JP4127282B2 - 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.
The variable displacement hydraulic motor control apparatus according to this conventional example will be described below with reference to FIG. 5 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. 6 of the explanatory diagram of the relationship between the pilot pressure and the motor capacity, where the vertical axis indicates the capacity of the motor 1 and the horizontal axis indicates the pilot pressure Pi. (See Patent Document 2 for FIG. 6 ).

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 becomes maximum, the capacity of the motor 1 becomes minimum (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, and an overload is provided between the counter balance valve of the motor drive circuit and the motor. In a control device for a variable displacement hydraulic motor equipped with a load relief valve, the motor driving pressure is switched when the pressure compensation valve operation exceeds a predetermined operating pressure and becomes a predetermined pressure lower than a set pressure of the overload relief valve. In addition to stopping the supply of the supplied pilot pressure, a forcible switching control valve that self-holds the switching operation at this pilot pressure is provided.

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 There comprising a pressure compensating valve for controlling so as not to exceed a predetermined value, and e Bei the overload relief valve disposed between the counterbalance valve and the motor of the motor drive circuit The control apparatus for varying displacement hydraulic motor, and receives a pressure detector for detecting a motor driving pressure, the electromagnetic switching valve capable of stopping the supply of pilot pressure to the spool valve, the signal of the pressure detection value from the pressure detector exceeds the operating predetermined pressure of the motor driving pressure is the pressure compensating valve, when it is determined that the Ru predetermined pressure der less than the set pressure of the overload relief valve, self its state to output the switching command signal to the electromagnetic switching valve A controller is provided that stops the supply of pilot pressure to the spool valve by holding.

Means for variable displacement hydraulic motor of the control device is adopted according to claim 3 of the present invention, in the control device of the variable displacement hydraulic motor according to claim 2, stopping the supply of pilot pressure to the spool valve The obtained electromagnetic switching valve also has a function of an electromagnetic proportional pressure reducing valve that controls the pilot pressure .

  In the control apparatus for a variable displacement hydraulic motor according to claim 1 of the present invention, even if a trouble occurs in which the spool is fixed at the non-switching position due to mechanical failure of the pressure compensation valve, biting of dust, etc., the motor The forced switching control valve is switched when the driving pressure exceeds the predetermined pressure of the pressure compensation valve and less than the set pressure of the overload relief valve, and the switching operation of the forced switching control valve is self-maintained by the pilot pressure. Therefore, the spool valve is switched and hydraulic oil escapes from the second piston, and is pushed by the first piston to increase the tilt angle of the swash plate, thereby maximizing the capacity and lowering the motor driving pressure. Therefore, according to the control device for a variable displacement hydraulic motor according to the first aspect of the present invention, the operation of the overload relief valve due to overload is prevented, so that the motor can be prevented from stalling.

In the control apparatus 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 in the non-switching position due to mechanical failure of the pressure compensation valve or biting of dust, the motor The supply of the pilot pressure to the spool valve is stopped when the driving pressure exceeds the predetermined operating pressure of the pressure compensation valve and is lower than the set pressure of the overload relief valve. Therefore, the spool valve is switched and hydraulic oil escapes from the second piston, and is pushed by the first piston to increase the tilt angle of the swash plate, thereby maximizing the capacity and lowering the motor driving pressure. Therefore, according to the control device for a variable displacement hydraulic motor according to claim 2 of the present invention, the operation of the overload relief valve due to overload is prevented, so that the motor stall can be prevented beforehand.

According to the variable displacement hydraulic motor control apparatus of the third aspect of the present invention, the electromagnetic switching valve that stops the supply of the pilot pressure and switches the motor capacity to the maximum capacity when the abnormality is detected is an electromagnetic that controls the pilot pressure. Since it also functions as a proportional pressure reducing valve, it can be made cheaper than the control device for the variable displacement hydraulic motor according to claim 2 .

The motor control apparatus according to Embodiments 1 to 4 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 motor control device according to the conventional example is that the pilot supply pressure is well understood in the comparison between FIG. 1 and FIG. The flow path 14 for supplying Pi communicates with the spool valve via a forced switching control valve having a configuration described later, and the other main components are the same. 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 16 branches from the flow path 10 that branches from the flow path 8 and supplies the motor driving pressure Pa or Pb to the pressure compensation valve 5. The flow path 16 communicates with one of the two systems of pilot switching portions of the 4-port 2-position forced switching control valve 17 through which the flow path 14 for supplying the pilot supply pressure Pi passes. The forced switching control valve 17 normally communicates the flow path 14, and the motor driving pressure Pa or Pb exceeds the predetermined operating pressure Ps of the pressure compensation valve 5, and is a predetermined pressure lower than the set pressure Pr of the overload relief valve 15a. When Pw is reached, the flow is switched to shut off the flow path 14, the supply of the pilot pressure Pi supplied to the spool valve 3 is stopped, and the switching operation is held by the pilot pressure Pi.

Hereinafter, an operation mode of the motor control device according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 6 sequentially. The operation mode of this motor control device is that the pressure compensation valve is in a state where the pilot pressure supplied to the spool valve 3 is Pib and the capacity of the motor 1 is the minimum capacity qa (see FIG. 6 ). No mechanical switching or dust catching trouble occurred in No. 5, and the spool is not switched even though the switching pressure (the motor driving pressure Pa or Pb selected by the shuttle valve 8a) is higher. This is the case when overload prevention stops functioning because it is stuck in place.

That is, even if the motor driving pressure supplied from the motor driving circuit to the motor 1 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 acts on one pilot switching portion of the two systems of the forced switching control valve 17 via the flow path 16. The forced switching control valve 17 is switched by the action of the predetermined pressure Pw, and the pilot pressure Pib supplied to the spool valve 3 becomes the tank pressure (substantially zero), while the other pilot switching unit of the forced switching control valve 17 The pilot pressure Pib acts.
Therefore, as shown in FIG. 9, since the capacity of the motor 1 becomes the maximum capacity qb and the motor driving pressure decreases, the motor driving pressure reaches the set pressure Pr of the overload relief valve 15a. Nothing will happen.

  Therefore, according to the motor control device of the first embodiment of the present invention, the operation of the overload relief valve 15a due to overload is prevented, and a closed circuit is configured on the motor side of the counter balance valve 6a. Therefore, the motor 1 can be prevented from stalling. Even if the motor drive pressure decreases, the pilot pressure Pib acts on the other pilot switching portion of the forced switching control valve 17 as described above, and the switching state of the forced switching control valve 17 continues to be maintained. Therefore, 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 pilot pressure Pi itself that uniquely controls the capacity of the motor 1 is decreased (for example, Pia or less). Thus, the switching of the forced switching control valve 17 is reset. Therefore, even if the forced switching control valve 17 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.

  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 forced switching control valve. Therefore, the same components as those in the motor control device according to the first embodiment are denoted by the same reference numerals, and the differences are mainly described with the same names.

  That is, the pressure compensation valve 5 ′ of the motor control apparatus according to the second embodiment of the present invention is of a type that operates according to the differential pressure (Pa−Pb) = Ps between the motor driving pressures Pa and Pb. The forced switching control valve 17 'has a three-line pilot switching unit, and two of these pilot switching units are arranged to face each other. The forced switching control valve 17 ′ is switched when the differential pressure between the motor driving pressures Pa and Pb becomes Pw (Ps <Pw <Pr).

  More specifically, the pilot switching section is arranged on the side opposite to the pilot switching section where the flow path 13 to which the motor driving pressure Pa is supplied from the flow path 6 of the pressure compensation valve 5 'communicates, that is, on the side where the spring 5b is provided. It is installed. 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 by a differential pressure (Pa-Pb) between the motor driving pressure Pa and Pb. A flow path 19 is branched from the flow path 7 for supplying the motor driving pressure Pb to the motor 1, and this flow path 19 is on the opposite side of the pilot switching portion to which the flow path 16 of the forced switching control valve 17 'communicates. It communicates with a pilot switching section that is arranged oppositely. That is, the forced switching control valve 17 'is configured to switch when the differential pressure (predetermined pressure) Pw between the motor driving pressures Pa and Pb becomes a pressure between Ps 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 (Pa−Pb) of the motor driving pressure reaches the predetermined operating pressure Ps, the overload prevention of the pressure compensation valve 5 does not function, and the differential pressure (Pa−Pb) of the motor driving pressure is the predetermined pressure. When Pw is reached, the forced switching control valve 17 'is switched. Accordingly, since the capacity of the motor 1 becomes the maximum capacity qb and the motor driving pressure decreases, the motor control device according to the second embodiment is the same as the motor control device according to the first embodiment. It is effective. The forced switching control valve 17 ′ may be applied to a control device in which the pressure compensation valve 5 ′ operates with absolute pressure (motor driving pressure Pa, pressure on the high pressure side of Pb).

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. Incidentally, as a control apparatus of a motor according to a third embodiment of the present invention, where different from the structure of a control apparatus of a motor according to the conventional example, is well understood in comparison with FIG. 3 and FIG. 5, The flow path 14 for supplying the pilot supply pressure Pi communicates with the spool valve 3 via the electromagnetic switching valve 25, and a controller 26 for switching and controlling the electromagnetic switching valve 25 is provided. 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 14 for supplying the pilot supply pressure Pi communicates with the pilot switching portion of the spool valve 3 through the electromagnetic switching valve 25 at the 3 port 2 position. This electromagnetic switching valve 25 is switch-controlled by a controller 26 that receives a pressure detection value signal from pressure detectors 27 and 28 that detect the pressure of the motor driving pressure Pa of the flow path 6 and the motor driving pressure Pb of the flow path 7. It has come to be. Then, the controller 26 detects that the detected pressure values of the motor driving pressures Pa and Pb inputted from the pressure detectors 27 and 28 exceed the predetermined operating pressure Ps of the pressure compensation valve 5 ′, and the set pressure of the overload relief valve 15a. When it is determined that the predetermined pressure Pw ₁ (Ps <Pw ₁ <Pr) set in advance is less than Pr, a switching command signal is output to switch the electromagnetic switching valve 25, and the pilot pressure Pi to the spool valve 3 is switched. While the supply is stopped, the switching state of the electromagnetic switching valve 25 is held by itself.

Hereinafter, the operation mode of the motor control apparatus according to the third embodiment of the present invention will be described with reference to FIGS. 3 and 6 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 the minimum capacity qa (see FIG. 6 ), the pressure compensating valve 5 ' Even if a biting trouble occurs and the differential pressure (Pa-Pb) exceeds the predetermined operating pressure Ps, the spool of the pressure compensation valve 5 'is stuck in the non-switching position, so that overload prevention does not function. This is the case.

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 _1, the controller 26 from the pressure detector 27 It is determined from the input pressure detection value signal that the overload prevention of the pressure compensation valve 5 'is not functioning. Therefore, the controller 26 transmits a switching signal to the electromagnetic switching valve 25 and switches the electromagnetic switching valve 25 to shut off the flow path 14 to stop the supply of the pilot pressure Pib to the spool valve 3.

Therefore, according to the motor control apparatus according to the third embodiment of the present invention, the motor 1 has the maximum capacity qb and the motor driving pressure is reduced. Therefore, the motor driving pressure is set to the overload relief valve 15a. The pressure Pr is not reached. Further, 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 that there is no fear that switching hunting occurs.

Hereinafter, a motor control apparatus according to Embodiment 4 of the present invention will be described with reference to the accompanying drawings. Figure 4 is a circuit diagram of a motor control device according to a fourth embodiment of the present invention. Incidentally, as a control apparatus of a motor according to a fourth embodiment of the present invention, where different from the structure of a control apparatus of a motor according to the third embodiment may be better understood in comparison of FIG. 3 and FIG. 4 In addition, the electromagnetic switching valve 25 interposed in the flow path 14 for supplying the pilot supply pressure Pi is replaced with an electromagnetic proportional pressure reducing valve 25 'having a known configuration. Therefore, the same points as those in the fifth embodiment are denoted by the same reference numerals, and different points are mainly described with the same names.

  That is, the flow path 14 for supplying the pilot supply pressure Pi communicates with the pilot switching portion of the spool valve 3 via the three-port electromagnetic proportional pressure reducing valve 25 '. The electromagnetic proportional pressure reducing valve 25 ′ is received by a controller 26 that receives a signal of a pressure detection value from pressure detectors 27 and 28 that detect the pressure of the motor driving pressure Pa in the flow path 6 and the motor driving pressure Pb in the flow path 7. It is configured to be controlled.

Hereinafter, an operation mode of the motor control device according to the fourth embodiment of the present invention will be described. That is, when the motor drive pressures Pa and Pb reach Pw ₁ , the controller 26 determines that the motor drive pressures Pa and Pb have reached Pw ₁ from the pressure detection values input from the pressure detectors 27 and 28, and Since a control signal is transmitted to the electromagnetic proportional pressure reducing valve 25 ', the electromagnetic proportional pressure reducing valve 25' is pressure-reduced. Therefore, the pressure value of the pilot pressure input to the spool valve 3 is switched from Pib to the tank pressure (substantially zero). Therefore, according to the motor control apparatus of the seventh embodiment of the present invention, the capacity of the motor 1 returns to the maximum capacity qb (see FIG. 6 ), and the motor driving pressure supplied to the motor 1 decreases. Since the motor drive pressure does not reach the set pressure Pr of the overload relief valve 15a, the motor control device according to the seventh embodiment of the present invention is the same as the motor control device according to the third embodiment. It is effective.

The motor control devices according to the first to fourth embodiments of the present invention are only specific examples of the present invention, and are thus limited to the motor control device 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 Embodiment 4 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 Path, 11 ... flow path, 12 ... flow path, 13 ... flow path, 14 ... flow path 15 ... flow path, 15a ... overload relief valve 16 ... flow path 17 ... forced flow rate switching control valve, 17 '... forced flow rate switching Control valve 18 ... channel, 19 ... channel,
25 ... Electromagnetic switching valve, 25 '... Electromagnetic proportional pressure reducing valve 26 ... Controller 27 ... Pressure detector 28 ... Pressure detector

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. In a control device for a variable displacement hydraulic motor having an overload relief valve disposed between a valve and a motor, the motor drive pressure is a pressure compensation valve. When the specified pressure exceeds the set pressure of the overload relief valve, the pilot pressure is switched, and the pilot pressure supplied to the spool valve is stopped and the switching operation is forcibly held by this pilot pressure. A control apparatus for a variable displacement hydraulic motor, comprising a switching control valve. 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. the control device of the variable displacement hydraulic motor that example Bei the disposed the overload relief valve between the valve and the motor, the pressure detection for detecting a motor driving pressure When the electromagnetic switching valve capable of stopping the supply of pilot pressure to the spool valve, receives the signal of the pressure detection value from the pressure detector, the motor drive pressure exceeds the operating predetermined pressure of the pressure compensating valve, overload relief valve when it is determined that the Ru predetermined pressure der of less than the set pressure, is provided a controller to stop the supply of pilot pressure to the spool valve by the state self-hold outputs a switching command signal to the electromagnetic switching valve A control apparatus for a variable displacement hydraulic motor. 3. The variable displacement hydraulic motor according to claim 2, wherein the electromagnetic switching valve capable of stopping the supply of the pilot pressure to the spool valve also functions as an electromagnetic proportional pressure reducing valve for controlling the pilot pressure . Control device.

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