Patent Publication Number: US-7591214-B2

Title: Driving motor controlling device of construction machine

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates to a driving motor controlling device of a construction machine, which has a driving motor connected to a pump and a tank through a swivel joint and a motor control valve for switching a state for connecting the pump and the tank to the driving motor such that the driving motor is controlled to any one of a stop state, a normal rotation state, and a reverse rotation state. 
   2. Related Art 
   A driving motor controlling device of a construction machine (hereinafter, referred to as driving motor controlling device) which has a driving motor and a motor control valve for controlling an operation state of the driving motor is known as an example of related art (see Japanese Unexamined Patent Application Publication No. 60-249707). In the driving motor controlling device disclosed in Japanese Unexamined Patent Application Publication No. 60-249707, the motor control valve is integrally formed with control valves for controlling the operation of actuators different from the driving motor, and disposed in an upper body of the construction machine which is higher than a swivel joint. When the construction machine having the driving motor controlling device is operated in an environment which a temperature is low, such as a cold region in winter, since viscosity of hydraulic oil becomes higher upon start-up, a warming up operation is first performed. When the warming up operation is performed, hydraulic oil is circulated from the pump to the tank through the control valves and thus becomes warm. 
   However, in the construction machine having the driving motor controlling device disclosed in Japanese Unexamined Patent Application Publication No. 60-249707, when the warming up operation is performed, the hydraulic oil is circulated from the pump to the tank through the control valves, but is not circulated from the motor control valve to the driving motor. Accordingly, the hydraulic oil which becomes warm by the warming up operation does not flow between the motor control valve and the driving motor and thus the motor control valve and the driving motor remains cold even when the warming up operation is performed. At this state, when the construction machine begins to be driven, the warm hydraulic oil is rapidly fed to the cold driving motor and thus heat balance of the driving motor is lost. In other words, a portion of the driving motor which is in contact with the warm hydraulic oil rapidly becomes warm, whereas the other thereof remains cold. In the driving motor controlling device disclosed in Japanese Unexamined Patent Application Publication No. 60-249707, when the construction machine begins to be driven after the warming up operation, an operation fault or failure of the driving motor may be caused due to a difference in thermal expansion. 
   In addition, a counterbalance valve was generally used for preventing cavitation of the driving motor from being created. However, in order to simplify the structure of the valve, the driving motor controlling device disclosed in Japanese Unexamined Patent Application Publication No. 60-249707 realizes a structure for preventing cavitation from being created although the counterbalance valve is not used. In this driving motor controlling device, a main selector valve  14 A provided in a circuit for connecting a hydraulic pump  10 A to an actuator  12  which is a hydraulic motor is switched by controlling a pilot valve  28 . Furthermore, pressure reduction valves  30   a  and  30   b  which reduce a set pressure in a conduit line between a pilot valve  28  and a pilot chamber provided at the both sides of the main selector valve  14 A according to the reduction in the pump pressure which is caused by the hydraulic oil from the pump  10 A are provided. 
   However, in the driving motor controlling device disclosed in Japanese Unexamined Patent Application Publication No. 60-249707, in order to allow the main selector valve  14 A to be switched from a neutral position, the pressure reduction valves  30   a  and  30   b  need be formed such that passages  26   a  and  26   b  between the remote control valve  28  and the pilot chamber of the main selector valve  14 A are sufficiently communicated with each other in an initial state of the switching operation in which a load is not generated in a passage  56  of a discharge side of the pump  10 A. In this driving motor controlling device, when the construction machine begins to be self-propelled on a downhill road to reduce the pressure of the passage  56 , the pressure may not be sufficiently reduced by the pressure reduction valves  30   a  and  30   b  in the initial state of the switching operation and the cavitation may be created in the driving motor. 
   In order to prevent the cavitation from being created due to the above-described reason, the pressure reduction valves  30   a  and  30   b  may be formed such that an opening degree of the passage  56  between the remote control valve  28  and the pilot chamber of the main selector valve  14 A is reduced in the initial state of the switching operation. However, when the pressure reduction valves  30   a  and  30   b  are formed as described above, a pilot pressure which acts on the pilot chamber of the main selector valve  14 A is reduced in the initial state of the switching operation (hydraulic oil fed to the pilot chamber is reduced) and thus the switching operation of the main selector valve  14 A is delayed and rising of a driving speed upon the start-up is delayed. 
   SUMMARY OF THE INVENTION 
   A first advantage of the present invention is to provide a driving motor controlling device of a construction machine, which is capable of suppressing heat balance of a driving motor from being lost when the construction machine begins to be driven after a warming up operation and suppressing an operation fault or failure of the driving motor due to a difference in thermal expansion in the driving motor. 
   A second advantage of the present invention is to provide a driving motor controlling device of a construction machine, which is capable of more surely suppressing cavitation from being created although a counterbalance valve is not used and preventing rising of a driving speed from being delayed upon start-up. 
   According to a first aspect of the invention for realizing the first advantage, there is provided a driving motor controlling device of a construction machine, included in the construction machine having a swivel joint interposed between an upper body and a lower body, the device comprising including a driving motor which is connected to a pump and a tank through the swivel joint, and a motor control valve which switches a state for connecting the pump and the tank to the driving motor such that the driving motor is controlled to a stop state, a normal rotation state, or a reverse rotation state, wherein the motor control valve has a neutral position for the stop state, a normal rotation position for the normal rotation state, and a reverse rotation position for the reverse rotation state, and is switched to the neutral position, the normal rotation position, or the reverse rotation position, based on a command from a control device manipulated by a operator and a pressure of an inflow side of hydraulic oil into the driving motor, wherein the motor control valve is disposed in the lower body in which the driving motor is disposed, and is integrally formed with the driving motor, and wherein, upon a warming up operation, the hydraulic oil discharged from the pump is circulated to the tank disposed in the upper body through the swivel joint and the motor control valve. 
   By this configuration, when a warming up operation of the construction machine is performed, the hydraulic oil discharged from the pump to the motor control valve disposed in the lower body in which the driving motor is disposed is circulated. Accordingly, the motor control valve becomes warm by the hydraulic oil which becomes warm by circulation, and thus the driving motor integrally formed with the motor control valve becomes warm. By this configuration, in the driving motor controlling device of the construction machine, when the construction machine begins to be driven after the warming up operation, the heat balance of the driving motor is prevented from being lost and thus the operation fault or failure of the driving motor due to the difference in the thermal expansion in the driving motor can be suppressed. 
   The motor control valve may be tandem-connected or serial-connected to control valves of hydraulic actuators different from the driving motor and may be provided at downstream of the control valves of the hydraulic actuators. 
   By this configuration, the hydraulic oil fed from the pump passes through the control valve of the hydraulic actuators and is fed to the motor control valve. Accordingly, pressure loss due to the length of the pipe which more becomes longer by a length corresponding to the motor control valve disposed in the lower body does not affect the hydraulic actuators. Therefore, it is possible to suppress energy efficiency from be reduced. 
   Furthermore, according to a second aspect of the invention, there is provided a driving motor controlling device of a construction machine, included in the construction machine having a swivel joint interposed between an upper body and a lower body, the device comprising a driving motor which is connected to a pump and a tank through the swivel joint, and a motor control valve which switches a state for connecting the pump and the tank to the driving motor such that the driving motor is controlled to a stop state, a normal rotation state, or a reverse rotation state, wherein the motor control valve has a neutral position for the stop state, a normal rotation position for the normal rotation state, and a reverse rotation position for the reverse rotation state, and is switched to the neutral position, the normal rotation position, or the reverse rotation position, based on a command from a control device manipulated by a operator and a pressure of an inflow side of hydraulic oil into the driving motor. 
   The driving motor controlling device of the construction machine related to the second aspect of the invention has the following several features in order to realize the first advantage. In other words, the driving motor controlling device of the construction machine related to the second aspect of the invention has each of the following features or a combination thereof. 
   A first feature of the driving motor controlling device of the construction machine related to the second aspect of the invention for realizing the first advantage is as follows: The driving motor controlling device further includes an electrical remote controller which is the control device for converting an amount controlled by the operator into an electrical signal; a detector which detects the pressure of the inflow side and converts the pressure into an electrical signal; a control unit which outputs a control signal based on the electrical signal from the electrical remote controller and the electrical signal from the detector; and an electro-hydraulic valve which generates a pilot pressure based on the control signal from the control unit, the motor control valve is disposed in the lower body in which the driving motor is disposed, and is integrally formed with the driving motor, and, upon a warming up operation, the hydraulic oil discharged from the pump is circulated to the tank disposed in the upper body through the swivel joint and the motor control valve. 
   By this configuration, when a warming up operation of the construction machine is performed, the hydraulic oil discharged from the pump to the motor control valve disposed in the lower body in which the driving motor is disposed is circulated. Accordingly, the motor control valve becomes warm by the hydraulic oil which becomes warm by circulation, and thus the driving motor integrally formed with the motor control valve becomes warm. By this configuration, in the driving motor controlling device of the construction machine, when the construction machine begins to be driven after the warming up operation, the heat balance of the driving motor is prevented from being lost and thus the operation fault or failure of the driving motor due to the difference in the thermal expansion in the driving motor can be suppressed. 
   In addition, when the construction machine is switched from the driving state to the stop state on a downhill road, an outflow side of the hydraulic oil from the driving motor has a high pressure. Accordingly, the existing driving motor controlling device of the construction machine need use a pipe which has a high strength to bear up against the high pressure between the motor control valve and the driving motor. Thus, an expensive pipe is required. However, according to the driving motor controlling device, since the motor control valve is integrally formed with the driving motor, a pipe for connecting the motor control valve and the driving motor is not required. 
   Furthermore, by this configuration, the electro-hydraulic valve is controlled to generate the pilot pressure based on a command from the electrical remote controller by the control unit and the result of detecting the pressure of the inflow side of the driving motor by the detector. Thus, the motor control valve can be operated by the pilot pressure. Accordingly, response delay is low and the motor control valve can be accurately or rapidly operated based on the pressure of the inflow side of the driving motor and the command from the electrical remote controller which is the control device. 
   A second feature of the driving motor controlling device of the construction machine related to the second aspect of the invention is as follows: The control unit and the electro-hydraulic valve are disposed in the upper body, the detector is mounted in the driving motor, the detector and the control unit are connected to each other through a snap ring disposed in the swivel joint, and the electro-hydraulic valve and the motor control valve are connected to each other through the swivel joint. 
   By this configuration, since the detector for detecting the pressure of the inflow side of the driving motor is mounted in the driving motor, detection of the pressure can be more suppressed from being delayed, compared with a case where the pipe is provided from the inflow side of the driving motor to the upper body through the swivel joint to be connected to the detector. In addition, a response to the change in the pressure of the inflow side of the driving motor is suppressed from being delayed and thus the motor control valve can be rapidly operated with respect to the change in the pressure of the inflow side of the driving motor, thereby suppressing cavitation from being created in the driving motor. In addition, the response to the change in the pressure of the inflow side of the driving motor is suppressed from being delayed and thus hunting can be suppressed from being generated in the operation of the motor control valve. 
   A third feature of the driving motor controlling device of the construction machine related to the second aspect of the invention is as follows: The motor control valve has a detecting port which is connected to the detector and induces the pressure of the inflow side detected by the detector, and wherein, in the normal rotation state, the detecting port is connected to a passage which becomes the inflow side in the normal rotation state, and in the reverse rotation state, the detecting port is connected to another passage which becomes the inflow side in the reverse rotation state. 
   By this configuration, the pressure of the inflow side of the driving motor which is induced to the detector is selected by the motor control valve and thus the passage which becomes the inflow side in the normal rotation position and the passage which becomes the inflow side in the reverse rotation position need not have the respective detectors, thereby sharing the detector. 
   In addition, a fourth feature of the driving motor controlling device of the construction machine related to the second aspect of the invention is as follows: A negative brake which is operated in the stop state is connected to the detecting port. 
   By this configuration, by combining a port for the negative brake and a port for the detecting port, the number of the ports may not increase in mounting the detector, thereby preventing the device from being enlarged. 
   According to a third aspect of the invention, there is provided a driving motor controlling device of a construction machine, including a driving motor which is connected to a pump and a tank through a swivel joint, and a motor control valve which switches a state for connecting the pump and the tank to the driving motor such that the driving motor is controlled to a stop state, a normal rotation state, or a reverse rotation state, and wherein the motor control valve has a neutral position for the stop state, a normal rotation position for the normal rotation state, and a reverse rotation position for the reverse rotation state, and is switched to the neutral position, the normal rotation position, or the reverse rotation position, based on a command from a control device manipulated by a operator and a pressure of an inflow side of hydraulic oil into the driving motor. 
   The driving motor controlling device of the construction machine related to the third aspect of the invention has the following several features in order to realize the second advantage. In other words, the driving motor controlling device of the construction machine related to the third aspect of the invention has each of the following features or a combination thereof. 
   A first feature of the driving motor controlling device of the construction machine related to the third aspect of the invention for realizing the second advantage is as follows: The driving motor controlling device further includes a remote control valve which is the control device for generating a pilot pressure; a first pilot chamber which is provided in the motor control valve and on which the pilot pressure for switching and operating the motor control valve acts; a pilot pressure control valve which switches a connection state between the remote control valve and the first pilot chamber and has a discharge position for connecting the first pilot chamber to the tank and a feed position for connecting the remote control valve to the first pilot chamber; a spring which is disposed at one side of the pilot pressure control valve to bias the pilot pressure control valve toward the discharge position; a second pilot chamber which is disposed at the other side of the pilot pressure control valve and on which the pressure of the inflow side acts such that the pilot pressure control valve is biased toward the feed position; and a starting passage which connects the remote control valve to the first pilot chamber through the motor control valve, and the remote control valve is connected to the first pilot chamber through the starting passage until the pilot pressure control valve is switched to the feed position, and the starting passage is blocked by the motor control valve when the pilot pressure control valve is switched to the feed position. 
   The remote control valve is connected to the first pilot chamber through the starting passage even until the pilot pressure control valve is switched to the feed position. Accordingly, the pilot pressure control valve can be formed such that the opening in the discharge position becomes narrower or is blocked and thus a sufficient pilot pressure can act on the first pilot chamber even until the pilot pressure control valve is switched to the feed position. Thus, it is possible to prevent the rising of the driving speed from be delayed due to the delay of the switching operation in an initial state of a time when the motor control valve is switched from the neutral position. After the pilot pressure control valve is switched to the feed position, the starting passage is blocked by the motor control valve and thus the pilot pressure acts on the first pilot chamber only through the pilot pressure control valve. 
   When the construction machine begins to be self-propelled and thus the pressure of the inflow side of the hydraulic oil into the driving motor is reduced, the pressure of the hydraulic oil acting on the second pilot chamber is reduced. Accordingly, the pilot pressure control valve is switched to the discharge position by the bias force of the spring and thus the passage between the remote controller valve and the pilot chamber more becomes narrower or is blocked. Thus, the motor control valve is moved toward the neutral position and thus the outflow side of the hydraulic oil from the driving motor becomes narrower. Accordingly, it is possible to suppress the cavitation of the driving motor from being created. 
   Accordingly, by this configuration, it is possible to provide a driving motor controlling device of a construction machine which is capable of more surely suppressing the cavitation from being created although the counterbalance valve is not used in the driving motor controlling device of the construction machine and preventing the rising of the driving speed upon the start-up from being delayed. 
   In addition, a second feature of the driving motor controlling device of the construction machine related to the third aspect of the invention is as follows: When the motor control valve is switched from the neutral position to the normal rotation position or the reverse rotation position, the starting passage is blocked and an outflow side of the hydraulic oil from the driving motor is then connected to the tank. 
   By this configuration, when the motor control valve is switched from the neutral position, the starting passage is first blocked and the outflow side of the driving motor and the tank are then connected to each other. Accordingly, even when the construction machine begins to be self-propelled upon the switching operation and thus the pressure of the outflow side of the driving motor is reduced, the outflow side of the driving motor is blocked by the motor control valve until the starting passage is blocked. Thus, the cavitation can be more suppressed from being created. 
   Furthermore, a third feature of the driving motor controlling device of the construction machine related to the third aspect of the invention is as follows: When the motor control valve is switched from the neutral position to the normal rotation position or the reverse rotation position, an outflow side of the hydraulic oil from the driving motor is connected to the tank and the starting passage is then blocked. 
   By this configuration, although the construction machine begins to be self-propelled upon the switching operation, the pressure of the outflow side of the driving motor is reduced, and thus the pilot pressure control valve is not sufficiently switched to the feed position, since the pilot pressure acts on the first pilot chamber through the starting passage, the outflow side of the driving motor in the motor control valve is not rapidly blocked and thus impact can be suppressed from being generated. 
   Furthermore, the driving motor controlling device of the construction machine related to the third aspect of the invention is characterized in that the motor control valve is a center bypass control valve, and an opening degree of a center bypass passage is set such that, when the starting passage is blocked, the pressure which can switch the pilot pressure control valve to the feed position against a bias force of the spring is generated in the inflow side of the driving motor and acts on the second pilot chamber, even in a state that a discharge amount of the pump is a minimum. 
   By this configuration, since a path in which the pilot pressure acts on the first pilot chamber can be smoothly switched to a passage from the starting passage through the pilot pressure control valve, impact generated upon the start-up of the driving motor, that is, impact generated when switching the pilot pressure control valve can be reduced. 
   In addition, in a case where the invention applies to the driving motor controlling device of the construction machine having the second feature, before the driving motor is initiated and the outflow side is opened, the path in which the pilot pressure acts on the first pilot chamber is switched to the passage through the pilot pressure control valve. Thus, it is possible to prevent impact from being generated in the driving motor when switching the pilot pressure control valve. 
   Furthermore, the above and other objects, features and advantages of the invention will be more apparent from the following description, referring to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements, and wherein: 
       FIG. 1  is a view showing a hydraulic circuit included in a driving motor controlling device of a construction machine related to a first embodiment of the invention; 
       FIG. 2  is a view explaining a change in an opening area of a passage when a position of a motor control valve is switched in the driving motor controlling device shown in  FIG. 1 ; 
       FIG. 3  is a view showing a hydraulic circuit included in a driving motor controlling device of a construction machine related to a second embodiment of the invention; and 
       FIG. 4  is a view showing the hydraulic circuit included in the driving motor controlling device of the construction machine related to the second embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, embodiments according to the invention will be described with reference to the accompanying drawings. 
   First Embodiment 
     FIG. 1  is a view showing a hydraulic circuit included in a driving motor controlling device of a construction machine related to a first embodiment of the invention. As shown in  FIG. 1 , the construction machine in which a hydraulic circuit  10  is disposed has a lower body including a crawler body and an upper body disposed thereon, and a swivel joint  11  is disposed between the lower body and the upper body. In this construction machine, at least two hydraulic pumps such as a first pump  12  and a second pump  13  and a tank  14  are provided in the upper body. In addition, in the upper body, various kinds of hydraulic actuators to which hydraulic oil is fed from the pumps  12  and  13  are provided. In the lower body, a driving motor connected to the pumps  12  and  13  and the tank  14  through the swivel joint  11  is provided. In addition, in this construction machine, a right driving motor  20  and a left driving motor are provided, but only the right driving motor  20  is shown in  FIG. 1 . In the upper body, a bucket cylinder for operating a bucket, a boom cylinder for operating a boom, a circling (swing) motor, and an arm cylinder for operating an arm are provided as hydraulic actuators different from the driving motor. 
   Furthermore, as shown in  FIG. 1 , the hydraulic circuit  10  of the construction machine includes a main control valve  15  provided in the upper body and a driving motor controlling device  1  of the construction machine related to the present embodiment (hereinafter, referred to as driving motor controlling device  1 ). 
   The main control valve  15  includes a swing direction switching valve  16  for controlling the feed of hydraulic oil into the circling motor, an arm direction switching valve  17  for controlling the feed of the hydraulic oil into the arm cylinder, a bucket direction switching valve  18  for controlling the feed of the hydraulic oil into the bucket cylinder, and a boom direction switching valve  19  for controlling the feed of the hydraulic oil into the boom cylinder. In addition, the swing direction switching valve  16  and the arm direction switching valve  17  are connected to the downstream of the first pump  12  and the bucket direction switching valve  18  and the boom direction switching valve  19  are connected to the downstream of the second pump  13 . 
   The driving motor controlling device  1  has the right driving motor  20  and the left driving motor. Furthermore, the driving motor controlling device  1  has a motor control valve  21 , a remote control valve  22 , a pilot pressure control valve  23  ( 23   a  and  23   b ), all of which are included in the right driving motor  20 , and a motor control valve, a remote control valve, and a pilot pressure control valve, all of which are not shown and are included in the left driving motor (In  FIG. 1 , only those included in the right driving motor  20  are shown). In addition, in the following description on the driving motor controlling device  1 , only the right driving motor  20  and the motor control valve  21  thereof will be described, and the left driving motor and the motor control valve thereof will be omitted in order to avoid repetition. 
   The driving motor  20  of the driving motor controlling device  1  is disposed in the lower body as described above and the motor control valve  21  and the pilot pressure control valve  23  are also disposed in the lower body. Meanwhile, the remote control valve  22  is disposed in the upper body. In addition, the motor control valve  21  is integrally mounted in the driving motor  20 . Furthermore, the motor control valve  21  is tandem-connected or serial-connected to the control valves  16 ,  17 ,  18 , and  19  of the other hydraulic actuators and provided at the downstream of the control valves  16  to  19  of the other hydraulic actuators. 
   The motor control valve  21  switches a state for connecting the pumps  12  and  13  and the tank  14  to the driving motor  20  such that the driving motor  20  is controlled to any one of a stop state, a normal rotation state (a state that the construction machine rotates forward), and a reverse rotation state (a state that the construction machine rotates backward). The motor control valve  21  has a neutral position  21   a , normal rotation positions  21   b  and  21   c , and reverse rotation positions  21   d  and  21   e . When the motor control valve  21  is switched to the neutral position  21   a , the driving motor  20  is in the stop state. When the driving motor control valve  21  is switched to the normal rotation position  21   b  (or  21   c ), the driving motor  20  is in the normal rotation state, and, when the driving motor control valve  21  is switched to the reverse rotation position  21   d  (or  21   e ), the driving motor  20  is in the reverse rotation state. As described below, the motor control valve  21  is switched to any one of the neutral position  21   a , the normal rotation positions  21   b  and  21   c , and the reverse rotation positions  21   d  and  21   e , based on a command from the remote control valve  22  and a pressure of an inflow side of the hydraulic oil into the driving motor  20 . 
   In addition, a pilot chamber  24  ( 24   a  and  24   b ) on which a pilot pressure for switching the motor control valve  21  acts are provided in the motor control valve  21 . The pilot pressure acts on the pilot chamber  24   a  such that the motor control valve  21  is switched in the order of the neutral position  21   a , the normal rotation position  21   b , and the normal rotation position  21   c , and pilot pressure acts on the pilot chamber  24   b  such that the motor control valve  21  is switched in the order of the neutral position  21   a , the reverse rotation position  21   d , and the reverse rotation position  21   e . The pilot pressure which acts on the pilot chamber  24  is generated by the remote control valve  22 . In other words, the remote control valve  22  configures a control device for generating a command due to the pilot pressure based on the manipulation of an operator (not shown) of the construction machine. In addition, the pilot chamber  24  configures a first pilot chamber in the present embodiment. 
   Furthermore, the driving motor controlling device  1  includes a pilot pressure control valve  23  for switching a connection state between the remote control valve  22  and the pilot chamber  24  of the motor control valve  21 , a spring  26  and a pilot chamber  27  provided in the pilot pressure control valve  23 , and a starting passage  28 . 
   The pilot pressure control valve  23  includes a pilot pressure control valve  23   a  for switching the connection state between the remote control valve  22  and the pilot chamber  24   a  and a pilot pressure control valve  23   b  for switching the connection state between the remote control valve  22  and the pilot chamber  24   b . In addition, the pilot pressure control valve  23  includes a discharge position  25   a  for connecting the pilot chamber  24  to the tank  14  and a feed position  25   b  for connecting a passage  29  in which the pilot pressure is induced from the remote control valve  22  to the pilot chamber  24 . 
   The spring  26  is disposed at one side of the pilot pressure control valve  23  and biases the pilot pressure control valve  23  in a direction in which the pilot pressure control valve  23  is switched to the discharge position  25   a . Meanwhile, the pilot chamber  27  is disposed at the other side of the pilot pressure control valve  23 . The pressure of the inflow side of the hydraulic oil into the driving motor  20  acts on the pilot chamber  27  through the passage  30  such that the pilot pressure control valve  23  is biased in a direction in which the pilot pressure control valve  23  is switched to the feed position  25   b . In addition, the pilot chamber  27  configures a second pilot chamber in the present embodiment. 
   The motor control valve  21  is switched and operated by switching the pilot pressure control valve  23  by the pilot pressure control valve  23 , the spring  26 , and the pilot chamber  27  having the above-described configuration. For example, when the pressure of the inflow side of the hydraulic oil into the driving motor  20  acts on the pilot chamber  27  of the pilot pressure control valve  23   a  and thus the pilot pressure control valve  23   a  is switched to the feed position  25   b  against the bias force of the spring  26 , the pilot pressure from the remote control valve  22  induced through the passage  29  acts on the pilot chamber  24   a . Accordingly, the motor control valve  21  is switched to the normal rotation position  21   b  or  21   c . Meanwhile, when the bias force due to the action of the hydraulic oil on the pilot chamber  27  is reduced with respect to the bias force of the spring  26  and thus the pilot pressure control valve  23   a  is switched to the discharge position  25   a , the hydraulic oil which acts the pilot pressure on the pilot chamber  24   a  is discharged to the tank  14  through an throttle  31 . In addition, the motor control valve  21  is switched in the order of the normal rotation position  21   c , the normal rotation position  21   b , and the neutral position  21   a.    
   The starting passage  28  ( 28   a  and  28   b ) connects the remote control valve  22  to the pilot chamber  24  through the motor control valve  21 . The starting passage  28   a  connects the remote control valve  22  to the pilot chamber  24   a  and the starting passage  28   b  connects the remote control valve  22  to the pilot chamber  24   b . Furthermore, a portion of the starting passage  28  is configured in a passage formed in the motor control valve  21  and connects the remote control valve  22  to the pilot chamber  24  when the motor control valve  21  is in the neutral position  21   a . In addition, when the motor control valve  21  is in the normal rotation positions  21   b  and  21   c , the starting passage  28   a  is blocked and, when the motor control valve  21  is in the reverse rotation positions  21   d  and  21   e , the starting passage  28   b  is blocked. 
   Next, an operation of the driving motor controlling device  1  will be described.  FIG. 1  shows a state which the motor control valve  21  is in the neutral position  21   a . In this state, the driving motor  20  is in the stop state. When the construction machine including the driving motor controlling device  1  is operated in an environment in which a temperature is low, such as a cold region in winter, a warming up operation is first performed. Upon the warming up operation, the pumps  12  and  13  are operated and the hydraulic oil is circulated in a state that the hydraulic oil is not fed to the hydraulic actuators (in a state that the control valves are not operated). 
   At this time, the hydraulic oil discharged from the pumps  12  and  13  becomes warm while being circulated to the tank  14  through the control valves  16 ,  17 ,  18 ,  19 , and  21 . Then, the hydraulic oil is also circulated in a path which reaches the tank  14  disposed in the upper body through the swivel joint  11  and the motor control valve  21 . In other words, upon the warming up operation, the hydraulic oil discharged from the pumps  12  and  13  is circulated to the motor control valve  21  disposed in the lower body in which the driving motor  20  is disposed. Accordingly, the motor control valve  21  also becomes warm by the hydraulic oil which becomes warm by circulation and the driving motor  20  integrally formed with the motor control valve  21  also becomes warm. 
   After the warming up operation, the left and right driving motors are initiated and the construction machine begins to be driven. Here, when the driving motor is operated in the normal rotation state such that the construction machine is moved forward, the right driving motor  20  will be described. In this case, first, the remote control valve  22  is manipulated by the operator such that a pilot pressure of a forward drive command (driving command of the normal rotation direction) which acts through the passage  32  is generated. 
   When the pilot pressure of the forward drive command is generated, since the motor control valve  21  is in the neutral position  21   a , the starting passage  28   a  is in a continuous state and the pilot pressure acts on the pilot chamber  24   a  through the starting passage  28   a . At this time, the pilot pressure control valve  23   a  which is at the downstream of the starting passage  28   a  is in the discharge position  25   a  by the bias force of the spring  26 , because the pressure of an inflow side of the hydraulic oil into the driving motor  20  is low. Thus, the hydraulic oil which generates the pilot pressure acting on the pilot chamber  24   a  through the starting passage  28   a  is discharged to the tank  14 . However, since the throttle  31  is provided in a path which reaches the tank  14  such that an opening degree thereof is adequately reduced, the pilot pressure required for switching and operating the motor control valve  21  is controlled to act on the pilot chamber  24   a  through the starting passage  28   a.    
   When the pilot pressure acts on the pilot chamber  24   a  through the starting passage  28   a , the motor control valve  21  is switched to the normal rotation position  21   b . Accordingly, the hydraulic oil is fed in a direction in which the driving motor  20  rotates in the normal rotation state and thus the construction machine begins to be moved forward. In addition, when the hydraulic oil begins to be fed to the driving motor  20 , since the pressure of the inflow side of the hydraulic oil into the driving motor  20  increases, the increased pressure acts on the pilot chamber  27  of the pilot pressure control valve  23   a  through the passage  30 . Accordingly, the pilot pressure control valve  23   a  is switched to the feed position  25   b  against the bias force of the spring  26  and the pilot pressure acts on the pilot chamber  24   a  through the passage  29  such that the motor control valve  21  is switched to and held in the normal position  21   b  or  21   c . In addition, in the state that the motor control valve  21  is switched to the normal position  21   b  or  21   c , the starting passage  28   a  is blocked. In the driving motor controlling device  1 , the remote control valve  22  and the pilot chamber  24  are connected to each other through the starting passage  28  until the pilot pressure control valve  23  is switched to the feed position  25   a , and the starting passage  28  is blocked by the motor control valve  21  when the pilot pressure control valve  23  is switched to the feed position  25   a.    
   Now, the switching of the motor control valve  21  from the neutral position  21   a  will be described in detail.  FIG. 2  is a view explaining a change in an opening area of a passage when a motor control valve  21  which is a center bypass control valve is switched from the neutral position  21   a  to the normal rotation positions  21   b  and  21   c  or the reverse rotation positions  21   d  and  21   e . In addition, in  FIG. 2 , the change in the opening area of a passage (P→N) which is a center bypass passage between a point P and a point N, a passage (P→Ma) between the point P and a point Ma (an inflow side of the hydraulic oil upon the normal rotation of the driving motor  20 ), a passage (Mb→T) between a point Mb (an outflow side of the hydraulic oil upon the normal rotation of the driving motor  20 ) and the tank  14 , and a passage (R→Pa) which is the starting passage  28  between a point R and a point Pa. Furthermore, in  FIG. 2 , as the change in the opening area of the passage (R→Pa), a pattern I and a pattern II are exemplified. The pattern I shows a case where the starting passage  28  is formed in the motor control valve  21  such that the opening area is changed along a locus denoted by (R→Pa-I) in the drawing. Meanwhile, the pattern II shows a case where the starting passage  28  is formed in the motor control valve  21  such that the opening area is changed along a locus denoted by a dotted line (R→Pa-II) 
   The motor control valve  21  begins to be switched from the neutral position  21   a  to the normal rotation positions  21   b  and  21   c , the opening degree of the center bypass passage (P→N) decreases and the opening degree of the passage (P→Ma) of the inflow side of the driving motor  20  increases. At this time, the starting passage  28 , that is, passage (R→Pa), is in the continuous state. In addition, in the pattern I, when the motor control valve  21  is switched from the neutral position  21   a  to the normal rotation positions  21   b  and  21   c , the passage (R→Pa) which is the starting passage  28  is blocked and the passage (Mb→T) between the outflow side of the hydraulic oil from the driving motor  20  and the tank  14  is then connected. Meanwhile, in the pattern II, when the motor control valve  21  is switched from the neutral position  21   a  to the normal rotation positions  21   b  and  21   c , the passage (Mb→T) is connected and the passage (R→Pa) which is the starting passage  28  is then blocked. 
   Furthermore, even in any one of the pattern I and the pattern II, when the starting passage  28  is blocked, the opening degree of the center bypass passage (P→N) is set to a predetermined opening degree ΔA. The opening degree ΔA is set such that a pressure which can switch the pilot pressure control valve  23   a  to the feed position  25   b  against the bias force of the spring  26  is generated in the inflow side of the driving motor  20  and acts on the pilot chamber  24   a  even in a state that a discharge amount of the pumps  12  and  13  is a minimum. 
   In the above-described driving motor controlling device  1 , when the warming up operation of the construction machine is performed, the hydraulic oil discharged from the pumps  12  and  13  is circulated to the motor control valve  21  disposed in the lower body in which the driving motor  20  is disposed. Accordingly, the motor control valve  21  becomes warm by the hydraulic oil which becomes warm by circulation and the driving motor  20  integrally formed with the motor control valve  21  also becomes warm. Thus, according to the driving motor controlling device  1 , when the construction machine begins to be driven after the warming up operation, the heat balance of the driving motor  20  is prevented from being lost and thus the operation fault or failure of the driving motor  20  due to the difference in the thermal expansion in the driving motor  20  can be suppressed. 
   In addition, when the construction machine is switched from the driving state to the stop state on the downhill road, the outflow side of the hydraulic oil from the driving motor  20  has a high pressure. Accordingly, the existing driving motor controlling device of the construction machine need use a pipe which has a high strength to bear up against the high pressure between the motor control valve and the driving motor. Thus, an expensive pipe is required. However, according to the driving motor controlling device  1 , since the motor control valve  21  is integrally formed with the driving motor  20 , a pipe for connecting the motor control valve  21  and the driving motor  20  is not required. 
   Furthermore, in the driving motor controlling device  1 , the motor control valve  21  is tandem-connected (or serial-connected) to the control valves of the hydraulic actuators different from the driving motor  20  and is provided at the downstream of the control valves  16  to  19  of the hydraulic actuators. Accordingly, the hydraulic oil fed from the pumps  12  and  13  passes through the control valves  16  to  19  of the hydraulic actuators and is fed to the motor control valve  21 . Thus, pressure loss due to the length of the pipe which more becomes longer by a length corresponding to the motor control valve  21  disposed in the lower body does not affect the hydraulic actuators. Therefore, it is possible to suppress the energy efficiency from be reduced. 
   In the driving motor controlling device  1 , the remote control valve  22  is connected to the pilot chamber  24  through the starting passage  28  even until the pilot pressure control valve  23  is switched to the feed position  25   b . Accordingly, by providing the throttle  31 , the pilot pressure control valve  23  can be formed such that the opening in the discharge position  25   a  becomes narrower and thus a sufficient pilot pressure can act on the pilot chamber  24  even until the pilot pressure control valve is switched to the feed position  25   b . Thus, it is possible to prevent the rising of the driving speed from be delayed due to the delay of the switching operation in an initial state of a time when the motor control valve  21  is switched from the neutral position  21   a . After the pilot pressure control valve  23  is switched to the feed position  25   b , the starting passage  28  is blocked by the motor control valve  21  and thus the pilot pressure acts on the pilot chamber  24  only through the pilot pressure control valve  23 . 
   In the driving motor controlling device  1 , when the construction machine begins to be self-propelled and thus the pressure of the inflow side of the hydraulic oil into the driving motor  20  is reduced, the pressure of the hydraulic oil acting on the pilot chamber  27  is reduced. Accordingly, the pilot pressure control valve  23  is switched to the discharge position  25   a  by the bias force of the spring  26  and thus the passage between the remote controller valve  22  and the pilot chamber  24  more becomes narrower or is blocked. Thus, the motor control valve  21  is moved toward the neutral position  21   a  and thus the outflow side of the hydraulic oil from the driving motor  20  becomes narrower. Accordingly, it is possible to suppress the cavitation of the driving motor  20  from being created. 
   Accordingly, according to the driving motor controlling device  1 , it is possible to more surely suppress the cavitation from being created although the counterbalance valve is not used in the driving motor controlling device of the construction machine and to prevent the rising of the driving speed upon the start-up from being delayed. 
   Furthermore, in the driving motor controlling device  1  which is formed such that the opening area of the starting passage  28  in the motor control valve  21  is changed to the pattern I, when the motor control valve  21  is switched from the neutral position  21   a , the starting passage  28  is first blocked and the outflow side of the driving motor  20  and the tank  14  are connected to each other. Accordingly, even when the construction machine begins to be self-propelled upon the switching operation and thus the pressure of the outflow side of the driving motor  20  is reduced, the outflow side of the driving motor  20  is blocked by the motor control valve  21  until the starting passage  28  is blocked. Thus, the cavitation can be more suppressed from being created. 
   In addition, in the driving motor controlling device  1  which is formed such that the opening area of the starting passage  28  in the motor control valve  21  is changed to the pattern II, the construction machine begins to be self-propelled upon the switching operation and the pressure of the outflow side of the driving motor  20  is reduced. Thus, although the pilot pressure control valve  23  is not sufficiently switched to the feed position  25   b , since the pilot pressure acts on the pilot chamber  24  through the starting passage  28 , the outflow side of the driving motor  20  in the motor control valve  21  is not rapidly blocked and thus impact can be suppressed from being generated. 
   Moreover, in the driving motor controlling device  1 , the opening degree of the center bypass passage (P→N) is set to the predetermined opening degree ΔA. Accordingly, since a path in which the pilot pressure acts on the pilot chamber  24  can be smoothly switched to a passage from the starting passage  28  through the pilot pressure control valve  23 , impact generated upon the start-up of the driving motor  20 , that is, impact generated when switching the pilot pressure control valve  23  can be reduced. In addition, in the driving motor controlling device  1  which is formed such that the opening area of the starting passage  28  in the motor control valve  21  is changed to the pattern II, before the driving motor  20  is initiated and the outflow side is opened, the path in which the pilot pressure acts on the pilot chamber  24  is switched to the passage through the pilot pressure control valve  23 . Thus, it is possible to prevent impact from being generated in the driving motor  20  when switching the pilot pressure control valve  23 . 
   Second Embodiment 
   Next, a second embodiment of the invention will be described.  FIGS. 3 and 4  are views showing a hydraulic circuit included in a driving motor controlling device of a construction machine related to a second embodiment of the invention. The construction machine having the hydraulic circuit  110  shown in  FIGS. 3 and 4  includes a lower body including a crawler body and an upper body disposed thereon, and a swivel joint  111  is interposed between the upper body and the lower body (see  FIG. 2 ). 
   In this construction machine, similar to the construction machine described in the first embodiment, at least two hydraulic pumps, such as a first pump  112  and a second pump  113 , and a tank  114  are disposed in the upper body. In addition, in the upper body, various kinds of hydraulic actuators to which the hydraulic oil is fed from the pumps  112  and  113  are provided. In the lower body, a driving motor connected to the pumps  112  and  113  and the tank  114  through the swivel joint  111  is provided. In addition, in this construction machine, a right driving motor  120  and a left driving motor are provided, but only the right driving motor  120  is shown in  FIG. 4 . Meanwhile, in the upper body, a bucket cylinder for operating a bucket, a boom cylinder for operating a boom, and a circling (swing) motor, an arm cylinder for operating an arm are provided as hydraulic actuators different from the driving motor. 
   Furthermore, the hydraulic circuit  110  of the construction machine includes a main control valve  115  provided in the upper body as shown in  FIG. 3 , and a driving motor controlling device  2  of the construction machine related to the present embodiment (hereinafter, referred to as driving motor controlling device  2 ) as shown in  FIG. 4 . In addition, the hydraulic oil from the pumps  112  and  113  is first fed to the main control valve  115  and the driving motor controlling device  2  located at the downstream of the main control valve  115  through the main control valve  115  and the swivel joint  111 . 
   As shown in  FIG. 1 , similar to the main control valve described in the first embodiment, the main control valve  115  includes a swing direction switching valve  116  for controlling the feed of hydraulic oil into the circling motor, an arm direction switching valve  117  for controlling the feed of the hydraulic oil into the arm cylinder, a bucket direction switching valve  118  for controlling the feed of the hydraulic oil into the bucket cylinder, and a boom direction switching valve  119  for controlling the feed of the hydraulic oil into the boom cylinder. In addition, the swing direction switching valve  116  and the arm direction switching valve  117  are connected to the downstream of the first pump  112  and the bucket direction switching valve  118  and the boom direction switching valve  119  are connected to the downstream of the second pump  113 . 
   As shown in  FIG. 4 , the driving motor controlling device  2  has the right driving motor  120  and the left driving motor. Furthermore, the driving motor controlling device  2  has a motor control valve  121  corresponding to the right driving motor  120 , an electrical remote controller  122  ( 122   a  and  122   b ), a detector  123 , a control unit  124 , and an electro-hydraulic valve  125  ( 125   a  and  125   b ). In  FIG. 4 , only the motor control valve  121 , the detector  123 , and the electro-hydraulic valve  125  corresponding to the right driving motor  120  are shown. In the following description on the driving motor controlling device  2 , only the right driving motor  120  and the motor control valve  121  thereof will be described, and the left driving motor and the motor control valve thereof will be omitted in order to avoid repetition. 
   Furthermore, a center bypass passage  126  ( 126   a  and  126   b ) in the main control valve  115  is connected to the channels of the left and right driving motors through the swivel joint  111 . In other words, the center bypass passage  126   a  for connecting the bucket direction switching valve  118  to the boom direction switching valve  119  in series is connected to the channel of the left driving motor and the center bypass passage  126   b  for connecting the swing direction switching valve  116  to the arm direction switching valve  117  in series is connected to the channel of the right driving motor  120 . 
   The driving motor  120  of the driving motor controlling device  2  is disposed in the lower body as described above and the motor control valve  121  and the detector  123  are also disposed in the lower body. Meanwhile, the electrical remote controller  122 , the control unit  124 , and the electro-hydraulic valve  125  are disposed in the upper body. In addition, the motor control valve  121  is integrally mounted with the driving motor  120 . Furthermore, the motor control valve  121  is tandem-connected or serial-connected to the control valves  116  and  117  of the hydraulic actuators and connected to the center bypass passage  126   b  at the downstream of the control valves  116  and  117  of the hydraulic actuators. 
   The motor control valve  121  switches a state for connecting the pumps  112  and  113  and the tank  114  to the driving motor  120  such that the driving motor  120  is in any one of a stop state, a normal rotation state (a state that the construction machine rotates forward), and a reverse rotation state (a state that the construction machine rotates backward). The motor control valve  121  has a neutral position  121   a , a normal rotation position  121   b , and a reverse rotation position  121   c , as shown in  FIG. 4 . When the motor control valve  121  is switched to the neutral position  121   a , the driving motor  120  is in the stop state. When the driving motor control valve  121  is switched to the normal rotation position  121   b , the driving motor  120  is in the normal rotation state, and, when the driving motor control valve  121  is switched to the reverse rotation position  121   c , the driving motor  120  is in the reverse rotation state. The motor control valve  121  is switched to any one of the neutral position  121   a , the normal rotation position  121   b , and the reverse rotation position  121   c , based on a command from the electrical remote controller  122  and a pressure of an inflow side of the hydraulic oil into the driving motor  120 , as described below. 
   In addition, a pilot chamber  127  ( 127   a  and  127   b ) on which a pilot pressure for switching and operating the motor control valve  121  acts is provided in the motor control valve  121 . The pilot pressure acts on the pilot chamber  127   a  such that the motor control valve  121  is switched from the neutral position  121   a  to the normal rotation position  121   b , and pilot pressure acts on the pilot chamber  127   b  such that the motor control valve  121  is switched from the neutral position  121   a  to the reverse rotation position  121   c . The pilot pressure which acts on the pilot chamber  127  is generated in the electro-hydraulic valve  125  as described below. 
   The electrical remote controller  122  (hereinafter, referred to as remote controller  122 ) is provided as a control device for converting an amount (for example, the control amount of a control lever) controlled by an operator (not shown) into an electrical signal. The remote controller  122   a  is used for manipulating the motor control valve  121  of the right driving motor  120  and the remote controller  122   b  is used for manipulating the motor control valve of the left driving motor. The remote controllers  122   a  and  122   b  are connected to the control unit  124  such that the electrical signal corresponding to the control amount is input to the control unit  124 . 
   The detector  123  is provided as a pressure sensor mounted in the driving motor  120 . The detector  123  detects the pressure of the inflow side of the hydraulic oil into the driving motor  120  and switches the pressure to an electrical signal. The detector  123  is connected to the control unit  124  through a snap ring  128  disposed in the swivel joint  111 . In addition, similar to the driving motor  120 , a detector (not shown) similar to the detector  123  is also mounted in the left driving motor (not shown). 
   The control unit  124  outputs a control signal of the electro-hydraulic valve  125  for the motor control valve  121  and a control signal of the electro-hydraulic valve for the motor control valve of the left driving motor, based on the electrical signal from the remote controller  122  and the electrical signals from the detector  123  and the detector for the left driving motor. The control unit  124  includes a CPU (central processing unit), a memory (ROM (read only memory)) and RAM (random access memory), and a current control circuit, all of which are not shown. 
   The electro-hydraulic valve  125  generates a pilot pressure which operates the motor control valve  121  based on the control signal from the control unit  124 . In other words, the electro-hydraulic valve  125  is connected to the motor control valve  121  through the swivel joint  111  and magnetized by the energization of a coil portion, based on the control signal from the control unit  124 , such that the pilot hydraulic oil fed from the pilot pump  129  acts on the pilot chamber  127  of the motor control valve  121 . Meanwhile, when the electro-hydraulic valve  125  is demagnetized, an elastic force is applied and the pilot hydraulic oil which acts on the pilot chamber  127  is discharged to the tank  114 . 
   The electro-hydraulic valve  125  includes an electro-hydraulic valve  125   a  for the normal rotation and an electro-hydraulic valve  125   b  for the reverse rotation. For example, when the remote controller  122   a  outputs the electrical signal of a forward drive command (driving command of a normal rotation direction), the electro-hydraulic valve  125   a  is magnetized based on the control signal from the control unit  124 . In addition, when the electro-hydraulic valve  125   a  is magnetized, the pilot hydraulic oil of the pilot pump  129  acts on the pilot chamber  127   a  through a pilot passage  130   a , that is, a pilot pressure is in the pilot chamber  127   a , and thus the motor control valve  121  is switched from the neutral position  121   a  to the normal rotation position  121   b . Meanwhile, when the remote controller  122   a  outputs the electrical signal of a reverse drive command (driving command of a reverse rotation direction), the electro-hydraulic valve  125   b  is magnetized based on the control signal from the control unit  124 , a pilot pressure is in the pilot chamber  127   c , and thus the motor control valve  121  is switched from the neutral position  121   a  to the reverse rotation position  121   c . In addition, similar to the motor control valve  121 , even in the motor control valve of the left driving motor (not shown), an electro-hydraulic valve (not shown) similar to the electro-hydraulic valve  125  for generating the pilot pressure is provided. 
   In addition, the motor control valve  121  of the driving motor controlling device  2  includes a detecting port  131  which is connected to the detector  123  and induces a pressure of the inflow side of the driving motor  120 , which is detected by the detector  123 . The detecting port  131  is communicated with a passage  132  of the inflow side of the driving motor through a continuous passage  133  when the motor control valve  121  is switched to the normal rotation position  121   b  and is communicated to a passage  134  of the inflow side of the driving motor through a continuous passage  135  when the motor control valve  121  is switched to the reverse position  121   c . The detecting port  131  is connected to the passage  132  which becomes the inflow side of the driving motor in the normal rotation state and connected to the passage  134  which becomes the inflow side of the driving motor in the reverse rotation state. 
   Furthermore, in the driving motor controlling device  2 , when the driving motor  120  is in the stop state, a negative brake (not shown) which is operated in order to maintain the stop state is connected to the detecting port  131 . 
   Next, an operation of the driving motor controlling device  2  will be described. The state shown in  FIG. 4  shows a state that the motor control valve  121  is in the neutral position  121   a . In this state, the driving motor  120  is in the stop state. When the construction machine having the driving motor controlling device  2  is operated in an environment in which a temperature is low, such as a cold region in winter, a warming up operation is first performed. Upon the warming up operation, the pumps  112  and  113  are initiated and the hydraulic oil is circulated in a state that the hydraulic oil is not fed into the hydraulic actuators (in a state that the control valves are not operated). 
   At this time, the hydraulic oil discharged from the pumps  112  and  113  becomes warm while being circulated to the tank  114  through the control valves  116 ,  117 ,  118 ,  119 , and  121 . Then, the hydraulic oil is also in a path which reaches the tank  114  disposed in the upper body through the swivel joint  111  and the motor control valve  121 . In other words, upon the warming up operation, the hydraulic oil discharged from the pumps  112  and  113  is circulated to the motor control valve  121  disposed in the lower body in which the driving motor  120  is disposed. Accordingly, the motor control valve  121  becomes warm by the hydraulic oil which becomes warm by circulation, and the driving motor  120  integrally formed with the motor control valve  121  also becomes warm. 
   After the warming up operation, the left and right driving motors are initiated and the construction machine begins to be driven. Here, when the driving motor is switched to the normal rotation state such that the construction machine is moved forward, the right driving motor  120  will be described. In this case, first, the remote controller  122   a  is manipulated by the operator such that the electrical signal of the forward drive command is output, and thus, as described above, the electro-hydraulic valve  125   a  generates the pilot pressure in the pilot chamber  127   a  of the motor control valve  121  based on the control signal from the control unit  124 . Thus, the motor control valve  121  is switched from the neutral position  121   a  to the normal rotation position  121   b  such that the hydraulic oil is fed in a direction in which the driving motor  120  rotates in the normal rotation state and the construction machine begins to be moved forward. 
   Furthermore, in the driving motor controlling device  2 , the pressure of the inflow side of the driving motor  120  is always detected by the detector  123  to be input to the control unit  124  as a detecting signal (electrical signal) and a change in the pressure is also detected by the control unit  124 . Accordingly, when the construction machine begins to be self-propelled on the downhill road and thus the pressure of the inflow side of the driving motor  120  is reduced, the pressure is detected by the control unit  124  and the electro-hydraulic valve  125  is controlled such that the motor control valve  121  returns to the neutral position  121   a  based on the control signal output from the control unit  124 . For example, when the motor control valve  121  is switched to the normal rotation position  121   a  and the pressure is reduced to a value lower than a predetermined threshold due to the self-propulsion of the construction machine, the electro-hydraulic valve  125   a  is demagnetized based on the control signal from the control unit  124  and thus the motor control valve  121  is switched to the neutral position  121   a . Thus, it is possible to suppress creation of cavitation of the driving motor  120  which is generated by the reduction of the pressure of the inflow side of the driving motor due to the self-propulsion of the construction machine from. 
   In the above-described driving motor controlling device  2 , when the warming up operation of the construction machine is performed, the hydraulic oil discharged from the pumps  112  and  113  is circulated to the motor control valve  121  disposed in the lower body in which the driving motor  120  is disposed. Accordingly, the motor control valve  121  becomes warm by the hydraulic oil which becomes warm by circulation, and the driving motor  120  integrally formed with the motor control valve  121  also becomes warm. Thus, according to the driving motor controlling device  2 , the heat balance of the driving motor  120  is prevent from being lost when the construction machine begins to be driven after the warming up operation, and thus the operation fault or failure of the driving motor  120  due to the difference in the thermal expansion in the driving motor  120  can be suppressed. 
   In addition, when the construction machine is switched from the driving state to the stop state on the downhill road, the outflow side of hydraulic oil from the driving motor  120  has a high pressure. Accordingly, the existing driving motor controlling device of the construction machine need use a pipe which has a high strength to bear up against the high pressure between the motor control valve and the driving motor. Thus, an expensive pipe is required. However, according to the driving motor controlling device  2 , since the motor control valve  121  is integrally formed with the driving motor  120 , a pipe for connecting the motor control valve  121  to the driving motor  120  is not required. 
   Furthermore, according to the driving motor controlling device  2 , the electro-hydraulic valve  125  is controlled to generate the pilot pressure based on a command from the electrical remote controller  122  by the control unit  124  and the result of detecting the pressure of the inflow side of the driving motor  120  by the detector  123 . Thus, the motor control valve  121  can be operated by the pilot pressure. Accordingly, response delay is low and the motor control valve  121  can be accurately or rapidly operated based on the pressure of the inflow side of the driving motor  120  and the command from the electrical remote controller  122  which is the control device. 
   Furthermore, according to the driving motor controlling device  2 , since the detector  123  for detecting the pressure of the inflow side of the driving motor  120  is mounted in the driving motor  121 , detection of the pressure can be more suppressed from being delayed, compared with a case where the pipe is provided from the inflow side of the driving motor  120  to the upper body through the swivel joint  111  to be connected to the detector  123 . In addition, a response to the change in the pressure of the inflow side of the driving motor  120  is suppressed from being delayed and thus the motor control valve  121  can be rapidly operated with respect to the change in the pressure of the inflow side of the driving motor  120 , thereby suppressing cavitation from being created in the driving motor  120 . In addition, the response to the change in the pressure of the inflow side of the driving motor  120  is suppressed from being delayed and thus hunting can be suppressed from being generated in the operation of the motor control valve  121 . 
   According to the driving motor controlling device  2 , when the motor control valve  121  is in the normal rotation position  121   b , the passage  132  and the detecting port  131  are communicated with each other through the continuous passage  133 , and, when the motor control valve  121  is in the reverse rotation position  121   c , the passage  134  and the detecting port  131  are communicated with each other through the continuous passage  135 . Accordingly, the pressure of the inflow side of the driving motor  120  which is induced to the detector  123  is selected by the motor control valve  121  and thus the passage  132  which becomes the inflow side in the normal rotation position and the passage  134  which becomes the inflow side in the reverse rotation position need not have the respective detectors, thereby sharing the detector. 
   In addition, according to the driving motor controlling device  2 , by combining a port for the negative brake and a port for the detecting port  131 , the number of the ports may not increase in mounting the detector  123 , thereby preventing the device from being enlarged. 
   Although the invention has been described in connection with the first and second embodiments of the invention illustrated in the accompanying drawings, it is not limited thereto. It will be apparent to those skilled in the art that various substitutions, modifications and changes may be made thereto without departing from the scope and spirit of the invention. 
   INDUSTRIAL AVAILABILITY 
   A driving motor controlling device of a construction machine according to the invention can widely apply to a driving motor controlling device including a driving motor connected to a pump and a tank through a swivel joint and a motor control valve for switching a state for connecting the pump and the tank to the driving motor such that the driving motor is controlled to any one of a stop state, a normal rotation state, and a reverse rotation state.