JP6336854B2 - Hydraulic pump drive system - Google Patents

Description

  The present invention relates to a drive system for a hydraulic pump that rotates a rotary shaft by an engine and an electric motor to drive a hydraulic pump.

  Construction machines and the like include a hydraulic pump, and a hydraulic actuator such as a hydraulic cylinder is operated by pressure oil discharged from the hydraulic pump to move an arm, a boom, and the like. The hydraulic pump is connected to the engine and the electric motor via a rotating shaft, and is rotated by the engine and the electric motor. As a construction machine configured in this way, for example, a construction machine disclosed in Patent Document 1 is known.

  In the construction machine disclosed in Patent Document 1, the engine is controlled by the control device so that the rotational speed becomes the rotational speed command. However, when the hydraulic pump is loaded, such as when a hydraulic actuator is driven, the rotational speed decreases. . When the rotational speed of the engine decreases and the deviation between the rotational speed and the rotational speed command increases, the control device moves the electric motor to assist the engine. Thereby, the engine speed is kept constant (specifically, the engine speed command). Further, the control device reduces the amount of charge of the power storage device that supplies electric power to the motor after the motor is operated, and increases the deviation between the charge amount and the charge amount command, while limiting the rate of time change and the target torque of the engine Is supposed to increase.

International Publication No. 2013/031525

  In the construction machine of Patent Document 1, since the engine and the electric motor are coupled, when the engine load torque increases and the rotation speed decreases, the deviation between the rotation speed and the rotation speed command increases. Then, the control device controls the electric motor in accordance with the deviation between the rotational speed and the rotational speed command, and assists the engine with the electric motor so as to keep the engine rotational speed constant.

  In this case, the torque adjustment by the electric motor is not performed until the deviation actually occurs (in other words, the torque adjustment by the electric motor is performed after the deviation is actually calculated). When the number decreases rapidly, the torque may not be adjusted immediately and the rotational speed may decrease excessively.

  Therefore, an object of the present invention is to provide an operating system for a hydraulic pump that can be assisted by an electric motor so that the rotational speed of the engine does not decrease excessively.

  The drive system for a hydraulic pump according to the present invention includes an engine that rotationally drives a rotary shaft of the hydraulic pump, an electric motor that can assist the rotational drive of the rotary shaft, and a rotational speed for detecting the rotational speed of the rotary shaft. A control device for controlling the movement of the electric motor, the control device comprising: a target fuel injection amount calculation unit; an injection amount restriction unit; an actual torque calculation unit; a target torque calculation unit; and a differential torque calculation And a drive control unit, wherein the target fuel injection amount calculation unit calculates a target fuel injection amount based on the actual rotational speed and the target rotational speed, and the injection amount restriction unit includes the target fuel injection amount When calculating the actual fuel injection amount based on the fuel injection amount, it has a function of increasing the actual fuel injection amount step by step up to the target fuel injection amount. Determine the actual fuel injection amount so that it is below the specified value The actual torque calculation unit calculates the actual torque output from the engine based on the actual rotation speed detected by the rotation speed sensor and the actual fuel injection amount determined by the injection amount limiting unit, The target torque calculation unit calculates a target torque to be applied to the rotating shaft based on the actual rotation number detected by the rotation number sensor and the target fuel injection amount calculated by the target fuel injection amount calculation unit. The differential torque calculator calculates a differential torque that is insufficient in the actual torque calculated by the actual torque calculator with respect to the target torque calculated by the target torque calculator, and the drive controller The movement of the electric motor is controlled to output the differential torque.

  According to the present invention, the output torque of the engine becomes insufficient by limiting the time change rate of the actual fuel injection amount, but the insufficient output torque is calculated in advance as a differential torque. By outputting this differential torque from the electric motor, the torque output from the entire hydraulic pump drive system can be brought close to the target torque even if the actual fuel injection amount is limited, and the torque output from the entire hydraulic pump drive system can be reduced. The decrease can be suppressed. In this way, in the hydraulic pump drive system, the amount of change in output torque due to the time rate of change being limited is estimated in advance, and the shortage of torque is output to the motor to deal with it. It is possible to suppress an excessive decrease in the engine speed as compared with the case where the torque is adjusted according to the number deviation. As a result, it is possible to suppress a decrease in fuel consumption of the engine due to an excessive decrease in the rotational speed.

  In the above invention, the injection amount restriction unit may use the target fuel injection amount as the actual fuel injection amount when the target fuel injection amount is decreasing.

  According to the present invention, the actual fuel injection amount is calculated by the injection amount limiting unit, and the target fuel injection amount is set as the actual fuel injection amount when the target fuel injection amount is decreasing. As a result, the actual torque and the target torque calculated by each of the actual torque calculation unit and the target torque calculation unit are the same or substantially the same, and the differential torque calculated by the differential torque calculation unit is zero. Therefore, it is possible to eliminate regeneration of the electric motor using the output torque of the engine, and it is possible to improve the fuel consumption of the engine.

  In the above invention, when calculating the actual fuel injection amount based on the target fuel injection amount, when the target fuel injection amount is increasing, the injection amount limiting unit changes the proportion in proportion to the elapsed time. The actual fuel injection amount may be increased stepwise based on a change rule.

  If the said structure is followed, it can suppress that an actual fuel injection amount increases rapidly. Thereby, it can suppress that the combustion state of an engine deteriorates, it can suppress that an engine output torque falls, and can improve the fuel consumption of an engine.

  In the above invention, when the target fuel injection amount is increased when the actual fuel injection amount is calculated on the basis of the target fuel injection amount, the injection amount limiting unit delays a primary delay with respect to an elapsed time. The actual fuel injection amount may be changed stepwise based on a change rule.

  If the said structure is followed, it can suppress that an actual fuel injection amount increases rapidly. Thereby, it can suppress that the combustion state of an engine deteriorates, it can suppress that an engine output torque falls, and can improve the fuel consumption of an engine.

  In the above invention, the control device includes a torque change estimating unit and a change torque calculating unit, and the torque change estimating unit calculates the actual fuel injection amount and the actual rotation calculated by the injection amount limiting unit. The change torque calculation unit calculates a change torque to be assisted based on the change amount of the output torque calculated by the torque change estimation unit. The drive control unit may control the movement of the electric motor so as to output a torque obtained by adding the change torque to the differential torque.

  If the said structure is followed, the variation | change_quantity (decrease amount) of the output torque resulting from the change of actual fuel injection amount will be estimated in advance, and the change torque which should be assisted will be calculated based on the estimated variation | change_quantity. The calculated change torque is output from the electric motor with differential torque added. In this way, the output torque of the engine can be assisted by the electric motor, and when the output torque changes, the change can be assisted by the electric motor. For example, even when the actual fuel injection amount suddenly increases when the hydraulic pump is loaded and the combustion state deteriorates, the above configuration causes the output torque due to the change in the actual fuel injection amount. It is possible to prevent a decrease and an excessive decrease in the rotational speed. Thereby, the fall of operativity by the fall of the hydraulic pump discharge flow volume accompanying rotation number falling too much can be suppressed.

  In the above invention, the torque change estimation unit estimates a rate of change of the output torque per unit revolution number of the engine based on the actual fuel injection amount, and the actual torque calculated by the actual torque calculation unit The amount of change in the output torque may be calculated based on the rate of change.

  In the engine, the change in the actual fuel injection amount affects the combustion state not only at the time of combustion immediately after supply but also over several subsequent combustions. That is, the influence on the combustion state due to the change in the actual fuel injection amount is reduced by passing the number of combustions instead of the time, and the combustion state of the engine changes according to the number of combustions (that is, the number of revolutions) rather than the time. .

  According to the above configuration, the rate of change of the output torque for each unit revolution of the engine with respect to the change of the actual fuel injection amount is calculated, and the amount of change of the output torque for each unit revolution is calculated based on this rate of change and the actual torque. It can be calculated. Thus, since the amount of change in output torque is calculated not in time units but in rotation speed units, it is possible to estimate the decrease in output torque more accurately than in the case of calculation in time units. As a result, the engine can be assisted based on the amount of change in the output torque, so that the engine speed can be prevented from excessively decreasing.

  In the above invention, the torque change estimation unit is a pseudo-differential calculation unit including a first-order lag element whose time constant can be changed, and the first-order lag element according to the rotation speed of the rotating shaft detected by the rotation speed sensor. A time constant calculating unit for changing a constant, and calculating a rate of change of the actual fuel injection amount per unit rotational speed of the engine using pseudo-differentiation, and the engine based on the rate of change of the actual fuel injection amount The amount of change in the output torque per unit rotational speed may be estimated.

  According to the above configuration, it is possible to practically calculate the rate of change of the output torque per unit rotational speed by using a pseudo-derivative including a first-order lag element and changing the first-order lag element according to the actual rotational speed. it can.

  In the above invention, the change torque calculation unit may set the change torque to zero when the change rate of the actual fuel injection amount is less than zero.

  According to the above configuration, it is possible to prevent a change torque (assist torque) from being generated from the electric motor when the actual fuel injection amount is decreased to reduce the output torque. As a result, when the output torque of the engine is intentionally reduced, it is possible to prevent wasteful consumption of energy by the electric motor.

  The hydraulic pump drive system according to the present invention includes an engine that rotationally drives the rotary shaft of the hydraulic pump, an electric motor that can assist in the rotational drive of the rotary shaft, and a rotation for detecting the actual rotational speed of the rotary shaft. A control device that controls the movement of the electric motor, and the control device includes an actual fuel injection amount calculation unit, a torque change estimation unit, an assist torque calculation unit, and a drive control unit. The actual fuel injection amount calculation unit calculates an actual fuel injection amount based on the actual rotation speed and the target rotation speed, and the torque change estimation unit calculates the actual fuel injection amount calculation unit by the actual fuel injection amount calculation unit. A change amount of the output torque of the engine is estimated based on the fuel injection amount and the actual rotational speed, and the change torque calculation unit assists based on the change amount of the output torque calculated by the torque change estimation unit. Should change torque Calculated, the drive control unit is for controlling the movement of the electric motor so as to output the change torque.

  According to the above configuration, the change amount (decrease amount) of the output torque due to deterioration of the combustion state of the engine due to the change in the actual fuel injection amount should be estimated in advance, and assisted based on the estimated change amount Calculate the change torque. The calculated change torque is output from the electric motor. Thereby, the output torque of the engine can be assisted by the electric motor, and when the output torque changes, the change can be assisted by the electric motor. For example, even when the target fuel injection amount suddenly increases when the hydraulic pump is loaded and the combustion state becomes unstable, the above configuration causes a decrease in output torque and excessive rotation speed. Can be prevented. Thereby, the fall of operativity by the fall of the discharge flow volume of the hydraulic pump accompanying rotation number falling too much can be suppressed.

  In the above invention, the control device includes an actual torque calculation unit, and the actual torque calculation unit is calculated by the actual rotation speed detected by the rotation speed sensor and the actual fuel injection amount calculation unit. The actual torque output from the engine is calculated based on the injection amount, and the torque change estimation unit estimates the rate of change of the output torque per unit rotational speed of the engine based on the actual fuel injection amount. The change amount of the output torque may be calculated based on the actual torque calculated by the actual torque calculation unit and the change rate.

  According to the above configuration, the change rate of the output torque for each unit speed with respect to the change in the actual fuel injection amount is calculated, and the change amount of the output torque for each unit speed is calculated based on the change rate and the actual torque. can do. As described above, since the amount of change in the output torque is calculated not in time units but in rotation speed units, it is possible to estimate the torque drop more accurately than in the case of calculation in time units. As a result, the engine can be assisted based on the amount of change in the output torque, so that the engine speed can be prevented from excessively decreasing.

  In the above invention, the torque change estimation unit is a pseudo-differential calculation unit including a first-order lag element whose time constant can be changed, and the first-order lag element according to the rotation speed of the rotating shaft detected by the rotation speed sensor. A time constant calculating unit for changing a constant, and calculating a rate of change of the actual fuel injection amount per unit rotational speed of the engine using pseudo-differentiation, and the engine based on the rate of change of the actual fuel injection amount The amount of change in the output torque per unit rotational speed may be estimated.

  According to the above configuration, it is possible to practically calculate the rate of change of the output torque per unit rotational speed by using a pseudo-derivative including a first-order lag element and changing the first-order lag element according to the actual rotational speed. it can.

  ADVANTAGE OF THE INVENTION According to this invention, when a load is applied to a hydraulic pump and rotation speed falls, it can assist with an electric motor so that the rotation speed of an engine may not fall excessively.

1 is a block diagram showing a hydraulic pump drive system according to an embodiment of the present invention. FIG. 2 is a functional block diagram illustrating functions of a control device provided in the hydraulic pump drive system of FIG. 1 as blocks. FIG. 3 is a functional block diagram illustrating a part of the control device of FIG. 2 in more detail. It is a graph which shows the time-dependent change of various values when the hydraulic pump drive system of FIG. 1 is driven. It is a graph which shows the time-dependent change of various values when the hydraulic pump drive system of other embodiment is driven.

  Hereinafter, a hydraulic pump drive system 1 according to an embodiment of the present invention will be described with reference to the drawings. In addition, the concept of the direction used in the following description is used for convenience in description, and does not limit the direction of the configuration of the invention in that direction. Moreover, the hydraulic pump drive system 1 described below is only one embodiment of the present invention. Therefore, the present invention is not limited to the embodiments, and additions, deletions, and changes can be made without departing from the spirit of the invention.

  A construction machine includes various attachments such as a bucket, a loader, a blade, and a hoisting machine, and is moved by a hydraulic actuator such as a hydraulic cylinder or a hydraulic motor (electric oil motor). For example, a hydraulic excavator that is a kind of construction machine includes a bucket, an arm, and a boom, and can perform operations such as excavation while moving these three members. Each of the bucket, arm, and boom is provided with hydraulic cylinders 11-13, and the bucket, arm, and boom are moved by supplying pressure oil to each cylinder 11-13.

  Moreover, the hydraulic excavator has a traveling device, and a revolving body is mounted on the traveling device so as to be capable of turning. A boom is attached to the revolving structure so as to be swingable in the vertical direction. A hydraulic turning motor 14 is attached to the turning body, and the turning body is turned by supplying pressure oil to the turning motor 14. In addition, a hydraulic traveling motor 15 is attached to the traveling device, and the traveling device 15 moves forward or backward by supplying pressure oil to the traveling motor 15. The hydraulic actuators 11 to 15 (that is, the hydraulic cylinders 11 to 13 and the hydraulic motors 14 and 15) are connected to the hydraulic supply device 16, and operate by receiving the supply of pressure oil from the hydraulic supply device 16. Yes.

  The hydraulic pressure supply device 16 includes a hydraulic pump 17 and a control valve 18. The hydraulic pump 17 is a swash plate pump, for example, and has a rotating shaft 17a, and discharges pressure oil by rotating the rotating shaft 17a. The discharged pressure oil is guided to the control valve 18, and the control valve 18 controls the flow of the discharged pressure oil.

  The hydraulic excavator is provided with a plurality of operating tools (for example, operating levers and operating buttons) in association with the hydraulic actuators 11 to 15, and the control valve 18 is operated when the operating tool is operated. Pressure oil is allowed to flow through the hydraulic actuators 11 to 15 corresponding to the operation tool. By flowing the pressure oil in this way, the hydraulic actuators 11 to 15 are operated according to the operation of the operation tool, and the bucket, the arm, the boom, and the like are moved. The rotary shaft 17a of the hydraulic pump 17 is connected to the hydraulic pump drive system 1, and the rotary shaft 17a is driven to rotate by the hydraulic pump drive system 1.

  The hydraulic pump drive system 1 is a hybrid drive system including an engine E and an electric motor 20, and both the engine E and the electric motor 20 are connected to a rotating shaft 17 a of the hydraulic pump 17. The engine E is, for example, a diesel engine having a plurality of cylinders, and a fuel injection device 21 is provided in association with each cylinder. The fuel injection device 21 includes, for example, a fuel pump and an electromagnetic control valve, and injects an amount of fuel corresponding to an input injection command into the combustion chamber of the corresponding cylinder. The engine E burns the fuel injected from the fuel injection device 21 and reciprocates a piston (not shown) to rotate the rotating shaft 17a and discharge the hydraulic oil from the hydraulic pump 17. In the present embodiment, the engine E is a diesel engine. However, the engine E is not necessarily a diesel engine and may be a gasoline engine. The rotating shaft 17a is provided with an electric motor 20 to assist in driving the engine E.

  The electric motor 20 is an AC motor, for example, and is connected to the inverter 22. The inverter 22 which is a driving device is connected to a battery (not shown), and converts a direct current supplied from the battery into an alternating current and supplies the alternating current to the electric motor 20. Further, the inverter 22 supplies an alternating current having a frequency and voltage according to the input torque command to the electric motor 20 so that the torque corresponding to the torque command (assist torque described later) is output from the electric motor 20 to the rotating shaft 17a. It has become.

  A rotation speed sensor 23 is attached to the rotation shaft 17a, and the rotation speed sensor 23 outputs a signal corresponding to the rotation speed of the rotation shaft 17a. The rotation speed sensor 23 is electrically connected to the control device 30 together with the inverter 22 and the electromagnetic control valve of the fuel injection device 21.

  The control device 30 calculates the actual rotational speed of the rotating shaft 17a based on the signal input from the rotational speed sensor 23, and calculates the difference between the calculated actual rotational speed and the target rotational speed. Note that the target rotational speed is a rotational speed that is input from an input means (a dial, a button, a touch panel, or the like) or is set in advance. The control device 30 calculates a target fuel injection amount to be injected from the fuel injection device 21 based on the difference between the actual rotational speed and the target rotational speed. Further, the control device 30 calculates an actual fuel injection amount by a method to be described later based on the target fuel injection amount, and causes the fuel injection device 21 to inject this actual fuel injection amount. The control device 30 calculates the actual rotation speed and the target fuel injection amount at predetermined intervals. Further, the control device 30 assists the engine E by driving the electric motor 20 when only the torque from the engine E is insufficient. Hereinafter, the function of the control device 30 will be described in more detail with reference to FIGS. 2 and 3.

  The control device 30 has a functional part that calculates various values (a first assist torque and a second assist torque described later). If the functional part that calculates various values is divided into blocks, the target fuel injection will be described. An amount calculation unit 38, a target torque calculation unit 31, an injection amount restriction unit 32, an actual torque calculation unit 33, and a first assist torque calculation unit 34 are provided. The target fuel injection amount calculation unit 38 calculates a target fuel injection amount to be injected from the fuel injection device 21 based on the difference between the actual rotational speed and the target rotational speed. The target torque calculator 31 calculates the target torque using the target torque map. The target torque map is a map in which the target torque to be output by the entire hydraulic pump drive system 1 is associated with the target fuel injection amount and the actual rotational speed, and the target torque calculator 31 calculates the calculated target fuel injection amount. The target torque is calculated from the target torque map based on the actual rotational speed. The target fuel injection amount calculated by the target fuel injection amount calculation unit 38 is used for the injection amount restriction unit 32 to calculate the actual fuel injection amount to be actually injected by the fuel injection device 21.

  The injection amount limiting unit 32 (actual fuel injection amount calculation unit) has a rate limit function with an increase rate limitation and without a decrease rate limitation, and the actual fuel injection amount based on the target fuel injection amount by this rate limit function. Is calculated. More specifically, when the target fuel injection amount increases and the increase rate of the target fuel injection amount exceeds a predetermined value, the injection amount limiting unit 32 sets the change rate or the change amount based on a predetermined change rule. The actual fuel injection amount is changed stepwise up to the target fuel injection amount while limiting. On the other hand, when the target fuel injection amount decreases, the injection amount limiting unit 32 sets the target fuel injection amount as the actual fuel injection amount without limiting the reduction rate.

  In the present embodiment, the injection amount restriction unit 32 internally holds (that is, stores) the target fuel injection amount calculated by the target fuel injection amount calculation unit 38, and calculates immediately after the held target fuel injection amount. The target fuel injection amount thus made is compared. When the target fuel injection amount immediately after the held target fuel injection amount is small, that is, when the target fuel injection amount is decreasing, the target fuel injection amount is calculated as the actual fuel injection amount. On the other hand, when the target fuel injection amount immediately after the held target fuel injection amount is large, that is, when the target fuel injection amount is increasing, the rate of increase (the difference between the two target fuel injection amounts in this embodiment) is It is determined whether or not a predetermined value is exceeded. If it is less than the predetermined value, the target fuel injection amount is calculated as the actual fuel injection amount. On the other hand, when it exceeds the predetermined value, the actual fuel injection amount is gradually increased to the target fuel injection amount while limiting the increase rate based on a change rule that sets the increase rate to a predetermined value or less. That is, when it exceeds the predetermined value, the actual fuel injection amount is increased stepwise to the target fuel injection amount in proportion to the time based on a proportional constant equal to or less than the predetermined value. The injection amount limiting unit 32 may be a filter, and may increase the target fuel injection amount based on, for example, a transfer function having a first-order lag element (that is, a lag element). The actual fuel injection amount calculated in this way is used together with the actual rotational speed in order to calculate the actual torque by the actual torque calculation unit 33.

  The actual torque calculator 33 calculates an actual torque using an actual torque map. The actual torque is an output torque output from the engine E when the fuel injection device 21 injects the actual fuel injection amount into the engine E. The actual torque map is a map in which the actual torque is associated with the actual fuel injection amount and the actual rotation speed, and the actual torque calculation unit 33 calculates the actual torque map based on the calculated actual fuel injection amount and the actual rotation speed. The actual torque is calculated. In the present embodiment, the same map is used as the actual torque map and the target torque map. The calculated actual torque is used together with the target torque so that the first assist torque calculator 34 calculates the first assist torque to be output by the electric motor 20.

  The first assist torque calculation unit 34 (difference torque calculation unit) is a shortage torque obtained by subtracting the actual torque from the target torque based on the actual torque calculated from one target fuel injection amount and the target torque. One assist torque (difference torque) is calculated. More specifically, the first assist torque calculator 34 subtracts the actual torque from the target torque, and calculates the first assist torque that is insufficient to generate the target torque from the hydraulic pump drive system 1.

  Thus, the control device 30 is configured to limit the increase rate of the actual fuel injection amount when the target fuel injection amount suddenly increases. By limiting the increase rate in this way, it is possible to prevent deterioration of the combustion state of the engine E due to a rapid increase in the target fuel injection amount, and to improve fuel efficiency. On the other hand, since the actual torque actually output becomes smaller than the target torque by being limited, that is, insufficient torque is generated, the first assist torque corresponding to the shortage is calculated in order to cause the motor 20 to output the shortage. doing.

  Further, in the hydraulic pump drive system 1, the output torque of the engine E is reduced by limiting the increase rate of the actual fuel injection amount. However, the control device 30 has a function of estimating the reduced output torque and calculating the second assist torque (change torque) so as to supplement the reduced output torque with the electric motor 20. The control device 30 includes a torque change estimation unit 35, a second assist torque calculation unit 36, and a drive control unit 37 in order to calculate the second assist torque.

  The torque change estimator 35 estimates the amount of change in torque output from the engine E based on the calculated actual rotational speed and actual fuel injection amount. In the engine E, the combustion state becomes unstable due to a change in the actual fuel injection amount, and a response delay occurs in the output torque. In addition, the combustion state of the engine E changes every revolution (in the case of a four-stroke engine, every cycle of intake-compression-expansion-exhaust), and the unstable state of the combustion state improves as the number of combustion passes. Is done. Accordingly, as the actual rotational speed is larger, the number of combustions per unit time is increased, so that the instability of the combustion state of the engine E is improved more quickly, and the decrease in the torque of the engine E is reduced.

  In view of the characteristics of the output torque of the engine E that the combustion state changes every rotation, the torque change estimation unit 35 calculates a decrease in the output torque at every unit rotation speed (preferably every rotation) of the engine E. It is supposed to be. In the present embodiment, the torque change estimating unit 35 numerically models the engine E using a transfer function including a pseudo-derivative described later to estimate the change in the output torque of the engine E, and further includes a first-order lag element included in the pseudo-differential. The time constant is changed according to the actual rotational speed. Thereby, it is possible to artificially calculate the output torque drop for each unit rotation speed. As a result, the higher the actual rotational speed, the faster the combustion state of the engine E improves and the torque reduction is suppressed, and the smaller the actual rotational speed, the slower the improvement of the combustion state of the engine E and the greater the torque reduction. Be considered. That is, the output torque characteristic of the engine E in which the response delay of the torque changes according to the actual rotational speed can be estimated by the above-described transfer function. The torque change estimator 35 that estimates the amount of change in the output torque will be described in more detail below with reference to FIG. 3 in addition to FIG.

  The torque change estimator 35 includes a time constant calculator 41, a pseudo-differential calculator 42, a torque change coefficient calculator 44, a torque change rate calculator 45, and a correction coefficient as functional parts for estimating a change in output torque. A calculation unit 46 and a torque change amount calculation unit 47 are provided. The time constant calculation unit 41 calculates a time constant from the actual rotational speed calculated by the control device 30 using the time constant map. In the present embodiment, the time constant map is a map in which the time constant is associated with the actual rotation. The correspondence between the time constant of the time constant map and the actual rotation is set based on data obtained from experiments and the like. The displacement of the engine E, accessories (supercharger, EGR, etc.), and structure ( It depends on the pipe diameter and length. That is, the correspondence is different for each model of the engine E, and is set for each model of the engine E with reference to the experimental result. The correspondence relationship may be set not only for each model but also for each individual. The time constant calculated by the time constant calculating unit 41 is used together with the actual fuel injection amount by the pseudo-differential calculating unit 42 in order to calculate a differential value of the actual fuel injection amount.

The pseudo-differential calculation unit 42 calculates a differential value of the actual fuel injection amount by a transfer function obtained by numerically modeling the engine E. In the engine E, the fuel injection amount corresponds to the torque, and the differential value of the actual fuel injection amount (corresponding to the rate of change of the actual fuel injection amount per unit revolution) corresponds to the rate of change of the torque. ing. The pseudo differential operation unit 42 will be described in more detail. The transfer function of the pseudo differential operation unit 42 includes a pseudo differential (also referred to as incomplete differentiation) including a first-order lag element. A differential value of the actual fuel injection amount is calculated using this transfer function. In the present embodiment, the pseudo-differentiation, the Laplace variable and s, the differential gain and T _D, when the constant is T time, represented by the following formula (1).

  Thus, by calculating the differential value of the actual fuel injection amount by the pseudo differential including the first-order lag element, a value corresponding to the rate of change of the output torque considering the response delay due to the deterioration of the combustion state (that is, the actual fuel injection) The differential value of the quantity is calculated. Further, the time constant calculated by the time constant calculation unit 41 is used as the time constant T of the first-order lag element included in the pseudo differentiation. That is, the pseudo-differential calculation unit 42 calculates the differential value of the actual fuel injection amount by changing the time constant every time it is calculated. Thus, by calculating the time constant based on the actual rotational speed and changing it every time it is calculated, the rate of change of the output torque for each unit rotational speed (preferably for each rotational speed) is simulated. It can be calculated. The differential value of the actual fuel injection amount calculated in this way corresponds to the rate of change per unit rotational speed of the output torque of the engine E, and the torque change coefficient described later is calculated by the torque change coefficient calculating unit 44. Used for.

  The torque change coefficient calculator 44 calculates a torque change coefficient based on the differential value of the actual fuel injection amount calculated by the pseudo-differential calculator 42. The torque change coefficient is a coefficient indicating how much the torque changes with respect to the actual torque. The torque change coefficient calculating unit 44 first calculates the absolute value of the differential value of the actual fuel injection amount, and then uses the torque change coefficient map 44a shown in FIG. 3 to change the torque change from the absolute value of the differential value of the actual fuel injection amount. Calculate the coefficient. The torque change coefficient map 44a is a map in which the absolute value of the differential value of the actual fuel injection amount is associated with the torque change coefficient. For example, the torque change coefficient map 44a is set so that the torque change coefficient increases as the absolute value of the differential value increases. Has been. In the present embodiment, the correspondence between the absolute value of the differential value of the actual fuel injection amount of the torque change coefficient map 44a and the torque change coefficient is set based on data obtained from experiments or the like, and the time constant map and Similarly, it is set for each model of the engine E. The correspondence relationship between the absolute value of the differential value of the actual fuel injection amount and the torque change coefficient is not necessarily the correspondence relationship as shown in FIG. The torque change coefficient calculation unit 44 calculates a torque change coefficient based on the torque change coefficient map 44a and the absolute value of the differential value of the actual fuel injection amount, and the calculated torque change coefficient indicates the torque change rate as the torque change rate. It is used for calculation by the calculation unit 45.

  The rate of change in torque is the ratio of torque that changes (specifically decreases) as the combustion state deteriorates, etc., relative to the actual torque that is output when fuel of the actual fuel injection amount is injected into the engine E. This is the value shown. The torque change coefficient and the torque change rate basically correspond to each other, but the torque change coefficient is a value set so as to be uniquely derived from the absolute value of the differential value of the actual fuel injection amount. On the other hand, the torque change rate takes into account not only the absolute value of the differential value of the actual fuel injection amount (that is, the torque change coefficient) but also the effects of the actual rotational speed and the actual fuel injection amount. For example, when the engine E has an exhaust turbo function, in the low speed range, the intake air delay increases due to the turbo, and the output torque decreases. In consideration of such a phenomenon, the torque change rate is corrected by the torque change coefficient calculated by the torque change coefficient calculating unit 44, and the correction coefficient for correction is calculated by the correction coefficient calculating unit 46. doing.

  The correction coefficient calculation unit 46 calculates a correction coefficient based on the actual rotational speed calculated by the control device 30 and the actual fuel injection amount calculated by the injection amount limiting unit 32. The correction coefficient is a coefficient for correcting the torque change coefficient calculated by the torque change coefficient calculating unit 44 according to the actual rotational speed and the actual fuel injection amount. More specifically, the correction coefficient calculator 46 calculates the first correction coefficient from the actual rotational speed using the first correction coefficient map 46a as shown in FIG. 3, and the second correction coefficient as shown in FIG. A second correction coefficient is calculated from the actual fuel injection amount using the map 46b. The first correction coefficient map 46a is a map in which the actual rotational speed and the first correction coefficient are associated with each other, and the second correction coefficient map 46b is in association with the actual fuel injection amount and the second correction coefficient. It is a map. In each of the correction coefficient maps 46a and 46b, for example, the correction coefficient is set to be smaller as the actual rotational speed and the actual fuel injection amount are increased.

  The two correction coefficient maps 46a and 46b are set based on data obtained from experiments or the like, and are different for each model of the engine E as in the other maps. Further, each of the correspondence relationship between the actual rotational speed and the first correction coefficient and the correspondence relationship between the actual fuel injection amount and the second correction coefficient is not necessarily the correspondence relationship as shown in FIG. Further, the correction coefficient calculator 46 multiplies the calculated first and second correction coefficients by the correction coefficient multiplier 46c to calculate a torque correction coefficient. The calculated torque correction coefficient is used together with the torque change coefficient in order to calculate the torque change rate by the torque change rate calculating unit 45.

  The torque change rate calculation unit 45 calculates a torque change rate based on the torque change coefficient calculated by the torque change coefficient calculation unit 44 and the correction coefficient calculated by the correction coefficient calculation unit 46. The torque change rate is a value indicating the ratio of torque that changes (increases or decreases) with respect to the actual torque as described above. The torque change rate calculating unit 45 calculates the torque change rate by multiplying the calculated torque change coefficient and the correction coefficient. The calculated torque change coefficient is used together with the actual torque in order to calculate the torque change amount by the torque change amount calculation unit 47.

  The torque change amount calculation unit 47 is based on the torque change rate calculated by the torque change rate calculation unit 45 and the actual torque calculated by the actual torque calculation unit 33, and the torque of the engine E caused by the change in the actual fuel injection amount. The amount of change is calculated. The amount of change in torque is the amount of change in torque that changes according to the combustion state of the engine E when the actual fuel injection amount calculated by the injection amount restriction unit 32 is injected into the engine E (that is, the amount of decrease or increase in torque). ). The torque change amount calculation unit 47 multiplies the torque change rate and the actual torque calculation unit 33 to calculate the torque change amount. The torque change estimation unit 35 estimates the torque change amount in this way. The estimated torque change amount is used for calculating the second assist torque by the second assist torque calculator 36.

  The second assist torque calculation unit 36 (change torque calculation unit) is a second torque corresponding to the shortage of torque to compensate for the shortage of torque that has decreased with the change in the actual fuel injection amount with the output torque of the electric motor 20. Assist torque (change torque) is calculated. The calculation method will be described in detail. The second assist torque calculator 36 first determines whether or not the differential value of the actual fuel injection amount calculated by the pseudo-differential calculator 42 is less than 0 (zero). If it is determined that the differential value of the actual fuel injection amount is less than zero, the second assist torque calculator 36 selects zero as the multiplication coefficient. When it is determined that the differential value of the actual fuel injection amount is equal to or greater than zero, the second assist torque calculation unit 36 selects a predetermined value (in this embodiment, predetermined value = 1) as a multiplication coefficient. Further, the second assist torque calculator 36 multiplies the multiplication coefficient by the torque change amount and calculates the multiplication result as the second assist torque. Accordingly, when the differential value is less than zero, the second assist torque is zero, and when the differential value is greater than or equal to zero, the second assist torque is a torque change amount. The second assist torque calculated in this way is used together with the first assist torque so that the drive control unit 37 calculates the assist torque to be output from the electric motor 20.

  The drive control unit 37 calculates assist torque to be output from the electric motor 20 based on the first assist torque and the second assist torque. That is, the drive control unit 37 calculates the assist torque by adding the first assist torque and the second assist torque. Further, the drive control unit 37 controls the movement of the inverter 22 so that the electric motor 20 outputs an assist torque.

  The control device 30 configured in this way causes the electric motor when the load on the hydraulic pump 17 increases and the rotational speed of the engine E decreases, and when the target fuel injection amount of the engine E increases to compensate for the decreased rotational speed. 20 is driven to assist the engine E. Hereinafter, the movement of the hydraulic pump drive system 1 when the load of the hydraulic pump 17 is increased by operating any of the hydraulic actuators 11 to 15 will be described with reference to the graph of FIG. In FIG. 4, the pump load (load of the hydraulic pump 17), engine speed (actual speed), target fuel injection amount, actual fuel injection amount, first assist torque (differential torque), The torque change coefficient, the second assist torque (change torque), and the change over time of the assist torque are shown. In FIG. 4, the horizontal axis represents time, and the vertical axis represents various values.

  When the operation tool is operated and the control valve 18 is activated, the hydraulic pump 17 is switched from the unload state to the on-load state, and a large load acts on the hydraulic pump 17 (see time t1 in the pump load graph of FIG. 4). ). When the load on the hydraulic pump 17 increases, the actual rotational speed of the engine E becomes lower than the target rotational speed, and a difference occurs between the actual rotational speed of the engine E and the target rotational speed. Then, the target fuel injection amount calculation unit 38 calculates the target fuel injection amount from the difference between the actual rotation speed and the target rotation speed, and the injection amount restriction unit 32 of the control device 30 sets the calculated target fuel injection amount. Based on this, the actual fuel injection amount is calculated. Since the increase rate (or increase amount) of the target fuel injection amount is equal to or greater than a predetermined value, the injection amount limiting unit 32 limits the actual fuel injection amount, and the actual fuel injection amount is proportional to the time until the target fuel injection amount. (See times t1 to t2 in the graph of actual fuel injection amount in FIG. 4).

  The actual fuel injection amount calculated by the injection amount restriction unit 32 is used by the actual torque calculation unit 33, and the actual torque calculation unit 33 is based on the actual rotational speed and the actual fuel injection amount calculated by the control device 30. The actual torque output from the engine E is calculated. On the other hand, the target torque calculator 31 calculates the target torque based on the target fuel injection amount and the actual rotational speed. Next, the first assist torque calculator 34 calculates a shortage of torque obtained by subtracting the actual torque from the target torque, that is, the first assist torque, based on the calculated target torque and actual torque. Since the actual fuel injection amount is limited, as shown in the graph of the first assist torque in FIG. 4, the first assist torque becomes the largest when the load of the hydraulic pump 17 increases rapidly, It decreases as the actual fuel injection amount increases (see times t1 to t2 in the graph of the first assist torque in FIG. 4). When the actual fuel injection amount reaches the target fuel injection amount, the first assist torque becomes zero (see time t2 in the graph of the first assist torque in FIG. 4).

  As described above, in the hydraulic pump drive system 1, it is possible to restrict the increase rate (or increase amount) of the actual fuel injection amount and prevent the actual fuel injection amount from rapidly changing. Thereby, it can suppress that the combustion state of the engine E deteriorates, and the fuel consumption of the engine E can be improved. In addition, the control device 30 calculates in advance a first assist torque that is a torque that is insufficient by limiting the fuel injection amount. By outputting the first assist torque from the electric motor 20, the torque output from the entire hydraulic pump drive system 1 can be brought close to the target torque even if the actual fuel injection amount is limited. Thereby, it can suppress that the torque output as the hydraulic pump drive system 1 whole falls. Thus, in the hydraulic pump drive system 1, the amount of change in the output torque is estimated in advance and the torque is output to the electric motor 20, and the engine is compared with the case where the torque is adjusted according to the deviation in the rotational speed. It can suppress that the rotation speed of E falls too much.

  Further, the torque change estimation unit 35 of the control device 30 calculates a torque change coefficient based on the calculated actual rotational speed and the actual fuel injection amount, and further calculates a torque change amount (second assist torque). That is, in the torque change estimation unit 35, the time constant calculation unit 41 calculates a time constant from the actual rotational speed using the time constant map 41a, and the pseudo-differential calculation unit 42 uses the calculated time constant to calculate the actual fuel injection amount. The derivative value of is calculated. Next, the torque change coefficient calculation unit 44 calculates the absolute value of the differential value of the actual fuel injection amount, and the torque change coefficient calculation unit 44 further uses the torque change coefficient map 44a to calculate the absolute value of the differential value of the actual fuel injection amount. The torque change coefficient is calculated from Since the calculated torque change coefficient is calculated based on the value including the element of the first-order lag calculated by the pseudo-differential calculation unit 42, the first-order lag as shown in the torque change coefficient graph of FIG. (See times t1 to t2 in the graph of the torque change coefficient in FIG. 4). The calculated torque change coefficient is expressed as a positive value. When the actual fuel injection amount is increased with time at a constant increase rate (that is, a proportional constant), the torque change coefficient changes with a first-order lag response.

  The pseudo differential calculation unit 42 calculates the rate of change of the actual fuel injection amount for each unit speed by changing the time constant for each calculation, and the torque change amount calculation unit 47 calculates the change rate and the actual torque. Based on the above, the amount of change in the output torque for each unit speed is calculated. This is because the change in the actual fuel injection amount affects the combustion state of the engine E not only at the time of combustion immediately after supply but also over several subsequent combustions. That is, the influence on the combustion state due to the change in the actual fuel injection amount is reduced by passing the number of combustions instead of time. Therefore, after the actual fuel injection amount reaches the target fuel injection amount, the deterioration of the combustion state does not stop and the torque decreases, and after the engine E performs a predetermined number of combustions (that is, a predetermined number of rotations). , The combustion state is improved. Thus, the combustion state of the engine E changes according to the number of combustions (that is, the number of revolutions) rather than the time. In view of this, the pseudo-differential calculation unit 42 calculates the rate of change of the actual fuel injection amount for each unit speed. In addition, by using a pseudo-differential when calculating the rate of change of the actual fuel injection amount, the rate of change of the actual fuel injection amount becomes zero from zero even after the actual fuel injection amount reaches the target fuel injection amount and becomes constant. A large value is calculated, and as a result, the torque change coefficient becomes a value larger than zero. Thereafter, the torque change coefficient decreases toward zero (see times t2 to t3 in the torque change coefficient graph of FIG. 4). That is, the torque change estimation unit 35 takes into account the torque change coefficient and the torque change amount after the actual fuel injection amount reaches the target fuel injection amount and becomes constant.

  Thus, since the change in the output torque is calculated not in the time unit but in the rotation speed unit, it is possible to estimate the decrease in the output torque of the engine E more accurately than in the case of calculating in the time unit. As a result, it is possible to prevent the rotational speed from excessively decreasing due to a decrease in output torque due to deterioration in combustion, and to suppress a decrease in fuel consumption of the engine that accompanies it. Since the torque change coefficient is calculated not according to the time but according to the number of combustions in the engine E, the time interval between times t2 and t3 is based on the value of the actual rotational speed. Since the pseudo-differential calculation unit 42 changes the time constant according to the actual rotational speed, the torque reduction coefficient at times t2 to t3 can be calculated in detail. As a result, the torque change estimation unit 35 can estimate a more accurate torque change coefficient and torque change amount.

  The correction coefficient calculator 46 calculates a correction coefficient in parallel with the calculation of the torque change coefficient. That is, the correction coefficient calculator 46 calculates the first correction coefficient and the second correction coefficient based on the calculated actual rotational speed and actual fuel injection amount, respectively, and further calculates the first correction coefficient and the second correction coefficient. Based on this, a correction coefficient is calculated. The torque change rate calculation unit 45 calculates the torque change rate based on the calculated correction coefficient and torque change coefficient, and the torque change amount calculation unit 47 calculates the torque change amount based on the torque change rate and the actual torque. . The torque change amount calculated in this way increases with time as shown in the torque change amount in FIG. 4 and peaks at time t2, and the combustion state in the engine E improves from time t2 to time t3. As it happens, it decreases rapidly. In addition, the torque change amount of FIG. 4 represents the torque amount to reduce as positive. Thus, the torque change estimation unit 35 estimates the torque change amount, and the estimated torque change amount is used by the second assist torque calculation unit 36. The second assist torque calculator 36 calculates the second assist torque based on this torque change amount.

  The second assist torque calculation unit 36 selects a first predetermined value (for example, 1) as a multiplication coefficient when the differential value of the actual fuel injection amount calculated by the pseudo-differential calculation unit 42 is zero or more. When the differential value of the fuel injection amount is less than zero, a second predetermined value (for example, 0) is selected as the multiplication coefficient. The second assist torque calculator 36 calculates the second assist torque by multiplying the torque change amount by this multiplication coefficient. The drive control unit 37 calculates the assist torque by adding the calculated first assist torque and second assist torque. The calculated assist torque changes as shown in the assist torque graph of FIG. 4, and further compensates for the shortage of the target torque (difference torque corresponding to the shortage of the target torque minus the actual torque). A torque change amount (a change torque corresponding to a shortage of torque that decreases with a change in the actual fuel injection amount) is also compensated. Therefore, it becomes the largest when the load of the hydraulic pump 17 suddenly increases, and decreases as the actual fuel injection amount increases (see the times t1 to t2 in the torque change amount graph of FIG. 4). Further, even after the differential torque (first assist torque) becomes zero, the change torque (second assist) from time t2 to time t3 in order to compensate for the change in output torque due to the transition of the combustion state of the engine E. Torque) is calculated as the assist torque. The control device 30 controls the movement of the inverter 22 based on the calculated assist torque to cause the electric motor 20 to output the assist torque.

  Thus, the hydraulic pump drive system 1 preliminarily estimates the amount of change in the output torque due to the transition of the combustion state of the engine E caused by the change in the actual fuel injection amount by the torque change estimation unit 35, and the estimated change The engine E can be assisted by outputting the second assist torque corresponding to the amount from the electric motor 20. That is, a decrease in the output torque of the engine E can be estimated in advance, and the decrease can be assisted by the electric motor. As a result, when the hydraulic pump 17 is loaded, it is possible to prevent the output torque from being reduced due to the transition of the combustion state and the rotational speed from being excessively decreased, and the hydraulic pump associated with the excessive decrease in the rotational speed can be prevented. A decrease in operability due to a decrease in the discharge flow rate can be suppressed.

  Thereafter, when the actual fuel injection amount reaches the target fuel injection amount and the engine E rotates a predetermined number of times, the combustion state of the engine E becomes stable, and as a result, the torque change coefficient becomes substantially zero, that is, the torque change amount becomes zero. (See times t3 to t4 in the graph of the torque change coefficient and the torque change amount in FIG. 4). Then, in the hydraulic pump drive system 1, the pump is driven only by the engine E, and the assist from the electric motor 20 is lost (see times t3 to t4 in FIG. 4).

  Next, when the operation of the operation tool is stopped (that is, the operation tool is returned to the neutral position) and the hydraulic pump 17 is switched from the on-load state to the unload state, the load on the hydraulic pump 17 is reduced. In the hydraulic pump 17, so-called load loss occurs (see time t4 in the pump load graph of FIG. 4). When the load loss occurs, the actual rotational speed of the engine E becomes larger than the target rotational speed, and the control device 30 calculates the target fuel injection amount from the difference between the actual rotational speed and the target rotational speed. Since the actual rotational speed of the engine E is larger than the target rotational speed, the control device 30 decreases the target fuel injection amount so that the actual rotational speed becomes the target rotational speed when calculating the target fuel injection amount. Therefore, the injection amount limiting unit 32 determines that the increase rate of the target fuel injection amount is not equal to or greater than the predetermined value, and calculates the target fuel injection amount as the actual fuel injection amount (time t4 in the graph of the actual fuel injection amount in FIG. 4). To t5). Thereby, the target torque and the actual torque calculated by each of the target torque calculation unit 31 and the actual torque calculation unit 33 coincide with each other, and the first assist torque calculation unit 34 calculates the first assist torque to be zero. (See times t4 to t5 in the graph of the first assist torque in FIG. 4). Further, the torque change estimation unit 35 estimates the torque change coefficient and the torque change amount based on the calculated actual rotational speed and the actual fuel injection amount as in the case where the operation tool is operated (torque change in FIG. 4). (Refer to times t4 to t5 in the graph of coefficient and torque change amount). On the other hand, since the differential value of the actual fuel injection amount is less than zero, the second assist torque calculator 36 selects zero as the multiplication coefficient. The second assist torque calculator 36 calculates the second assist torque by multiplying the torque change amount by this multiplication coefficient, so the second assist torque becomes zero.

  Thus, when the hydraulic pump 17 is unloaded, the actual engine speed of the engine E increases rapidly (see times t4 to t5 in the engine speed graph of FIG. 4), and the target fuel injection is rapidly performed to decrease it. The amount is reduced. Even in such a case, the transition of the combustion state of the engine E occurs as in the case where the actual rotational speed rapidly decreases, resulting in a torque change (specifically, a torque decrease). However, when the load is lost, it is necessary to reduce the output torque of the hydraulic pump 17. Therefore, it is preferable to prevent the assist torque from being generated from the electric motor 20 that prevents the actual rotational speed of the engine E from being lowered. Therefore, in the hydraulic pump drive system 1, when the differential value of the actual fuel injection amount is less than zero, the multiplication coefficient in the second assist torque calculator 36 is set to zero so that assist torque is not generated when the load is released. Thereby, when the output torque is reduced by the engine, it is possible to prevent wasteful consumption of energy by the electric motor.

  Further, as will be described later, since the injection amount limiting unit 32 has a rate limiting function that does not limit the reduction rate, the first assist torque calculating unit 34 sets the first assist torque to zero. Therefore, regenerative power is not generated in the electric motor, and the fuel efficiency of the engine E can be improved.

[Other embodiments]
In the hydraulic pump drive system 1 of this embodiment, the injection amount limiting unit 32 has a rate limit function that does not limit the decrease rate, and the second assist torque is zero when the differential value of the actual fuel injection amount is less than zero. The second assist torque calculator 36 has a function of Below, operation | movement of 1 A of hydraulic pump drive systems of 1st Embodiment which does not have these functions is demonstrated, referring FIG. The configuration of the hydraulic pump drive system 1A is the same as that of the hydraulic pump drive system 1 except for the functions described above, and therefore, FIG. 1 to FIG. 3 are referred to. In FIG. 5, similarly to FIG. 4, the pump load (load of the hydraulic pump 17), the engine speed (actual speed), the target fuel injection amount, the actual fuel injection amount, the first assist torque, and the torque in order from the paper surface. A change coefficient, a torque change amount, and an assist torque change with time are shown. In FIG. 5, the horizontal axis represents time, and the vertical axis represents various values.

  In the hydraulic pump drive system 1 </ b> A according to another embodiment, changes in various values when a load is applied are the same as those in the hydraulic pump drive system 1, and changes in various values when a load is lost are different from the hydraulic pump drive system 1. For example, the actual fuel injection amount and the first assist torque in the hydraulic pump drive system 1A change as shown in FIG. That is, when the load is lost, the actual fuel injection amount decreases stepwise in proportion to time (see the actual fuel injection amount times t6 to t7 in FIG. 5), and the first assist torque is calculated as the regenerative force. (Refer to times t6 to t7 of the first assist torque in FIG. 5). On the other hand, in the engine E, the torque is reduced as the actual fuel injection amount is reduced. Therefore, the second assist torque calculator 36 calculates the second assist torque based on the torque change amount estimated by the torque change estimator 35 to compensate for this. The first assist torque and the second assist torque calculated in this way are added by the drive control unit 37.

  Thus, in the hydraulic pump drive system 1A, useless regeneration by the first assist torque is performed while assisting the engine E when the load is lost. Therefore, the efficiency of the system is lowered. In the hydraulic pump drive system 1A, the second assist torque is output in order to compensate for the torque drop due to the transition of the fuel state of the engine E when the actual fuel injection amount is reduced when the load is released. Therefore, the output torque of the engine E is unnecessarily assisted although it is desired to quickly reduce the pump load. In order to avoid these, in the hydraulic pump drive system 1, the injection amount limiting unit 32 has a rate limiting function without limiting the reduction rate, and the second assist torque calculating unit 36 takes into account the differential value of the actual fuel injection amount. Thus, the second assist torque is calculated. That is, the rate limit function without the reduction rate limitation of the injection amount limiting unit 32 prevents unnecessary regeneration due to the first assist torque when the load is lost, and the second assist torque calculating unit 36 determines the actual fuel injection amount. By calculating the second assist torque in consideration of the differential value, it is possible to quickly reduce the output torque of the engine E when the load is lost. Here, the description of the hydraulic pump drive system 1 shows that it is a preferable function to calculate the second assist torque in consideration of the rate limit function without the reduction rate limit and the differential value of the actual fuel injection amount. Thus, it does not necessarily exclude those having these functions. That is, the hydraulic pump drive system 1A is also an embodiment according to the present invention.

[Other configuration]
In the hydraulic pump drive systems 1 and 1A of the present embodiment, the amount of change in torque per unit revolution (for example, torque per revolution) is simulated by changing the time constant of pseudo differentiation based on the actual revolution. It has been calculated. In addition to this method, a pseudo differential calculation may be actually performed for each unit rotation speed, and the amount of torque change for each unit rotation may be actually obtained. That is, as the actual rotational speed increases, the interval for calculating the torque change amount becomes shorter, and as the actual rotational speed decreases, the interval for calculating the torque change amount becomes longer. Thereby, the amount of change in torque per unit rotation speed can be estimated.

  In the hydraulic pump drive systems 1 and 1A, the first assist torque and the second assist torque are calculated and added to obtain the assist torque, but only one of the first assist torque and the second assist torque is used as the assist torque. It is good. That is, the hydraulic pump drive systems 1 and 1A do not necessarily have the function of calculating both the first assist torque and the second assist torque, and include the target torque calculation unit 31 and the first assist torque calculation unit 34. It does not have to be. When the target torque calculating unit 31, the injection amount limiting unit 32, and the first assist torque calculating unit 34 are not provided, the target fuel injection amount calculating unit 38 functions as an actual fuel injection amount calculating unit. The torque change estimation unit 35 is not limited to the estimation method as described above, and any method that can estimate the change in the output torque of the engine E due to the change in the actual fuel injection amount may be used.

  The construction machine on which the hydraulic pump drive systems 1 and 1A are mounted is not limited to a hydraulic excavator, and may be another construction machine such as a crane or a dozer, as long as it is a construction machine provided with a hydraulic actuator. Good. In the hydraulic pump drive systems 1 and 1A, the hydraulic pump is described as an example of the hydraulic pump. However, the hydraulic pump is not limited to the hydraulic pump and may be a pump that discharges liquid such as water.

DESCRIPTION OF SYMBOLS 1,1A Hydraulic pump drive system 17 Hydraulic pump 17a Rotating shaft 20 Electric motor 23 Rotation speed sensor 30 Control apparatus 31 Target torque calculating part 32 Injection amount restriction | limiting part (actual fuel injection amount calculating part)
33 Actual torque calculator 34 First assist torque calculator (difference torque calculator)
35 Torque change estimation unit 36 Second assist torque calculation unit (change torque calculation unit)
38 Target fuel injection amount calculation section 37 Drive control section 41 Time constant calculation section 42 Pseudo-differential calculation section 44 Torque change coefficient calculation section 45 Torque change rate calculation section 46 Correction coefficient calculation section 47 Torque change amount calculation section

Claims (11)

An engine that rotationally drives the rotary shaft of the hydraulic pump;
An electric motor capable of assisting rotation driving of the rotating shaft;
A rotational speed sensor for detecting the actual rotational speed of the rotary shaft;
A control device for controlling the movement of the electric motor,
The control device includes a target fuel injection amount calculation unit, an injection amount restriction unit, an actual torque calculation unit, a target torque calculation unit, a differential torque calculation unit, and a drive control unit,
The target fuel injection amount calculation unit calculates a target fuel injection amount based on the actual rotational speed and the target rotational speed,
The injection amount limiting unit calculates an actual fuel injection amount to be injected next, and when calculating the actual fuel injection amount based on the target fuel injection amount, the injection amount limiting unit performs stepwise to the target fuel injection amount. Having a function of increasing the fuel injection amount, determining the actual fuel injection amount so that the time change rate of the actual fuel injection amount when increasing the fuel injection amount becomes a predetermined value or less,
The actual torque calculation unit calculates an actual torque output from the engine based on an actual rotation speed detected by the rotation speed sensor and an actual fuel injection amount determined by the injection amount restriction unit,
The target torque calculation unit calculates a target torque to be applied to the rotating shaft based on the actual rotation number detected by the rotation number sensor and the target fuel injection amount calculated by the target fuel injection amount calculation unit. And
The differential torque calculation unit calculates a differential torque that is insufficient with the actual torque calculated by the actual torque calculation unit with respect to the target torque calculated by the target torque calculation unit,
The drive control unit is a hydraulic pump drive system that controls the movement of the electric motor to output the differential torque.   2. The hydraulic pump drive system according to claim 1, wherein when the target fuel injection amount is decreasing, the injection amount limiting unit sets the target fuel injection amount as the actual fuel injection amount.   When the target fuel injection amount is increased when the actual fuel injection amount is calculated based on the target fuel injection amount, the injection amount limiting unit is based on a change rule that changes in proportion to the elapsed time. The hydraulic pump drive system according to claim 1, wherein the actual fuel injection amount is increased stepwise.   When the target fuel injection amount is increased when calculating the actual fuel injection amount based on the target fuel injection amount, the injection amount limiting unit is based on a change rule that causes a primary delay with respect to the elapsed time. The hydraulic pump drive system according to claim 1, wherein the actual fuel injection amount is increased stepwise. The control device includes a torque change estimation unit and a change torque calculation unit,
The torque change estimation unit estimates the amount of change in the output torque of the engine based on the actual fuel injection amount and the actual rotational speed calculated by the injection amount limiting unit,
The change torque calculation unit calculates a change torque to be assisted based on a change amount of the output torque calculated by the torque change estimation unit,
5. The hydraulic pump drive system according to claim 1, wherein the drive control unit controls the movement of the electric motor to output a torque obtained by adding the change torque to the differential torque. 6.   The torque change estimation unit estimates a rate of change of the output torque per unit revolution of the engine based on the actual fuel injection amount, and the actual torque and the rate of change calculated by the actual torque calculation unit The hydraulic pump drive system according to claim 5, wherein a change amount of the output torque is calculated based on the hydraulic pressure.   The torque change estimation unit includes a pseudo-differential calculation unit including a first-order lag element whose time constant can be changed, and a time constant for changing the time constant of the first-order lag element according to the rotation speed of the rotating shaft detected by the rotation speed sensor. A constant calculation unit, calculating a change rate of the actual fuel injection amount per unit rotation speed of the engine using pseudo differentiation, and calculating a unit rotation speed of the engine based on the change rate of the actual fuel injection amount. The hydraulic pump drive system according to claim 5 or 6, wherein an amount of change in the output torque at a hit is estimated.   The hydraulic pump drive system according to claim 7, wherein the change torque calculation unit sets the change torque to zero when a change rate of the actual fuel injection amount is less than zero. An engine that rotationally drives the rotary shaft of the hydraulic pump;
An electric motor capable of assisting rotation driving of the rotating shaft;
A rotational speed sensor for detecting the actual rotational speed of the rotary shaft;
A control device for controlling the movement of the electric motor,
The control device includes an actual fuel injection amount calculation unit, a torque change estimation unit, a change torque calculation unit, and a drive control unit,
The actual fuel injection amount calculation unit calculates an actual fuel injection amount to be injected next based on the actual rotation speed and the target rotation speed,
The torque change estimating unit estimates a change amount of the output torque of the engine based on the actual fuel injection amount and the actual rotational speed calculated by the fuel injection amount calculating unit,
The change torque calculation unit calculates a change torque to be assisted based on a change amount of the output torque calculated by the torque change estimation unit,
The drive control unit is a hydraulic pump drive system that controls movement of the electric motor to output the change torque. The control device has an actual torque calculation unit,
The actual torque calculation unit calculates an actual torque output from the engine based on the actual rotation speed detected by the rotation speed sensor and the actual fuel injection amount calculated by the fuel injection amount calculation unit,
The torque change estimation unit estimates a rate of change of the output torque per unit revolution of the engine based on the actual fuel injection amount, and the actual torque and the rate of change calculated by the actual torque calculation unit The hydraulic pump drive system according to claim 9, wherein the change amount of the output torque is calculated based on the hydraulic pressure.   The torque change estimation unit includes a pseudo-differential calculation unit including a first-order lag element whose time constant can be changed, and a time constant for changing the time constant of the first-order lag element according to the rotation speed of the rotating shaft detected by the rotation speed sensor. A constant calculating unit, calculating a rate of change of the actual fuel injection amount per unit rotational speed of the engine using pseudo differentiation, and calculating the engine of the output torque based on the rate of change of the actual fuel injection amount The drive system of the hydraulic pump according to claim 9 or 10, wherein the amount of change per unit rotational speed is estimated.