JP4702379B2 - Control device for variable displacement hydraulic motor - Google Patents

Description

  The present invention relates to a control device for a variable displacement hydraulic motor that is used for a hoisting winch or the like of a construction machine such as a crane and changes a rotational speed together with a displacement, and more specifically, prevents a stall of the variable displacement hydraulic motor. The present invention relates to a control device for a variable displacement hydraulic motor that makes it possible.

As a control device for a variable displacement hydraulic motor that is used for hoisting winches of construction machines such as cranes and is capable of changing the rotational speed as well as the capacity of the motor, for example, the configuration described later is used. Is known. In the control apparatus for a variable displacement hydraulic motor according to this conventional example, the capacity (rotational speed) of the variable displacement hydraulic motor is uniquely determined by the pilot pressure supplied from the outside, and appropriate overload prevention is performed. It is configured as follows.
A variable displacement hydraulic motor control apparatus according to this conventional example will be described below with reference to FIG. 4 of its circuit diagram.

  In a swash plate type axial piston motor that changes the tilt angle of the swash plate, that is, the variable displacement hydraulic motor 1, the tilt angle of the swash plate is pushed by the pistons 2 a and 2 b disposed opposite to the hydraulic piston 2. Is changed, the piston stroke of the piston motor is changed, and the capacity of the motor 1 (required oil amount per one rotation) is changed. A control device for controlling the capacity of the motor 1 is combined with the motor 1 and includes a hydraulic piston 2 for driving a swash plate, a spool valve 3, a connecting means 4, a pressure compensation valve 5, and the like.

  The motor 1 communicates with flow paths 6 and 7 (motor drive circuit) through which hydraulic oil of motor supply pressure Pa or Pb (hereinafter referred to as motor drive pressure) is switched and supplied from a hydraulic oil supply source (not shown). . The spool valve 3 communicates with a flow path 14 on which a pilot pressure Pi arbitrarily set by an operator's operation from a pressure generating source acts. The control device, the flow path 6 and the flow path 7 are connected by a flow path 8 in which a shuttle valve 8a is interposed, and the motor driving pressure Pa or Pb is supplied through the flow path 8. The pilot pressure Pi acts from the flow path 14.

  The flow path 8 communicates with the pressure receiving portion of the first piston 2 a through the flow path 9 to increase the capacity of the motor 1 by increasing the angle of the swash plate. Further, the other flow path 10 branched from the flow path 8 reduces the tilt angle of the swash plate via a pressure compensation valve 5 and a spool valve 3 (and flow paths 11 and 12), which will be described later. It communicates with the pressure receiving portion of the second piston 2b that reduces the capacity. The pressure receiving portion of the second piston 2b is set to have a larger pressure receiving area than the pressure receiving portion of the first piston 2a, and when the motor driving pressure Pa or Pb of the same pressure acts on both, the second piston 2b When pressed, the angle of the swash plate is reduced.

  The pressure compensation valve 5 is provided between the flow path 10 and the flow path 11 reaching the pressure receiving portion of the second piston 2b. The pressure compensation valve 5 communicates the flow path 10 and the flow path 11 by the spring force of the spring 5b, but flows in through the shuttle valve 8a and is transmitted from the flow path 13 branched from the flow path 8 or the motor driving pressure Pa or When Pb exceeds the rated value, the flow path 10 and the flow path 11 are blocked against the spring force of the spring 5b, or the flow path 11 is communicated with the return side to the tank. In addition, the said rated value is comprised so that it may be set by adjustment of the screwing amount of the adjustment screw which adjusts the setting dimension of the spring 5b.

  The spool valve 3 is connected in series with the pressure compensation valve 5 between the flow passages 11 and 12 before the second piston 2b, and the spool 3a moves according to the pilot pressure Pi. A flow path 14 is connected to a pilot pressure introducing portion at one end of the spool 3a, and a spring 3b is provided at the other end. The sleeve 3c of the spool valve 3 is connected to the swash plate by a feedback lever 4a swingably attached by a pin 4b of the connecting means 4. Therefore, when the pilot pressure Pi applied to the spool valve 3 is increased, the spool 3a moves to the position shown in the figure, and hydraulic oil is supplied to the second piston 2b, so that the tilt angle of the swash plate is reduced. When the sleeve 3c moves through the feedback lever 4a in accordance with the displacement of the plate and moves to a position where the control deviation becomes zero, the flow path is blocked and the displacement of the swash plate is stopped.

  According to the control device for the motor 1 according to this conventional example, the capacity of the motor 1 is uniquely controlled by the pilot pressure Pi, and the rotational speed is controlled under the condition that the amount of hydraulic oil supplied is constant (rotational speed control). At the same time, overload prevention control is performed by the pressure compensation valve 5. The rotational speed control is illustrated as shown in FIG. 5 of an explanatory diagram of the relationship between the pilot pressure and the motor capacity, where the vertical axis represents the capacity of the motor 1 and the horizontal axis represents the pilot pressure Pi. (See Patent Document 2 for FIG. 5).

That is, when the pilot pressure Pi is not supplied, the spool 3a of the spool valve 3 moves to the left side by the spring force of the spring 3b, the flow paths 11 and 12 are blocked, and no pressure is applied to the second piston 2b. On the other hand, since the motor driving pressure Pa or Pb acts on the first piston 2a, the tilt angle of the swash plate, that is, the capacity of the motor 1 is maximum (high torque low speed rotation).
When an arbitrary pilot pressure Pi is supplied, the swash plate is tilted by an angle corresponding to the level of the pilot pressure Pi, the capacity of the motor 1 is reduced, and the rotational speed is increased to a constant value.
Further, even when the pilot pressure Pi is changed, the swash plate is tilted by an angle corresponding to the level of the changed pilot pressure Pi, so that a new capacity and rotation speed of the motor 1 are determined. When the pilot pressure Pi is maximized, the capacity of the motor 1 is minimized (low torque high speed rotation).

When the load increases or the capacity of the motor 1 decreases and the motor driving pressure Pa or Pb tends to exceed the rated value, the pressure compensation valve 5 functions to avoid a pressure increase above the rated value (preventing overload) Controlled). That is, when the motor driving pressure Pa or Pb exceeding the rated value acts from the flow path 13, the spool of the pressure compensation valve 5 moves and switches, and the flow paths 10 and 11 for supplying hydraulic oil to the second piston 2b are shut off. If necessary, the hydraulic oil of the second piston 2b is opened to the return side (tank port). Therefore, regardless of the supplied pilot pressure Pi, further reduction in the capacity of the motor 1 is prevented, and further increase in the rotational speed of the motor 1 and further increase in the motor driving pressure Pa or Pb are prevented. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 5-126103 JP 2004-76910 A

  Although the control device for the variable displacement hydraulic motor according to the above-described conventional example is extremely useful, there may be a problem in the components of the control device. For example, when a mechanical failure or a trouble that the pressure compensation valve 5 of the control device is stuck at the non-switching position due to the biting of dust occurs, the capacity of the motor 1 is minimized regardless of the motor driving pressure. Can be.

  By the way, for example, when the motor 1 is used for driving a hoisting winch, the pressure acting on the motor 1 (from the relationship between the winch shaft torque necessary for holding the suspended load in the air and the capacity of the motor 1 ( Holding pressure). Further, in order to cut the surge pressure that is generated when the suspended load is lowered while the hoisting winch is lowered, as shown in the one-dot chain line in FIG. Between the counter balance valve 6a and the counter balance valve 6a, a flow path 15 generally including an overload relief valve 15a is disposed. The relief pressure of the overload relief valve 15a is set to be higher than the relief pressure of a main relief valve (not shown) provided in the motor drive circuit (channels 6 and 7) in order to prevent the relief at the normal time. .

  However, if the above-mentioned trouble occurs in the pressure compensation valve 5 in a state where the suspended load is lifted in the air by the hoisting winch, the pressure of the pressure equal to or higher than the constant pressure control set value is obtained when the capacity of the motor 1 is small. Will act. For example, when the suspended load is heavy, the holding pressure of the motor 1 may exceed the relief set pressure of the overload relief valve 15a. Then, the overload relief valve 15a is opened, and a closed circuit is configured on the motor side of the counter balance valve 6a. Therefore, there is a risk that the motor 1 will stall and the suspended load lifted by the hoisting winch may fall, leading to a major accident. The same applies not only to such a hoisting winch but also to a boom hoisting winch (boom collapses) and a traveling purpose (the traveling body stalls on a downhill).

  Therefore, an object of the present invention is to provide a control device for a variable displacement hydraulic motor that makes it possible to prevent the motor from stalling even if a trouble occurs in the pressure compensation valve of the control device.

  In order to solve the above problems, the means adopted by the variable displacement hydraulic motor control device according to claim 1 of the present invention is the first piston for increasing the tilt angle of the swash plate of the motor and the tilt angle being reduced. A hydraulic piston having a second piston that moves through a spool that switches the supply of fluid to the second piston according to the pilot pressure and a feedback lever that transmits the displacement of the swash plate. A sleeve that cuts off the supply of fluid, and has a spool valve that uniquely determines the tilt angle. When the motor drive pressure supplied to the motor via the motor drive circuit reaches a predetermined value, the supply pressure to the second piston is reduced. A pressure compensation valve that controls the motor drive pressure so that the motor drive pressure does not exceed a predetermined value is stopped. In a variable displacement hydraulic motor control device equipped with a load relief valve and equipped with a negative brake that brakes the motor by stopping supply of brake release pressure, it exceeds the set pressure of the main relief valve provided in the motor drive circuit and overloads When a pressure lower than the set pressure of the relief valve is selected, the brake release pressure supply to the negative brake is stopped, and a negative brake forced switching control valve is provided that self-holds the switching operation with this brake release pressure. It is characterized by.

  The variable displacement hydraulic motor control device according to claim 2 of the present invention employs a hydraulic system having a first piston that increases the tilt angle of the swash plate of the motor and a second piston that decreases the tilt angle. A spool that includes a piston and switches supply of fluid to the second piston in accordance with pilot pressure; and a sleeve that moves through a feedback lever that transmits displacement of the swash plate to block supply of fluid to the second piston Comprising a spool valve that uniquely determines the tilt angle, and when the motor driving pressure supplied to the motor via the motor driving circuit reaches a predetermined value, the supply of the supply pressure to the second piston is stopped, and the motor driving pressure Including a pressure compensation valve that controls so as not to exceed a predetermined value, an overload relief valve disposed between the counter balance valve of the motor drive circuit and the motor, In a variable displacement hydraulic motor control device having a negative brake that brakes a motor by stopping supply of rake release pressure, a pressure detector that detects motor drive pressure and supply of brake release pressure to the negative brake can be stopped The pressure detection value signal is received from the electromagnetic switching valve and the pressure detector, and the motor drive pressure exceeds the set pressure of the main relief valve provided in the motor drive circuit, and at a predetermined pressure less than the set pressure of the overload relief valve. When it is determined that there is a controller, a controller for stopping the supply of the brake release pressure to the negative brake by outputting a switching command signal to the electromagnetic switching valve and holding the state by itself is provided. .

  The variable displacement hydraulic motor control device according to claim 3 of the present invention employs the variable displacement hydraulic motor control device according to claim 2, wherein the controller has a motor drive pressure that is a motor drive circuit. When it is detected that the pressure is higher than the set pressure of the main relief valve provided in the valve and less than the set pressure of the overload relief valve, the alarm is activated based on the pressure value signal detected by the pressure detector. It has a function of outputting an alarm command.

In the control apparatus for a variable displacement hydraulic motor according to the first aspect of the present invention, even if a trouble occurs in which the spool is fixed in the non-switching position due to mechanical failure, dust trapping, or the like, the overpressure is not exceeded. The negative brake forced switching control valve is switched at a pressure lower than the set pressure of the load relief valve, and the state is maintained. Therefore, according to the control apparatus for a variable displacement hydraulic motor according to the first aspect of the present invention, the motor is braked by the negative brake, so that the motor is prevented from stalling. It should be noted that the predetermined pressure for the switching control must exceed the set pressure of the main relief valve provided in the motor drive circuit, so that the maximum output state of the motor in the normal state (maximum capacity and the motor drive pressure is the main pressure). The negative brake forced switching control valve is not switched even in the output state with the relief valve set pressure), and the brake forced switching control valve is switched only in an abnormal state.

  In the control device for a variable displacement hydraulic motor according to claim 2 of the present invention, even if a trouble occurs in which the spool is fixed at the non-switching position due to mechanical failure or dust trapping, etc. The electromagnetic switching valve for forcibly switching the negative brake is switched at a pressure lower than the set pressure of the load relief valve, and the state is maintained. Therefore, according to the control device for a variable displacement hydraulic motor according to claim 2 of the present invention, the motor is braked by the negative brake, so that the motor is prevented from stalling. It should be noted that the predetermined pressure for the switching control must exceed the set pressure of the main relief valve provided in the motor drive circuit, so that the maximum output state of the motor in the normal state (maximum capacity and the motor drive pressure is the main pressure). The electromagnetic switching valve that forcibly switches the negative brake is not switched even in the output state with the relief valve set pressure), and the brake forced switching control valve is switched only in an abnormal state.

  According to the control apparatus for a variable displacement hydraulic motor according to claim 3 of the present invention, if a trouble occurs in which the pressure compensation valve is stuck in the non-switching position due to a mechanical failure, dust trapping, or the like, an alarm is generated. Since the alarm is issued from the container, it can be known that the spool has been stuck in the non-switching position due to a mechanical failure of the pressure compensation valve or the entry of dust.

  The motor control apparatus according to Embodiments 1 to 3 of the present invention will be described below. First, a motor control apparatus according to Embodiment 1 of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a motor control apparatus according to Embodiment 1 of the present invention. The difference between the motor control device according to the first embodiment of the present invention and the configuration of the motor control device according to the conventional example is well understood in the comparison between FIG. 1 and FIG. The supply of the brake release pressure Po to the negative brake that brakes the motor is stopped. Therefore, the same points as those in the conventional example and those having the same functions are denoted by the same reference numerals, and different points are mainly described with the same names.

  That is, the flow path 20 branches from the flow path 9 that branches from the flow path 8 and supplies the motor driving pressure Pa or Pb to the hydraulic piston 2. The flow path 20 communicates with the negative brake 21 and passes through the flow path 22 for supplying the brake release pressure Po to the negative brake 21. It communicates with one of the pilot switching sections. This negative brake forced switching control valve 23 normally communicates with the flow path 22, and the motor drive pressure Pa or Pb exceeds the set pressure Pp of a main relief valve (not shown) provided in the motor drive circuit, and is overloaded. When the pressure reaches a predetermined pressure Pw (Pp <Pw <Pr) lower than the set pressure Pr of the relief valve 15a, the flow is cut off to stop the supply of the brake release pressure Po to the negative brake 21, and this brake The switching operation is configured to be held by the release pressure Po.

  Hereinafter, the operation mode of the motor control apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 5 in sequence. This is because when the pilot pressure supplied to the spool valve 3 is Pib and the capacity of the motor 1 is at the minimum capacity qa (see FIG. 5), the pressure compensation valve 5 is mechanically damaged or bite. Trouble occurs and the spool is stuck in the non-switching position despite the switching pressure (the higher of the motor driving pressure Pa or Pb selected by the shuttle valve 8a), preventing overload. This is when it stops functioning.

  Even if the motor driving pressure reaches the predetermined operating pressure Ps, the overload prevention of the pressure compensation valve 5 does not function, and when the motor driving pressure reaches the predetermined pressure Pw, the predetermined pressure Pw is forced through the flow path 20 to force the negative brake. It acts on one pilot switching portion of the two systems of the switching control valve 23. Therefore, the negative brake forced switching control valve 23 is switched, and the negative brake release pressure Po supplied to the negative brake 21 becomes the tank pressure, while the negative pilot forced switching control valve 23 has a negative pilot switching portion. Brake release pressure Po acts.

  Therefore, according to the motor control apparatus of the first embodiment of the present invention, the rotation of the motor 1 is braked, so that the motor 1 does not stall. Even if the supply pressure of the motor 1 decreases due to the switching operation of the negative brake forced switching control valve 23, the pilot pressure Pib acts on the other pilot switching portion of the negative brake forced switching control valve 23. Since the switching state of the brake forced switching control valve 23 continues to be maintained, there is no fear that switching hunting will occur.

In the case of the motor control device according to the first embodiment of the present invention, in addition to the decrease in the motor driving pressure, the brake release pressure Po itself decreases (for example, the tank pressure), resulting in a negative brake. The switching of the forced switching control valve 23 is reset. Therefore, even if the negative brake forced switching control valve 23 is switched once, the motor 1 can be driven in the same condition as in the normal state within the condition range where there is no stall after the dangerous state is avoided.
On the other hand, when the pressure compensation valve 5 operates normally, the pilot pressure supplied to the spool valve 3 is Pia or less, the capacity of the motor 1 is the maximum capacity qb (see FIG. 5), and the motor Even if the drive pressure of 1 (the pressure of Pa or Pb higher) is the set pressure Pp of the main relief valve (not shown), the pressure of the flow path 20 is the pressure of the negative brake forced switching valve 23. Since the switching pressure Pw (Pp <Pw <Pr) is not reached, the negative brake forced switching valve 23 is not switched. That is, in the motor control apparatus according to Embodiment 1 of the present invention, when the pressure compensation valve 5 operates normally, the negative brake forced switching valve 23 does not switch and operates, and the rotation of the motor 1 The negative brake 21 is not forced to brake.

  Hereinafter, a motor control apparatus according to Embodiment 2 of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a circuit diagram of a motor control apparatus according to Embodiment 2 of the present invention. The difference between the motor control device according to the second embodiment of the present invention and the configuration of the motor control device according to the first embodiment is well understood in the comparison between FIG. 1 and FIG. In addition, the configuration of the pressure compensation valve is different from the configuration of the negative brake forced switching control valve. Therefore, the same points as those in the first embodiment are denoted by the same reference numerals, and different points are mainly described with the same names.

  The pressure compensation valve 5 ′ of the motor control device according to the second embodiment of the present invention is of a type that operates with a differential pressure (Pa−Pb) = Ps between the motor driving pressures Pa and Pb. Further, the negative brake forced replacement control valve 23 'has three pilot switching units, and two of these three pilot switching units are arranged to face each other. The negative brake forced switching control valve 23 'is switched when the differential pressure between the motor driving pressure Pa and Pb becomes Pw (Pp <Pw <Pr).

  More specifically, the pilot switching unit is disposed on the side opposite to the pilot switching unit that communicates with the channel 13 to which the motor driving pressure Pa is supplied from the channel 6 of the pressure compensation valve 5 ′, that is, on the side where the spring 5b is provided. Has been. A flow path 18 branched from the flow path 7 to which the motor driving pressure Pb is supplied communicates with the pilot switching portion. That is, the pressure compensation valve 5 'is configured to operate with a differential pressure (Pa-Pb) between the motor driving pressure Pa and Pb. Further, a flow path 19 is branched from a flow path 7 for supplying the motor driving pressure Pb to the motor 1, and this flow path 19 is opposite to the pilot switching portion where the flow path 24 of the negative brake forced switching control valve 23 'communicates. It communicates with a pilot switching section that is arranged oppositely on the side. That is, the negative brake forced switching control valve 23 'is configured to switch when the differential pressure (predetermined pressure) Pw between the motor driving pressure Pa and Pb becomes a pressure between Pp and Pr.

  Hereinafter, an operation mode of the motor control device according to the second embodiment of the present invention will be described. That is, even if the differential pressure of the motor driving pressure reaches the predetermined operating pressure Ps, the overload prevention of the pressure compensation valve 5 'does not function, and when the differential pressure of the motor driving pressure reaches the predetermined pressure Pw, negative brake forced switching control Valve 23 'is switched. Then, while the negative brake release pressure Po supplied to the negative brake 21 becomes the tank pressure, the negative brake release pressure Po acts on the other pilot switching portion of the negative brake forced switching control valve 23 '.

Therefore, according to the motor control device according to the second embodiment of the present invention, the rotation of the motor 1 is braked. Therefore, the motor braking device according to the fourth embodiment of the present invention is related to the third embodiment. It is the same effect as a motor braking device. The negative brake forced switching control valve 23 ′ may be configured such that the pressure compensation valve 5 ′ operates with absolute pressure (motor drive pressure Pa, pressure on the high pressure side of Pb).
Further, even when the pressure compensation valve 5 'operates normally, the negative brake does not forcibly brake the rotation of the motor 1 as in the motor control device according to the third embodiment.

Hereinafter, a motor control apparatus according to Embodiment 3 of the present invention will be described with reference to the accompanying drawings. FIG. 3 is a circuit diagram of a motor control apparatus according to Embodiment 3 of the present invention. The difference between the motor control device according to the third embodiment of the present invention and the configuration of the motor control device according to the second embodiment is well understood in the comparison between FIG. 2 and FIG. In addition, an electromagnetic switching valve 25 is provided in the flow path 22 for supplying the brake release pressure P ₀ to the negative brake 21 instead of the negative brake forced switching control valve 23 ′. This is the point to be controlled. Therefore, the same points as those in the second embodiment and those having the same functions are denoted by the same reference numerals, and different points are mainly described with the same names.

That is, the flow path 22 for supplying the brake release pressure P ₀ communicates with the chamber on the side where the braking spring of the negative brake 21 is compressed via the electromagnetic switching valve 25 at the 3 port 2 position. The electromagnetic switching valve 25 is controlled by a controller 26 that receives a signal of a pressure detection value from each of pressure detectors 27 and 28 that detect the motor driving pressure Pa of the flow path 6 and the motor driving pressure Pb of the flow path 7. It is configured to be switched.

The controller 26 detects that the pressure detection values of the motor drive pressures Pa and Pb input from the pressure detectors 27 and 28 exceed the set pressure Pp of a main relief valve (not shown) provided in the motor drive circuit, and the overload relief valve. When it is determined that the predetermined pressure Pw ₂ (Pp <Pw ₂ <Pr) set in advance is lower than the set pressure Pr of 15 a, a switching command signal is output to switch the electromagnetic switching valve 25, and to the negative brake 21. It stops the supply of the brake releasing pressure P _0, and is configured to switch the state of the electromagnetic switching valve 25 so as to self-hold. Further, when the controller 26 determines that the pressure is the predetermined pressure Pw _2, it outputs an alarm command signal for issuing an abnormality alarm to the alarm device 29 in conjunction with the output of the switching command signal to the electromagnetic switching valve 25. It is configured.

Hereinafter, an operation mode of the motor control device according to the third embodiment of the present invention will be described. That is, even if the motor drive pressure becomes actuated predetermined pressure Ps without overload preventing function of the pressure compensating valve 5 ', when the motor driving pressure reaches a predetermined pressure Pw _2, controller 26 of the pressure detector 27 It is determined from the pressure detection value signals inputted from each of them that the overload prevention of the pressure compensation valve 5 'is not functioning. Then, the controller 26 outputs a switching signal to the electromagnetic switching valve 25, since thereby switching operation of the electromagnetic selector valve 25, is cut off the flow passage 22, the supply stop of the brake release pressure P ₀ to the negative brake 21 Is done.

(0057 of the original application)
Therefore, according to the control apparatus of a motor according to a third embodiment of the present invention, it switched to the brake release pressure P ₀ is tank pressure (substantially zero), the motor 1 is braked by the negative brake 21 is actuated, The motor 1 does not stall. Once the switching signal is output from the controller 26, the electromagnetic switching valve 26 continues to be self-held unless the reset condition is satisfied, so there is no fear that switching hunting will occur. On the other hand, when the pressure compensation valve 5 'operates normally, the pilot pressure supplied to the spool valve 3 is Pia or less, and the capacity of the motor 1 is the maximum capacity qb (see FIG. 5). Even when the driving pressure (Pa-Pb) of the motor 1 is the maximum output state of the motor 1 which is a set pressure Pp of a main relief valve (not shown), the controller 26 detects the pressure input from the pressure detectors 27 and 28, respectively. Since it is not judged from the value signal that the overload prevention of the pressure compensation valve 5 ′ is not functioning, a switching signal is not output to the electromagnetic switching valve 25. That is, in the case of the motor control apparatus according to Embodiment 6 of the present invention, when the pressure compensation valve 5 'operates normally, the electromagnetic switching valve 25 does not switch and operates, and the motor 1 rotates. The negative brake 21 is not forced to brake.

  Therefore, according to the motor control device of the third embodiment of the present invention, the electromagnetic switching valve 25 is switched only when an abnormality occurs, and at the same time, an abnormality alarm is issued from the alarm device 29. It is possible to know that an abnormality has occurred in the device. And even if an abnormality occurs in the control device of the motor 1, it is known that the motor 1 does not stall and there is no fear that the suspended load will fall, so that a panic occurs in the driving operation after the abnormality occurs. The excellent effect of being able to cope with deposition can be obtained.

  Note that the motor control devices according to the first to third embodiments of the present invention are only specific examples of the present invention, and thus are limited to the motor control devices according to the first to seventh embodiments. In addition, the design can be freely changed without departing from the technical idea of the present invention.

1 is a circuit diagram of a motor control device according to Embodiment 1 of the present invention. FIG. It is a circuit diagram of the control apparatus of the motor which concerns on Embodiment 2 of this invention. It is a circuit diagram of the control apparatus of the motor which concerns on Embodiment 3 of this invention. It is a circuit diagram of the control apparatus of the motor which concerns on a prior art example. FIG. 5 is an explanatory diagram of the relationship between pilot pressure and motor capacity, with the vertical axis representing the motor capacity and the horizontal axis representing the pilot pressure Pi.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Hydraulic piston, 2a ... 1st piston, 2b ... 2nd piston 3 ... Spool valve, 3a ... Spool, 3b ... Spring, 3c ... Sleeve 4 ... Connecting means, 4a ... Feedback lever, 4b ... Pin 5 ... pressure compensation valve, 5 '... pressure compensation valve, 5a ... spool, 5b ... spring 6 ... flow path, 6a ... counter balance valve 7 ... flow path 8 ... flow path, 8a ... shuttle valve 9 ... flow path, 10 ... flow Road, 11 ... Channel, 12 ... Channel, 13 ... Channel, 14 ... Channel 15 ... Channel, 15a ... Overload relief valve 18 ... Channel, 19 ... Channel, 20 ... Channel 21 ... Negative brake DESCRIPTION OF SYMBOLS 22 ... Flow path 23 ... Negative brake forced switching control valve, 23 '... Negative brake forced switching control valve 24 ... Channel 25 ... Electromagnetic switching valve 26 ... Controller 27 ... Pressure detector 28 ... Pressure detector 29 ... Alarm

Claims (3)

  A spool that includes a hydraulic piston having a first piston that increases the tilt angle of the swash plate of the motor and a second piston that decreases the tilt angle, and switches the supply of fluid to the second piston in accordance with the pilot pressure; It has a spool valve that moves through a feedback lever that transmits the displacement of the swash plate and cuts off the supply of fluid to the second piston, and uniquely determines the tilt angle. When the motor drive pressure supplied to the motor reaches a predetermined value, the supply pressure to the second piston is stopped, and a pressure compensation valve is provided to control the motor drive pressure so that it does not exceed the predetermined value. Variable with an overload relief valve arranged between the valve and the motor, and a negative brake that brakes the motor by stopping the supply of brake release pressure In a control device for a quantity hydraulic motor, the pressure is switched when it exceeds the set pressure of the main relief valve provided in the motor drive circuit and less than the set pressure of the overload relief valve, and the brake release pressure is supplied to the negative brake. A control apparatus for a variable displacement hydraulic motor, characterized by being provided with a negative brake forced switching control valve that stops and self-holds the switching operation by the brake release pressure.   A spool that includes a hydraulic piston having a first piston that increases the tilt angle of the swash plate of the motor and a second piston that decreases the tilt angle, and switches the supply of fluid to the second piston in accordance with the pilot pressure; It has a spool valve that moves through a feedback lever that transmits the displacement of the swash plate and cuts off the supply of fluid to the second piston, and uniquely determines the tilt angle. When the motor drive pressure supplied to the motor reaches a predetermined value, the supply pressure to the second piston is stopped, and a pressure compensation valve is provided to control the motor drive pressure so that it does not exceed the predetermined value. Variable with an overload relief valve arranged between the valve and the motor, and a negative brake that brakes the motor by stopping the supply of brake release pressure In a control device for a quantity hydraulic motor, a pressure detector that detects motor driving pressure, an electromagnetic switching valve that can stop the supply of brake release pressure to the negative brake, and a pressure detection value signal from the pressure detector are received. When it is determined that the motor drive pressure exceeds the set pressure of the main relief valve provided in the motor drive circuit and is less than the set pressure of the overload relief valve, a switch command signal is output to the electromagnetic switching valve. A controller for a variable displacement hydraulic motor, characterized in that a controller is provided to stop the supply of brake release pressure to the negative brake by self-holding the state.   When the controller detects that the motor drive pressure exceeds the set pressure of the main relief valve provided in the motor drive circuit and is less than the set pressure of the overload relief valve, the controller detects it. 3. The control apparatus for a variable displacement hydraulic motor according to claim 2, further comprising a function of outputting an alarm command to the alarm device based on the pressure value signal.

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