JP3246520B2 - Prime mover controller for construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hydraulic excavator,
The present invention relates to a prime mover control device for a construction machine suitable for controlling the rotational speed of a prime mover mounted on a construction machine such as a hydraulic crane, and in particular, a selective command for selectively giving a target rotational speed of a prime mover in a plurality of stages. The present invention relates to a prime mover control device for a construction machine having means.

[0002]

2. Description of the Related Art FIGS. 5 to 10 show an example in which a conventional prime mover control device for a construction machine is used for a hydraulic excavator.

In the drawing, reference numeral 1 denotes a lower traveling body provided with a traveling hydraulic motor (not shown) and the like, and 2 denotes a lower traveling body 1
A revolving device 3 provided on the upper side indicates an upper revolving structure that is rotatably mounted on the lower traveling body 1 via the revolving device 2, and the upper revolving structure 3 includes a revolving frame 4 and the revolving frame. A machine room 5 provided on the frame 4 and accommodating an engine 9 and the like to be described later, an operation room 6 provided on the revolving frame 4 at a front side of the machine room 5, and a rear portion of the machine room 5 And a counter weight 7 provided on the revolving frame 4 and located on the side, and a command device 14 and the like described later are provided in the cab 6.

[0004] Reference numeral 8 denotes a working device provided at the front of the upper revolving unit 3. The working device 8 includes a boom 8 A rotatably provided at the front of the revolving frame 4, and a tip of the boom 8 A. Arm 8B rotatably provided on the side of the arm 8B;
B, a backhoe-type bucket 8C rotatably provided on the tip side of B, and these boom 8A, arm 8B, and bucket 8C are operated by boom cylinder 8D, arm cylinder 8E, and bucket cylinder 8F, respectively. Things.

[0005] In FIG. 6, reference numeral 9 denotes a diesel engine (hereinafter referred to as “engine”) as a prime mover provided in the machine room 5, reference numeral 10 denotes a governor attached to the engine 9, and , Governor lever 1
0A, an upper limit stopper 10B and a lower limit stopper 10C that regulate the rotation range of the governor lever 10A. The governor 10 is configured to increase or decrease the rotation speed of the engine 9 by rotating a governor lever 10A in a direction of acceleration A and a direction of deceleration B by a servo motor 11 described later.

Here, the governor 10 sets the rotation speed of the engine 9 to a maximum rotation speed of about 2000 rpm when the governor lever 10A comes into contact with the upper limit stopper 10B, and turns the rotation of the engine 9 when it comes into contact with the lower limit stopper 10C. The number is set to an idle speed of about 800 rpm.

Reference numeral 11 denotes a servomotor as an electric motor provided near the engine 9. A lever 11A is attached to an output shaft of the servomotor 11, and the lever 11A
Is the governor lever 10A of the governor 10 through the link 12.
It is connected to. The servo motor 11 rotates in the forward rotation F and reverse rotation R directions based on a control signal from a controller 18 described later, and rotates the governor lever 10A in the speed increasing A and deceleration B directions via the link 12. Along with
Even when the stop signal is input from the controller 18 and the rotation is stopped, the governor lever 10A is maintained at the current rotation angle and the engine 9 is rotated at the current rotation speed.

Reference numeral 13 denotes a potentiometer as a rotation angle detecting means. A lever 13A is attached to a rotation shaft of the potentiometer 13, and the lever 13A is
It is connected to. And the potentiometer 13
Is the governor lever 1 via the lever 13A and the link 12.
The rotation angle of 0A is detected as a voltage signal, and this voltage signal is output to the controller 18 as the rotation speed of the engine 9.

[0009] 14 represents a directive device provided in the cab 6, the finger-old device 14, the target rotational speed Na of the engine 9
Are P (power), E (economy), L (row), I
(Idle) selectively election varying in four steps modes
It comprises a mode selection switch 15 as an optional commanding means and an up-down switch 16 comprising an up switch 16A and a down switch 16B for increasing / decreasing the target rotation speed Na of the engine 9 in an addition / subtraction manner . So
Then, the mode selection switch 15 sets P, E, L, I
P switch 15A and E switch 1 corresponding to each mode
5B, L switch 15C, is constituted by the I switch 15D. Each of the switches 15A to 15D of the mode selection switch 15 and each of the switches 16A and 16B of the up / down switch 16 are constituted by a contacts (normally open contacts). As shown in FIG. 7, one end is grounded and the other end is grounded. is connected to a controller 18, a current limiting resistor 17, 17, ... each voltage through is applied.

The command device 14 is operated by the operator to select each of the switches 15A to 15A of the mode selection switch 15.
When D is selectively operated, each of the switches 15A to 15A
D outputs an on / off signal to the controller 18 to instruct the target rotation speed Na of the engine 9 in four stages. When the up / down switch 16 is operated, an on / off signal is output from each of the switches 16A and 16B, and the target rotation speed Na of the engine 1 is increased or decreased in accordance with the pressing time of each of the switches 16A and 16B. It has become.

Reference numeral 18 denotes a controller provided in the driver's cab 6 or the like. As shown in FIG. 8, the controller 18 includes a mode selection switch input unit 19, an up / down switch input unit 21, an arithmetic unit 25, and the like. It is configured as a computer.

Reference numeral 19 denotes a mode selection switch input section provided in the controller 18. The mode selection switch input section 19 has its input side connected to each of the switches 15A to 15D of the mode selection switch 15 and its output. The side is connected to a first% -N converter 23 described later via a signal connection point 20. When the switches 15A to 15D of the mode selection switch 15 are selectively operated and the on / off signal is output, the mode selection switch input unit 19 converts the% converted into a numerical value according to each of the P to I modes. Output the output.

That is, the mode selection switch input section 19
When the P switch 15A, the E switch 15B, the L switch 15C, and the I switch 15D of the mode selection switch 15 are turned on, for example, 100%, 80%, 40%,
It outputs a digitized signal of 0%.

Reference numeral 21 denotes an up / down switch input section provided in the controller 18. The up / down switch input section 21 has its input side connected to the switches 16A and 16B of the up / down switch 16, respectively.
Its output is connected to a signal connection point 20. When each of the switches 16A and 16B of the up / down switch 16 is selectively turned on, the up / down switch input unit 21 outputs 1% for each of the time periods during which the switches 16A and 16B are turned on. It outputs a digitized signal.

When the up switch 16A of the up / down switch 16 is turned on, the digitized signal of 1% output from the up / down switch input section 21 is supplied to the mode selection switch 20 via the signal connection point 20. It is added to the digitized signal from the input unit 19. On the other hand, when the down switch 16B is turned on, the digitized signal from the up / down switch input unit 21 is subtracted from the digitized signal from the mode selection switch input unit 19 via the signal connection point 20. I have.

Reference numeral 22 denotes a V provided in the controller 18.
The V-% converter 22 has an input side connected to the potentiometer 13 and an output side connected to a second% -N converter 24 described later. The V-% converter 22 converts a voltage signal corresponding to the rotation angle of the governor lever 10A input from the potentiometer 13 into a digitized signal of 0 to 100% as shown in FIG. Output.

Reference numeral 23 denotes a first% -N conversion unit provided between the signal connection point 20 and the calculation unit 25, and the first% -N conversion unit
As shown in FIG. 10, the N conversion unit 23 converts the digitized signal from the command device 14 input via the signal connection point 20 into an engine speed, and converts this signal into a target speed of the engine 9 as a command value. It is output to the arithmetic unit 25 as the number Na.

Reference numeral 24 denotes a second% -N conversion unit provided between the V-% conversion unit 22 and the operation unit 25.
The -N converter 24 converts the digitized signal input from the V-% converter 22 into an engine speed, as shown in FIG. 10, in substantially the same manner as the first% -N converter 23. The signal is output to the calculation unit 25 as the actual rotation speed Nb of the engine 9 as a detection value.

Reference numeral 25 denotes an arithmetic unit comprising a CPU or the like. The arithmetic unit 25 has a% -N conversion unit 2 on its input side.
3 and 24 are connected to each other, and an output unit for outputting a control signal to the servomotor 11 is connected to an output side thereof. The calculation unit 25 calculates the target rotation speed Na of the engine 9 output from the first% -N conversion unit 23 and the second rotation speed.
Is compared with the actual rotation speed Nb of the engine 9 output from the% -N conversion unit 24, and a control signal corresponding to the difference between the two is output to the servo motor 11 from the output unit 26. The governor lever 10A of the governor 10 is rotated via the
b is made to coincide with the target rotation speed Na.

The motor control device for a hydraulic shovel according to the prior art has the above-described configuration. The operator selects a mode selection switch 15 to change the rotation speed of the engine 9 according to the work content and the state of the work load. When any one of the P to I modes is selected, the mode selection switch input unit 19 outputs a digitized signal corresponding to the mode, and the digitized signal is output by the first% -N conversion unit 23. After being converted to the target rotation speed Na, it is output to the calculation unit 25.

The rotation angle of the governor lever 10A of the governor 10 is always detected by the potentiometer 13, and the voltage signal from the potentiometer 13 is V-%.
After being converted into the actual rotation speed Nb via the conversion unit 22 and the second% -N conversion unit 24, it is output to the calculation unit 25.

As a result, the arithmetic unit 25 calculates the first% -N
The target rotation speed Na from the conversion unit 23 is compared with the actual rotation speed Nb from the second% -N conversion unit 24, and a control signal corresponding to the difference between the two is output to the servo motor 11 via the output unit 26. Then, the servo motor 11 is rotated to rotate the governor lever 10A of the governor 10, and the rotation speed of the engine 9 is adjusted to the target rotation speed Na.

On the other hand, if the target engine speed Na of the engine 9 in the selected mode does not match the engine speed desired by the operator, the operator sets the up / down switch 1.
6, the up switch 16A and the down switch 16B are selectively turned on. Thus, the digitized signal from the up / down switch input unit 21 is added to or subtracted from the digitized signal from the mode selection switch input unit 19, and the target rotational speed N
a is changed.

[0024]

By the way, in the above-described prior art motor control device for a hydraulic shovel, the mode selection switch 15 is used to selectively instruct the target rotation speed Na from preset PI modes. Although it is possible, the setting of the target rotation speed Na by the mode selection switch 15 is fixed, and therefore may not match the engine rotation speed desired by the operator. In this case, the target rotation speed Na is set by the up / down switch 16. You have to tweak.

However, only during the time when the up switch 16A and the down switch 16B of the up / down switch 16 are turned on, a digitized signal of 1% is output from the up / down switch input section 21 and the mode selection switch input section 19 is output. When the difference between the engine rotation speed desired by the operator and the target rotation speed Na by the mode selection switch 15 is large, the operator is up. Down switch 16
It is necessary to turn on each switch 16A, 16B for a long time.

For this reason, according to the above-described prior art, when the work environment, work content, load state, etc. of the hydraulic shovel change frequently, the rotational speed of the engine 9 is made to coincide with the desired rotational speed. It takes time, and the target speed N
There is a problem that adjustment of a is complicated, and operability, work efficiency, and the like are significantly reduced.

On the other hand, in order to solve the above-mentioned problem, the operability of the up / down switch 16, that is, the scan speed of the up / down switch input section 21 is increased, and the digitized signal is reduced by 1%
Although a method of shortening the operation time required to change the value is conceivable, in this case, it is difficult to match the desired numerical value, and there is a problem that operability is reduced.

The present invention has been made in view of the above-described problems of the prior art, and can easily adjust the target rotation speed of the prime mover even when the working environment and the load state of the construction machine frequently change. The present invention relates to a prime mover control device for a construction machine capable of improving operability and the like.

[0029]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a prime mover provided in a construction machine, and a rotational speed of the prime mover attached to the prime mover according to a rotation angle of a governor lever. A governor that increases or decreases, an electric motor that rotates a governor lever of the governor based on a control signal, a rotation angle detection unit that detects the rotation speed of the prime mover as a rotation angle of the governor lever, and a target rotation speed of the prime mover. A motor control device for a construction machine, comprising: a rotation speed commanding means for instructing; and a controller for outputting a control signal to the electric motor based on a command value from the rotation speed commanding means and a detection value from the rotation angle detecting means. Applied to And claim 1
A feature of the configuration adopted by the invention of the present invention is that the rotation speed command means, the selection type command means for selectively instructing the target rotation speed of the prime mover as any one of a plurality of stages of command values, While continuously changing and instructing the target number of revolutions of the prime mover as a command value corresponding to the operation amount, the continuous command means for holding the command value, and any one of the continuous command means and the selective command means In order to output the command value of the target rotation speed from either of them, it is constituted by switching means for selectively switching between the continuous command means and the selective command means. According to the second aspect of the present invention, when the switching means is switched to the selection type command means, the rotation speed command means finely adjusts the target rotation speed command value output through the switching means to increase or decrease the command value. It has a configuration having value fine adjustment means. In the invention of claim 3 , the command value fine adjustment means is constituted by an up / down switch for increasing / decreasing the command value of the target rotation speed in accordance with a switch operation.

[0030]

According to the first aspect of the present invention, when performing mode selection or the like in accordance with the content of work or the state of a work load, the switching means is switched to the selection-type command means so that the prime mover can be used by using the selection-type command means. Can be selected as one of a plurality of stages of command values, and a command value of the selected target speed can be output. If the rotation speed of the prime mover does not match the desired rotation speed in this state, the switching means is switched from the selective commanding means to the continuous commanding means, and the continuous commanding means is operated. The target speed of the prime mover can be continuously changed according to the manipulated variable, and a command value (target speed) corresponding to the desired speed can be output. This command value can be output until the next operation by the continuous command means. Can be held. According to the second aspect of the present invention, the command value of the target rotation speed commanded by the selection commanding device can be delicately increased or decreased by the command value fine adjustment device to adjust the rotation speed of the prime mover to a desired rotation speed. . According to the third aspect of the present invention, when the up-down switch is operated, for example, the up-switch side, the command value of the target rotational speed can be slightly increased. The command value can be slightly reduced according to the switch operation.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the same reference numerals are given to the same components as those in the conventional art shown in FIGS. 5 to 10 described above, and the description thereof will be omitted.

In the figure, reference numeral 31 denotes a command device 1 described in the prior art.
Instead of 4 indicates directive device that apply to this embodiment, the finger-old device 31, much like the command device 14 described in the prior art, P switch 32A, E switch 32B, L switch 32C, I switch 32D selection type command means;
A mode selection switch 32 and, up switch 33
A and an up-down switch 33 composed of a down switch 33B. However, the command device 31 according to the present embodiment is connected to a changeover switch 35 described later.

Here, as shown in FIG. 2, the mode selection switch 32 has switches a and 32 each having an a contact.
B, 32C and 32D have resistors R1, R2, R3,
The other end is connected to a power line V to which a voltage is supplied from the controller 36.
One end of each of 2A to 32D is connected to a ground line G extending into the controller 36 via a voltage dividing resistor R5.

Each of the resistors R1, R2, R3, R4
Are set such that R4>R3>R2> R1 so that the P switch 32A and the E switch 32
When the B and L switches 32C and I switch 32D are turned on, different voltage signals of, for example, 5V, 4V, 3V, and 2.5V are generated, respectively.

Further, each of the switches 33A and 33B of the up / down switch 33 is connected to a controller 36 via a changeover switch 35 in substantially the same manner as the up / down switch 16 described in the related art.
6, a voltage is applied via a current limiting resistor 17.

[0036] 34 indicates a fuel lever as continuous instruction means connected to the change-over switch 35, the fuel lever 3
4 corresponds to the operation amount by performing the lever operation.
Command value (target engine speed Na of engine 9)
And keep this command value until the next lever operation
It is. As shown in FIG. 2 , the fuel lever 34 is configured as a variable resistor including a resistor 34A and a slider 34B slidably provided on the resistor 34A. Also,
The fuel lever 34 is operated by a changeover switch 35 so that the resistance 3
4A is connected to the ground line G, the other end of the resistor 34A is connected to the power supply line V, and the slider 34B is connected to the signal line S.
Is to be connected to.

The maximum value of the output voltage of the fuel lever 34 is determined by the P switch 3 of the mode selection switch 32.
The output voltage (5V) when 2A is turned on,
The minimum value of the output voltage is configured to match the output voltage (2.5 V) when the I switch 32D of the mode selection switch 32 is turned on.

The fuel lever 34 is connected to the slider 3
By moving 4B leftward and rightward in FIG. 2, the output voltage to the signal line S is variably reduced and increased, and the target rotation speed Na of the engine 9 is continuously commanded.

35 is a command device 31 and a fuel lever 34
2 shows a changeover switch as a changeover means provided in the operator's cab 6 between the controller 36 and the controller 36. The changeover switch 35 includes a signal line S, a power supply line V,
Three c-contacts 35A, 35 connected to the mode selection switch 32 and the fuel lever 34 corresponding to the ground line G
A,... And each switch 33 of the up-down switch 33
A, 33B, two b-contacts 35B, 35B connected to
And an operation unit 35C for switching the contacts 35A and 35B in conjunction with each other. The changeover switch 35 always connects the command device 31 and the controller 36 via the contacts 35A and 35B.

When the operator switches the operation unit 35C, the changeover switch 35 is turned on.
5A, the mode selection switch 32 and the fuel lever 3
4 is selectively switched, and each b contact 35B is opened and closed to cut off and communicate between the up / down switch 33 and the controller 36.

Reference numeral 36 denotes a controller applied to this embodiment. The controller 36 is substantially the same as the controller 18 described in the prior art, and as shown in FIG. Part 22, 1st%
-N conversion unit 23, second% -N conversion unit 24, operation unit 2
5. The output unit 26 and the like are configured as a microcomputer. However, the controller 36 according to the present embodiment
The mode selection switch input unit 19 described in the prior art
9 in that another V-% converter 37 for converting a voltage signal into a digitized signal is provided as shown in FIG.

Then, the controller 36 converts the voltage signal input via one of the command device 31 and the fuel lever 34 via another V-% converter 37 and the first% -N converter 23. The target rotation speed Na is converted to a target rotation speed Na, and the target rotation speed Na is compared with the actual rotation speed Nb of the engine 9 output from the second% -N converter 24, and a control signal corresponding to a deviation between the two is calculated. The output from the output unit 26 to the servomotor 11 allows the governor 10 to be output via the servomotor 11.
The governor lever 10A is rotated to make the actual rotational speed Nb of the engine 9 coincide with the target rotational speed Na.

The prime mover control device for a hydraulic shovel according to the present embodiment has the above-described configuration, and its basic operation is not particularly different from that of the prior art.

In the present embodiment, however, resistors R1 to R4 are provided in the switches 32A to 32D of the mode selection switch 32 so that the switches 32A to 32D output different values of output voltages to the signal line S, respectively. Device 3
Since the changeover switch 35 for selectively switching between the mode selector switch 1 and the fuel lever 34 is provided in the cab 6, the mode selection switch 32 and the fuel lever 34 are switched by operating the operation section 35 </ b> C of the changeover switch 35. It can be selectively switched.

As a result, for example, when the work content and the working environment of the hydraulic shovel hardly change and the number of changes of the engine speed is small, the target speed Na of the engine 9 is set to P, E by the mode selection switch 32. , L, and I modes can be selected and finely adjusted by the up / down switch 33.

When the work contents of the hydraulic shovel change frequently and the number of changes in the engine speed is large, the operating section 35C of the changeover switch 35 is operated to switch the respective contacts 35A and 35B to switch the mode. By switching the connection from the selection switch 32 to the fuel lever 34, a target rotation speed Na corresponding to the operation amount of the fuel lever 34 can be output as a command value, and the target rotation speed Na of the engine 9 can be continuously changed. it can. Then, the operator operates the fuel lever 34 until the engine speed matches the desired speed.
The by operation, also quickly cope with frequent changes such work and load conditions, changes in the target rotational speed Na, together with the adjusting operation can be easily performed, the next lever
The command value can be held up to .

Therefore, according to the present embodiment, the operator operates the change-over switch 35 to perform a step-by-step, fixed (digital) operation by the mode selection switch 32 according to the change frequency of the engine speed and the like. Either one of the setting of the target rotation speed Na and the setting of the continuous (analog) target rotation speed Na by the fuel lever 34 can be arbitrarily selected, and the operability and work efficiency are greatly improved. be able to.

In the above-described embodiment, the changeover switch 35 is used as the changeover means.
Although it has been described that the command device 31 and the fuel lever 34 are switched by switching the 5C, the present invention is not limited to this.
One connector 41, 41 is provided on the fuel lever 34, another connector 42 is provided on the controller 36, and the other connector 42 is selectively connected to the one connector 41. It may be configured to switch between the lever 34.

Further, in the above embodiment, the feedback control is performed by using the servomotor 11 as the electric motor and the potentiometer 13 as the rotation angle detecting means. For example, a configuration may be adopted in which open-loop control is performed by using a stepping motor as an electric motor and using a counter that counts the number of drive pulses to the stepping motor as a rotation angle detection unit.

Further, in the above-described embodiment, a description has been given by taking a hydraulic excavator as an example of a construction machine, but the present invention is not limited to this, and can be widely applied to other construction machines such as a hydraulic crane.

[0051]

As described in detail above, according to the first aspect of the present invention, the rotation speed command means for commanding the target rotation speed of the prime mover can be selected-type command means, continuous-type command means, or any of these. Since the switching means is configured to output the command value of the target rotation speed from one side, for example, when the work content or the load state hardly changes, the switching means is switched to the selection-type command means side so that the target rotation speed of the prime mover is changed. The number of modes can be selected, and a command value of the target rotation speed corresponding to the operation mode or the like can be output. When the work content and the like frequently change, the switching means is switched from the selective commanding means to the continuous commanding means, so that the continuous commanding means is used until the engine speed reaches a desired speed. By operating it, it is possible to quickly respond to frequent changes in work content and the like, change the target rotation speed, easily perform adjustment work, and hold the command value until the next operation by the continuous command means. be able to. As a result, the operator can set either the stepwise setting of the target rotation speed by the selection-type command unit or the continuous setting of the target rotation speed by the continuous switching unit according to the work content of the construction machine by the switching unit. Either one can be selected arbitrarily, and operability and work efficiency can be improved. According to the second aspect of the present invention, the command value of the target rotation speed commanded by the selection-type command device is finely increased or decreased by the command value fine adjustment device, and the rotation speed of the prime mover is finely adjusted to a desired rotation speed. Can be. According to the third aspect of the present invention, the command value of the target rotation speed can be finely increased or decreased by using the up / down switch, and the rotation speed of the prime mover can be easily finely adjusted.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a motor control device for a hydraulic shovel according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing connection between a command device and a fuel lever in FIG. 1 and a controller.

FIG. 3 is a block diagram illustrating a configuration of a controller in FIG. 1;

FIG. 4 is an overall configuration diagram of a motor control device for a hydraulic shovel according to a modification of the present invention.

FIG. 5 is a front view showing a hydraulic excavator to which a conventional motor excavator motor control device is applied.

FIG. 6 is an overall configuration diagram of a motor control device for a hydraulic shovel according to the related art.

FIG. 7 is an electric circuit diagram showing a connection between a command device and a controller in FIG. 6;

FIG. 8 is a block diagram illustrating a configuration of a controller in FIG. 6;

FIG. 9 is an explanatory diagram illustrating conversion from a voltage signal to a digitized signal by a V-% conversion unit.

FIG. 10 is an explanatory diagram illustrating a state in which a digitized signal is converted into a rotation speed signal by a% -N conversion unit.

[Explanation of symbols]

 Reference Signs List 9 engine (motor) 10 governor 10A governor lever 11 servo motor (electric motor) 13 potentiometer (rotation angle detecting means) 31 command device (selective command means) 34 fuel lever (continuous command means) 35 changeover switch ( Switching means) 36 controller 41, 42 connector (switching means)

Claims (3)

(57) [Claims] A motor provided on a construction machine, a governor attached to the motor for increasing or decreasing the rotation speed of the motor in accordance with a rotation angle of the governor lever, and a governor lever of the governor being rotated based on a control signal. An electric motor that moves, rotation angle detection means for detecting the rotation speed of the prime mover as a rotation angle of a governor lever, rotation speed command means for commanding a target rotation speed of the prime mover, and a command value by the rotation speed command means. And a controller that outputs a control signal to the electric motor based on the detection value from the rotation angle detection means.The rotation speed command means includes a target rotation number of the motor. A selective commanding means for selectively instructing any one of a plurality of command values as a command value; and continuously changing a target rotation speed of the prime mover as a command value corresponding to an operation amount. Continuous command means for holding the command value, and outputting the command value of the target rotation speed from one of the continuous command means and the selective command means. A motor control device for a construction machine, comprising: command means and switching means for selectively switching between the selective command means. 2. The control device according to claim 1, wherein said rotation speed command means finely adjusts and increases / decreases a target rotation speed command value output through said switching means when said switching means is switched to a selection type command means side. The prime mover control device for a construction machine according to claim 1, wherein the control device has an adjusting unit. 3. The prime mover control device for a construction machine according to claim 2 , wherein said command value fine adjustment means comprises an up / down switch for increasing / decreasing a command value of said target rotation speed in accordance with a switch operation.