KR20050048653A - Prime mover controller of construction machine - Google Patents

Abstract

A prime mover controller in a construction machine comprising a hydraulic pump (11) being driven by a prime mover (40), a hydraulic motor (5) for traveling being driven by pressure oil delivered from the hydraulic pump (11), and a control valve (12) for controlling pressure oil flow from the hydraulic pump (11) to the hydraulic motor (5) depending on the operation of an operating member (22a). The prime mover controller further comprises means (31) for detecting the decelerating operation of the operating member (22a), means (35) for detecting the revolution speed Nm of the hydraulic motor (5), and means (30, 43) for controlling the revolution speed of the prime mover (40) depending on the detection results of the means (35) for detecting the revolution speed when a decelerating operation is detected by the means (31) for detecting the decelerating operation and controlling the revolution speed of the prime mover (40) depending on the operation of the operating member (22a) when an operation other than decelerating operation is detected.

Description

Mover control device for construction machinery {PRIME MOVER CONTROLLER OF CONSTRUCTION MACHINE}

 The present invention relates to a prime mover control device for a construction machine that performs slow down control of prime mover rotation speed.

 Conventionally, what is disclosed in Japanese Patent No. 2634330 is known as a control device of this kind.

In the apparatus described in this publication, the engine speed is gradually lowered over time without lowering the engine speed to the idle speed immediately when the foot is released from the travel pedal during travel. In other words, the engine speed is controlled to slow down, thereby preventing the occurrence of cavitation.

However, by slowing down the engine speed when the foot is released from the pedal, there is a fear that cavitation cannot be prevented reliably under a situation where cavitation is more likely to occur, such as when driving on a long downhill road. have.

1 is a view showing the appearance of a wheel-type hydraulic excavator to which the present invention is applied.

2 is a hydraulic circuit diagram for driving the wheel-type hydraulic excavator of FIG. 1.

3 is a hydraulic circuit diagram for the work of the wheel-type hydraulic shovel of FIG.

4 is a block diagram of a prime mover control device according to an embodiment of the present invention.

5 is a diagram illustrating details of a control circuit of FIG. 4.

FIG. 6 is a flowchart showing a control procedure of the delay control unit according to the first embodiment shown in FIG.

FIG. 7 is a flowchart showing a control procedure of the servo control unit shown in FIG. 4.

8 is a view for explaining the operation of the prime mover control device according to the first embodiment.

9 is a flowchart showing a control procedure of the delay control unit according to the second embodiment.

10 is a view for explaining the operation of the prime mover control device according to the second embodiment.

 An object of the present invention is to provide a prime mover control device for a construction machine that can reliably prevent the occurrence of cavitation even in the case of long downhill driving.

The present invention provides a hydraulic pump driven by a prime mover, a traveling hydraulic motor driven by pressure oil discharged from the hydraulic pump, and a control for controlling the flow of pressure oil from the hydraulic pump to the hydraulic motor in accordance with the operation of the operation member. Applies to construction machinery with valves. The prime mover control device includes deceleration detecting means for detecting the deceleration operation of the operation member, rotation speed detecting means for detecting the rotational speed of the hydraulic motor, and deceleration detection means for detecting the deceleration operation. And a prime mover rotation speed control means for controlling the rotation speed of the prime mover according to the detection result of the control unit and controlling the rotation speed of the prime mover in accordance with the operation of the operation member.

Accordingly, even in the case of long downhill driving, a sufficient makeup pressure can be secured, and a sufficient makeup flow rate can be supplied to prevent the occurrence of cavitation.

In this case, it is preferable to keep the rotational speed of the prime mover constant when the motor rotational speed is larger than a predetermined value, and gradually reduce the rotational speed of the prime mover when it is less than or equal to the predetermined value.

At the time of deceleration operation, the motor revolution speed is gradually reduced by a predetermined time or a predetermined amount. After that, if the motor revolution speed is larger than the predetermined value, the revolution speed of the prime mover is kept constant. You may.

It is preferable to apply this invention to a wheel type hydraulic excavator.

First Embodiment

A first embodiment in which the prime mover control device according to the present invention is applied to a wheel type hydraulic excavator will be described with reference to FIGS.

As shown in FIG. 1, the wheel-type hydraulic excavator has a traveling body 1 and a swinging body 2 rotatably mounted on the upper side of the traveling body 1. The swinging structure 2 is provided with the work front attachment 4 which consists of the cab 3, the boom 4a, the arm 4b, and the bucket 4c. The boom 4a is undulated by the drive of the boom cylinder 4d, the arm 4b is undulated by the drive of the arm cylinder 4e, and the bucket 4c is driven by the drive of the bucket cylinder 4f. By cloud or by dump. The traveling body 1 is provided with the traveling motor 5 by hydraulic drive, and the rotation of the traveling motor 5 is transmitted to the wheel 6 (tire) via a propeller shaft and an axle.

FIG. 2 is a hydraulic circuit diagram for driving the wheel type hydraulic excavator shown in FIG. 1. FIG. As shown in Fig. 2, the discharge oil from the variable displacement main pump 11 driven by the engine (motor) 40 is controlled by the control valve 12 in its direction and flow rate, and the counter balance valve ( It is supplied to the traveling motor 5 via the brake valve 14 incorporating 13). The amount of light in the main pump 11 is adjusted by the pump regulator 11a.

The pilot circuit 21 includes a pilot valve 21, a pilot valve 22 for generating a pilot secondary pressure according to the operation of the travel pedal 22a, and a return to the pilot valve 22 following the pilot valve 22. The slow return valve 23 which delays oil, and the forward and backward conversion valve 24 which are converted into forward (F position), backward (R position), and neutral (N position) by operation of the forward and backward conversion switch which are not shown in figure. It is provided. The pressure sensor 31 is connected between the slow return valve 23 and the forward and backward conversion valve 24, and the pressure sensor 31 detects the pressure Pt corresponding to the operation amount of the travel pedal 22a.

When the forward / backward switching valve 23 is switched to the F position or the R position by the switch operation, and the traveling pedal 22a is operated, the pilot pressure from the pilot pump 2l acts on the control valve 25. As a result, the control valve 12 is switched so that the hydraulic oil from the main pump 11 acts on the traveling motor 5 through the control valve 12, and the traveling motor 5 rotates at a speed corresponding to the pedal operation amount. The vehicle runs.

When the accelerator pedal 22a is removed while the vehicle is running, the pilot valve 22 shuts off the hydraulic oil from the pilot pump 21, and the outlet port communicates with the tank. As a result, the hydraulic oil acting on the pilot port of the control valve 12 returns to the tank via the forward and backward conversion valve 24, the slow return valve 23, and the pilot valve 22. At this time, since the return oil is throttled by the throttling of the slow return valve 23, the control valve 12 is gradually switched to the neutral position. When the control valve 12 is switched to the neutral position, the discharge oil from the main pump 11 returns to the tank, the supply of the driving pressure oil to the traveling motor 5 is interrupted, and the counter balance valve 13 is also shown. Converted to a neutral position.

In this case, the vehicle body continues to run by the inertia force, and the travel motor 5 changes from the motor action to the pump action. For example, in the forward travel, the B port side is sucked in the drawing and the A port side is discharged (reverse travel). In reverse). Since the oil pressure from the traveling motor 5 is throttled by the throttling (neutral throttling) of the counter balance valve 13, the pressure between the counter balance valve 13 and the traveling motor 5 rises, and the traveling motor It acts as a brake pressure on (5). As a result, the traveling motor 5 generates a brake torque to brake the vehicle body. If the suction flow rate is insufficient during the pumping operation, the traveling motor 5 is supplemented with the flow rate from the make-up port 15. The brake pressure is regulated at its maximum pressure by the relief valves 16 and 17.

When the running pedal 22a is released on the downhill, a hydraulic brake is generated in the same manner as in the deceleration described above, and the hill is descended by inertial driving while braking the vehicle. In this case, since the inertia of the vehicle body is larger than when the traveling pedal 22a is removed during flat driving, a sufficient amount of oil replenishment is required from the make-up port 15 to prevent cavitation. Therefore, in the present invention, as described later, the rotation of the engine 40 at the time of deceleration is controlled to prevent the lack of make-up pressure and the lack of make-up flow rate.

As an example of a working hydraulic circuit, the hydraulic circuit of a boom cylinder is shown in FIG. This hydraulic circuit controls the flow of the hydraulic oil from the main pump 26, the boom cylinder 4d which is expanded and contracted by the hydraulic oil from the main pump 26, and the boom cylinder 4d from the main pump 26. The control valve 27, the pilot pump 21, and the pilot valve 28 driven by the operation lever 28a are provided. Although not shown, other working actuator hydraulic circuits are also the same.

When the operation lever 28a is operated, the pilot valve 28 is driven according to the operation amount, and the pilot pressure from the pilot pump 21 acts on the control valve 27. As a result, the hydraulic oil from the main pump 26 is led to the boom cylinder 4d through the control valve 27, and the boom 4a is lifted by the expansion and contraction of the boom cylinder 4d. The main pump 26 may be omitted, and the cylinder 4d may be driven by the oil pressure from the main pump 24.

4 is a block diagram of a control circuit for controlling the rotation speed of the engine 40. The governor lever 41 of the engine 40 is connected to the pulse motor 43 via the link mechanism 42, and the engine speed is changed by the rotation of the pulse motor 43. In other words, the engine speed increases due to the electrostatic discharge of the pulse motor 43, and decreases in reverse. The potentiometer 44 is connected to the governor lever 41 via the link mechanism 42, and the potentiometer 44 detects the governor lever angle according to the rotation speed of the engine 40, and rotates the engine control. It is input to the control circuit 30 as the number Nθ.

The control circuit 30 includes a pressure sensor 31 that detects a pilot pressure Pt according to the amount of operation of the travel pedal 22a, a position switch that detects a switching position of the brake switch 32 and the forward and backward conversion valve 23. (33), a detector 34 for detecting the operation amount X of the rotational speed command member (for example, a fuel lever) (not shown), and a rotation speed sensor 35 for detecting the rotational speed of the traveling motor 5. Are connected to each other.

The brake switch 32 is converted into driving, working and parking positions to output work / driving signals. When the vehicle is switched to the driving position, the parking brake is released, and the brake pedal allows the operation of the service brake. When shifted to the working position, activate the parking brake and service brake. When the vehicle is switched to the parking position, the parking brake is activated. The brake switch 32 outputs an off signal when converted to the travel position, and outputs an on signal when converted to the work and parking position.

The rotation speed control circuit 30 performs the following calculation and outputs a control signal to the pulse motor 43.

5 is a conceptual diagram illustrating the details of the rotation speed control circuit 30. As shown in the figure, the relationship between the detected value Pt by the pressure sensor 3l and the target rotational speeds Nt, Nd is stored in advance in the rotational speed calculating sections 51 and 52, respectively. The target rotational speeds Nt and Nd are respectively calculated. In addition, the characteristic of the rotation speed calculating part 51 is a characteristic suitable for running, and the characteristic of the target rotation speed calculating part 52 is a characteristic suitable when the work is performed using the work attachment 4. According to these characteristics, the target rotation speeds Nt and Nd increase linearly from the idle rotation speed Ni as the pedal operation amount increases. The increase inclination of the target rotational speed Nt is greater than the increase inclination of the target rotational speed Nd, and the maximum value Ntmax of the target rotational speed Nt is larger than the maximum value Ndmax of the target rotational speed Nd.

As shown in the figure, the relationship between the detected value X by the detector 34 and the target rotational speed (set rotational speed) Nx is stored in advance in the rotational speed calculation unit 53. From this characteristic, the target rotation according to the operation amount X of the fuel lever is stored. Calculate the number Nx. The maximum value Nxmax of the target rotational speed Nx is set equal to the maximum value Ndmax of the rotational speed calculation unit 52.

The selection unit 54 selects any one of the target rotation speeds Nt and Nd of the rotation speed calculating sections 51 and 52 according to the signals from the brake switch 32, the position sensor 33 and the pressure sensor 31. In this case, the brake switch 32 is switched to the travel position (off signal output), the forward and backward conversion valve 23 is outside the neutral position, and the pilot pressure Pt by the operation of the travel pedal 22a is a predetermined value. When larger than (e.g., 0), that is, when driving, the target rotational speed Nt is selected, and in other conditions, that is, when the non-driving is selected, the target rotational speed Nd is selected. The maximum value selector 55 selects, as Nmax, the larger value of the target rotational speed Nt or Nd selected by the selection unit 54 and the target rotational speed Nx calculated by the rotational speed calculator 53.

The delay control section 56 rotates in the order shown in FIG. 6 in accordance with the selected rotation speed Nmax and signals from the brake switch 32, the position sensor 33, the pressure sensor 34, and the rotation speed sensor 35. Calculates the numerical command value Nin.

The servo control unit 47 compares the rotation speed command value Nin selected by the delay control unit 56 with the control rotation speed Nθ corresponding to the displacement amount of the governor lever 41 detected by the potentiometer 44. And the pulse motor 43 is controlled so that both may correspond according to the procedure shown in FIG.

The process of the delay control part 56 is demonstrated. In Fig. 6, first, at step S1, signals from the maximum value selecting section 55 and the respective sensors 31, 33, 35 and the switch 32 are read. Next, the value of a running flag is determined in step S2. The running flag is set to 1 at the time of traveling and to 0 at the time of non-driving by the process (step S10, step S11, step S12) mentioned later. If it is determined in step S2 that the running flag = 1 (during running), the flow advances to step S3 to determine the value of the deceleration flag. The deceleration flag is set to 1 at the deceleration time and is set to 0 at the deceleration time by the processes described later (step S4, step S5, step S13).

If it is determined that the deceleration flag = 0 (during non-deceleration), the flow advances to step S4 to determine whether or not the deceleration operation is started by the signal from the pressure sensor 31. In this case, for example, when the pedal amount of the traveling pedal 22a decreases and the pressure detection value Pt becomes less than or equal to the predetermined value Pt1, it is determined that the deceleration operation starts. If step S4 is affirmative, the process proceeds to step S5. In step S5, deceleration flag = 1 is set, and in step S13, deceleration flag = 0 is set.

In step S7, it is determined whether the motor rotation speed Nm detected by the rotation speed sensor 35 is less than or equal to a predetermined value Nm1 preset. This is a process for determining whether to allow the slow down of the engine speed, and the predetermined value Nm1 is set in consideration of the magnitude of the make-up pressure during traveling of the steel sheet. That is, the larger the fall of the make-up pressure due to the slowdown, the predetermined value Nm1 is set to a larger value. If step S7 is affirmed, it progresses to step S8 and the rotation speed command value Nin is gradually reduced by the predetermined ratio until it reaches the target rotation speed Nt according to the operation amount (pressure detection value Pt) of the travel pedal 22a. That is, the rotation speed command value Nin is slowed down. Then, the rate of decrease of the rotation speed command value Nin is changed over time. Alternatively, the reduction ratio of the rotation speed command value Nin may be changed in accordance with the magnitude of the rotation speed. If step S7 is negative, the process proceeds to step S9 and the previous value Ninb is substituted into the rotation speed command value Nin.

If it is determined in step S2 that the traveling flag is 0 (non-driving), the flow advances to step S10 to determine whether to start traveling. When the brake switch 32 is switched to the travel position (off signal output), and the forward and backward conversion valve 24 is outside the neutral position, and the pilot pressure Pt is larger than the predetermined value, it is determined to be the start of travel and the step S11 Proceeds to Step S12 otherwise. In step S11, the running flag = 1 is set, and in step S12, the running flag = 0 is set. Then, as mentioned above, deceleration flag = 0 is set in step S13, and it progresses to step S14. In step S14, the rotation speed Nmax selected by the maximum value selection part 55 is substituted into the rotation speed command value Nin.

On the other hand, if it is determined in step S3 that deceleration flag = 1 (during deceleration), the flow proceeds to step S6 to determine whether deceleration operation is canceled. In this case, for example, when the pressure detection value Pt becomes larger than the predetermined value Pt1 by the pedal operation of the travel pedal 22a, it is determined that the deceleration operation is cancelled. If step S6 is affirmative, it progresses to step S13, and if it is negative, it progresses to step S15. In step S15, it is determined whether the deceleration control after step S7 ends. This determination is performed by comparing the rotation speed command value Nin obtained by the previous process with the target rotation speed Nt (target rotation speed Nt in accordance with the pressure detection value Pt) commanded by the operation of the travel pedal 22a. When Nin? Nt, the deceleration control is determined to end, and the flow advances to step S16, otherwise, the flow advances to step S7. In other words, it is determined that the deceleration control ends when the rotation speed command value Nin becomes equal to the target rotation speed Nt commanded by the travel pedal 22a (a time when the operator becomes the rotation speed commanded). In step S16, it is determined in the same manner as in step S10 to determine whether the vehicle is running. If affirmative, the process proceeds to step S13, and if negative, the process proceeds to step S17. In step S17, running flag = 0 is set, and it progresses to step S13.

Next, the processing of the servo control unit will be described. In FIG. 7, first, the rotation speed command value Nin set by the delay control part 56 and the control rotation speed N (theta) detected by the potentiometer 44 are respectively read out in step S21. Next, in step S22, the result of Nθ-Nin is stored in the memory as the speed difference A, and in step S23, it is determined whether | A | ≥K using the predetermined reference speed difference K. If affirmative, the process proceeds to step S24, and it is determined whether the rotation speed difference A> 0, and if A> 0, the engine rotation because the control rotation speed Nθ is larger than the rotation speed command value Nin, that is, the control rotation speed is higher than the target rotation speed. In order to lower the number, a signal for commanding motor reversal is output to the pulse motor 43 in step S25. As a result, the pulse motor 43 reverses and the engine speed decreases.

On the other hand, when A? 0, since the control rotation speed Nθ is smaller than the rotation speed command value Nin, that is, the control rotation speed is lower than the target rotation speed, a signal for commanding the motor power failure is output in step S26 to increase the engine speed. As a result, the pulse motor 43 is interrupted and the engine speed is increased. If step S23 is negative, the process proceeds to step S27 to output a motor stop signal, whereby the engine speed is maintained at a constant value. Execution of steps S25 to S27 returns to the start.

Next, a characteristic operation of the prime mover control device according to the first embodiment will be described.

At the time of traveling, the brake switch 32 is operated to a traveling position, and the forward and backward conversion switch is operated to a forward position or a reverse position. In this state, when the fuel lever is operated to the idling position and the driving pedal 22a is pressed, the control valve 25 is switched in accordance with the pedal operation amount, and the traveling motor 5 is driven by the hydraulic pressure from the main pump 24. Rotate

At this time, in the delay control section 56, the running flag = 1 and the deceleration flag = 0 are set, and the target rotational speed Nt selected by the selecting section 54 is set as the rotational speed command value Nin (step S14). As a result, the engine speed is controlled to the target rotation speed Nt by the signal output to the pulse motor 43 by the servo control unit 57. In this case, the engine speed is changed in accordance with the operation amount of the travel pedal 22a in accordance with the characteristics of the rotation speed calculation unit 51. Therefore, good acceleration can be obtained, and fuel efficiency and noise can be reduced.

When the travel pedal 22a is released at the time point t1 when the steel sheet travels, the control valve 12 is switched to the neutral position. Accordingly, although the hydraulic brake force acts on the traveling motor 5 in response to the inertia force of the vehicle body, the reduction ratio of the motor rotation speed Nm (vehicle speed) is small because the inertia force of the vehicle body is large, and the motor rotation speed Nm is, for example, As shown in FIG. 8, it is larger than predetermined value Nm1. At this time, the traveling pilot pressure Pt is equal to or less than the predetermined value Pt1, and the running flag = 1 and the deceleration flag = 1 are set in the delay control unit 56, and the rotation speed command value Nin is maintained at the control rotation speed at the start of the deceleration operation. (Step S9). As a result, as shown in FIG. 8, the engine speed is kept constant, and a decrease in pump discharge oil is suppressed. As a result, sufficient oil is sucked in the travel motor 5 from the makeup port 15, and cavitation can be prevented.

When the steel plate traveling ends at the time point t2 and the motor rotation speed Nm decreases to the predetermined value Nm1 or less at the time point t3, the rotation speed command value Nin is gradually decreased (step S8). This slows down the engine speed as shown in FIG. In this case, since the motor rotation speed is low, it is not necessary to increase the make-up pressure as much as the steel sheet travels, and cavitation can be sufficiently prevented by the slow down of the engine rotation speed. The slow down of the engine speed continues until the rotational speed command value Nin becomes less than or equal to the target rotational speed Nt. When rotation speed command value Nin falls to target rotation speed Nt, engine rotation speed will become the value Nmax according to the operation amount of the traveling pedal 22a (step S15-step S13).

On the other hand, when the driving pedal 22a is operated at the time of deceleration of the vehicle and the running pilot pressure Pt becomes larger than the predetermined value Pt1, the deceleration operation is canceled and the deceleration flag = 0 is set (step S6 to step S13). As a result, the slow down of the engine speed is stopped, and the engine speed immediately returns to the value Nmax corresponding to the operation amount of the travel pedal 22a (step S14).

At the time of work, the brake switch 32 is operated to a working position, and the forward and backward conversion switch is operated to a neutral position. When operating the operation lever 28a in this state, the control valve 27 is changed according to the operation amount, and the boom cylinder 4d is driven.

At this time, by the calculation by the control circuit 30, the maximum value selection part 55 selects the larger value of the target rotation speed Nd and the target rotation speed Nx by a fuel lever. Therefore, if the target rotation speed Nx is set to a value suitable for the work by the fuel lever, the engine speed will not be undesirably increased at the time of work, thereby improving operability and fuel economy. In this case, since the characteristic inclination of the rotation speed calculating part 53 is small, setting of target rotation speed Nx is also easy.

According to the first embodiment, since the engine speed is slowed down in accordance with the rotation of the steering motor 5 at the start of the deceleration operation, it is effective for preventing cavitation. That is, since the make-up pressure becomes inadequate when the motor rotation speed Nm is larger than the predetermined value Nm1, the engine rotation speed is kept constant, and when the motor rotation speed Nm is smaller than or equal to the predetermined value Nm1, the make-up pressure is sufficient, so that it is slewed. As a result, sufficient makeup pressure is ensured even at the time of steel plate running, and sufficient makeup flow volume is supplied and cavitation can be prevented reliably. Except for the deceleration operation, since the engine speed increases and decreases according to the operation amount of the travel pedal 22a, good acceleration can be obtained. When the traveling pedal 22a is operated during the slow down of the engine speed, the slow down state is released immediately, and thus, the acceleration can be obtained even during the slow down.

In addition, this embodiment is equally effective even when used when the make-up pressure is insufficient due to the inertia force of the vehicle body in addition to the steel sheet traveling.

Second Embodiment

9 and 10, a second embodiment of the prime mover control device according to the present invention will be described. Hereinafter, differences from the first embodiment will be mainly described.

What is different from the first embodiment from the second embodiment is the processing in the delay control section 56. That is, in the first embodiment, the engine speed is slowed down when the motor speed Nm is equal to or less than the predetermined value Nm1 during the deceleration operation. In contrast, in the second embodiment, the engine speed is slowed down during the deceleration operation, and then the slowdown is prohibited when the motor speed Nm is larger than the predetermined value Nm1.

9 is a flowchart showing a processing procedure in the delay control unit 56 of the prime mover control device according to the second embodiment. In addition, the same code | symbol is attached | subjected to the same place as FIG. 6, and a difference is mainly demonstrated below. As shown in Fig. 9, when it is determined in step S4 that the deceleration operation is started, the deceleration flag = 1 is set in step S5, and the timer is started in step S21. Next, in step S22, it is determined whether or not the timer has timed the predetermined time T1, and if yes, the flow advances to step S7. If negative, the flow advances to step S8.

The operation of this second embodiment will be described with reference to FIG. The deceleration operation is started at the time point t11, and the rotation speed command value Nin gradually decreases until the predetermined time T1 elapses thereafter (step S22 to step S8). As a result, the engine speed is slowed down as shown between the time points t11 to t12. When the engine speed slows down, the make-up pressure decreases with this, and the brake force acting on a vehicle becomes large. As a result, the motor rotation speed Nm gradually decreases as shown. The predetermined time T1 is set to a value that at least prevents cavitation from occurring.

At the time t12 after the predetermined time T1 has elapsed, when the motor speed Nm is larger than the predetermined value Nm1, the slowdown of the engine speed is stopped as indicated by the solid line in FIG. 10, and the engine speed is maintained at the current value (step). S9). Then, when the steel sheet travel ends at the time point t13, and the motor rotation speed Nm becomes the predetermined value Nm1 or less at the time point t14, the slowdown is started (step S8). On the other hand, when the time t12 after the predetermined time T1 has elapsed and the motor speed Nm is equal to or less than the predetermined value Nm1, the slowdown of the engine speed continues as it is indicated by the dotted line in FIG.

According to the second embodiment, the engine speed is reduced by the predetermined time T1 regardless of the motor speed during the deceleration operation, so that the engine speed can be reduced as much as possible while preventing cavitation, thereby improving fuel economy. When the deceleration operation is started and the motor rotational speed drops below the predetermined value Nm1, the slowdown is performed by the same process (step S8). Thereby, the characteristic of the slowdown at the start of the deceleration operation (characteristics of the time points t11 to t12) and the characteristic of the slowdown (after the time point t12 or after t14) when the motor rotation speed Nm is equal to or less than the predetermined value Nm1 are the same. As a result, when the engine speed Nm is less than or equal to the predetermined value Nm1 after the predetermined time T1 has elapsed, the engine speed can be smoothly down as shown by the dotted line in FIG. 10.

In the second embodiment, the engine speed is slowed down by the predetermined time T1 at the start of the deceleration operation. However, the engine speed may be slowed down when the engine speed decreases by the predetermined amount. That is, instead of step S21 and step S22, it is determined whether the engine speed has decreased by a predetermined amount, and if it is affirmative, it progresses to step S7, and if it is negative, it may make a slowdown in step S8. Moreover, the slowdown characteristic (characteristic of the time points t11-t12) at the time of the deceleration operation start, and the slowdown characteristic (after time t12 or after t14) when motor speed Nm is below predetermined value Nm1 may be mutually different.

In addition, although the operation amount of the traveling pedal 22a was detected by the pressure sensor 31 above, for example, a potentiometer may be directly attached to the traveling pedal 22a, and the operation amount may be detected. In addition to the pressure detection by the pressure sensor 31, as a means for detecting the running state, a timer for measuring the time when the travel pedal 22a is pressed, that is, the pressure detection time by the pressure sensor 31, is provided. Thus, it may be determined that the driving state is when the time at which the traveling pedal 22a is operated is more than a predetermined time. According to this, when the operation is frequently repeated such as driving and stopping operation such as the work positioning operation by running, the present control does not operate and good operability can be obtained.

The deceleration operation start may be detected at the time of non-operation of the travel pedal 22a, or the deceleration operation may be detected when the pedal operation amount decreases by a predetermined amount or more. Further, the deceleration operation can be performed by comparing the previous operating pressure (pressure sensor 31) with the current operating pressure, and can be determined as the deceleration when the current operating pressure is smaller than the previous operating pressure.

Although the rotation speed of the travel motor 5 was detected by the rotation speed sensor 35, the rotation speed of the travel motor 5 may be indirectly detected by the vehicle speed sensor. The engine speed may be changed in accordance with the rotation speed of the travel motor 5 during the deceleration operation. In other words, the higher the rotation speed of the traveling motor 5, the larger the engine rotation speed.

As mentioned above, although the wheel type hydraulic excavator was demonstrated as an example as a construction machine, this invention is applicable also to construction machines other than a wheel type.

Claims (5)

Hydraulic pump driven by prime mover, A traveling hydraulic motor driven by pressure oil discharged from the hydraulic pump, In the prime mover control device of a construction machine having a control valve for controlling the flow of pressure oil from the hydraulic pump to the hydraulic motor in accordance with the operation of the operation member, Deceleration detecting means for detecting a deceleration operation of the operation member; Rotation speed detection means for detecting the rotation speed of the hydraulic motor; When the deceleration operation is detected by the deceleration detecting means, the speed of the prime mover is slowed down according to the detection result of the rotational speed detecting means, and when anything other than the deceleration operation is detected, the prime mover is operated according to the operation of the operation member. Motor speed control means for controlling the number of revolutions A prime mover control device for a construction machine, comprising: a. The method of claim 1, In the slow down control by the prime mover rotation speed control means, when the deceleration operation is detected by the deceleration detection means, the rotation speed of the prime mover is fixed if the motor revolution speed detected by the revolution speed detection means is larger than a predetermined value. And the rotation speed of the prime mover is gradually reduced when the detected motor rotation speed is equal to or less than the predetermined value. The method of claim 1, In the slow down control by the prime mover rotation speed control means, when the deceleration operation is detected by the deceleration detection means, the revolution speed of the prime mover is gradually reduced for a predetermined time, and after that predetermined time by the revolution speed detection means. And if the detected motor speed is greater than a predetermined value, the rotation speed of the prime mover is kept constant, and when the detected motor speed is less than or equal to the predetermined value, the prime speed of the prime mover is gradually reduced. The method of claim 1, In the slow down control by the prime mover rotation speed control means, if the deceleration operation is detected by the deceleration detecting means, the revolution speed of the prime mover is gradually reduced by a predetermined amount, and the prime speed is decreased when the prime mover revolution speed decreases by a predetermined amount. When the motor rotation speed detected by the detection means is greater than a predetermined value, the rotation speed of the prime mover is kept constant, and when the detected motor rotation speed is below the predetermined value, the rotation speed of the prime mover is gradually reduced. Prime mover control device. Hydraulic pump driven by prime mover, A traveling hydraulic motor driven by the pressure oil discharged from the hydraulic pump; A control valve for controlling the flow of pressure oil from the hydraulic pump to the hydraulic motor in accordance with the operation of the operation member; Wheel type hydraulic excavator which has the prime mover control apparatus in any one of Claims 1-4.