JPH0356072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a water discharge pressure control device for a fire engine.

BACKGROUND TECHNOLOGY In general, a water spray system for a fire engine has a configuration in which a water pump driven by an internal combustion engine pressurizes water taken in from a water suction hose, and the pressurized water is discharged from a water discharge nozzle. It is becoming. In conventional devices of this type, in order to maintain the water discharge pressure at the water discharge nozzle at a desired set value, a control system is configured that controls the speed of the internal combustion engine in response to a signal indicating the water discharge pressure. A water discharge pressure control device is provided to maintain the pressure at a desired set value (see, for example, Japanese Utility Model Application Publication No. 51-23394).

The conventional water discharge pressure control device described above increases the engine speed when the water discharge pressure is less than the desired set value, while decreasing the engine speed when the water discharge pressure is greater than the desired set value. The water discharge pressure is adjusted so that the water discharge pressure reaches a desired set value.

Problems to be Solved by the Invention Therefore, in the conventional device described above, when the water suction flow rate decreases due to reasons such as the water suction hose being stepped on by a car, the water pressure on the water suction side becomes a large negative pressure, and the water discharge pressure decreases. Since the pressure is lower than the set pressure, the engine speed will increase to near the maximum rotation speed in order to increase the water discharge pressure. Under these conditions, when the water suction hose is released from being trampled, the water suction flow rate immediately returns to the original water suction flow rate, and the water discharge pressure temporarily rises to exceed the required set pressure. However, there is a problem in that a large water pressure is suddenly applied to the nozzle, creating an extremely dangerous situation for workers.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a water discharge pressure control device for a fire engine that eliminates the above-mentioned problems in conventional devices and prevents sudden changes in water discharge pressure.

Means for Solving the Problems The present invention has a control means for controlling the rotational speed of the internal combustion engine so that the water discharge pressure given by the water pump driven by the internal combustion engine is maintained at a desired set pressure. A water discharge pressure control device for a fire engine, comprising: a detection means for detecting a negative pressure state on the water suction side of the water pump; and a detection means for adjusting the pressure on the water suction side to a predetermined negative pressure value in response to the detection result of the detection means. When the pressure becomes more negative than , the rotational speed of the internal combustion engine is forcibly reduced to a low rotational speed near the idle rotational speed, and when the pressure on the water intake side becomes higher than a predetermined negative pressure value. The present invention is characterized in that it comprises means for controlling the control means to resume rotational speed control of the internal combustion engine.

Effects According to the above configuration, when the water suction side hose is stepped on and crushed by a car, for example, and the water discharge pressure decreases due to the drop in flow rate, the control means controls the rotation of the internal combustion engine in order to increase the water discharge pressure. Speed is increased. However, when the negative pressure on the water intake side becomes more negative than a predetermined negative pressure value, the rotational speed of the internal combustion engine is forced to a predetermined low rotational speed, for example, near the idle rotational speed, and the internal combustion engine is overloaded. It is possible to prevent a load state from occurring. When the pressure on the water suction side becomes higher than the predetermined negative pressure value to the positive pressure side due to reasons such as the water suction hose being released, the rotational speed of the internal combustion engine is controlled again by the control means, and the required water discharge pressure is increased. The rotational speed of the internal combustion engine can be gradually increased to achieve this.

In this way, when the negative pressure on the water suction side becomes more negative than the predetermined negative pressure value, the rotational speed of the internal combustion engine is reduced to a low rotational speed, and the negative pressure on the water suction side becomes lower than the predetermined negative pressure value. When the value becomes more positive, the rotational speed of the internal combustion engine is increased again, and the rotational speed is adjusted so that the water discharge pressure becomes the required value.

As a result, for example, when the water suction hose is stepped on by a vehicle and the water suction side becomes in a large negative pressure state, the engine speed becomes a low rotational speed of about idling rotational speed, and it is possible to prevent a large load from being applied to the water pump. Then, when the cause such as trampling by a vehicle is removed and the water suction side pressure state returns to a predetermined normal state, the engine speed gradually increases from a low rotational speed, and the control means moves to adjust the water discharge pressure to the required level. It can be gradually increased to a pressure value. Therefore, if the trampling of the water suction hose, etc. is released,
It is possible to effectively prevent the water discharge pressure from rising rapidly at the nozzle, which greatly helps prevent danger to workers.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to illustrated examples.

FIG. 1 shows an embodiment of a water discharge device for a fire engine equipped with a water discharge pressure control device according to the present invention. The water discharging device 1 has a water pump 3 for fire fighting driven by a diesel engine 2, and the water pump 3 is connected to a water tank, such as a water tank for firefighting (not shown), through a water suction hose 4 provided on the water suction side of the water pump 3. After sucking water from a water tank and pressurizing it, the pressurized water is discharged through a water discharge hose 5 and a water discharge nozzle 6 provided on the water supply side of the water supply pump 3.

The diesel engine 2 is also used to drive a fire engine (not shown), and is configured to receive fuel from a fuel injection pump 7. The amount of fuel injection supplied from the fuel injection pump 7 to the diesel engine 2 is controlled by a positioning actuator 8.
It is adjusted according to the amount of operation of the control rack 9 operated by the operator.

The water pump 3 controls the rotational speed of the diesel engine 2 according to the water discharge pressure so that the water discharge pressure in the water discharge nozzle 6 is maintained at a desired set value.
A pressure detector 10 that outputs a detection signal V ₁ according to the water discharge pressure P ₁ provided on the water discharge side of the
A first control signal _S1 is provided in the control unit ₁₁ for outputting a first control signal S1 for adjusting the position of the control rack 9 in response to the water discharge pressure _P1 at a predetermined set pressure value _Pt in response to the water discharge pressure P1. A water discharge pressure control device 20 including a first control section 12 is configured.

The first control signal _S1 is applied to one fixed contact 16a of the switch 16, and when the switch 16 is switched as shown by the solid line, the first control signal _S1 is input to the speed governor unit 15. be done. The other fixed contact 16b of the switch 16 receives an accelerator signal S ₂ indicating the amount of operation of the accelerator pedal 17 for driving.
is supplied from the accelerator sensor 18, and when the diesel engine 2 is used for running, the switch 16 is switched as shown by the dotted line, and the accelerator signal _S2 is input to the speed governor unit 15.

In addition to the signal from the switch 16, the speed governor unit 15 receives a speed signal N indicating the speed of the diesel engine and a position signal R indicating the position of the control rack 9. In response to these input signals, A drive control signal DS is outputted to drive the actuator 8 so that the control rack 9 is positioned so that the diesel engine 2 reaches a desired rotational speed.

Therefore, when the switch 16 is switched as shown by the dotted line, the diesel engine 2
Its speed is controlled according to the amount of operation of the accelerator pedal 17. On the other hand, when the switch 16 is switched as shown by the solid line, the speed of the diesel engine 2 is controlled by the first control signal _S1 so that the water discharge pressure _P1 matches the set pressure value _Pt . That is, the water discharge pressure control device 20 controls the water discharge pressure.
When P ₁ becomes smaller than the set pressure value P _t , the actuator 8 moves the control rack 9 in the fuel increasing direction, and on the other hand, when the water discharge pressure P ₁ becomes larger than the set pressure value P _t , the actuator 8 moves the control rack 9 . This configuration outputs a first control signal _S1 for operating the speed governor unit 15 so as to move the fuel in the fuel decreasing direction.

If the pressure _P2 on the water suction side of the water pump 3 becomes an extremely large negative pressure due to a vehicle passing over the water suction hose 4, etc., the rotation speed of the diesel engine 2 may be reduced to a low rotation speed of about idling speed. In order to control the rotational speed of the diesel engine 2 again by the first control unit 12 when the pressure P ₂ on the water suction side returns to a predetermined negative pressure, the negative pressure detector 13 and the A second control section 14 is provided for controlling the operation of the first control section 12 in response to the operation of the negative pressure detector 13. Negative pressure detector 13
is connected to the water suction hose 4 in order to detect the negative pressure state on the water suction side of the water pump 3. In the illustrated embodiment, the pressure _P2 inside the water suction hose 4 is set to a predetermined negative pressure value P2. It is configured as a negative pressure switch which is closed when the pressure becomes more negative than _zero and is otherwise open. On the other hand, the second control section 14 is configured as a part of the control unit 11, and responds to the operation of the negative pressure detector 13 to
Control signal CS for controlling the operation of the control unit 12
It is configured to output .

A more specific embodiment of the control unit 11 is shown in FIG. The first control unit 12 has a differential amplifier 22 to which the detection signal V ₁ is applied to an inverting input terminal via an input resistor 21, and a non-inverting input terminal of the differential amplifier 22 has a power supply voltage +V is divided by the voltage dividing resistors 23 and 24.
_Vr is applied. The voltage dividing resistor 24 is configured as a variable resistor, and by adjusting it, the value of the reference voltage V _r can be arbitrarily determined, and the set pressure value P _t can be set to a desired value. The output terminal of the differential amplifier 22 is connected to the output terminal 26 of the first control section 12 via an output resistor 25 and to its non-inverting input terminal via a capacitor 27. A differential input signal corresponding to the difference between V ₁ and the reference voltage V _r is amplified and integrated, and is obtained as an output voltage V ₂ .
The output terminal 26 is grounded via a resistor 28, and the power supply voltage +V is supplied to the output terminal 26 via a resistor 29, so that the level of the output voltage _V2 from the output terminal 26 is The signal is narrowed within a predetermined level range and output as the first control signal _S1 .

In the illustrated embodiment, the input/output characteristics of the pressure detector 10 are set so that the level of the detection signal _V1 changes in proportion to the water discharge pressure _P1 , as shown in FIG. The level of the output voltage V ₂ has a characteristic that it decreases as the water discharge pressure P ₁ increases, and increases as the water discharge pressure P ₁ decreases. As a result, for example, when the water discharge pressure _P1 decreases below the required set pressure _Pt , the level of the first control signal _S1 increases, a larger drive current is supplied to the actuator 8, and the control rack 9 is activated in the fuel increasing direction. As a result, the rotational speed of the diesel engine 2 is increased, and the water discharge pressure _P1 is increased. vice versa,
When the water discharge pressure _P1 increases more than the required set pressure value _Pt , the rotational speed of the diesel engine 2 decreases, causing the water discharge pressure _P1 to decrease. In this way, the speed of the diesel engine 2 is feedback-controlled so that the value of the water discharge pressure _P1 is maintained at the required set pressure value _Pt .

Next, the second control section 14 will be explained. Second
The control unit 14 controls the switch 13a of the negative pressure detector 13.
It has a transistor 33 whose base is supplied with a power supply voltage +V through a resistor 31 and whose base is grounded through a resistor 32. The emitter of the transistor 33 is grounded, and the collector is connected to a resistor. A power supply voltage +V is supplied through the device 34. The negative pressure detector 13 detects the pressure inside the water suction hose 4 as shown in FIG.
It is configured to close only when the value of P ₂ becomes more negative pressure than a predetermined negative pressure value P ₀ ,
Therefore, when P ₂ ≧P ₀ , the transistor 33 is off, but when P ₂ <P ₀ , the switch 3a is closed, so the transistor 33 is turned on.

A voltage dividing circuit consisting of resistors 35 and 36 is connected in parallel with the collector-emitter circuit of the transistor 33, and the connection point between the resistors 35 and 36 is connected to the transistor 3 whose emitter is grounded.
7 bases are connected. transistor 37
The collector of the power supply voltage +
V is applied, and a charging/discharging circuit 40 including a capacitor 39 is connected.

The charging/discharging circuit 40 includes a resistor 41 and a series circuit of a resistor 42 and a diode 43 connected between the other end of a capacitor 39 whose one end is grounded and the collector of a transistor 37. . Therefore, when the transistor 37 is turned off, the resistors 38, 41, 42 and the diode 4
A charging current flows to the capacitor 39 through the capacitor 39.
On the other hand, when the transistor 37 is turned on, the diode 43 is reverse biased, so that the capacitor 39 is discharged only through the resistor 41. In this way, since the diode 43 is connected only to the resistor 42 with the polarity shown, the time constant when charging the capacitor 39 is small, while the time constant when discharging the capacitor 39 is large. Therefore, switch 1
3a turns on, transistor 33 turns on,
As a result, when the transistor 37 is turned off, the capacitor 39 is charged at a relatively high speed, and the terminal voltage V _c of the capacitor 39 rises sharply. On the other hand, when the switch 13a is turned off and the transistor 37 is turned on, the capacitor 39
is discharged relatively slowly through the resistor 41, so the value of the terminal voltage _Vc is the same as that of the transistor 37.
After turning on, it will slowly decrease over time.

The terminal voltage V _c is inputted via a resistor 44 to an attenuation circuit 51 including a differential amplifier 45 , and the output voltage V ₃ of the differential amplifier 45 is inputted via a resistor 46 to a buffer amplifier 47 . There is. The connection point between the input terminal of the buffer amplifier 47 and the resistor 46 is grounded by a resistor 48 and connected to the power supply voltage +V via a resistor 49.
Therefore, the level of the output voltage V ₃ is narrowed within a predetermined range and is input to the + input terminal of the buffer amplifier 47. As a result, an output voltage _V4 whose level changes according to the level of the _terminal voltage Vc is output from the output of the buffer amplifier 47, and this output voltage
V ₄ is applied to terminal 26 via diode 50.

As a result, the level of the first control signal S ₁ output from the terminal 26 is determined according to the higher level output signal of the two output signals V ₂ and V ₄ .

Next, while referring to FIG.
The operation of the device shown in the figure will be explained. As already explained, if there is no abnormality in the system, the engine speed is controlled by the first control signal _S1 so that the water discharge pressure is maintained at a predetermined set value.
In this case, the pressure _P2 inside the water suction hose 4 is closer to positive pressure than the predetermined negative pressure value _P0 ,
Therefore, since the switch 13a is open and the transistor 37 is on, the terminal voltage V _c
is almost zero. Therefore, the output voltage V ₄
Since the level of is also approximately the ground level, the diode 50 is in a reverse bias state, and the first control signal S changes in accordance with the output voltage _V2 , thereby controlling the water discharge pressure.

In the above state, if the pressure _P2 on the water suction side of the water pump 3 becomes more negative than the predetermined negative pressure value _P0 at time t= _t1 due to reasons such as the water suction hose 4 being stepped on by a vehicle, the switch is activated. 13a
is closed (FIG. 5a), the charging/discharging circuit 40 enters a charging state, and the level of the terminal voltage V _c begins to rise at a relatively fast rate (see FIG. 5b). Therefore, the output voltage V ₄ will also change in accordance with the change in the terminal voltage V _c (FIG. 5c).
On the other hand, in such a situation, the water discharge pressure is decreasing, and therefore, in order to further increase the rotation speed of the diesel engine 2, the level of the output voltage V ₂ is
After t=t ₁ , the voltage suddenly drops to near the ground level (Fig. 5d).

As a result, as soon as the switch 13a is closed, V ₄ >V ₂ and the level of the first control signal S ₁ becomes
After t= _t1 , the level corresponds to the level of the output voltage _V4 . That is, the level of the first control signal _S1 is t=
After t ₁ , it rises rapidly and resistors 25, 29, 28
(Fig. 5e). Therefore, the rotational speed N of the diesel engine 2 rapidly decreases to the idle rotational speed N _i after t= _t1 , as shown in FIG. 5f.
In this way, the pressure _P2 inside the water suction hose 4 is set to a predetermined value.
When the engine speed N becomes lower than P ₀ , the engine speed N becomes the idle rotation speed, so the water discharge pressure P ₁ rapidly decreases from the predetermined set value P _t , as shown in Figure 5g, and the diesel engine 2 has a large Load can be effectively prevented from being applied.

At time t= _t2, when the water suction hose 4 is released from being trampled and _P2 > _P0 , the switch 13a is turned off and the transistor 37 is turned on, so that the charging/discharging circuit 40 enters the discharge state, and the capacitor 39 is It is discharged via the resistor 41 with a relatively large time constant. Therefore, the level of the terminal voltage V _c gradually decreases, and along with this, the first control signal S ₁
Since the level of N also decreases gradually, the engine speed N
begins to rise gradually from the idle rotational speed, and the water discharge pressure _P1 also gradually rises (Fig. 5g).

As the water discharge pressure P ₁ increases, the level of the detection signal V ₁ also gradually increases, so the level of the output voltage V ₂ also begins to gradually increase (Fig. 5d), and at t=t ₃ , V ₄ <V ₂ Then, the level of the first control signal _S1 is determined according to the output signal _V2 .
That is, after _t3 , the water discharge pressure control by the first control section 12 is performed again according to the detection signal _V1 , and the water discharge pressure _P1 is maintained at the predetermined set water discharge pressure value _Pt .

In this way, due to the action of the second control unit 14, even if the negative pressure on the water suction side increases due to stepping on the water suction hose, etc., and then the water suction hose is suddenly released from being stepped on, the water discharge pressure is maintained at the required set pressure P _t Since the pressure increases gradually toward the water discharge nozzle, safety can be easily ensured without applying a large pressure shock to the water discharge nozzle.

Note that the configuration of the control section of the device according to the present invention is not limited to that shown in FIG. 2, and may be realized using a microcomputer, and a device configured in this manner is also within the scope of the present invention. It is included within the scope of.

Furthermore, the internal combustion engine for driving the water pump is not limited to a diesel engine, and the present invention can be applied to any internal combustion engine.
Similarly, the water discharge pressure can be controlled, and such a water discharge pressure control device also falls within the scope of the present invention.

Effects According to the present invention, as described above, when the pressure on the water suction side becomes more negative than a predetermined negative pressure value, such as when the water suction side hose is stepped on by a vehicle, the water supply pump is activated. The rotation speed of the internal combustion engine being driven is forcibly lowered, and when the water suction side pressure becomes more positive than the predetermined negative pressure value, the engine speed is controlled to obtain the required water discharge pressure again. Therefore, when the cause of the large negative pressure on the water suction side is removed, the engine speed increases from a low rotational speed and reaches the rotational speed necessary to obtain the required water discharge pressure. Therefore, when the cause of large negative pressure on the water suction side is removed, it is possible to effectively prevent the water discharge pressure from increasing rapidly and applying a large pressure shock to the water discharge nozzle.
It has an excellent effect in protecting the safety of workers.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a water discharge device equipped with a water discharge pressure control device according to the present invention, FIG. 2 is a circuit diagram showing an example of a specific circuit of the control unit shown in FIG. 1, and FIG. is a characteristic curve diagram showing the characteristics of the pressure detector shown in FIG. 1, FIG. 4 is a diagram showing the operating characteristics of the pressure detector shown in FIG. 1, and FIGS. FIG. 2 is a waveform diagram of signals of various parts for explaining the operation of the water spray device shown in FIGS. 1 and 2. FIG. 1... Water spray device, 2... Diesel engine, 3...
... Water pump, 4 ... Water suction hose, 10 ... Pressure detector, 11 ... Control unit, 12 ... First control section, 13 ... Negative pressure detector, 14 ... Second control section, P ₁ ... ... Water discharge pressure, P ₂ ... Pressure, CS ... Control signal, V ₁ ... Detection signal, S ... First control signal.

Claims (1)

[Claims] 1. A water discharge pressure control device for a fire engine, comprising a control means for controlling the rotational speed of the internal combustion engine so that the water discharge pressure provided by a water pump driven by the internal combustion engine is maintained at a desired set pressure, a detection means for detecting a negative pressure state on the water suction side of the water pump; and a detection means for detecting a negative pressure state on the water suction side of the water pump; The rotational speed of the internal combustion engine is forcibly reduced to a predetermined low rotational speed, and when the pressure on the water intake side becomes higher than the predetermined negative pressure value, the rotational speed control of the internal combustion engine by the control means is resumed. A water discharge pressure control device for a fire engine, comprising means for controlling the control means so as to control the control means.