JPS58204961A - High speed fuel injection valve - Google Patents

Abstract

PURPOSE:To secure the sufficient lift of a fuel injection valve, by making full use of bending vibrations in plural vibrating reeds installed between the outer surface of a piezoelectric body and the wall inner surface of a valve body, in case of the fuel injection valve using the piezoelectric body. CONSTITUTION:A rod 20 securing a needle 22 to its tip end is locked in a rectangular direction toward the thickness of a piezoelectric body 18, and the tip end of each plural locked vibrating reeds 27 tilted to the thickness direction is closely pressed to the wall inner surface of a valve body, while the piezoelectric body 18 is resiliently energized in a direction of valve oening and set in valve closing motion when a high frequency electric field is given to the piezoelectric body 18. Like this, by impressing the high frequency electric field to the piezoelectroc body 18, these vibrating reeds perform their bending vibrations, making the valve body open, so that the sufficient speedy response and lift of a fuel injection valve can be secured.

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 uses expansion and contraction due to electrostriction of a piezoelectric body to open and close the valve instead of an electromagnetic type, and improves 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;
, 9 are connected to terminals a and b, respectively, and by applying a constant electric field to the electrodes 8 and 9 through terminals a and b, the piezoelectric body 7 undergoes mechanical displacement, that is, contraction or expansion, in the axial direction of the rod 5. arise. 10 is a guide when the piezoelectric body is displaced; 1
Reference numeral 1 denotes a fixing device for the piezoelectric body that determines the position of the piezoelectric body 7, the relative position between the needle 6 and the seat 4, and the amount of lift.

An injection pulse having a pulse width corresponding to the amount of fuel injection to be supplied to the engine is given to a control circuit (not shown), and when a constant electric field is applied between terminals a and terminal A by the control circuit at the rise of the injection pulse, the piezoelectric material 7 contracts and opens the valve. Then, at the falling edge of the injection pulse, no electric field is applied, so the piezoelectric body 7 expands and the valve closes. Therefore, with this fuel injection valve, high-speed valve opening and closing responses can be obtained. ', jl.

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 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 a rod having a needle formed at the tip is fixed to a piezoelectric body that can freely reciprocate in a direction perpendicular to the thickness direction. , the tips of multiple vibrating pieces fixed to the outer surface of the piezoelectric body at an angle are brought into pressure contact with the inner wall of the valve body, the piezoelectric body is further urged in the valve closing direction by a return spring, and a high-frequency electric field is applied to the piezoelectric body. By doing so, 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 constant high-voltage 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 I5, and the fuel chamber 15 is formed with an inlet 16 and an outlet 7 for high-pressure fuel.

A support rod 19 is fixed to one end face perpendicular to the thickness direction of the piezoelectric body 18 disposed in the piezoelectric body chamber 14 , and a support rod 19 is fixed to one end face of the piezoelectric body 8 opposite to the support rod 19 . The rear end of the arranged rod 20 passing through the partition wall 13 is fixed. Therefore, the piezoelectric body 8 and the rod 20 are supported preferably in the center of the piezoelectric body chamber 14 and the fuel chamber 15, respectively, so as to be able to reciprocate in the direction perpendicular to the thickness direction of the piezoelectric body 18 and in the axial direction of the rod 20. be done. A sealing member 21 is attached to the penetrating portion of the partition wall 130 to prevent the high pressure fuel in the fuel chamber 15 from leaking into the piezoelectric chamber 14. Alternatively, the entire partition wall 13 may be made of a sealing member.

Inside the fuel chamber 15, a needle 22 formed at the tip of the rod 20 faces a seat 23 formed at the outlet 17 of the fuel chamber 15. Therefore, if the piezoelectric body 18 is moved to the right in the drawing, the needle 22 separates from the seat 23 and the valve opens, and if the piezoelectric body 18 is moved to the left, the needle 22 seats on the seat 23 and the valve is closed. .

Electrodes 24 and 25 and a diaphragm 26 are fixed to both end faces in the thickness direction of the piezoelectric body 18, and rear ends of a plurality of inclined rod-shaped vibrating pieces 27 are fixed to the outer surface of each of the diaphragms 26. Each vibrating piece 27 is inclined at a constant angle α so that as it advances from the rear end fixed to the diaphragm 26 to the free end, the tip shifts toward the rod 20 (leftward in the drawing). It is preferably fixed to the diaphragm 26 as shown in FIG. Then, the tip of each vibrating piece 27 is brought into pressure contact with the inner wall of the piezoelectric body chamber 14 . The piezoelectric body 18 is normally urged in the valve closing direction by the return spring path.

Electrodes 24 and 25 of piezoelectric material 8 are connected to a high frequency generation circuit (not shown) and a high voltage circuit (not shown) via terminals a and b, respectively. This high frequency generation circuit generates a high frequency electric field of a specific frequency, for example 30KHz,
High voltage circuits generate a constant electric field of high voltage.

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 25, the piezoelectric material 8 repeatedly contracts and expands in the thickness direction at the same frequency as the applied electric field, causing mechanical vibration. , vibrating piece. 7 vibrates.

The vibrating piece 27 is inclined toward the rod 20 side toward the tip, and the tip is pressed against the inner wall surface of the piezoelectric body chamber 14, so that the piezoelectric body 18 is moved by the return spring 28 due to the high-frequency contraction and expansion vibration of the piezoelectric body 18. The valve moves to the right in the drawing against the spring force, and the valve opens.

When the valve is closed, a high-voltage constant electric field from the high-voltage circuit is applied between the electrodes 24 and 25, causing the piezoelectric body 18 to contract significantly, and the pressure contact force of the vibrating piece 27 against the inner surface of the piezoelectric body chamber wall to be relaxed. The piezoelectric body 18 is moved to the left by the spring force of the return spring 28, and a valve closing operation is performed.

Note that the plurality of vibrating pieces 27 are not all in the same operating state, but are set to operate alternately with each vibrating piece changing the phase, thereby smoothing the displacement of the piezoelectric body 18 when the valve is opened. Is possible.

In addition, as mentioned above, since the valve opening operation utilizes the frictional force between the tip of the vibrating piece and the inner wall surface of the piezoelectric body chamber, the piezoelectric body chamber 1
4. It is important to seal the fuel chamber 15 to prevent fuel from leaking.

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.

(7) 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 portion of the support rod 19 that supports the piezoelectric body 18 protruding from the piezoelectric body 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 calculates the sign and magnitude of (-I-1 or (=) 38 is an absolute value circuit,
Outputs the absolute value of the signal based on the deviation. A comparison circuit 35 compares the signal from the absolute value circuit 38 and the triangular wave signal from the triangular wave generation circuit 31 at a predetermined period, and generates a duty pulse signal (pulse signal - period) according to the magnitude of the signal based on the deviation. signal that changes the high or low ratio of
Output. 36 is an AND (8) circuit that allows the high frequency electric field from the high frequency generation circuit 30 to pass through and apply it to the piezoelectric body 18 only when the output from the comparator 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 8 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 deviation detection circuit 34 indicates that the sign is 1000) and the target value. A signal having a magnitude based on the difference (deviation) between the value and the actual value is output. The comparison circuit 35 outputs a signal having a duty 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 18, the piezoelectric body 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 greater 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 18 to loosen the pressure contact force of the vibrating piece 27 and release the return spring. The piezoelectric body 18 is moved in the valve closing direction by the path,
The actual value of the lift position approaches the target value.

When the absolute value of the signal based on the deviation is O, neither the high-frequency electric field nor the high-voltage constant electric field is applied to the piezoelectric body 18, and in this case, the actual lift position matches the target position or is within an acceptable range. Assuming that they match, the position of the piezoelectric body 18 is maintained as it is.

In this way, the actual lift position is feedback-controlled so that it matches or acceptably matches the target position.

(Effect of the invention) 1111:111 As explained above, according to this invention, a mouthpiece with a needle fixed to the tip is fixed in a direction perpendicular to the thickness direction of the piezoelectric material, and the thickness of the piezoelectric material is The tips of multiple vibrating pieces fixed at an angle are brought into pressure contact with the inner wall of the valve body, the piezoelectric body is biased 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. The structure is such that when a constant high-voltage electric field is applied to the piezoelectric body, the return spring closes the valve.In addition to achieving high-speed valve opening and closing responses, it is also possible to stack piezoelectric bodies or create complex designs. The lift amount can be increased with a simple structure without the need to add a displacement enlarging means, 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 drawings]

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.
This figure is a block diagram of the lift amount control circuit of the high-speed fuel injection valve shown in FIG. 2. 12... Valve body... 14... Piezoelectric body chamber 15... Fuel chamber ・1. ] 6...
...Entrance 17...Exit 18...
... Piezoelectric body 20 ... Lot 22 ...
Needle 23... Separate sheet, 5...
Electrode 26... Vibration plate 27...
Vibrating piece...Return spring 30...High frequency generation circuit 37...High voltage circuit Patent applicant Nissan Motor Co., Ltd. Patent application agent Megumi Yamamoto - 1st figure

Claims (1)

[Claims] A fuel chamber having a piezoelectric body chamber and an inlet and an outlet for high-pressure fuel is formed in the valve body, and a piezoelectric body is supported within the piezoelectric body chamber so as to be able to reciprocate in a direction perpendicular to the thickness direction, and the piezoelectric body is disposed within the fuel chamber. The rear end of the rod is fixed to the piezoelectric body, a needle formed at the tip of the rod faces a seat formed at the outlet of the high-pressure fuel, and electrodes and a vibration plate are provided on both end faces of the piezoelectric body in the thickness direction. The rear ends of a plurality of vibrating pieces are fixed to the outer surface of the diaphragm, and the vibration is applied so that as the vibrating pieces move from the rear end toward the free end, the tips shift toward the rod side. The vibrating piece is tilted, the tip of the vibrating piece is brought into pressure contact with the inner wall of the piezoelectric body chamber, the piezoelectric body is urged in the valve closing direction by a return spring, and the valve opens when a high frequency electric field is applied to the piezoelectric body. A high-speed fuel injection valve configured to perform a valve closing operation by the return spring when a constant high-voltage electric field is applied to the piezoelectric body.