JPS5834203A - Impact preventive device - Google Patents

Abstract

PURPOSE:To improve the shock absorbing effect in a device described at the head which is capable of damping residual oscillation shock produced when a whirling device or so of a shovel loader is stopped by adruptly reducing a fluid pressure in a main circuit at the high pressure side which is developed adjacently to the completion of a pressure control valve for controlling brake pressure. CONSTITUTION:Residual oscillation preventive valves 13 and 13' are placed in parallel with a brake circuit not illustrated between main circuits 2 and 3 for supplying on/discharging pressure oil for or from a hydraulic motor which drives a whirling member of a shovel or so. Among the valves 13 and 13' which are similarly designed, the valve 13 damps shock resulting from a rise in pressure in the main circuit 3 which is developed due to inertia revolution of the motor when a direction change-over valve (not shown) is shifted into the neutral position, with the main circuit 2 supplying the motor with pressure oil. Namely, when the pressure in the main circuit 3 is increased over a certain value, a spool 1 is moved left to lessen force of the pressure oil and when pressure in the main circuit 3 is reduced due to reduction in said inertia force, a check valve 27 is opened to quickly flow the pressure oil into the main circuit 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an impact prevention device capable of mitigating the swinging back impact of a driven member such as a construction machine when the driven member stops.

In construction machines such as excavators that are equipped with a complete pressure fluid circuit, pressure fluid from a pressure fluid source is selectively supplied to an actuator to operate it, and the power generated in this actuator is transmitted to a driven member such as a boom. In addition, in order to stop the driven member, a brake circuit is also provided with a brake valve that controls the fluid pressure on the back pressure side of the actuator to apply a brake force.

However, for example, in a swinging device of an excavator, a reduction gear is provided between a driven member and an actuator for driving the drive member, and the amount of play in the reduction gear (for example, the para-clash of the gears of the reduction gear) is In the case where the mass material can freely operate, when the actuator is stopped, the inertial force of the driven member acts on the actuator, and the fluid pressure due to this inertial force is accumulated in the fluid circuit and the actuator is stopped once. Since the force that drives the driving member in the opposite direction acts as a lock, the driven member swings back by the amount of play in the reducer, and due to the inertia of this swing back, fluid pressure is accumulated in the pressure fluid circuit in the same way as above. As a result of causing the driven member to swing back in the opposite direction again, the driven member swings back several times and then stops.

There is a device disclosed in Japanese Utility Model Application Laid-Open No. 54-35986 as a device for alleviating such back-swinging and its impact.

As shown in FIG. 6, this device has a brake circuit between two main circuits 2 and 3 for supplying and discharging pressurized fluid connected to an actuator l that drives a driven member (not shown). Relief valves 4.5 are connected in parallel, and springs 6 on both sides are connected in parallel.
, 7, both pressure chambers 10. ll are connected to the main circuit 2゜3 through apertures 12a and 12b, respectively, and when stopping the actuator l rotating in the direction of arrow A, the inertia of the driven member causes the back When the fluid pressure in the pressure side main circuit 2 increases, the pressure is controlled by the relief valve 4 and the fluid is transferred to the other main circuit 3.
and one pressure chamber 1 of the accumulator 9.
To stop actuator l, which is designed to flow 4 degrees to 0 and is rotating in the direction of arrow B, on the other hand,
The pressurized fluid in the main circuit 3 is pressure-controlled by the relief valve 5 and flows out into the main circuit 2, and also flows into the other pressure chamber 11 of the accumulator 9. Therefore, the tension of the springs 6, 7 of the accumulator 9, the pressure chamber 10
．． By adjusting the volume of 11 and the throttle amount of throttles 12a and 12b, respectively, and delaying the end of operation of accumulator 9 from the end of operation of relief valve 4.5, the swinging back of the driven member and its impact are alleviated. This makes it possible to do so.

However, in the case of the above device, since pressure starts to accumulate in the accumulator 9 from the time when braking is started, if the braking force, that is, the set pressure of the relief valves 4 and 5 is increased, it is necessary to increase the volume of the accumulator 9, and the accumulated pressure fluid It is also necessary to release the pressure to the main circuit on the back pressure side.
There was a drawback that it was not possible to obtain a sufficient function to prevent swinging back and its impact.

This invention provides a pressure control valve that controls brake pressure between two main circuits for supplying and discharging pressurized fluid connected to an actuator, and a pressure control valve that operates in an overship manner at the end of the operation of this control valve. A valve is provided in parallel with the pressure control valve, and near the end of the operation of the pressure control valve, the swing back prevention valve promptly releases the brake pressure (fluid pressure) to the opposite main circuit in accordance with the amount of downward slope of the brake pressure (fluid pressure) in the back pressure side main circuit. This causes the pressure to drop rapidly, thereby alleviating the swinging back of the driven member and its impact.

Hereinafter, the impact prevention device of the present invention will be explained in detail based on the drawings showing all the embodiments.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which 1 is an actuator for driving a driven member (hereinafter referred to as a motor), and this motor 1 has a counterbalance installed in the middle. Valve 14 and directional valve (not shown)
Two main circuits 2.3 for supplying and discharging pressurized fluid are connected. Between these main circuits 2 and 30, a brake circuit 16 equipped with pressure control valves 15 and 15' is provided, and in parallel with this, a swing back prevention valve 13°1, which will be described later, is installed.
3 is provided.

One pressure control valve 15 of the brake circuit 16 controls the total fluid pressure in the main circuit 3, and the other pressure control valve 15' controls the fluid pressure in the main circuit 2, for example, a balance piston type valve. A pressure control valve or the like is used. These pressure control valves 15, 15' have characteristics of pressure P and flow rate Q as shown by the solid line No. 0 in FIG. 3
is closed, the pressure control valve 15' starts operating when the fluid pressure in the main circuit 2 on the back pressure side rises to Pl, and the pressure fluid in the main circuit 2 flows out to the main circuit 3. The WLq body p in the main circuit 2 is controlled to P2.

Therefore, a braking force corresponding to this fluid pressure pi is applied to the motor IK. Conversely, when the main circuit 2.3 is closed when the motor I is rotating in the direction of arrow B, K
li, the other pressure control valve 15 is activated and controls the fluid pressure in the main circuit 3 to t Pz.

Specifically, the swing back prevention valve 13.13' is
It has a structure as shown in FIG. These swing back prevention valves will be explained below, but in both cases of FIGS. 2 and 3, the swing back prevention valve 13 and the swing back prevention valve 13' have the same configuration, so one Only the oscillation prevention valve 13 will be explained, and the other swing back prevention valve 13' will only be indicated by using the same numbers for the same parts and dashes in all lines, and the explanation thereof will be omitted.

The swing back prevention valve 13 illustrated in FIG. Part 17
A first pressure chamber 21 is provided at the side end, and a second pressure chamber 23 is provided at the end on the small diameter portion 18 side, and a spring 22 that applies a constant pressing force to the tube 1-19 is tensioned inside. Furthermore, a third pressure chamber 25 is provided around the intermediate portion 24 between the large diameter portion 17 and the small diameter portion 18.
They are formed respectively.

The spool 19 is formed to pass through an internal passage 26,
A check valve 27 having a throttle hole 28 is provided in the internal passage 26.
This is provided. The forward direction of this check valve 27Fi is the direction from the internal passage 26 to the third pressure chamber 25 via the through hole 29 of the intermediate portion 24. It is connected to one main circuit 3 for supplying and discharging pressurized fluid through the spool 19, and also communicates with the spool internal passage 26 through an end opening 30 and a through hole 31 on the large diameter portion 17 side of the spool 19.

In addition, the second pressure chamber 23 has a spring receiver screwed into the end opening on the small diameter portion 18 side of the spool 19 and a through passage 3 of the member 34 .
5. The third pressure chamber 2511 communicates with the internal passage 26 of the spool 19 through the throttle hole 28 of the check valve 27.
, connection port) 33"i to the other main circuit 2 for supplying and discharging pressurized fluid, and when the check valve 27 opens, the main circuit 3 for supplying and discharging one pressurized fluid passes through the internal passage 26. When the pressure in the main circuit 3 increases, the pressure in the first pressure chamber 21 and the second pressure chamber 23 also increases, but at this time, the spool 19 has a large diameter Since fluid pressure acts on the difference in the pressure receiving area between the pressure receiving area 17 and the small diameter portion 18, when the pressing force due to the fluid pressure acting on the difference in the pressure receiving area overcomes the pressing force of the spring 22, the fluid in the second pressure chamber 23 reverses. Since the flow flows into the first pressure chamber 21 through the entire throttle 28 of the stop valve 27, it moves toward the second pressure chamber 23. Then, the pressure in the main circuit 3 begins to decrease, and the large diameter portion 17 and the small diameter portion of the spool 19 move toward the second pressure chamber 23. When the pressing force of the spring 22 overcomes the pressing force due to the fluid pressure in the main circuit 3 which acts on the difference in pressure receiving area between the spool 19 and the spool 18, the spool 19
The fluid moves in the direction of the pressure chamber 21, but at this time, fluid flows into the second pressure chamber 23 via the first pressure chamber 21, the internal passage 26, and the restrictor 28 of the check valve 27. 27 is moved toward the second pressure chamber 23 due to the difference in fluid pressure occurring before and after the throttle 28 . When the check valve 27 operates in this manner, the main circuit 2.3 communicates with the first pressure chamber 21, the internal passage 26 and the third pressure chamber 25.
Therefore, the value of the fluid pressure in the main circuit 3 when the spool 19 starts full operation and when it starts returning is the same as the spool 19.
By changing the difference in pressure receiving area between the large diameter part 17 and the small diameter part 18 of 9 and the elastic resistance of the spring 22, it is possible to increase or decrease the value to a desired value, and the opening time of the check valve 27 can also be adjusted. This swing back prevention valve 13 can be adjusted to a desired time by adjusting the throttle amount of the first throttle hole 28 and the volume of the second pressure chamber 23. When the spool 19 reaches a pressure value (almost the same as the pressure value Pφ) slightly lower than the cracking pressure P1 of the one pressure control valve 15 that operates in conjunction with the swing back prevention valve 13, the spool 19 moves toward the second pressure chamber 23. The fluid pressure in the main circuit 3 is controlled to the set pressure Pz of the pressure control valve 15 and then lowered to reach the cracking pressure Pz.
The fluid pressure in the main circuit 3 decreases to a pressure value slightly lower than the cracking pressure P1 so that the spool 19 starts to return and the check valve 27 starts to open when the pressure value P3 reaches a pressure value slightly lower than 1. The start timing of the operation and return of the spool 19, the opening time of the check valve 27, etc. are adjusted as described above so that the check valve 27 closes when PL+ is reached and the return of the spool 19 is completed immediately before that. Adjustments are being made.

The other swing back prevention valve 13' has a first pressure chamber 21 connected to the main circuit 2 for supplying and discharging pressurized fluid, and a third pressure chamber 25' connected to the main circuit 2 for supplying and discharging pressurized fluid.
is connected to the other main circuit 3 for supplying and discharging pressure fluid,
As described above, the connection relationship to the main circuits 2 and 3 is opposite to that of the above-mentioned swing back prevention valve 13, and the above-mentioned swing back prevention valve A swing back prevention valve 13.13' having the same configuration as the valve 13, such as 0 or more, is connected to the main circuit 2.3.
Regarding the operation of the embodiment shown in FIG. 1, which is provided in parallel with the pressure control valves 15 and 15' between 15 and 15', we will take as an example the case where this is applied to the boom swinging device of an excavator.
Characteristic surface #! representing the relationship between time t and pressure P shown in b)! The counterbalance valve 14 is moved to the switching position 14a by operating the directional switching valve from the state shown in FIG.
When the switch is made, pressurized fluid is supplied to the motor 1 via the main circuit 2, and fluid from the motor 1 flows out through the main circuit 3, the counter 7 (the lance valve 14, and the directional control valve) to a tank (not shown). , the motor l rotates in the direction of arrow B.0 This rotation causes the driven member, the boom (0, not shown), to be driven via the reduction gear (0, not shown).0 The rotation of the motor l becomes a constant speed rotation. When the fluid pressure in the main circuit 2 reaches the operating start pressure P+ of the spool 19 of the swing back prevention valve 13, as shown in curve (a) of FIG. 5(b),
On the other hand, the fluid pressure in the main circuit 3 becomes a low value P7 due to the circuit resistance of the counterbalance valve 14, directional control valve, etc. In this rotating state, the fluid pressure in the main circuit 2 becomes lower than that in the brake circuit. The fluid pressure acts on the first pressure chamber 21' of the 16 pressure control valve 15' and the swing back prevention valve 13', respectively, and this fluid pressure is caused by the cracking pressure P1 of the pressure control valve 15' and the spool of the swing back prevention valve li3'. Since the operation start pressure Pm has not been reached, both the pressure control valve 15' and the swing back prevention valve 13' barely operate. When the directional control valve is operated to the neutral position at time t1 while the motor l is rotating, the counter The lance valve 14 is switched to the neutral position 14b and the main circuit 2.3 is closed.Thus, the supply and discharge of pressure fluid to and from the motor 1 is stopped, but the motor 1 is closed.

- The fluid pressure in the main circuit 3 begins to rise rapidly as shown in the curve (b) of FIG. 5(a), and the pressure control valve 15 and the Then, the fluid pressure in the main circuit 3 reaches the spool operation start pressure P of the swing back prevention valve 13, and the first pressure chamber 21 of the swing back prevention valve 13 and this When the fluid pressure in the communicating second pressure chamber 23 reaches the operation start pressure P-, the large diameter portion 17 and the small diameter portion 1 of the spool 19
The spool operating force generated by the pressure receiving area difference between springs 8 and 8 is
The pressing force of 2 is greater than that of spool 19.
The spool begins to slide toward the second pressure chamber 23. At the time of this spool sliding, the pressure fluid in the second pressure chamber 23 passes through the check valve 2.
Since the flow flows toward the first pressure chamber 21 through the throttle hole 28 of No. 7, that is, the check valve 27 flows in the opposite direction to the forward direction in which the check valve 27 is opened.
0 is displaced toward the pressure chamber 23. Therefore, while the fluid pressure t in the main circuit 3 is rising, the check valve 27 has no opening force, so one main circuit 3 and the other main circuit 2 are closed. Thus, as the fluid pressure S in the main circuit 3 increases,
The pressure control valve 15 is activated, and thereby the fluid pressure is controlled to the control set pressure values P and L of the control valve 15. motor l depending on this control fluid pressure).

A rake force is applied, and the inertial force of the boom begins to decrease, and the rotational force of the motor l also begins to decrease.At this time, the fluid pressure fd in the main circuit 3, the characteristic curve e of the pressure control valve 15 in FIG. Accordingly, as shown in FIG. Since the fluid pressure in the pressure chamber 21 and the second pressure chamber 23 as well as P3Ifp become the return start pressure of the spool 19,
The pressing force of the spring 22 overcomes the pressing force acting on the spool 19, and the spool 19 begins to return toward the first pressure chamber 21. When the spool 19 begins to return, the volume of the second pressure chamber 23 increases. The pressure fluid on the first pressure chamber 21 side passes through the throttle hole 28 of the check valve 27 and enters the second pressure chamber 23.
However, since the flow rate passing through the throttle hole 28 is small, negative pressure is generated on the second pressure chamber 23 side, and the first pressure chamber 2
The pressure is lower than the fluid pressure on the first side. When a pressure difference occurs in this way, the check valve 27 begins to open, and both main circuits 2.3
is the first pressure chamber 21. Since the spool internal passage 26 and the third pressure chamber 25 communicate with each other, the pressure fluid in the main circuit 3 quickly flows out to the other main circuit 2. When the check valve 27 is opened, the rotational force of the motor 1 and the inertia of the boom are also reduced, so when the pressure fluid in the main circuit 3 flows out to the other main circuit 2, the inside of the main circuit 3 is reduced. The fluid pressure suddenly decreases as shown in the curve of FIG. 5(a). Then, just before the fluid pressure in the main circuit 3 reaches p4, the return of the spool 19 is completed, and when the fluid pressure reaches P, the check valve 2
7 closes and both main circuits 2 and 3 are completely cut off, so the motor l stops.

Note that even if motor 1 stops, the inertia of the boom is not completely absorbed, so the boom moves in the opposite direction (swings back).
The fluid pressure in the main circuit 3.2 is as shown in Fig. 5(a), (
The curve (e) in b) becomes as shown in →゛.

The above is a case where main circuit 2 is operated for supply and main circuit 3 is operated for discharge, but conversely, main circuit 2 is operated for discharge and main circuit 3 is operated for discharge.
When operated for supply, the other pressure control valve 15' and swing back prevention valve 13' function in the same way, so a detailed explanation thereof will be omitted.

In the swing back prevention valve 13aI/i illustrated in FIG. 3, a sleeve 36 is internally fixed in the opening 20a of the main body.
A spool 19ai of different diameters having a large diameter part 17a and a small diameter part 18a is slidably fitted into the inside of the inner hole 2.
There is a radial gap 37 between Oa and the sleeve 36.
This radial gap 37 is partially formed in a1.
a is the main circuit 2 via the 5 passage 38 and the connecting bow) 33ai
is connected to.

A first
A pressure chamber 21a is formed, and a barb 22a that applies a constant pressing force to the spool 19a is provided at the end of the spool 19a on the side opposite to the first pressure chamber 21a, that is, on the small diameter portion 18a side of the spool 19a. Second pressure chamber 2 stretched inside
3a'Ik is formed. Further, a third pressure chamber 25a'ii is formed between the intermediate portion 24a between the large diameter portion 17a and the small diameter portion 18a of the spool 19a and the sleeve 36.

Internal passage 26a of spool 19a Kif-shaped check valve 27
A indicates a direction from the first pressure chamber 21a to the second pressure chamber 23a as the forward direction, and this check valve 27a is connected to the large diameter portion 2.
7b and a small diameter portion 27c, and the outer peripheral surface of the small diameter portion 27c is formed with an annular groove 27di that continues to the large diameter portion 27b.And, in the middle of the internal passage 40 of this check valve 27a, there is a throttle hole. 28a is provided. The first pressure chamber 21a is fixed to the internal passage 40 of the check valve 27a provided in the middle of the throttle hole 28ak, the internal passage 26a of the spool 19a, and the end of the spool 19a on the small diameter portion 18a side. The spring receiver communicates with the second pressure chamber 23a through a through hole 35a of a member 34a (a cap-like member having the same outer diameter as the small diameter @ l 8 a), and furthermore, this second pressure chamber 23a communicates with the passageway of the main body. 41a and connection 1-) 33ata are connected to the main circuit 3, and the third pressure chamber 25a communicates with the radial gap 37a, which communicates with the main circuit 2, through the through hole 42 of the sleeve 36. , communicates with the annular groove 27d of the check valve 27a through the through hole 43 of the spool 19a. Therefore, when the check valve 27a is opened, both main circuits 2°3 are connected to the passage 38 of the main body, the radial Gap 37a1 Third pressure chamber 25a1 Annular groove 27d1 Internal passage 26a1 Second pressure chamber 23a and main body passage 41a
This swing return prevention valve 13 is also connected to the pressure control valve 1 of the above-mentioned one side.
In conjunction with the valve 5, the valve 13 performs the same function as the anti-swing valve 13 shown in FIG. When the main circuit 3 on the discharge side is stopped, the fluid pressure in the main circuit 3 on the discharge side rises rapidly, and the fluid pressures in the first pressure chamber 21a and the second pressure chamber 23a also rise equally rapidly.
When the operating start pressure P- of 9a is reached, the operating pressure generated by the difference in pressure receiving area between the large diameter portion 17a and the small diameter 518a of the spool 19a becomes greater than the pressing force of the spring 22a, and the spool 19a moves toward the second pressure chamber 23. Slide towards. At this time, the pressure fluid flows from the second pressure chamber 23a toward the first pressure chamber 21a, that is, in the opposite direction where the check valve 27a cannot open. It is displaced toward the second pressure chamber 23a together with the spool 19a.

Then, the fluid pressure in the main circuit 3 further increases, and the pressure feed control valve 1
When the pressure exceeds the set pressure P2 of 5, the pressure of the brake circuit 16 and the main circuit 3 is controlled by the control valve 15, and a braking force is applied to the motor l, so that the rotation speed of the motor l decreases. The inertial force of decreases and the fluid pressure in the main circuit 3 also decreases, but when this fluid pressure decreases to P3 and the pressure in the first and second pressure chambers 21a+23a becomes P, the pressing force of the spring 22 decreases. becomes larger than the operating force due to the fluid pressure of the spool 19a, and the spool 19a returns to the first pressure chamber 21a. Due to the return of the spool 19a, the fluid in the first pressure chamber 21a is reduced by the restriction of the check valve 27a.
928a into the second pressure chamber 23a, the pressure on the first pressure chamber 21a side increases, and this pressure difference opens the check valve 27a, so the pressure fluid in the main circuit 3 flows through the main body passage. 41, second pressure chamber 23, spool internal passage 2
6a1 Annular groove 27d1 of check valve 27 3rd pressure chamber 25a1
It sequentially passes through the radial gap 37 and the passage 38 and flows out to the other main circuit 2, resulting in the curve shown in FIG. 5(a))
As shown by K, the fluid pressure in the main circuit 3 suddenly drops. Then, the return of the spool 19a is completed just before the fluid pressure reaches 4, and when it reaches P, the check valve 27a closes and cuts off both main circuits 2.3, so the motor l stops, and after the stop The fluid pressure in the main circuit 2.3 is as shown in Fig. 5 (a) and (b).
) song 11A (E), the pressure is low and does not cause large fluctuations, so large swing back and its impact will not occur. ', the second pressure chamber 23a' is connected to the main circuit 2 through the passage 38 and the connection port 33a', and the third pressure chamber 25a' is connected to the radial gap 37.
a', is connected to the other main circuit 3 via the passage 38', and the connection boat 33a, and works in conjunction with the other pressure control valve 15' to cause the pressure fluid in the main circuit 2 to flow out to the main circuit 3 when the motor is stopped. The swing back prevention valve 13 is
It has exactly the same configuration as a.

As can be understood from the above description, the shock prevention device of the present invention includes a pressure control valve that controls the braking force of the actuator, and a pressure control valve that controls the braking force of the actuator between the two main circuits connected to the actuator of the pressure fluid circuit. By providing a swing back prevention valve that operates in a fluid pressure range near the end of operation in parallel, the fluid pressure in the high-pressure main circuit near the end of operation of the pressure control valve can be rapidly reduced, thereby reducing the pressure of the actuator. This device has the effect of mitigating the swinging return of the driven member and its impact, and the setting pressure of the pressure control valve and the operation of the swinging return prevention valve are adjusted depending on the magnitude of the inertia of the driven member. By varying the pressure range, operating time, etc., it can be used in various pressure fluid circuits. Furthermore, since the swing return prevention valve is not a direct acting type, but a differential pressure type valve that incorporates a different diameter spool having a large diameter part and a small diameter part, it is possible to reduce the size of the spring for returning the spool. , unlike a switching valve with a fixed restrictor that has a constant flow rate, while the reverse valve in the spool is open, the flow rate of the pressure fluid changes depending on the degree of drop in fluid pressure in the high-pressure side main circuit. However, it has the effect of efficiently flowing out toward the low-voltage side main circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing an example of the swing back prevention valve shown in FIG. 1, and FIG. 3 is a cross section showing another example of the swing back prevention valve. Figure 4 is a characteristic curve of pressure and flow rate of the pressure control valve, Figure 5 (a) is a characteristic curve of time and pressure of the high pressure side main circuit during actuator stop operation, and Figure 5 (b) is a characteristic curve of pressure and flow rate of the pressure control valve. 6 is a characteristic curve diagram of time and pressure of the low-pressure side main circuit, and FIG. 6 is a circuit diagram of the prior art. l・Actuator, 2, 3... Main circuit, 13° 13
・・Swing back prevention valve, 14 ・・Counter balance valve, 1
5.15'...Pressure control outlet valve, 17 Large diameter part, 18...
Small diameter part, 19... Spool, 21... First pressure chamber, 22
・・Spring, 23・・Second pressure chamber, 25・Third pressure chamber, 2
6-internal passage, 27-check valve, 28-throttle hole. Patent applicant: Japan Air Brake Co., Ltd.
Kobe Steel Co., Ltd. Representative Mihiko Watanabe Figure 3

Claims (1)

[Claims] 1. A pressure fluid circuit in which two main circuits for supplying and discharging pressure fluid are connected to an actuator, and a pressure control valve and a vibration prevention valve that are provided in parallel between the two main circuits, and this vibration The return prevention valve has one large diameter part and one small diameter part! A check valve with a throttle hole in the internal passage that can be slid freely across all stages.
A λ spool, a first pressure chamber formed at the end of the large diameter side of the spool and connected to one of the main circuits and the internal passage, respectively; and a first pressure chamber formed at the end of the spool on the small diameter side and connected to the spool. a second pressure chamber having a spring tensioned therein for applying a constant pressing force and connected to the first pressure chamber through the throttle hole of the check valve; the other side of the main circuit and the internal passage; and a third pressure chamber connected to one of the main circuits via the reverse ratio valve.