JP6336855B2 - 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. . Then, the control device increases the fuel injection amount so as to return the engine speed to the engine speed command value. At this time, the control device assists the engine by moving the electric motor.

International Publication No. 2013/031525

  In the construction machine of Patent Document 1, the drive control of the electric motor is performed based on the deviation between the rotational speed and the rotational speed command value. Therefore, when the deviation of the rotational speed becomes large regardless of the combustion state of the engine, the motor assists the engine. Therefore, even when the decrease in the output torque of the engine is small and the increase in the fuel injection amount is relatively small, the engine is assisted by the electric motor. When the increase in the fuel injection amount is relatively small, the combustion state of the engine is stable. Therefore, even if the engine is assisted by the electric motor, improvement in the combustion state cannot be expected so much, and fuel efficiency cannot be improved by improving the combustion state. Nevertheless, the assistance by the electric motor is forcibly performed, and electric power is wasted.

  Therefore, an object of the present invention is to provide a drive system for a hydraulic pump that can reduce power consumption.

  A drive system for a hydraulic pump according to the present invention includes an engine that rotationally drives a rotary shaft of a hydraulic pump, an electric motor that rotates the rotary shaft by receiving power supply, and assists the engine, and an actual implementation of the rotary shaft. A rotational speed sensor for detecting the rotational speed; and a control device that determines a fuel injection amount of the engine and controls movement of the electric motor, the control device comprising: a torque command calculation unit; a fuel injection amount; A calculation unit, a torque change estimation unit, an assist torque determination unit, an assist determination unit, and a drive control unit are included, and the torque command calculation unit is configured to return the actual rotation number to a predetermined target rotation number. Based on a rotational speed deviation that is a deviation between the actual rotational speed and the target rotational speed, an engine torque command that is an engine torque to be output to the engine is calculated, and the fuel injection amount calculation unit An actual fuel injection amount to be injected by the engine is calculated based on an engine torque command calculated by the command calculation unit and the actual rotational speed, and the torque change estimation unit is calculated by the fuel injection amount calculation unit. A change value of the output torque of the engine is estimated based on the actual fuel injection amount and the actual rotational speed, and the assist torque determining unit determines an assist torque to be output to the electric motor based on the rotational speed deviation, The assist determination unit sets the assist torque command to zero when the output torque change value estimated by the torque change estimation unit is less than a predetermined threshold value, and the output torque change value is a predetermined threshold value. When the above is true, the torque corresponding to the assist torque is used as an assist torque command, and the drive control unit determines the assist torque determined by the assist output determination unit. The command is intended to be output from the electric motor.

  According to the present invention, whether the assist torque command is set to zero or the assist torque is determined based on the estimated change value of the output torque. Therefore, the movement of the electric motor can be controlled in accordance with the change value of the output torque. That is, when the change value of the output torque is less than the threshold value, the motor can be stopped, and when the change value of the output torque is equal to or more than the threshold value, the motor can be assisted. When the change value of the output torque is small, the change of the fuel injection amount is small and the combustion state of the engine is relatively stable. In such a stable state, since the effect of suppressing the change in output torque by the electric motor is small, it is possible to suppress wasteful consumption of the electric power stored in the battery by stopping the electric motor. That is, the power consumption consumed by the electric motor can be reduced. On the other hand, when the change value of the output torque is large, the change of the fuel injection amount is large, and the combustion state of the engine is unstable. The combustion state can be stabilized by assisting the engine with the electric motor in such an unstable state, and the fuel consumption can be improved.

  In the above invention, the assist torque determination unit sets the assist torque to zero when the rotation speed deviation, which is a value obtained by subtracting the target rotation speed from the actual rotation speed, is zero or more, and the rotation speed deviation is less than zero. In this case, the assist torque may be set to a preset torque value.

  According to the above configuration, when the actual rotational speed is greater than the target rotational speed, the electric motor is not operated in order to reduce the actual rotational speed of the engine to the target rotational speed even if the change value of the output torque increases. It has become. That is, the regenerative operation of the electric motor is not performed in order to reduce it. Therefore, it is possible to avoid a low energy efficiency situation in which the regenerative operation is performed by the electric motor while consuming excess fuel in the engine, and the fuel consumption can be improved.

  In the above invention, the preset torque value in the assist torque determination unit may be a torque that the electric motor can output with an efficiency of 80% to 95%.

  According to the above configuration, since the electric motor can be driven with high efficiency, consumption of electric power stored in the electric storage device can be suppressed.

  In the above invention, the assist determination unit includes a correction coefficient calculation unit and an assist torque correction unit, and the correction coefficient calculation unit has a change value of the output torque estimated by the torque change estimation unit in advance. The correction coefficient is set to zero when it is less than a predetermined threshold value, and is set to a predetermined positive value when the change value of the output torque is greater than or equal to the threshold value. The assist torque correction unit is calculated by the correction coefficient calculation unit. The assist torque command may be calculated by correcting the assist torque using a correction coefficient.

  According to the above configuration, the motor can be moved or stopped by calculating the assist torque command by correcting the assist torque with the correction coefficient.

  In the above-described invention, a storage amount sensor that detects a storage amount of a capacitor that supplies electric power to the electric motor is provided, and the assist determination unit decreases the correction coefficient as the storage amount detected by the storage amount sensor decreases. You may come to do.

  According to the above configuration, it is possible to prevent a large amount of current from flowing through the drive system of the motor due to a decrease in the amount of electricity stored in the capacitor.

  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 change value of the output torque per unit rotational speed may be estimated.

  According to the above configuration, it is possible to practically calculate a change value of the output torque for each unit rotational speed by using a pseudo differential 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 fuel injection amount calculation unit has a target fuel injection amount calculation part and an injection amount restriction part, and the target fuel injection amount calculation part is an engine torque command calculated by the torque command calculation part. And a target fuel injection amount that is a target based on the actual rotational speed, and the injection amount limiting portion is configured to calculate the actual fuel injection amount based on the target fuel injection amount calculated in the target fuel injection amount calculation portion. When calculating the actual fuel injection amount in a stepwise manner up to the target fuel injection amount, and the time change rate of the actual fuel injection amount when increasing is less than or equal to a predetermined value. The fuel injection amount is determined, and the control device includes an actual torque calculation unit, a target torque calculation unit, and a differential torque calculation unit, and the actual torque calculation unit is detected by the rotational speed sensor. Rotational speed and injection amount limiting unit The actual torque output from the engine is calculated on the basis of the actual fuel injection amount determined in step (i), and the target torque calculation unit is configured to calculate the actual rotation speed detected by the rotation speed sensor and the target fuel injection amount calculation part. The target torque, which is a target torque to be output to the engine, is calculated based on the target fuel injection amount calculated in step (i), and the differential torque calculation unit is configured to calculate the target torque calculated in the target torque calculation unit. The difference torque that is insufficient with the actual torque calculated by the actual torque calculation unit is calculated, and the drive control unit adds a torque obtained by adding the difference torque calculated by the difference torque calculation unit to the assist torque command. May be output.

  According to the above configuration, the increase rate of the actual fuel injection amount is limited when the target fuel injection amount suddenly increases. By limiting the increase rate in this way, it is possible to prevent instability of the combustion state of the engine 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 by being limited is smaller than the target torque, that is, insufficient torque is generated, the shortage can be output to the motor. Thereby, it can prevent that the rotation speed of the engine E accompanying torque shortage falls too much.

  According to the present invention, power consumption can be reduced.

It is a block diagram which shows the hydraulic pump drive system which concerns on 1st and 2nd embodiment of this invention. It is the functional block diagram which showed the function which the control apparatus with which the hydraulic pump drive system of 1st Embodiment of this invention has was shown as a block. FIG. 3 is a functional block diagram illustrating a torque change estimation unit 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. 2 is a graph showing changes over time of various values when a regenerative operation is performed in the hydraulic pump drive system of FIG. 1. It is the functional block diagram which showed the function which the control apparatus with which the hydraulic pump drive system of 2nd Embodiment of this invention has was shown as a block. It is the functional block diagram shown in order to demonstrate a part of control apparatus of FIG. 6 in detail.

  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 manner, 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, but 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 is connected to the battery 24, converts a direct current supplied from the battery 24 into an alternating current, and supplies the alternating current to the electric motor 20. A voltage sensor 25 (electric storage amount sensor) for detecting the electric storage amount of the battery 24 is connected to the battery 24 (electric storage device). The voltage sensor 25 is connected to a control device 30 described later, and outputs a signal corresponding to the output voltage of the battery 24 to the control device 30.

  Further, the inverter 22 supplies an alternating current having a frequency and voltage according to the input assist torque command to the electric motor 20, and outputs torque corresponding to the assist torque command from the electric motor 20 to the rotating shaft 17a. . 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 voltage sensor 25, the inverter 22, and the electromagnetic control valve of the fuel injection device 21.

  The control device 30 has a functional part that calculates various values as shown in FIG. 2. In the following, each functional part that calculates various values and controls the movement of the above-described configuration is divided into blocks. Separately described. The control device 30 includes a target rotation speed determination unit 31, a rotation speed difference calculation unit 32, a torque command calculation unit 33, a fuel injection amount calculation unit 34, and a fuel injection drive unit 35. Each functional unit calculates various values at a predetermined interval or controls the movement of the configuration at a predetermined interval.

  The target rotational speed determination unit 31 determines the target rotational speed of the engine based on the rotational speed input from the input means (dial, button, touch panel, etc.) or set in advance. The rotational speed difference calculation unit 32 calculates the actual rotational speed of the rotating shaft 17a based on the signal input from the rotational speed sensor 23, and the target rotational speed determined by the calculated actual rotational speed and the target rotational speed determination unit 31. Rotational speed deviation, which is the difference from the number, is calculated. In the present embodiment, the rotational speed deviation is a value obtained by subtracting the target rotational speed from the actual rotational speed. The torque command calculator 33 calculates an engine torque command based on the rotation speed deviation calculated by the rotation speed difference calculator 32. The engine torque command is a command indicating the torque of the engine E to be output in order to return the actual rotation speed of the engine E to the target rotation speed. The fuel injection amount calculation unit 34 calculates the actual fuel injection amount to be injected from the fuel injection device 21 based on the engine torque command calculated by the torque command calculation unit 33 and the actual rotational speed. The fuel injection drive unit 35 controls the movement of the fuel injection device 21 based on the actual fuel injection amount calculated by the fuel injection amount calculation unit 34 so as to inject the fuel of the actual fuel injection amount from the fuel injection device 21. It has become.

  In addition, the control device 30 includes an assist torque determination unit 36, a torque change estimation unit 37, a correction coefficient calculation unit 38, an assist torque correction unit 39, and a drive control unit 40 in order to drive the electric motor 20. Each functional unit described above also calculates various values at predetermined intervals or controls the movement of the configuration at predetermined intervals.

  The assist torque determination unit 36 determines the assist torque value from the electric motor 20 based on the rotation speed deviation calculated by the rotation speed difference calculation unit 32. More specifically, the assist torque determination unit 36 sets the assist torque to zero when the rotation speed deviation (a value obtained by subtracting the target rotation speed from the actual rotation speed) is zero or more. On the other hand, when the rotational speed deviation is less than zero, the assist torque determination unit 36 sets the assist torque to a preset positive torque value. In the present embodiment, the set positive torque value is the maximum torque that can be output by the electric motor 20 that is used, and is the torque that can be output with the highest efficiency. The set torque value does not necessarily need to be the maximum torque, and is set to a torque that can be output by the electric motor 20 with a high efficiency of 80% or more and 95% or less. The assist torque determined in this manner is corrected according to the change value of the output torque of the engine E, and the change value of the output torque of the engine E is estimated by the torque change estimation unit 37.

  The torque change estimation unit 37 estimates a change value of the output torque of the engine E, that is, a reduction coefficient, based on the actual fuel injection amount and the actual rotational speed calculated by the fuel injection amount calculation unit 34. 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. Further, 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 combustion state is improved as the number of combustion passes. The 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 revolution, the torque change estimation unit 37 calculates a decrease in the output torque at every unit revolution of the engine E (preferably every revolution). It is supposed to be. In the present embodiment, the torque change estimation unit 37 estimates the change in the output torque of the engine E by numerically modeling the engine E using a transfer function including a pseudo-derivative, which will be described later, and is a first-order lag element included in the pseudo-differential. The 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 transfer function described above. The calculation of the torque change estimation unit 37 is performed at a predetermined interval. The torque change estimation unit 37 that estimates the change in output torque in this way will be described in more detail with reference to FIG.

  The torque change estimation unit 37 includes a time constant calculation unit 41, a pseudo-differentiation calculation unit 42, and a torque reduction coefficient calculation unit 43 as functional parts for estimating a change in output torque. The time constant calculation unit 41 calculates a time constant from the actual rotational speed using a 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 revolution of the output torque of the engine E, and a torque reduction coefficient described later is calculated by the torque reduction coefficient calculation unit 43. Used for.

  The torque reduction coefficient calculator 43 calculates a torque reduction coefficient based on the differential value of the actual fuel injection amount calculated by the pseudo-differential calculator 42. The torque reduction coefficient, which is a change value of the output torque, is a coefficient indicating how much the torque changes with respect to the engine torque command (actual torque). The torque reduction coefficient calculation unit 43 first calculates the absolute value of the differential value of the actual fuel injection amount, and then calculates the torque reduction coefficient from the absolute value of the differential value of the actual fuel injection amount using the torque reduction coefficient map 43a. . The torque reduction coefficient map 43a is a map in which the absolute value of the differential value of the actual fuel injection amount is associated with the torque reduction coefficient. For example, the torque reduction coefficient map 43a is set so that the torque reduction 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 in the torque reduction coefficient map 43a and the torque reduction 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. It should be noted that the correspondence relationship between the absolute value of the differential value of the actual fuel injection amount and the torque reduction coefficient is not necessarily a correspondence relationship as shown in FIG. Note that the value calculated as the change value of the output torque of the engine E does not necessarily have to be a torque reduction coefficient, and the torque change amount may be directly calculated. The calculated torque reduction coefficient is used in the correction coefficient calculation unit 38.

  In the assist determination unit 44, the correction coefficient calculation unit 38 calculates a correction coefficient based on the torque reduction coefficient calculated by the torque reduction coefficient calculation unit 43. The correction coefficient is a coefficient for correcting the assist torque determined by the assist torque determination unit 36 according to the change value of the output torque of the engine E. The assist determination unit 44 calculates the assist torque when the torque reduction coefficient is small. It is set not to output.

  The correction coefficient calculator 38 calculates a correction coefficient from the torque reduction coefficient using the correction coefficient map 38a. The correction coefficient map 38a is a map in which a torque reduction coefficient and a correction coefficient are associated with each other. In the present embodiment, in the correction coefficient map 38a, the correction coefficient is zero when the torque reduction coefficient is less than a predetermined threshold, and the correction coefficient is a predetermined value (= 1) when the torque reduction coefficient is equal to or greater than the threshold. Is set to The correction coefficient calculated in this way is used in the assist torque correction unit 39 shown in FIG.

  The assist torque correction unit 39 corrects the assist torque determined by the assist torque determination unit 36 with the correction coefficient calculated by the correction coefficient calculation unit 38. Specifically, the assist torque correction unit 39 corrects the assist torque by multiplying the determined assist torque by a correction coefficient, and calculates an assist torque command that is the corrected assist torque. The calculated assist torque command is used by the drive control unit 40, and the drive control unit 40 drives the electric motor 20 by controlling the movement of the inverter 22 to output the assist torque command from the electric motor 20. . In the present embodiment, an assist determination unit 44 is configured by the correction coefficient calculation unit 38 and the assist torque correction unit 39.

  The control device 30 configured as described above increases the actual fuel injection amount of the engine E to compensate for the decreased rotational speed when the load of the hydraulic pump 17 increases and the rotational speed of the engine E decreases. If necessary, the electric motor 20 is driven to assist the engine E. In the following, first, the operation of the hydraulic pump drive system 1 when any of the hydraulic actuators 11 to 15 is operated to increase the load of the hydraulic pump 17 (that is, when the load is applied) will be described with reference to the graph of FIG. explain. 4 shows the pump load (load of the hydraulic pump 17), engine rotation speed (actual rotation speed) engine torque command, assist torque, torque reduction coefficient, and change over time of the assist torque command in order from the top of the drawing. ing. In FIG. 4, the horizontal axis represents time and the vertical axis represents various values. The same applies to FIG. 5 described later.

  When the operation tool is operated and the control valve 18 is activated, the hydraulic pump 17 is switched from the unloaded state to the on-loaded state, and a large load acts on the hydraulic pump 17 (time t1 to t1 in the pump load graph of FIG. 4). t4). When the load on the hydraulic pump 17 increases, the actual rotational speed of the engine E decreases (see times t1 to t2 in the engine rotational speed graph of FIG. 4), and the actual rotational speed becomes smaller than the target rotational speed. As a result, a difference occurs between the actual engine speed of the engine E and the target engine speed, and the engine speed deviation calculated by the engine speed difference calculator 32 becomes a negative value. The torque command calculation unit 33 calculates an engine torque command based on this rotational speed deviation, and the torque command calculation unit 33 calculates an engine torque command that increases in response to an increase in pump load (FIG. 4). (See times t1 to t4 in the graph of the engine torque command). The fuel injection amount calculation unit 34 calculates an actual fuel injection amount based on the calculated engine torque command and the actual rotational speed, and the fuel injection drive unit 35 further performs fuel injection based on the calculated actual fuel injection amount. The movement of the device 21 is controlled. As a result, the calculated actual fuel injection amount of fuel is injected from the fuel injection device 21.

  In the control device 30, the assist torque determination unit 36 determines the assist torque to be output from the electric motor 20, and the torque change estimation unit 37 calculates a torque reduction coefficient so as to estimate the change value of the output torque. That is, the assist torque determination unit 36 determines the assist torque based on the rotation speed deviation calculated by the rotation speed difference calculation unit 32. In the present embodiment, since the actual rotational speed is smaller than the target rotational speed and the rotational speed deviation is less than zero at times t1 to t2, the assist torque determining unit 36 sets the assist torque to a preset torque value (FIG. 4). (See times t1 to t2 in the assist torque graph).

  On the other hand, as shown in FIG. 3, in the torque change estimation unit 37, the time constant calculation unit 41 calculates the time constant from the actual rotational speed using the time constant map. Next, the pseudo differential calculation unit 42 calculates a differential value of the actual fuel injection amount from the actual fuel injection amount calculated by the fuel injection amount calculation unit 34 using the calculated time constant. The torque reduction coefficient calculation unit 43 calculates the absolute value of the differential value of the actual fuel injection amount, and the torque reduction coefficient calculation unit 43 uses the torque reduction coefficient map 43a to calculate the torque from the absolute value of the differential value of the actual fuel injection amount. Calculate the reduction factor. Since the calculated torque reduction 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 graph of the torque reduction coefficient in FIG. (See times t1 to t3 in the graph of the torque reduction coefficient in FIG. 4). Note that the calculated torque reduction coefficient is expressed as a positive value.

  In this way, 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 reduction coefficient calculation unit 43 calculates the change rate. Based on this, a reduction coefficient (that is, a reduction rate) of the output torque for each unit rotational 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 the time. Therefore, even after the actual rotational speed reaches the target rotational speed and the actual fuel injection amount becomes constant, the deterioration of the combustion state does not stop and the torque decreases, and the engine E performs a predetermined number of combustions (that is, the predetermined number of combustions). After the rotation is performed, 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. Further, by using the pseudo differentiation when calculating the rate of change of the actual fuel injection amount, the torque reduction coefficient becomes a value larger than zero even after the engine speed reaches the target speed. Thereafter, the torque reduction coefficient decreases toward zero (see times t2 to t3 in the graph of the torque reduction coefficient in FIG. 4). That is, the torque change estimation unit 37 takes into account the torque reduction coefficient after the engine speed reaches the target speed. Thus, since the rate of change of the output torque is calculated not in time units but in rotation speed units, the torque reduction coefficient can be estimated more accurately than in the case of calculation in time units.

  The correction coefficient calculator 38 calculates a correction coefficient from the torque reduction coefficient estimated by the torque change estimator 37 using the correction coefficient map 38a. In the present embodiment, the correction coefficient calculation unit 38 sets the correction coefficient to zero at times t1 to t11 and times t2 to t3 where the torque reduction coefficient is less than a predetermined threshold. On the other hand, at time t11 to t2 when the torque reduction coefficient is equal to or greater than the threshold value, the correction coefficient calculator 38 sets the correction coefficient to a predetermined value (= 1). The assist torque correction unit 39 corrects the assist torque based on the correction coefficient calculated in this way, and calculates an assist torque command. That is, the assist torque correction unit 39 calculates the assist torque command value by multiplying the assist torque by the correction coefficient. As a result, as shown in the assist torque command graph of FIG. 4, the assist torque command is calculated as a value of zero or more at time t11 to time t2, and the drive control unit 40 is connected to the inverter 22 based on the calculated assist torque command. To control the movement. Thus, at time t11 to time t2, torque corresponding to the assist torque command is output from the electric motor 20, and the engine E is assisted.

  Thus, the hydraulic pump drive system 1 calculates the correction coefficient based on the estimated torque reduction coefficient, corrects the assist torque using this correction coefficient, and calculates the assist torque command. Therefore, an assist torque command corresponding to the torque reduction coefficient is calculated, and the movement of the electric motor 20 can be controlled according to the decrease in the torque of the engine E. That is, when the torque reduction coefficient is small as in this embodiment, the movement of the electric motor 20 is stopped (see times t1 to t11), and when the torque reduction coefficient is large, the motor E can assist the engine E (time). t11 to t2). When the torque reduction coefficient is small, the change in the fuel injection amount is small, and the combustion state of the engine E is relatively stable. In such a stable state, the effect of suppressing the torque change of the engine E by the electric motor 20 is small, so that the electric power stored in the battery 24 can be prevented from being wasted by stopping the electric motor 20. That is, the power consumption consumed by the electric motor 20 can be reduced. On the other hand, when the torque reduction coefficient is large, the change in the fuel injection amount is large, and the combustion state of the engine E is unstable. In such an unstable state, assisting the engine E with the electric motor 20 can stabilize the combustion state, and improve fuel efficiency.

  Next, when the operation of the operation tool is stopped (that is, the operation tool is returned to the neutral position), the hydraulic pump 17 is switched from the on-load state to the unload state, and the load on the hydraulic pump 17 is reduced (that is, A description will be given of when load is lost. 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 increases (see times t4 to t5 in the graph of the engine rotational speed in FIG. 4), and the actual rotational speed becomes larger than the target rotational speed. As a result, a difference occurs between the actual rotational speed of the engine E and the target rotational speed, and the rotational speed deviation calculated by the rotational speed difference calculation unit 32 becomes a positive value. The torque command calculation unit 33 calculates an engine torque command based on the calculated rotation speed deviation. Then, an engine torque command that is decreased in response to a decrease in pump load is calculated by the torque command calculation unit 33 (see times t4 to t5 in the graph of the engine torque command in FIG. 4). The fuel injection amount calculation unit 34 calculates the actual fuel injection amount based on the calculated engine torque command and the actual rotational speed. The fuel injection drive unit 35 controls the movement of the fuel injection device 21 based on the actual fuel injection amount calculated by the fuel injection amount calculation unit 34. Thereby, the calculated fuel injection amount of fuel is injected from the fuel injection device 21.

  Further, in the control device 30, the assist torque determination unit 36 determines the assist torque based on the rotation speed deviation calculated by the rotation speed difference calculation unit 32. In this embodiment, since the actual rotational speed is larger than the target rotational speed and the rotational speed deviation is zero or more from time t4 to time t5, the assist torque determination unit 36 sets the assist torque to zero (the assist torque graph in FIG. 4). (See time t4 to t5). For this reason, the assist torque command calculated by the assist torque correction unit 39 becomes zero regardless of the torque reduction coefficient estimated by the torque change estimation unit 37. That is, in the hydraulic pump drive system 1, the motor 20 is not operated to reduce the actual rotational speed of the engine E to the target rotational speed when the load is lost, specifically, the regenerative operation is not performed. Since the electric motor 20 is not regeneratively operated when the load is lost, it is possible to avoid a low energy efficiency situation in which the regenerative operation is performed by the electric motor 20 while consuming excess fuel in the engine E, and fuel efficiency can be improved. .

  Note that the assist torque determination unit 36 of the control device 30 does not necessarily need to set the assist torque to zero when the rotational speed deviation is not less than zero. For example, when the rotational speed deviation becomes zero or more, the assist torque determination unit 36 sets a predetermined regenerative braking torque, that is, a predetermined negative torque value, as the assist torque. Then, as shown at times t6 to t7 in the assist torque graph of FIG. 5, the assist torque determination unit 36 sets the assist torque to a negative torque value when the load is released. The assist torque is corrected by the assist torque correction unit 39 using a correction coefficient. The correction coefficient becomes zero at times t6 to t61 when the torque reduction coefficient becomes less than the threshold, and becomes a predetermined value (= 1) at times t61 to t7 when the torque reduction coefficient becomes equal to or greater than the threshold (torque reduction in FIG. 5). See the coefficient graph). Therefore, the assist torque command calculated by the assist torque correction unit 39 becomes zero at times t6 to t61 and becomes a negative value (that is, regenerative braking torque command) at times t61 to t7. Thereby, the electric motor 20 comes to perform a regenerative operation, and the actual rotational speed that has increased when the load is released can be quickly reduced to the target rotational speed.

Second Embodiment
The hydraulic pump drive system 1A of the second embodiment is similar in configuration to the hydraulic pump drive system 1 of the first embodiment. Below, about the hydraulic pump drive system 1A, only a different structure from the structure of the hydraulic pump drive system 1 of 1st Embodiment is demonstrated, and description is abbreviate | omitted about the same structure.

  In the hydraulic pump drive system 1A, the fuel injection amount calculation unit 34A of the control device 30A shown in FIG. 6 increases or decreases while limiting the rate of change of the actual fuel injection amount. More specifically, as shown in FIG. 7, the fuel injection amount calculation unit 34 </ b> A has a target fuel injection amount calculation part 51 and an injection amount restriction part 52. The target fuel injection amount calculation part 51 calculates a target fuel injection amount that is a target fuel injection amount to be injected from the fuel injection device 21 based on the engine torque command calculated by the torque command calculation unit 33 and the actual rotational speed. To do. This target fuel injection amount is used in the injection amount restriction portion 52.

  The injection amount limiting portion 52 has a rate limit function with an increase rate limitation and without a decrease rate limitation, and the actual fuel injection amount is calculated based on the target fuel injection amount by this rate limit function. . That is, when the target fuel injection amount increase rate exceeds a predetermined value when the target fuel injection amount is increased, the injection amount limiting portion 52 performs an actual operation while limiting the change rate or the change amount based on a predetermined change rule. The fuel injection amount is changed stepwise up to the target fuel injection amount. On the other hand, when the target fuel injection amount decreases, the injection amount restriction portion 52 sets the target fuel injection amount as the actual fuel injection amount without restricting the reduction rate.

  More specifically, the injection amount restriction portion 52 holds (ie, stores) the target fuel injection amount calculated by the target fuel injection amount calculation portion 51 inside, and immediately after the held target fuel injection amount. The target fuel injection amount calculated in the above 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 portion 52 may be a filter. For example, the target fuel injection amount may be increased based on a transfer function having a first-order lag element (that is, a lag element). In the fuel injection drive unit 35 and the torque change estimation unit 37, the actual fuel injection amount calculated in this way is used.

  The control device 30 </ b> A further includes a target torque calculator 53, an actual torque calculator 54, and a differential torque calculator 55. The target torque calculation unit 53 calculates a target torque based on the target fuel injection amount calculated by the target fuel injection amount calculation part 51 of the fuel injection amount calculation unit 34A and the actual rotational speed. The target torque is a torque output from the engine E when the target fuel injection amount is injected. The target torque calculator 53 will be described in more detail. The target torque calculator 53 has a target torque map, and the target torque map associates the target torque with the target fuel injection amount and the actual rotational speed. It is a map. The target torque calculator 53 calculates the target torque from the target torque map based on the calculated target fuel injection amount and the actual rotational speed.

  Further, the actual torque calculation unit 54 calculates the actual torque based on the actual fuel injection amount calculated by the injection amount limiting portion 52 of the fuel injection amount calculation unit 34A and the actual rotational speed. The actual torque is a torque output from the engine E when the actual fuel injection amount is injected. More specifically, the actual torque calculation unit 54 has an actual torque map, and 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. The actual torque calculator 54 calculates the actual torque from the actual torque map based on the calculated actual fuel injection amount and the actual rotation speed. The actual torque calculated in this way is used by the differential torque calculator 55 together with the target torque.

  The differential torque calculator 55 calculates a differential torque that is a shortage of torque obtained by subtracting the actual torque from the target torque. The calculated differential torque is added to the assist torque command by the drive control unit 40A. The drive control unit 40A controls the movement of the inverter 22 so that the motor 20 outputs a torque obtained by adding the differential torque to the assist torque command.

  Thus, in the hydraulic pump drive system 1A, the increase rate of the actual fuel injection amount is limited when the target fuel injection amount suddenly increases. By limiting the increase rate in this way, it is possible to prevent instability 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, an insufficient differential torque is generated, the shortage can be output to the electric motor 20. Thereby, it can prevent that the rotation speed of the engine E accompanying torque shortage falls too much.

  In addition, the hydraulic pump drive system 1A has the same effects as the hydraulic pump drive system 1 of the first embodiment.

<Other embodiments>
In the hydraulic pump drive systems 1 and 1A of the present embodiment, the correction coefficient calculated by the correction coefficient calculation unit 38 is selected from two values of zero or a predetermined value (= 1). However, such a configuration is not necessarily required. For example, the assist determination unit 44 may change the correction coefficient according to the torque reduction coefficient when the torque reduction coefficient estimated by the torque change estimation unit 37 is greater than or equal to a threshold value. Further, when the correction coefficient calculation unit 38 calculates the correction coefficient, a predetermined value may be changed according to the charge amount of the battery 24 detected based on the signal output from the voltage sensor 25. Good. For example, when the charge amount of the battery 24 decreases, the predetermined value is made smaller than 1. Thereby, it is possible to prevent a large current from flowing in the inverter 22.

  In the hydraulic pump drive system 1, 1 </ b> A of the present embodiment, a change in the torque of the engine E per unit speed (for example, torque per speed) is changed by changing the time constant of pseudo differentiation based on the actual speed. The rate is calculated in a pseudo manner. In addition to this method, it is also possible to actually calculate the pseudo-differentiation for each unit rotation speed and actually obtain the torque change rate for each unit rotation. That is, as the actual rotational speed increases, the interval for calculating the torque change rate becomes shorter, and as the actual rotational speed decreases, the interval for calculating the torque change rate becomes longer. Thereby, the rate of change of torque per unit rotation speed can be estimated. The torque change estimation unit 37 is not limited to the estimation method as described above, but may be any method that can estimate a reduction coefficient of the output torque of the engine E due to a change in the actual fuel injection amount.

  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.

E Engine 1, 1A Hydraulic pump drive system 17 Hydraulic pump 17a Rotating shaft 20 Electric motor 23 Rotational speed sensor 24 Battery (capacitor)
25 Voltage sensor (charge storage sensor)
30, 30A Control device 31 Target speed determination unit 32 Speed difference calculation unit 33 Torque command calculation unit 34, 34A Fuel injection amount calculation unit 36 Assist torque determination unit 37 Torque change estimation unit 38 Correction coefficient calculation unit 39 Assist torque correction unit 40, 40A Drive control unit 41 Time constant calculation unit 42 Pseudo-differentiation calculation unit 44 Assist determination unit 51 Target fuel injection amount calculation part 52 Injection amount restriction part 53 Target torque calculation part 54 Actual torque calculation part 55 Differential torque calculation part

Claims (7)

An engine that rotationally drives the rotary shaft of the hydraulic pump;
An electric motor that receives power supply to rotationally drive the rotating shaft and assist the engine;
A rotational speed sensor for detecting the actual rotational speed of the rotary shaft;
A controller that determines a fuel injection amount of the engine and controls movement of the electric motor,
The control device includes a torque command calculation unit, a fuel injection amount calculation unit, a torque change estimation unit, an assist torque determination unit, an assist determination unit, and a drive control unit,
The torque command calculation unit is an engine torque that is output to the engine based on a rotational speed deviation that is a deviation between the actual rotational speed and the target rotational speed so as to return the actual rotational speed to a predetermined target rotational speed. Calculate the engine torque command,
The fuel injection amount calculation unit calculates an actual fuel injection amount to be injected by the engine based on an engine torque command calculated by the torque command calculation unit and the actual rotational speed,
The torque change estimation unit estimates a change value of the output torque of the engine based on the actual fuel injection amount calculated by the fuel injection amount calculation unit and the actual rotational speed,
The assist torque determination unit determines an assist torque to be output to the electric motor based on the rotation speed deviation,
The assist determination unit sets the assist torque command to zero when the change value of the output torque estimated by the torque change estimation unit is less than a predetermined positive threshold, and the change value of the output torque is the positive value. When the torque is equal to or greater than the threshold value, the torque corresponding to the assist torque is set as an assist torque command.
The drive control unit is a hydraulic pump drive system that outputs an assist torque command determined by the assist determination unit from the electric motor.   The assist torque determining unit sets the assist torque to zero when the rotational speed deviation, which is a value obtained by subtracting the target rotational speed from the actual rotational speed, is zero, and when the rotational speed deviation is less than zero, 2. The hydraulic pump drive system according to claim 1, wherein the assist torque is set to a preset torque value.   The hydraulic pump drive system according to claim 2, wherein the preset torque value in the assist torque determining unit is a torque that the electric motor can output with an efficiency of 80% or more and 95% or less. The assist determination unit includes a correction coefficient calculation unit and an assist torque correction unit,
The correction coefficient calculation unit sets the correction coefficient to zero when the change in the output torque estimated by the torque change estimation unit is less than the predetermined threshold, and when the change in the output torque is equal to or greater than the threshold. A predetermined positive value,
The hydraulic pump according to any one of claims 1 to 3, wherein the assist torque correction unit calculates the assist torque command by correcting the assist torque using a correction coefficient calculated by the correction coefficient calculation unit. Drive system. A power storage amount sensor that detects a power storage amount of a battery that supplies power to the electric motor;
The hydraulic pump drive system according to claim 4, wherein the assist determination unit is configured to reduce the correction coefficient in accordance with a decrease in the storage amount detected by the storage amount sensor. . 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 calculation that changes the time constant of the first-order lag element according to the actual rotation speed detected by the rotation speed sensor. And calculating a rate of change of the actual fuel injection amount per unit rotational speed of the engine using pseudo differentiation, and based on the rate of change of the actual fuel injection amount per unit rotational speed of the engine The hydraulic pump drive system according to claim 1, wherein a change in the output torque is estimated. The fuel injection amount calculation unit has a target fuel injection amount calculation part and an injection amount restriction part,
The target fuel injection amount calculation part calculates a target fuel injection amount that is a target based on the engine torque command calculated by the torque command calculation unit and the actual rotational speed,
The injection amount restriction portion gradually reduces the actual fuel injection amount to the target fuel injection amount when calculating the actual fuel injection amount based on the target fuel injection amount calculated in the target fuel injection amount calculation portion. Having the function of increasing, determining the actual fuel injection amount so that the time change rate of the actual fuel injection amount when increasing is less than a predetermined value,
The control device includes an actual torque calculation unit, a target torque calculation unit, and a differential 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 determined by the injection amount restriction portion;
The target torque calculation unit is a target torque to be output to the engine based on the actual rotation speed detected by the rotation speed sensor and the target fuel injection amount calculated by the target fuel injection amount calculation part. Calculate the target torque,
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,
7. The hydraulic pump according to claim 1, wherein the drive control unit causes the electric motor to output a torque obtained by adding the differential torque calculated by the differential torque calculation unit to the assist torque command. 8. Driving system.