JPH0348389B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a flow control valve for controlling the flow rate of hydraulic fluid supplied to a hydraulic cylinder in a hydraulic circuit of a die-casting machine or the like. [Prior art] Injection molding equipment such as die casting machines and plastic injection molding machines is equipped with an injection cylinder that injects molten metal or resin into a mold cavity.
A flow control valve that adjusts the flow rate of hydraulic oil to control the injection speed is provided in the hydraulic circuit of the injection cylinder. FIG. 3 shows a schematic structure of a conventional flow control valve of this type. This will be explained based on the figure. The pulse motor 3 attached to the casing 2 of the flow control valve 1 has a A screw shaft 4a of a ball screw 4 rotatably supported therein is connected by a coupling 5, and a nut 4c that is threadedly engaged with the screw shaft 4a via a ball 4b of the ball screw 4 is connected to a nut 4c via a connection shaft 4d. A spool 6 is integrally formed. The spool 6 is supported in a valve body 7 connected to the casing 2 so as to be able to move forward and backward in the axial direction, and the valve body 7 has a hydraulic oil inlet 7a and a hydraulic oil outlet 7b. Also,
The spool 6 is provided with a plurality of communication holes 6a that communicate with the front chamber 7c and the rear chamber 7d of the valve body 7, and the valve body 7 is further provided with a pair of communication holes 6a that are formed in an annular shape and communicate with the outlet 7b. Groove 7e,
7f are provided in parallel in the axial direction, and the communication hole 6a of the spool 6 is provided with a groove 6b that allows communication between the communication hole 6a and the communication groove 7f as the spool 6 moves. 8 is casing 2
9 is a permanent magnet provided on the outer periphery of the nut 4c, and 10 is a key for regulating rotation of the nut 4c. To explain the operation of the flow rate control valve configured as above, taking as an example the flow rate control of injection cylinder hydraulic oil in a die-casting machine, before the start of injection of the die-casting machine, the nut 4c is screwed up from the position shown in the figure. It has come out of the shaft 4a and the spool 6 has moved forward to the left from the position shown in the diagram.
The spool 6 closes the communication grooves 7e and 7f.
When a command to start injection is issued from this state and the pulse motor 3 rotates by a predetermined angle, the screw shaft 4a connected by the coupling spring 5 rotates, and the nut 4c and the integral spool 6 screwed together rotate. Move back to the right. Therefore, the front chamber 7a communicates with the communication groove 7e, and the groove 6b communicates with the communication groove 7f, and the hydraulic oil from the inlet 7a is supplied to the injection cylinder from the outlet 7b. At the initial stage of injection,
The opening degree of the communication grooves 7e and 7f is small, the flow rate of the hydraulic oil is small, and the injection speed is low. However, when the injection is read and a command for high-speed injection is sent to the pulse motor 3 after a predetermined time, the pulse motor 3 starts. When the spool 6 rotates again, the spool 6 further retreats and the opening degree of the communication grooves 7e and 7f increases, thereby increasing the flow rate of the hydraulic oil and increasing the injection speed. In such a flow rate control operation, the hydraulic pressure in the front chamber 7c and the hydraulic pressure in the rear chamber 7d change due to changes in the opening degree (valve opening degree) of the communication grooves 7e and 7f depending on the movement position of the spool 6. Due to the pressure difference, spool 6
The compressive stress (stress in the valve opening direction) acting on the connecting shaft 4d between the and the nut 4c changes, and depending on the valve opening position, the tensile stress (stress in the valve closing direction) changes. ) was in effect. A diagram showing the relationship between the valve opening degree and compression and tensile stress caused by the movement of the spool 6 is shown in FIG. 4, and the horizontal axis represents the communication hole 7 indicated by the symbol S in FIG.
Take the valve opening degree (mm) of e, 7f, and connect the connecting shaft 4 on the vertical axis.
d (spool 6) in the axial direction. Note that this stress is tensile stress (stress in the valve closing direction) + σ above the 0 point, and compressive stress (stress in the valve opening direction) - σ below the 0 point, and the further away from the 0 point, the more This indicates that the absolute value is large. In the figure, when the valve opening degree is 0, the compressive stress -σ is the largest and equal to the hydraulic oil supply pressure P ₀ . From this state, spool 6
When it retreats and the communication grooves 7e and 7f begin to open, the arrow A in the figure moves from the front chamber 7c to the communication grooves 7e and 7f.
As shown in Fig. 4, the hydraulic oil flows in a constricted manner, and the flow speed increases at this constricted portion, so the pressure of the hydraulic oil decreases and the spool 6 is pulled toward the front chamber 7c. As shown in the figure, as the valve opening degree S gradually increases, the compressive stress -σ decreases. In addition, when the fully open state of the valve opening S is set to 10 to 12 mm, for example, when the valve opening reaches about 5 mm, the compressive stress -σ becomes minimum, and after this, the valve opening S
As the pressure increases, the compressive stress -σ increases again until the cylinder is fully opened, and the entire cylinder has a characteristic that the cylinder has a substantially chevron-shaped configuration. When compressive stress -σ is the minimum in such a valve opening degree-stress characteristic, this may turn into tensile stress +σ as shown in the figure. This phenomenon is caused by the shape of the spool 6, especially the shape of the constricted portion formed by the edge of the front chamber side end of the spool 6 that opens and closes the communication grooves 7e and 7f on the valve body 7 side, and the edge of the groove 6b. Although it changes somewhat, the tendency is almost the same regardless of the shape. In other words, shapes for forming such a constricted portion include a simple corner-shaped spool edge, as well as a chamfered portion, a notch portion, a curved groove, etc. formed on the edge portion as appropriate. However, in all cases, although there were some differences in the magnitude of the stress width, they had almost the same characteristics. By the way, in the flow rate control valve 1 as described above, the stress width described above is a value indicated by the symbol P in _FIG . Therefore, the pulse motor 3 that drives the spool 6, which is subject to such stress, via the connecting shaft 4d and the ball screw 4 must have a capacity commensurate with this, which reduces equipment costs and The disadvantage was that power costs increased. That is, the capacity required for the motor 3 is required to have a driving force sufficient to maintain the spool 6 at a predetermined position against the maximum stress P ₀ as described above. In particular, in order to satisfy these conditions, the pulse motor 3 is actually required to have a capacity close to about 10 times the force required to resist the maximum stress (P ₀ ) mentioned above. It was hot. This is because torque is required to accelerate the pulse motor 3 at startup, and even when the rotational speed increases and the generated torque becomes constant,
It was necessary to secure a force sufficient to withstand the maximum stress mentioned above. Therefore, it is desired to take some measures that can reduce as much as possible the supporting torque required to obtain an acting force that opposes the maximum stress that affects the capacity of the motor 3. Further, when such a flow control valve 1 is incorporated into a hydraulic circuit connected to a hydraulic cylinder in a die-casting machine as described above, there are the following problems that are desired to be solved. That is, when the valve spool moves in the opening direction and stops at the valve opening position for high-speed injection when transitioning from low-speed injection to high-speed injection, a tensile stress +σ is normally applied to the connecting shaft 4d.
However, in the conventional equipment as mentioned above, the tensile stress +
When σ is small, the force acting as a brake when stopping the valve spool that is moving to open is small, and the disadvantage is that the time from when the valve spool starts to open until it stops at the desired high-speed opening position is slightly longer. It was hot. This is the case when it is necessary to switch from low-speed injection to high-speed injection in an extremely short period of several hundredths of a second, such as in a die-casting machine, or when it is necessary to suppress vibrations as quickly as possible when switching to high-speed injection. However, it is desirable to be able to solve these problems as well. [Summary of the Invention] The present invention has been made in view of the above points, and includes a valve spool for opening and closing a fluid passage that is driven by a motor through a screw mechanism and moves back and forth within a housing.
The connecting shaft on the screw mechanism side and the end shaft on the fluid inlet side are pivotally supported in the housing, and the diameter d of the end shaft is determined by the stress width P generated in the axial direction on the connecting shaft when the valve spool is operated and the hydraulic oil. By satisfying a certain relationship based on the supply pressure _P0 and forming the connecting shaft smaller than the diameter D, it is possible to make the maximum tensile stress and the maximum compressive stress acting on the connecting shaft almost equal. As a result, the present invention provides a flow control valve which is capable of reducing the capacity of the motor, thereby reducing equipment costs and power costs, and improving operability when opening the valve. [Example] This example shows an example in which a flow control valve according to the present invention is implemented in a die-casting machine, and FIG. 1 is a longitudinal sectional view thereof. In the figure, a flow control valve, generally designated by reference numeral 11, is disposed between the injection cylinder of the die-casting machine and an accumulator that stores its hydraulic oil.
2 is a valve body 13 formed into a cylindrical shape with a bottom.
A casing 14 fitted into the inner hole of the casing 14 and a motor base 15 flanged to the casing 14 are integrally formed concentrically. A pulse motor 16 is mounted on the motor stand 15 and rotates by an amount corresponding to the number of command pulses in response to a rotation command from the control device, and the motor shaft 17 is provided to protrude into the hollow part of the motor stand 15. ing. The ball screw, which is generally designated by the reference numeral 18, is a screw mechanism that converts the rotation of the motor shaft 17 into motion in the axial direction. The screw shaft 19 and the motor shaft 17 are connected by fitting their tapered portions into the tapered holes of the coupling ring 20 and tightening them with nuts. The ball screw 18 includes a bottomed cylindrical nut 22 that is screwed through a ball 21 to a threaded portion of a screw shaft 19 facing into the inner hole of the casing 14, and the screw shaft 19 is rotated in the forward direction and in the reverse direction. By rotating to and fro, the nut 22
moves forward in the direction of the valve body 13 and the motor 16
It is configured to move backward in the direction. 2
3 is an air freezer, 24 is a permanent magnet attached to the circumferential surface of the nut 22, and 25 is a proximity switch that is sensitive to the movement of the permanent magnet 24. The movement distance in the axial direction of the nut 22 and a spool 27, which will be described later, is accurately controlled. A position detector 26 which detects and feeds back to the control device is a key fixed to the casing 14 side and fitted into a key groove of the nut 22 to restrict rotation of the nut 22. What is generally designated by the reference numeral 27 is a cylindrical spool body 28 and a spool shaft 29 passing through the center of the spool body 28.
The spool shaft 29 is a spool integrally formed with a through shaft 29a in the center, a connecting shaft 29b on the ball screw 18 side, and an end shaft 29c at the opposite end, which are concentric. It is integrally formed with
Of these, the connecting shaft 29b has a tip end flange attached to a tightening tool 30.
It is concentrically fixed to the end face of the nut 22 by the screws. The connecting shaft 29b is slidably supported by the casing 14 via a bearing 31, and the end shaft 29c is supported by a bearing 31 on the end plate of the valve body 13.
2, and is slidably supported. The spool body 28 is pivotally supported in the inner hole of the casing 14 so as to be able to move forward and backward, and has a front chamber 33, through which the end shaft 29c passes, and a rear chamber 34, through which the connecting shaft 29b passes, at both ends in the axial direction. It is formed. Further, the spool body 28 is provided with a plurality of communication holes 35 for communicating between the front chamber 33 and the rear chamber 34, and furthermore, the communication holes 35 and the spool body 28 are provided in the longitudinal center of the spool body 28. An annular groove 36 is provided that communicates with the outside of the main body 28. On the other hand, a pair of annular communication grooves 37 and 38 are provided in the shaft portion of the spool body 28, and the depth is the same as that of the valve body 13.
7 and 38 are partially communicated by a connecting path 39. The flow rate control valve 11 configured in this manner has a hydraulic oil inlet 40 opened in the front chamber 33 connected to an accumulator provided in the hydraulic piping, and a hydraulic oil inlet 40 provided in the connecting passage 39. The outlet 41 is connected to the injection cylinder of the die casting machine. Then, by retracting the spool 27 to the right in the figure via the ball screw 18 by the rotation of the pulse motor 16, the front chamber 33 and the communication groove 37 and the annular groove 36 and the communication groove 38 are brought into communication at the same time, and the inflow port The hydraulic oil flowing in from 40 is sent to the injection cylinder from the outlet 41, and the amount of oil sent changes depending on the opening degree of the communication grooves 37 and 38 by the spool 27, so that the injection speed of the molten metal by the injection cylinder is controlled. It is composed of In this flow rate control valve 11, as described above, the spool 27 has an end shaft 29c passing through the front chamber 33 and a connecting shaft 29b passing through the rear chamber 34.
are provided on both end sides, and the diameter of the end shaft 29c indicated by the symbol d in the figure is smaller than the diameter of the connecting shaft 29b indicated by the symbol D in the figure. Next, such an end shaft 29c is attached to the spool 27.
The relationship between the acting forces and the like when the connecting shaft 29b is provided at the end opposite to the connecting shaft 29b will be described. First, in the flow control valve 11 configured as described above, considering the equilibrium state when the valve opening degree by the valve spool 27 is 0 point (when the valve is closed), the pressure in the front chamber 33 and the rear chamber 34 is Due to the presence of the communication hole 35, the supply pressure of hydraulic oil is P ₀ in both cases. Therefore, in FIG.
The acting force on the right side acting on valve 7 is FA, the acting force on the left side is FB, the acting force from the motor 3 on the left side in the figure is F, and the diameter of the inner hole of the housing 12 that holds the valve spool 27 is If Q, then FA=(π/4Q ² −π/4d ² )P ₀ FB=(π/4Q ² −π/4D ² )P ₀ , and in order to maintain this valve closed state,
F derived by FA=FB+F (=FA−FB)
It is necessary to convert the torque T of the motor 3 into a linear force and support it by the screw mechanism 18. Then, if the absolute stress value of the compressive stress or tensile stress acting on the connecting shaft 29b due to this force F is σ, F becomes F=π/4D ² σ. And to summarize these formulas, F=FA−FB=(π/4Q ² −π/4d ² )P ₀ −(π/4Q ² −π/4D ²
) P ₀ = π/4D ² σ, and as a result, the relationship between the absolute stress value σ and the hydraulic oil supply pressure P ₀ mentioned above and the cross-sectional area of both shafts 29b and 29c is π/4D ² σ = π/ It is expressed as 4D ² P ₀ −π/4d ² P ₀ D ² σ=(D ² −d ² )P ₀ . Note that from the above formula, σ=D ² −d ² /D ² P ₀ is derived, and this absolute stress value σ is
Regardless of the valve opening degree S depending on the stroke position of
It is established and determined. By substituting d=0 in this equation, the end shaft 29c
It is also clear from the fact that the absolute stress value σ in the conventional example without is the hydraulic oil supply pressure P ₀ . Under the above conditions, the capacity of the motor 16 is its maximum stress value (in the example shown in FIG. 4, P ₀ when the valve opening degree S is 0)
is required at least, and if this capacity is not present, the motor 16 side will be rotated in the opposite direction due to pressure. The present invention takes into consideration the various conditions mentioned above, and the motor 1
In order to reduce the required power, that is, the absolute value σ of the stress, the valve opening degree-stress characteristic shown in FIG. 4 is entirely translated in parallel, and the stress width P is changed as shown in FIG. Tensile stress + σ side and compressive stress - σ
It is divided into two equal parts, and the positive and negative sides have the same amplitude. Therefore, in the above-mentioned equation, it is preferable to substitute P/2 for σ and expand this to obtain the diameter d of the end shaft 29c. Here, the stress width P mentioned above is the value of the valve spool 27
When the valve operates to open and close the fluid passage between the opening degree of 0 and the maximum opening degree, the force generated in the axial direction of the connecting shaft 29b through the valve spool 27 due to the acting force due to the fluid flow is This corresponds to the maximum change width calculated in terms of stress, that is, the sum of the maximum compressive stress value and the maximum tensile stress value, and this corresponds to the flow state at the throttle part of the fluid passage opened and closed by the valve spool 27. It is determined by the pressure change caused by the change in pressure, and can be determined by experiment using a conventional model without the end shaft 29c. In addition, the hydraulic oil supply pressure P ₀ is determined by the application,
Furthermore, the diameter D of the connecting shaft 29b with the motor 16 side is
It is set to a certain value from a structural standpoint, taking into consideration its strength, etc., and by substituting these into the above formula,
It is preferable to determine the diameter d of the end shaft 29c that satisfies this equation. The operation of the flow control valve configured as above is as follows.
explain. First, before the casting operation of the die-casting machine starts, the spool 27 is in the position shown in the figure, and the communication grooves 37 and 38 are closed by the outer peripheral surface of the spool body 28. When a command to start injection is issued from this state and the pulse motor 16 rotates by a predetermined angle, the screw shaft 19 connected by the coupling ring 20 rotates, and the nut 22 and the integral spool 27 that are screwed together rotate. Move back to the right. Therefore, the front chamber 33
The communication groove 37 and the annular groove 36 communicate with the communication groove 38, and the hydraulic oil from the inflow port 40 passes through the communication hole 35 to the rear chamber 34, and the communication grooves 37 and 38 communicate with the connection path 39. Outlet 41 after Tonogi
The molten metal is supplied to the injection cylinder from where the molten metal is poured. At the initial stage of injection, the communication groove 3
7 and 38 are small, the flow rate of hydraulic oil is small, and the injection speed is low. However, when injection continues and a command for high-speed injection is sent to the pulse motor 16 after a predetermined time, the pulse motor 16 rotates again. However, as the spool 27 moves further back and the opening degree of the communication grooves 37 and 38 increases, the flow rate of the hydraulic oil increases and the injection speed increases. In this case, the position detector 25 is sensitive to the movement of the permanent magnet 24 and the spool 2
Since the movement distance of the pulse motor 7 in the axial direction is accurately detected and fed back to the control device, the pulse motor 1
6, that is, the injection speed by the opening degree of the spool 27 is correctly controlled. In such a flow rate control operation, if the end shaft 29c is not provided as in the conventional case, the fourth
As explained in the figure, a stress width P is generated and power corresponding to this is required, but if we assume that the end shaft 29c is provided and its diameter d is gradually increased from 0, then the opening shown in FIG. , the stress curve gradually moves to the tensile stress +σ side while maintaining the stress width P, and as mentioned above,

When the diameters D and d are set so as to satisfy [Formula], this curve becomes as shown in FIG. That is, FIG. 2 is shown in correspondence with FIG.

〔Effect of the invention〕

As is clear from the above description, according to the flow control valve according to the present invention, both ends in the axial direction of the valve spool for opening and closing the fluid passage, which is driven by the motor via the screw mechanism and moved forward and backward within the housing, The connecting shaft on the screw mechanism side and the end shaft on the fluid inlet side are pivotally supported on the housing side, and the diameter d of this end shaft is determined by the shape of the fluid passage constriction part by the valve spool, and the connection is made when the valve spool is operated. With a certain relationship based on the stress width P generated in the axial direction on the shaft and the hydraulic oil supply pressure _P0 , the diameter D of the connecting shaft is made smaller than the diameter D, so that the maximum tensile force acting on the connecting shaft is It can be configured so that the stress and the maximum compressive stress are almost equal, and this greatly reduces the power required to move the valve spool forward and backward compared to the conventional system in which the valve spool is pivotally supported only on the screw mechanism side. Therefore, it is possible to reduce the capacity of the drive motor, which has various excellent effects such as reducing equipment costs and power costs. Furthermore, according to the present invention, it is possible to increase the tensile stress that acts as a braking force when stopping the valve spool at a predetermined valve opening position, so the timing of stopping the valve spool can be made earlier than in the past. For example, by using it in a die-casting machine, etc., it is possible to quickly switch from low-speed injection to high-speed injection, and it is possible to move to stable high-speed injection that much faster, making it easier to obtain high-quality products. Play advantage.

[Brief explanation of drawings]

1 and 2 show an embodiment of the flow control valve according to the present invention, FIG. 1 is a longitudinal sectional view thereof, and FIG.
The figure is a diagram showing the relationship between the spool opening and the stress on the spool shaft, Figure 3 is a schematic cross-sectional view of a conventional flow control valve, and Figure 4 is the relationship between the spool opening and the stress on the spool shaft in the same conventional structure. It is a line diagram. 11...Flow control valve, 12...Casing, 13...
Valve body, 14...Casing, 16...Pulse motor, 18...Ball screw, 27...Spool, 28...Spool body, 29...Spool shaft, 29b...Connection shaft, 29c...End shaft, 33...
...front chamber, 34...rear chamber, 35...communication hole, 36...
...Annular groove, 37, 38...Communication groove, 40...Inflow port, 41...Outflow port, D...Diameter of connecting shaft, d...
Diameter of end shaft.

Claims (1)

[Scope of Claims] 1. A motor that can control the amount of rotation, a valve spool connected to the motor via a screw mechanism that converts the rotation into axial movement, and a motor that can move the valve spool back and forth in the axial direction. A casing that is freely pivoted and forms a front chamber and a rear chamber on both ends of the valve spool in the axial direction, a communication passage that communicates between the front chamber and the rear chamber, and a fluid flow opening in the front chamber. A flow rate regulating valve comprising an inlet and a fluid outlet opened in the casing that communicates with the fluid inlet by a fluid passage that is opened and closed by the forward and backward movement of the valve spool, the valve spool comprising: The connecting shaft with the screw mechanism and the end shaft on the front chamber side are pivotally supported on the housing side, and the diameter d of the end shaft is made smaller than the diameter D of the connecting shaft. Here, P: Stress width generated in the axial direction on the connecting shaft when opening and closing the fluid passage of the valve spool _P0 : The diameter of the connecting shaft is formed smaller than D so that the relationship of hydraulic oil supply pressure holds. flow control valve.