JPH0352990Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement of a hydraulic timer installed in a fuel injection pump of a diesel engine.

[Conventional technology]

Conventionally, the fuel injection timing of diesel engines was adjusted using a flyweight timer whose movement amount varied depending on the engine speed, but in recent years, flyweight timers have been used that do not depend on the magnitude of centrifugal force caused by the engine speed. , a device called a hydraulic timer that adjusts the fuel injection timing by advancing the oil pressure using oil pressure has begun to be adopted (for example, Japanese Utility Model Application Publication No. 1983-99026,
(Japanese Patent Application Laid-open No. 165635/1983).

In this way, the hydraulic timer device has a structure as shown in FIGS. 6 and 7, for example, and is formed integrally with the driven shaft 1 or has a circular shape fixed to rotate integrally with the driven shaft 1. It includes a first eccentric cam 3 fitted into the plate 2 and a second eccentric cam 4 fitted into the first eccentric cam 3.

The disk 2 and these first and second eccentric cams 3
and 4 are shown in the upper half of FIG. 7, in which the second eccentric cam 4 is engaged with a pin 6 fixed to the drive disk 5, while the first eccentric cam 3 is fitted with a pin 6 fixed to the drive disk 5. , a pin 8 fixed to the adjusting piston 7 is engaged.

The adjusting piston 7 is housed in a cylinder 9 that is rotatably attached to the driven shaft 1 and is biased by a spring 10.

The driven shaft 1 is connected to a camshaft of a fuel injection pump (not shown), and pressurized lubricating oil O is supplied from a hydraulic device 14 into a cylinder 9 located on the outer periphery of the driven shaft 1. It is becoming more and more
This hydraulic system 14 pressurizes lubricating oil O in an oil tank 15 with a pump 17 and sends the oil to an oil pipe 13 having a throttle 11.
The controller 12 and the pressure regulating valve 16 can be used to change the fuel injection timing of the fuel injection pump while detecting the load L and the load L.

That is, when the piston 7 is moved in the A direction in the figure, it is done by the hydraulic pressure of the lubricating oil O, and when it is moved in the B direction, it is done by the urging force of the return spring 10. There is. and,
When the piston 7 presses the spring 10 in the direction of arrow A due to hydraulic pressure, the pin 8 moves to the position shown by the broken line, thereby rotating the first eccentric cam 3, and thereby the second eccentric cam 4 and pin 6 move to the seventh position. The driven shaft 1 is moved to the position indicated by the broken line in the figure, and the driven shaft 1 is advanced by θ with respect to the drive shaft disc 5.

However, in the conventional hydraulic timer configured as described above, fluctuations in driving torque occur due to intermittent injection of the fuel injection pump, and this impact causes high pressure fluctuations in the high pressure part of the hydraulic oil via the piston 7. . This causes a problem in that the oil seal installed for maintaining high pressure is destroyed and the timer function is lost.

[Purpose of invention]

The purpose of this invention is to solve the problems of the conventional hydraulic timer, absorb high pressure peaks of hydraulic oil due to fluctuations in driving force in the pressure regulating piston, and prevent abnormal increases in hydraulic pressure on the high pressure side of the pressure regulating piston. prevent,
The objective is to provide an excellent hydraulic timer that prevents oil seal damage and is durable and reliable.

[Structure of the idea]

The hydraulic timer of the present invention that achieves the above object is a hydraulic timer for adjusting injection timing that is attached to a fuel injection pump, and includes a shock pressure absorption mechanism provided at the head of an adjustment piston built into the timer. It is characterized by the presence of

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Figure 1 shows the adjusting piston 7 of the hydraulic timer of the present invention.
This figure shows the configuration of the first embodiment.

In this embodiment, a recess 2 is provided in the head 7a of the piston 7.
1 is provided, and the side wall 21a of this recess 21
The snap spring 22 is used as a shock pressure absorption mechanism.
A closed type bellows 2 having a closed space 23a using
3 is attached to cover the recess 21. This bellows 23 is a snap spring 22
In addition to being able to be attached with a screwdriver, it can also be fixed in the recess 21 of the piston 7 by caulking, press-fitting, or the like. 7b is a through hole through which the pin 8 is inserted.

Further, the bellows 23 is provided with an orifice 24 at its peripheral edge, which communicates the high pressure side of the piston 7 with the inside of the recess 21, which is a closed space by the bellows 23. Therefore, bellows 23
is adapted to receive pressure from inside the recess 21 as well. The closed space 23a of the bellows 23
does not contract and does not change the internal volume of the cylinder until the hydraulic pressure reaches a predetermined pressure value.

In the hydraulic timer of the present invention incorporating the piston 7 configured as described above, a sharp working hydraulic pressure exceeding the contraction pressure value of the closed space 23a is generated in the cylinder on the high pressure side of the piston 7 due to intermittent injection of the fuel injection pump. When the peak occurs, a sudden impact pressure is applied to both sides of the bellows 23 as described above, and the closed space 23a of the bellows 23 contracts in response to this pressure. As a result, the internal volume of the cylinder increases, the pressure increase on the high pressure side is attenuated, and excessive hydraulic pressure is prevented from being applied to the oil seal portion.

Therefore, for example, even when oil pressure fluctuation including a peak part H as shown by waveform M in FIG.
The bellows 23 having a peak absorbs the shock pressure and the pressure within the cylinder is attenuated as shown by waveform N in FIG. This prevents damage to the oil seal mechanism and increases the durability of the hydraulic timer.
Improved reliability.

FIG. 2 shows a second embodiment of the piston 7 built into the hydraulic timer of the present invention.

In this embodiment as well, a recess 21 is provided in the head 7a of the piston 7, and a diaphragm 24 is attached to the side wall 21a of the recess 21 as a shock pressure absorbing member with a snap ring 22 so as to cover the recess 21. ing. This diaphragm 24 is also designed not to deform unless the oil pressure exceeds a predetermined pressure. The bottom 21b of the recess 21 is communicated with the spring side of the piston 7 through an orifice 21c.

In a hydraulic timer with a built-in piston 7 having this configuration, when impact pressure is input into the cylinder, the diaphragm 24 bends toward the bottom 21b of the recess 21, the cylinder volume increases, and the hydraulic pressure inside the cylinder is also attenuated. Ru.

FIG. 3 shows a third embodiment of the piston built into the hydraulic timer of the present invention.

In this embodiment, a through hole 25 communicating from the high pressure side to the spring side is provided inside the piston 7, and a valve body 26a is installed in the through hole 25 as a pressure regulating valve biased toward the high pressure side by a spring 26b. 26 are provided. Reference numeral 27 denotes a pressure relief hole 27 for adjusting the urging force of the valve body 26a of the spring 26b.
A is a set screw provided, and is used to set the displacement start pressure of the pressure regulating valve 26.

In the hydraulic timer incorporating the piston 7 of this mechanism, when impact pressure is input into the cylinder, the valve body 26a of the pressure regulating valve 26 moves against the spring 26b to expand the cylinder volume. This reduces the oil pressure inside the cylinder and prevents damage to the oil seal.

In this way, the hydraulic timer of the present invention uses the impact pressure absorption mechanism provided at the piston head to temporarily increase the cylinder volume on the piston head side when impact pressure is applied, thereby preventing an increase in oil pressure. be.

[Effect of idea]

As explained above, the hydraulic timer of the present invention is a hydraulic timer for adjusting injection timing attached to a fuel injection pump, and a shock pressure absorption mechanism is provided in the head of the adjustment piston built into the timer. As a result, even if driving torque fluctuations occur due to intermittent injection of the fuel injection pump and the impact load is input into the cylinder, the pressure peak on the high pressure side of the cylinder is attenuated by the action of the impact pressure absorption mechanism installed in the piston. This has the effect of preventing damage to sealing mechanisms such as oil seals and improving the durability and reliability of the hydraulic timer.

[Brief explanation of the drawing]

Fig. 1 shows the configuration of the first embodiment of the hydraulic timer of the present invention, and is a vertical sectional view of a single pressure regulating piston built in the hydraulic timer, and Fig. 2 shows the second embodiment of the hydraulic timer of the present invention. It shows an example configuration,
FIG. 3 is a vertical sectional view of a single piston built in a hydraulic timer, and FIG. 3 shows the configuration of a third embodiment of the hydraulic timer of the present invention. The figure is a waveform diagram of hydraulic pressure including impact pressure input to the cylinder, Figure 5 is a waveform diagram showing the same waveform after being attenuated by the hydraulic timer of the present invention, and Figure 6 is a diagram showing the configuration of a conventional hydraulic timer. The schematic side sectional view shown in FIG. 7 is taken along the line C-C in FIG.
FIG. DESCRIPTION OF SYMBOLS 1... Driven shaft, 2... Disk, 3... First eccentric cam, 4... Second eccentric cam, 5... Drive disk, 7... Adjustment piston, 21... Recess, 23...
... bellows, 24 ... diaphragm, 25 ... through hole, 26 ... pressure regulating valve, 27 ... set screw.

Claims (1)

[Scope of utility model registration request] 1. A hydraulic timer for adjusting injection timing mounted on a fuel injection pump, characterized in that a shock pressure absorption mechanism is provided at the head of an adjustment piston built into the timer.