JPH0684748B2 - Fuel injection valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection valve using a piezoelectric element, and more particularly to a fuel injection valve suitable for a fuel injection device of an internal combustion engine.

[Conventional technology]

As a fuel injection valve using a piezoelectric element, Japanese Patent Publication Sho-49-604
No. 3, there is a fuel injection nozzle in which the injection nozzle integrally has a valve head at the lower end of a valve rod made of a piezoelectric element, and is pressed against a valve seat of the injection nozzle by a valve spring. Is disclosed.

[Problems to be Solved by the Invention]

 This prior art invention does not consider the following points.

The high displacement piezoelectric element used for stroke control generally has a low Curie temperature (about 150 ° C), and the operating temperature range where performance can be maintained is said to be 1/3 or less of the Curie temperature. Therefore, it is preferable to add a cooling means in consideration of self-heating of the piezoelectric element and temperature rise due to heat conduction from the mounting portion.
It is considered that the fuel is cooled by the fuel in the operating state of the injection valve. However, since there is no fuel flow after the operation is stopped, there is no cooling means, and a temperature rise due to heat conduction from the mounting portion is considered, which is unreliable from the viewpoint of protecting the piezoelectric element. Considering an internal combustion engine in particular, it is said that the maximum temperature of the mounting portion is about 140 ° C., and it is considered difficult to apply because the mounting portion has a large heat capacity.

Further, the one described in Japanese Patent Publication No. Sho 49-6043 only supplies the fuel to the valve seat from the supply port through the passage between the laminated piezoelectric element and the body of the injection nozzle. No consideration is given to the structure for giving the swirling motion, the structure for cooling the fuel injection valve, and the cooling means after the operation is stopped.

An object of the present invention is to solve such a drawback and to construct an inward opening seat valve by using a piezoelectric element. That is, a pulse positive voltage is applied to the piezoelectric element, and the mechanical displacement thereof opens and closes the injection hole to control the flow rate to form an injection valve that ejects fine liquid droplets, and also adds cooling means for the piezoelectric element. Then, it is to improve the reliability of the piezoelectric element by suppressing the performance deterioration due to the temperature rise.

[Means for Solving the Problems]

In order to achieve the above-mentioned items, a fuel injection valve of the present invention is a hollow cylindrical laminated piezoelectric member formed by laminating piezoelectric elements, and is joined to the laminated piezoelectric member in surface contact and fixed to a valve case. A support member having a flange, an injection hole provided at the tip of the valve case, a fuel inflow hole formed on the upstream side of the injection hole and a tip between the fuel inflow hole and the injection hole. In a fuel injection valve having a valve body that makes contact with a seat portion formed by, and a needle that reciprocates in the support member, the fuel injection valve is provided at an arbitrary position between the injection hole side end surface of the laminated piezoelectric member and the valve body. A second flange and a spring member provided between the flange and the second flange so as to close the seat portion, and a plurality of the fuel inflow holes are formed so as to give a swirling motion to the fuel. Is
A swirl chamber is formed between the downstream side of the fuel inflow hole and the seat portion, and a flow path is configured to flow the fuel flowing from the fuel inflow hole to the fuel return hole when the seat portion is closed. , The fuel tank and the fuel injection valve are connected by a fuel return pipe via a fuel supply pipe and a flow control valve, and the flow rate control is performed even after the engine is stopped so that the temperature of the fuel injection valve becomes equal to or lower than a set temperature by a control circuit. It is characterized by controlling the valve.

[Action]

A hollow cylindrical laminated piezoelectric member including a large number of piezoelectric elements,
A needle is arranged inscribed in both of the hollow valve cases having an injection hole at the most distal end, and the needle is vibrated in conjunction with the mechanical displacement of the laminated piezoelectric member to control the opening and closing of the injection hole. Therefore, it is possible to open and close the injection hole at high speed to accurately control the flow rate, and it is possible to control the flow rate in the injection region (pulse ON time 0.5 to 1.0 ms) in which the valve opening time is short.

Further, in the operating state, a fuel amount that does not affect the fuel injection control can be recirculated through the inside of the needle or the periphery of the laminated piezoelectric member, and the temperature rise of various members forming the fuel injection valve. It is possible to suppress the change, and by controlling the temperature below the set temperature, it is possible to prevent changes in the injection flow rate due to thermal expansion of the members and to prevent bubbles from entering the fuel, and to improve the reliability of the laminated piezoelectric member consisting of multiple piezoelectric elements with respect to temperature. be able to. Further, after the engine is stopped, the temperature rise of the fuel injection valve due to the residual heat can be suppressed by controlling the fuel that recirculates inside or outside the fuel injection valve according to the temperature, and the reliability of the temperature of the members is extremely high. Is to be. Further, since a plurality of fuel inlets are provided to provide a swirling flow and a swirl chamber is provided, the swirling motion can be imparted to the pressure fluid even when the valve is closed, so that a thin film spray shape can be obtained without impairing kinetic energy. Therefore, atomization can be performed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a sectional view showing a second embodiment of the present invention.
The drawing shows an embodiment showing a means for controlling the amount of fuel circulation in a state where the fuel injection valve of either the first embodiment or the second embodiment is installed in the intake passage of the engine.

In FIG. 1, 20 is a hollow cylindrical laminated piezoelectric member in which a large number of piezoelectric elements are laminated, 21 is a supporting member inserted in the laminated piezoelectric member 20, and has a flange 21a having a thread groove. twenty two
Is a hollow valve case having an injection hole 22a at the most distal end and a plurality of inflow holes 22b provided so as to be adjacent to and communicate with the injection hole 22a, and 23 is arranged inscribed in the support member 21 and the valve case 22. The needle is fitted to the valve case 22 side with a relatively small gap. For example, the gap is about 10 microns. 23a is a sheet formed between the injection hole 22a and the inflow hole 22b of the valve case 22 in the vicinity of the tip of the needle 23, and is constituted by surface contact or line contact. Reference numeral 23b is a flange provided on the other end surface of the needle 23, and is mechanically (for example, caulked) coupled after the laminated piezoelectric member 20 is inserted. Reference numeral 23c is a thick portion provided on the needle 23 in the vicinity of the flange 23b and is inscribed in the support member 21 to prevent the runout of the needle 23. 23d is a support member 21
Is provided between the flange 21a and the valve case 22 corresponding to this surface, and the position is another small diameter flange close to the valve case 22, and 24 is between the small diameter flange 23d and the flange 21a of the support member 21. Needle 23 with the provided compression spring
The seat 23a is pressed against the valve case 22. 25 is a flange 23d
The sealing material provided between the inner surface of the valve case 22 and the corresponding inner surface of the valve case 22 prevents the flow of the pressure fluid toward the laminated piezoelectric member 20. 26 is a swirl chamber formed upstream of the seat 23a of the needle 23, 27 is a valve cap fixed to cover the tip of the valve case 22, 28 is a pressure fluid flow path formed in the valve cap 27,
A pressure fluid inlet 29 is connected to a fuel supply pipe (not shown). Reference numeral 32 is a conducting wire for supplying power to the laminated piezoelectric member 20.
With such a configuration, the seat 23a of the needle 23 is pressed by the restoring force of the compression spring, and fuel leakage of the pressurized fluid to the outside is prevented. The pressing force (sheet force) can be adjusted by selecting the spring constant of the compression spring. FIG. 2 is a sectional view taken along the line AA in FIG. 1, showing an inflow hole 22b that gives a swirling motion to the pressure fluid. Further, this embodiment is provided with a cooling means for the laminated piezoelectric member. The main part will be described below. Reference numeral 33 is a needle having a fuel passage 33a therein, and 34 is a valve lid for opening a fuel return hole 34a. The fuel passage 33a is a needle
From the upstream side of the small diameter flange 23d of 33, it communicates with the fuel return hole 34a provided in the valve lid 34.

Reference numeral 35 is a stopper provided between the valve lid 34 and the flange 23b of the needle 33, and 36 is a sealing material provided between the valve lid 34 and the flange 23b of the needle 33, which blocks the flow of fuel to the laminated piezoelectric member 20 side.

FIG. 3 is a sectional view showing a second embodiment of the present invention. The second embodiment is similar to the first embodiment in that it is provided with cooling means for a laminated piezoelectric member. In this embodiment, fuel is supplied into the laminated piezoelectric member. Differences from the first embodiment will be described below. First, the sealing materials 25 and 36 provided to prevent the flow of fuel to the laminated piezoelectric member side are unnecessary in the second embodiment. Further, the fuel passage 33a provided inside the needle 33 is also unnecessary. Reference numeral 37 denotes a fuel passage provided in the support member 21, which is formed by cutting a part in the circumferential direction into an elongated shape in the axial direction, and induces the flow of fuel to the laminated piezoelectric member side.

The same reference numerals in FIGS. 1 to 3 indicate the same parts.

The operation of the above configuration will be described below. First
In the figure, when a pulse voltage is applied to the laminated piezoelectric member 20, the laminated piezoelectric member 20 is displaced (stretched) according to the ON time of the pulse. This displacement is in the direction of the dotted arrow shown in the figure. The displacement response is usually 0.1 msec. (The valve opening time of the electromagnet method is about 1 msec.) This is due to the high natural frequency of the piezoelectric element. The needle 23 is pushed up by the expansion of the laminated piezoelectric member 20, and the seat 23 of the needle 23
a separates from the valve case 22. As a result, the injection hole 22a provided in the valve case 22 is opened. At this time, the pressure fluid passes through a conveying device such as a pressure pump (not shown) and the pressure fluid inlet 2
9. From the pressure fluid passage 28 to the swirl hole 23a. The pressure fluid given the swirling motion in the swirling hole 23a flows toward the spray hole 22a from the gap of the sheet 23a without impairing the kinetic energy held by the pressure fluid collected in the swirl chamber 26, and the spray hole 22a
It is injected from the outside. Since the opening / closing valve operation of the injection hole 22a is performed at high speed, the injection amount can be accurately controlled. Further, since the injected fuel is given sufficient swirling energy, it becomes a thin film spray shape having a spread and is subdivided into fine droplets. On the other hand, when the pulse voltage applied to the laminated piezoelectric member 20 is turned off, the needle 23 is instantly returned to its original position by the restoring force of the compression spring and presses the sheet 23a. As a result, the injection hole 22a provided in the valve case 22 is closed. At this time, the injection of the pressure fluid to the outside is stopped.

In FIG. 3, the pressure fluid that has flowed into the swirl chamber 26 from the pressure fluid inlet 29 and the pressure fluid passage 28 through the fluid hole 22b provided in the valve case 22 is injected through the gap between the seat 23a of the needle 33 and the valve case 22 into the injection hole. It is separated into a flow reaching 22a and a flow passing through the fuel passage 33a from the gap between the needle 33 and the valve case 22 to the fuel return hole 34a. Each flow rate is determined by the injection amount to be discharged from the injection hole 22a to the outside. The amount of fuel flowing into the fuel return hole 34a is such that all of the supplied fuel flows to the fuel return hole 34a when the seat 23a of the needle 33 is closed, that is, when the pulse voltage is OFF. Therefore, the valve case 22,
The valve cap 27 and the needle 33 are forcibly cooled by the fuel to suppress the temperature rise of the laminated piezoelectric member 20. In addition,
The fuel injected from the injection holes 22a to the outside is given sufficient swirling energy as in the first embodiment, and is thus divided into fine droplets in the form of a thin film spray having a spread.

The operation of the second embodiment is almost the same as that of the first embodiment, except that the laminated piezoelectric member 20 is provided with a cooling means. Differences from the similar first embodiment will be described below. Describe. In FIG. 3, pressure fluid inlet 29, pressure fluid passage 28
When the pressure fluid that has flowed into the swirl chamber 26 through the inflow hole 22b provided in the valve case 22 reaches the fuel return hole 34a, from the fuel passage 37 provided in the support member 21 that supports the laminated piezoelectric member 20, the laminated piezoelectric material is provided. It flows around the member 20. Therefore, the flow of the fuel is generated in the entire area of the inside of the injection valve, the cooling is promoted, and the temperature rise of the laminated piezoelectric member 20 is suppressed.

As described above, in the first embodiment and the second embodiment, the cooling of the members constituting the injection valve is promoted by the recirculation of the fuel, so that the control of the fuel to be injected without the performance drop due to the temperature rise is performed. Can be performed with extremely high precision.

FIG. 4 shows an embodiment in which the fuel injection valve shown in FIG. 1 or 3 is installed in the intake passage of the engine, and means for controlling the flow rate of the recirculated fuel is added.

As an intake system, an intake passage 100 is provided with an air filter upstream thereof, a throttle valve (both not shown) for controlling the intake air amount by opening and closing, and an ignition portion 120 of a spark plug 110 downstream thereof. An intake hole 140 that communicates with the fuel chamber 130 to be installed and an intake valve 15 that controls the opening and closing of the intake hole 140.
Equipped with 0. The intake passage 100 is provided upstream of the intake valve 150.
Mounting hole 1 on wall 170 (intake manifold) of
The fuel injection valve 190 of the present invention is attached to the intake valve 80.
Injection is possible in the direction of 50 valve seats 200. On the other hand, in the fuel supply pipe 210 as a fuel supply system, a pressure regulator 230 having a function of maintaining a constant pressure of fuel supplied to the fuel injection valve 190 is provided upstream thereof, and a pressure pump 240 and a filter are provided further upstream. 250 and a fuel tank 260 are provided. When regulated by pressure regulator 230, excess fuel returns to fuel tank 260 via fuel path 270. An arrow 220 in the figure is a fuel path supplied to the fuel injection valve 190. Further, a flow rate control valve 290 that controls the recirculation amount is provided downstream of the fuel return pipe 280 of the fuel injection valve 190, and the fuel that has flowed out of the flow rate control valve 290 returns to the fuel tank 260. The arrow 300 in the figure indicates the fuel path for recirculation. 310 is a flow control valve 290
Is a control circuit for controlling the operation of the.

In such a configuration, the gasoline engine draws a predetermined amount of intake air into the fuel chamber 130 through the intake passage 100 and the intake valve 150 in the intake stroke. A desired amount of fuel is sprayed from the fuel tank 260 through the filter 250, the pressure pump 240, the pressure regulator 230, and the fuel injection valve 190 toward the valve seat 200. This is diffusively mixed with the intake air to form a mixture of fuel and air having a predetermined mixing ratio. In the fuel chamber 130, the air-fuel mixture is sucked and compressed in the compression process, and then the spark plug 11
Ignition combustion is performed by 0, and the combustion is completed properly. When the engine maintains the operating state, the temperature around the combustion chamber 130 gradually rises due to heat transfer. Fuel injection valve 190
It is said that the temperature of the wall portion 170 of the mounting hole 180 is about 140 ° C. at maximum. Fuel injection valve 1 by conduction heat from wall 170
When the temperature of 90 reaches a certain set temperature, the control circuit 310 operates the flow control valve 290 to start the recirculation of fuel. The input signal to the control circuit 310 is in this case the temperature inside or outside the fuel injection valve 190. That is, the fuel injection valve 190
Control circuit 31 as the temperature inside or outside
The output signal from 0 operates to further increase the passage area of the flow control valve 290. Control circuit 310
The input signal of is acceptable as long as the operating condition of the engine can be grasped.

On the other hand, when the engine is stopped, the fuel injection from the fuel injection valve 190 toward the valve seat 200 is immediately stopped, but the fuel path flowing from the inside of the fuel injection valve 190 through the fuel return pipe 280.
Fuel flows to the 300 even after the engine is stopped, and the fuel injection valve 1
It will not stop until the temperature of 90 drops below the set temperature.

For this reason, the temperature rise of various members constituting the fuel injection valve can be suppressed and can be made equal to or lower than the set temperature, so that the temperature rise of the piezoelectric element member can be particularly suppressed and made equal to or lower than the set temperature. As a result, it is possible to prevent changes in the injection flow rate due to thermal expansion of the members and to prevent bubbles from entering the fuel, and it is possible to increase the reliability of the laminated piezoelectric member including a large number of piezoelectric elements with respect to temperature.

With such a configuration, the fuel injection valve 190 can be cooled more appropriately according to the operating state of the engine, and as a result, optimum fuel injection for operating the engine can be obtained.

Incidentally, FIG. 5 shows a bridge circuit 10 which serves as an electric field applying means for applying an electric field to the piezoelectric element and inverting its polarity. 10a is an input terminal to an injection pulse corresponding to the time width fuel injection amount is added, 10b is a pulse transformer with the injection pulse positive trigger pulse to the output terminal 10b ₁ to the rising time of,
Generating a negative trigger pulse to the output terminal 10b _2, also the rise time is to generate the opposite polarity of the trigger pulse, respectively. 10c, 10d, 10e and 10f are thyristors, and + B is a positive voltage electrode terminal. The operation of the above configuration will be described. When the injection pulse arrives at the input terminal 10a, the pair of thyristors 10c and 10d become conductive and the other pair of thyristors 10e and 10f are cut off by the trigger pulse of the output terminals 10b ₁ and 10b ₂ generated at the rising time. Has become.

〔The invention's effect〕

As described above, according to the present invention, firstly, the needles are arranged inside both the hollow cylindrical laminated piezoelectric member including a large number of piezoelectric elements and the hollow valve case having the injection hole at the most distal end. It is possible to configure an inward opening seat valve that controls the opening and closing of the injection hole by vibrating the needle in conjunction with the mechanical displacement of the laminated piezoelectric member, and as a result, opening and closing the injection hole at high speed to control the flow rate. In addition to performing with high accuracy, the injection region with a short valve opening time (pulse ON time 0.5 ~
It enabled flow rate control in 1.0 ms).

Secondly, the amount of fuel that does not affect the fuel injection control in the operating state is circulated through the inside of the needle or around the laminated piezoelectric member, and the temperature of the fuel injection valve is controlled by the control circuit even after the engine is stopped. Since the flow control valve is controlled so as to be equal to or lower than the set temperature, as a result, it is possible to suppress the temperature rise of various members constituting the fuel injection valve and to set the temperature to be equal to or lower than the set temperature. The rise can be suppressed and the temperature can be kept below the set temperature. As a result, it is possible to prevent changes in the injection flow rate due to thermal expansion of the members and to prevent bubbles from entering the fuel, and it is possible to increase the reliability of the laminated piezoelectric member including a large number of piezoelectric elements with respect to temperature. Thirdly, the means for controlling the amount of recirculation of the fuel is provided, and as a result, the operating state of the engine can be accurately grasped and the optimum fuel control can be performed.
Further, after the engine is stopped, the temperature rise of the fuel injection valve due to the residual heat is suppressed by controlling the fuel that recirculates depending on the temperature inside or outside the fuel injection valve, and the reliability with respect to the temperature of the members is extremely high. Is to be. Therefore, a very high effect can be obtained in terms of improving the life and reliability of the fuel injection valve. In addition,
The fuel injection valve and the fuel recirculation amount control means of the present invention,
Even if it is applied to various industrial fields, the actual profit can be highly obtained. Further, since the swirl chamber is provided, the pressure fluid that has been given swirling motion in the swirl hole even when the valve is closed is collected in the swirl chamber, so that the kinetic energy held by the pressure fluid is not impaired, and Sufficient swirling energy is given to the inflowing fuel, and a spray-like thin film having a spread is formed into fine droplets, which improves fuel efficiency.

[Brief description of drawings]

1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, FIG. 3 is a sectional view showing a second embodiment of the present invention, and FIG. Sectional drawing which shows one Example which equips the intake passage of an engine with the fuel injection valve of the 1st Example or 2nd Example of this invention, and added the control means of the amount of recirculation | reflux of fuel,
FIG. 5 shows a control circuit of a fuel injection valve of a conventional example. 20 ... Multilayer piezoelectric member, 22 ... Valve case, 22a ... Injection hole, 22b ... Inflow hole, 23, 33 ... Needle, 33a ... Fuel passage, 34a ... Fuel return hole, 310 ... Control circuit , 29 …… Flow control valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeyuki Yamazaki Inventor Shigeyuki 502 Jinritsucho, Tsuchiura City, Ibaraki Prefecture Hiritsu Manufacturing Co., Ltd.Mechanical Research Laboratory (72) Tsuneo Suga 502 Jinritsucho, Tsuchiura City, Ibaraki Prefecture Hiritsu Co., Ltd. (56) References JP-A-55-164771 (JP, A) JP-A-56-7911 (JP, A) JP-A-59-70871 (JP, A)

Claims (1)

[Claims] 1. A hollow-cylindrical laminated piezoelectric member formed by laminating piezoelectric elements, a support member having a flange joined to the laminated piezoelectric member in surface contact and fixed to a valve case, and the valve case. An injection hole provided at the tip of the valve, a fuel inflow hole formed on the upstream side of the injection hole, and a valve main body at the tip that contacts a seat formed between the fuel inflow hole and the injection hole. In a fuel injection valve including a needle that reciprocates in the support member, a second flange provided at an arbitrary position between the injection hole side end surface of the laminated piezoelectric member and the valve body and the seat portion are closed. As described above, a plurality of the fuel inflow holes are formed so as to give a swirling motion to the fuel, and the spring member is provided between the flange and the second flange. A swirl chamber is formed between In addition, a flow path is configured so that the fuel flowing from the fuel inflow hole flows to the fuel return hole when the seat portion is closed, and the fuel tank and the fuel injection valve form a fuel supply pipe and a flow control valve. A fuel injection valve, characterized in that the flow control valve is controlled by a control circuit even after the engine is stopped so that the temperature of the fuel injection valve becomes equal to or lower than a set temperature by being connected by a fuel return pipe.