JP2773200B2 - Fuel injection pump with fuel injection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection pump for controlling fuel injection.

[Conventional technology]

For example, in a diesel engine for automobiles, fuel pressurized by a fuel injection pump is supplied to the engine through an injection nozzle.However, in order to reduce noise and vibration during idling operation, pilot injection of fuel is performed. It is known to be effective.

The pilot injection device controls the fuel pressure by connecting an actuator to a pump chamber of a fuel injection pump.
For example, as disclosed in JP-A-63-134849,
In a distributed fuel injection pump, if the fuel is temporarily released by an actuator while the fuel in the pump chamber is pressurized by the plunger, the fuel pressure in the pump chamber becomes lower than the valve opening pressure of the injection nozzle and the fuel is injected. Is temporarily stopped, so that pilot injection can be performed. Specifically, a casing fixed to the pump housing, a pressure chamber formed in the casing and communicating with the pump chamber, a piston slidably disposed in the casing, and a piston housed in the casing. There has been known a piezoelectric element laminate that drives a piston.

[Problems to be Solved by the Invention] However, in the above-described structure, not only does the fuel flow into the piezoelectric element laminate, there is a danger of malfunction due to electric leakage, but also the piezoelectric element laminate has a Curie point. There was a drawback that the heat became high up close.

The present invention has been devised in view of the above drawbacks, and has as its technical object to provide a fuel injection device of a combustion injection pump that can cool a piezoelectric element laminate without fuel flowing into the piezoelectric element laminate. I do.

Means for Solving the Problems A fuel injection pump having a fuel injection device according to the present invention pumps fuel in a pump chamber pressurized by a plunger to an injection nozzle through an injection passage and pressurizes the pressurized fuel. A fuel injection pump having a fuel injection device for controlling the injection of fuel, wherein the fuel injection device has an opening communicating with the pump chamber at one end, a bottom surface at the other end, The inner peripheral surface of the portion forms a first cylinder wall, the inner peripheral surface of the other end portion forms a cylinder forming a second cylinder wall, and the outer peripheral surface is a portion on one end side in sliding contact with the first cylinder wall. One piston portion, a second piston portion whose outer peripheral surface is the other end portion in sliding contact with the second cylinder wall, and a concave portion for accommodating a piezoelectric element which is open at the other end surface on the second piston portion side. Slidably held on the cylinder A ring-shaped space for accommodating a coil spring which is located between the two piston portions and is defined between an inner peripheral surface of the cylinder and an outer peripheral surface of the piston; and a second cylinder wall. A sealing member that seals a gap between the outer peripheral surface of the second piston portion, one end of which contacts the bottom surface of the cylinder, and the other end contacts the bottom surface of the concave portion of the piston to extend the piston when extended. A piezoelectric element that urges the opening side of the cylinder, a supply passage provided in the cylinder to supply a cooling liquid to the ring-shaped space, and a cylinder that is housed in the ring-shaped space and whose base ends are the two cylinders. A coil spring that is supported by the cylinder at an intermediate position of a wall and has a biasing end for biasing the second piston portion in a compression direction of the piezoelectric element.

[Action]

With the above configuration, the piston moves in the cylinder by the expansion and contraction of the piezoelectric element, and the fuel is injected. Here, since the seal member is interposed between the second cylinder wall and the second piston portion, fuel does not flow into the piezoelectric element. Coolant is supplied from a supply passage to a ring-shaped space between the outer peripheral surface of the piston portion and the cylinder wall surface of the cylinder to cool the fuel injection device main body including the piezoelectric element.

Embodiment First, an injection pump portion of a distribution type fuel injection pump having the pilot injection device of the present embodiment will be described. In FIG. 2, reference numeral 80 denotes a distribution type fuel injection pump main body. Since the distribution type fuel injection pump main body 80 is known, detailed description is omitted, but the pump housing is driven by a drive shaft rotated by an engine (not shown). The face cam 82 in 81 is driven, and the face cam 82 is formed by the same number of cam rollers 83 as the number of cylinders connected to the face cam 82.
During one rotation, the plunger 84 is reciprocated according to the number of cylinders of the engine, and is also connected to the face cam 82.
Is reciprocated a plurality of times during one revolution according to the number of cylinders of the engine. During the suction process of the plunger 84, when one of the suction grooves 85 formed in the peripheral surface of the distal end portion of the plunger 84 communicates with the suction port 86, the fuel in the fuel chamber 87 is sucked into the pump chamber 88 through the introduction path. During the compression process of the plunger 84, the fuel in the pump chamber 88 is pressurized.
When the supply port 90 communicates with one of the plurality of projecting ports 91, the fuel is supplied to the fuel injection nozzle 94 through the injection passage 92 via the delivery valve 93.

When fuel is supplied to the fuel injection nozzle 94 through the injection passage 92, a spill ring 95 provided on the plunger 84 is provided.
From the end face, the spill port 96 communicating with the vertical hole 89 is released to the fuel chamber, and the fuel in the vertical hole 89 is released from the spill port 96 to the fuel chamber 87. Thus, the supply of fuel to the fuel injection nozzle 94 is stopped. Therefore the spill ring 95 is plunged
By controlling the movement in the axial direction of 84, the fuel injection amount can be controlled.

The pilot injection device 1 is attached to the pump housing 81, and the pilot injection device 1 is configured as shown in FIG.

That is, the pilot injection device 1 includes a cylinder 11 having a cylinder chamber 11a (FIG. 2) communicating with the pump chamber 88,
Piston 12 sliding in cylinder 11 and cylinder wall 111b
A sealing member 13 for sealing the piston and the piston 12, and a piston
It comprises a piezoelectric element laminate 14 interposed between the cylinder 12 and the bottom surface 11b of the cylinder 11, and a supply passage 15 provided in the cylinder 11 for supplying a coolant.

As shown in FIG. 1, the cylinder 11 is formed by screwing a cylindrical first cylinder 111 and a container-shaped second cylinder 112 having a bottom 112b. The first cylinder 111 has a small-diameter first cylinder wall 111a on one of the inner peripheral surfaces and a large-diameter second cylinder wall 111b on the other. The inner peripheral surface of the cylindrical cylinder portion 112a of the second cylinder 112 is fitted to the outer peripheral surface of the first cylinder 111 on the second cylinder wall 111b side as shown in FIG. ing. An O-ring 113 is interposed at the fitting portion between the first cylinder 111 and the second cylinder 112 so as to prevent fuel or the like from flowing in from the outside.

The piston 12 has a cylindrical shape with a bottomed one-end opening having a bottom portion 12a at one end and a flange-shaped portion at the other end. The side having the bottom portion 12a serves as the first piston portion 121, and the flange-shaped portion at the other end serves as the second piston portion 122. This first piston part 1
A ring-shaped space 12b is formed between a boundary portion 123 between the first piston portion 122 and the second piston portion 122 and the second cylinder wall 111b, and a side surface of the first cylinder wall 111a and the second piston portion 1 in the space 12b.
A spring 16 is interposed between the side surface of the cylinder 22 and the piston 16 to urge the piston 12 toward the bottom surface 11b of the cylinder 11. The first piston portion 121 slides along the first cylinder wall 111a, and the second piston portion 122 slides along the second cylinder wall 111b. Further, a seal member 13 composed of an O-ring for preventing fuel leakage is interposed between the second cylinder wall 111b and the second piston portion 122.

Also, the bottom 1 of the piston 12 forming the first piston portion 121
The piezoelectric element laminate 14 is sandwiched between 2a and the bottom 112b of the second cylinder 112. The piezoelectric element laminate 14 is formed by stacking several tens of disk-shaped piezoelectric elements having a property of generating a voltage when a load is applied and causing a distortion when a voltage is applied, with an electrode plate interposed therebetween. This piezoelectric element laminate
The end face of 14 is insulated from other parts by a disk-shaped insulating plate 141. Reference numeral 142 denotes a lead wire.

The first cylinder 111 and the second cylinder 112 have a supply passage 15 for supplying fuel to the ring-shaped space 12b, and the supply passage 15 communicates with a supply pipe 151 provided in the second cylinder 112. Further, the first cylinder 111 has a discharge passage (not shown) for discharging fuel from the ring-shaped space 12b.

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

The distribution type fuel injection pump main body 80 pressurizes the fuel in the pump chamber 88 by the compression action of the plunger 84. The pump chamber 88 and the cylinder chamber 11a are the first cylinder 111 and the piston 12
Pump chamber 88 and cylinder chamber
The fuel in 11a is gradually pressurized and the vertical hole 89 and the injection passage 92
The pressure is sent to the fuel injection nozzle 94 through the valve and the pressure continues to increase until the valve opening pressure of the fuel injection nozzle 94 is reached. At this time, since the piezoelectric element laminate 14 is stretched due to application of voltage to the piezoelectric element, the volume of the cylinder chamber 11a is small.

At this time, the pressure is applied to the distal end surface of the piston 12, and the pressure received by the piston 12 is applied to the piezoelectric element laminate 14 as a load.

Here, since the piezoelectric element has a property of generating a voltage when a load is applied, the piezoelectric element laminate 14 is expanded even when a load is applied.

When the generated voltage is short-circuited at a predetermined timing (at the time when the fuel starts to be injected from the injection nozzle), the generated voltage is removed and the distortion disappears, so that the piezoelectric element laminate 14 contracts instantaneously.

Then, the volume of the cylinder chamber 11a increases, and the pump chamber 88
When the pressure in the cylinder chamber 11a decreases and becomes equal to or lower than the valve opening pressure of the fuel injection nozzle 94, the injection is temporarily stopped.

When the short circuit of the voltage is released and the plunger 84 continues to pump the fuel further, the pressure in the pump chamber 88 and the cylinder chamber 11a increases again, and the fuel injection nozzle 94
The injection is restarted because the pressure becomes equal to or higher than the valve opening pressure. Thus, pilot injection is performed according to the present embodiment.

The state of this pilot injection is shown in FIG. In the figure, a represents pilot injection, and b represents main injection. Note that c indicates a case where pilot injection is not performed.

Next, another operation will be described. Plunger 84 in the same manner as above
Pressurizes the fuel in the pump chamber 88, and the fuel pressure in the pump chamber 88 increases. Then, shortly before the start of fuel injection, a voltage is applied to the piezoelectric element laminate 14. As a result, the piezoelectric element laminate 14 expands and deforms, and the volume of the cylinder chamber 11a decreases. That is, the pressure of the pump chamber 88 communicating with the cylinder chamber 11a increases, and fuel injection is performed. This is pilot injection. Immediately after this, the piezoelectric element stack 14
, The fuel pressure in the pump chamber 88 decreases, and the fuel injection stops. After that, the plunger 84 continues to pressurize the fuel, so that the fuel pressure again increases
When the valve opening pressure reaches 94, the main injection is performed.

Here, the sealing member 13 prevents the fuel from flowing into the concave portion holding the piezoelectric element laminate 14 of the piston 12, and furthermore, the fuel is supplied from the supply pipe 151 to the ring-shaped space 12 b through the supply passage 15 and passes through the discharge passage. Then, the main body of the pilot injection device 1 including the piezoelectric element laminate 14 can be cooled.

As shown in FIG. 4, the flow of fuel from the cylinder chamber 11a into the ring-shaped space 12b is blocked between the first cylinder wall 111a and the first piston portion 121 via the seal member 17, thereby stacking the piezoelectric elements. As a cooling liquid for cooling the body 14, not only fuel but also various fluids such as engine cooling water can be used.

[Effects of the Invention] According to the fuel injection device for a fuel injection pump of the present invention, it is possible to realize that the fuel does not flow into the concave portion of the piston having the piezoelectric element, and that the piezoelectric element that generates high heat can be cooled. Further, a cooling liquid for cooling the piezoelectric element is introduced into a ring-shaped space provided in close proximity to the piezoelectric element between the outer peripheral surface of the piston containing the piezoelectric element and the inner peripheral surface of the cylinder which slidably holds the piston. Since the cooling liquid storage chamber to be used and the spring storage chamber for storing the spring for compressing the piezoelectric element are commonly used, the device configuration is simple and small. Furthermore, since the coil spring having a large number of ring-shaped portions expands and contracts in the axial direction in the cooling liquid storage chamber, the cooling liquid in the cooling liquid storage chamber is strongly agitated, and the movement of the cooling liquid increases. The thermal conductivity from the outer peripheral surface of the piston facing the storage chamber to the cooling liquid is improved, whereby the improvement of the reliability of the piezoelectric element, which is an important point in actual operation, can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a pilot injection device of an embodiment. FIG. 2 is an explanatory view of the distribution type fuel injection pump of the embodiment. FIG. 3 is a diagram showing pilot injection. FIG. 4 is a sectional view showing another embodiment of the pilot injection device of the embodiment. 1 Pilot injection device 11 Cylinder 12 Piston 13 Seal member 14 Piezoelectric element laminate 15 Supply passage 26 Discharge passage

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsushi Hayashi 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (72) Inventor Shinro Oda 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Denso Stock In-house (56) References JP-A-63-134849 (JP, A) JP-A-60-104762 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 51/04 F02M 51/06 F02M 53/00

Claims (1)

(57) [Claims] 1. A fuel injection device for pumping fuel in a pump chamber pressurized by a plunger to an injection nozzle through an injection passage and controlling the pressure of the pressurized fuel to inject fuel. In the injection pump, the fuel injection device has an opening communicating with the pump chamber at one end and a bottom surface at the other end, and an inner peripheral surface of a portion at one end forms a first cylinder wall, and the other end. The inner peripheral surface of the portion is a cylinder that forms a second cylinder wall, the first piston portion whose outer peripheral surface is one end portion that is in sliding contact with the first cylinder wall, and the outer peripheral surface is in sliding contact with the second cylinder wall. A second piston portion which is an end portion, and a piston slidably held by the cylinder having a concave portion for accommodating a piezoelectric element opened on the other end surface on the second piston portion side; The syringe located between the pistons A ring-shaped space for accommodating a coil spring defined between the inner peripheral surface of the piston and the outer peripheral surface of the piston, and a gap between the second cylinder wall and the outer peripheral surface of the second piston portion are sealed. A sealing element, a piezoelectric element having one end in contact with the bottom surface of the cylinder and the other end in contact with the bottom surface of the concave portion of the piston to urge the piston toward the opening side of the cylinder when extended; A supply passage provided for supplying a cooling liquid to the ring-shaped space; and a supply end accommodated in the ring-shaped space, a base end of which is supported by the cylinder at an intermediate position between the two cylinder walls, and a biasing end. A coil spring for urging the second piston portion in a compression direction of the piezoelectric element, a fuel injection pump having a fuel injection device.