JP5278517B2 - Hydraulic unit - Google Patents

Abstract

A surplus flow control unit (50) controls an inverter (6): in a manner such that when the flow discharged from a pump (1) is a high flow, the surplus flow from a relief valve (3) is a low surplus flow; and in a manner such that when the flow discharged from the pump (1) is a low flow that is lower than the high flow, the surplus flow from the relief valve (3) is a high surplus flow that is higher than the low surplus flow.

Description

  The present invention relates to a hydraulic unit such as a hydraulic unit or a hydraulic unit used in various industrial machines such as construction machines, agricultural machines, machine tools, and injection molding machines.

  Conventionally, as a hydraulic unit, as shown in FIG. 8, a fixed displacement pump 101, a motor 102 for driving the pump 101, a relief valve 103 connected to a discharge line 106 of the pump 101, and the relief A flow rate sensor 104 connected between the valve 103 and the tank 107 for detecting an excessive flow rate from the relief valve 103, and a rotation speed control means 105 for controlling the rotation speed of the motor 102 based on a signal from the flow rate sensor 104. (See JP-A-11-303758: Patent Document 1).

  The rotational speed control means 105 feedback-controls the rotational speed of the motor 102 so that the excess flow detected by the flow sensor 104 becomes a predetermined value.

  However, in the conventional hydraulic unit, the rotation speed control means 105 controls the motor 102 so that the excess flow rate of the flow rate sensor 104 becomes a predetermined value, so that the discharge amount from the pump 101 is small. In order to ensure the stability of the control, it is necessary to ensure a relatively large surplus flow rate, and the predetermined value of the surplus flow rate is large. For this reason, even when there is a large discharge amount from the pump 101 whose control is stable, the motor 102 is controlled so that the surplus flow rate becomes a large predetermined value. There was a loss.

Japanese Patent Laid-Open No. 11-303758

  Accordingly, an object of the present invention is to provide a hydraulic unit capable of ensuring the stability of pressure control and realizing energy saving and prevention of oil heat generation.

In order to solve the above problems, the hydraulic unit of the present invention is:
A fixed displacement pump that supplies liquid to the main engine,
A motor for driving the pump;
An inverter connected to the motor;
A relief valve connected to the discharge line of the pump;
A sensor for detecting an excessive flow rate from the relief valve;
A control unit for controlling the rotational speed of the motor via the inverter based on the surplus flow rate detected by the sensor;
The control unit
When the discharge amount from the pump is a large flow rate, the inverter is controlled so that the surplus flow rate from the relief valve becomes a small surplus flow rate based on the surplus flow rate detected by the sensor ,
When the discharge amount from the pump is a small flow rate smaller than the large flow rate, the surplus flow rate from the relief valve becomes a large surplus flow rate larger than the small surplus flow rate based on the surplus flow rate detected by the sensor. Thus, it has the surplus flow control part which controls the above-mentioned inverter.

  According to the hydraulic unit of the present invention, since the control unit includes the surplus flow rate control unit, for example, in a state where the pressure is controlled by flowing the liquid from the relief valve in the pressure-holding state, the discharge from the pump is performed. When the amount is small, the surplus flow rate from the relief valve can be increased to ensure a constant motor rotation speed to eliminate motor control instability and pressure control instability due to the relief valve. That is, in general, the pressure becomes unstable when the flow rate flowing through the relief valve is a small flow rate. For example, if the surplus flow rate is controlled at the minimum flow rate of the relief valve that can stably control the pressure, the control stability And greater energy savings. On the other hand, when the discharge amount from the pump is large, the surplus flow rate can be reduced to suppress energy loss and prevent oil from being heated.

  Therefore, stability of pressure control can be secured, and energy saving and prevention of heat generation of oil can be realized.

Moreover, in the hydraulic unit of one embodiment,
The surplus flow rate control unit
As the liquid supply flow rate to the main machine side increases, the surplus flow rate gradually decreases, while when the liquid supply flow rate to the main machine side exceeds a predetermined value, the surplus flow rate becomes a constant value. ,Control.

  According to the hydraulic unit of this embodiment, the surplus flow rate control unit gradually decreases the surplus flow rate as the supply flow rate to the main unit increases, while the supply flow rate to the main unit reaches a predetermined value. Since the control is performed so that the surplus flow rate becomes a constant value when the flow rate exceeds 1, the surplus flow rate from the relief valve is increased when the supply flow rate to the main engine side is small, and a constant motor rotation speed is ensured. Control stability can be secured. Moreover, when the supply flow rate to the main engine side is large, the surplus flow rate from the relief valve can be reduced to realize energy saving and prevention of oil heat generation.

  Moreover, in the hydraulic unit of one embodiment, the surplus flow rate control unit has a base clipper that limits the rotation speed of the pump.

  According to the hydraulic unit of this embodiment, the surplus flow rate control unit has a base clipper that limits the rotation speed of the pump, and can therefore be controlled to an optimum surplus flow rate. For example, when the minimum number of rotations of the motor and the minimum number of rotations of the pump are set as the base clipper, it is possible to achieve both control stability, pump protection, and a greater energy saving effect.

  Moreover, in the hydraulic unit of one embodiment, the surplus flow rate control unit has a surplus flow rate target value creation unit that changes the target value of the surplus flow rate according to the supply flow rate to the main engine side.

  According to the hydraulic unit of this embodiment, the surplus flow rate control unit has a surplus flow rate target value creation unit that changes the target value of the surplus flow rate according to the supply flow rate to the main engine side. The flow rate can be controlled.

  Further, in the hydraulic unit of one embodiment, the surplus flow rate control unit switches the gain according to the magnitude of the deviation between the target surplus flow rate and the current surplus flow rate, and the dead zone in the zero and near zero areas of the deviation. Is provided.

  According to the hydraulic unit of this embodiment, the surplus flow rate control unit switches the gain according to the magnitude of the deviation between the target surplus flow rate and the current surplus flow rate, and the dead zone in the zero and near zero areas of the deviation. Therefore, while switching from the pressure-holding state to the flow rate control, the responsiveness is increased, and in the pressure-holding state, the gain can be lowered to stabilize the control.

  According to the hydraulic unit of the present invention, the control unit controls the inverter so that when the discharge amount from the pump is a large flow rate, the surplus flow rate from the relief valve becomes a small surplus flow rate, When the discharge amount from the pump is a small flow rate smaller than the large flow rate, the surplus flow control unit that controls the inverter so that the surplus flow rate from the relief valve becomes a large surplus flow rate greater than the small surplus flow rate Therefore, stability of pressure control can be ensured, and energy saving and prevention of oil heat generation can be realized.

It is a circuit diagram of the hydraulic unit of one embodiment of the hydraulic unit of the present invention. It is a graph which shows the relationship between the main machine side supply flow rate, pump discharge amount, and an excessive flow rate. It is a graph which shows the relationship between speed deviation (target surplus flow rate-present surplus flow rate) and pump discharge amount variation. It is a block diagram which shows the control by a base clipper. It is a flowchart which shows the control by a base clipper. It is a block diagram which shows the control by a surplus flow target value preparation part. It is a flowchart which shows the control by a surplus flow target value preparation part. It is a circuit diagram of the conventional hydraulic unit.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 shows a circuit diagram of a hydraulic unit according to an embodiment of the hydraulic unit of the present invention. As shown in FIG. 1, the hydraulic unit includes a fixed displacement pump 1 and a motor 2 that drives the pump 1. The suction side of the pump 1 is connected to a tank 10 in which oil is stored, and a main machine 7 is connected to a discharge line 11 of the pump 1. The main machine 7 has a hydraulic cylinder, a hydraulic motor, a solenoid valve, etc. (not shown). The oil discharged from the pump 1 is returned to the tank 10 via the main machine 7.

  A relief valve 3 is connected to a branch line 12 branched from the discharge line 11 of the pump 1. The relief valve 3 allows the upstream oil to escape downstream when the discharge pressure of the pump 1 upstream of the relief valve 3 becomes larger than the set pressure, and the pressure of the discharge line 11 becomes the set pressure. Control to become. Hereinafter, the flow rate of the oil discharged from the relief valve 3 is referred to as an excess flow rate. Note that the set pressure of the relief valve 3 may be variable.

  The branch line 12 is provided with a throttle 8 on the downstream side of the relief valve 3, and a pressure sensor 4 is provided between the throttle 8 and the relief valve 3. Since the surplus flow rate passing through the throttle 8 is determined by the pressure difference before and after the throttle 8 (difference between the upstream pressure of the throttle 8 and the tank pressure), the pressure sensor 4 eventually detects the surplus flow rate. become. However, instead of the pressure sensor 4, a flow rate sensor may be provided to detect the excess flow rate directly.

  The branch line 12 is provided with a line 13 branched from the upstream side of the throttle 8 to the tank 10, and the load check valve 9 is provided on the line 13. The load check valve 9 opens to protect the circuit when the excess flow rate becomes excessive and the pressure on the upstream side of the throttle 8 becomes larger than the spring force of the load check valve 9. A relief valve or a safety valve may be used instead of the load check valve.

  An inverter 6 is connected to the motor 2, and the inverter 6 is controlled by the control unit 5. The control unit 5 sends a switching signal to the inverter 6 based on the surplus flow detected by the pressure sensor 4, and controls the rotation speed of the motor 2 via the inverter 6.

  The control unit 5 has a surplus flow rate control unit 50. The surplus flow rate control unit 50 controls the inverter 6 so that the surplus flow rate from the relief valve 3 becomes a small surplus flow rate when the discharge rate from the pump 1 is a large flow rate. When the flow rate is smaller than the large flow rate, the inverter 6 is controlled so that the surplus flow rate from the relief valve 3 becomes a large surplus flow rate larger than the small surplus flow rate.

  As shown in FIG. 2, the surplus flow rate control unit 50 gradually decreases the surplus flow rate as the oil supply flow rate to the main machine 7 increases, while the oil supply flow rate to the main machine 7 side has a predetermined value. If it exceeds, control is performed so that the surplus flow rate becomes a constant value.

  That is, the excess flow rate QL indicated by hatching gradually decreases from the second flow rate value Q2 to the first flow rate value Q1 (<Q2) as the main engine side supply flow rate Qp increases from 0 to the predetermined value Qp1. The surplus flow rate QL becomes a constant value of the first flow rate value Q1 when the main engine side supply flow rate Qp exceeds a predetermined value Qp1.

  Further, the pump discharge amount Q becomes a constant value of the second flow rate value Q2 when the main engine side supply flow rate Qp increases from 0 to a predetermined value Qp1, while the pump discharge amount Q is equal to the main engine side supply flow rate Qp. When the value Qp1 is exceeded, it gradually increases from the second flow rate value Q2.

  The main machine side supply flow rate Qp is a value obtained by subtracting the surplus flow rate QL from the pump discharge amount Q, and is equal to the flow rate returned from the main device 7 to the tank 10.

  As shown in FIG. 3, the surplus flow rate control unit 50 switches the gain according to the magnitude of the deviation between the target surplus flow rate and the current surplus flow rate, and provides a dead zone in the region of zero and near zero deviation.

  That is, when the speed deviation dV, which is the deviation between the target surplus flow rate and the current surplus flow rate, increases from 0 to dV1, the pump discharge amount change amount dQ, which is a gain, becomes zero, which is a dead zone. When the speed deviation dV increases from dV1 to dV2, the pump discharge amount change amount dQ gradually increases from 0 to dQ1. When the speed deviation dV increases from dV2 to dV3, the pump discharge amount change dQ gradually increases from dQ1 to dQ2. The rate of change of the pump discharge amount change amount dQ from dQ1 to dQ2 is larger than the rate of change of the pump discharge amount change amount dQ from 0 to dQ1. When the speed deviation dV exceeds dV3, the pump discharge amount change amount dQ becomes a constant value of dQ2.

  Similarly, when the speed deviation dV sequentially changes from 0 to -dV1, -dV1 to -dV2, -dV2 to -dV3, the pump discharge amount change dQ is 0, 0 to -dQ1, -dQ1. -DQ2 in order.

  Therefore, while switching from the pressure holding state to the flow rate control, the response can be improved, and in the pressure holding state, the gain can be lowered to stabilize the control.

  As shown in FIG. 1, the surplus flow rate control unit 50 includes a base clipper 51 that limits the rotational speed of the pump 1. The base clipper 51 limits the lower limit value of the rotation speed of the pump 1 and sets the functional relationship of the discharge amount from the pump 1 to the shape (pump discharge amount Q) shown in the graph of FIG.

  And the command of the discharge amount to the pump 1 by the said surplus flow control part 50 is demonstrated concretely. As shown in the block diagram of FIG. 4, the surplus flow rate control unit 50 includes an addition point 21, a pump discharge amount change amount calculation unit 22, an integration unit 23, and a pump discharge amount command limit 24.

  The addition point 21 obtains a deviation between the current surplus flow rate and the target surplus flow rate. The current surplus flow rate is detected by the pressure sensor 4. The target surplus flow rate is input from the outside, for example.

  The pump discharge amount change amount calculation means 22 calculates the pump discharge amount change amount based on the deviation obtained by the addition point 21 using the functional relationship shown in FIG.

  The integration unit 23 integrates the pump discharge amount change amount calculated by the pump discharge amount change amount calculation unit 22 to obtain the pump discharge amount.

  The pump discharge amount command limit 24 is an example of the base clipper 51, and limits the lower limit value of the pump discharge amount calculated by the integrating means 23 so that the pump discharge amount becomes the pump discharge amount Q shown in FIG. Next, the inverter 6 is commanded.

  The flow of the command for the discharge amount to the pump 1 by the surplus flow control unit 50 will be described. As shown in the flowchart of FIG. 5, when the control of the surplus flow rate control unit 50 is started (step S21), a deviation of the surplus flow rate obtained by subtracting the current surplus flow rate from the target surplus flow rate is calculated (step S22).

  If the excess flow deviation is greater than 0 (step S23), the pump discharge amount is calculated to be incremented (step S24). On the other hand, if the excess flow deviation is 0 or less (step S23), the pump discharge amount. Is calculated to be decremented (step S25). At this time, the pump discharge amount change amount shown in FIG. 3 is used to calculate the pump discharge amount change amount based on the deviation of the surplus flow rate, and then the pump discharge amount change amount is integrated to obtain the pump discharge amount.

  Thereafter, if the pump discharge amount is equal to or less than a predetermined value (step S26), the pump discharge amount is set to a constant value (step S27), the inverter is commanded so that the pump discharges the pump discharge amount, and the control is finished. (Step S28). On the other hand, when the pump discharge amount exceeds a certain value (step S26), the inverter is commanded so that the pump discharges the pump discharge amount as it is, and the control is ended (step S28).

  Therefore, since the surplus flow rate control unit 50 has the pump discharge amount command limit 24 as the base clipper 51, it can be controlled to an optimum surplus flow rate.

  As shown in FIG. 1, the surplus flow rate control unit 50 may include a surplus flow rate target value creation unit 52 instead of the base clipper 51. The surplus flow rate target value creation unit 52 may be provided together with the base clipper 51. In this case, the base clipper 51 and the surplus flow rate target value creation unit 52 can be switched.

  The surplus flow rate target value creation unit 52 changes the surplus flow rate target value in accordance with the supply flow rate to the main machine 7 side. That is, the functional relationship of the target value of the surplus flow is assumed to be the shape (surplus flow QL) shown in the graph of FIG.

  A command for the discharge amount to the pump 1 by the surplus flow target value creation unit 52 of the surplus flow control unit 50 will be specifically described. As shown in the block diagram of FIG. 6, the surplus flow rate control unit 50 includes an addition point 31, a pump discharge amount change amount calculation unit 32, an integration unit 33, and a target surplus flow rate calculation unit 34.

  The target surplus flow rate calculating means 34 is an example of the surplus flow rate target value creating unit 52, and using the functional relationship of the surplus flow rate QL shown in FIG. 2, the target surplus flow rate is calculated from the oil supply flow rate to the main engine 7 side. calculate.

  The addition point 31 obtains a deviation between the target surplus flow calculated by the target surplus flow calculating means 34 and the current surplus flow detected by the pressure sensor 4.

  The pump discharge amount change amount calculation means 32 calculates the pump discharge amount change amount based on the deviation obtained by the addition point 31 using the functional relationship shown in FIG.

  The integration means 33 integrates the pump discharge amount change amount calculated by the pump discharge amount change amount calculation means 32 to obtain the pump discharge amount. The pump discharge amount calculated by the integrating means 33 becomes the pump discharge amount Q shown in FIG. 2, and commands the inverter 6 to discharge the pump discharge amount.

  The flow of the discharge amount command to the pump 1 by the surplus flow target value creation unit 52 of the surplus flow control unit 50 will be described. As shown in the flowchart of FIG. 7, when the control of the surplus flow rate control unit 50 is started (step S31), the target surplus flow rate is calculated from the main engine side supply flow rate using the functional relationship of the surplus flow rate QL shown in FIG. Step S32).

  Then, a deviation of the surplus flow rate obtained by subtracting the current surplus flow rate from the target surplus flow rate is calculated (step S33). If the surplus flow deviation is larger than 0 (step S34), the pump discharge amount is calculated to be incremented (step S35). If the surplus flow deviation is 0 or less (step S34), the pump discharge amount is decreased. It calculates so that it may be divided (step S36). At this time, the pump discharge amount change amount shown in FIG. 3 is used to calculate the pump discharge amount change amount based on the deviation of the excess flow rate, and then the pump discharge amount change amount is integrated to obtain the pump discharge amount.

  Thereafter, the inverter is commanded so that the pump discharges the pump, and the control is terminated (step S37).

  Therefore, since the surplus flow rate control unit 50 includes the target surplus flow rate calculation unit 34 as the surplus flow rate target value creation unit 52, it can be controlled to an optimum surplus flow rate.

  According to the hydraulic unit having the above-described configuration, the control unit 5 includes the surplus flow rate control unit 50. For example, in the state where the pressure is controlled by flowing the liquid from the relief valve 3 in the pressure-holding state, When the discharge amount from 1 is small, the surplus flow rate from the relief valve 3 is increased to ensure a constant motor rotation speed to eliminate motor control instability and pressure control instability by the relief valve 3 This can be solved. Further, when the discharge amount from the pump 1 is large, it is possible to reduce the surplus flow rate, suppress energy loss and prevent heat generation of oil.

  Therefore, stability of pressure control can be secured, and energy saving and prevention of heat generation of oil can be realized.

  Further, the surplus flow rate control unit 50 gradually decreases the surplus flow rate as the supply flow rate to the main unit 7 increases, while the surplus flow rate control unit 50 increases the surplus flow rate control unit 50 when the supply flow rate to the main unit 7 side exceeds a predetermined value. Since the control is performed so that the flow rate becomes a constant value, when the supply flow rate to the main engine 7 side is small, the surplus flow rate from the relief valve 3 is increased to ensure a constant motor rotation speed, and the stability of pressure control Can be secured. That is, generally, when the flow rate flowing through the relief valve is a small flow rate, the pressure becomes unstable. However, for example, if the surplus flow rate is controlled with the lowest flow rate of the relief valve 3 that can stably control the pressure, the control becomes stable. Compatibility with greater energy savings. On the other hand, when the supply flow rate to the main engine 7 side is large, the surplus flow rate from the relief valve 3 can be reduced to realize energy saving and prevention of oil heat generation.

  In addition, this invention is not limited to the above-mentioned embodiment. For example, the base clipper and the surplus flow rate target value creation unit may be a software process or a hardware process. In addition, when the minimum rotation speed of the motor, the minimum rotation speed of the pump, or the like is set as the base clipper, it is possible to achieve both stability of control, protection of the pump, and a greater energy saving effect.

  The configuration of the present invention may be applied to a hydraulic unit such as a hydraulic unit in addition to the hydraulic unit. As main machines, there are various industrial machines such as construction machines, agricultural machines, machine tools, and injection molding machines.

DESCRIPTION OF SYMBOLS 1 Fixed capacity type pump 2 Motor 3 Relief valve 4 Pressure sensor 5 Control part 50 Surplus flow control part 51 Base clipper 52 Surplus flow target value preparation part 6 Inverter 7 Main machine 8 Restriction 9 Load check valve 10 Tank 11 Discharge line 12 Branch line

Claims (5)

A fixed displacement pump (1) for supplying liquid to the main machine (7);
A motor (2) for driving the pump (1);
An inverter (6) connected to the motor (2);
A relief valve (3) connected to the discharge line (11) of the pump (1);
A sensor (4) for detecting an excess flow rate from the relief valve (3);
A controller (5) for controlling the rotational speed of the motor (2) via the inverter (6) based on the surplus flow rate detected by the sensor (4);
The control unit (5)
When the discharge amount from the pump (1) is a large flow rate, the surplus flow rate from the relief valve (3) becomes a small surplus flow rate based on the surplus flow rate detected by the sensor (4). While controlling the inverter (6),
When the discharge rate from the pump (1) is a small flow rate smaller than the large flow rate, the surplus flow rate from the relief valve (3) is reduced based on the surplus flow rate detected by the sensor (4). A hydraulic unit comprising a surplus flow rate control unit (50) for controlling the inverter (6) so that a large surplus flow rate is greater than a flow rate. The hydraulic unit according to claim 1,
The surplus flow rate control unit (50)
As the liquid supply flow rate to the main machine (7) increases, the surplus flow rate gradually decreases. On the other hand, when the liquid supply flow rate to the main machine (7) side exceeds a predetermined value, the surplus flow rate is reduced. A hydraulic unit that is controlled so as to have a constant value. The hydraulic unit according to claim 2,
The excess flow controller (50) includes a base clipper (51) that limits the rotational speed of the pump (1). The hydraulic unit according to claim 2,
The surplus flow rate control unit (50) includes a surplus flow rate target value creation unit (52) that changes a target value of the surplus flow rate according to a supply flow rate to the main machine (7) side. unit. In the hydraulic unit according to any one of claims 1 to 4,
The surplus flow rate control unit (50) switches the gain according to the magnitude of deviation between the target surplus flow rate and the current surplus flow rate, and provides a dead zone in the region of zero and near zero deviation. Pressure unit.

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