JP2000128083A - Nozzle driving unit for small ship - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically powered nozzle driving unit for a small ship which has a small actuator with excellent responsiveness. SOLUTION: This nozzle driving unit 6 for controlling a trim angle of a jet propulsion nozzle for a small ship is provided with a grip part 7, an actuator part 8, and a control part 9. The grip part 7 is provided with a sensor which outputs the electric signal corresponding to the rotational position of a grip 3. A motor 20 for the actuator part 8 is a direct acting type motor having an output shaft 27 which moves in the axial direction when the rotor rotates. The control part 9 makes the motor 20 to operate according to the rotational position of the grip 3 and moves a push-pull cable 10 through the output shaft 27. The control part 9 comprises an engine misfire control function which forces the engine to misfire while the actuator part 8 is operating to reduce jet reaction force from a nozzle 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle driving device for adjusting a vertical angle (trim angle) of a jet propulsion nozzle of a small boat such as a watercraft.

[0002]

2. Description of the Related Art A jet propulsion nozzle of a personal watercraft jets water pressurized by a pump to the rear of the hull, and the vertical angle (trim angle) of the jet propulsion nozzle greatly affects the maneuverability. I do. 2. Description of the Related Art Conventionally, there has been known a nozzle driving device capable of changing a trim angle of a jet propulsion nozzle according to a boat maneuvering state, for example, at the time of starting, turning, or riding two people.

[0003] Nozzle driving devices for operating a trim angle of a small boat such as a watercraft are broadly classified into a mechanical type using a nozzle driving cable and an electric type using a motor. In terms of surface, it is said that mechanical type is advantageous. For example, the nozzle driving device of the personal watercraft 1 (also referred to as a personal water vehicle or watercraft) shown in FIG. 13 connects a nozzle driving cable (not shown) to a grip 3 provided on the handlebar 2. The nozzle drive cable is operated by rotating the grip 3 to change the trim angle of the nozzle (water jet port) 4. The inclination of the nozzle 4 can be changed in at least three stages. That is, a neutral position (NEUTRAL), an up position (UP), and a down position (DOWN).
A restoring force (reaction force) acts on the nozzle 4 due to the thrust of the water jet during maneuvering.

In this type of mechanical nozzle driving device, since the operating force of the grip 3 is directly transmitted to the nozzle 4 via a nozzle driving cable or the like, the reaction force due to the water jet of the nozzle 4 is transmitted via the nozzle driving cable. Acts on grip 3. For this reason, a large watercraft or the like requires a considerably large gripping operation force when the jetting power of the nozzle 4 is large, so that there is a problem that it is difficult to operate the trim angle.

On the other hand, the electric nozzle driving device includes a grip portion provided with a grip position detecting mechanism for detecting a rotational position of the grip, and a motor which operates based on an electric signal output from the grip position detecting mechanism. It comprises an actuator unit provided, a force transmission cable for transmitting the movement of the actuator unit to the nozzle, and the like. Such a motor-driven nozzle driving device has an advantage that it can relatively easily cope with a large watercraft or the like by using a high-output motor for the actuator section.

[0006]

In the case of an electric nozzle driving device, a quick response and low cost are required instead of a mechanical type, but in the case of a large jet propulsion nozzle, the nozzle side has a considerably high load. Therefore, in order to improve the responsiveness, an actuator unit using a large motor is inevitably needed, which increases the cost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a motor-driven nozzle driving device having a small-sized and highly responsive actuator section.

[0008]

According to a first aspect of the present invention, there is provided a nozzle driving device for achieving the above object, wherein an electric signal corresponding to a grip position is transmitted from a grip position sensor to a control unit. The control unit operates the motor of the actuator unit based on the output signal, and performs a trim angle control of the nozzle via a force transmitting member such as a push-pull cable. The motor employed in this actuator section is a direct-acting motor that directly converts the rotational movement of the rotor that rotates when the coil section is excited into axial movement of the output shaft. Can be stored compactly.

According to a second aspect of the present invention, a motor of the actuator section has a first sensor for detecting a reference position of the output shaft and a second sensor for detecting rotation of the rotor. The control unit controls the rotation of the motor so that the nozzle is at a desired trim angle position based on the outputs of the first sensor, the second sensor, and the grip position sensor. Includes controlling. The present invention also includes that the grip portion includes a lock mechanism for stopping the grip at a position corresponding to the trim angle and the grip position sensor.

According to a fourth aspect of the present invention, the control unit includes a misfire output circuit having an engine misfire control function for forcibly causing the engine to misfire while the motor is operating, thereby reducing the reaction force of the nozzle. With this arrangement, the engine output is automatically reduced while the actuator is operating. Thereby, the reaction force of the water jet of the jet propulsion nozzle is temporarily reduced, and the nozzle can be driven with a relatively small force.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

The jet propulsion nozzle 4 shown in FIG. 1 is provided at the rear of the hull of a small boat (for example, the watercraft 1 shown in FIG. 13). The jet propulsion nozzle 4 can swing up and down around a shaft 5, and is driven by an electrically driven nozzle driving device 6 described below at a neutral position (NEUTRAL) in a vertical direction as a boundary. The trim angle can be adjusted to a total of five levels, i.e., two levels and two levels on the down (DOWN) side. However, the number of switching of the trim angle may be other than five, or may be configured so that the trim angle can be changed steplessly (continuously).

The nozzle driving device 6 controls the grip portion 7 having the grip 3 provided on the left end portion of the steering handlebar 2, the actuator portion 8 provided on the hull side, and the control for controlling the actuator portion 8 and the like. Part 9 and push-pull cable 10 connected to jet propulsion nozzle 4
It is configured with such as. Push-pull cable 1
Numeral 0 indicates a rod 12 functioning as a force transmitting member inserted through the outer tube 11, and when the rod 12 is pulled in the direction of arrow F1 in FIG. 1, the nozzle 4 is driven, for example, to the up side, When the rod 12 is pushed in the direction of the arrow F2, the nozzle 4 moves, for example, to the down side.

As shown in FIG. 2, a cylindrical grip inner 13 which is a core material of the grip 3 is rotatably held around an axis of the handle bar 2 by a housing 14 fixed to the handle bar 2. A first gear 15 such as a spur gear is provided coaxially with the grip inner 13 at an end of the grip inner 13. As shown in FIG. 3, a second gear (for example, a spur gear) 16 meshes with a tooth portion 15a of the first gear 15. The number of teeth of the second gear 16 is smaller than the number of teeth of the first gear 15, and when the grip 3 is rotated, the rotation is accelerated from the first gear 15 to the second gear 16 at a constant ratio. To be communicated. Note that the first gear 15 only needs to have the teeth 15a only in a range where the first gear 15 meshes with the second gear 16, so that the teeth 15a need not be provided on the entire circumference of the first gear 15.

A shaft 17a of a grip position sensor 17 functioning as a means for detecting the rotational position of the grip 3 is provided coaxially with the second gear 16. One example of the grip position sensor 17 is a potentiometer, which is fixed to the housing 14 by screws 18 as shown in FIG. Therefore, when the grip 3 is rotated, the gears 15, 1
6, the shaft 17a of the sensor 17 rotates, and the grip 3
, Ie, an electric signal used for trim angle control.
In the case of this embodiment, the electric signal is an analog signal.

The trim angle control of the nozzle 4 is as follows.
For example, UP1, UP2, neutral, DOWN1, DOWN2
Since the five types of positions are switched, the grip position sensor 1
Instead of a stepless sensor such as the potentiometer, a plurality of contact switches that operate independently according to the rotational position of the grip 3 may be used as the switch 7.

As shown in FIGS. 5 and 6, the actuator section 8 has a motor 20. An example of the motor 20 is a cover 22 fixed to the frame 21 of the actuator section 8.
And a coil part 23 provided inside the cover 22, a hollow rotor 24 that rotates when the coil part 23 is energized (excited), and a male screw part screwed into a female screw part 25 formed at the center of the rotor 24. An output shaft 27 having an output shaft 26 is provided. The motor 20 is a direct-acting motor in which the output shaft 27 advances in the axial direction according to the rotation direction and the rotation amount when the rotor 24 rotates.

A base 30a of a bellows 30 functioning as a dust cover is fixed to an end of a cover 22 of the motor 20. The tip 30b of the bellows 30 is connected to the output shaft 2
7 is fixed to an intermediate portion in the axial direction. The bellows 30 is expandable and contractible in the axial direction of the output shaft 27, and the bellows 30 expands and contracts in the axial direction integrally with the output shaft 27 when the output shaft 27 moves in the axial direction.

One end 12a of the rod 12 of the push-pull cable 10 is connected to a tip 27a of the output shaft 27 via a relay nut 31. Push-pull cable 1
One end (hub) 11 a of the outer tube 11 is fixed to the frame 21. Therefore, when the output shaft 27 moves in the axial direction, the rod 1 moves with respect to the outer tube 11.
2 moves in the pull direction (direction indicated by arrow F1) or the push direction (direction indicated by arrow F2). As shown in FIG. 1, the other end 12b of the rod 12 is connected to a mechanism 4a for performing a trim angle operation of the nozzle 4. With such a configuration, when the motor 20 operates, the rod 12 of the push-pull cable 10 moves in the pulling direction or the pushing direction, and the trim angle of the nozzle 4 can be changed up or down.

As shown in FIG. 5 and the like, the motor 20 includes a first sensor 33 functioning as reference position detecting means, and a detected member 34 provided on the output shaft 27. In this embodiment, a mechanical microswitch is used as the first sensor 33, but a magnetic sensor or an optical sensor may be used. When the output shaft 27 is at the reference position (when the output shaft 27 is deepest in the female screw portion 25 of the rotor 24 as shown in FIG. 5), the detected member 34 , The contact of the sensor 33 is turned on. FIG.
When the output shaft 27 is located at a position other than the reference position as shown in FIG.

Inside the cover 22 of the motor 20, there is provided a second sensor 35 functioning as a means for detecting the amount of movement (the amount of rotation) of the motor 20. One example of the sensor 35 is a magnetic element. The rotor 24 is provided with a magnet 36 at a position that can face the sensor 35.
When the magnet rotates, the sensor 35 generates an electric pulse each time the magnet 36 passes near the sensor 35.

When the rotor 24 makes one rotation, the female screw 25
Is moved in the axial direction by an amount equivalent to the pitch of the threaded portions 25 and 26. Therefore, by counting the number of pulses generated by the second sensor 35, the relative movement amount of the output shaft 27, that is, the push-pull cable 1
The movement amount of the zero rod 12 can be detected. The minimum unit of this movement amount is determined by the pitch of the screw portions 25 and 26. Therefore, for example, by providing a plurality of magnets 36 at equal intervals on the circumference of the rotor 24, the minimum detection unit of the movement amount can be further reduced. Note that the second sensor 35 is not limited to a magnetic element as in the above-described embodiment, but may be an optical element, for example.

When performing the trim angle control of the nozzle 4, it is necessary to detect the absolute position of the output shaft 27 of the actuator section 8. In the case of this embodiment, the relative movement amount of the output shaft 27 from the reference position (the state of FIG. 5) is detected by using the sensors 33 and 35 and stored in the control unit 9 so that the output shaft 27 can be detected. Is used to calculate the absolute position. Instead of incorporating the detection mechanism including the sensors 33 and 35 in the motor 20, a similar detection mechanism may be provided outside the motor 20, or detection means capable of detecting the absolute position of the output shaft 27 may be used. You may.

The control section 9 has a control circuit 9a shown in FIG. The control circuit 9a operates using the battery B mounted on the personal watercraft 1 as a power supply. Control circuit 9
The central control unit 9b of FIG. 1A uses a microcomputer or the like, and controls the entire control in accordance with a program incorporated in advance.

In this embodiment, the grip position is input by the grip position sensor 17 as an analog voltage corresponding to the rotation angle of the grip 3. This analog signal is converted into a digital value in the control unit 9, and according to the digital value, in the program of the central control unit 9b, the above-described five types of trim angles (UP1, UP2, neutral, DO)
WN1, DOWN2).

The amount of movement of the output shaft 27 of the actuator section 8 is relatively detected by the number of pulses detected by the second sensor 35. Since there is no difference in the pulse with respect to the moving direction of the output shaft 27, it is necessary to recognize the reference position (the state shown in FIG. 5) and distinguish the moving direction in order to know the absolute position of the output shaft 27. Therefore, in this embodiment, processing is performed on a program as described below.

First, when the reference position signal is on, the integrated position of the actuator is cleared to zero. Next, when the reference position signal is in the OFF state, when the motor 20 is rotating in the direction away from the reference position, the sensor 35 adds 1 to the actuator integrated position each time a pulse is generated. Conversely, when the actuator rotates in the direction approaching the reference position, the actuator integrated position is decremented by one. This value is used as the amount of movement from the reference position.

The control section 9 also includes a driver circuit 37 capable of driving the actuator section 8 in both directions, a circuit 38 for taking in engine rotation pulses, and a misfire output circuit 39 for forcibly reducing engine rotation.

As shown in FIG. 8 to FIG.
Has a lock mechanism 40 and a detent mechanism 41. The lock mechanism 40 includes a lock lever 50 and a receiving portion 52 having a receiving groove 51 with which a part 50a of the lock lever 50 can be engaged. Lock lever 50 is shaft 53
It is freely rotatable around. As shown in FIG. 9, five receiving grooves 51 are formed in the housing 14 at positions corresponding to the five positions. Ribs 57 are formed between the receiving grooves 51.

When the lock lever 50 is engaged with any one of the receiving grooves 51, the rotation of the grip 3 is prevented by the rib 57, and the lock lever 50 is moved in the direction of arrow A (release direction) in FIG. When the lock lever 50 is disengaged from the receiving groove 51 when operated, the grip 3 can be rotated. The lock lever 50 is urged by a torsion spring 58 in a direction to engage with the receiving groove 51.

A mark 60 (shown in FIG. 10) is provided on the grip 3. The housing 14 is provided with a position indicator (not shown) at a position corresponding to each position of the grip 3 so that the user can visually check where the grip 3 is located among the above five positions. ing.

The detent mechanism 41 includes two balls 71 and 72 functioning as engaging members, and a detent body 74 which rotates integrally with the first gear 15.
The balls 71, 72 are housed in ball housing holes 76, 77 formed in the housing 14, and are urged by springs 78, 79 in a direction to come out of the ball housing holes 76, 77.

A center hole 80 through which the handlebar 2 passes is formed in the center of the detent body 74.
Four receiving holes 81, 82, 83, 84 are formed on the same circumference centered on the center hole 80. In the case of this embodiment, all the receiving holes 81 to 84 are arranged at the same pitch P2 (45 °) between the holes. Ball 7
The pitch P1 of 1,72 is 1.5 times the pitch P2 between holes (6
7.5 °).

When the grip 3 is in the neutral position (NEUTRAL), the first ball 71 is fitted in the second receiving hole 82. In this state, the lock lever 50 is moved by the arrow A in FIG.
When the grip 3 is rotated to the position (UP1) in FIG. 10, the second ball 72 of the detent mechanism 41 is fitted into the third receiving hole 83, and at that moment, the rotation resistance of the grip 3 is changed. Increase and the sense of articulation arises,
It can be seen that the position has been switched to UP1 by the feel received by the hand. Further, the grip 3 is connected to (UP in FIG. 10).
When the ball is rotated to the position 2), the first ball 71
Into the receiving hole 81. Also at this time, it is understood that the mode has been switched to UP2 because of a sense of articulation.

Conversely, when the grip 3 is rotated to the position indicated by (DOWN1) in FIG. 10, the second ball 72 fits into the fourth receiving hole 84. At this time, since a sense of articulation is generated, it is understood that the mode has been switched to DOWN1. When the grip 3 is further rotated to the position of (DOWN2), the first ball 71 is moved to the third receiving hole 83 this time.
Fits. Also at this time, a sense of moderation occurs, so DOWN2
It can be seen that it has been switched to.

Next, the operation of the actuator unit 8 and the control unit 9 will be described with reference to a flowchart shown in FIG. 11 (normal operation).
And the flowchart shown in FIG. 12 (engine misfire control)
A description will be given with reference to FIG.

In this embodiment, the absolute position of the output shaft 27 is calculated based on the relative movement amount of the output shaft 27 of the actuator section 8 from the reference position. There is. When power is supplied to the control unit 9, a drive signal is output so that the output shaft 27 moves to the reference position, and the output shaft 27 moves to the reference position. When the detected member 34 fixed to the output shaft 27 reaches the first sensor 33 for detecting the reference position, the first sensor 33 is turned on, and the signal is input to the control unit 9. Then, a signal for stopping the motor 20 is output from the control unit 9, and the output shaft 27 stops at the reference position by stopping the motor 20. At this time, the integrated position of the actuator is cleared to zero on the program of the central control unit 9b.

FIG. 11 is a flow chart showing a normal operation. As described above, the rotational position of the grip 3 is classified into five positions on the program, and the target position of the actuator unit 8 (the target position of the output shaft 27) corresponding to each position is determined in advance. Here, the target value is assumed to be Xg, and the actual values that can be taken are X1 to X5.
And X1 is a reference position (= 0), X1 <X2 <X
3 <X4 <X5. The current integrated position of the actuator is defined as Xa.

In normal operation, comparison control is repeatedly performed so that the grip position and the integrated position of the actuator always coincide with each other on a program. Therefore, the following operation is performed. (1) When Xg = Xa, the motor 20 does not operate because the grip position and the actuator position are equal. (2) When Xg> Xa, the control unit 9 outputs a signal for driving the motor 20 so that the grip position becomes large and the output shaft 27 moves in the direction opposite to the reference position. The motor 20 moves the output shaft 27 in a direction to extend the bellows 30. At this time, the pulse captured by the second sensor 35 is taken into the control unit 9 with the movement of the output shaft 27, and Xa is added according to the number of pulses. As a result of the addition, Xg =
When it becomes Xa, a signal for stopping the motor 20 is output from the control unit 9 and the motor 20 stops. (3) When Xg <Xa, the grip position becomes small, and the control unit 9 outputs a signal for driving the motor 20 so that the output shaft 27 of the actuator unit 8 moves in the direction of the reference position. The motor 20 moves the output shaft 27 in a direction to contract the bellows 30. At this time, a pulse is fetched from the second sensor 35 into the control unit 9 along with the movement of the output shaft 27,
Xa is subtracted according to the number of pulses. The result of the subtraction,
When Xg = Xa, a signal for stopping the motor 20 is output from the control unit 9, and the motor 20 stops.

Xa = X immediately after the initial reference position adjustment.
Since 1 = 0, the grip position is X1
If it is, the motor 20 is stopped as it is, and otherwise, the same operation as the above (2) is performed.

The flowchart of FIG. 12 shows the engine misfire control when the actuator section 8 is operating. As described above, the reaction force due to the water ejection from the nozzle 4 acts on the actuator section 8 via the push-pull cable 10, so that a large load is imposed on the operation of the motor 20. Therefore, in this embodiment, the nozzle misfire output during the operation of the actuator is reduced by performing engine misfire control as described below.

In the normal operation described above, when the motor 20 of the actuator section 8 is operating, that is, while the drive signal is being output to the motor 20, the following operation is repeatedly performed. Let N be the target engine speed. The actual number of revolutions of the engine is read, and when it is N or more, an arbitrary duty pulse is output from the control unit 9 to the misfire circuit on the engine side. This duty pulse is set to a value such that the misfire function operates properly without stopping the engine. At this time, the engine speed decreases irrespective of the hull-side throttle opening, but when the engine speed falls below the target speed N, the control is repeated so that the misfire output is turned off. To be stable.

In the case of this embodiment, the target rotation speed N of the misfire function is substantially set to the idling rotation speed. When the misfire function is activated, the ejection of water from the nozzle 4 is temporarily weakened. Thus, the nozzle reaction force, which is a load on the motor 20, is reduced, and the motor 20 can be operated efficiently. Immediately after the operation of the motor 20 is completed, the misfire control is also terminated, so that the operability of the jet propulsion nozzle 4 is not substantially affected.

[0044]

According to the first aspect of the present invention, the actuator section is made compact by adopting a direct-acting motor for directly converting the rotation of the rotor into the axial movement of the output shaft. be able to. According to the second aspect of the present invention, since the first sensor and the second sensor are built in the actuator section, the actuator section can be made more compact.
According to the third aspect of the present invention, it is possible to provide an electric nozzle driving device having a built-in grip position sensor in a grip portion without impairing a grip operation feeling of a mechanical nozzle driving device conventionally used.

According to the fourth aspect of the present invention, the output of the jet propulsion nozzle can be reduced when the actuator is operated. Therefore, by reducing the nozzle reaction force, a motor having a relatively small output is used for the actuator section. As a result, it is possible to provide an inexpensive and compact electric nozzle driving device as compared with the conventional device.

[Brief description of the drawings]

FIG. 1 is a side view of a watercraft nozzle drive device showing an embodiment of the present invention.

FIG. 2 is a front view of a grip portion of the nozzle driving device shown in FIG.

FIG. 3 is a cross-sectional view of the grip section along the line III-III in FIG. 2;

FIG. 4 is a cross-sectional view of the grip section taken along line IV-IV in FIG. 2;

FIG. 5 is a sectional view of an actuator section of the nozzle driving device shown in FIG. 1;

FIG. 6 is a sectional view showing an operation mode of the actuator unit shown in FIG. 5;

FIG. 7 is a block diagram of a control unit of the nozzle driving device shown in FIG. 1;

FIG. 8 is a sectional view showing a lock mechanism and a detent mechanism of a grip portion of the nozzle driving device shown in FIG. 1;

9 is a front view of a part of the lock mechanism shown in FIG.

FIG. 10 is a front view showing an operation mode of the detent mechanism shown in FIG. 8;

FIG. 11 is a flowchart showing functions of a control unit of the nozzle driving device shown in FIG.

12 is a flowchart showing a misfire control function of a control unit of the nozzle driving device shown in FIG.

FIG. 13 is a perspective view showing an example of a watercraft.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Water motorcycle 2 ... Handlebar 3 ... Grip 4 ... Nozzle 6 ... Nozzle drive device 7 ... Grip part 8 ... Actuator part 9 ... Control part 10 ... Push-pull cable (force transmission member) 17 ... Grip position sensor 20 ... Motor 27 ... output shaft 33 ... first sensor (reference position detecting means) 35 ... second sensor (motor movement amount detecting means) 40 ... lock mechanism

Claims (4)

[Claims] 1. A nozzle driving device for use in a small boat having a jet propulsion nozzle swingable at an up side and a down side at a rear part of a hull, a mechanism for operating the jet propulsion nozzle up or down. A force transmission member connected to the steering wheel, a grip portion having a grip rotatably provided on a steering handlebar, and a second rotation when the grip is rotated in a first direction with a neutral position as a boundary. A grip position sensor that generates a different electric signal when rotated in the direction, an actuator unit including a motor that drives the force transmitting member, and a nozzle that is raised based on the electric signal from the grip position sensor. And a control unit for controlling the rotation of the motor so as to move the motor to the side or the down side. A direct-rotation motor having a rotor that rotates when magnetized, and a screw portion that converts the rotational force of the rotor into axial movement and an output shaft that connects the force transmitting member. Nozzle drive device for small boats. 2. The motor of the actuator section includes a first sensor for detecting a reference position of the output shaft, and a second sensor for detecting rotation of the rotor. 2. The motor according to claim 1, wherein the rotation of the motor is controlled so that the nozzle is at a desired trim angle position based on the outputs of the first sensor, the second sensor, and the grip position sensor. The nozzle driving device as described in the above. 3. The nozzle driving device according to claim 1, wherein the grip portion includes a lock mechanism for stopping the grip at a position corresponding to a trim angle and the grip position sensor. 4. A nozzle driving device for use in a small boat having a jet propulsion nozzle swingable at an up side and a down side at a rear part of a hull, a mechanism for operating the jet propulsion nozzle up or down. A force transmission member connected to the steering wheel, a grip portion having a grip rotatably provided on a steering handlebar, and a second rotation when the grip is rotated in a first direction with a neutral position as a boundary. A grip position sensor that generates a different electric signal when rotated in the direction, an actuator unit including a motor that drives the force transmitting member, and a nozzle that is raised based on the electric signal from the grip position sensor. A control unit that controls the rotation of the motor so as to move the motor to the side or the down side, wherein the control unit controls the engine while the motor is operating. A small boat nozzle drive device having an engine misfire control function of forcibly causing a misfire to reduce the reaction force of the nozzle.