JP5279660B2 - Hybrid work machine and control method thereof - Google Patents

Description

  The present invention relates to a hybrid work machine that drives a drive system using power generated by an engine and stored electrical energy, and a control method thereof.

  In the hybrid work machine, the engine speed is arbitrarily set by an operator, for example. However, if the engine speed is arbitrarily set by the operator, depending on the operating conditions (load conditions) of the work machine, the state of charge (SOC) of the power storage device will drop and the power will be insufficient, and the operator will In some cases, the user cannot satisfy the operation.

  A technique for controlling the engine speed in real time in accordance with the SOC value is known.

  A conventional example of the engine speed control method will be described with reference to FIG. The upper stage, middle stage, and lower stage in the figure show time changes in load output, SOC, and engine speed, respectively. The load output is displayed in the unit “kW”, the SOC is displayed in the unit “%”, and the engine speed is displayed in the unit “rpm”. Time is expressed in units of seconds.

At time _{t 2} from time _{t 1,} an increase in the load output SOC decreases due. SOC at time _{t 2,} reaches its threshold.

Referring to the range of time _{t 3} from the time _{t 2.} When the SOC is smaller than the threshold value, the engine speed is increased, the motor generator (assist motor) performs a power generation operation, and the generated electric energy is stored in the power storage device, thereby increasing the SOC increase rate. Control to increase is performed. Thus, at time t ₃ SOC is a small time t ₂ than the threshold, as shown in the figure the lower the engine speed increases. As a result, the slope (dSOC / dt) of the time change graph of the SOC increases, and the decrease in the SOC is suppressed.

At time t ₄ from time t _3, the decrease in the load output, the power generation amount in the electric generator, and the electrical energy stored in the power storage device is increased, SOC is increased. The engine speed decreases as the SOC increases. At time _{t 4,} SOC is restored to the threshold, the engine speed is also normal (time _{t 2} previously) returns to it.

At time t ₅ after the load output began to increase again, SOC becomes equal to the threshold again, the engine speed starts to increase. Even after time t _5, the working machine is operated at high load output, at time t ₆ after a short time from the time t _5, a smaller operating state of rapid load output. SOC continued to decrease at time _{t 6} from the time _{t 5,} at time _{t 6,} SOC takes a minimum value. Engine speed increases with decrease in SOC, the maximum value within the control range at the time t _6.

At time t ₇ from the time t _6, a possible load output is small, by a large engine speed, SOC is restored at a high growth rate. As the SOC recovers, the engine speed decreases. SOC is restored to the threshold at time t _7, the engine speed also returns to its normal time.

  In the engine speed control method according to the conventional example, the engine speed is changed in real time depending on the SOC. For this reason, the operator feels uncomfortable and the operability of the work machine deteriorates.

Further, for example, in the above example, for increasing the load output from the time t ₅ in a short period of time t _6, since the load output at time t ₆ after is small, even without increasing the engine speed, usually at a rotational speed of time, at a time after the time t _7, it is considered that can recover the SOC until greater than a threshold value. As described above, in the conventional engine speed control method, even if a shortage of power due to a decrease in SOC can be avoided in a series of operations, it cannot be said that an appropriate engine speed is realized in the long term. Efficient engine operation is difficult.

  An invention of a power source device for a work machine that makes the engine speed variable according to the SOC or temperature of the power storage device is disclosed (see, for example, Patent Document 1). When the SOC is low and at a low temperature, the maximum discharge output of the power storage device decreases. In the invention described in Patent Document 1, in such a case, the engine speed is increased, the insufficient power is supplied, or the power storage device is charged to raise the SOC.

JP 2005-233164 A

  An object of the present invention is to provide a hybrid work machine capable of operating an engine efficiently and a control method thereof.

According to one aspect of the present invention,
An engine that generates power,
A motor that is connected to the engine and performs an electric operation, and a motor generator that functions as a generator that performs a power generation operation, so that the power generated by the engine can be transmitted;
When the motor generator functions as a motor, power is supplied to the motor generator, and when the motor generator functions as a generator, a capacitor is supplied with power from the motor generator;
A hydraulic load driven by at least the power generated by the engine; and
An electric load driven by being supplied with power from at least the capacitor;
A control device for controlling the rotational speed of the engine,
The controller controls the engine speed in a second period following the first period based on a temporal change or energy of power supplied to the hydraulic load and the electric load in the first period. There is provided a hybrid work machine that determines a target value of the motor and controls the rotational speed so as to be the determined target value.

According to another aspect of the invention,
An engine that generates power, an electric motor that is connected to the engine and that performs an electric operation so that the power generated by the engine can be transmitted, and a motor generator that functions as a generator that performs an electric power generation operation; and When the motor generator functions as a motor, power is supplied to the motor generator. When the motor generator functions as a generator, the capacitor is supplied with power from the motor generator, and is generated at least in the engine. A control method of a hybrid work machine having a hydraulic load driven by being supplied with power and an electric load driven by being supplied with power from at least the capacitor,
(A) grasping time change or energy of power supplied to the hydraulic load and the electric load in the first period;
(B) determining a target value of the engine speed in the second period following the first period based on the time change or energy of the power grasped in the step (a);
And (c) controlling the engine speed so that the engine speed in the second period becomes the target value determined in the step (b). A method is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the hybrid type work machine in which efficient engine operation is possible, and its control method can be provided.

The side view of the hybrid type working machine by an Example is shown. The block diagram of a hybrid type work machine is shown. The internal block diagram of the electrical storage circuit 120 is shown. It is a figure for demonstrating the control method of the hybrid type working machine by an Example. It is a figure for demonstrating the control method of the hybrid type working machine by an Example. It is a figure for demonstrating the control method of the hybrid type working machine by an Example. 3 is a functional block diagram of a CPU 30A included in the control device 30. FIG. It is a figure for demonstrating the prior art example of an engine speed control method.

  FIG. 1 shows a side view of a hybrid work machine according to an embodiment. An upper swing body 3 is mounted on the lower traveling body (base body) 1 via a swing mechanism 2. The turning mechanism 2 includes an electric motor (motor), and turns the upper turning body 3 clockwise or counterclockwise. A boom 4 is attached to the upper swing body 3. The boom 4 swings up and down with respect to the upper swing body 3 by a hydraulically driven boom cylinder 7. An arm 5 is attached to the tip of the boom 4. The arm 5 swings in the front-rear direction with respect to the boom 3 by an arm cylinder 8 that is hydraulically driven. A bucket 6 is attached to the tip of the arm 5. The bucket 6 swings up and down with respect to the arm 5 by a hydraulically driven bucket cylinder 9. The upper swing body 3 further includes a cabin 10 that accommodates a driver.

  FIG. 2 shows a block diagram of the hybrid work machine. In FIG. 2, the mechanical power system is represented by a double line, the high-pressure hydraulic line is represented by a thick solid line, the electric system is represented by a thin solid line, and the pilot line is represented by a broken line.

  The drive shaft of the engine 11 is connected to the input shaft of the transmission 13. As the engine 11, an engine that generates a driving force by a fuel other than electricity, for example, an internal combustion engine such as a diesel engine is used. The engine 11 is always driven during operation of the work machine. The rotation speed of the engine 11 is controlled by a command value issued from the control device 30.

  The drive shaft of the motor generator 12 is connected to the other input shaft of the transmission 13. The motor generator 12 can perform both the electric (assist) operation and the power generation operation. As the motor generator 12, for example, an internal permanent magnet (IPM) motor in which a magnet is embedded in a rotor is used.

  The transmission 13 has two input shafts and one output shaft. A drive shaft of the main pump 14 is connected to the output shaft. Further, an angular velocity detector 130 for detecting the angular velocity of the output shaft is installed on the output shaft. The angular velocity of the output shaft detected by the angular velocity detector 130 is input to the control device 30.

  When the load on the main pump 14 is large, the motor generator 12 performs an assist operation, and the driving force of the motor generator 12 is transmitted to the main pump 14 via the transmission 13. Thereby, the load applied to the engine 11 is reduced. On the other hand, when the load on the main pump 14 is small, the driving force of the engine 11 is transmitted to the motor generator 12 via the transmission 13, so that the motor generator 12 is operated for power generation. Switching between the assist operation and the power generation operation of the motor generator 12 is performed by an inverter 18 connected to the motor generator 12. The inverter 18 is controlled by the control device 30.

  The control device 30 includes a central processing unit (CPU) 30A and an internal memory 30B. The CPU 30A executes a drive control program stored in the internal memory 30B. The control device 30 alerts the driver by displaying the deterioration state of various devices on the display device 35.

  The main pump 14 supplies hydraulic pressure to the control valve 17 via the high pressure hydraulic line 16. The control valve 17 distributes hydraulic pressure to the hydraulic motors 1A, 1B, the boom cylinder 7, the arm cylinder 8, and the packet cylinder 9 in accordance with a command from the driver. The hydraulic motors 1A and 1B each generate a driving force for driving the lower traveling body shown in FIG. The high-pressure hydraulic line 16 is provided with a flow meter 131 that measures the flow rate of oil discharged from the main pump 14 and flowing through the high-pressure hydraulic line 16. The flow rate of oil measured by the flow meter 131 is input to the control device 30.

  The input / output terminal of the electric system of the motor generator 12 is connected to the DC bus line of the storage circuit 120 via the inverter 18. The DC bus line of the storage circuit 120 is connected to the turning electric motor 21 via another inverter 20. An ammeter 132 is disposed between the DC bus line of the storage circuit 120 and the inverter 20. The current value measured by the ammeter 132 is input to the control device 30.

  The turning electric motor 21 is AC driven by a pulse width modulation (PWM) control signal from the inverter 20 and can perform both a power running operation and a regenerative operation. For example, an IPM motor is used as the turning electric motor 21.

  During the power running operation of the turning electric motor 21, the rotational force of the turning electric motor 21 is transmitted to the turning mechanism 2 shown in FIG. 1 through the transmission 24. At this time, the transmission 24 reduces the rotation speed. As a result, the rotational force generated by the turning electric motor 21 increases and is transmitted to the turning mechanism 2. Further, during the regenerative operation, the rotational motion of the upper swing body 3 is transmitted to the turning electric motor 21 via the transmission 24, so that the turning electric motor 21 generates regenerative electric power. At this time, the transmission 24 increases the rotational speed, contrary to the power running operation. Thereby, the rotation speed of the electric motor 21 for rotation can be raised.

  The resolver 22 detects the position of the rotation shaft of the turning electric motor 21 in the rotation direction. The detection result is input to the control device 30.

  A mechanical brake 23 is connected to the rotating shaft of the turning electric motor 21 and generates a mechanical braking force. The mechanical brake 23 receives a command from the control device 30 and is switched between a braking state and a release state by an electromagnetic switch.

  The pilot pump 15 generates a pilot pressure necessary for the hydraulic operation system. The generated pilot pressure is supplied to the operating device 26 via the pilot line 25. The operating device 26 includes a lever and a pedal and is operated by a driver. The operating device 26 converts the primary side hydraulic pressure supplied from the pilot line 25 into a secondary side hydraulic pressure in accordance with the operation of the driver. The secondary side hydraulic pressure is transmitted to the control valve 17 via the hydraulic line 27 and to the pressure sensor 29 via the other hydraulic line 28.

  The detection result of the pressure detected by the pressure sensor 29 is input to the control device 30. Thereby, the control apparatus 30 can detect the operation state of the lower traveling body 1, the turning mechanism 2, the boom 4, the arm 5, and the bucket 6.

  FIG. 3 shows an internal configuration diagram of the power storage circuit 120. The power storage circuit 120 includes the converter 100, the DC bus line 110, and the capacitor 19. Converter 100 controls the voltage of DC bus line 110 to be a constant value. The DC bus line 110 includes a smoothing capacitor 105.

  The capacitor 19 is connected to the pair of power supply connection terminals 103A and 103B of the converter 100, and the smoothing capacitor 105 of the DC bus line 110 is connected to the pair of output terminals 104A and 104B. One power connection terminal 103B and one output terminal 104B are grounded.

  The DC bus line 110 is connected to the motor generator 12 and the turning electric motor 21 via inverters 18 and 20.

  During the period in which the motor generator 12 is generating, the electric power generated by the motor generator 12 is supplied to the capacitor 19 via the inverter 18 and the capacitor 19 is charged. During the period in which the motor generator 12 is being assisted, necessary power is supplied from the capacitor 19 to the motor generator 12 via the inverter 18.

  Electric power is supplied from the capacitor 19 to the turning electric motor 21. Further, the regenerative power generated by the turning electric motor 21 is stored in the capacitor 19.

  The voltage generated at both ends of the smoothing capacitor 105 is measured by the voltmeter 111, and the measurement result is input to the control device 30.

  A series circuit in which a collector of a boosted insulated gate bipolar transistor (IGBT) 102A and an emitter of a step-down IGBT 102B are connected to each other is connected between output terminals 104A and 104B. . The emitter of the step-up IGBT 102A is grounded, and the collector of the step-down IGBT 102B is connected to the output terminal 104A on the high voltage side. An interconnection point between the step-up IGBT 102A and the step-down IGBT 102B is connected to the high-voltage side power supply connection terminal 103A via the reactor 101.

  Diodes 102a and 102b are connected in parallel to the step-up IGBT 102A and the step-down IGBT 102B, respectively, such that the direction from the emitter to the collector is the forward direction.

  A voltmeter 106 connected between the power connection terminals 103A and 103B measures the voltage across the terminals of the capacitor 19, and the current SOC (charge rate) of the capacitor 19 is calculated based on the measured voltage. An ammeter 107 inserted in series with the reactor 101 measures the charge / discharge current of the capacitor 19. The measurement results of voltage and current are input to the control device 30.

  The control device 30 performs pulse width modulation (PWM) control on the gate voltages of the step-up IGBT 102A and the step-down IGBT 102B so that the voltage of the DC bus line 110 becomes a constant value.

  Hereinafter, the boosting operation (discharging operation) will be described. When the voltage of the DC bus line 110 decreases, a part of the energy of the capacitor 19 is stored in the reactor 101 by PWM control of the gate voltage of the boosting IGBT 102A, and to the DC bus line 110 via the diode 102b. , The voltage of the DC bus line 110 rises.

  Next, the step-down operation (charging operation) will be described. When the voltage of the DC bus line 110 increases, the gate voltage of the step-down IGBT 102B is PWM-controlled so that the energy of the DC bus line 110 flows into the capacitor 19 and the voltage of the DC bus line 110 decreases.

  With reference to FIGS. 4-6, the control method of the hybrid type working machine by an Example is demonstrated.

  Please refer to FIG. The upper stage, the middle stage, and the lower stage of FIG. 4 show changes over time in the load output (load request output) of the work machine, the SOC of the storage circuit 120 (capacitor 19), and the rotational speed of the engine 11, respectively. The load output is displayed in the unit “kW”, the SOC is displayed in the unit “%”, and the engine speed is displayed in the unit “rpm”. Time is expressed in units of seconds.

Time T ₁ to Time T ₂ are the first period from the start of work, Time T ₂ to Time T ₃ are the second period, Time T ₃ to Time T ₄ are the third period, and Time T ₄ to Time T ₅ are the fourth period Period. The length of each period is equal to T _cyc , and T _cyc is several tens of _minutes, for example. This figure shows a case where the load output waveforms in the first period and the second period are equal and the load output waveforms in the third period and the fourth period are equal. The period length can be arbitrarily set by the operator, for example, according to the work content.

The load output (load request output) will be described with reference to FIG. The upper stage, middle stage, and lower stage of FIG. 5 are graphs showing temporal changes in hydraulic output (hydraulic demand output) P _Hyd , electrical output (electrical demand output) P _Elc , and load output (load demand output), respectively. The horizontal axis of the graph indicates time in the unit “second”, and the vertical axis indicates each output in the unit “kW”.

The hydraulic output (hydraulic demand output) P _Hyd is energy (power) per unit time supplied to the hydraulic load. The hydraulic load is a component driven by hydraulic pressure, and includes the boom cylinder 7, the arm cylinder 8, the packet cylinder 9, and the hydraulic motors 1A and 1B shown in FIG.

The electric output (electric demand output) P _Elc is energy (power) per unit time supplied to the electric load. The electric load is a component driven by electric power, and includes the turning electric motor 21 shown in FIG.

The load output (load required output) is the energy (power) per unit time supplied to the entire load of the work machine, and is the hydraulic output (hydraulic required output) P _Hyd and the electric output (electrically required output) P _Elc . Expressed in sum.

Time variation of the hydraulic output is represented by the graph shown in the upper part of FIG at time t _{s ~} time t _e, when the time change in the electrical output is represented by a graph shown in the middle figure of load output changes thereof The sum is represented by the graph shown in the lower part of the figure. In the graph of the output change shown in this figure, regenerative power is generated at the time when the output is negative.

The average load output _{P Ave} at time _{t s} ~ time _{t e} is defined by the following equation (1).

(Equation 1)

  here,

(Equation 2)
_{T cyc} = _t e -t _s
It is. The average load output _{P Ave} is a value that indicates the average of the load output during the period defined by the time _{t s} ~ time _{t e.} In the lower graph of this figure, the average load output P _Ave is indicated by a two-dot chain line.

Since the time _{t s} is the time of the beginning of the period, the time _{t e} indicating the time of the end of the period, for example, when the _{t s} to the _T 1, _{t e} and _{T 2,} the formula (1) is, in FIG. 4 The average value of the load output in the first period is shown.

Reference is again made to FIG. In the control method of the hybrid work machine according to the embodiment, the engine in the (n + 1) period is based on the load output of the n period (n is a natural number) and the SOC of the power storage circuit 120 at the end time of the n period. The required output P _EngReq is calculated, and based on this, the target value of the rotational speed of the engine 11 in the (n + 1) period is determined. Calculation of the engine required output P _EngReq and determination of the target value of the rotation speed of the engine 11 are performed by the control device 30. After the target value of the rotational speed is determined, the control device 30 controls the rotational speed of the engine 11 so that the rotational speed of the engine 11 becomes the determined target value.

First, an average load output P _Ave for the nth period is obtained based on the load output for the nth period. The average load output _{P Ave} of the n period may be determined using the following equation obtained by replacing _{t s} of formula (1) _T n, a _{t e} to _{T n + 1} (3).

(Equation 3)

  here,

(Equation 4)
T _cyc = T _{n + 1} −T _n
It means the time length of the nth period.

Next, the required charge / discharge output P _Bat in the (n + 1) period is calculated based on the SOC of the power storage circuit 120 (capacitor 19) at the end time of the n period. In calculating the required charge / discharge output P _Bat , first, the required charge / discharge amount E _Bat in the (n + 1) period is obtained.

The required charge / discharge amount E _Bat can be obtained from the difference between the SOC target value SOC _Ref and the measured value SOC _Mes of the SOC at the end time of the n-th period by the following equation (5).

(Equation 5)
E _Bat = (SOC _Ref -SOC _Mes ) × E _BatFull
Here, E _BatFull is energy when the power storage circuit 120 (capacitor 19) is fully charged, and is a value specific to the power storage circuit 120 (capacitor 19). Further, the SOC target value SOC _Ref is a constant value that tends to bring the SOC of the power storage circuit 120 (capacitor 19) closer to it. In the middle part of FIG. 4, the SOC target value SOC _Ref is indicated by a dotted line. Incidentally, in this figure middle _row, examples of _{SOC Mes, SOC T2} the SOC at end time _{T 2} of the first period, _{SOC T3} the SOC at end time _{T 3} of the second period, the end time _{T 4} of the third period the SOC in the _{SOC T4,} the SOC at the end time _{T 5} of the fourth period was marked with the _{SOC T5.}

The required charge / discharge output P _Bat in the (n + 1) period is calculated using the required charge / discharge amount E _Bat in the (n + 1) period.

(Equation 6)
P _Bat = E _Bat / T _cyc
Is calculated by In the above equation (6), T _cyc means the time length of the (n + 1) period.

From the average load output P _Ave in the nth period and the required charge / discharge output P _Bat in the (n + 1) period, the engine required output P _EngReq in the (n + 1) period is calculated by the following equation (7).

(Equation 7)
P _EngReq = P _Ave + P _Bat
The engine request output P _EngReq is an average value (average target output) of the engine output P _Eng expected for the engine 11 in the (n + 1) period. As understood from the equation (7), in the hybrid work machine control method according to the embodiment, the engine required output P _EngReq of the engine 11 in the (n + 1) period is _expressed as the average load output P _{Ave in} the n period. The SOC at the end time of the n-th period is a value represented by the sum of the charge / discharge output P _Bat necessary for returning to the target value SOC _Ref in the (n + 1) -th period.

Based on the load output of the nth period and the SOC of the power storage circuit 120 (capacitor 19), the engine required output P _EngReq in the (n + 1) period is set to the value represented by the equation (7), so that the (n + 1) period , The necessary power can be supplied when the operation (load output) is the same as that in the nth period, and the SOC can be returned to the target value at the end of the (n + 1) period.

FIG. 6 is an iso-fuel consumption diagram of the engine 11. In the figure, the horizontal axis indicates the number of revolutions of the engine 11 in the unit “rpm”, and the vertical axis indicates the torque generated by the engine 11 in the unit “N · m”. In this figure, three equal fuel consumption lines α to γ are shown. The fuel consumption on the iso-fuel consumption line α is high and the fuel consumption on the iso-fuel consumption line γ line is low. The fuel consumption on the equal fuel consumption line β takes an intermediate value. Here, the fuel consumption refers to a fuel consumption amount required per unit work, and is represented by a unit “g / kWh”. Curve T _Max shows the engine speed dependency of the maximum value of torque that can be generated.

When the engine request output P _EngReq in the (n + 1) period is calculated by the equation (7), the rotational speed of the engine 11 in the (n + 1) period is determined. The engine output P _Eng [W] is obtained by the following equation (8) using the engine speed N [rpm] and the torque T [N · m] generated by the engine.

(Equation 8)
P _Eng = 2 × π × T × N / 60
As can be seen from Equation (8), the rotational speed N that generates a constant engine output P _Eng and the torque T are in an inversely proportional relationship. A curve indicating the relationship between the rotational speed N and the torque T that generates a constant engine output P _Eng is referred to as an equal horsepower line. In the iso-fuel consumption diagram of FIG. 6, equal horsepower lines δ1 to δ3 are indicated by alternate long and short dash lines. Equal horsepower line δ1 represents the relationship between the rotational speed N and the torque T to generate a large engine output E _1, equal horsepower line δ3 represent it to generate a smaller engine output E _3. Equal horsepower line δ2 indicates the relationship between the rotational speed N and the torque T to generate an intermediate of the engine output E _2. In addition, _NBfr in the figure indicates the rotational speed of the engine 11 in the n-th period.

For example, when the calculated engine request output P _EngReq in the (n + 1) period is E _{2 according} to the equation (7), the engine speed N _Aft of the engine 11 in the (n + 1) period is within a range not exceeding T _Max . The rotational speed at which the fuel consumption is lowest (good) on the equal horsepower line δ2. The target value of the engine speed determined in this _way is represented as N _AfterBest in this drawing. The target value rotational speed of the engine _11, based on the _{N AftBest,} it is also possible to determine the different and _{N AftBest} value.

Three times, refer to FIG. In the first period from time T ₁ to time T ₂ , the engine 11 is operated at the rotation speed of the initial value y [rpm]. In determining the target value of the engine 11 rotational speed in the second period from time T ₂ to time T ₃ , first, the load output (the sum of the hydraulic output P _Hyd and the electric output P _Elc ) in the first period, and the first Based on the SOC of power storage circuit 120 at the end time of the period, engine request output P _EngReq for the second period is calculated using equations (3) to (7).

The average load output P _{Ave in} the first period is obtained by the following equation (9) where n = 1 in the equation (3).

(Equation 9)

Here, the hydraulic output P _Hyd [W] is _expressed by the following equation (10) using the rotational speed N _A [rpm] of the output shaft of the transmission 13 and the torque T _A [N · m] generated by the main pump 14. ).

(Equation 10)
_{P Hyd = 2 × π × T} A × N A / 60
Rotational speed N _A is grasped from the angular velocity of the output shaft measured by the angular velocity detector 130. The torque T _A [N · m] includes the rotational speed N _A , the secondary hydraulic pressure P _A [Pa] detected by the pressure sensor 29, and the oil flow rate Q _A [m ³ / [Min] is calculated by the following equation (11).

(Equation 11)
T _A = P _A × Q _A / (2 × π × N _A )
The electrical output P _Elc [W] is _expressed by the following equation (12) using the current value I _A [A] detected by the ammeter 132 and the voltage value V _A [V] detected by the voltmeter 111. Calculated.

(Equation 12)
P _Elc = I _A × V _A
The required charge / discharge output P _Bat in the second period is obtained by the following equation (13) from the equations (5) and (6).

(Equation 13)
P _Bat = (SOC _Ref −SOC _T2 ) × E _BatFull / T _cyc
By adding the values obtained by Expression (9) and Expression (13), the engine required output P _EngReq in the second period is obtained. It should be noted that various quantities necessary for calculating the engine required output P _EngReq , for example, T _cyc , SOC _Ref , and E _BatFull are stored in the internal memory 30 _{</ b> B} of the control device 30.

Next, on the equal horsepower line with the calculated engine demand output P _EngReq in the second period as the engine output, the engine speed that achieves fuel consumption equal to or lower than that when the engine speed is y [rpm], preferably the lowest The engine speed x that achieves fuel efficiency is selected and determined.

The internal memory 30B stores, for example, the number of revolutions of the engine 11 that achieves the lowest fuel consumption for each range of the engine required output P _EngReq value. The control device 30 refers to the stored content and determines a target value for the engine 11 rotation speed in the second period.

  When the target value of the engine speed 11 is determined, the control device 30 changes the command value for instructing the engine speed and transmits it to the engine 11. The engine 11 is driven at the determined constant rotational speed during the second period in accordance with a command transmitted from the control device 30.

When changing the rotation speed of the engine 11, it is performed gently. FIG. 4 shows the change time of the engine rotational speed as a T _H. It is desirable that the engine speed change rate (xy) / _TH is, for example, such that the operator does not feel uncomfortable.

In addition, when changing the rotation speed of the engine 11, the discharge amount of the main pump 14 is also changed. Thus, by determining the rotation speed of the engine 11 in the second period based on the load output in the first period and the SOC at the end of the first period, for example, the first period and the second period as shown in FIG. when the load output waveform equal to the charging rate _{SOC T3} at time _{T 3} is equal to the target value _{SOC Ref} charging rate.

Engine 11 rotational speed target value of the third period is determined load output of the second period, and the SOC of the power storage circuit 120 (capacitor 19) at the end time T ₃ of the second period based. FIG. 4 shows a case where the target value of the engine 11 rotation speed in the third period is determined to be a value x equal to the engine 11 rotation speed in the second period. In such a case, there is no need to change the command value for commanding the engine speed.

However the time T ₃ after the change work forms and the like, the load output pattern in the first period and the second period becomes different patterns, the average load output P _Ave of the third period, the first, the second period It is bigger than that. As a result, the measured _SOC Mes _{(SOC T4)} at time _{T 4,} a smaller value than the target value _{SOC Ref} charging rate. Therefore, based on the measured values in the third period, the values obtained in the same manner as in Expression (9) and Expression (13) are added, for example, larger than the engine required output E ₂ in the second and third periods. obtaining a requested engine output _{E 1} in 4 periods. Requested engine output E ₁ of the fourth period is output along the equal horsepower line δ1 6. Here, in FIG. 6, when the engine speed of N _AfterBest is maintained and it is made to correspond to the engine output δ1, it will exceed T _Max , but even if it does not exceed T _Max , the fuel consumption will be remarkably deteriorated. End up. Obtains a requested engine output E ₁ in this order time T _4, the control device 30 alters the most fuel efficiency rpm on equal horsepower line δ1 the speed of the engine 11 (z). Thus, fuel efficiency can be improved by changing the engine output according to the average load in the previous period. Further, since the engine speed is changed to the speed with the best fuel efficiency in accordance with the change in the engine required output, the fuel efficiency of the engine can be further improved.

The average load in the fourth period is as long as the same as the third time period, the charging rate _{SOC T5} at time _{T 5} coincides with the target value _{SOC Ref} charging rate.

  According to the control method for the hybrid work machine according to the embodiment, the engine can be operated efficiently. Further, the engine can be driven with low fuel consumption.

  FIG. 7 is a functional block diagram of the CPU 30 </ b> A included in the control device 30. With reference to this figure, the control method of the hybrid type working machine by a modification is demonstrated.

  The CPU 30A includes an output condition calculation unit and a power distribution unit. The output condition calculation unit calculates the output conditions of the engine 11 and the battery (capacitor 19).

  As described so far, the average load output of the previous period is calculated from the hydraulic load request output and the electrical load request output, and this and the storage circuit 120 (capacitor 19) derived from the battery (capacitor 19) voltage. An engine request output is calculated based on the SOC. Then, a target value of the engine speed is calculated based on the engine required output.

For example, when the target value of the engine 11 rotation speed in the second period is determined to be x and the engine 11 is operated at the rotation speed x, the engine rotation speed x is input to the block 30A-1. Block 30A-1 is, for instance as illustrated, the upper limit of the proper engine output determined by the engine speed, and with reference to the map or conversion table showing the lower limit, the engine in rpm x output upper limit value P _H, and determining the engine output lower limit value P _L. The map or the conversion table is stored in the internal memory 30B of the control device 30.

  The SOC of the power storage circuit 120 (capacitor 19) derived from the battery voltage is input to the other block 30A-2 of the output condition calculation unit, and the battery current output upper limit value, the battery current output lower limit value, and the battery output target value Is determined.

The engine output upper limit value P _H , the engine output lower limit value P _L , the battery current output upper limit value, the battery current output lower limit value, and the battery output target value determined in the blocks 30A-1 and 30A-2 of the output condition calculation unit are: Input to the power distribution unit.

The power distribution unit determines a hydraulic load output, an electric load output, and an assist motor output command based on the input values, the hydraulic load request output, and the electric load request output. The control device 30 controls the hydraulic pressure supplied to the hydraulic load based on the hydraulic load output, controls the power supplied to the electric load based on the electrical load output, and assist motor (motor generator based on the assist motor output command) The assist amount of the engine 11 and the power generation amount by the assist motor according to 12) are controlled. According to the control by the control device 30, in the second period in which the engine 11 speed is a x, the output P _Eng of the engine 11, the engine output a lower limit value P _L or more, are the scope of the following engine output upper limit value P _H .

In the control method according to the modification, for example, in the second period, when the engine 11 is driven at a rotational speed x, the output P _Eng time constant time satisfying the engine output upper limit value P _H of the engine 11, for example 5 When the minute is exceeded, the second period is terminated at that time, and the third period (for example, the initial setting period) is continued by a method similar to the method (control method according to the embodiment) described with reference to FIGS. The number of revolutions of the engine 11 in the length T _cyc ) is determined. Such control can further improve the working efficiency.

For example, the control unit 30, in the second period, measures the time which the output _{P Eng} of the engine 11 is an engine output upper limit value _{P H.} Then, the measured value is compared with a predetermined value, for example, 5 minutes. When the measured value exceeds 5 minutes, the second period is ended and the engine 11 rotational speed in the third period is determined.

  As mentioned above, although this invention was demonstrated along the Example and the modification, this invention is not restrict | limited to these.

  For example, in the embodiment, the end time of the n-th period and the start time of the (n + 1) -th period coincide with each other.

  In the embodiment, the target value of the rotational speed of the engine 11 in the (n + 1) period is determined based on the calculated value in the output (power) dimension based on the average value of the load output in the n period. However, for example, based on the energy supplied to the entire load in the nth period, the target value of the rotational speed of the engine 11 in the (n + 1) period may be determined based on the calculated value in the energy dimension.

Further, in the modified example, the output P _Eng of the engine 11 has determined a new engine 11 rotational speed when the time becomes the engine output upper limit value P _H exceeds the predetermined time, the output P _Eng of the engine 11 is an engine when the time becomes the output lower limit value P _L has exceeded the predetermined time, it is also possible to newly determine engine 11 speed.

For example, the control unit 30, in the second period, measures the time that the output _{P Eng} of the engine 11 is an engine output lower limit value _{P L.} Then, the measured value is compared with a predetermined value, for example, 6 minutes. When the measured value exceeds 6 minutes, the second period is ended and the engine 11 rotational speed in the third period is determined.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

  It can be used for hybrid work machines in general.

1 Lower traveling body (base)
1A, 1B Hydraulic motor 2 Turning mechanism 3 Upper turning body 4 Boom 5 Arm 6 Bucket 7 Boom cylinder 8 Arm cylinder 9 Bucket cylinder 10 Cabin 11 Engine 12 Motor generator 13 Transmission 14 Main pump 15 Pilot pump 16 High pressure hydraulic line 17 Control Valve 18 Inverter 19 Capacitor 20 Inverter 21 Turning motor 22 Resolver 23 Mechanical brake 24 Transmission 25 Pilot line 26 Operating device 27, 28 Hydraulic line 29 Pressure sensor 30 Control device 35 Display device 100 Converter (capacitor charge / discharge circuit)
101 Reactor 102A Boost IGBT
102B IGBT for step-down
102a, 102b Diodes 103A, 103B Power connection terminals 104A, 104B Output terminal 105 Smoothing capacitor 106 Voltmeter 107 Ammeter 110 DC bus line 111 Voltmeter 120 Power storage circuit 130 Angular velocity detector 131 Flow meter 132 Ammeter

Claims (13)

An engine that generates power,
A motor that is connected to the engine and performs an electric operation, and a motor generator that functions as a generator that performs a power generation operation, so that the power generated by the engine can be transmitted;
When the motor generator functions as a motor, power is supplied to the motor generator, and when the motor generator functions as a generator, a capacitor is supplied with power from the motor generator;
A hydraulic load driven by at least the power generated by the engine; and
An electric load driven by being supplied with power from at least the capacitor;
A control device for controlling the rotational speed of the engine,
The controller controls the engine speed in a second period following the first period based on a temporal change or energy of power supplied to the hydraulic load and the electric load in the first period. A hybrid work machine that determines the target value of the machine and controls the rotational speed so that the determined target value is obtained.   The control device derives an average target output of the engine in the second period, and determines the engine speed based on the speed at which the fuel consumption is lowest when the engine is driven at the average target output. The hybrid work machine according to claim 1, wherein a target value is determined. The control device determines a target value of the engine speed in the second period based on a time average value of power supplied to the hydraulic load and the electric load in the first period. The hybrid work machine according to claim 1 or 2.   The control device measures a time during which the output of the engine is an upper limit value in the first period, compares the measurement result with the first value, and the measurement result exceeds the first value. Or, in the first period, when the output of the engine becomes a lower limit value is measured, the measurement result is compared with the second value, and when the measurement result exceeds the second value, The hybrid work machine according to claim 1, wherein the first period is ended.   5. The control device according to claim 1, wherein the control device determines a target value of the engine speed in the second period according to a charging rate of the capacitor at the end of the first period. The hybrid type work machine according to the item. An engine that generates power, an electric motor that is connected to the engine and that performs an electric operation so that the power generated by the engine can be transmitted, and a motor generator that functions as a generator that performs an electric power generation operation; and When the motor generator functions as a motor, power is supplied to the motor generator. When the motor generator functions as a generator, the capacitor is supplied with power from the motor generator, and is generated at least in the engine. A control method of a hybrid work machine having a hydraulic load driven by being supplied with power and an electric load driven by being supplied with power from at least the capacitor,
(A) grasping time change or energy of power supplied to the hydraulic load and the electric load in the first period;
(B) determining a target value of the engine speed in the second period following the first period based on the time change or energy of the power grasped in the step (a);
And (c) controlling the engine speed so that the engine speed in the second period becomes the target value determined in the step (b). Method. The step (b)
(B1) deriving an average target output of the engine in the second period based on the time change or energy of the power grasped in the step (a);
The hybrid type work according to claim 6, further comprising: (b2) determining a target value of the engine speed based on the engine speed at which the fuel consumption is lowest when the engine is driven at the average target output. How to control the machine. In the step (b), based on a time average value of power supplied to the hydraulic load and the electric load in the first period, a target value of the engine speed in the second period is determined. The method for controlling a hybrid work machine according to claim 6 or 7, wherein the method is determined. The step (a)
(A1) measuring a time during which the output of the engine is an upper limit value in the first period;
(A2) comparing the time measured in the step (a1) with a first value and terminating the first period when the measured time exceeds the first value. The method for controlling a hybrid work machine according to any one of claims 6 to 8. The step (a)
(A3) measuring a time during which the output of the engine becomes a lower limit value in the first period;
(A4) comparing the time measured in the step (a3) with a second value and ending the first period when the measured time exceeds the second value. The control method of the hybrid type work machine of any one of Claims 6-9.   The said process (b) WHEREIN: The target value of the rotation speed of the said engine of the said 2nd period is determined according to the charging rate of the said capacitor in the end time of the said 1st period. A control method for a hybrid type work machine according to claim 1. 6. The hybrid work machine according to claim 1, wherein the control device drives the engine at a constant rotational speed of a determined target value during the second period. The method for controlling a hybrid type work machine according to any one of claims 6 to 11, wherein in the step (c), the engine is driven at a constant rotation speed during the second period.