JP2007249583A - Pressure-reducing valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure reducing valve suitable for an hydraulic pressure control device of a load sensing system equipped with hunting suppression function. <P>SOLUTION: Inside a main part of the valve 12, first and second through-holes 14, 16 are formed, and a spool 18 is accommodated in the second through-hole being possible to slide. In the spool, a first land 20, a second smaller in diameter part 22, a second land 24, a first smaller in diameter part 26 and a third land 28 are formed, and the outside diameter D2 of the first and the second land are formed larger than the outer diameter D1 of the third land. The primary-side LSIN of a pressure reducing valve 10 is supplied to the second smaller in the radial part and the third land edge face side. Moreover, a secondary-side LSOUT is connected to the first through-hole. Thus, due to the difference in the pressure receiving area of the right and the left edge face of the spool, the second small-diameter part chamber V2 and the first through-hole repeats communication and blocking in rapid succession, and the pressure in the secondary side is consequently reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pressure reducing valve, and particularly in a hydraulically operated construction machine, preferably a pressure reducing pressure that is combined with a plurality of control valves constituting a load sensing type hydraulic control device to provide a hunting suppression function to the hydraulic control device. Regarding the valve.

  A flow rate control method called load sensing detects the maximum load pressure of multiple actuators in a hydraulic control device that controls multiple actuators with a single pump so that the discharge pressure of the pump becomes a constant higher pressure than the detected pressure. This is a control method. The difference in load pressure with respect to the pump pressure is usually called load sensing differential pressure. When multiple actuators are operated, the pump discharge pressure is controlled to a pressure higher than the maximum load pressure of the multiple actuators. In recent years, it has been attracting attention as an energy saving control method by supplying only oil.

  FIG. 5 shows a general configuration of a hydraulic circuit of a hydraulic control device for a construction machine using such a load sensing function. In FIG. 5, reference numeral 100 indicates an engine that drives the variable displacement pump 102, and a discharge line L of the pump 102 is connected to pressure compensating valves 104 and 110 that constitute a control valve unit CVLU. Control valves 106 and 112, which are spool valve type directional switching valves, are arranged downstream of these pressure compensation valves 104 and 110. Further, cylinders 108 and 114 which are hydraulic actuators are provided on these control valves 106 and 112, respectively. Each is connected. Reference numeral 116 denotes a shuttle valve. When each control valve 106, 112 is in an operating state, the larger load pressure of load pressure detection lines L1, L2 indicated by broken lines is used for load sensing (hereinafter referred to as LS). This is given to the line LSL. The control unit CTU including the variable displacement pump 102 is provided with a valve 120 for adjusting the pump discharge flow rate, and a load sensing line LSL is connected to the left port. The spring 122 is provided for setting a differential pressure that always applies a predetermined pressure to the target load sensing pressure. Reference numeral 118 is a cylinder for adjusting the swash plate angle of the variable displacement pump 102 and is connected to the valve 120. In the hydraulic circuit shown in FIG. 5, the pressure compensation valves 104 and 110 are arranged on the upstream side of the control valves 106 and 112, respectively, but between the control valves 106 and 112 and the actuators 108 and 114, respectively. In some cases, a load sensing line LSL is formed from the load pressure detection lines L1 and L2 via the shuttle valve 116. ing.

  On the other hand, in order to improve the relationship between the pressure compensation valve and the load sensing LS, the load sensing control is performed so that the discharge pressure of the hydraulic pump is higher than the maximum load pressure of the plurality of actuators by the target differential pressure, and the plurality of direction switching valves. In a hydraulic drive device such as a hydraulic excavator that controls the differential pressure before and after the pressure compensation valve, the target compensation differential pressure of each pressure compensation valve is the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure of multiple actuators. And a hydraulic drive device in which a target differential pressure for load sensing control is set as a variable value depending on the engine speed has been proposed (Patent Document 1).

  In FIG. 1 of Patent Document 1, the secondary pressure from the differential pressure reducing valve and the target differential pressure of the load sensing control are respectively derived as the embodiment of the hydraulic drive device, and one of these is lower. The low pressure selection valve that outputs the pressure of the other is provided, the output pressure of the low pressure selection valve is guided to all the pressure compensation valves, and the output pressure is set as the target compensation differential pressure of each of the plurality of pressure compensation valves. A circuit configuration that makes it easy to operate the construction machine, with no difference in pressure difference before and after the direction switching valve between the fine operation and the flow rate exceeding a certain level on a construction machine such as an excavator. A hydraulic drive having the same is disclosed. Further, as shown in FIG. 1 of Patent Document 1, one differential pressure reducing valve is arranged for a plurality of directional control valves, and the outlet side of the differential pressure reducing valve is connected to a load sensing line (PC secondary). Pressure) and supplied to the pump tilt angle control valve.

  On the other hand, in a flow control system having a load sensing function used in combination with a variable displacement pump, hunting is likely to occur when a load having a large inertia is used as a load.

  In addition, in such a flow rate control system, since the flow rate is controlled by feedback control of the load pressure, once hunting occurs, it cannot be easily suppressed. As a method for preventing such hunting and demonstrating the load sensing function, there is a method of increasing the amount of hydraulic oil constantly supplied from the hydraulic pump to constantly bleed off from the maximum load pressure signal. However, in this method, it is necessary to select a very large bleed orifice in order to effectively control a load that is likely to cause hunting, and an excessive flow rate is always consumed by bleed-off. This is an inefficient flow control system.

  Therefore, as a hydraulic control device used in a multiple flow control system having a load sensing function, which is small and can save energy by changing flow characteristics, a variable capacity A load sensing function that detects the maximum load pressure among the load pressures of a plurality of actuators driven by a pump and controls the discharge pressure of the variable displacement pump so that it is higher than the detected maximum load pressure by a predetermined value In a hydraulic control device having a maximum load pressure port to which a maximum load pressure in the system is supplied, through a pump port and a variable orifice of the variable displacement pump, A first flow path communicating with the actuator is connected to the input port, and a second flow path communicating with the actuator is connected to the output port. A compensator having a throttle whose opening amount changes in order to control the pressure of the first flow path in accordance with the pressure in the flow path, a pressure chamber for applying a force in the direction of closing the throttle, the variable orifice, It operates independently of the compensator, and when the pressure in the second flow path is higher than the maximum load pressure of other stations in the system, the pressure in the first flow path is reduced to the pressure in the second flow path. A switching valve for reducing pressure and supplying the reduced pressure to the maximum load pressure port. The switching valve is built in the compensator, and the switching valve is connected to the pressure of the maximum load pressure port and the second flow rate. Slides according to the deviation from the pressure of the passage, and the slide guides the pressure of the first flow path to the highest load pressure port to obtain the highest load pressure. Disclosed is a hydraulic control device that has a function of guiding the pressure of a flow path to a pressure chamber of a compensator to close the throttle, and providing an intermediate throttle in the flow path from the switching valve to the highest load pressure port. (Patent Document 2).

  In Patent Document 2, as shown in FIGS. 3, 7, 9, and 10, a pressure reducing function is provided. In paragraph 0104, “the switching valve 103 to the PLS port” The hydraulic oil flowing to the PLS port 180 is further reduced as the load pressure is increased by the intermediate throttle 145 provided in the flow path connected to the flow path 180. Accordingly, if the load pressure increases, the solid line in FIG. As shown in Fig. 9, it is possible to provide a flow rate characteristic in which the flow rate to the load decreases as the load pressure increases. . "

JP 2002-323004 “Hydraulic drive device” JP-A-2005-140253 “Hydraulic Control Device”

  However, in the above-mentioned Patent Document 1, it is not considered as a problem to suppress the occurrence of hunting in a load sensing type hydraulic control device. Further, the structure of the differential pressure reducing valve itself is not particularly shown.

  Moreover, in the said patent document 2, the intermediate | middle restrictor which gives a pressure reduction function inside each direction switching valve is formed, and it is an intermediate | middle to each direction switching valve which is a some control valve of the said hydraulic control apparatus. A diaphragm is provided. Therefore, although it is possible to use a hydraulic control valve in an existing working construction machine as it is and to have a pressure reducing function, it is actually possible to remodel each control valve in practice. It is necessary and practically difficult.

  In addition to the description in Patent Document 2, when the conventional load sensing control method is adopted, it is possible to supply pressure oil regardless of the load pressure, but there is an actuator or inertia having a high load pressure. When a large actuator or load pressure fluctuates, if the pressure higher than a certain load pressure is continuously supplied to the load, the actuator vibrates (hunts), and the aircraft itself and further the construction machine The pilot vibrates with the airframe, thereby moving the operation lever and amplifying the vibration. Further, the pilot feels uncomfortable due to the vibration.

  As a result of various studies and studies to solve the above problems, the present inventor has obtained a single pressure reducing valve having a separate structure from the hydraulic control valve hydraulically connected to the hydraulic actuator of the construction machine. It has been found that the problem of the occurrence of hunting can be basically solved by arranging it on the load sensing line.

  Therefore, the object of the present invention is preferably that in an oil pressure control apparatus adopting a load sensing system, the actuator does not cause hunting. An object of the present invention is to provide a pressure reducing valve used in a load sensing type hydraulic control device that makes it possible to obtain good operability.

  In order to achieve the above object, a pressure-reducing valve according to the present invention, preferably used in a load-sensing hydraulic control device, has a first through hole and an opening formed at one end of the first through hole. A valve body having a second through hole, a primary port provided in the valve body and communicating with the second through hole, a secondary port communicating with the first through hole, and the second A spool that is slidable in the through hole, has one end facing the first through hole and the other end facing the second through hole, and is provided on the valve body. A plug that seals one end of each of the first and second through holes from the outside of the valve body, and the second through hole has a second zone whose one side is adjacent to the first through hole. And the first zone adjacent to the other side of the second zone and the inner diameter of the second zone A first land and a second land having the same diameter are formed on the outer periphery of the spool that is formed to be larger than the inner diameter of the first zone, and slidably contact the inner diameter portion corresponding to the second zone of the spool. A second small-diameter chamber is formed between the second lands, and a third land is formed on the outer periphery of the spool that is in sliding contact with the inner diameter corresponding to the second zone. A first small-diameter chamber is formed between the second land, and the primary port is provided at the second through-hole end facing the second small-diameter chamber and the other end of the spool. It is connected, The said 1st small diameter part chamber is connected to the drain, It is characterized by the above-mentioned.

  In that case, the first through hole and the second through hole formed on one end side of the first through hole are formed adjacent to each other through a step portion, and the inner diameter of the first through hole is the second It is preferable that the first through-hole is formed larger than the inner diameter of the through-hole, and a spring receiver is provided in the first through-hole, and the spool is biased to an initial setting position by a spring attached to the spring receiver.

  In this case, the primary side port communicates with the second small diameter portion and the end of the second through-hole facing the other end of the spool by providing a branch passage in the valve body. It may be configured.

  In order to achieve the above object, a load sensing type hydraulic control apparatus according to the present invention includes a plurality of hydraulic control valves connected to supply and discharge pressure oil to and from a plurality of hydraulic actuators. In a hydraulic control device that detects the actuator load and feeds back the maximum load pressure to the flow rate adjustment mechanism of the variable displacement pump via the load sensing line, the load sensing line receives the load sensing pressure as the primary pressure. The secondary pressure is proportional to the primary pressure and a single pressure reducing valve that gradually decreases is connected to suppress hunting of the hydraulic actuator.

  In this case, the pressure reducing valve includes a valve body having a first through hole and a second through hole formed at one end of the first through hole therein, and the second main body provided in the valve body. A first side port communicating with the first through hole, a second side port communicating with the first through hole, and a first side hole slidable within the second through hole. The other end side is sealed from the outside of the valve body, and the spool arranged to face the second through hole and the respective one end portions of the first and second through holes provided in the valve body. And the second through-hole comprises a second zone having one side adjacent to the first through-hole and a first zone adjacent to the other side of the second zone. The inner diameter is larger than the inner diameter of the first zone and corresponds to the second zone of the spool A first land and a second land having the same diameter are formed on the outer periphery in sliding contact with the inner diameter portion, and a second small-diameter chamber is formed between the first land and the second land. A third land is formed on the outer periphery of the spool that is in sliding contact with an inner diameter portion corresponding to one zone, and a first small-diameter chamber is formed between the third land and the second land, The primary side port communicates with the second small diameter portion and the end of the second through hole facing the other end of the spool, and the first small diameter chamber is connected to the drain. be able to.

  In this case, the first through hole and the second through hole formed on one end side of the first through hole are formed adjacent to each other through a step portion, and the inner diameter of the first through hole is the second. Preferably, the first through hole is provided with a spring receiver, and a spring attached to the spring receiver is used to urge the spool to the initial setting position.

  According to the pressure reducing valve according to the first aspect of the present invention, the pressure decreasing rate of the pressure reducing valve can be arbitrarily set by setting the outer peripheral diameters of the first land and the third land to an appropriate ratio.

  According to the hydraulic control device of the present invention as set forth in claim 4, the occurrence of hunting of the hydraulic actuator can be suppressed by arranging a single pressure reducing valve on the load sensing line.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a longitudinal section in the spool axial direction of a pressure reducing valve 10 according to the present invention. In FIG. 1, a first through hole 14 is formed in the center of the valve body 12 from the left side, and a second through hole 16 adjacent to the right side of the through hole 14 is formed through a step portion 14A. Has been. A spool 18 is slidably accommodated in the through hole 16. The second through hole 16 is divided into a zone ZN2 and a right zone ZN1 adjacent to the zone ZN2 from the left in the drawing. The inner diameter of the through-hole 16 in the zone ZN2 is formed at D2, while the inner diameter of the zone ZN1 is D1, where the inner diameter D2 is formed to be slightly larger than D1. The inner diameter D1 of the zone ZN1 corresponds to the inner diameter of the sleeve 30 inserted and fixed in the recess 30 formed in the valve body 12. The left end of the through hole 14 and the right end of the through hole 16 are sealed by screwed plugs 32 and 36 and o-rings 34 and 38, respectively.

  A first land 20, a second small diameter portion 22, and a second land 24 are formed on the outer peripheral portion of the spool 18 corresponding to the zone ZN 2 from the left, and the outer periphery of the first land 20 and the second land 24. The diameters are equal (D1). Pressure oil of the primary side LSIN of the pressure reducing valve 10 is given to the second diameter small portion chamber V2 surrounded by the inner peripheral surface of the second diameter small portion 22 and the through hole 16 and the right and left land side surfaces thereof. On the other hand, a first small diameter portion 26 is formed between the second land 24 and the third land 28 on the outer peripheral portion of the spool 18, and the first small diameter portion 26 and the through hole 16, that is, the sleeve 32. The first small-diameter chamber V1 surrounded by the inner peripheral surface and the left and right land side surfaces thereof is connected to the drain DR.

  Further, the right end portion of the spool 18 faces the right end portion of the second through hole 16, and the pressure oil of the primary side LSIN of the pressure reducing valve 10 is given to the right end portion of the through hole 16 through the communication channel 40. ing.

  A small-diameter shaft portion 18A is formed on the left end side of the first land 20 of the spool 18 through a step portion, and a spring receiver 44 is fitted therein to support the right end portion of the spring 46. Reference numeral 42 is a guide member of the spring 46 and is attached to the right end of the plug 32. The spring 46 acts so that the initial position of the spool 18, that is, the right end surface of the spool 18 contacts the stopper 36. The pressure in the through hole 14 constitutes the pressure of the secondary side LSOUT of the pressure reducing valve 10, and a flow path SCL for taking out the pressure is formed in the valve body 12. In the drawing, the pressure oil of the primary side LSIN of the pressure reducing valve 10 branches outside the valve body 12 and is given to the second small diameter chamber and the communication flow path 40, respectively. 12 may be formed inside.

  Reference numerals 50 and 52 are screw holes for attaching the valve body 12 to other members.

  2 indicates the configuration of the equivalent hydraulic circuit of the pressure reducing valve 10 shown in FIG.

  FIG. 3 is a graph showing the relationship between the primary side LSIN and the secondary side LSOUT of the pressure reducing valve 10 and the change in the characteristics of the pressure reducing valve 10 according to the parameter α.

  FIG. 4 is a graph showing actual measurement data of the characteristic change of the pressure reducing valve 10.

  Next, the operation of the pressure reducing valve 10 will be described mainly with reference to FIG.

When pressure oil is not supplied to the primary side LSIN of the pressure reducing valve 10, the spool 18 is held at the right end position, which is the initial position, by urging the spring 46 to the right as described above. Here, when pressure oil is supplied to the primary side LSIN, the pressure oil is transmitted to the right end portion of the first through hole 16 via the communication flow path 40, and therefore the spool 18 has its right end surface (the outer diameter is D1). receiving area i.e., moved leftward by a hydraulic fluid acting on ^{A1 (= πD1 2/4)} .

As the spool 18 moves, the oil in the first small diameter chamber V1 is gradually discharged to the drain DR. On the other hand, the pressure oil in the second small-diameter chamber V2 connected to the primary side LSIN is moved while remaining in the same chamber V2. When the left end of the first land 20 passes the stepped portion 14A and the right end of the first land 20 passes the stepped portion 14A due to the leftward movement of the spool 18, the pressure oil in the second small diameter chamber V2 passes through the through hole 14. the pressure in the through-hole 14 is increased communication with, the first land pressure receiving area of the left end surface of the (an outer diameter D2) that, A2 in (= πD2 ^2/4) second radial resulting spool 18 The pressure oil pressure in the small chamber V2 acts. Since the outer diameter D2 is formed to be larger than D1, the spool 18 is pushed back by the acting force from the left end side pressure receiving surface, which exceeds the acting force from the right end side pressure receiving surface, and moves to the right. As a result, when the right end of the first land again passes the step 14A and returns to the right, the communication between the second small diameter chamber V2 and the through hole 14 is blocked. Then, the acting force of the pressure oil acting on the right end surface of the spool 18 becomes dominant, and the spool 18 is moved to the left again. Hereinafter, such a process is repeated at a minute time interval, and the pressure in the first through hole 14, that is, the pressure on the secondary side of the pressure reducing valve 10 is, on average, compared with the pressure on the primary side. The pressure reduction value substantially corresponds to the ratio of the pressure receiving areas A1 and A2. F1 indicated by a broken line in FIG. 2 indicates an acting force acting on the right end surface of the spool 18, and F2 indicates an acting force acting on the left end surface of the spool 18.

  The equation in FIG. 3 shows a relational expression between the secondary pressure PLSOUT of the pressure reducing valve 10 and the primary pressure PRISIN, where k is a spring constant of the spring 46, x1 is an initial displacement amount of the spring 46, x represents the displacement amount of the spool 18. Since the second term k (x1 + x) / A2 in the equation is very small compared to the first term, the secondary pressure PLSOUT of the pressure reducing valve 10 is substantially equal to the primary pressure PLSIN and α (= A1). / A2). That is, the secondary side pressure PLSOUT of the pressure reducing valve 10 is a value obtained by multiplying the primary side pressure PLSIN by the pressure receiving area ratio.

  FIG. 4 shows the situation of pressure reduction when the outer diameter D2 of the first and second lands is 10 mm and the outer diameter D1 of the third land is 9.85 mm and 9.70 mm, respectively. In FIG. 4, for example, when D1 is 9.70 mm, a pressure reducing effect of about 2 MPa can be obtained when the primary pressure PRISN is 30 MPa. In FIG. 4, reference numeral RF indicates a state in which D1 is 10 mm, that is, D1 = D2, and there is almost no pressure reducing effect.

  Supply pressure to the valve 120 for adjusting the pump discharge flow rate that constitutes the discharge flow rate adjustment mechanism of the variable displacement pump 102 by disposing such a pressure reducing valve 10 on the load sensing line LSL of FIG. Can be provided under reduced pressure.

  As is clear from the above description, in the pressure reducing mechanism of the pressure reducing valve 10, the spring 46 has no essential function other than the role of setting the initial position of the spool 18. Thus, for example, it is possible not to use a spring. In that case, in order to set the initial position of the spool 18, for example, permanent magnets of the same polarity are embedded in the right end of the guide member 42 in FIG. It is also possible to set the initial position of the spool 18. In this case, the inner diameter of the first through hole is such that when the right end of the first land 20 reaches the stepped portion 14A due to the left line of the spool 18, the communication between the second small diameter chamber V2 and the through hole 16 is immediately established. It is sufficient that the opening is made to the extent that it can be performed, and it is not always necessary to have an inner diameter for accommodating the spring 46.

  The preferred embodiments of the present invention have been described above with reference to the drawings. However, those skilled in the art can make various modifications based on the technical ideas disclosed by the present invention using the above-described embodiments and drawings. It is. However, such various modifications are within the scope of the present invention.

The spool axial direction longitudinal cross-section of the pressure-reduction valve by this invention is shown. It is a figure which shows the equivalent hydraulic circuit of the pressure reducing valve of FIG. It is a graph explaining the theoretical characteristic of pressure reduction of the pressure reducing valve according to the present invention. It is a graph which shows the pressure-reduction characteristic measured actually of the pressure-reduction valve by this invention. It is a figure which shows the general hydraulic circuit structure of the hydraulic control apparatus provided with the load sensing function.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pressure reducing valve 12 Valve main body 14 1st through-hole 14A Step part 16 2nd through-hole 18 Spool 18A Diameter small shaft part 20 First land 22 Second diameter small part 24 Second land 26 First diameter small part 28 First 3 land 30 sleeve 32 plug 34 o-ring 36 plug 38 o-ring 40 communication passage 42 guide member 44 spring receiver 46 spring 50, 52 screw hole 100 engine 102 variable displacement pump 104, 110 pressure compensation valve 106, 112 control valve 108, 114 Actuator 116 Shuttle valve 118 Cylinder 120 Pump discharge amount adjustment valve 122 Target load sensing differential pressure setting spring A1, A2 Pressure receiving area CTU Control unit CVLU Control valve unit D1 Outer diameter D2 of third land D2 Outer diameter DRN of first and second land Drain L1, L2 Load detection line LSL Load sensing line L IN primary port LSOUT secondary port V1 first small diameter chamber V2 second small diameter chamber

Claims (6)

A valve body having a first through hole therein and a second through hole formed at one end of the first through hole;
A primary side port provided in the valve main body and communicating with the second through hole, and a secondary side port communicating with the first through hole;
A spool that is slidable in the second through-hole and has one end facing the first through-hole and the other end facing the second through-hole,
A stopper that seals one end of each of the first and second through holes provided in the valve body from the outside of the valve body, and
The second through hole includes a second zone adjacent to the first through hole on one side and a first zone adjacent to the other side of the second zone. The inner diameter of the second zone is the inner diameter of the first zone. Formed larger,
A first land and a second land having the same diameter are formed on the outer periphery of the spool in sliding contact with the inner diameter portion corresponding to the second zone, and a second small diameter portion is formed between the first land and the second land. Further, a third land is formed on the outer periphery of the spool that is in sliding contact with the inner diameter portion corresponding to the first zone, and a small first diameter is formed between the third land and the second land. Part is formed, and
The primary side port communicates with the second small diameter portion and the end of the second through hole facing the other end of the spool, and the first small diameter portion is connected to the drain. Characteristic pressure reducing valve.   The first through hole and the second through hole formed on one end side of the first through hole are formed adjacent to each other through a step portion, and the inner diameter of the first through hole is that of the second through hole. 2. The pressure reducing valve according to claim 1, wherein the pressure reducing valve is formed to be larger than an inner diameter, and a spring receiver is provided in the first through-hole, and the spool is biased to an initial setting position by a spring attached to the spring receiver.   The primary side port communicates with the second small diameter portion and the end of the second through hole facing the other end of the spool by communicating with a branch passage in the valve body. The pressure reducing valve according to claim 1 or 2.   Equipped with multiple hydraulic control valves connected to supply and discharge pressure oil to and from multiple hydraulic actuators, detects the load of each hydraulic actuator and adjusts the flow rate of the variable displacement pump via the load sensing line In the hydraulic control apparatus that feeds back to the mechanism, the load sensing line is connected to a single pressure reducing valve that accepts the load sensing pressure as the primary pressure and the secondary pressure is proportional to the primary pressure and decreases. A hydraulic control device characterized in that hunting of the hydraulic actuator is suppressed. The pressure reducing valve has a valve body having a first through hole and a second through hole formed on one end side of the first through hole inside;
A primary side port provided in the valve main body and communicating with the second through hole, and a secondary side port communicating with the first through hole;
A spool that is slidable in the second through-hole and has one end facing the first through-hole and the other end facing the second through-hole,
A plug that seals one end of each of the first and second through holes provided in the valve body from the outside of the valve body, and
The second through hole includes a second zone adjacent to the first through hole on one side and a first zone adjacent to the other side of the second zone. The inner diameter of the second zone is the inner diameter of the first zone. Formed larger,
A first land and a second land having the same diameter are formed on the outer periphery of the spool in sliding contact with the inner diameter portion corresponding to the second zone, and a second small diameter portion is formed between the first land and the second land. Further, a third land is formed on the outer periphery of the spool that is in sliding contact with the inner diameter portion corresponding to the first zone, and a small first diameter is formed between the third land and the second land. Part is formed, and
The primary side port communicates with the second small diameter portion and the end of the second through hole facing the other end of the spool, and the first small diameter portion is connected to the drain. The hydraulic control apparatus according to claim 4, wherein the hydraulic control apparatus is characterized in that:   The first through hole and the second through hole formed on one end side of the first through hole are formed adjacent to each other through a step portion, and the inner diameter of the first through hole is that of the second through hole. 6. The hydraulic control device according to claim 5, wherein the hydraulic control device is formed larger than an inner diameter, and a spring receiver is provided in the first through hole, and the spool is biased to an initial setting position by a spring attached to the spring receiver.

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