JP5596583B2 - Drive control device for work machine - Google Patents

Description

  The present invention includes a second motor generator that drives and brakes a predetermined movable portion separately from an assist motor as a first motor generator that assists the rotation of the engine, and these first and second motor generators. A power control device for a work machine that stores power generated by the power storage device, and supplies power that cannot be stored in the power storage device among power generated by the second motor generator to the first motor generator. The present invention relates to a drive control device for a work machine that is consumed by assisting rotation of an engine.

  A conventional drive control device for a work machine is configured to limit the assistance of rotation of the engine by the assist motor in accordance with the remaining amount of power stored in the power storage device (see Patent Document 1).

JP 2005-83242 A

  By the way, a drive control device for a work machine includes a second motor generator that drives and brakes a predetermined movable portion separately from an assist motor as a first motor generator that assists the rotation of the engine. is there. A drive control device for a hydraulic excavator, which is a type of work machine, includes a second motor generator as a turning motor serving as a drive source for a turning body as a predetermined movable part. Hereinafter, the turning motor that is the second motor generator is referred to as an “electric turning motor”. This electric swing motor generates electric power by performing regenerative braking on the swing body. This electric power is stored in the power storage device in the same manner as the electric power generated by the assist motor. Generated by the electric swing motor when the amount of charge of the power storage device is not sufficient, or when the electric power generated by the electric swing motor per unit time exceeds the power that the power storage device can absorb per unit time Power is excessive for the battery. In order to prevent the excess power from being wasted, it has been conventionally performed to supply the excess power to the assist motor and to assist the rotation of the engine by the assist motor.

  However, when the engine is assisted by the assist motor using excessive electric power generated by the electric swing motor, the engine may be operated at an overspeed exceeding the rated speed and exceeding the assist range. Yes, there is concern that the engine will be overloaded or approach the physical limits.

  The present invention has been made in consideration of the above-described circumstances, and the object thereof is to provide excessive power for the power storage device among the power generated by the second motor generator different from the first motor generator. An object of the present invention is to provide a drive control device for a work machine that can prevent the engine speed from becoming excessive when the first motor generator is used to assist the rotation of the engine.

  In order to achieve the above object, the present invention is configured as follows.

[1] A drive control device for a work machine according to the present invention includes an engine composed of an internal combustion engine, a hydraulic pump driven by the engine, and a hydraulic actuator driven by pressure oil discharged from the hydraulic pump. A first motor / generator coupled to the engine so as to be capable of transmission, a second motor / generator for driving a predetermined movable part of the work machine, and performing regenerative braking for the movement, and the first motor / generator. A power storage device that stores the generated power and the power generated by the second motor generator, and excess power relative to the power storage device among the power generated by the second motor generator, In a drive control device for a work machine, comprising an assist control means for supplying to a motor generator and consuming with assistance of rotation of the engine, the rated rotational speed of the engine Upper limit rotation speed command means for instructing as an upper limit rotation speed, engine rotation speed detection means for detecting the engine rotation speed per unit time, pump output estimation means for calculating the estimated output of the hydraulic pump, and the second motor generator Assist request generating means for calculating excess power as an assist request output for the power storage device among the power generated by the machine, target rotational speed calculating means for calculating a target rotational speed of the engine based on the estimated output, Engine control means for controlling the fuel injection amount of the engine based on the target speed, excess demand output obtained by subtracting the estimated output from the assist demand output, and engine speed by the engine speed detection means control switching of on the basis of the detection value, switches the control mode for controlling the first motor generator and the engine And the control switching means is provided when the excessive required output is equal to or lower than a predetermined reference excessive required output and the engine speed detected by the engine speed detecting means is lower than the upper limit speed. The normal mode is selected as the control mode, the excessive required output is larger than the reference excessive required output, and the engine speed detected by the engine speed detecting means is required for work of the work machine. when the preset or reference rotation speed as the lowest engine speed, to select the rotational speed drop mode as the control mode, the engine control means usually means for controlling the engine rotational speed in the normal mode And a speed reduction means for controlling the engine speed in the speed reduction mode, wherein the normal means outputs the assist request output. And subtracting the assist rotational speed obtained by assisting the engine by the first motor generator from the target rotational speed to obtain a target rotational speed for the engine, and fuel injection based on the target rotational speed for the engine And the engine speed reduction means stepwise reduces the fuel injection quantity of the engine to a fuel injection quantity corresponding to a predetermined low engine speed lower than the reference engine speed. To do.

In the drive control device for the work machine described in “[1]”, the condition that the rotation speed reduction mode is selected as the control mode is that the excessive required output is larger than the reference excessive required output and the engine rotational speed is detected. is set to the engine rotational speed detected by the means is greater than or equal to the reference rotational speed, the reference rotational speed is previously set as the lowest engine speed required for the work of the working machine, engine braking the rotational speed drop means of control means, the fuel injection amount of the engine, the step to reduce the fuel injection amount of low predetermined substantial low rotational speed than the reference speed. In these cases, excessive electric power for the power storage device among electric power generated by the second motor generator different from the first motor generator is consumed by the first motor generator to assist engine rotation. In addition, it is possible to prevent the engine speed from becoming excessive.

[2] The work machine drive control device according to the present invention is the work machine drive control device according to [1], wherein the engine control means controls the fuel injection amount of the engine. And an engine speed command means for commanding the target engine speed to the fuel injection amount control device. The engine speed command means constitutes the normal means together with the fuel injection amount control device. And a rotation speed drop command means that constitutes the rotation speed drop means together with the fuel injection amount control device, and the normal command means is obtained by subtracting the assisting rotation speed from the target rotation speed. The engine target rotation speed is commanded to the fuel injection amount control device, and the rotation speed decrease command means sets the fuel injection amount with the low rotation speed as the engine target rotation speed. It is characterized by instructing the control device.

  In the drive control device described in “[2]”, the normal command means of the engine speed command means uses the fuel injection amount control to set the target engine speed obtained by subtracting the assist speed from the target speed. The fuel injection amount control device controls the fuel injection amount of the engine based on the target engine speed from the normal command means. Thereby, control of the engine speed in the normal mode can be realized. The engine speed reduction command means of the engine speed command means commands the fuel injection amount control device with the low engine speed as the engine target speed, and the fuel injection amount control device receives the engine speed reduction command means from the engine speed reduction command means. The fuel injection amount of the engine is controlled based on the target engine speed (predetermined low speed). Thereby, control of the engine speed in the speed reduction mode can be realized.

[3] The work machine drive control device according to the present invention is the work machine drive control device according to [1], wherein the engine control means controls the fuel injection amount of the engine. And an engine speed command means for commanding the target engine speed to the fuel injection amount control device. The engine speed command means constitutes the normal means together with the fuel injection amount control device. is intended to, the fuel injection amount control device includes a small injection quantity processing means as poor stage later the rotational speed, the small injection quantity processing means, the low rotational speed equivalent quantity of fuel injection amount of the engine It is characterized by being controlled.

  In the drive control device described in “[3]”, the engine speed command means commands the fuel injection amount control device to set the target engine speed obtained by subtracting the assisting speed from the target speed. The fuel injection amount control device controls the fuel injection amount of the engine based on the target engine speed from the engine speed command means. Thereby, control of the engine speed in the normal mode can be realized. Further, the small injection amount processing means of the fuel injection amount control device controls the fuel injection amount of the engine to a low rotation speed equivalent amount. Thereby, control of the engine speed in the speed reduction mode can be realized.

  In particular, in the drive control device described in “[3]”, the small injection amount processing means of the fuel injection amount control device controls the fuel injection amount of the engine to a low rotational speed equivalent amount, that is, “[2]”. The engine speed reduction command means of the engine speed command means does not need to perform processing for instructing the fuel injection amount control apparatus to use the low speed as the engine target speed as in the drive control device described in the above. Controlling the number to a predetermined low rotational speed can be realized more quickly than the drive control device described in “[2]”.

[4] The drive control device for a work machine according to the present invention is the drive control device for a work machine according to any one of “[1]” to “[3]”, wherein the control switching unit has a control mode. After the transition from the normal mode to the rotational speed reduction mode, the excessive required output is equal to or lower than a predetermined reference excessive required output, and the engine rotational speed detected by the engine rotational speed detecting means is the upper limit rotational speed. The control mode is returned to the normal mode when it becomes lower than the normal mode.

In the drive control device described in “[4]”, excess electric power generated by the second motor generator is supplied to the first motor generator for consumption by the power storage device. In addition, after avoiding the engine speed exceeding the upper limit number, it is possible to return to the state in which excessive electric power is consumed by the first electric motor again.

[5] driving control device for a working machine according to the present invention is characterized in that in the drive control apparatus according to any one of the "[1]" - "[4]", the Assist control means, It is determined whether or not the assist request output is higher than a predetermined reference request output. If the result of this determination is true, the assist request output is subtracted from the assist request output. It is characterized by correcting.

In the driving control device according to this "[5]", Assist control unit, when the assist request output is higher than the reference required output in the normal mode, by subtracting a predetermined reference required output from the assist required output Then, the assist request output is corrected. Accordingly, it is possible to prevent over-rotation of the engine due to assisting the rotation of the engine by the first motor generator based on the assist request output in the normal mode.

  According to the drive control device for a work machine according to the present invention, as described above, of the power generated by the second motor generator different from the first motor generator, excessive power is supplied to the power storage device. It is possible to prevent the engine speed from becoming excessive when it is consumed by one motor generator to assist the rotation of the engine. As a result, it is possible to prevent an excessive load that approaches or exceeds the physical limit from being applied to the engine.

It is a figure which shows the hydraulic shovel which is a working machine with which the drive control apparatus which concerns on embodiment of this invention is applied. It is a figure which shows the drive control apparatus which concerns on embodiment of this invention. FIG. 3 is a block diagram showing a configuration for engine control in the drive control device shown in FIG. 2. It is a figure which shows the detail of the determination table shown in FIG. It is a flowchart which shows the process performed by the vehicle body controller shown in FIG. It is a figure which shows an example of the change of the engine speed obtained by the process shown in FIG. It is a block diagram which shows the structure for engine control in the drive control apparatus which concerns on 2nd Embodiment of this invention.

[First Embodiment]
A drive control apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

  A hydraulic excavator 1 shown in FIG. 1 includes a traveling body 2 that travels by driving a crawler belt 2a, a revolving body 3 that is a movable unit coupled to the traveling body 2 via a revolving bearing 14, and the revolving body. 3 is provided with a front working device 6 provided at the front portion.

  The traveling body 2 includes a left frame 2b that forms a skeleton on the left side of the traveling body 2, and a right frame (not shown) positioned in parallel with the left frame 2b. The left frame 2b is provided with a left traveling motor 20 with a speed reducer. The crawler belt 2a is wound around the left frame 2b, and the crawler belt 2a is driven by the output of the left traveling motor 20 being transmitted to the crawler belt 2a. The right frame side of the traveling body 2 is similarly configured. The right traveling motor 21 provided in the right frame is illustrated by symbols in FIG.

  The front working device 6 includes a boom 7 that is pivotably coupled to the front portion of the revolving structure 3, an arm 8 that is pivotably coupled to the boom 7, and a bucket 9 that is pivotally coupled to the arm 8. A backhoe type front working device provided, which is driven by contraction or expansion of at least one hydraulic cylinder of a boom cylinder 7a (hydraulic cylinder), an arm cylinder 8a (hydraulic cylinder) and a bucket cylinder 9a (hydraulic cylinder). It has become.

The swivel body 3 includes a cab 4 on the left side of the front working device 6, and a machine room 5 behind the cab 4. The machine room 5, an engine 10 composed of an internal combustion engine, the pump unit 11 driven by the engine 10, i.e. main pump 11a (variable displacement hydraulic pump, shown in oil圧記No. 2) and a pilot pump 11b (Constant displacement pump, indicated by hydraulic symbols in FIG. 2). The main pump 11 is a hydraulic source of hydraulic pressure supplied to the left traveling motor 20, the right traveling motor 21, the boom cylinder 7a, the arm cylinder 8a, and the bucket cylinder 9a.

  In the machine room 5 of the revolving structure 3, an assist motor 12 as a first motor generator coupled to the engine 10 so as to be capable of transmission and a battery 13 as a power storage device are provided. When the assist motor 12 is driven by the engine 10, it functions as a generator to generate electric power, and the electric power is stored in the battery 13. Further, the assist motor 12 acts as an electric motor when power is supplied from the battery 13 to assist the rotation of the engine 10.

  The machine room 5 is further provided with an electric turning motor 30 as a second motor generator different from the first motor generator. The electric swing motor 30 becomes an electric motor when electric power is supplied from the battery 13, and drives the swing body 3. When the swing speed of the swing body 3 is reduced, the swing body 3 is driven. On the other hand, it becomes a generator that performs regenerative braking and generates electric power. The electric power generated by the electric turning motor 30 is stored in the battery 13.

  As shown in FIG. 2, the drive control apparatus 100 according to the first embodiment includes the above-described engine 10, the above-described pump unit 11 (main pump 11 a and pilot pump 11 b), the above-described assist motor 12, In addition to the above-mentioned electric swing motor 30, the above-mentioned boom cylinder 7a, the above-mentioned arm cylinder 8a, the above-mentioned bucket cylinder 9a, the above-mentioned left traveling motor 20, and the above-mentioned right traveling motor 21, the boom cylinder 7a and the bucket 9 includes a boom / bucket operation lever device 101 for instructing an operation 9 and a turning / arm operation lever device 102 for instructing the operation of the electric swing motor 30 and the operation of the arm cylinder 8a. The boom / bucket operation lever device 101 is provided on the right side of the driver seat in the cab 4, and the turning / arm operation lever device 102 is provided on the left side of the driver seat in the cab 4.

Boom and bucket control lever device 101 includes a tilt-operable operating levers 1 01a in all directions from a neutral position, the pilot pressure corresponding to the tilt amount for each of tilting directions of front, rear, left and right from a neutral position of the operating lever device 101a Is provided with a pilot valve (not shown) that generates the pilot pump 11b as a hydraulic pressure source. And small range of a preset tilt amount around the neutral position of the operating levers 1 01a, the preset tilt amount from the vicinity of the maximum tilting amount of the operating levers 1 01a to the maximum inclination of the micro range except, the pilot valve is adapted to output a high pilot pressure greater the tilt amount from the neutral position of the operating levers 1 01a. By tilting operation of the forward direction from the neutral position of the operating lever device 101a are adapted to the pilot pressure P1 of directing boom lowering is output, the boom by tilting operation of the backward from the neutral position of the operating levers 1 01a being adapted to pilot pressure P2 is output to command raising, commanding the bucket crowding (rotational direction of the bucket 9 approaching the cab 4) by tilting operation in the left direction from the neutral position of the operating levers 1 01a being adapted to pilot pressure P3 is output to the pilot pressure for commanding the operation bucket dumping by tilting operation from the neutral position of the levers 1 01a to the right (pivoting direction of the bucket 9 away from the cab 4) P4 is output.

Pivot arm operating lever device 102, a tilting operation can be operated levers 1 0 2 a back and forth and left and right from a neutral position, each tilting direction of the left and right front and rear from the neutral position of the operating levers 1 02a according to the tilt amount A pilot valve (not shown) for generating the pilot pressure using the pilot pump 11b as a hydraulic pressure source is provided. Also in the swing and arm control lever device 102, similarly to the boom and bucket control lever device 101, and the minute range of a preset tilt amount around the neutral position of the operating levers 1 02a, the maximum operating levers 1 02a except for a small range of a preset tilt amount up to the tilt amount from the vicinity of the tilt amount, the pilot valve, so as to output a high pilot pressure greater the tilt amount from the neutral position of the operating levers 1 02a It has become. Operation and so the pilot pressure P5 to command (rotational direction of the arm 8 away from the cab 4) arm dumping is output by the tilting operation from the neutral position of the levers 1 02a in the forward direction, the operation levers 1 0 2 a are adapted to pilot pressure P6 which direct arm-crowding (rotational direction of the arm 8 to approach the cab 4) is output by the tilting operation of the backward from the neutral position, operating levers 1 by tilting operation in the left direction from the neutral position 02a being adapted pilot pressure P7 of directing the left turn is output, the right turn by tilting operation in the right direction from the neutral position of the operating levers 1 02a The commanded pilot pressure P8 is output.

  It is the left traveling operation lever device and the right traveling operation lever device that command the respective operations of the traveling motors 20 and 21, but these are not shown. Each of these left travel control lever device and right travel control lever device is an operation lever that can be tilted back and forth from the neutral position, and a pilot pressure corresponding to the tilt amount for each tilt direction from the neutral position to the front and back. Is provided with a pilot valve that generates a pilot pump as a hydraulic pressure source, and is arranged in the left-right direction in front of the driver's seat in the cab 4. Also in the left travel operation lever device and the right travel operation lever device, as in the boom / bucket operation lever device 101, a minute range of the tilt amount set in advance around the neutral position of the operation lever and the maximum tilt amount of the operation lever The pilot valve is configured to output a higher pilot pressure as the tilt amount from the neutral position of the operation lever increases, except for a minute range of the preset tilt amount from the vicinity of to the maximum tilt amount.

  The drive control device 100 further includes a hydraulic pilot-type directional switching valve in a hydraulic line connecting the boom cylinder 7a, the arm cylinder 8a, the bucket cylinder 9a, the left traveling motor 20 and the right traveling motor 21 with the main pump 11a. The boom direction control valve 103, the arm direction control valve 104, the bucket direction control valve 105, the left travel direction control valve 106, and the right travel direction control valve 107 are provided. Each of these directional control valves 103 to 107 controls the flow of pressure oil supplied from the main pump 11a to each of the boom cylinder 7a, arm cylinder 8a, bucket cylinder 9a, left travel motor 20 and right travel motor 21. It is like that. The pilot pressure for the boom direction control valve 130 and the bucket direction control valve 105 is supplied from the boom / bucket operation lever device 101, and the pilot pressure for the arm direction control valve 104 is the swivel / arm The pilot pressure for each of the left travel direction control valve 106 and the right travel direction control valve 107 is supplied from the operation lever device 102. The left travel operation lever device (not shown) and the right travel operation lever It is supplied from each of the devices (not shown).

  The drive control device 100 further converts the direct current power of the battery 13 into alternating current power and supplies it to the electric swing motor 30, and the pilot pressure generated by the swing / arm operation lever device 102 is converted into a left-handed rotation as an electric signal. The pilot pressure sensor 137 that converts and outputs the rotation command signal Sp7, and the pressure sensor pilot that converts the pilot pressure generated by the turning / arm operation lever device 102 into the right turning command signal Sp8 that is an electrical signal and outputs it. And a pressure sensor 138.

  The drive control device 100 further includes a vehicle body controller 110. The vehicle body controller 110 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a predetermined control program, a RAM (Random Access Memory) as a storage area for information processing work performed by the CPU, and the like. The control program stored in the ROM is executed by the CPU, and various processes relating to the control of the hydraulic excavator 1 are performed.

  The vehicle body controller 110 includes electric swing motor control means 111 that is a means set by a control program. The electric swing motor control means 111 controls the electric swing motor 30 by controlling the inverter 121 based on the left turn command signal Sp7 and the right turn command signal Sp8 from the pilot pressure sensors 137 and 138, respectively. is there. More specifically, when the left turn command electric signal Sp7 is input to the vehicle body controller 110, the electric turning motor 30 has a higher left turn speed as the pilot pressure indicated by the left turn command signal Sp7 is higher. When the right turn command signal Sp8 is input to the vehicle body controller 110, the higher the pilot pressure based on the right turn command signal Sp8 is, the faster the right turn speed is. Thus, the inverter 121 is controlled.

  The vehicle body controller 110 further includes pump output estimating means 112 which is means set by the control program. In relation to the pump output estimating means 112, the drive control device 100 includes a pump discharge pressure sensor 139 in the discharge line of the main pump 11a. The pump discharge pressure sensor 139 detects the discharge pressure Pm of the main pump 11a and outputs a discharge pressure detection signal Spm which is an electric signal corresponding to the discharge pressure Pm. The drive control apparatus 100 further includes pilot pressure sensors 131 to 136 in association with the pump output estimating means 112. These pilot pressure sensors 131 and 132 are respectively provided in pilot pipelines for guiding pilot pressures P1 and P2 from the boom / bucket operation lever device 101 to the boom direction control valve 103, and pilots in the pilot pipelines are provided. The pressure is detected, and pilot pressure detection signals Sp1 and Sp2, which are electrical signals corresponding to the pilot pressure, are output. That is, the pilot pressure sensors 131 and 132 are means for detecting command values for the operation of the boom 7. The pilot pressure sensors 133 and 134 are provided in the pilot pipes that lead the pilot pressures P3 and P4 from the boom / bucket operation lever device 101 to the bucket direction control valve 105, respectively. Is detected, and pilot pressure detection signals Sp3 and Sp4, which are electrical signals corresponding to the pilot pressure, are output. That is, these pilot pressure sensors 133 and 134 are means for detecting a command value for the operation of the bucket 9. The pilot pressure sensors 135 and 136 are respectively provided in the pilot pipelines that lead the pilot pressures P5 and P6 from the turning / arm operation lever device 102 to the arm direction control valve 104, and the pilot pressures in the pilot pipelines are provided. And pilot pressure detection signals Sp5 and Sp6, which are electrical signals corresponding to the pilot pressure, are output. That is, these pilot pressure sensors 135 and 136 are means for detecting command values for the operation of the arm 8. The discharge pressure detection signal Spm output from the pump discharge pressure sensor 139 and the pilot pressure detection signals Sp1 to Sp6 output from the pilot pressure sensors 131 to 136 are input to the vehicle body controller 110, respectively. Yes. The pump output estimation means 112 calculates the discharge flow rate of the main pump 11a based on the pilot pressure detection signals Sp1 to Sp6, and estimates the main pump 11a based on the discharge flow rate and the discharge pressure indicated by the discharge pressure detection signal Spm. The output Wp is calculated.

The vehicle body controller 110 further includes target rotational speed calculation means 113 which is a means set by the control program. This target speed calculating means calculates a target value of the engine speed (the speed of the engine 10 per unit time), that is, the target speed Rt, based on the estimated output Wp calculated by the pump output estimating means 112. It is. The engine 10 includes a main pump 11a, an assist motor 12, and a pilot pump 11b, a cooling fan for radiating heat from a heat exchanger such as an oil cooler and a radiator, and cooling used for cooling the inverters 121 and 122 and the assist motor 12. Auxiliary equipment such as a cooling pump for circulating water is connected to be able to transmit. For this reason, when the output of the assist motor 12 is 0 and the discharge flow rate of the main pump 11a is minimum, there is a minimum between the main pump 11a, the assist motor 12, the pilot pump 11b, and the auxiliary machine and the engine 10. Drag resistance occurs. The minimum output Wmin of the engine 10 is a minimum output necessary for operating against the minimum drag resistance. In order to drive the front working device 6 and the traveling body 2, it is necessary to drive the main pump 11a to be larger than the minimum discharge flow rate, and the output of the engine 10 in response to the necessity is the driving of the main pump 11a. The total output Wt of the output required for the output and the minimum output Wmin. Target speed Rt of the preceding, based on the estimated output Wp of the main pump 11a, is intended to be calculated for the purpose of outputting the total output Wt engine 10.

The vehicle body controller 110 further includes an engine speed command means 114 that is a means set by a control program. This engine speed command means 114 uses a part or all of the target speed Rt calculated by the target speed calculation means 113 described above for use in controlling the fuel injection amount of the engine 10. A command is given to the fuel injection amount control device 130 as Re. The fuel injection amount control device 130 includes a CPU, a ROM, and a RAM, and controls the fuel injection amount of the engine 10 based on the target engine speed Re commanded by the engine speed command means 114. It is. The engine speed command means 114 and the fuel injection amount control device 130 constitute engine control means for controlling the fuel injection amount of the engine 10.

The vehicle body controller 110 is a means set by a control program, and includes an assist motor control means 115 (assist control means) for controlling the assist motor 12. The assist motor control means 115, adapted to control the assist motor 12 by controlling the inverter 122 of the inverter 121 and 122 when driving the assist motor 12 with the electric energy stored in the battery 13 When the assist motor 12 is driven using the electric power generated by the electric turning motor 30, the assist motor 12 is controlled by controlling both the inverters 121 and 122. In FIG. 2, reference numeral 123 denotes a chopper circuit that stabilizes the voltage of power led from the battery 13 to each of the inverters 121 and 122.

  The engine 10 is provided with a magnetic pickup type engine speed sensor 131. The engine speed sensor 131 detects an actual engine speed and outputs an engine speed detection signal Sr that is an electrical signal corresponding to the engine speed. The engine speed detection signal Sr is input to the vehicle body controller 110.

  The engine speed command means 114 described above uses the target speed Rt calculated by the target speed calculation means 113 as the engine target when the regenerative braking by the electric swing motor 30 is not performed on the swing body 3. It is set to instruct the fuel injection amount control device 130 as the rotational speed Re. As a result, the fuel injection amount control device 130 determines the fuel injection amount so that the actual engine speed R indicated by the engine speed detection signal Sr increases to Re based on the engine target speed Re (Re = Rt). Control. In the state where the actual engine speed R is lower than the engine target speed Re (Re = Rt), the assist motor control means 115 described above controls the inverter 122 to supply power from the battery 13 to the assist motor 12. That is, it is set so that the assist motor 12 is powered as an electric motor and the assist motor 12 assists the rotation of the engine 10.

  In a state where the regenerative braking by the electric swing motor 30 is performed on the swing body 3, when the charge state (charged amount) of the battery 13 reaches the limit, the electric power that can be charged per unit time of the battery 13 is If the electric swing motor 30 is smaller than the electric power generated per unit time, the electric power generated by the electric swing motor 30 is excessive with respect to the battery 13, and in this case, the assist motor control means 115 causes the excessive electric power to be generated. Is supplied to the assist motor 12, and the assist motor 12 is set to assist the rotation of the engine 10. The drive control device 100 according to the first embodiment is characterized by the configuration for causing the assist motor 12 to assist the rotation of the engine 10 in this way. The features will be described next.

  The vehicle body controller 110 includes assist request generation means 116 that is a means set by a control program. The assist request generator 116 uses the assist motor 12 to assist the rotation of the engine 10 using all of the excessive power that cannot be charged in the battery 13 among the power generated by the electric swing motor 30. As an output, an assist request output Wa is calculated. When calculating the assist request output Wa, the assist request generation unit 116 first determines the braking torque of the electric swing motor 30 required for regenerative braking and the number of revolutions per unit time of the electric swing motor 30 during regenerative braking. Calculates the electric power generated by the electric swing motor 30, calculates the charge state (charged amount) of the battery 13 based on the progress of power input / output already performed in the battery 13 and the terminal voltage of the battery 13, and Using the electric power obtained by the calculation and the charging state, excessive electric power that cannot be charged in the battery 13 among electric power generated by the electric swing motor 30 is calculated, and the excessive electric power is calculated as the assist request output Wa. To do. Further, the assist request generation means 116 obtains excessive power by subtracting power that can be absorbed by the battery 13 per unit time from power generated by the electric swing motor 30 per unit time. The power is set as the assist request output Wa. Various information used when the assist request generation means 116 calculates the assist request output Wa, that is, the braking torque of the electric swing motor 30 required for regenerative braking, and the unit time of the electric swing motor 30 during regenerative braking. The number of revolutions, the progress of power already in and out of the battery 13, the terminal voltage of the battery 13, the power generated by the electric turning motor 30 per unit time, and the power that the battery 13 can absorb per unit time All are information handled by the vehicle body controller 110 for controlling the inverters 121 and 122, and are temporarily stored in the RAM of the vehicle body controller 110.

  The vehicle body controller 110 is provided with an upper limit rotation speed input device 140. The upper limit rotational speed input device 140 is a dial operation type input device, and is an upper limit rotational speed command means for commanding the vehicle body controller 110 with the rated rotational speed of the engine 10 as the upper limit rotational speed Rlim of the engine 10.

The vehicle body controller 110 includes control switching means 117 that is a means set by a control program. The control switching means 117 is based on a preset correspondence relationship between each of the four types of states of the drive control device 100 and each of the three types of control modes, that is, the normal mode, the rotation speed reduction mode, and the assist stop mode. The control mode is determined according to the state of the drive control device 100 . The correspondence relationship between the state of the drive control device 100 and the control mode is defined by the determination table 117a shown in FIG. The determination table 117a is stored in the ROM of the vehicle body controller 110. Next, the normal mode, the rotation speed reduction mode, and the assist stop mode will be described with reference to FIG.

  The normal mode is a control mode that assists the rotation of the engine 10 based on the assist request output Wa, and is an excess request output ΔW that is an excess of the assist request output Wa with respect to the estimated output Wp, that is, the estimated output Wp from the assist request output Wa. When the engine speed R is lower than the upper limit rotational speed Rlim input by the upper limit rotational speed input device 140 (ΔW ≦ Wc, R <Rlim) Case). In the first embodiment, the predetermined reference excess request output Wsc is set to the aforementioned minimum output Wmin, and is set in advance in the ROM of the vehicle body controller 110.

  This normal mode is also used when the excessive required output ΔW is higher than the reference excessive required output Wsc and the engine speed R is lower than the reference speed Rc (when ΔW> Wc, R <Rc). It is done. The reference rotation speed Rc is set in advance as the minimum rotation speed at which the front working device 6 can work, and is stored in the ROM of the vehicle body controller 110.

  The rotation speed reduction mode prevents the engine 10 from being over-rotated by assisting the rotation of the engine 10 by the assist motor 12, that is, exceeds the upper limit rotation speed Rlim input by the upper limit rotation speed input device 140. This is a control mode for preventing the engine 10 from rotating. This rotational speed drop mode is used when the excessive required output ΔW is higher than the reference excessive required output Wsc and the engine speed R is equal to or higher than the reference rotational speed Rc (when ΔW> Wc, R ≧ Rc). Note that when the excessive required output ΔW decreases below the reference excessive required output Wsc in this rotational speed lowering mode, that is, when “ΔW ≦ Wc, R <Rlim”, the control mode is switched to the normal mode described above.

  The assist cancellation mode is a control mode in which the assist motor 12 stops assisting the rotation of the engine 10, and the engine speed R is equal to or higher than the upper limit speed Rlim regardless of the excessive required output ΔW (R ≧ Rlim). Case).

  The engine speed command means 114 described above determines the target engine speed Re (Re <Rt) in the normal mode and commands the fuel injection amount control device 130, and the above-described rotation. Rotational speed decrease command means 114b for determining the target engine rotational speed Re and instructing the fuel injection amount control device 130 in the speed decreasing mode is provided. These normal command means 114a and rotation speed drop command means 114b are also set by the control program. Details of the normal command means 114a and the rotation speed drop command means 114b will be described below.

  In the normal mode, a part of the engine speed R for maintaining the output (estimated output Wp) of the main pump 11a is due to the assist motor 12 assisting the rotation of the engine 10 by an amount corresponding to the assist request output Wa. Is. The normal command means 114a of the engine speed command means 114 uses the engine speed obtained by subtracting the assist speed Ra corresponding to the assist request output Wa from the target speed Rt as the engine target speed Re, and the fuel injection amount. The controller 130 is instructed. Therefore, the target engine speed Re is lower than the target engine speed Rt.

  Since the drive source of the swing body 3 is the electric swing motor 30, the oil discharged from the main pump 11a is not necessary when the front working device 6 is not operating, that is, the estimated output Wp is the lowest. At this time, the engine speed R need not be equal to or higher than the reference speed Rc. In the first embodiment, even when the front working device 6 is not in operation, the normal command means 114a performs the target engine rotation during the supply of electric power to the electric swing motor 30 and during the regenerative braking of the electric swing motor 30. The number Re is set to be determined within a range equal to or higher than the reference rotational speed Rc, so that the engine rotational speed R does not fall below the reference rotational speed Rc during work on the excavator 1.

  The engine speed reduction command means 114b determines the engine target engine speed Re to be a preset low engine speed Rl and commands the fuel injection amount control device 130. The low rotational speed Rl may be a rotational speed lower than the reference rotational speed Rc, and may be 0. However, when the assist motor 12 no longer assists the engine 10, the low rotational speed Rl is equal to or lower than the idle rotational speed Ri. When only the engine speed can be obtained, the engine 10 stops. In this case, when the assist motor 12 suddenly stops due to some abnormality and the engine 10 is no longer supported, the engine 10 stops during the operation of the hydraulic excavator 1, which is not preferable for safety. In the first embodiment, the low engine speed Rl is set higher than the idle engine speed Ri so that the engine 10 is not stopped even if the assist of the assist motor 12 to the engine 10 is suddenly stopped.

  The normal command means 114a and the fuel injection amount control device 130 constitute normal means for controlling the engine speed in the normal mode. The engine speed reduction command means 114b and the fuel injection amount control device 130 constitute engine speed reduction means for controlling the engine speed in the engine speed reduction mode.

  The above-described assist motor control means 115 consumes the electric power generated by the electric swing motor 30 in the normal mode and the rotation speed reduction mode, so that the assist motor 12 is in a state of assisting the engine 10, that is, Normal control means 115a for controlling the inverters 121 and 122 based on the assist request output Wa, and assist stop control means 115b for controlling the inverters 121 and 122 so that the assist of the electric swing motor 30 by the assist motor 12 is stopped in the assist stop mode. And. These normal control means 115a and assist stop control means 115b are also means set by the control program. Details of the normal control means 115a will be described next.

  The normal control means 115a determines whether or not the assist request output Wa is larger than a predetermined reference request output Wac, and subtracts the reference request output Wac from the assist request output Wa when the result of this determination is true. Thus, the assist request output Wa is corrected, and the inverters 121 and 122 are controlled such that the assist motor 12 is in a state of assisting the engine 10 by consuming the corrected assist request output War (War = Wa−Wac). .

  Of the operations of the drive control apparatus 100 according to the first embodiment, operations when regenerative braking is performed on the revolving structure 3 by the electric swing motor 30 will be described with reference to FIGS. 5 and 6.

  The vehicle body controller 110 acquires the engine speed R detected by the engine speed sensor 131, acquires the pilot pressures P1 to P6 detected by the pilot pressure sensors 131 to 136, and discharges the pump pump. The discharge pressure Pm of the main pump 11a detected by the pressure sensor 139 is acquired (step S1).

Next, the pump output estimating means 112 of the vehicle body controller 110 calculates an estimated output Wp based on the pilot pressures P1 to P6 and the discharge pressure Pm (step S2). Further, the assist request generation means 116 of the vehicle body controller 110 calculates an assist request output Wa based on information related to the control of the inverters 121 and 122 stored in the RAM of the vehicle body controller 110 (step S2). The target speed calculating means 113 of the vehicle body controller 110, based on the estimated output Wp calculated by pump output estimating unit 112, and Ru to output the sum output Wt of this estimated output Wp and minimum output Wmin engine 10 A target rotation speed Rt is calculated (step S2).

  Next, the control switching means 117 of the vehicle body controller 110 refers to the determination table 117a based on the engine speed R, the estimated output Wp, and the assist request output Wa, so that the excess required output ΔW and the engine speed R are in the determination table 117a. It is determined which of the states corresponds to (step S3). When the determination result is “ΔW ≦ Wsc, R <Rlim”, the control switching unit 117 selects the normal mode as the control mode (step S4), and the determination result is “ΔW> Wsc, R ≧ Rc”. ”, The control switching means 117 selects the rotation speed reduction mode as the control mode (step S5), and if the result of the determination is“ ΔW> Wsc, R <Rc ”, the control switching means 117 is in the control mode. The normal mode is selected (step S6), and if the determination result is “R ≧ Rlim”, the control switching means 117 selects the assist stop mode as the control mode (step S7).

  Next, the engine speed command means 114 of the vehicle body controller 110 uses a part of the target speed Rt as the engine target speed Re (() in the control mode selected in any one of steps S4 to S7. Re <Rt) is determined, and the engine target rotational speed Re is commanded to the fuel injection amount control device 130. Specifically, in the normal mode, the engine speed command means 114 uses the normal command means 114a to calculate the remaining engine speed obtained by subtracting the assist speed Ra corresponding to the assist request output Wa from the target speed Rt. Then, the target engine speed Re (Re <Rt) is determined, and the engine target speed Re is commanded to the fuel injection amount control device 130. In the engine speed reduction mode, the engine engine speed command means 114 determines the engine target engine speed Re to be the low engine speed Rl by the engine speed decrease instruction means 114b. Further, in the assist stop mode, the engine speed command means 114 determines the target speed so that the engine speed falls within the range from the idle speed Rc to the upper limit speed Rlim by the normal command means 114a.

  In parallel with the processing by the engine speed command means 114, the assist motor control means 115 of the vehicle body controller 110 controls the assist motor 12. That is, the assist motor control means 115 is supplied from the electric swing motor 30 to the assist motor 12 by controlling the inverters 121 and 122 based on the control mode selected in any one of steps S4 to S7. Control power. Specifically, in the normal mode and the rotation speed reduction mode, the assist motor control unit 115 is configured to output the assist request output Wa or the corrected assist request from the excess electric power generated by the electric swing motor 30 by the normal control unit 115a. The inverters 121 and 122 are controlled so that the assist motor 12 assists the engine 10 by consuming electric power corresponding to the output War. On the other hand, in the assist stop mode, the assist motor control means 115 controls the inverters 121 and 122 so that the excessive power generated by the electric swing motor 30 is not supplied to the assist motor 12 by the assist stop control means 115b.

  The routine for performing Step S8 through any one of Step S1 to Step S4 to Step S7 is repeated at a predetermined cycle of several milliseconds. The predetermined period is set so that the processing speed is sufficient for the control of the engine speed R.

  Here, an example of a change in the engine speed R when the control mode is switched between the normal mode and the speed reduction mode according to the operation of the hydraulic excavator 1 will be described with reference to FIG.

  The change in the excess required output ΔW indicated by the broken line 201 (solid line) in FIG. 6A reduces the turning speed of the swing body 3 in a state where the output of the main pump 11a is constant, that is, the estimated output Wp is constant. Obtained when. In order to decelerate the turning speed to an arbitrary speed, the braking torque of the regenerative braking by the electric turning motor 30 rises to a necessary value as time elapses, stabilizes to the necessary value, and then terminates the regenerative braking. Decreases with time. The assist request output Wa changes in conjunction with this braking torque. Since the estimated output Wp is constant this time, the change in the excess required output ΔW is the same as the change in the assist required output Wa. Specifically, after increasing from W1 to W2 over time, the W2 Then, it decreases with time until W1.

  While the turning speed is being reduced to change the excess required output ΔW as shown in FIG. 6A, the engine speed command means 114 is based on the fact that the electric turning motor 30 is in regenerative braking. A command is sent to the fuel injection amount control device 130 for an engine target speed Re that is equal to or higher than the target speed Rc, whereby the engine speed R is controlled to be equal to or higher than Rc.

  In a state where the excessive required output ΔW is equal to or less than the reference excessive required output Wsc, that is, in a period from time 0 to time T1 when the braking torque of regenerative braking by the electric turning motor 30 starts to rise, the assist motor control means 115 is the normal control means 115a. Thus, by controlling the inverters 121 and 122 based on the assist request output Wa, electric power is supplied from the electric turning motor 30 to the assist motor 12, and the engine 10 is assisted by the assist motor 12.

  In parallel with this, the engine speed command means 114 receives the assist request output Wa from the target speed Rt for causing the engine 10 to output the total output Wt of the estimated output Wp and the minimum output Wmin by the normal command means 114a. The engine target rotational speed Re is obtained by subtracting the substantial assisting rotational speed Ra, and this target engine rotational speed Re is commanded to the fuel injection amount control device 130. As a result, the fuel injection amount of the engine 10 is controlled to an amount corresponding to the command for the target engine speed Re. As described above, since the assist request output Wa increases with time in the period from time 0 to time T1, the engine speed command means 114 causes the assist speed Ra corresponding to the increase of the assist request output Wa. Is subtracted from the target rotational speed Rt to obtain the target rotational speed Re for the engine. As a result, the engine rotational speed Re due to fuel injection is decreased by the increase in the assist rotational speed Ra by the assist of the assist motor 12, and as a result, the engine speed is shown as a broken line 202 (solid line) in FIG. 6B. The number R is stable to R1 (R1> Rc). Since the period from time 0 to time T1 is always “ΔW ≦ Wsc, R <Rlim”, the control switching unit 117 holds the control mode in the normal mode.

  When the time T1 elapses, that is, when the rising of the braking torque of the regenerative braking of the electric swing motor 30 has passed halfway, the excessive required output ΔW exceeds the reference excessive required output Wsc with the engine speed R being R1, that is, “ ΔW> Wsc, R ≧ Rc ”, and the control switching unit 117 switches the control mode from the normal mode to the rotation speed reduction mode. As a result, the engine speed command means 114 determines the engine target speed Re to be the low speed Rl and gives a command to the fuel injection amount control device 130 by the speed drop command means 114b. As a result, the fuel injection amount decreases stepwise, and the engine speed R decreases from R1 to R2 accordingly.

  Even after the decrease in the engine speed R, the rotation assist of the engine 10 by supplying electric power from the electric turning motor 30 to the assist motor 12 is continuously performed. It rises from R2 and finally reaches R3. The engine speed R3 is lower than the upper limit speed Rlim.

  Thereafter, when the excess required output ΔW starts to decrease from W2, that is, when the assist required output Wa starts to decrease, the assisting rotational speed Ra also starts to decrease. At this time, the control mode is the rotational speed reduction mode, and the target rotational speed Re is held at the low rotational speed Rl, that is, the engine rotational speed Re obtained only by fuel injection is stable at Rl. As the assist rotational speed Ra corresponding to the assist request output Wa decreases, the engine rotational speed R (R = Ra + Re) also starts to decrease. When the excessive required output ΔW decreases to the reference excessive required output Wsc, the engine speed R decreases to R1, thereby the states of the assist required output ΔW and the engine speed R are “ΔW ≦ Wsc, R <Rlim”. Return to the state. Along with this, the control switching means 117 returns the control mode from the rotation speed reduction mode to the normal mode. That is, the engine speed Re according to the fuel injection amount increases as the assisting speed Ra decreases. As a result, the engine speed R (R = Ra + Re) is represented by a broken line 202 (solid line) in FIG. 6B. As shown, it is stable at R1 (R1> Rc).

  It should be noted that the state where “ΔW ≦ Wsc” (including ΔW <0 or less) is likely to be a state in which the front working device 6 is working, that is, from the main pump 11a to the boom cylinder 7a, arm cylinder 8a, bucket cylinder 9a. This is a case where regenerative braking is performed by the electric swing motor 30 in a state where pressure oil is supplied to any or all of them. Further, when the total output Wt of the estimated output Wp and the minimum output Wmin is larger than the assist request output Wa, the control mode is the normal mode. Conversely, the state where “ΔW ≧ Wsc” tends to be satisfied is a case where regenerative braking is performed by the electric swing motor 30 in a state where the front working device 6 is not working. In this case, since the output required for the engine 10 is the minimum output Wmin, that is, the minimum output for operating the engine 10 against the minimum load applied to the engine 10, an output for assisting the rotation of the engine 10 by the assist motor 12 is provided. Hard to generate.

  According to the drive control apparatus 100 according to the first embodiment, the following effects can be obtained.

  In the drive control apparatus 100 according to the first embodiment, the condition for selecting the rotation speed reduction mode as the control mode is that the excessive required output WΔ is larger than the reference excessive required output Wsc and is detected by the engine speed sensor 131. The engine speed R is set to be equal to or higher than the reference speed Rc, and the reference speed Rc is set in advance as the minimum engine speed required for the work of the hydraulic excavator 1. The rotation speed decrease command means 114b of the rotation speed control means 114 instructs the fuel injection amount control device 130 to set the fuel injection amount of the engine 10 with a predetermined low rotation speed Rl lower than the reference rotation speed Rc as a target rotation speed. As a result, the engine speed decreases stepwise to the low speed Rl. As a result, when the assist motor 12 assists the rotation of the engine 10 by consuming excessive power to the battery 13 out of the power generated by the electric turning motor 30 different from the assist motor 12, the engine rotation It is possible to prevent the number from becoming excessive. As a result, it is possible to prevent the engine 10 from being subjected to an excessive load that approaches or exceeds the physical limit.

  Although the drive control device 100 according to the first embodiment described above includes the battery 13 as the power storage device, the power storage device in the present invention is not limited to the battery, and is a capacitor instead of the battery 13. It may be both a battery and a capacitor.

[Second Embodiment]
A drive control device for a work machine according to a second embodiment of the present invention will be described with reference to FIG.

  In the drive control apparatus according to the second embodiment, the engine speed command means 114 has only the function as the normal command means 114a of the normal command means 114a and the rotation speed decrease command means 114b in the first embodiment, The fuel injection amount control device 130 is provided with a small injection amount processing means 130a instead of the rotation speed lowering instruction means 114b. The small injection amount processing means 130a is for causing the fuel injection device of the engine 10 to inject fuel with a predetermined small injection amount when the control mode is switched to the rotation speed reduction mode by the control switching means 117. The predetermined small injection amount is set to a fuel injection amount that is injected by the fuel injection device of the engine 10 when the fuel injection amount control device 130 is instructed by the engine target rotation speed Re equivalent to the low rotation speed Rl. Yes. That is, in the drive control device 100 according to the second embodiment, the normal means for controlling the engine speed in the normal mode is configured by the engine speed command means 114 and the fuel injection amount control device 130. The engine speed reduction means for controlling the engine speed in the engine speed reduction mode includes a small injection amount processing means 130 a of the fuel injection amount control device 130.

  According to the drive control apparatus according to the second embodiment, the condition for selecting the rotation speed decrease mode as the control mode is that the excessive required output WΔ is larger than the reference excessive required output Wsc and is detected by the engine speed sensor 131. The engine speed R is set to be equal to or higher than the reference engine speed Rc, and the reference engine speed Rc is set in advance as the lowest engine speed required for the work of the hydraulic excavator 1. The small amount injection processing means 130a of the injection amount control device 130 reduces the fuel injection amount corresponding to the low rotational speed Rl and decreases the engine rotational speed step by step to the low rotational speed Rl. As a result, when the assist motor 12 assists the rotation of the engine 10 by consuming excessive power to the battery 13 out of the power generated by the electric turning motor 30 different from the assist motor 12, the engine rotation It is possible to prevent the number from becoming excessive. As a result, it is possible to prevent the engine 10 from being subjected to an excessive load that approaches or exceeds the physical limit.

  In particular, according to the drive control apparatus according to the second embodiment, it is possible to omit the process of instructing the fuel injection amount control device 130 from the engine speed command means 114 to the fuel injection amount control device 130 as the engine target speed Re. As a result, the engine speed R can be lowered from R1 to R2 more rapidly than in the first embodiment. That is, overspeeding of the engine 10 can be avoided more quickly than in the first embodiment.

1 Excavator (work machine)
3 Revolving body (movable part)
7a Boom cylinder (hydraulic actuator)
8a Arm cylinder (hydraulic actuator)
9a Bucket cylinder (hydraulic actuator)
10 Engine 11a Main pump 12 Assist motor (first motor generator)
20 Left travel motor (hydraulic actuator)
21 Right travel motor (hydraulic actuator)
30 Electric swing motor (second motor generator)
13 Battery (power storage device)
DESCRIPTION OF SYMBOLS 100 Drive control apparatus 110 Car body controller 111 Turning motor control means 112 Pump output estimation means 113 Target rotation speed calculation means 114 Engine rotation speed command means (engine control means)
114a Normal command means (normal means)
114b Speed reduction command means (speed reduction means)
115 Assist motor control means (assist control means)
115a Normal control means 115b Assist stop control means 116 Assist request generation means 117 Control switching means 117a Determination table 130 Fuel injection amount control device (engine control means, passage means, rotation speed reduction means)
130a Small injection amount processing means (rotational speed lowering means)
131 engine speed sensor (engine speed detection means)
140 Upper limit rotational speed input device (upper limit rotational speed command means)

Claims (5)

An engine comprising an internal combustion engine; a hydraulic pump driven by the engine; a hydraulic actuator driven by pressure oil discharged from the hydraulic pump; and a first motor generator coupled to the engine to be able to transmit A second motor / generator that drives a predetermined movable part of the work machine and performs regenerative braking on the movable part, power generated by the first motor / generator, and generated by the second motor / generator Of the electric power generated by the second motor / generator and the electric power generated by the second motor / generator is supplied to the first motor / generator with the assistance of the rotation of the engine. A drive control device for a work machine comprising assist control means for causing
Upper limit rotational speed command means for commanding the rated rotational speed of the engine as the upper limit rotational speed of the engine;
An engine speed detecting means for detecting the engine speed per unit time;
Pump output estimating means for calculating an estimated output of the hydraulic pump;
Assist request generation means for calculating excess power as an assist request output for the power storage device among the power generated by the second motor generator;
Target engine speed calculating means for calculating a target engine speed of the engine based on the estimated output;
Engine control means for controlling the fuel injection amount of the engine based on the target rotational speed;
For controlling the engine and the first motor-generator based on an excessive request output obtained by subtracting the estimated output from the assist request output and a detected value of the engine speed by the engine speed detection means. Control switching means for switching the control mode,
The control switching means is
When the excessive required output is equal to or lower than a predetermined reference excessive required output and the engine speed detected by the engine speed detecting means is lower than the upper limit speed, the normal mode is selected as the control mode,
The excessive required output is larger than the reference excessive required output, and the engine rotational speed detected by the engine rotational speed detecting means is preset as the minimum engine rotational speed required for work of a work machine. When the speed exceeds the reference speed, select the speed drop mode as the control mode,
The engine control means,
A normal means for controlling the engine speed in the normal mode; and a speed drop means for controlling the engine speed in the speed drop mode;
The normal means obtains a target engine speed by subtracting from the target engine speed an assist engine speed obtained by assisting the engine by the first motor generator based on the assist request output. The fuel injection amount is controlled based on the target engine speed,
The drive speed control device for a work machine, wherein the rotational speed lowering unit reduces the fuel injection amount of the engine stepwise to a fuel injection amount corresponding to a predetermined low rotational speed lower than the reference rotational speed. The drive control device for a work machine according to claim 1,
The engine control means includes a fuel injection amount control device that controls a fuel injection amount of the engine, and an engine rotation speed command means that commands the engine target rotation speed to the fuel injection amount control device,
Rotational speed command means for said engine comprises a normal command means constituting the normal means together with the fuel injection amount control device, and a rotational speed drop command means constituting the rotational speed drop unit together with the fuel injection amount control device ,
The normal command means commands the target injection speed for the engine obtained by subtracting the assist rotational speed from the target rotational speed to the fuel injection amount control device,
The drive speed control device for a work machine, wherein the rotation speed drop command means commands the fuel injection amount control device to use the low rotation speed as a target engine rotation speed. The drive control device for a work machine according to claim 1,
The engine control means includes a fuel injection amount control device that controls a fuel injection amount of the engine, and an engine rotation speed command means that commands the engine target rotation speed to the fuel injection amount control device,
The engine speed command means constitutes the normal means together with the fuel injection amount control device,
The fuel injection amount control device includes a small injection quantity processing means as poor stage later said rotation speed,
The small injection amount processing means controls the fuel injection amount of the engine to the amount corresponding to the low rotational speed. In the drive control apparatus of the working machine of any one of Claims 1-3,
The control switching means detects the engine speed detection means when the excess demand output is equal to or lower than a predetermined reference excess demand output after the control mode is shifted from the normal mode to the speed reduction mode. A drive control device for a work machine, wherein the control mode is returned to the normal mode when the engine speed is lower than the upper limit speed. In the drive control apparatus of the working machine of any one of Claims 1-4,
The Assist control unit performs determination the assistance request output is whether higher than a predetermined reference required output, if the result of this determination is true, the reference request outputted from the assist request output A drive control device for a work machine, wherein the assist request output is corrected by subtraction.

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