JPH0328575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine rotation speed control device for safely operating an aerial work vehicle, that is, raising and lowering a boom, driving telescopic movement, and traveling.

(Prior Art) Conventionally, in order to control the engine speed of a vehicle for aerial work, a circuit was constructed that uses the battery B loaded on the vehicle for aerial work as a power source, as shown in the electric circuit in Figure 8. and accelerator control switch SW1
Manually operate the electromagnetic switch RU or RD to excite the electromagnetic switch RU or RD, supply the forward rotation drive power or reverse rotation drive power to the motor M that operates the accelerator lever, rotate it, and adjust the operating angle of the accelerator lever. to control the engine speed.
As mentioned above, the engine speed of the aerial work vehicle increases or decreases depending on the operating angle of the accelerator lever, so the driver operates the accelerator control switch SW1 according to the operating conditions of the aerial work vehicle, such as the boom and travel. and the engine speed was increased or decreased. At this time, the upper limit rotation speed of the engine is limited by the upper limit operating angle detector LS1, which detects when the accelerator lever has reached the upper limit operating angle, and the lower limit rotation speed of the engine, that is, the idle rotation speed, is limited when the accelerator lever reaches the lower limit. This was determined by the lower limit working angle detector LS2, which detects when the working angle has been reached.

(Problems to be Solved by the Invention) In the conventional engine speed control device, the driver judges the driving situation of the aerial work vehicle by himself.
Because the engine speed was adjusted manually, for example, if the boom's upright angle becomes higher than horizontal (the larger the boom's upright angle is, the vehicle's center of gravity moves upwards and the vehicle stability decreases). However, there is a problem in that when the driver increases the engine speed and raises or lowers the boom at a high speed, it is very dangerous for the driver. The same applies to the telescopic operation and traveling of the boom.

Therefore, in order to solve the above problems, the present invention sets the engine rotation speed to a preset safe medium speed so that the boom can be safely extended and extended when the boom is raised at a reference angle or higher. The technical problem to be solved is to control the rotation.

(Means for solving the problem) The first technical means for solving the above problem is to drive a motor according to the operation of the accelerator control switch, and to drive the motor according to the operation angle of the accelerator lever driven by the motor. The engine rotation speed control device for an aerial work vehicle is provided with an engine whose rotation speed is adjusted by the engine, a hydraulic pump is driven by the engine, and a boom is extended, contracted and raised by pressure oil from the hydraulic pump. a luffing angle detector that detects the luffing angle of the boom and outputs a signal corresponding to the luffing angle; an operating angle detector that detects the operating angle of the accelerator lever and outputs a signal corresponding to the detected angle; When the signal from the luffing angle detector corresponds to an angle equal to or greater than a preset reference angle, the operating angle is detected to be an operating angle corresponding to a medium rotation speed of the engine set for safe operation of the boom. and a control circuit that controls the motor so that the signals from the motors match.

A second technical means is to provide an engine that drives a motor in accordance with the operation of an accelerator control switch, and whose rotational speed is adjusted in accordance with the operating angle of an accelerator lever driven by the motor.
A hydraulic pump is driven by the engine, and an engine rotation speed control device of an aerial work vehicle equipped with a boom that extends, contracts, and raises and lowers with pressure oil from the hydraulic pump detects the lifting angle of the boom, and detects the lifting angle of the boom. A luffing angle detector outputs a signal corresponding to the boom, a boom extension detector detects the extension of the boom and outputs a signal corresponding to the extension, and a boom extension detector detects the operating angle of the accelerator lever and corresponds to the detected angle. an actuation angle detector that outputs a signal that corresponds to a preset reference angle; controlling the motor so that the signal from the operating angle detector matches an operating angle corresponding to a medium speed of the engine that is set in order to safely operate the boom when the boom is extended by more than the specified amount; The purpose of the present invention is to provide a configuration including a control circuit.

Furthermore, a third technical means is to provide an engine that drives a motor in accordance with the operation of an accelerator control switch, and whose rotational speed is adjusted in accordance with the operating angle of an accelerator lever driven by the motor,
A hydraulic pump is driven by the engine, and an engine rotation speed control device of an aerial work vehicle equipped with a boom that extends, contracts, and raises and lowers with pressure oil from the hydraulic pump detects the lifting angle of the boom, and detects the lifting angle of the boom. an operating angle detector that detects an operating angle of the accelerator lever and outputs a signal corresponding to the detected angle; and a workbench attached to the tip of the boom. When the signals from the foot switch and the luffing angle detector correspond to an angle equal to or higher than a preset reference angle, or when the foot switch is stepped on and a signal is output, in order to operate the boom safely, The motor is controlled so that the signal from the operating angle detector matches the operating angle corresponding to the set engine speed, and when the foot switch is released, the motor is controlled at the idle rotation of the engine. and a control circuit that controls the motor so that the signal from the operating angle detector matches the operating angle corresponding to the number of operating angles.

(Function) In the first invention, when the rising angle of the boom becomes equal to or higher than a preset reference angle during the boom hoisting operation of the aerial work vehicle, the circuit operates the motor that operates the accelerator lever of the engine according to the output signal of the hoisting angle detector. and operates the accelerator lever until the output signal of the operating angle detector matches the operating angle corresponding to the medium rotational speed of the engine, which is set for safe operation of the boom. In the second invention, in addition to the action of the first invention, when the boom is extended beyond a preset reference position, the circuit controls the motor that operates the accelerator lever of the engine according to the output signal of the boom extension/contraction detector. The accelerator lever is operated until the output signal of the operating angle detector matches the operating angle corresponding to the medium rotational speed of the engine, which is set for safe operation of the boom.

Furthermore, in the third invention, in addition to the effect of the first invention, when a footswitch provided on the workbench is operated, the circuit controls the motor in accordance with the output signal of the footswitch and detects the operating angle detector. When the accelerator lever is actuated until the output signal matches the operating angle corresponding to the medium speed rotation speed of the engine set for safe operation of the boom, and the operation of the foot switch is released, the operating angle detector is activated. It operates the accelerator lever until it outputs an operating angle signal corresponding to the idle rotation of the engine.

(Example) Next, the configuration of an embodiment of the present invention will be explained.

FIG. 1 shows the appearance of an aerial work vehicle 1. A swivel platform 3 on a chassis 2 is equipped with an engine 4 and a hydraulic system consisting of a hydraulic pump, hydraulic tank, etc. (not shown). A hoisting cylinder 6 for hoisting the boom 5 in response to the supply of hydraulic pressure is installed therein. The boom 5 is composed of a fixed boom 5A and a movable boom 5B, and a telescopic cylinder 7 for extending and contracting the movable boom 5B is installed inside the fixed boom 5A. A workbench 8 is provided at the tip of the movable boom 5B, and the operator operates the aerial work vehicle while operating switches in a control box 9 provided on the workbench 8. The control box 9 is provided with an automatic return type accelerator control switch SW1 that increases or decreases the rotational speed of the engine 4, and adjusts the operating speed of the boom 5, travel, etc. At the base end of the fixed boom 5A, the fixed boom 5A is erected by the erecting cylinder 6, and a contact point is closed until the erecting angle reaches a horizontal angle set as a reference angle, for example, and a contact point is closed when the erecting angle reaches a horizontal angle set as a reference angle. A luffing angle switch SW2 that opens is installed. In addition, at the tip of the fixed boom 5A,
A boom extension/contraction detection switch SW3 is installed, the contact of which closes when the movable boom 5B is housed in the fixed boom 5A, and which opens when the movable boom 5B is extended outside from the housed state.

FIG. 2 shows a configuration in which an accelerator lever 10 that adjusts the rotation speed of the engine 4 is operated by a motor M, and transmits forward and reverse rotational torque of the motor M to a reducer 12. The wire winding pulley 13 attached to the output shaft of the accelerator lever 10 is rotated to wind or unwind the wire 14 connected to the accelerator lever 10, thereby operating the accelerator lever 10. The speed reducer 12 has a structure such as a worm wheel that does not rotate due to a force from the load side, in this case a force from the accelerator lever 10 side, and maintains the tension of the room-temperature wire 14.

3 and 4 show a cam 15 mounted coaxially with the wire take-up pulley 13 so as to be interlocked with the rotation of the wire take-up pulley 13 shown in FIG.
When the cam 15 rotates, the recess 15A of the cam 15
A limit switch LS1 in which the open/closed state of the contact is reversed when it is located at the convex portion 15B and when it is located at the convex portion 15B.
It shows the engagement configuration with LS2 and LS3. The limit switch LS1 is installed at a position where the contact opens when the operating angle of the accelerator lever 10 is in the idle state of the engine 4,
Further, the limit switch LS2 is located at a position where the operating angle of the accelerator lever 10 corresponds to a medium speed rotation of the engine 4 that enables safe operation of the boom 5, that is, a position where the contact opens when the operating angle of the accelerator lever 10 is in a medium speed state. Installed and additionally a limit switch
The LS 3 is installed at a position where the contact opens when the operating angle of the accelerator lever 10 is at the highest speed rotation state of the engine 4.

Figure 5 shows battery B loaded on an aerial work vehicle.
As a power source, the accelerator control switch SW1, the luffing angle switch SW2, and the engine 4
Limit switch LS1 for idle setting of engine 4, limit switch for medium speed rotation setting of engine 4
Input the signal from limit switch LS3 for setting the maximum speed rotation of LS2 and engine 4, and
This is an electric circuit of the first embodiment that supplies a forward or reverse rotation drive power to rotate the engine and operate the accelerator lever.

The accelerator control switch SW1 is an automatic return type changeover switch, and one contact point L is
The limit switch LS1 and the electromagnetic switch RD described below
The other contact H is connected to the series circuit formed by the coil of the limit switch LS3.
is connected to the series circuit formed by the coil of electromagnetic switch RU, which will be described later, and electromagnetic switch RD and
The RU coil is connected to battery B's O volt. Luffing angle switch SW2 is electromagnetic relay RL
limit switch LS2 is connected in series with the coil of electromagnetic relay RM, and each series circuit is connected to battery B. When the excitation current is applied to the coil, the electromagnetic switch RD closes its main contact RDC, supplies power from the battery B to the motor M, and operates the accelerator lever 10 in the direction of decreasing the rotation speed of the engine 4. Rotate the motor M so that Further, when the excitation current is applied to the coil, the electromagnetic switch RU closes its main contact RUC to supply power from the battery B to the motor M, and the accelerator lever 10 is moved in a direction that increases the rotational speed of the engine 4. The motor M is rotated so as to operate as follows. On the other hand, the coil of the electromagnetic relay RL switches the levitation angle switch when the boom 5 is in an undulation state below horizontal.
Since the SW2 contact closes, it is energized. Further, the coil of the electromagnetic relay RM is energized when the motor M rotates to rotate the cam 15 and close the contact of the limit switch LS2. Normally closed contacts RLC and RMC of electromagnetic relay RL and electromagnetic relay RM are connected in series, one end of which is connected to battery B and the other end to limit switch LS1.

The operation will be explained according to the electric circuit configured as above. When the boom 5 of the aerial work vehicle 1 is below horizontal and the engine 4 is in an idle state, when the operator of the work platform 8 sets the accelerator control switch SW1 to the contact H side, the power supply current of the battery B is changed to the accelerator control switch SW1. Contact H
→ Limit switch LS3 → Flows through the coil of electromagnetic switch RU. In this case, since the boom 5 is below horizontal, the contacts of the luffing angle switch SW2 are closed, so the electromagnetic relay RL is energized, and the normally closed contact RLU is open, so the electromagnetic switch RD is not energized. As a result, the electromagnetic switch RU is energized, its main contact RUC is closed, and drive power is supplied from the battery B to the motor M in the forward rotation direction. The motor M rotates when supplied with driving power in the forward rotation direction, and is connected to the wire take-up pulley 13 via the reducer 12.
is rotated in the wire winding direction, and the accelerator lever 10 is operated in a direction to increase the rotational speed of the engine 4. As the motor M continues to rotate forward, the cam 15 also rotates together with the wire take-up pulley 13, and when the rotational position of the cam 15 reaches the position where the contact of the limit switch LS3 is opened, the electromagnetic switch RU
The excitation current is cut off. Therefore, the electromagnetic switch
The main contact RUG of RU opens and stops the rotation of motor M. In this state, the rotational speed of the engine 4 is maintained at the maximum rotational speed.

In this state, when the hoisting cylinder 6 is driven to raise the boom 5 above the horizontal level, the hoisting angle switch SW2 opens its contacts, so the electromagnetic relay RL is energized and opened, and its normally closed contact RLC is closed. Become. Also, limit switch LS2
is located in the recess 15A of the cam 15 like the limit switch LS3, and its contact is open, so the electromagnetic relay RM is energized and opened, and its normally closed contact
The RMU is in a closed state. Further, since the limit switch LS1 is located on the convex portion 15B of the cam 15, its contact point is closed. Therefore,
The power supply current of battery B is the contact of electromagnetic relay RL.
Flows through RLC → electromagnetic relay RM contact RMC → limit switch LS1 → electromagnetic switch RD coil.
As a result, the electromagnetic switch RD is energized, its main contact RDC is closed, and driving power is supplied from the battery B to the motor M in the reverse rotation direction. The motor M rotates when supplied with driving power in the reverse rotation direction, rotates the wire take-up pulley 13 in the wire rewinding direction via the reducer 12, and moves the accelerator lever 10 in the direction in which the rotation speed of the engine 4 decreases. Activate it. As the motor M rotates in the reverse direction, the cam 15 also rotates together with the wire take-up pulley 13, and when the rotational position of the cam 15 reaches the position where the contact of the limit switch LS2 is closed, the electromagnetic relay RM is energized and its normally closed contact RMC opens, so the excitation current of the electromagnetic switch RD is cut off. Therefore, the main contact RDC of the electromagnetic switch RD opens and stops the rotation of the motor M.
In this state, the engine 4 maintains a medium speed state.

Therefore, when the boom 5 reaches an upright angle above horizontal, the rotational speed of the engine 4 is automatically controlled from a high speed state to a medium speed state, and the boom 5 can be operated safely.

In addition, in order to put the engine 4 into the idle state, press the accelerator control switch SW1 at contact L.
Set it on the side. That is, by setting the accelerator control switch SW1 to the contact L side, the electromagnetic switch RD is energized, and by the same action as described above, reverse rotation driving power is supplied from the battery B to the motor M, and by the reverse rotation driving of the motor M. The accelerator lever 10 is operated in a direction to decrease the rotational speed of the engine 4. As the motor M rotates in the opposite direction, the cam 15 rotates in the opposite direction, and when the contact of the limit switch LS1 returns to the position where it opens, that is, the position where the engine 4 is in the idle state, the electromagnetic switch RD is de-energized and its main contact RDC is Open it to stop the rotation of the motor M. In this state, the engine 4 maintains an idle state.

Next, FIG. 6 shows an electric circuit of a second embodiment in which a series circuit formed by the boom extension/retraction detection switch SW3 and the coil of the electromagnetic relay RB is added to the electric circuit shown in FIG. 5.

The electric circuit shown in FIG. 6 includes the limit switch LS2 and the electromagnetic relay in the electric circuit shown in FIG.
The series circuit formed by the coil of boom extension/contraction detection switch SW3 and electromagnetic relay RB is connected in parallel to the series circuit formed by the coil of RM, and the normally closed contact RBC of electromagnetic relay RB is connected to the electromagnetic relay.
It is connected in series with the normally closed contact RMC of the RM to form a series circuit with the normally closed contact RLC of the electromagnetic relay RL. The other circuits are constructed in the same manner as in FIG. 5 above.

Next, the operation of the electric circuit of the second embodiment shown in FIG. 6 will be explained. The engine rotation speed control function during the up-and-down operation of the boom 5 is completely the same as in the first embodiment. In other words, if the undulating state of the boom 5 is below horizontal, the rotational speed of the engine 4 increases to the maximum rotational speed limited by the limit switch LS3;
When the undulating state of the boom 5 becomes more than horizontal, the rotation speed of the engine 4 is automatically controlled to a medium speed rotation set by the limit switch LS2.

In addition to this effect, the electric circuit of the second embodiment shown in FIG. boom 5
When the movable boom 5B is extended from the stored state to the outside, the boom extension/contraction detection switch SW3 opens its contact, and as a result, the excitation current supplied from the battery B to the coil of the electromagnetic relay RB is cut off, making it normally closed. When contact RBC closes, the power supply current of battery B flows from contact RLC of electromagnetic relay RL → electromagnetic relay
Contact RMC of RM → contact RBC of electromagnetic relay RB → limit switch LS1 → the coil of electromagnetic switch RD, so the electromagnetic switch RD is energized, its main contact RDC closes, and the battery B transfers from battery B to motor M in the reverse rotation direction. Drive current is supplied. The motor M rotates when supplied with driving power in the reverse rotation direction, rotates the wire take-up pulley 13 in the wire rewinding direction via the reducer 12, and moves the accelerator lever 10 in the direction in which the rotation speed of the engine 4 decreases. When the rotational position of the cam 15 rotating together with the wire take-up pulley 13 reaches a position where the contact of the limit switch LS2 is closed, the excitation current of the electromagnetic switch RD is cut off. Therefore, the main contact RDC of the electromagnetic switch RD opens and stops the rotation of the motor M. In this state, the engine 4 maintains a medium speed state.

Therefore, when the movable boom 5 is extended outward, the rotation speed of the engine 4 changes from a high speed state to a medium speed state,
The boom 5 can be operated safely.

Next, install a foot switch FS on the workbench 8,
Furthermore, the control box 9 is provided with a momentary type medium speed setting switch SW4, and a series circuit of the normally open contact FSO of the foot switch FS and the medium speed setting switch SW4 is added to the electric circuit shown in FIG. The electrical circuit is shown in FIG.

The electric circuit shown in FIG.
FS normally open contact FSO and the medium speed setting switch SW4
The contacts of the electromagnetic relay R, the coil of the electromagnetic relay R, and the normally closed contact RMC of the electromagnetic relay RM shown in FIG. Connect RO between contact H of accelerator control switch SW1 and positive terminal of battery B. Further, the normally closed contact FSC of the foot switch FS is connected in parallel to the series circuit formed by the normally closed contact RLC of the electromagnetic relay RL and the normally closed contact RMC of the electromagnetic relay RM shown in FIG. The other circuits are constructed in the same manner as in FIG. 5 above.

Next, the operation will be explained according to the electric circuit of the third embodiment shown in FIG. The engine rotation speed control function during the up-and-down operation of the boom 5 is the same as in the first embodiment. In other words, if the undulating state of the boom 5 is below horizontal, the rotation speed of the engine 4 will be lowered by the limit switch.
Although it increases to the maximum rotation speed limited by LS3,
When the lifting angle of the boom 5 becomes above horizontal, the rotation speed of the engine 4 is automatically controlled to a medium speed rotation set by the limit switch LS2.

In addition to this action, the electric circuit of the third embodiment shown in FIG.
When 4 is turned on, electromagnetic relay R is energized.
In other words, the electromagnetic relay RM is a limit switch.
Since the contact of LS2 is open and in a non-energized state, the electromagnetic relay R is energized by its normally closed contact RMC being closed. As a result, the normally open contact RO of the electromagnetic relay R closes and the power supply current of the battery B flows through the contact RO of the electromagnetic relay R → the limit switch LS3 → the coil of the electromagnetic switch RU, so the electromagnetic switch RU is energized, and its main contact RUC closes and battery B supplies motor M with drive power in the forward rotation direction. The motor M rotates when supplied with drive power in the forward rotation direction, rotates the wire winding pulley 13 in the wire winding direction via the reducer 12, and moves the accelerator lever 10 in the direction in which the rotational speed of the engine 4 increases. Activate it. When the motor M rotates forward and the cam 15 rotates together with the wire take-up pulley 13 to the position where the contact of the limit switch LS2 is closed, the electromagnetic relay RM is energized and its normally closed contact RMC is opened, so that the electromagnetic relay R is deenergized and its normally open contact RO opens. As a result, the excitation of the electromagnetic switch RU is also released, its contact RUC is opened, the supply of drive power to the motor M is stopped, and the rotation of the motor M is stopped. As long as the medium speed setting switch SW4 is turned ON and the foot switch FS continues to be depressed,
The operating position of the accelerator lever 10 is maintained at this position, and the engine 4 continues to rotate at a medium speed.

When the foot switch FS is released after the rotation of the engine 4 reaches a medium speed state, the normally closed contact FSC of the foot switch FS closes and the power supply current of the battery B is transferred to the normally closed contact of the foot switch FS.
FSC → Limit switch LS1 → Electromagnetic switch RD is excited because the flow flows through the coil of electromagnetic switch RD,
The main contact RDC closes and the battery B supplies the motor M with driving power in the reverse rotation direction. The motor M rotates when supplied with drive power in the reverse rotation direction, rotates the wire take-up pulley 13 in the wire rewind direction via the reducer 12, and rotates the accelerator lever 1.
0 in the direction of decreasing the rotational speed of the engine 4. When the motor M rotates in the opposite direction and the cam 15 rotates together with the wire take-up pulley to the position where the contact of the limit switch LS1 is opened,
The electromagnetic switch RD is de-energized and its main contact
RDC opens and the supply of drive power from battery B to motor M is stopped, and rotation of motor M is stopped. In this state, the accelerator lever 10
puts engine 4 into idle state. Therefore, when the foot switch FS is depressed and the medium speed setting switch SW
When both operations 4 are performed, the rotational speed of engine 4 is the highest at medium speed, and the driver presses the foot switch.
When the FS is released, the engine 4 is in an idle state, so the driver can safely drive the aerial work vehicle 1. In addition, if the foot switch FS is linked with a work controller, etc., it is possible to set the speed to medium only during work.

(Effects of the Invention) As described above, according to the present invention, when the boom raising angle is higher than the reference angle during boom hoisting operation of an aerial work vehicle, the engine speed is automatically set to a medium speed speed. By controlling the boom, it is possible to safely raise and lower the boom without interfering with work, and it also has the effect of improving fuel efficiency by preventing excess fuel consumption due to uneven driving during manual operation. In addition, during boom extension and retraction operation, when the boom is extended from the reference position, the engine speed is automatically controlled so as not to exceed the medium speed rotation speed, thereby enabling safe boom extension and retraction operation. Similarly, it has the effect of improving fuel efficiency. Furthermore, by incorporating the footswitch into the control circuit, the engine speed is automatically set to medium speed when the footswitch is operated, and the engine speed is set to idle when the footswitch is released. By controlling the above, it is possible to safely operate the vehicle for working at high altitudes, and as described above, there is an effect of improving fuel efficiency.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the external appearance of the aerial work vehicle and the mounting positions of each switch, Figs. 2, 3, and 4 are partial detailed views thereof, and Fig. 5 is an illustration of the first embodiment of the present invention. FIG. 6 shows an electric circuit diagram of a second embodiment of the present invention, FIG. 7 shows an electric circuit diagram of a third embodiment of the present invention, and FIG. 8 shows a conventional electric circuit diagram. 1... Aerial work vehicle, 4... Engine, 5... Boom, 8... Work platform, 9... Control box, 10... Accelerator lever, SW1... Accelerator control switch, SW2... Lifting angle switch, SW3……Boom extension/contraction detection switch,
SW4……Medium speed setting switch, LS1, LS2, LS
3...Limit switch, M...Motor, RU,
RD...Electromagnetic switch, R, RB, RL, RM...Electromagnetic relay, FS...Foot switch.

Claims (1)

[Claims] 1. An engine is provided which drives a motor in accordance with the operation of an accelerator control switch, and whose rotational speed is adjusted in accordance with the operating angle of an accelerator lever driven by the motor, and the engine drives a hydraulic pump. In an aerial work vehicle equipped with a boom that is driven, extended, contracted and raised by pressure oil from a hydraulic pump, a lifting angle detector detects a lifting angle of the boom and outputs a signal corresponding to the lifting angle. , an operating angle detector that detects the operating angle of the accelerator lever and outputs a signal corresponding to the detected angle; and when the signal from the undulation angle detector corresponds to an angle equal to or greater than a preset reference angle; and a control circuit that controls the motor so that a signal from the operating angle detector matches an operating angle corresponding to a medium speed engine speed set for safe operation of the boom. Car engine speed control device. 2. An engine is provided that drives a motor in accordance with the operation of an accelerator control switch, and the rotational speed is adjusted in accordance with the operating angle of an accelerator lever driven by the motor, and the engine drives a hydraulic pump. An aerial work vehicle equipped with a boom that expands, contracts, and raises and lowers using pressure oil from the ground includes a lifting angle detector that detects the lifting angle of the boom and outputs a signal corresponding to the lifting angle, and a lifting angle detector that detects the extension of the boom. a boom extension/contraction detector that outputs a signal corresponding to the extension; an operating angle detector that detects the operating angle of the accelerator lever and outputs a signal corresponding to the detected angle; Set to operate the boom safely when the signal corresponds to an angle equal to or greater than a preset reference angle, or when the signal from the boom extension/contraction detector corresponds to extension equal to or greater than a preset reference extension amount. and a control circuit for controlling the motor so that a signal from the operating angle detector matches an operating angle corresponding to a medium-speed engine rotation speed. 3 An engine is provided that drives a motor in accordance with the operation of an accelerator control switch, and the rotational speed is adjusted in accordance with the operating angle of an accelerator lever driven by the motor, and the engine drives a hydraulic pump. In an aerial work vehicle equipped with a boom that is extended, contracted and hoisted by pressure oil from a pump, a hoisting angle detector detects a hoisting angle of the boom and outputs a signal corresponding to the hoisting angle, and actuation of the accelerator lever. an operating angle detector that detects an angle and outputs a signal corresponding to the detected angle; a foot switch on a work platform attached to the tip of the boom; and a reference to which the signal from the luffing angle detector is set in advance. When the angle is greater than the above angle, or when the foot switch is depressed and a signal is output, the operating angle is adjusted to the operating angle corresponding to the medium speed of the engine set to ensure safe operation of the boom. The motor is controlled so that the signals from the detector match, and when the foot switch is released, the signal from the operating angle detector matches the operating angle corresponding to the idle rotation speed of the engine. and a control circuit for controlling the motor as described above.