JPH1122493A - Fuel injection timing control device of fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a smooth sliding by restraining a deformation of a timer piston and restrain sticking and seizure of the timer piston even in a injection pump in which a high pressurization of a fuel injection is required. SOLUTION: A timer piston 22 is stored to be slidable in a timer cylinder 21, a high pressure chamber 24 to which a fuel within a pump is introduced is provided at one end of the timer piston 22, a timer spring 26 which energizes the timer piston 22 to the high pressure chamber 24 side is disposed at the other end of the timer piston 22, and a spark advance is adjusted in response to the pressure of the high pressure chamber 24. A communicating passage 33 which communicates a sliding contact part of the timer piston 22 with the high pressure chamber 24 is provided at the timer piston 22. The communicating passage 33 is divided into a plurality of passages, and each of the passages opens to the sliding contact part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a cam ring having a cam surface formed on an inner periphery thereof provided around a rotor, and a plunger provided on the rotor is reciprocated radially by the cam ring to reduce the volume of a compression chamber. The fuel injection device is used in a so-called VR pump that changes the pressure, a so-called VE pump that compresses and distributes fuel while rotating a plunger by a cam disk and reciprocating in an axial direction. The present invention relates to an injection timing control device.

[0002]

2. Description of the Related Art As a conventional timer device, for example, Japanese Utility Model Laid-Open No. 60-47836 is known. this is,
In this publication, a timer piston 16 is housed in a timer cylinder 15, and a timer piston pressure chamber 23 is formed at one end of the timer piston 16. 23
The fuel pressurized by the feed pump 7 is guided to urge the timer piston 16 with this fuel pressure,
A spring housing chamber 25 is formed at the other end of the timer piston 16, and the timer piston 16 is urged toward the timer piston pressure chamber 23 by a timer spring 17 housed in the spring housing chamber 25. The configuration is shown in which the injection timing is adjusted by changing the advance amount by changing the fuel pressure in the piston pressure chamber 23.

The configuration in which the advance amount is adjusted by the balance between the fuel pressure on the high pressure side and the urging force of the timer spring is basically the same in a VR pump.
In recent years, a fuel tank in which the fuel pressure on the high pressure side is controlled by an electromagnetic valve called a timing control valve (TCV) has been put to practical use.

[0004]

By the way, in recent injection pumps, higher pressure of injected fuel is further required,
Along with this, it is necessary to reconsider the structure suitable for high pressure. Generally, the VR pump is known as a pump structure more suitable for increasing the pressure than the VE pump because the plunger reciprocates in the radial direction of the rotor. However, in any pump, a roller is inserted into the cam lobe. In this case, a driving reaction force is applied to the cam ring or the cam disk, and a large impact force acts on the timer piston connected thereto in the direction of compressing the high-pressure chamber.

[0005] The higher the injection fuel pressure, the more
Although this driving reaction force becomes large, it has become clear that, as one of the problems associated with such a high pressure, a bitter occurs between the timer piston and a member that comes into sliding contact with the timer piston, and that the timer piston sticks. Was. Although the specific mechanism that causes such inconvenience is not clear, since the seizure of the timer piston occurs near the high-pressure chamber, the high-pressure chamber pressure is momentarily increased by the driving reaction force transmitted to the timer piston. It is considered that this is because the high pressure chamber pressure deforms the timer piston as shown by a two-dot chain line in FIG.

That is, the deformation of the timer piston A shown in FIG. 6 is exaggerated for the sake of convenience of description, but the deformation of the timer piston A causes the clearance of the sliding contact portion C to be reduced. It is presumed that absorption is not possible, and the inner surface of the timer cylinder B is shaved and metal powder generated at that time enters the sliding contact portion C or is strongly pressed against the inner surface of the timer cylinder B.

Therefore, in the present invention, even in an injection pump which requires a high pressure of the injected fuel, the deformation of the timer piston is suppressed, smooth sliding is ensured, and the timer piston is prevented from being bitter and seized. It is an object of the present invention to provide an injection timing control device for a fuel injection device which is designed to improve durability.

[0008]

In order to achieve the above object, an injection timing control device for a fuel injection device according to the present invention has a timer piston slidably housed in a timer cylinder, and one end of the timer piston. A high-pressure chamber into which fuel in the pump is introduced is provided, and an urging member for urging the timer piston toward the high-pressure chamber is provided at the other end, and an advance amount is adjusted according to the pressure of the high-pressure chamber. On the premise of a possible configuration, a communication path is provided for communicating the sliding contact portion of the timer piston with the high-pressure chamber (claim 1).

In the conventional configuration in which the high-pressure chamber pressure acts only on the end face of the timer piston facing the high-pressure chamber, the timer piston is allowed to deform in the radial direction due to the shape and connection structure of the timer piston. However, in the above configuration, since the fuel in the high pressure chamber is guided to the sliding contact portion of the timer piston through the communication path, even when the high pressure chamber pressure is instantaneously increased due to the driving reaction force. , This pressure does not only act on the end face of the timer piston facing the high pressure chamber,
It also acts on the sliding portion of the timer piston, which is considered to suppress the force for deforming the timer piston, thereby ensuring the smooth movement of the timer piston.

Here, the fuel injection device may be of the VE type or the VR type, and is particularly useful in a VR type suitable for high pressure. The communication passage may be provided on the timer cylinder side. However, since the timer piston slides according to the pressure of the high-pressure chamber, it is desirable to provide the communication passage on the timer piston itself. Preferably, the other end is opened to the sliding contact portion of the timer piston (claim 2).

In forming the communication passage, it is preferable that fuel in the high-pressure chamber is guided around the timer piston in a well-balanced manner. Therefore, one end is opened to the high-pressure chamber, and the other end is branched into a plurality of passages. It is preferable that the respective passages are opened to the sliding contact portion of the timer piston (claim 3). The number of branches of the communication passage is preferably three or more in order to balance the force exerted by the timer piston. Each of the branched passages does not need to have the same diameter, but may be set to different diameters as necessary. Then, the force applied to the peripheral surface of the timer piston may be adjusted.

In order to guide the fuel in the high pressure chamber to the sliding contact portion of the timer piston, a circumferential groove is formed in the sliding contact portion.
The end of the communication path may be connected to this groove (claim 4). This groove may be provided on the timer cylinder side, but is preferably provided on the timer piston itself in consideration of the movement of the timer piston (claim 5).

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a main part of a VR type distribution type fuel injection pump. This distribution type fuel injection pump 1 has a rotor 3 disposed in a housing 2, and the rotor 3 is driven by an engine (not shown). It receives driving torque via the shaft 4 and rotates in synchronization with the engine. The rotor 3 extends through a chamber 5 defined by the housing 2, and the chamber 5 is supplied with fuel from a fuel tank via a feed pump (not shown).

The drive shaft 4 is rotatably mounted on a support member 6 fixed to the housing 2 via a radial bearing 7, and the rotor 3 is rotatably inserted into a support member 8 fixed on the housing 2. The enlarged diameter portion 3a whose diameter is enlarged is formed at the base end portion.
The roller holding piece 3b which protrudes in a radial direction is formed in a. A groove extending in the radial direction is formed in the drive shaft 4 at a connection end portion with the rotor 3.
b is fitted to receive rotational power from the drive shaft 4. A plunger passage 9 extending in the radial direction (radial direction) is formed in the enlarged diameter portion 3a of the rotor 3. In this configuration example, for example, 180 plungers are formed on the same plane.
Two plunger passages 9 are formed at a certain interval, and a plunger 10 is slidably inserted into each plunger passage 9.

The distal end of each plunger 10 faces so as to close a compression chamber 11 provided at the center of the rotor 3, and the proximal end of the plunger 10 has a shoe 12 and a roller 12 arranged between the roller holding pieces 3b. The inner surface of the ring-shaped cam ring 14 is slidably contacted through the ring 13. The cam ring 14 is provided concentrically outside the rotor 3, and cam lobes 14 a corresponding to the number of cylinders are formed on the inner periphery, and when the rotor 3 rotates, each plunger 10
Reciprocates in the radial direction (radial direction) of the rotor 3, and the compression chamber 1
1 is made variable.

That is, if the cam ring 14 is formed corresponding to, for example, four cylinders, the cam lobes 14a are formed on the inside at every 90 degrees.
The two plungers 10 move so as to simultaneously compress the compression chamber 11 in a sandwiching manner, and move away from the compression chamber 11 at the same time.

The rotor 3 has a vertical hole 15 formed in the axial direction thereof and communicating with the compression chamber 11. The vertical hole 15 has a distribution port 16 communicating with a plurality of distribution passages corresponding to the number of cylinders. Are formed and an inflow / outflow port 17 that can be opened to the chamber 5 is formed.

A delivery valve is attached to each distribution passage, and compressed fuel is pressure-fed from the delivery valve to the injection nozzle. A control sleeve is slidably fitted to a portion of the rotor 3 that is exposed in the chamber 5, and an inflow / outflow port 17 is opened to the chamber 5 during the suction process so that fuel in the chamber is compressed. Outflow port 1 during the pumping process
The timing for opening the chamber 6 to the chamber 5 and cutting off the fuel pumping is adjusted.

Below the cam ring 14, a timer device 2
The timer device 20 has a timer piston 22 slidably housed in a timer cylinder 21 formed in the housing 2, and a connecting rod integrally formed with the cam ring 14 on the timer piston 22. Reference numeral 23 is connected from the radial direction (above), and converts the straight movement of the timer piston 23 into the rotation movement of the cam ring 14 to adjust the injection timing according to the operating conditions of the engine.

At one end of the timer piston 22, there is formed a high-pressure chamber 24 into which fuel in the chamber 5 is introduced, and at the other end, a low-pressure chamber 25 communicating with the suction path of the feed pump. The low pressure chamber 25 has a timer spring 2
The timer piston 26 is constantly urged toward the high-pressure chamber by the timer spring 26. Therefore, the timer piston 22 stops at a position where the spring force of the timer spring 26 and the high-pressure chamber pressure are balanced,
When the high-pressure chamber pressure increases, the timer piston 22 moves toward the low-pressure chamber against the timer spring 26, and the cam ring 1
4 is rotated in a direction to advance the injection timing. Also,
When the high-pressure chamber pressure decreases, the timer piston 22 moves toward the high-pressure chamber, and the cam ring 14 is rotated in a direction to delay the injection timing. The high-pressure chamber pressure is adjusted by a timing control valve (not shown) so as to obtain a required timer advance angle.

As shown in FIG. 3, the timer piston 22 has a recess 27 formed in the peripheral surface thereof in anticipation of the movable range of the connecting rod 23. A through hole 28 perpendicular to the axis of each piston 22 is formed.
A cylindrical rotating body 29 is inserted into 8 so as not to protrude from the peripheral surface of the timer piston 22, and the connecting rod 22 is inserted into the insertion hole 35 formed in the rotating body 29 via the concave portion 27. .

The timer piston 22 has a high-pressure chamber 2
4 has a bottomed introduction hole 31 in the axial direction from the center of the end face 30 facing
Is formed, and one end is opened in the introduction hole 31.
A large number of branch holes 32 having the other end opened to the outer peripheral surface of the timer piston 22 are formed. One end of the introduction hole 31 and the branch hole 32 is opened in the high-pressure chamber 24, and a sliding contact portion of the timer piston 22 is formed. A communication path 33 having the other end opened is formed. In this example, five branch holes 32 are formed, and are formed so that the phase intervals are equal (at a phase interval of 72 degrees) on a plane perpendicular to the axis of the timer piston 22. Further, the diameter of each branch hole 32 is formed to be equal, and the opening of the branch hole 32 is
It is formed so as to open at a predetermined position between the end face 30 facing to 4 and the recess 27.

In the above configuration, each time the roller 13 reaches the cam lobe 14a of the cam ring 14 with the rotation of the rotor 3, the high pressure chamber 24
A drive reaction force in the direction of compressing (retard direction) is momentarily applied, and the high-pressure chamber pressure is rapidly increased each time. This pressure is transmitted to the sliding portion of the timer piston 22 via the communication passage 33, and as a result, the end face 3 of the timer piston 22
A pressure of the same magnitude as the pressure applied to 0 also acts on the sliding contact portion. Therefore, the timer piston 22 tends to be deformed in the radial direction by the pressure applied to the end face 30, but this force is suppressed by the pressure of the fuel guided to the sliding contact portion via the communication passage 33, and An oil film of the fuel supplied through the slidable portion is formed on the timer piston 2.
It is considered that the centering of No. 2 and the sliding resistance can be reduced. Actually, according to an experimental result of driving the timer device in accordance with the conventional operating condition in which image sticking occurs, a smooth movement of the timer piston 22 is confirmed.

FIG. 5 shows another example of the configuration of the timer piston 22 used in the timer device 21. In this configuration example, the branch hole 32 is positioned 90 degrees on a plane perpendicular to the axis of the timer piston 22. Four are formed at a phase interval of degrees,
The opening end of each branch hole 32 is connected to an annular groove 34 provided in the timer piston 22 along the circumferential direction. Other configurations are the same as those of the above-described configuration example.

In such a configuration, the number of the branch holes 32 extending from the introduction hole 31 is four, but the configuration is substantially the same as the state in which countless branch holes are opened in the sliding contact surface. Since the chamber pressure is transmitted to the entire annular groove 34 through the communication passage 33, it is considered that the timer piston 22 can be centered and the sliding resistance can be reduced similarly to the above-described configuration example. You can expect smooth movement.

Although the above configuration example shows an example in which the invention is applied to a VR type injection pump, basically the same structure can be used in a VE type injection pump. Also, the number of the branch holes 32 may be set within a range that does not break the balance of the force applied to the timer piston 22 in the radial direction.
The number is preferably three or more, more preferably five or more, and the diameter of each branch hole 32 may be made different from the viewpoint of adjusting the balance of force.

[0027]

As described above, according to the present invention,
A communication passage is provided to communicate the high pressure chamber formed at one end of the timer piston with the sliding contact portion of the timer, so that the force that the timer piston attempts to deform due to the high pressure chamber pressure is guided to the sliding contact portion via the communication passage. It is considered that the pressure can be suppressed by the applied fuel pressure, and smooth sliding of the timer piston can be ensured. In other words, it is possible to suppress the occurrence of bitterness between the timer piston and the member that comes into sliding contact with the timer piston and to prevent the timer piston from sticking, and it is possible to cope with an increase in the pressure of the injected fuel.

Further, since the smooth sliding of the timer piston can be ensured, the lead angle control with good responsiveness can be realized.
Since the bitterness and burn-in can be suppressed, the durability of the timer device can be improved.

In particular, when a communication passage opening to the sliding contact portion and a circumferential groove connected to the communication passage are provided in the timer piston, even if the timer piston is moved according to the high-pressure chamber pressure, the timer piston is not moved. The position where the fuel pressure acts does not fluctuate, and it becomes easy to identify the position of the communication passage that can most effectively suppress the deformation of the timer piston. Further, in a configuration in which one end of the communication passage is opened to the high-pressure chamber and the other end is branched into a plurality of passages and opened to the sliding contact portion, the pressure balance applied to the timer piston can be easily adjusted. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a VR-type distribution type fuel injection device utilizing the present invention.

FIG. 2 is a sectional view cut in a vertical direction so that a cam ring and a timer piston of the fuel injection device shown in FIG. 1 appear.

FIG. 3 is a perspective view showing a timer piston of the fuel injection device shown in FIG. 1;

FIG. 4 is a cross-sectional view of the timer piston of FIG. 3 taken along line IV-IV.

FIG. 5 shows another example of the configuration of the timer piston. FIG. 5 (a) is a vertical sectional view including the axis of the timer piston, and FIG. 5 (b) Figure 5
It is sectional drawing cut | disconnected by the VV line of (a).

FIG. 6 is an explanatory diagram showing a conventional timer device.

[Explanation of symbols]

 Reference Signs List 20 timer device 21 timer cylinder 22 timer piston 23 connecting rod 24 high-pressure chamber 26 timer spring 31 introduction hole 32 branch hole 33 communication passage 34 annular groove

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Tanaka, Inventor 3-13-26, Yayumicho, Higashimatsuyama-shi, Saitama Prefecture Inside Zexel Higashimatsuyama Plant (72) Inventor Katsuhiro Shimogoshiki-cho 3-13, Yayumicho, Higashimatsuyama-shi, Saitama No. 26 Inside of Xexel Higashi Matsuyama Plant

Claims (5)

[Claims] 1. A timer piston is slidably accommodated in a timer cylinder, a high-pressure chamber into which fuel in a pump is introduced is provided at one end of the timer piston, and the timer piston is attached to the high-pressure chamber at the other end. An injection timing control device for a fuel injection device, which includes a biasing member for biasing and adjusts an advance amount according to a pressure of the high-pressure chamber, wherein a communication passage communicating between a sliding contact portion of the timer piston and the high-pressure chamber; An injection timing control device for a fuel injection device, comprising: 2. The fuel according to claim 1, wherein the communication passage is provided in the timer piston, one end opens to the high-pressure chamber, and the other end opens to a sliding portion of the timer piston. An injection timing control device for the injection device. 3. The communication passage has one end opened to the high-pressure chamber,
2. The injection timing control device for a fuel injection device according to claim 1, wherein the other end is branched into a plurality of passages, and each of the branched passages opens to a sliding portion of the timer piston. 4. The fuel injection device according to claim 1, wherein an end of the communication passage opening to a sliding contact portion of the timer piston is connected to a groove provided along a circumferential direction. Injection timing control device. 5. An injection timing control device for a fuel injection device according to claim 4, wherein said groove is provided in said timer piston.