JP4798149B2 - Hybrid hydraulic system - Google Patents

Description

  The present invention relates to a hybrid hydraulic apparatus used in, for example, a construction machine.

  Conventionally, as a hybrid hydraulic apparatus, there is one described in Japanese Patent Application Laid-Open No. 2007-71197 (Patent Document 1). The hybrid hydraulic apparatus includes an engine, a hydraulic pump driven by the engine, a hydraulic actuator that receives supply of hydraulic oil from the hydraulic pump, a generator driven by the engine, and an electric power generated by the generator. And a motor that is driven by the electricity of the battery.

  The generator is installed between the engine and the hydraulic pump. More specifically, a generator is connected to a rotating shaft that is an output shaft of the engine. The tip of the rotating shaft is connected to one end of a pump shaft for driving the hydraulic pump. The other end of the pump shaft is connected to the drive shaft of the electric motor.

  According to the hybrid hydraulic apparatus having the above-described configuration, when the load of the hydraulic actuator is small, the generator is activated, and the battery is charged with the electric power obtained by the generator. When the load on the hydraulic actuator increases, electric power is supplied from the battery to the electric motor, and the electric motor assists the engine.

  By the way, for example, when a conventional hydraulic device described in Japanese Patent Laid-Open No. 5-187042 (Patent Document 2) is to be modified like the hybrid hydraulic device, an engine and a hydraulic pump driven by the engine A generator must be installed between them.

  However, the conventional hydraulic device has a problem in that there is no space between the engine and the hydraulic pump, so that a generator cannot be installed between them and the hybrid device cannot be modified.

If the above-described conventional hydraulic device is hybridized by modification, a large amount of labor and cost are generated.
JP 2007-71197 A Japanese Patent Laid-Open No. 5-187042

  Accordingly, an object of the present invention is to provide a hybrid hydraulic device that can be hybridized with a conventional hydraulic device as it is or with slight modifications.

In order to solve the above problems, the hybrid hydraulic device of the present invention is
Engine,
A main pump driven by the engine;
A hydraulic motor driven by hydraulic fluid from the main pump;
A control valve provided between the main pump and the hydraulic motor;
A generator driven by the hydraulic motor;
A power storage device for storing electricity generated by the generator;
A sub pump for supplying hydraulic oil to a circuit connecting the main pump and the control valve;
Using electricity generated by the generator or electricity stored in the power storage device, and an electric motor that drives the sub-pump ,
A check valve is installed between the circuit and the sub pump,
An electromagnetic clutch is installed between the generator and the hydraulic motor,
The main pump is a variable displacement pump,
When the discharge pressure of the main pump is equal to or lower than a predetermined pressure, constant flow rate control means for keeping the discharge flow rate of the main pump constant;
When the discharge pressure of the main pump exceeds the predetermined pressure, constant horsepower control means for changing the discharge flow rate of the main pump and keeping the horsepower of the main pump constant;
When the discharge pressure of the main pump is equal to or lower than the predetermined pressure and the flow rate of hydraulic oil flowing through the circuit is equal to or higher than a desired flow rate, power generation is performed by connecting the electromagnetic clutch between the hydraulic motor and the generator. Control means;
Assist control means for driving the sub pump when the discharge pressure of the main pump is less than or equal to the predetermined pressure and the flow rate of hydraulic fluid flowing through the circuit is less than or equal to a desired flow rate;
It is characterized by comprising a.

  According to the hybrid hydraulic apparatus having the above configuration, the engine drives the main pump. Then, the hydraulic oil from the main pump is supplied to the hydraulic motor via the control valve, and the hydraulic motor is driven. Since this hydraulic motor drives the generator, the generator may not be provided between the engine and the main pump. Therefore, the conventional hydraulic device can be hybridized as it is or with slight modifications.

In addition , since the check valve is installed between the circuit and the sub pump, it is possible to prevent the hydraulic oil from flowing from the circuit toward the sub pump and to prevent the hydraulic oil in the circuit from being insufficient.

Moreover , since the electromagnetic clutch is installed between the generator and the hydraulic motor, the electromagnetic clutch can be connected or disconnected at an arbitrary timing. Therefore, the degree of freedom of power generation control of the generator can be increased.

Further , since the main pump is a variable displacement pump, the maximum capacity of the main pump can be reduced to reduce the surplus hydraulic oil during standby. Therefore, the energy saving effect can be increased.

In addition , when the discharge pressure of the main pump is less than a predetermined pressure and the flow rate of hydraulic oil flowing through the circuit is greater than or equal to a desired flow rate, power generation control means for generating power by connecting an electromagnetic clutch between the hydraulic motor and the generator is provided. Therefore, during the control by the constant flow rate control means, it is possible to efficiently generate power from the generator using surplus hydraulic oil.

  In addition, when the discharge pressure of the main pump is not more than a predetermined pressure and the flow rate of the hydraulic oil flowing through the circuit is not more than the desired flow rate, the auxiliary pump is provided with assist control means. It is possible to prevent shortage of hydraulic oil in the circuit.

The hybrid hydraulic device of the present invention is
Engine,
A main pump driven by the engine;
A hydraulic motor driven by hydraulic fluid from the main pump;
A control valve provided between the main pump and the hydraulic motor;
A generator driven by the hydraulic motor;
A power storage device for storing electricity generated by the generator;
A sub pump for supplying hydraulic oil to a circuit connecting the main pump and the control valve;
An electric motor that drives the sub pump using electricity generated by the generator or electricity stored in the power storage device;
With
A check valve is installed between the circuit and the sub pump,
An electromagnetic clutch is installed between the generator and the hydraulic motor,
The main pump is a variable displacement pump,
When the discharge pressure of the main pump is equal to or lower than a predetermined pressure, constant flow rate control means for keeping the discharge flow rate of the main pump constant;
When the discharge pressure of the main pump exceeds the predetermined pressure, constant horsepower control means for changing the discharge flow rate of the main pump and keeping the horsepower of the main pump constant;
When the discharge pressure of the main pump is equal to or lower than the predetermined pressure and the flow rate of hydraulic oil flowing through the circuit is equal to or higher than a desired flow rate, power generation is performed by connecting the electromagnetic clutch between the hydraulic motor and the generator. Control means;
Exceeds the discharge pressure above a predetermined pressure of the main pump, and the flow rate of the hydraulic oil flowing in the circuit is at the desired flow rate or less is characterized in that a assist control means for driving the auxiliary pump.

According to the hybrid hydraulic apparatus having the above configuration, the engine drives the main pump. Then, the hydraulic oil from the main pump is supplied to the hydraulic motor via the control valve, and the hydraulic motor is driven. Since this hydraulic motor drives the generator, the generator may not be provided between the engine and the main pump. Therefore, the conventional hydraulic device can be hybridized as it is or with slight modifications.
In addition , since the check valve is installed between the circuit and the sub pump, it is possible to prevent the hydraulic oil from flowing from the circuit toward the sub pump and to prevent the hydraulic oil in the circuit from being insufficient.
Moreover, since the electromagnetic clutch is installed between the generator and the hydraulic motor, the electromagnetic clutch can be connected or disconnected at an arbitrary timing. Therefore, the degree of freedom of power generation control of the generator can be increased.
Further, since the main pump is a variable displacement pump, the maximum capacity of the main pump can be reduced to reduce the surplus hydraulic oil during standby. Therefore, the energy saving effect can be increased.
In addition, when the discharge pressure of the main pump is less than a predetermined pressure and the flow rate of hydraulic oil flowing through the circuit is greater than or equal to a desired flow rate, power generation control means for generating power by connecting an electromagnetic clutch between the hydraulic motor and the generator is provided. Therefore, during the control by the constant flow rate control means, it is possible to efficiently generate power from the generator using surplus hydraulic oil.

  Further, when the discharge pressure of the main pump exceeds the predetermined pressure and the flow rate of the hydraulic oil flowing through the circuit is equal to or less than the desired flow rate, an assist control unit that drives the sub pump is provided. It is possible to prevent shortage of hydraulic oil in the circuit.

The hybrid hydraulic device of the present invention is
Engine,
A main pump driven by the engine;
A hydraulic motor driven by hydraulic fluid from the main pump;
A control valve provided between the main pump and the hydraulic motor;
A generator driven by the hydraulic motor;
A power storage device for storing electricity generated by the generator;
A sub pump for supplying hydraulic oil to a circuit connecting the main pump and the control valve;
An electric motor that drives the sub pump using electricity generated by the generator or electricity stored in the power storage device;
With
A check valve is installed between the circuit and the sub pump,
An electromagnetic clutch is installed between the generator and the hydraulic motor,
The main pump is a variable displacement pump,
When the discharge pressure of the main pump is equal to or lower than a predetermined pressure, constant flow rate control means for keeping the discharge flow rate of the main pump constant;
When the discharge pressure of the main pump exceeds the predetermined pressure, constant horsepower control means for changing the discharge flow rate of the main pump and keeping the horsepower of the main pump constant;
When the flow rate of hydraulic fluid flowing through the circuit is equal to or higher than a desired flow rate, power generation control means for generating power by connecting the electromagnetic clutch between the hydraulic motor and the generator;
Flow rate of the hydraulic oil flowing in the circuit is at the desired flow rate or less is characterized in that a assist control means for driving the auxiliary pump.

According to the hybrid hydraulic apparatus having the above configuration, the engine drives the main pump. Then, the hydraulic oil from the main pump is supplied to the hydraulic motor via the control valve, and the hydraulic motor is driven. Since this hydraulic motor drives the generator, the generator may not be provided between the engine and the main pump. Therefore, the conventional hydraulic device can be hybridized as it is or with slight modifications.
In addition , since the check valve is installed between the circuit and the sub pump, it is possible to prevent the hydraulic oil from flowing from the circuit toward the sub pump and to prevent the hydraulic oil in the circuit from being insufficient.
Moreover, since the electromagnetic clutch is installed between the generator and the hydraulic motor, the electromagnetic clutch can be connected or disconnected at an arbitrary timing. Therefore, the degree of freedom of power generation control of the generator can be increased.
Further, since the main pump is a variable displacement pump, the maximum capacity of the main pump can be reduced to reduce the surplus hydraulic oil during standby. Therefore, the energy saving effect can be increased.
In addition, when the flow rate of the hydraulic oil flowing through the circuit is equal to or higher than a desired flow rate, power generation control means for connecting the electromagnetic clutch between the hydraulic motor and the generator to generate power is provided. During the control, the generator can generate power efficiently using excess hydraulic oil.

  Further, when the flow rate of the hydraulic oil flowing through the circuit is equal to or less than the desired flow rate, the hydraulic control system includes assist control means for driving the auxiliary pump, so that there is insufficient hydraulic oil in the circuit during control by the constant flow rate control means and the constant horsepower control means. Can be prevented.

  According to the hybrid hydraulic apparatus of the present invention, the generator is driven by a hydraulic motor that uses hydraulic oil from the main pump as power, and therefore it is not necessary to provide it between the engine and the main pump. Therefore, the conventional hydraulic device can be hybridized as it is or with slight modifications.

  Hereinafter, the hybrid type hydraulic apparatus of the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 is a schematic perspective view of a hydraulic excavator equipped with a hybrid hydraulic apparatus according to an embodiment of the present invention. In FIG. 1, the inside of the hydraulic excavator is illustrated so that the inside can be seen for easy understanding.

  The hydraulic excavator includes a lower traveling body 101 with a built-in traveling motor 104, an upper revolving body 102 that is turnably mounted on the lower traveling body 101, and a work arm 103 that is mounted on the upper revolving body 102. ing.

  The work arm 103 includes a boom 105, an arm 106, a bucket 107, a boom cylinder 108, a boom offset cylinder 109, an arm cylinder 110 and a bucket cylinder 111.

  One end of the boom 105 is rotatably connected to the upper swing body 102. Further, one end of an arm 106 is rotatably connected to the other end of the boom 105. A bucket 107 is rotatably connected to the other end of the arm 106. These boom 105, arm 106 and bucket 107 are rotationally driven by a boom cylinder 108, a boom offset cylinder 109, an arm cylinder 110 and a bucket cylinder 111.

  FIG. 2 is a schematic diagram showing the configuration of the hybrid hydraulic apparatus.

  The hybrid hydraulic apparatus includes an engine 1, a dual variable capacity main pump 2 as an example of a main pump, a multi valve 3, a hydraulic motor 4, and a dual fixed capacity sub pump 5 as an example of a sub pump. A generator / motor 6 as an example of a generator and an electric motor, and a power storage device 7 are provided.

  The dual variable capacity main pump 2 includes a constant flow rate control unit 201 that keeps the discharge flow rate of the dual variable capacity main pump 2 constant when the discharge pressure of the dual variable capacity main pump 2 is less than a specified value, When the discharge pressure of the variable capacity main pump 2 exceeds a specified value, a constant horsepower control unit 202 that changes the discharge flow rate of the double variable capacity main pump 2 to keep the horsepower of the double variable capacity main pump 2 constant; Have. The dual variable capacity main pump 2 includes a first main pump part P1 and a second main pump part P2. The dual variable capacity main pump 2 is driven by the engine 1 to suck in the hydraulic oil in the tank 8 and supply it to the multi-valve 3 via the circuit 9. Then, the hydraulic oil branches at the multi-valve 3, a part flows toward the actuator unit 10, and the other part flows toward the hydraulic motor 4. The constant flow control unit 201 is an example of a constant flow control unit, and the constant horsepower control unit 202 is an example of a constant horsepower control unit.

  The actuator unit 10 includes a traveling motor 104, a boom cylinder 108, a boom offset cylinder 109, an arm cylinder 110, a bucket cylinder 111, and the like (see FIG. 1).

  The double fixed capacity sub pump 5 includes a first sub pump part P11 and a second sub pump part P12. The hydraulic oil in the tank 8 is supplied to the circuit 9 by driving the dual fixed capacity sub pump 5. A check valve 11 is provided between the double fixed capacity sub pump 5 and the circuit 9.

  The check valve 11 is opened when hydraulic oil flows from the double fixed capacity sub pump 5 toward the circuit 9, and is closed when hydraulic oil flows from the circuit 9 toward the dual fixed capacity sub pump 5.

  The hydraulic motor 4 is connected to an option port of the multi-valve 3 and always receives hydraulic oil from the multi-valve 3. The drive shaft of the hydraulic motor 4 is rotated only to the right by the control of the multi-valve 3.

  The generator / motor 6 is controlled by the controller 12 to generate power. The electricity generated by the generator / motor 6 is stored in the power storage device 7.

  The controller 12 includes a torque signal indicating the torque of the engine 1, a discharge pressure signal indicating the discharge pressure of the dual variable capacity main pump 2, a rotation speed signal indicating the rotation speed of the hydraulic motor 4, and a storage amount of the power storage device 7. Is received. Then, the controller 12 adjusts the load of the generator / motor 6 based on the discharge pressure signal and the storage amount signal. The controller 12 outputs an electromagnetic clutch ON signal for connecting the electromagnetic clutch 13 (see FIG. 4) to the electromagnetic clutch 13 and outputs an electromagnetic clutch OFF signal for disconnecting the electromagnetic clutch 13 to the electromagnetic clutch 13. .

  FIG. 3 is a circuit diagram of the multi-valve 3.

  The multi-valve 3 includes a travel motor operation valve 301, a boom cylinder operation valve 302, and a hydraulic motor operation valve 303. The hydraulic motor operation valve 303 is an example of a control valve.

  The travel motor operation valve 301 and the boom cylinder operation valve 302 are opened and closed under the control of a control device (not shown). When the travel motor operation valve 301 is opened, the hydraulic oil from the dual variable capacity main pump 2 is supplied to the travel motor 104 and the lower travel body 101 travels. On the other hand, when the boom cylinder operation valve 302 is opened, hydraulic oil from the dual variable capacity main pump 2 is supplied to the boom cylinder 108, and the boom 105 rotates with respect to the upper swing body 102.

  The hydraulic motor operation valve 303 can be controlled to be opened and closed by the control device, but the hydraulic motor operation valve 303 is always opened. That is, the open / close state of the hydraulic motor operation valve 303 is fixed to open. For this reason, since the inside of the hydraulic motor 4 is always in communication with the inside of the circuit 9, if surplus hydraulic fluid is discharged from the dual variable capacity main pump 2, the surplus hydraulic fluid is supplied to the hydraulic motor 4. Is done. At this time, the hydraulic motor 4 rotates at a rotational speed corresponding to the excess amount of hydraulic oil. The rotational speed of the hydraulic motor 4 is proportional to the amount of excess hydraulic oil. On the other hand, if there is no surplus in the hydraulic oil discharged from the dual variable capacity main pump 2, the hydraulic oil is not supplied to the hydraulic motor 4 and the hydraulic motor 4 does not rotate.

  Although not shown, the multi-valve 3 includes a valve for operating the boom offset cylinder 109, the arm cylinder 110, and the bucket cylinder 111.

  FIG. 4 is a schematic diagram showing a connection relationship between the generator / motor 6, the hydraulic motor 4, and the dual fixed capacity sub-pump 5.

  The generator / motor 6 is connected to the hydraulic motor 4 through an electromagnetic clutch 13 and connected to the dual fixed capacity sub pump 5 through a direction that is effective only when the one-way clutch 14 is rotated counterclockwise. Has been. When the electromagnetic clutch 13 is connected and the generator / motor 6 is generating power by receiving the driving force of the hydraulic motor 4, it always rotates right, so the one-way clutch 14 is not connected and the sub pump does not rotate. Yes. Further, when the electromagnetic clutch 13 is disengaged and the generator / motor 6 is driven to rotate counterclockwise, the one-way clutch 14 is activated, and the generator / motor 6 can drive the dual fixed capacity sub-pump 5. It is like that.

  According to the hybrid hydraulic apparatus having the above configuration, the generator / motor 6 is driven by the hydraulic motor 4 connected to the option port of the multi-valve 3. It does not have to be provided.

  Therefore, for example, a conventional hydraulic apparatus as described in JP-A-5-187042 can be hybridized as it is or with slight modifications.

  In addition, since the check valve 11 is installed between the circuit 9 and the dual fixed capacity sub pump 5, the hydraulic oil does not flow from the circuit 9 toward the dual fixed capacity sub pump 5. It is possible to prevent the hydraulic oil in 9 from being insufficient.

  In the hybrid hydraulic apparatus, the electromagnetic clutch 13 is controlled based on the rotational speed of the hydraulic motor 4.

  The control of the electromagnetic clutch 13 will be described in more detail. When the hydraulic motor 4 is rotating, a surplus is generated in the hydraulic oil discharged from the dual variable capacity main pump 2. Therefore, the rotational speed of the hydraulic motor 4 is detected, and when the rotational speed is equal to or higher than a predetermined rotational speed, the controller 12 outputs an electromagnetic clutch ON signal. As a result, the electromagnetic clutch 13 is connected, the driving force of the hydraulic motor 4 is transmitted to the generator / motor 6, and the drive shaft of the generator / motor 6 rotates clockwise. As a result, the generator / motor 6 generates power, and the generated electricity is stored in the power storage device 7. When the drive shaft of the generator / motor 6 is rotating clockwise, the one-way clutch 14 is not connected and the dual fixed capacity sub pump 5 is not driven.

  Thereafter, if the rotation of the hydraulic motor 4 stops, it means that there is no excess hydraulic oil, so the controller 12 outputs an electromagnetic clutch OFF signal. Thereby, the electromagnetic clutch 13 is disconnected, and the power generation of the generator / motor 6 is stopped. Then, the drive shaft of the generator / motor 6 is rotated counterclockwise by the control device. Then, the one-way clutch 14 is connected, the driving force of the generator / motor 6 is transmitted to the double fixed capacity sub pump 5, and the double fixed capacity sub pump 5 is driven. As a result, the dual fixed capacity sub-pump 5 supplies hydraulic fluid to the circuit 9, so that shortage of hydraulic fluid can be prevented from occurring in the circuit 9. Moreover, since the generator / motor 6 uses the electricity of the power storage device 7 to drive the dual fixed capacity sub-pump 5, an energy saving effect can also be obtained.

  Thereafter, even if surplus hydraulic oil is generated in the circuit 9 and the surplus hydraulic oil is supplied to the hydraulic motor 4, the hydraulic clutch 4 is idle because the electromagnetic clutch 13 is disengaged. If the rotational speed of the hydraulic motor 4 exceeds a predetermined rotational speed, the dual fixed capacity sub pump 5 is stopped, the electromagnetic clutch 13 is connected again, the generator / motor 6 generates power, and the power storage device 7 stores power. Do.

  Even when the rotational speed of the hydraulic motor 4 is equal to or higher than a predetermined rotational speed, when the power storage amount of the power storage device 7 is equal to or greater than the specified capacity, the electromagnetic clutch 13 is disconnected and the generator / motor 6 does not generate power. .

  By the way, as a control method of the hybrid hydraulic apparatus, there are a plan A, a plan B and a plan C which will be described later. Outline each plan.

  The plan A is a control method in the case where the conventional hydraulic apparatus has a mechanism for saving energy by resetting the maximum capacity of the dual variable capacity main pump 2 to be low.

  The plan B is a control method in the case where the conventional hydraulic apparatus has a mechanism for saving energy by resetting the constant horsepower control set value of the double variable capacity main pump 2 to be low.

  The plan C is a control method for saving energy by resetting the rated speed of the engine to a low value without the above-described mechanism in the dual variable capacity main pump 2 of the conventional hydraulic device.

  Hereinafter, the control method of the plan A will be described with reference to the graph of FIG. 5 and the flowcharts of FIGS.

  FIG. 5 is a graph showing the relationship between the discharge flow rate of the dual variable capacity main pump 2 and the discharge pressure of the dual variable capacity main pump 2. In FIG. 5, it is assumed that the hybrid hydraulic apparatus is a modification of the conventional hydraulic apparatus, and the change in the discharge flow rate of the main pump of the conventional hydraulic apparatus is indicated by a dotted line.

  In the pressure range corresponding to the straight line portion of the solid line in FIG. 5, the constant flow rate control is performed on the double variable capacity main pump 2. Then, constant horsepower control is performed on the double variable capacity main pump 2 in the pressure range corresponding to the curved line portion. Further, the control of the dual variable capacity main pump 2 and the dual fixed capacity sub pump 5 is determined depending on where in the regions A1 to A3 the flow rate of hydraulic oil (●) required by the actuator unit 10 belongs. .

  More specifically, when the discharge pressure of the dual variable capacity main pump 2 is a low pressure that does not enter constant horsepower control and the drive speed of the actuator unit 10 is low, for example, as shown in (1), the actuator The flow rate of the hydraulic oil required by the unit 10 is the flow rate in the region A1. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is smaller than the discharge flow rate of the dual variable capacity main pump 2, surplus hydraulic fluid is generated. Therefore, the electromagnetic clutch 13 is connected and the generator / motor 6 generates power.

  Further, when the discharge pressure of the dual variable capacity main pump 2 is a low pressure that does not enter constant horsepower control and the driving speed of the actuator unit 10 is high, for example, as shown in (2), the actuator unit 10 The flow rate of the hydraulic oil required by is the flow rate in the region A2. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is larger than the discharge flow rate of the dual variable capacity main pump 2, the hydraulic fluid is insufficient. Therefore, the electromagnetic clutch 13 is disconnected, and the double fixed capacity sub pump 5 is driven by the generator / motor 6, and hydraulic fluid is supplied from the double fixed capacity sub pump 5 to the circuit 9. In this case, excessive hydraulic oil is generated, but the electromagnetic clutch 13 is turned off so that the generator / motor 6 does not generate power to simplify the control.

  Further, when the discharge pressure of the dual variable capacity main pump 2 is a high pressure that enters constant horsepower control and the driving speed of the actuator unit 10 is low, the actuator unit 10 is necessary, for example, as shown in (3). The flow rate of hydraulic oil is the flow rate in the region A3. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is smaller than the discharge flow rate of the dual variable capacity main pump 2, surplus hydraulic fluid is generated, but in order to simplify the control, The clutch 13 is disengaged so that the generator / motor 6 does not generate power. The dual fixed capacity sub pump 5 is also not driven.

  Further, when the discharge pressure of the dual variable capacity main pump 2 is a high pressure that enters constant horsepower control and the driving speed of the actuator unit 10 is high, for example, as shown in (4), the dual variable capacity main pump 2 All the hydraulic oil discharged from the pump 2 is supplied to the actuator unit 10. In this case, the electromagnetic clutch 13 is turned off so that the generator / motor 6 does not generate power, and the dual fixed capacity sub pump 5 is not driven to simplify the control.

  Hereinafter, the control of FIG. 5 will be described with reference to the flowcharts of FIGS. 6 and 7.

  First, as shown in FIG. 6, control is started, and it is determined in step S1 whether the current mode is the power generation mode or the electric mode. That is, the generator / motor 6 determines whether it is driven by the hydraulic motor 4 to generate power, or whether it is driving the dual fixed capacity sub pump 5 without generating power. If it is determined in step S1 that the generator / motor 6 is generating power, the process proceeds to step S2. On the other hand, if it is determined in step S1 that the generator / motor 6 is driving the double fixed capacity sub pump 5 without generating power, the process proceeds to step S6 in FIG.

  When the process proceeds to step S2, as shown in FIG. 6, it is determined whether or not the discharge pressure of the double variable capacity main pump 2 is not more than a specified value. This specified value is the maximum value of the pressure range in which the dual variable capacity main pump 2 performs constant flow control. If it is determined in step S2 that the discharge pressure of the dual variable capacity main pump 2 is not more than the specified value, the process proceeds to the next step S3. On the other hand, if it is determined in step S2 that the discharge pressure of the double variable capacity main pump 2 is not less than the specified value, the process proceeds to step S9, the electromagnetic clutch 13 is disconnected, and the power generation mode is continued.

  Next, in step S3, it is determined whether or not the hydraulic motor 4 is rotating. If it is determined in step S3 that the hydraulic motor 4 is rotating, the process proceeds to the next step S4. On the other hand, if it determines with the hydraulic motor 4 not rotating by said step S3, it will progress to step S10, will cut off the electromagnetic clutch 13, and will transfer to electric mode.

  Next, in step S4, it is determined whether or not the amount of power stored in the power storage device 7 is equal to or greater than a specified capacity. If it is determined in step S4 that the power storage amount of the power storage device 7 is not greater than the specified capacity, the process proceeds to the next step S5. On the other hand, if it determines with the electrical storage amount of the electrical storage apparatus 7 being more than regulation capacity | capacitance by the said step S4, it will progress to step S11, the electromagnetic clutch 13 will be cut | disconnected, and electric power generation mode will be continued.

  Next, in Step S5, the electromagnetic clutch 13 is connected, and power is generated by adjusting the load torque of the generator / motor 6 so that the maximum axial load is obtained under the condition that the engine 1 can maintain the rated torque.

  On the other hand, when it determines with electric mode at the said step S1 and progresses to step S6, as shown in FIG. 7, it is determined whether the discharge pressure of the double variable displacement main pump 2 is below a regulation value. This specified value is the maximum value of the pressure range in which the dual variable capacity main pump 2 performs constant flow control. If it is determined in step S6 that the discharge pressure of the dual variable capacity main pump 2 is not more than the specified value, the process proceeds to the next step S7. On the other hand, if it is determined in step S6 that the discharge pressure of the dual variable capacity main pump 2 is not less than the specified value, the process proceeds to step S12, the dual fixed capacity sub pump 5 is stopped, and the power generation mode is entered.

  Next, in step S7, it is determined whether or not the rotational speed of the hydraulic motor 4 is equal to or higher than a predetermined rotational speed. If the rotation speed of the hydraulic motor 4 is equal to or higher than a predetermined rotation speed, the surplus amount of hydraulic oil is excessive. In other words, if the rotational speed of the hydraulic motor 4 is not equal to or higher than the predetermined rotational speed, the surplus amount of hydraulic oil is not excessive. Therefore, if it is determined in step S7 that the rotational speed of the hydraulic motor 4 is not equal to or higher than the predetermined rotational speed, the process proceeds to step S8 to maintain the current state. That is, the electric mode is continued. On the other hand, if it is determined in step S7 that the rotational speed of the hydraulic motor 4 is equal to or higher than the predetermined rotational speed, the process proceeds to step S12.

  In the control as described above, step S5 is an example of the power generation control unit, and step S8 is an example of the assist control unit.

  By adopting the control method of the A plan, the hybrid hydraulic apparatus has a smaller load fluctuation range of the engine 1 and can perform an efficient operation and improve fuel efficiency.

  Further, since the maximum capacity of the dual variable capacity main pump 2 is lowered, the surplus hydraulic oil during standby is reduced, and the energy saving effect can be enhanced.

  Further, the hybrid hydraulic device can hybridize the conventional hydraulic device at a minimum cost and can pass environmental regulations.

  If only the electric mode is used, a part of the function is limited, but the work can be performed without using the engine.

  The hybrid hydraulic apparatus can have the same operation feeling as that of the conventional hydraulic apparatus, regardless of which of the regions A1 to A3 the discharge flow rate of the dual variable capacity main pump 2 belongs to.

  Further, even if the conventional hydraulic device is modified like the hybrid hydraulic device, since the modification is slight, it is possible to prevent the durability reliability from being lowered.

  If the hybrid hydraulic device is a modified version of the conventional hydraulic device, it can be resold as a second-hand product of the conventional hydraulic device by removing the equipment added for hybridization and returning it to its original state. it can.

  Hereinafter, the control method of the plan B will be described with reference to the graph of FIG. 8 and the flowcharts of FIGS.

  FIG. 8 is a graph showing the relationship between the discharge flow rate of the dual variable capacity main pump 2 and the discharge pressure of the dual variable capacity main pump 2. In FIG. 8, it is assumed that the hybrid hydraulic apparatus is a modification of the conventional hydraulic apparatus, and the change in the discharge flow rate of the main pump of the conventional hydraulic apparatus is indicated by a dotted line.

  In the pressure range corresponding to the straight line portion of the solid line in FIG. 8, constant flow rate control is performed on the double variable capacity main pump 2. Then, constant horsepower control is performed on the double variable capacity main pump 2 in the pressure range corresponding to the curved line portion. Further, the control of the dual variable capacity main pump 2 and the dual fixed capacity sub pump 5 is determined depending on where in the areas A21 to A23 the flow rate of hydraulic oil (●) required by the actuator unit 10 belongs. .

  More specifically, when the discharge pressure of the dual variable capacity main pump 2 is a low pressure that does not enter constant horsepower control, for example, as shown in (21), the flow rate of hydraulic oil required by the actuator unit 10 is in a region. It becomes the flow rate in A21. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is smaller than the discharge flow rate of the dual variable capacity main pump 2, surplus hydraulic fluid is generated. Therefore, the electromagnetic clutch 13 is connected and the generator / motor 6 generates power.

  Further, when the discharge pressure of the dual variable capacity main pump 2 is a high pressure that enters constant horsepower control and the drive speed of the actuator unit 10 is low, the actuator unit 10 is necessary, for example, as shown in (22). The flow rate of the working oil is the flow rate in the region A22. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is smaller than the discharge flow rate of the dual variable capacity main pump 2, surplus hydraulic fluid is generated, but in order to simplify the control, The clutch 13 is disengaged so that the generator / motor 6 does not generate power. The dual fixed capacity sub pump 5 is also not driven.

  Further, when the discharge pressure of the dual variable capacity main pump 2 is a high pressure that enters constant horsepower control and the driving speed of the actuator unit 10 is high, the actuator unit 10 is necessary, for example, as shown in (23). The flow rate of the hydraulic oil is the flow rate in the region A23. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is larger than the discharge flow rate of the dual variable capacity main pump 2, the hydraulic fluid is insufficient. Therefore, the electromagnetic clutch 13 is disconnected, and the double fixed capacity sub pump 5 is driven by the generator / motor 6, and hydraulic fluid is supplied from the double fixed capacity sub pump 5 to the circuit 9. In this case, excessive hydraulic oil is generated, but the electromagnetic clutch 13 is turned off so that the generator / motor 6 does not generate power to simplify the control.

  Hereinafter, the control of FIG. 8 will be described with reference to the flowcharts of FIGS. 9 to 11.

  First, as shown in FIG. 9, control is started, and it is determined in step S11 whether the current mode is the power generation mode or the electric mode. That is, the generator / motor 6 determines whether it is driven by the hydraulic motor 4 to generate power, or whether it is driving the dual fixed capacity sub pump 5 without generating power. If it is determined in step S11 that the generator / motor 6 is generating power, the process proceeds to step S12. On the other hand, if it is determined in step S11 that the generator / motor 6 is driving the double fixed capacity sub pump 5 without generating power, the process proceeds to step S15 in FIG.

  When the process proceeds to step S12, as shown in FIG. 9, it is determined whether or not the discharge pressure of the double variable capacity main pump 2 is not more than a specified value. This specified value is the maximum value of the pressure range in which the dual variable capacity main pump 2 performs constant flow control. If it is determined in step S12 that the discharge pressure of the dual variable capacity main pump 2 is not more than the specified value, the process proceeds to the next step S13. On the other hand, if it is determined in step S12 that the discharge pressure of the dual variable capacity main pump 2 is not less than the specified value, the process proceeds to step S18 in FIG.

  In step S18, it is determined whether or not the hydraulic motor 4 is rotating. If it determines with the hydraulic motor 4 rotating in the step S18, it will progress to step S19, the electromagnetic clutch 13 will be cut | disconnected, and electric power generation mode will be continued. On the other hand, if it determines with the hydraulic motor 4 not rotating by said step S18, it will progress to step S10, the electromagnetic clutch 13 will be cut | disconnected, and it will transfer to electric mode.

  Next, as shown in FIG. 9, in step S <b> 13, it is determined whether or not the amount of power stored in the power storage device 7 is equal to or greater than a specified capacity. If it is determined in step S13 that the power storage amount of the power storage device 7 is not greater than the specified capacity, the process proceeds to the next step S14. On the other hand, if it determines with the electrical storage amount of the electrical storage apparatus 7 being more than regulation capacity | capacitance by the said step S13, it will progress to step S20, the electromagnetic clutch 13 will be cut | disconnected, and electric power generation mode will be continued.

  Next, in step S14, the electromagnetic clutch 13 is connected, and power is generated by adjusting the load torque of the generator / motor 6 so that the maximum axial load is obtained under the condition that the engine 1 can maintain the rated torque.

  On the other hand, when it determines with electric mode at the said step S11 and progresses to step S15, as shown in FIG. 10, it determines whether the discharge pressure of the double variable displacement main pump 2 is below a regulation value. This specified value is the maximum value of the pressure range in which the dual variable capacity main pump 2 performs constant flow control. If it is determined in step S15 that the discharge pressure of the dual variable capacity main pump 2 is not less than the specified value, the process proceeds to the next step S16. On the other hand, if it is determined in step S15 that the discharge pressure of the dual variable capacity main pump 2 is equal to or lower than the specified value, the process proceeds to the next step S21, the dual fixed capacity sub pump 5 is stopped, and the power generation mode is entered. .

  Next, in step S16, it is determined whether or not the rotational speed of the hydraulic motor 4 is equal to or higher than a predetermined rotational speed. If the rotation speed of the hydraulic motor 4 is equal to or higher than a predetermined rotation speed, the surplus amount of hydraulic oil is excessive. In other words, if the rotational speed of the hydraulic motor 4 is not equal to or higher than the predetermined rotational speed, the surplus amount of hydraulic oil is not excessive. Therefore, if it is determined in step S16 that the rotational speed of the hydraulic motor 4 is not equal to or higher than the predetermined rotational speed, the process proceeds to step S17 to maintain the current state. That is, the electric mode is continued. On the other hand, if it is determined in step S16 that the rotational speed of the hydraulic motor 4 is equal to or higher than the predetermined rotational speed, the process proceeds to step S21.

  In the control as described above, step S14 is an example of the power generation control unit, and step S17 is an example of the assist control unit.

  By adopting the B-type control method, the hybrid hydraulic device can reduce the load fluctuation range of the engine 1, perform efficient operation, and improve fuel efficiency.

  In addition, since the minimum value of the pressure range for performing the constant horsepower control is reduced, the engine torque load is reduced and fuel consumption can be reduced.

  Further, the hybrid hydraulic device can hybridize the conventional hydraulic device at a minimum cost and can pass environmental regulations.

  If only the electric mode is used, a part of the function is limited, but the work can be performed without using the engine.

  Further, when the discharge flow rate of the dual variable capacity main pump 2 belongs to the region A21, the same operation feeling as that of the conventional hydraulic device can be obtained.

  Further, even if the conventional hydraulic device is modified like the hybrid hydraulic device, since the modification is slight, it is possible to prevent the durability reliability from being lowered.

  If the hybrid hydraulic device is a modified version of the conventional hydraulic device, it can be resold as a second-hand product of the conventional hydraulic device by removing the equipment added for hybridization and returning it to its original state. it can.

  Further, since the switching between the power generation mode and the electric mode is determined only by the discharge pressure of the double variable capacity main pump 2, the control can be simplified.

  Hereinafter, the control method of the plan C will be described with reference to the graph of FIG. 12 and the flowcharts of FIGS.

  FIG. 12 is a graph showing the relationship between the discharge flow rate of the dual variable capacity main pump 2 and the discharge pressure of the dual variable capacity main pump 2. In FIG. 12, it is assumed that the hybrid hydraulic apparatus is a modification of the conventional hydraulic apparatus, and the change in the discharge flow rate of the main pump of the conventional hydraulic apparatus is indicated by a dotted line.

  In FIG. 12, the solid line shows the change in the discharge flow rate of the dual variable capacity main pump 2. Constant horsepower control is performed on the dual variable capacity main pump 2 in the pressure range corresponding to the curved line portion. Further, the control of the dual variable capacity main pump 2 and the dual fixed capacity sub pump 5 is determined depending on where in the areas A31 and A32 the flow rate (●) of the hydraulic oil required by the actuator unit 10 belongs. .

  More specifically, when the driving speed of the actuator unit 10 is low regardless of the discharge pressure of the dual variable capacity main pump 2, for example, as shown in (31), the hydraulic oil required by the actuator unit 10 The flow rate is the flow rate in the region A31. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is smaller than the discharge flow rate of the dual variable capacity main pump 2, surplus hydraulic fluid is generated. Therefore, the electromagnetic clutch 13 is connected and the generator / motor 6 generates power.

  Further, when the driving speed of the actuator unit 10 is high regardless of the discharge pressure of the dual variable capacity main pump 2, for example, as shown in (32), the flow rate of hydraulic oil required by the actuator unit 10 is The flow rate is within the area A32. In this case, since the flow rate of the hydraulic fluid required by the actuator unit 10 is larger than the discharge flow rate of the dual variable capacity main pump 2, the hydraulic fluid is insufficient. Therefore, the electromagnetic clutch 13 is disconnected, and the double fixed capacity sub pump 5 is driven by the generator / motor 6, and hydraulic fluid is supplied from the double fixed capacity sub pump 5 to the circuit 9. In this case, excessive hydraulic oil is generated, but the electromagnetic clutch 13 is turned off so that the generator / motor 6 does not generate power to simplify the control. In this case, the rotational speed of the dual fixed capacity sub pump 5 is adjusted based on a function defined by the sum of the discharge pressure of the first main pump part P1 and the discharge pressure of the second main pump part P2. Thus, the flow rate of the hydraulic oil flowing from the double fixed capacity sub pump 5 to the circuit 9 is set to a fixed flow rate.

  Hereinafter, the control of FIG. 12 will be described using the flowcharts of FIGS. 13 and 14.

  First, as shown in FIG. 13, the control is started, and it is determined in step S31 whether the current mode is the power generation mode or the electric mode. That is, the generator / motor 6 determines whether it is driven by the hydraulic motor 4 to generate power, or whether it is driving the dual fixed capacity sub pump 5 without generating power. If it is determined in step S31 that the generator / motor 6 is generating power, the process proceeds to step S32. On the other hand, if it is determined in step S31 that the generator / motor 6 is driving the double fixed capacity sub pump 5 without generating power, the process proceeds to step S35 in FIG.

  When the process proceeds to step S32, it is determined whether the hydraulic motor 4 is rotating as shown in FIG. If it is determined in step S32 that the hydraulic motor 4 is rotating, the process proceeds to the next step S33. On the other hand, if it determines with the hydraulic motor 4 not rotating by said step S32, it will progress to step S37, will cut | disconnect the electromagnetic clutch 13, and will transfer to electric mode.

  Next, in step S33, it is determined whether or not the amount of power stored in the power storage device 7 is equal to or greater than a specified capacity. If it is determined in step S33 that the power storage amount of the power storage device 7 is not equal to or greater than the specified capacity, the process proceeds to the next step S5. On the other hand, if it determines with the electrical storage amount of the electrical storage apparatus 7 being more than regulation capacity | capacitance by the said step S33, it will progress to step S38, will cut off the electromagnetic clutch 13, and will continue electric power generation mode.

  Next, in Step S34, the electromagnetic clutch 13 is connected, and power is generated by adjusting the load torque of the generator / motor 6 so that the maximum axial load is obtained under the condition that the engine 1 can maintain the rated torque.

  On the other hand, when it determines with electric mode at the said step S31 and progresses to step S35, as shown in FIG. 14, it is determined whether the rotation speed of the hydraulic motor 4 is more than predetermined rotation speed. If the rotation speed of the hydraulic motor 4 is equal to or higher than a predetermined rotation speed, the surplus amount of hydraulic oil is excessive. In other words, if the rotational speed of the hydraulic motor 4 is not equal to or higher than the predetermined rotational speed, the surplus amount of hydraulic oil is not excessive. Therefore, if it is determined in step S35 that the rotational speed of the hydraulic motor 4 is not equal to or higher than the predetermined rotational speed, the process proceeds to step S36 to maintain the current state. That is, the electric mode is continued. On the other hand, if it is determined in step S35 that the rotational speed of the hydraulic motor 4 is equal to or higher than the predetermined rotational speed, the process proceeds to step S39, where the dual fixed capacity sub pump 5 is stopped and the mode is changed to the power generation mode.

  In the control as described above, step S34 is an example of the power generation control unit, and step S36 is an example of the assist control unit.

  By adopting the control method of the C plan, the hybrid hydraulic apparatus has a small fluctuation range of the engine 1 and can perform an efficient operation and improve fuel efficiency.

  Further, since the rated rotational speed of the dual variable capacity main pump 2 is lowered, the surplus hydraulic oil during standby is further reduced, and the energy saving effect can be further enhanced.

  Further, the hybrid hydraulic device can hybridize the conventional hydraulic device at a minimum cost and can pass environmental regulations.

  If only the electric mode is used, a part of the function is limited, but the work can be performed without using the engine.

  If the hybrid hydraulic device is a modified version of the conventional hydraulic device, it can be resold as a second-hand product of the conventional hydraulic device by removing the equipment added for hybridization and returning it to its original state. it can.

  Moreover, since the area A31 is widened, opportunities for power generation are increased, and power can be generated efficiently.

  In the above embodiment, the hydraulic motor 4, the generator / motor 6, the electromagnetic clutch 13 and the one-way clutch 14 are used. However, the hydraulic motor 104, the generator / motor 106, the electromagnetic clutch 113 and the one-way clutch 114 shown in FIG. It may be used.

  The hybrid hydraulic apparatus includes a generator / motor 6 that serves as both a generator and an electric motor. Instead of the generator / motor 6, a generator and a motor separate from the generator are provided. You may prepare. In this case, the electric motor may drive the double fixed capacity sub-pump 5 using electricity generated by the generator.

FIG. 1 is a schematic perspective view of a hydraulic excavator. FIG. 2 is a schematic diagram of a hybrid hydraulic apparatus according to an embodiment of the present invention. FIG. 3 is a circuit diagram of a multi-valve of the hybrid hydraulic apparatus. FIG. 4 is a schematic diagram of a generator / motor, a hydraulic motor, and a dual fixed capacity sub pump of the hybrid hydraulic apparatus. FIG. 5 is a graph for explaining the control method of the plan A of the hybrid hydraulic apparatus. FIG. 6 is a flowchart of the control method of the plan A. FIG. 7 is a flowchart of the control method of the plan A. FIG. 8 is a graph for explaining the control method of the plan B of the hybrid hydraulic apparatus. FIG. 9 is a flowchart of the above-mentioned B plan control method. FIG. 10 is a flowchart of the control method of the above B plan. FIG. 11 is a flowchart of the above-mentioned B plan control method. FIG. 12 is a graph for explaining a control method of the C plan of the hybrid hydraulic apparatus. FIG. 13 is a flowchart of the control method of the above C plan. FIG. 14 is a flowchart of the control method of the above C plan. FIG. 15 is a schematic diagram of another generator / motor, hydraulic motor, electromagnetic clutch, and one-way clutch.

1 Engine 2 Dual variable capacity main pump 4, 104 Hydraulic motor 5 Dual fixed capacity sub pump 6, 106 Generator / motor 11 Check valve 13, 113 Electromagnetic clutch 201 Constant flow rate control unit 202 Constant horsepower control unit 303 Hydraulic motor operation Valve

Claims (3)

Engine (1),
A main pump (2) driven by the engine (1);
A hydraulic motor (4) driven by hydraulic oil from the main pump (2);
A control valve (303) provided between the main pump (2) and the hydraulic motor (4);
A generator (6) driven by the hydraulic motor (4);
A power storage device (7) for storing electricity generated by the generator (6);
A sub pump (5) for supplying hydraulic oil to a circuit (9) connecting the main pump (2) and the control valve (303);
An electric motor (6) for driving the auxiliary pump (5) using electricity generated by the generator (6) or electricity stored in the power storage device (7);
With
A check valve (11) is installed between the circuit (9) and the sub pump (5),
An electromagnetic clutch (13, 113) is installed between the generator (6) and the hydraulic motor (4),
The main pump (2) is a variable displacement pump (2),
When the discharge pressure of the main pump (2) is below a predetermined pressure, constant flow rate control means (201) for keeping the discharge flow rate of the main pump (2) constant;
When the discharge pressure of the main pump (2) exceeds the predetermined pressure, constant horsepower control means (202) for changing the discharge flow rate of the main pump (2) to keep the horsepower of the main pump (2) constant. )When,
When the discharge pressure of the main pump (2) is equal to or lower than the predetermined pressure and the flow rate of hydraulic fluid flowing through the circuit (9) is equal to or higher than a desired flow rate, the hydraulic motor (4) and the generator (6) Power generation control means (S5) for generating power by connecting the electromagnetic clutches (13, 113) in between,
Assist control means for driving the sub pump (5) when the discharge pressure of the main pump (2) is less than or equal to the predetermined pressure and the flow rate of hydraulic fluid flowing through the circuit (9) is less than or equal to a desired flow rate. And a hybrid hydraulic apparatus comprising: S8). Engine (1),
A main pump (2) driven by the engine (1);
A hydraulic motor (4) driven by hydraulic oil from the main pump (2);
A control valve (303) provided between the main pump (2) and the hydraulic motor (4);
A generator (6) driven by the hydraulic motor (4);
A power storage device (7) for storing electricity generated by the generator (6);
A sub pump (5) for supplying hydraulic oil to a circuit (9) connecting the main pump (2) and the control valve (303);
An electric motor (6) for driving the auxiliary pump (5) using electricity generated by the generator (6) or electricity stored in the power storage device (7);
With
A check valve (11) is installed between the circuit (9) and the sub pump (5),
An electromagnetic clutch (13, 113) is installed between the generator (6) and the hydraulic motor (4),
The main pump (2) is a variable displacement pump (2),
When the discharge pressure of the main pump (2) is below a predetermined pressure, constant flow rate control means (201) for keeping the discharge flow rate of the main pump (2) constant;
When the discharge pressure of the main pump (2) exceeds the predetermined pressure, constant horsepower control means (202) for changing the discharge flow rate of the main pump (2) to keep the horsepower of the main pump (2) constant. )When,
When the discharge pressure of the main pump (2) is equal to or lower than the predetermined pressure and the flow rate of hydraulic fluid flowing through the circuit (9) is equal to or higher than a desired flow rate, the hydraulic motor (4) and the generator (6) Power generation control means (S14) for generating power by connecting the electromagnetic clutches (13, 113) in between,
Assist control means (S17) for driving the sub pump (5) when the discharge pressure of the main pump (2) exceeds the predetermined pressure and the flow rate of hydraulic fluid flowing through the circuit (9) is less than or equal to a desired flow rate. And a hybrid hydraulic device. Engine (1),
A main pump (2) driven by the engine (1);
A hydraulic motor (4) driven by hydraulic oil from the main pump (2);
A control valve (303) provided between the main pump (2) and the hydraulic motor (4);
A generator (6) driven by the hydraulic motor (4);
A power storage device (7) for storing electricity generated by the generator (6);
A sub pump (5) for supplying hydraulic oil to a circuit (9) connecting the main pump (2) and the control valve (303);
An electric motor (6) for driving the auxiliary pump (5) using electricity generated by the generator (6) or electricity stored in the power storage device (7);
With
A check valve (11) is installed between the circuit (9) and the sub pump (5),
An electromagnetic clutch (13, 113) is installed between the generator (6) and the hydraulic motor (4),
The main pump (2) is a variable displacement pump (2),
When the discharge pressure of the main pump (2) is below a predetermined pressure, constant flow rate control means (201) for keeping the discharge flow rate of the main pump (2) constant;
When the discharge pressure of the main pump (2) exceeds the predetermined pressure, constant horsepower control means (202) for changing the discharge flow rate of the main pump (2) to keep the horsepower of the main pump (2) constant. )When,
When the flow rate of the hydraulic oil flowing through the circuit (9) is equal to or higher than a desired flow rate, power generation control means for generating power by connecting the electromagnetic clutches (13, 113) between the hydraulic motor (4) and the generator (6). (S34)
A hybrid hydraulic apparatus comprising: assist control means (S36) for driving the auxiliary pump (5) when the flow rate of the hydraulic oil flowing through the circuit (9) is less than or equal to a desired flow rate.