JPH0643490Y2 - Actuator for injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an injector actuator.

[Conventional technology]

Various injector actuators are known in which a piezo-piezoelectric element is arranged in a housing so that it can expand and contract, and a piston is driven by the piezo-piezoelectric element. For example, in the injector actuator described in JP-A-59-206671, the outer peripheral wall surface of the piezo-piezoelectric element is supported by the inner wall surface of the housing, which is described in JP-A-59-58129. In the injector actuator, the outer peripheral wall surface of the piezoelectric element is covered with an insulator, and the outer peripheral wall surface of the piezoelectric element is supported by the inner wall surface of the housing via the insulator.

Further, in the injector actuator described in JP-A-60-19968, an annular cooling oil chamber is formed between the outer peripheral wall surface of the piezoelectric element and the inner peripheral wall surface of the housing, and the cooling oil introduced into the cooling oil chamber is formed. Has a structure for cooling the piezoelectric element.

[Problems to be solved by the invention]

By the way, the piezo-piezoelectric element is formed of a laminated body of a large number of piezoelectric element plates, the laminated body is likely to be curved along its longitudinal axis, and the individual piezoelectric element plates may be displaced from each other. However, when the laminated body is curved along its longitudinal axis or the individual piezoelectric element plates are displaced from each other in this way, a localized concentrated stress is generated in the piezoelectric element plates, which causes a problem that the piezoelectric element plates are damaged. .

By the way, the above-mentioned JP-A-59-206671 or JP-A-59-
When the outer peripheral wall surface of the piezoelectric element is supported by the inner wall surface of the housing as described in Japanese Patent No. 58129, it is possible to prevent the laminated body from bending and prevent the piezoelectric element plates from being displaced from each other. It is possible to prevent the plate from being damaged. However, when the outer peripheral wall surface of the piezo-piezoelectric element is supported by the inner peripheral wall surface of the housing as described above, the cooling liquid cannot be directly guided around the outer peripheral wall surface of the piezo-piezoelectric element, and thus the piezo-piezoelectric element cannot be cooled well. There's a problem.

[Means for solving problems]

According to the present invention to solve the above-mentioned problems, in the injector actuator in which the piezo-piezoelectric element is arranged to be expandable and contractable in the housing, and the piston is driven by the piezo-piezoelectric element, the inner diameter of the housing inner peripheral wall The outer peripheral wall surface of the piezoelectric element is supported by the inner wall surface of the housing, and the cooling liquid flow groove extending spirally is formed over almost the entire inner wall surface of the housing. It is formed on the inner wall surface of the housing.

〔Example〕

Referring to FIGS. 3 to 5, 1 is a housing body,
Reference numeral 2 denotes a nozzle having a nozzle opening 3 at its tip, 4 denotes a spacer, 5 denotes a sleeve, and 6 denotes a nozzle holder for fixing the nozzle 2, the spacer 4, and the sleeve 5 to the housing body 1. A needle 7 that controls the opening and closing of the nozzle port 3 is slidably inserted into the nozzle 2, and the top of the needle 7 is connected to a spring retainer 9 via a pressure pin 8. This spring retainer 9 is a compression spring
It is always pressed downward by 10 and this pressing force is transmitted to the needle 7 via the pressing pin 8. Therefore, the needle 7 is always urged by the compression spring 10 in the valve closing direction.

On the other hand, a plunger hole 11 is formed in the housing body 1 coaxially with the needle 7, and a plunger 12 is slidably inserted into the plunger hole 11. The upper end of the plunger 12 is connected to a tappet 13, which is a compression spring.
It is always urged upward by 14. This tappet 13
Is moved up and down by a cam (not shown) driven by the engine, and thereby the plunger 12 is moved up and down in the plunger hole 11. On the other hand, in the plunger hole 11 below the plunger 12, a fuel pressurizing chamber 15 defined by the plunger 12 is formed. The fuel pressurizing chamber 15 is connected to a needle pressurizing chamber 18 via a rod-shaped filter 16 and a fuel passage 17, and the needle pressurizing chamber 18 is connected to the nozzle port 3 via an annular fuel passage 19 around the needle 7. It Further, as shown in FIG. 4, a fuel supply port 20 that opens into the fuel pressurizing chamber 15 is formed on the inner wall surface of the plunger hole 11 when the plunger 12 is at the upper position.
From this, the fuel having a pressure of about 3 kg / cm ² is supplied into the fuel pressurizing chamber 15.

On the other hand, a sliding hole 21 extending laterally is formed in the housing body 1 in the vicinity of the lateral side in the plunger hole 11. An overflow valve 22 is slidably inserted into the sliding hole 21, and a fuel overflow chamber 23 having a larger diameter than the sliding hole 21 is formed adjacent to the sliding hole 21. This fuel overflow chamber 23 has a fuel supply port 24
Fuel is supplied from the fuel tank, and the fuel flows out from a fuel outlet (not shown). The fuel pressure in the fuel overflow chamber 23 is maintained at about 3 kg / cm ² . The overflow valve 22 has an enlarged head 22a located in the fuel overflow chamber 23, and a circumferential groove 22b formed adjacent to the enlarged head 22a, and the enlarged head 22a of the valve port 25 Open / close control. The slide valve 22 is constantly urged to the right in FIG. 3 by the compression spring 26 located on the side opposite to the enlarged head 22a. A fuel pressurizing chamber 27 is formed in the housing body 1 as shown in FIG. This fuel overflow channel 27
One end of the fuel overflow passage 27 always communicates with the fuel pressurizing chamber 15, and the other end of the fuel overflow passage 27 always communicates with the circumferential groove 22b of the overflow valve 22.

Further, a rod hole 28 is formed in the housing body 1 coaxially with the sliding hole 21, and a rod 29 is slidably inserted into the rod hole 28. One end of the rod 29 is arranged so as to be able to contact the enlarged head portion 22a of the overflow valve 22, and a pressure control chamber 30 defined by the other end of the rod 29 is formed at the other end of the rod 29.

On the other hand, the housing body 1 has an actuator housing
31 is fixed, and a piezoelectric element 32 having a large number of piezoelectric element plates stacked therein is inserted into the actuator housing 31. At the lower end of the actuator housing 31 is a piston
33 is slidably inserted, and a cylinder chamber 34 filled with fuel is formed below the piston 33. The cylinder chamber 34 is connected to the pressure control chamber 30 via a fuel passage 35. Further, a disc spring 36 that constantly biases the piston 33 upward is inserted into the cylinder chamber 34.

Referring to FIGS. 1 and 2, the actuator housing 31 includes a hollow cylindrical housing body 31a and a cup-shaped upper housing 31b fitted and fixed to an upper end portion of the housing body 31a. The housing holder 37 secures the housing body 31a. A plug 38 for supplying electric power to the piezoelectric element 32 is attached to the upper housing 31b. An insulating plate 39 attached to the upper end of the piezoelectric element 32 is fixed to a spacer 40, and the spacer 40 has a protrusion 41 protruding upward. The protrusion 41 is fitted in a centering hole 42 formed in the upper housing 31b, whereby the piezoelectric element 32 is positioned on the central axis of the housing 31a, 31b. On the other hand, the insulating plate 43 attached to the lower end of the piezoelectric element 32
A concave groove 44 is formed on the lower wall surface of the piston 33, and a projection 45 integrally formed with the piston 33 is fitted into the concave groove 44. The outer peripheral wall surface of the piezo-piezoelectric element 32 is entirely covered with an insulating film 46.
Covered by.

Upper housing 31 as shown in FIGS.
The inner wall surface 47 of the lower portion of b has an inner diameter substantially equal to the outer diameter of the piezoelectric element 32 having the insulating film 46. Therefore, the inner wall surface 47 of the lower portion has the piezoelectric element 32 over its entire surface.
Contact the insulating film 46 of. A cooling liquid inflow chamber, to which a cooling liquid, for example, fuel is supplied, is provided above the lower portion inner peripheral wall surface 47.
48 is formed, and the cooling liquid inflow chamber 48 is formed in the housing 31a,
A cooling liquid supply passage 49 extending in 31b is brought into contact with a cooling liquid supply source, for example, the fuel overflow chamber 23. On the other hand, the inner peripheral wall surface 50 of the housing body 31a also has an inner diameter substantially equal to the outer diameter of the piezoelectric element 32 having the insulating film 46. It contacts the insulating film 46 of the element 32. Inner wall surfaces 47,5 of upper housing 31b and housing body 31a
On the 0, a cooling liquid circulation groove 52 extending spirally is formed over substantially the entire length of the inner peripheral wall surfaces 47, 50. The upper end of the cooling liquid flow groove 52 is connected to the cooling liquid inflow chamber 48, and the lower end of the cooling liquid flow groove 52 is connected to the cooling liquid discharge passage 51. The cooling liquid, for example, the fuel supplied into the cooling liquid inflow chamber 48 spirally flows through the cooling liquid flow groove 52 while cooling the piezoelectric element 32, and is then discharged from the cooling liquid discharge passage 51.

Thus, the upper housing 31b and the housing body 31a
When the spiral cooling liquid circulation groove 52 is formed on the inner peripheral wall surfaces 47, 50 of the piezo piezoelectric element 32, the outer peripheral wall surface of the piezoelectric element 32 is supported by the inner peripheral wall surfaces 47, 50 over the entire length thereof. Thus, it is possible to completely prevent the piezoelectric element 32 from bending along its axis, and it is possible to completely prevent the piezoelectric element plate from shifting. Further, by forming the spiral cooling liquid circulation groove 52 on the inner peripheral wall surfaces 47, 50 of the upper housing 31b and the housing main body 31a, the outer peripheral wall surface of the piezoelectric element 32 is made to have its entire length by these inner peripheral wall surfaces 47, 50. Cooling liquid and piezo piezoelectric element
The contact area and contact time of 32 can be increased.
As a result, a high cooling efficiency for the piezoelectric element 32 can be ensured.

On the other hand, a check valve 53 is inserted in the housing body 1 as shown in FIGS. 6 and 7. The check valve 53 includes a ball 55 that controls opening / closing of the valve port 54, a rod 56 that regulates a lift amount of the ball 55, and a compression spring 57 that constantly presses the ball 55 and the rod 56 downward. Therefore, the valve port 54 is normally closed by the ball 55. Check valve
The valve port 54 of 53 is connected to the fuel overflow chamber 23 via an annular fuel inflow passage 58 and a fuel inflow passage 59, and the fuel outflow passage 60 of the check valve 53 is connected to the cylinder chamber 34. As described above, the fuel pressure in the fuel overflow chamber 23 is maintained at about 3 kg / cm ² , and when the fuel pressure in the cylinder chamber 34 becomes lower than the fuel pressure in the fuel overflow chamber 23, the check valve 53 Is opened and fuel is replenished into the cylinder chamber 34. Therefore, the cylinder chamber 34 is always filled with fuel.

As described above, when the plunger 12 is in the upper position, the fuel is supplied from the fuel supply port 20 into the fuel pressurizing chamber 15, so that the fuel pressurizing chamber 15 has a low pressure of about 3 kg / cm ^{2 at} this time. . On the other hand, at this time, the piezoelectric element 32
Is in the maximum contraction position, and at this time, the fuel pressure in the cylinder chamber 34 and the pressure control chamber 30 is a low pressure of about 3 kg / cm ² . Therefore, at this time, the overflow valve 22 is moved to the right in FIG. 3 by the spring force of the compression spring 26, and the enlarged head portion 22a of the overflow valve 22 opens the valve port 25. Therefore, at this time, the fuel pressure in the fuel overflow passage 27 and the circumferential groove 22b of the overflow valve 22 is also a low pressure of about 3 kg / cm ² .

Next, when the plunger 12 descends, the fuel supply port 20 is closed by the plunger 12, but the overflow valve 22 is closed by the valve port 25.
The fuel in the fuel pressurizing chamber 15 flows into the fuel overflow chamber 23 through the fuel overflow passage 27, the circumferential groove 22b of the overflow valve 22 and the valve port 25 because of the opening. Therefore, at this time as well, the fuel pressure in the fuel pressurizing chamber 15 is as low as about 3 kg / cm ² .

Next, when the piezoelectric element 32 is charged with electric charge to start fuel injection, the piezoelectric element 32 expands in the axial direction, and as a result, the piston 33 descends, so that the cylinder chamber 34
And the fuel pressure in the pressure control chamber 30 rises rapidly. When the fuel pressure in the pressure control chamber 30 rises, the rod 29 moves to the left in FIG. 3, so that the overflow valve 22 also moves to the left, and the enlarged head 22a of the overflow valve 22 moves to the valve. Close port 25. When the valve port 25 is closed, the fuel pressure in the fuel pressurizing chamber 15 rapidly rises due to the downward movement of the plunger 12, and the fuel pressure in the fuel pressurizing chamber 15 is a predetermined pressure, for example 1500.
When the pressure exceeds a certain pressure of kg / cm ² or more, the needle 7 opens and fuel is injected from the nozzle port 3. At this time, the fuel overflow channel 27
A high pressure is also applied to the inside of the circumferential groove 22b of the overflow valve 22 through this, but the driving force does not act on the overflow valve 22 due to this high pressure because the pressure receiving areas of both axial end surfaces of the circumferential groove 22b are equal.

Then, when the electric charge charged in the piezoelectric element 32 is discharged to stop the fuel injection, the piezoelectric element 32 is discharged.
32 contracts. As a result, the piston 33 is raised by the spring force of the disc spring 36, and the fuel pressure in the cylinder 34 and the pressure control chamber 30 is reduced. When the fuel pressure in the pressure control chamber 30 decreases, the rod 29 and the overflow valve 22 move to the right in FIG. 3 due to the spring force of the compression spring 26, so that the enlarged head portion 22b of the overflow valve 22 opens. Open the gut 25. As a result, the high-pressure fuel in the fuel pressurizing chamber 15 passes through the fuel overflow passage 27, the circumferential groove 22b of the overflow valve 22 and the valve port 25, and the fuel overflow chamber 2
The fuel pressure in the fuel pressurizing chamber 15 immediately decreases to a low pressure of about 3.0 kg / cm ² to flow out into the inside 3, and the needle 7 descends to stop the fuel injection. Next, the plunger 12 rises and returns to the upper end position, and starts descending again.

[Effect of device]

By forming a cooling liquid flow groove extending spirally on the inner peripheral wall surface of the housing, the outer peripheral wall surface of the piezoelectric element can be supported by the inner peripheral wall surface of the housing over its entire length, so that the piezoelectric element curves along its axis. To completely prevent the piezoelectric element plate from being displaced, and to further increase the contact area and the contact time between the cooling liquid flowing in the cooling liquid flow groove and the piezoelectric element. Therefore, high cooling efficiency for the piezoelectric element can be ensured.

[Brief description of drawings]

1 is a side sectional view of the actuator, FIG. 2 is a side sectional view of the actuator of FIG. 1 showing the piezoelectric element removed, and FIG. 3 is a sectional view taken along line III-III of FIG. A side sectional view of the unit injector, FIG.
FIG. 5 is a sectional view taken along line IV-IV in FIG. 5, FIG. 5 is a plan view of FIG. 3, FIG. 6 is a sectional view taken along line VI-VI of FIG. 3, and FIG. FIG. 7 is a sectional view taken along the line VII-VII in the figure. 7 ... Needle, 12 ... Plunger, 15 ... Fuel pressurizing chamber, 21 ... Sliding hole, 22 ... Overflow valve, 23 ... Fuel overflow chamber, 29 ... Rod, 30 ... Pressure control Chamber, 31 …… Actuator housing, 32 …… Piezo piezoelectric element, 33 …… Piston, 52 …… Cooling liquid flow groove.

Claims (1)

[Scope of utility model registration request] 1. An injector actuator in which a piezo-piezoelectric element is arranged in a housing so that it can expand and contract, and a piston is driven by the piezo-piezoelectric element,
The inner diameter of the housing inner peripheral wall is formed to be substantially equal to the outer diameter of the piezoelectric element, and the outer peripheral surface of the piezoelectric element is supported almost entirely by the inner surface of the housing, and the entire inner surface of the housing is spirally shaped. An injector actuator in which a cooling liquid flow groove extending to the inside is formed on the inner peripheral wall surface of the housing.