Start assister of fuel injection pump

Abstract

A start assister (10) of a fuel injection pump, comprising a piston (46) inlayed into a housing (H), an upper chamber (49) formed over the piston (46), lower chamber (48) formed under the piston (46), wherein a sub port (42) is opened and closed by sliding of the piston (46), and a fuel injection timing is advanced by closing the sub port (42). A thermo-element (61) for sliding the piston is arranged on one side of the piston (46) in sliding direction. A telescopic pin (61a) of the thermo-element (61) is arranged in a low-pressure chamber (50) divided into the upper chamber and the lower chamber, and a connection pin (62) is interposed between the telescopic pin (61a) and the piston (46).

Description

technical field [0001] The invention relates to the design of a starting aid for fuel injection pumps. Background technique [0002] Conventionally, there is known a fuel injection pump start assist device constituting a start advance mechanism that advances the fuel injection timing by closing an auxiliary port of a plunger portion of the fuel injection pump. [0003] In such a starting assist device, a drain passage connected to the auxiliary port is formed on the housing, and the oil drain passage, that is, the auxiliary port is opened and closed by the outer peripheral portion of the piston slidably fitted in the housing. , by closing the auxiliary port, the fuel injection timing is advanced. [0004] Furthermore, the opening and closing of the auxiliary port by the piston is performed by attaching an actuator such as a temperature-sensitive member or a solenoid to the starting assist device, and sliding the piston by the expansion and contraction of the telescopic pin ...

AI Technical Summary

Problems solved by technology

[0006] In the starting assist device constructed as described above, for example, when a temperature-sensitive member is used as an actuating device, the telescopic pin of the temperature-sensitive member is arranged in one of the high-pressure upper chamber and the lower chamber constituted above and below the piston. , so the pressure fluctuation in the upper chamber or the lower chamber is added to the temperature sensing member, or the fuel oil in the upper chamber or the lower chamber invades the temperature sensing member, sometimes aging or damage of the temperature sensing member will occur

[0007] In addition, since the actuators such as temperature-sensitive components and solenoids are fixedly installed on the housing, the installed actuators cannot be replaced with other types of actuators according to the application in the starting auxiliary device of the same specification. Difficulty responding appropriately to a wide range of needs

[0008] Furthermore, even in the case where the auxiliary port is closed by the piston, since the fuel oil in the fuel chamber pressurized by the plunger leaks from the fitting gap formed between the housing and the piston through the aforementioned oil leakage passage to the fuel passage and the The upper chamber and the lower chamber are connected to each other such as drilling holes, so sufficient lead angle control cannot be performed

[0009] In order to prevent the fuel oil from leaking into the upper chamber and the lower chamber, it is necessary to process and manage the fitting gap formed between the case and the piston with the same precision as the fitting gap between the plunger and the plunger sleeve, which is very troublesome. matter

Images