JPS58204960A - High speed fuel injection valve - Google Patents

Abstract

PURPOSE:To secure the proper lift amount required as well as to aim at the promotion of miniaturization and lightweight of a high speed fuel injection valve, by forming the valve into a simple structure using plural tilted vibrating reeds, etc., in case of the high speed fuel injection valve using a piezoelectric body. CONSTITUTION:The inside of a valve body 12 is divided into two parts, a piezoelectric body chamber 14 and a fuel chamber 14, and an nlet 16 and an outlet 17 for high pressure fuel are made up at this fuel chamber 15. In time of valve opening, a piezoelectric body 18 produces a mechanical vibration in a thick direction at the same frequency as an impressed high frequency electric field whereby vibrating reeds vibrate. Each of vibrating reeds 28 is tilted to the side opposite to a rod 19 in a direction toward the tip end, and since the tip end is closely pressed to the peripheral surface of a plunger 18, this plunger 18 is shifted to the right (see illustration upside) against the resilient force of a return spring 29. In time of valve closing, a piezoelectric body 25 expands diametrally and thereby the pressing force of each of vibrating reeds 28 against the plunger 18 is weakened so that the plunger 18 shifts to the left.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a high-speed fuel injection valve for injecting high-pressure fuel into an internal combustion engine at high speed by electronic control.

(Prior Art) As a recent fuel injection valve, a high-speed fuel injection valve has been developed that utilizes the electrostrictive expansion and contraction of a piezoelectric body to open and close the valve to improve high-speed response. Such a high-speed fuel injection valve is disclosed, for example, in Japanese Patent Application Laid-Open No. 50-60630, and is shown in FIG.

In FIG. 1, high-pressure fuel is introduced from an inlet 2 formed in a valve body 1, and is injected into the engine from an outlet 3 while the valve is open. 4 is a sheet formed at the outlet 3, 5 is a rod, and 6 is a needle formed at the tip of the rod 5. 7 is a piezoelectric material such as barium titanate or lead zirconate; 8 and 9 are electrodes; the rear end of the rod 5 is fixed to the electrode 8;
. occurs. 10 is a guide when the piezoelectric body is displaced;
Reference numeral 11 denotes a fixing device for the piezoelectric body that determines the position of the piezoelectric body 7 and thus the relative position and lift amount between the needle 6 and the seat 4.

An injection pulse having a pulse width corresponding to the fuel injection amount to be supplied to the engine is given to a control circuit (not shown), and at the rise of the injection pulse, the control circuit connects terminals a and l).
When a constant electric field is applied to the piezoelectric body 7, the piezoelectric body 7 contracts and opens. When the injection pulse falls, no voltage is applied, so the piezoelectric body 7 expands and the valve is closed. Therefore, by using this fuel injection valve, high-speed valve opening and closing responses can be obtained.

However, such conventional high-speed fuel injection valves using piezoelectric bodies are configured to directly open and close the valve in response to contraction and expansion of the piezoelectric body.
The amount of mechanical displacement of the piezoelectric body, that is, the amount of lift of the valve is minute,
At most, only about 30 to 40 μm can be obtained, and the shape of the nozzle is subject to significant restrictions. Therefore, in practice, it is necessary to increase the displacement by increasing the number of laminated piezoelectric layers or adding a displacement amplification mechanism to ensure an appropriate lift amount. Providing the enlarging means increases the size and weight of the entire fuel injection valve, which poses a problem in that it cannot be made smaller and lighter.

(Purpose of the Invention) This invention was made by focusing on the above-mentioned problems of the prior art, and is intended to achieve high-speed valve opening and closing responses by using a piezoelectric material, and to solve the necessary and necessary problems with a simple structure. The purpose is to provide a small, lightweight, high-speed fuel injection valve that secures an appropriate amount of lift.

(Structure, 1, and operation of the invention) Therefore, the feature of the high-speed fuel injection valve according to the present invention is that the rear end of the rod having a needle formed at the tip is fixed to a cylindrical plunger, and a cylindrical piezoelectric body is used. The tips of a plurality of vibrating pieces fixed to the inner surface (3) at an angle are brought into pressure contact with the outer peripheral surface of the plunger, and the piezoelectric body is further urged in the valve closing direction by a return spring, thereby applying a high-frequency electric field to the piezoelectric body. The valve is opened using the bending vibration of the vibrating piece, and the return spring is used to close the valve when the pressure of the vibrating piece is loosened by applying a high-voltage constant electric field to the piezoelectric body.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view of an embodiment of the high speed fuel injection valve according to the present invention. In the figure, the inside of the valve body 12 is divided by a partition wall 13 into a piezoelectric chamber 14 and a fuel chamber 15, and the fuel chamber 15 is formed with an inlet 16 and an outlet 17 for high-pressure fuel.

A cylindrical plunger 18 is disposed in the piezoelectric chamber 14 , and the rear end of a rod 9 passing through the partition wall 13 is fixed to the end face of the plunger 18 on the fuel chamber 15 side.
One end of a support rod 20 (4) passing through the wall of the piezoelectric body chamber 14 is fixed to the end surface opposite to the side to which the rod 19 is fixed. Therefore, the plunger 18 is disposed preferably in the center of the piezoelectric chamber 4 so as to be able to reciprocate in the axial direction. A sealing member 21 is provided at the portion of the partition wall 13 through which the rod 19 passes.
is attached, and the high pressure fuel in the fuel chamber 15 is transferred to the piezoelectric body chamber 1.
4. Make sure that it does not leak. Alternatively, the entire partition wall 13 may be made of a sealing member. The rod 19 extends within the fuel chamber 15, and a needle 22 formed at its tip faces a seat 23 formed at the outlet 17 of the fuel chamber 15. Therefore, if the plunger 18 is moved to the right in the drawing, the needle 22 will move away from the seat 23 to open the valve, and if the plunger 18 is moved to the left, the needle 22 will be seated on the seat 23.

In the piezoelectric body chamber 14, a cylindrical electrode 24-piezoelectric body 25-electrode 26- is arranged around the outer periphery of the cylindrical plunger 18.
The diaphragm 27 is fixed integrally from the outside in this order, and is fixed to the inner wall surface of the piezoelectric chamber 14 so as not to move in the axial direction of the plunger 18. Furthermore, the rear ends of a plurality of inclined rod-shaped vibrating single-way circles are fixed to the inner surface of the diaphragm 27.

As each vibrating single path advances from the rear end fixed to the diaphragm 27 to the free end, the tip ends with the plunger 1.
Opposite side to rod 19 fixed to 8 (towards the right in the drawing)
It is fixed to the diaphragm 27 so as to be tilted at a constant angle α so as to be displaced from the front side, and the tilt angle α is preferably about 6 to 10 degrees.

Then, the tip of each vibrating piece 28 is brought into pressure contact with the outer peripheral surface of the plunger 18. The plunger 18 is normally urged in the valve closing direction by a return spring.

Electrodes 24 and 26 of the piezoelectric body 25 are terminals a and 1, respectively]
It is connected to a high frequency generation circuit (not shown) and a high voltage circuit (not shown) through the circuit. This high frequency generating circuit generates a high frequency electric field of a specific frequency, for example 30 KHz, and the high voltage circuit generates a constant high voltage electric field.

Next, the opening and closing operations of the above-mentioned high-speed fuel injection valve will be explained.

When the valve is open, a high frequency electric field from the high frequency generation circuit is applied to electrode 2.
4 and 26, the piezoelectric body 18 repeatedly expands and contracts in diameter as it contracts and expands in the thickness direction at the same frequency as the applied electric field, producing mechanical vibrations, causing one-way vibration. vibrates. The vibration single path is inclined toward the tip opposite to the rod 19, and the tip is pressed against the outer circumferential surface of the plunger 18, so that the plunger 18 is moved by the return spring 29 due to the high-frequency contraction and expansion vibration of the piezoelectric body 5. It moves to the right in the drawing against the spring force, and the valve opening operation is performed.

When the valve is closed, a constant high-voltage electric field from the high-voltage circuit is applied between the electrodes 24 and 26, and the piezoelectric body 5 expands greatly, increasing its diameter, and the pressing force against the outer circumferential surface of the plunger 18 of the vibrating one-way path is increased. Therefore, the plunger 18 is moved to the left by the spring force of the return spring 29, and a valve closing operation is performed.

Note that the plurality of vibrating single paths should not all be in the same operating state, but should be set so that each vibrating piece operates alternately with a different phase, thereby smoothing the displacement of the plunger 18 when the valve is opened. is possible.

In addition, as mentioned above, since the valve opening operation utilizes the frictional force between the four tips of the vibrating pieces and the circumferential surfaces of lA1 and □ of the plunger 18, it is possible to prevent fuel from leaking from the fuel chamber 15 into the piezoelectric body chamber 14. It is essential to seal.

In addition to the above-mentioned valve opening and closing operations, it is also necessary and important to set the lift amount of the needle 22 to an appropriate value. A control circuit for this purpose will be explained.

FIG. 3 is a block diagram showing an embodiment of the lift amount control circuit. In the figure, numeral 30 is a high frequency generating circuit, which generates the above-mentioned high frequency electric field, and 31 is a triangular wave generating circuit, which outputs a triangular wave signal. 32 is a command circuit that outputs a target value signal for the optimum lift amount, that is, the lift position, of the fuel injection valve. Reference numeral 33 denotes a lift position sensor that detects and outputs the actual lift position, and is attached to the tip of the support rod that supports the plunger 18 protruding from the piezoelectric chamber 14, as shown in FIG. 2, for example. 34 is a deviation detection circuit that compares the target value signal of the lift position from the command circuit 32 and the actual value signal of the lift position from the lift position sensor 33, and compares the sign and magnitude of (-1-1 or (@). 38 is an absolute value circuit,
Outputs the absolute value of the signal based on the deviation. 35 is a comparison circuit that compares the signal from the absolute value circuit 38 and the triangular wave signal from the triangular wave generating circuit 31 at a predetermined period, and generates a data pulse signal (pulse signal - period) according to the magnitude of the signal based on the deviation. signal that changes the ratio of no, i or low)
Output. 36 is an AND circuit that allows the high frequency electric field from the high frequency generation circuit 30 to pass through and is applied to the piezoelectric body only when the output from the comparison circuit 35 is a high signal. A high voltage circuit 37 supplies a high voltage constant electric field, and applies a high voltage constant electric field to the piezoelectric body 5 in response to a signal based on the deviation from the deviation detection circuit 34.

Next, the operation of controlling the lift position will be explained.

In the valve open state, for example, if the actual lift position is smaller than the target value of the lift position, that is, if the actual lift amount is smaller than the target value of the lift amount, the sign is (-1) from the deviation detection circuit 34. -1 and a signal having a magnitude based on the difference (deviation) between the target value and the actual value is output.

The comparison circuit 35 outputs a pulse signal having a data pulse width corresponding to the magnitude of the absolute value of the signal based on the deviation, and during this pulse width, the high frequency electric field from the high frequency generation circuit 30 passes through the AND circuit 36. is applied to the piezoelectric body 25, the plunger 18 is moved in the valve opening direction, and the actual value of the lift position approaches the target value.

Contrary to the above, if the actual lift position is wider than the target value,
The signal based on the deviation is (-) and has a certain absolute value, and a constant high voltage electric field from the high voltage circuit 37 is applied to the piezoelectric body 25, loosening the pressure contact force of the vibrating piece 4, and releasing the return spring. 29 moves the plunger 18 in the valve closing direction, and the actual value of the lift position approaches the target value.

Based on the deviation (if the absolute value of the signal is O, then neither the high-frequency electric field nor the high-voltage constant electric field is applied to the piezoelectric body B, in which case the actual lift position matches or is acceptable to the target position) The position of the plunger 18 is maintained as is.

In this way, the actual lift position is feedbank controlled so that it matches or acceptably matches the target position. □ 1 (Effects of the Invention) As explained above, according to the present invention, a plurality of inclined vibrating pieces are fixed to the inner surface of a cylindrical piezoelectric body, and a rod with a needle fixed to the tip is attached to a cylindrical plunger. fixed,
The tip of the vibrating piece is pressed against the outer circumferential surface of the plunger, the piezoelectric body is urged in the valve closing direction by a return spring, and a high-frequency electric field is applied to the piezoelectric body to open the valve, and a constant high voltage electric field is applied to the piezoelectric body. Since the valve is configured to close using a return spring when the valve is applied to the The lift amount can be increased with a simple structure, there are no restrictions on the shape of the nozzle, and a small and lightweight high-speed fuel injection valve can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional high-speed fuel injection valve, FIG. 2 is a cross-sectional view showing an embodiment of the high-speed fuel injection valve according to the present invention, and FIG.
The diagram shows the lift amount control circuit of the high-speed fuel injection valve shown in Figure 2. Minutes: This is a lock diagram. 12... Valve body 14... Piezoelectric chamber 15... Fuel chamber 16... Inlet 17... Outlet 18... Plunger (11) 19...Lot 22...Needle 23
... Seat part ... Piezoelectric body 24
, 26... Electrode 27... Vibration plate side... Vibration piece 29... Return spring 30... High frequency generation circuit 37... High voltage circuit patent applicant: Nissan Motor Co., Ltd. Patent application agent: Megumi Yamamoto (12) Figure 1 Figure 2 b

Claims (1)

[Claims] A fuel chamber having a piezoelectric chamber and an inlet and an outlet for high-pressure fuel is formed in the valve body, a cylindrical plunger is supported in the piezoelectric chamber so as to be able to reciprocate in the axial direction, and a rod disposed in the fuel chamber is provided. The rear end of the rod is fixed to the plunger, and a needle formed at the tip of the rod faces a seat formed at the outlet of the high-pressure fuel. A diaphragm is fixed to the piezoelectric chamber wall integrally and away from the outer peripheral surface of the plunger in that order from the outside, and rear ends of a plurality of vibrating pieces are fixed to the inner surface of the diaphragm, and the diaphragm is fixed to the rear end of the diaphragm. The vibrating piece is tilted so that the tip is shifted to the opposite side of the rod as it advances toward the free end, and the tip of the vibrating piece is pressed against the outer peripheral surface of the plunger, and the plunger is returned. The spring biases the valve in the closing direction,
A high-speed fuel injection valve configured to perform a valve opening operation when a high frequency electric field is applied to the piezoelectric body, and a valve closing operation by the return spring when a high voltage constant electric field is applied to the piezoelectric body.