JP2791912B2 - Servo valve electronic control timer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an electronically controlled timer, and more particularly to an electronically controlled timer using a servo valve timer in combination.

[Conventional technology and its technical problems]

A hydraulic timer for controlling the fuel injection timing of a distribution type fuel injection pump using an electromagnetic timing control valve is known in Japanese Patent Application Laid-Open No. 57-97024.

This electronic control timer is provided with an electromagnetic valve having a needle at the lower part of the pump housing, and connects the low pressure side of the electromagnetic valve to the low pressure chamber of the timer through a passage, and connects the high pressure side of the electromagnetic valve to the high pressure chamber of the timer through a passage. The signal from the electronic control unit turns on / off the current to the electromagnetic unit, and controls the amount of leakage from the high pressure chamber to the low pressure chamber by opening and closing the needle according to the duty ratio. The piston operation pressure is changed to control the movement of the timer piston, that is, the advance amount.

Therefore, this electronically controlled timer can control the injection timing in any way by controlling the energized / deenergized time, and has the advantage that the degree of freedom of the advance angle characteristic can be improved. However, since the high-pressure chamber and the pump chamber of the timer are always communicated with each other through the passage having the throttle in the timer piston, the fuel oil causes a kind of breathing phenomenon through the passage due to the driving reaction force peculiar to the disc cam, and the advance angle The accuracy of the characteristics tends to decrease, and there is also a problem in response.

On the other hand, a servo valve timer is known as a mechanical timer for the purpose of reducing the influence of driving reaction force and improving responsiveness (Japanese Utility Model Laid-Open No. 59-58743, etc.). In this timer, a servo valve is arranged on a timer piston, the pump valve and the timer high-pressure chamber are normally shut off by the servo valve, and the servo valve is displaced according to a change in fuel pressure in the pump chamber to the timer high-pressure chamber. The connection and disconnection of the fuel passage is controlled to displace the timer piston.

Therefore, as a method of solving the problem of the electronic control type timer, it is conceivable to combine an electromagnetic control valve with the servo valve timer. However, simply replacing the timer piston with a servo valve timer structure does not achieve the intended function. In a servo valve timer, the change in pump chamber pressure is the source of all control, whereas in an electromagnetically controlled timer, the control of the pressure in the timer high-pressure chamber is the same as in a standard temechanical timer. It is because it decides.

That is, in this case, a passage with a throttle connecting the timer high-pressure chamber and the pump chamber is omitted, and instead, a servo valve is arranged on the timer piston so that the pressure-receiving surface communicates with the pump chamber.
The timer high pressure chamber is connected to the solenoid valve high pressure side, and the timer low pressure chamber is connected to the solenoid valve low pressure side. However, in this structure, when the needle of the solenoid valve is opened to release the pressure in the timer high-pressure chamber to retard the timing, the fuel oil in the pump chamber displaces the servo valve to open the valve. As a result, the fuel oil in the pump chamber is replenished to the timer high-pressure chamber, and the brake is applied at a retarded angle. Next, the pressure in the pump chamber is reduced by the replenishment of the fuel oil into the timer high-pressure chamber, and the servo valve is retarded. For this reason, the merit of improving the response, which is the purpose of using the servo valve, is lost.

[Means for solving the problem]

The present invention has been made in order to solve the above-mentioned problems, and has as its object the relatively simple structure, the advantage of the improvement in the degree of freedom by the electromagnetic control type, and the improvement of the drive response by the servo valve timer. An object of the present invention is to provide a timer that can appropriately balance force reduction and high responsiveness, and that can perform highly accurate timer piston position control.

In order to achieve the above object, the present invention provides a timer including a timer unit and an electromagnetic valve which is provided outside the timer unit and communicates and shuts off a high pressure side and a low pressure side with a needle which is electromagnetically operated, wherein the timer unit is A timer piston having one end facing the high-pressure chamber and the other end facing the low-pressure chamber, and a servo valve arranged to be relatively movable with respect to the timer piston. A small-volume control pressure chamber is provided on the pressure-sensitive surface side of the servo valve. The control pressure chamber always communicates with the pump chamber via an orifice. Thus, the low pressure chamber is always in communication with the high pressure side of the solenoid valve, and the low pressure chamber is always in communication with the low pressure side of the solenoid valve.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a servo valve type electromagnetic control type timer according to the present invention, and FIGS. 1a and 2 (FIG. 1a).
(Shown with a phase shift of 90 degrees) shows the details of the timer section in an initial set state with a lead angle of zero.

Numeral 1 denotes a housing of the distribution type fuel injection pump, numeral 2 denotes a servo valve timer provided in the housing 1, and numeral 3 denotes an electromagnetic valve (duty solenoid valve) inserted in a housing portion below the servo valve timer 2.

The servo valve timer unit 2 has a cylinder hole 20 formed in the housing 1 so as to be orthogonal to the drive shaft. Both ends of the cylinder hole 20 are oil-tightly closed by a high-pressure side cover 21 and a low-pressure side cover 22. . A timer piston 4 movable axially into the cylinder bore 20, a servo valve 5 for controlling the movement of the timer piston 4, and springs 6a, 6b
Is arranged.

A recess 40 whose outer periphery is open to the pump chamber A is formed at an axially intermediate portion of the timer piston 4, and a slider 7 having a short columnar cross section is fitted therein.
The front end of a connection pin 7a connected to an inner ring of a roller holder (not shown) is fitted to.

A high-pressure chamber 41H is formed between the timer piston 4 and the high-pressure side cover 21, and a low-pressure chamber 4
1L is formed. This low pressure chamber 41L has a housing 1
The low-pressure port 10 is open, and the low-pressure port 10 is
This communicates with the low pressure side chamber 32 of the solenoid valve 3 described later.

Stepped holes 43 and 44 are formed in the timer piston 4 from the low-pressure chamber side toward the recess 40. Further, the timer piston 4 intersects with the small-diameter side hole 44 and bends to form the high-pressure A passage hole 45 communicating with the chamber 41H is provided. A snap ring 15 is attached to the wall of the large-diameter hole 43 of the timer piston 4, and a spring 6 b is interposed between the snap ring 15 and a seat disposed on the inner wall of the low-pressure side cover 22. The spring 6b does not perform a timer piston return function like a spring in an electronic control type timer, but serves to prevent vibration of the timer piston 4, and therefore has a very small spring constant and a small set force. The timer piston 4 is energized.

The servo valve 5 has a bottomed valve body 5a and a main body 5b which is slidably fitted in the bottomed valve body 5a. The bottomed valve body 5a has the small-diameter side hole with the thin bottom wall 50 facing the recess 40.
The orifice 51 is inserted through the center of the bottom wall 50. A groove 77 is formed in the slider 7 at a position corresponding to the orifice 51, and the fuel oil in the pump chamber A is introduced from the groove 70 through the orifice 51 into the bottomed valve body 5a.

The main body 5b is brought into contact with the step portion 42 of the stepped hole by the flange 52 formed on the low pressure chamber 41L side, and is urged to the high pressure side by the spring 6a supported by the shim 16 arranged on the inner surface of the low pressure side cover 22. I have.

In this state, the tip surface 53 of the main body 5b and the bottom wall of the bottomed valve body
Between 50 and 50, a small volume control chamber pressure B is created.
As shown in FIG. 1a, a first port 90 is provided through a bottomed valve body side wall at a portion corresponding to the control pressure chamber B, and an axial line corresponding to the peripheral surface of the timer piston 4, particularly, the stepped portion 42 is provided. A slit 92 is formed in the direction portion, and the slit 92 and the first port 90 are connected to a second port 91 extending in the radial direction.
Connected by A third port 93 is provided in the housing 1 so as to always communicate with the slit 92, and the third port 93 communicates with the high-pressure side chamber 31 of the solenoid valve 3 through a passage hole 94.

On the other hand, as shown in FIG. 2, the bottomed valve body 5a is provided with a communication passage hole 54 that communicates with the first port 90, for example, by 90 degrees out of phase with the first port 90 and communicates with the passage hole 45. 5b is provided with a control group 56 that can communicate with the communication passage hole 54 and a control hole 55 having a radial hole communicating with the control group 56 at a position separated by a predetermined distance from the front end surface 53,
55 has an opening in the low-pressure chamber 41L.

Next, the solenoid valve 3 is housed in a valve body 3a fitted in a blind hole 30 formed in the housing 1 and an inner cavity of the valve body 3a.
The needle 3b seated inside the distal end hole 34 of 3a, the armature 3c fixed to the rear of the needle, and an electromagnetic unit that attracts the armature 3c by energization and moves the armature 3c in the axial direction.
3d. The electromagnetic unit 3d is connected to an external electronic control unit 8, processes and calculates signals from various sensors, and provides a duty ratio (a ratio of a valve closing time within a unit time) of the drive signal to the electromagnetic unit 3d. It has become.

A high-pressure side chamber 31 is formed oil-tight in a blind hole at an intermediate outer peripheral portion of the valve body 3a, and the high-pressure side chamber 31 is provided with a passage hole 94 as described above.
To the third port 93. The valve body 3a is provided with a side hole 33 communicating with the inner cavity, and a passage hole 94 is formed in the needle 3b.
The fuel oil introduced from is introduced.

On the other hand, a low-pressure side chamber 32 is defined between the valve body 3a and the bottom of the blind hole.The low-pressure side chamber 32 communicates with the low-pressure chamber 41L through the passage hole 100, and when the needle 3b is lifted, the distal end hole 34 of the valve body 3a is opened. Is opened to communicate with the high-pressure side chamber 31.

FIG. 3 shows a fuel circuit using the present invention, in which fuel in a fuel tank a is sent to a pump chamber A by a feed pump b, and a plunger arranged in the pump chamber A changes according to the rotation of the engine. By rotating and moving up and down by the cam disk and the roller, the pressure is increased in the high pressure chamber c at the upper end of the plunger, and the fuel cut valve d and the delivery valve e
And is ejected to the ejection nozzle f by pressure. The timer section 2 and the solenoid valve 3 are provided outside the pump chamber A. In FIG. 3, the thick solid line indicates the pressure, the thin line indicates the hydraulic pressure, and the chain line indicates the low pressure.

[Operation of the embodiment]

 Next, the operation and operation of the embodiment will be described.

1 and 2, the recess 40 of the timer piston 4 is shown.
Communicates with the pump chamber A, and it is known that the pump chamber A is at a pressure corresponding to the engine speed.

The recess 40 of the timer piston 4 communicates with a groove 70 formed on the slider 7, and the groove 70 communicates with the control pressure chamber B via an orifice 51 provided on the bottomed valve body side wall of the servo valve 5. The control pressure chamber B has a first port 90 of the bottomed valve body 5a, a second port 91 and a slit 92 of the timer piston 4, and a third port 9 of the housing 1.
It is always in communication with the high pressure side chamber 31 of the solenoid valve 3 through the passage 3 and the passage hole 94, and this communication state is maintained at any position of the timer piston 4. Therefore, the fuel oil in the pump chamber A always flows into the high-pressure side chamber 31 of the solenoid valve 3 while being stored in the control pressure chamber B with a reduced flow rate from the groove 70 by the orifice 51. The low pressure chamber 41L of the timer unit 2 is always in communication with the low pressure side chamber 32 of the solenoid valve 3 through the port 10 and the passage hole 100.

On the other hand, the high-pressure chamber 41H of the timer section 2 is isolated from the pump chamber A by the main body 5b of the servo valve 5 in the state of FIGS. 1 and 2, and the passage hole 45 for the high-pressure chamber 41H is shown in FIG. As described above, it only communicates with the low-pressure chamber 41L via the communication passage hole 54, the control groove 56, and the control hole 55. Therefore,
When the solenoid valve 3 is not energized, the timer piston 4 does not move,
Further, the pressure in the control pressure chamber B is low, and the setting force of the spring 6a is superior, so that the servo valve 5 is in the illustrated state.

From this state, when the engine speed increases and the pressure in the pump chamber A increases, the hydraulic pressure of the pump chamber A is reduced by the orifice 51 of the servo valve 5 and enters the control pressure chamber B.
From here, it flows into the high pressure side chamber 31 of the solenoid valve 3 by the above route, and the pressure in the control pressure chamber B gradually increases. The main body 5b of the servo valve 5 moves as it is, but if the electromagnetic portion 3d of the solenoid valve 3 is energized, the needle 3b lifts,
Since the low pressure side chamber 32 and the high pressure side chamber 31 communicate with each other, the control pressure chamber B
Is reduced, so that the main body 5b does not move. When the power supply to the electromagnetic unit 3d is stopped again, the needle 3b is closed, so that the pressure side chamber 32 and the high pressure side chamber 31 are shut off.
, The body 5b moves against the spring force of the spring 6a. That is, the pressure in the control pressure chamber B is regulated by the duty control of the solenoid valve 3, and it is determined whether the operation of the surf valve 5 is performed.

Therefore, now, when the pressure in the control pressure chamber B is increased by the duty control of the solenoid valve 3, the main body 5b is moved to the bottomed valve body 5a.
Inside, the control groove 56 is gradually disconnected from the communication passage hole 54 and the passage hole 45 of the bottomed valve body 5a, while the distal end face 53 of the servo valve body 5b is seen through the communication passage hole 54. . As a result, the control pressure chamber B becomes a passage hole.
45 and the hydraulic pressure of pump chamber A
41H flows into the low-pressure chamber 41L and the solenoid valve 3
, The timer piston 4 is moved to the left (advance side) by the pressure of the high-pressure chamber 41H. When the passage hole 45 of the timer piston 4 and the communication passage hole 54 of the bottomed valve body 5a coincide with the control groove 56 of the servo valve body 5b, the movement of the timer piston 4 stops because the pressure in the high pressure chamber 41H is released to the low pressure chamber 41L. Thereby, the roller holder is rotated via the connecting pin 7a, and the injection timing is advanced.

In order to delay the injection timing by controlling the engine from the advanced state to the retarded side according to a decrease in the engine speed or the like, the duty ratio of the solenoid valve 3 may be reduced and the valve opening time of the needle 3b may be increased. In this way, the high-pressure side chamber 31 and the low-pressure side chamber 32 of the solenoid valve 3 communicate with each other, so that the pressure in the control pressure chamber B decreases and the timer high-pressure chamber
The pressure of 41H is applied to the passage hole 45-communication passage hole 54-control groove 56.
The servo valve body 5b and the timer piston 4 move to the right as a unit because the control valve 55 passes through the low pressure chamber 32 of the solenoid valve 3 through the route of the passage hole 100.

In the present invention, the pressure-sensitive portion (tip surface) of the servo valve 5 does not directly communicate with the pump chamber A, and the pressure-sensitive portion faces the control pressure chamber B. The control pressure chamber B is controlled by the orifice 51. Although communicating with the pump chamber A, a time difference is given to the pressure change in the pump chamber A. The control pressure chamber B is always kept in communication with the high pressure side chamber 31 of the solenoid valve 3 irrespective of the position of the timer piston 4. Accordingly, when the solenoid valve 3 is used to release the pressure in the high-pressure side chamber 31 to retard the pressure, the timer piston 4 moves while the servo valve 5 is kept open, whereby fuel oil is replenished from the pump chamber A and retarded. There is no braking. That is, since the pressure relationship between the pump chamber A and the control pressure chamber B is separated by the orifice 51, the control pressure chamber B quickly responds to the operation of the solenoid valve 3. Therefore, the relative balance between the servo valve 5 and the timer piston 4 can be surely moved together without breaking.

〔The invention's effect〕

According to the present invention described above, in a timer including a timer unit and an electromagnetic valve that is outside the timer unit and that communicates and shuts off a high pressure side and a low pressure side with a needle that is electromagnetically operated,
The timer section has a timer piston having one end facing the high-pressure chamber and the other end facing the low-pressure chamber, and a servo valve arranged to be relatively movable with respect to the timer piston, and one end of the timer piston communicates with the high-pressure chamber. The other end is provided with a passage communicating with and shut off from the low-pressure chamber via a servo valve, and a small-volume control pressure chamber which is always in communication with the pump chamber via an orifice is provided on the pressure-sensitive surface side of the servo valve. Since the pressure chamber is always in communication with the high pressure side of the solenoid valve by the passage, and the low pressure chamber is always in communication with the low pressure side of the solenoid valve, it is possible to provide a high degree of freedom in injection timing and high responsiveness,
Complex control such as a damping advance angle and a rear advancing angle can be realized with high accuracy only in the initial period within a short time, such as when the engine is transited. In addition, an excellent effect can be obtained in that the mechanism can be implemented relatively inexpensively because the change of the valve portion of the servo valve timer and the slight change of the porting and processing are sufficient.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a servo valve type electromagnetic control type timer according to the present invention, FIG. 1a is a partially enlarged view of the timer part, and FIG. 2 is a line II-II in FIG. 1a. 3 is a fuel system diagram according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Timer part, 3 ... Electromagnetic part, 3a ... Electromagnetic part, 4 ... Timer piston, 5 ... Servo valve, 5a ... Bottom valve body, 5b ... Main body, 31 ... High pressure side chamber, 32 ... Low pressure side chamber, 41H … High pressure chamber, 41L… Low pressure chamber, 51… Orifice, 90…
1st port, 91 ... 2nd port, 92 ... slit, 93 ... 3rd
Port, 94: passage hole, 100: passage hole, A: pump chamber, B
… Control pressure chamber

Claims (1)

(57) [Claims] 1. A timer comprising: a timer section; and an electromagnetic valve outside of the timer section, the solenoid valve communicating and shutting off a high pressure side and a low pressure side with a needle that is electromagnetically operated. The other end of the timer piston has a timer piston facing the low-pressure chamber, and the timer piston has a servo valve disposed so as to be relatively movable. The timer piston has one end connected to the high-pressure chamber and the other end connected to the low-pressure chamber via the servo valve. A small-volume control pressure chamber is provided on the pressure-sensitive surface side of the servo valve through an orifice, and a small volume control pressure chamber is provided on the pressure-sensitive surface side of the servo valve. A servo valve type electronically controlled timer, wherein the timer is always in communication with the high pressure side, and the low pressure chamber is always in communication with the low pressure side of the solenoid valve.