 36. The high pressure chamber 35 communicates with the fuel chamber 6 in the pump housing 2 through an orifice 37 formed in the timer piston 33. Furthermore, the low pressure chamber 36 communicates with the fuel tank 5 as a low pressure fuel reservoir via a return passage 38. Note that a timer spring 39 is accommodated in this low pressure chamber 36. This timer spring 3
9 always presses and biases the timer piston 33 toward the high pressure chamber 35 side. When the fuel pressure in the fuel chamber 6 of the pump housing 2 increases as the rotational speed of the engine increases, the fuel pressure in the high pressure chamber 35 also increases, so the timer piston 33 moves toward the low pressure chamber 36 side. This displacement is transmitted to the roller ring 31 by the rod 32. For this reason, the roller ring 31
is rotated in the circumferential direction to advance the cam roller 9 relative to the face cam 8. Therefore, the reciprocating timing of the plunger 4 is advanced, and as a result, the fuel injection timing is controlled. In addition, in FIG. 3, the timer piston 33
Although the axial direction is drawn in the left-right direction of the paper, it is actually arranged perpendicular to the paper. A bypass-like relief passage 40 connecting the high pressure chamber 35 and the low pressure chamber 36 is formed in the timer cylinder 34 . The passage area of the relief passage 40 is controlled by a flow control valve 41 serving as an atmospheric pressure compensation mechanism. To explain the atmospheric pressure compensation flow control valve 41, in FIG. 4, 42 is a bushing guide that forms a part of the atmospheric pressure compensation housing. Holes 43 and 44 are opened. These communication holes 43 and 44 are connected to the push rod 4.
The opening area of the annular groove 46 is controlled by the annular groove 46 formed in the groove 5 . pushyrod 45
is the oil seal 4 relative to the bushing guide 42.
7 to maintain air-liquid tightness, and is slidably inserted in the axial direction, and is constantly biased downward as shown in the figure by a spring 48. A cover 49 as part of the atmospheric pressure compensation housing is attached to the bushing guide 42.
An adjustment screw 50 is attached to the. A bellows 51 is stretched between the adjusting screw 50 and the push rod 45. The space outside this bellows 51 is the atmosphere sensing chamber 5.
2, and this atmosphere sensing chamber 52 is open to the atmosphere through an atmosphere introduction hole 53 formed in the cover 49. The internal space of the bellows 51 is filled with gas at a predetermined pressure. Therefore, due to the pressure difference between the inside and outside of the bellows 51, this bellows 5
1 expands and contracts, and slides the push rod 45 in the axial direction to control the opening area of the communication holes 43 and 44. Here, if the atmospheric pressure is high, such as when driving at low altitude,
Since the atmospheric pressure inside the atmospheric sensing chamber 51 is high, the bellows 5
1 is retracted and slides the push rod 45 downward in FIG. As a result, the communication holes 43, 44
The opening area of the timer cylinder 34 is increased from the high pressure chamber 35 to the low pressure chamber 36 through the relief passage 40.
The amount of fuel escaping to the side increases, causing the timer piston 33 to move relatively to the right in the drawing. Therefore, the cam roller 9 is kept on the retarded side relative to the face cam 8 via the roller ring 31, so that the fuel injection timing is not advanced. Further, when the atmospheric pressure is low, such as when traveling at high altitudes, the atmospheric pressure inside the atmospheric sensing chamber 52 is also low, so the bellows 51 is extended, causing the push rod 45 to slide upward in FIG. 4. As a result, the communication holes 43, 4
The opening area of the timer piston 3 is narrowed to reduce the amount of fuel escaping from the high pressure chamber 35 of the timer cylinder 34 to the low pressure chamber 36 side through the relief passage 40.
3 is moved relatively to the left in the drawing, and the cam roller 9 is moved relatively to the advance side with respect to the face cam 8 via the roller ring 31, thereby advancing the fuel injection timing. Therefore, with such a configuration, when the atmospheric pressure is low, the injection timing of the fuel injection pump can be made relatively earlier than when the atmospheric pressure is high, and ignition delay can be prevented. Incidentally, in the conventional structure described above, an oil seal 47 is provided between the bushing guide 42 and the push rod 45 in order to keep the fuel on the side of the communication holes 43 and 44 and the atmosphere on the side of the atmosphere sensing chamber 52 air-liquid-tight. is provided. When such an oil seal 47 is used, sliding resistance occurs as the push rod 45 slides, and this sliding resistance causes a delay in the response of the bellows 51 to changes in atmospheric pressure, and also causes the output of the bellows 51 to remain constant due to the atmospheric response. Even in this case, variations occur in the stroke of the push rod 45, causing large hysteresis in the control characteristics of the fuel injection timing. Further, there is also the problem that the sliding portion of the oil seal 47 is subject to wear and air-liquid tightness is likely to be lost early. For this reason, it is conceivable to stop employing the oil seal 47 and instead partition the relief passage 40 and the atmospheric sensing chamber 52 with a flexible airtight member such as a bellows or a diaphragm.
Such a flexible airtight member does not cause sliding resistance to the push rod 45, and can therefore respond to fluctuations in atmospheric pressure with high precision. [Problems to be solved by the invention] However, if a flexible airtight member such as the bellows or diaphragm is used, the resistance becomes too small, causing the push rod 45 to fluctuate even with a slight force. There is a concern that if it fluctuates, it will cause pulsation and the operation will become unstable. In order to prevent such pulsation of the push rod, a damper mechanism may be provided. However, if a special damper mechanism is to be provided around the push rod, the number of parts will increase and a special space will also be required, making the structure complicated. [Purpose of the invention] The present invention was developed based on the above circumstances, and its purpose is to improve the responsiveness to atmospheric pressure fluctuations and to create a damper mechanism with a simple structure that prevents pulsation of the push rod. Another object of the present invention is to provide a fuel injection timing control device for a distributed fuel injection pump that can be configured in a small space. [Structure of the invention] In order to achieve the above object, the present invention partitions the relief passage and the atmospheric sensing chamber by an axially expandable flexible airtight member provided between the push rod and the atmospheric pressure compensating housing, A fuel reservoir chamber communicating with the relief passage is formed in this divided area, and
a push rod advancement/retraction chamber is formed between the tip of the push rod and the atmospheric pressure compensating housing;
It is characterized in that the fuel reservoir chamber and the advance/retreat chamber are communicated with each other through a throttle passage formed in the atmospheric pressure compensating housing. [Function] According to the configuration of the present invention, the relief passage and the atmosphere sensing chamber are partitioned by a flexible airtight member such as a bellows or diaphragm instead of a conventional oil seal, which reduces the sliding resistance of the push rod. Therefore, it is possible to respond to atmospheric pressure fluctuations with high precision. In addition, since the fuel reservoir chamber divided by this flexible airtight member and the advancing/retracting chamber formed at the tip of the push rod are communicated through a throttle passage, the flow of fuel in the advancing/retracting chamber is controlled when the push rod changes. It is possible to prevent pulsation of the push rod by restricting it with a throttle passage. The damper mechanism consisting of these fuel reservoir chambers, advance/retreat chambers, and throttle passages uses the fuel reservoir chamber 2 divided by a flexible airtight member as one of the damper chambers, and also serves as the advance/retreat chamber of the push rod that is originally formed. Since the damper chamber is used as the other damper chamber, there is no need to form a special damper chamber, the structure is simple, and it can be configured in a small space. [Embodiment of the invention] The invention will be described below based on an embodiment shown in FIG. In this embodiment, the overall structure of the fuel injection pump may be the same as the conventional one shown in FIG. 3, so the explanation thereof will be omitted and will be explained with reference to FIG. 1 showing the main parts. Reference numeral 80 in FIG. 1 denotes a bellows, one end of which is sandwiched between the bushing guide 42 and the cover 49, which form a part of the atmospheric pressure compensating housing, and the other end is a flange of the push rod 45. is attached in an air-liquid tight manner. Therefore, the bellows 80 surrounds the push rod 45 and the spring 48 and is supported so as to be expandable and contractible in the axial direction, and partitions the fuel on the side of the communication holes 43 and 44 and the atmosphere on the side of the atmosphere sensing chamber 52 in an air-liquid tight manner. There is. Note that this bellows 80 is desirably made of a material such as Teflon or nylon. With such a bellows 80, the bellows 8
0, the space surrounded by the flange portion of the bushing guide 42 and the push rod 45 becomes a fuel reservoir chamber 81. This fuel reservoir chamber 81 is communicated with a push rod advancing/retracting chamber 83 formed at the tip of the bushing guide 42 via a throttle passage 82 formed in the bushing guide 42. The rest of the structure is the same as the conventional one shown in FIG. 4, so the explanation thereof will be omitted by using the same reference numerals. According to an embodiment of such a configuration, the bellows 8
0 is extendable and retractable, so it does not create resistance to the axial movement of the push rod 45, and the atmosphere sensing chamber 5
Completely cut off fuel for 2. Therefore,
Since no sliding resistance occurs on the push rod 45,
Since there is no delay in response to changes in atmospheric pressure and there is no variation in the stroke of the push rod 45, highly accurate control is possible without causing hysteresis in the control characteristics of the fuel injection timing. In addition, since the bellows 80 does not cause wear,
Air-liquid tightness is maintained over a long period of time, resulting in a long service life. Further, since the fuel reservoir chamber 81 and the chamber 83 in which the push rod 45 advances and retreats are communicated through the throttle passage 82, when the push rod 45 operates, the movement of the push rod 45 is alleviated by the flow resistance action of the throttle passage 82. This prevents undesired pulsation of the push rod 45. Therefore, the opening area of the relief passage 40 is controlled with high precision,
Since the movement of the timer piston 33 is restricted, the timer advance characteristics are stabilized. Moreover, in such a damper mechanism, the fuel reservoir chamber 81 partitioned by the bellows 45 is used as one damper chamber, and the originally required chamber 83 in which the push rod 45 advances and retreats is used as the other damper chamber. There is no need for a special fuel storage chamber, and since the throttle passage 82 connecting the fuel reservoir chamber 81 and the push rod advancement/retraction chamber 83 can be formed in the bushing guide 42, and can be integrally molded, no special parts are required. Since it is not necessary, the structure is simple, and no special space is required, it can be constructed in a small size. The results of experiments conducted on the structure of the above example are shown in the table below.

[Table] Note that responsiveness indicates the degree of delay in the timer advance with respect to changes in negative pressure. FIG. 2 shows another embodiment of the present invention, in which a diaphragm 90 is used in place of the bellows 80. Further, in the present invention, in addition to the bellows 80 and diaphragm 90, a cap or cover made of bellows, rubber, or the like may be used. [Effects of the invention] As explained above, according to the invention, in place of the conventional oil seal, a flexible airtight member that can be freely expanded and contracted in the axial direction, such as a bellows or a bellow frame, is used.
Since a diaphragm or the like is used, there is no resistance to the axial movement of the push rod, and fuel is completely cut off from the atmosphere sensing chamber. Therefore,
Since there is no sliding resistance on the push rod, there is no delay in response to changes in atmospheric pressure, and there is no need to worry about variations in the stroke of the push rod. This eliminates hysteresis in the control characteristics of fuel injection timing, allowing highly accurate control. It becomes possible. In addition, the fuel reservoir chamber divided by the flexible airtight member and the advance/retreat chamber formed at the tip of the push rod are communicated through a throttle passage, so that when the push rod fluctuates, the flow of fuel is regulated by the throttle passage. Therefore, pulsation of the push rod can be prevented. The damper mechanism, which consists of these fuel reservoir chambers, advance/retreat chambers, and throttle passages,
Since the fuel reservoir chamber divided by the flexible airtight member is used as one damper chamber, and the chamber in which the push rod advances and retreats is the other damper chamber, there is no need for a special damper chamber, and the structure is simplified. It can be constructed from a small base.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, and is a sectional view of the main part, Fig. 2 is a sectional view of the main part, showing another embodiment of the invention, and Figs. 3 and 4 show the conventional one. FIG. 3 is a sectional view showing the entire distribution type fuel injection pump, and FIG. 4 is a sectional view of the middle part of FIG. 1... Drive shaft, 2... Pump housing, 4...
... Plunger, 6 ... Fuel chamber, 8 ... Face cam, 9 ... Cam roller, 24 ... Spill ring,
33...Timer piston, 34...Timer cylinder, 35...High pressure chamber, 36...Low pressure chamber, 40...
Relief passage, 41...Atmospheric pressure compensation flow control valve, 42
...Butching guide, 43, 44...Communication hole,
45... Push rod, 48... Spring,
51... Bellows, 52... Atmospheric sensing chamber, 80...
...Bellows, 81... Fuel reservoir chamber, 82... Restriction passage, 83... Push rod advance/retreat chamber, 90...
diaphragm.

Claims (1)

[Scope of Claim for Utility Model Registration] A fuel injection timing control member in a distribution type fuel injection pump is connected to a timer piston, and the timer piston is slidably inserted into a working pressure chamber, and hydraulic pressure is introduced into the working pressure chamber. The operating pressure chamber is communicated with the low pressure fuel reservoir portion through a relief passage, and the opening area of the relief passage is operated in response to fluctuations in atmospheric pressure introduced into the atmospheric sensing chamber. A fuel injection timing control device that is controlled by a push rod, controls the operation of the timer piston according to the opening area of the relief passage, and thereby corrects the fuel injection timing of the fuel injection control member according to atmospheric pressure. The above-mentioned relief passage and the above-mentioned atmospheric sensing chamber are divided by a flexible airtight member that is axially expandable and contractible attached to the push rod, a fuel reservoir chamber communicating with the above-mentioned relief passage is formed in this divided area, and the fuel A fuel injection timing control device for a distribution type fuel injection pump, characterized in that a reservoir chamber and a push rod movement chamber formed at the tip of the push rod are communicated through a throttle passage.