JP2003185043A - Electric relief valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric relief valve capable of preventing unusual rise of a relief pressure even if a surge current is inputted. <P>SOLUTION: A main poppet 22 is provided openably and closably between a passage 41 to be pressure controlled and a tank 17, and a pilot poppet 28 controlling pilot pressure introduced from the passage 41 into a spring chamber 33 opposite side to a main poppet 22. A spring 47 is interposed between the pilot poppet 28 and a movable part 30 of a solenoid 29 driving the pilot poppet 28 in the trapping direction of the pilot pressure during current carrying. A stroke limiter 51 is provided to regulate a travel stroke (St) of the movable part 30 of the solenoid 29. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric relief valve having a solenoid.

[0002]

2. Description of the Related Art When a hydraulic excavator or the like is used to electrify a hydraulic system, an electric relief valve that electrically controls a conventional main relief valve to control system pressure can be considered.

FIG. 6 is a simplified hydraulic circuit showing common piping for a hydraulic excavator. In the attachment circuit of the hydraulic excavator, an electric relief valve is used for pressure control of the attachment circuit.

An attachment circuit 13 is connected to the hydraulic pump 11 via a control valve 12. The attachment circuit 13 includes a plurality of electric relief valves 15 and electric check valves 16 so that various attachments 14 can be accommodated.
Is provided in the passage to the tank 17.

That is, the operator in the cab of the hydraulic excavator electrically switches the electric relief valve 15 and the electric check valve 16 to switch the circuit from inside the cab (single-acting, double-acting, using one pump, (2 pumps used)
And the relief pressure can be changed.

The control valve 12 has a pilot-operated spool 18 for controlling the hydraulic actuator 14a of the attachment 14 and a make-up function that enables a make-up operation when a vacuum occurs in the circuit. Line relief valve 19 of is installed.

Then, the spool 18 in the control valve 12
Is in the neutral position, an external force acts on the hydraulic actuator 14a of the attachment 14 to increase the pressure of the confined oil in the attachment circuit 13.
Works to limit the circuit pressure in the attachment circuit 13 to the relief pressure set by the spring.

The line relief valve 19 also has a make-up function, and when the spool 18 is in the neutral position, an external force acts on the hydraulic actuator 14a to cause the hydraulic actuator 1 to operate.
When the piston of 4a moves, the pressure oil corresponding to the movement of this piston is not supplied, so that the inside of the hydraulic actuator 14a becomes a vacuum.

When the vacuum is generated, the make-up function is activated to supply the return oil to the tank 17 to the vacuum generating portion of the hydraulic actuator 14a to eliminate the vacuum.

The electric relief valve 15 is disclosed in Japanese Patent No. 306951.
This will be described with reference to FIG. 7. The main poppet 22 is slidably provided inside the valve body 21, and the main poppet 22 is pressed against the main seat 24 by the spring 23. Further, the seat body 26 is fixed by the adapter 25 screwed into the valve body 21, facing the pilot seat 27 of the seat body 26,
A pilot poppet 28 slidably fitted in an adapter 25 is provided so as to be able to move forward and backward, and a solenoid 29 for axially moving the pilot poppet 28 is attached to the valve body 21.

As shown in FIG. 8, this solenoid 29
Is a rightward thrust generated in proportion to the current value supplied to the built-in solenoid coil (not shown).
And the movable portion 30 presses the pilot poppet 28 against the pilot seat 27.

The inlet port 31 provided at the tip of the valve body 21 is an orifice 32 provided in the main poppet 22.
Is connected to the spring chamber 33 via the
Is an orifice 34 provided in the seat body 26, a pilot seat 27 opened by the retracted pilot poppet 28, a through hole 35 provided in the adapter 25, and an adapter 25.
Is communicated with the inside of the tank 17 through a passage 36 provided along the outer peripheral surface of the valve and a through hole 37 provided in the valve body 21.

The valve body 21 is provided with a tank port 38 which communicates with the inlet port 31 when the main poppet 22 is separated from the main seat 24. Also the main poppet
A filter 39 is provided on the inlet 22 of the orifice 32.

Next, the operating principle of the conventional electric relief valve 15 will be described.

First, the solenoid 29 causes the tip of the pilot poppet 28 to move toward the seat 26 with a thrust force F ₁ proportional to the current value I.
The pilot seat 27 is pressed. At this time, the solenoid thrust F ₁ and the current value I are in the proportional relationship shown in FIG.

(Formula 1) F ₁ = k ₁ · I where k ₁ is a proportional constant.

The pressure receiving area at the tip of the pilot poppet 28 seated on the pilot seat 27 of the seat body 26 is Ap, and the pressure receiving area upstream and downstream of the orifice 32 of the main poppet 22 are both Am. . The preset load of the spring 23 is F ₂ .

When the inlet pressure Pin of the inlet port 31 is lower than F ₁ / Ap, the pilot seat 27 is closed by the pilot poppet 28, so the inlet pressure Pin and the pressure in the spring chamber 33 are balanced. ing. For this reason, the main poppet 22 is attached to the main seat 24 by the spring 23.
The inlet port 31 and the tank port 38 are blocked by the main poppet 22.

Next, when the inlet pressure Pin rises and (Equation 2) becomes Pin = F ₁ / Ap, the pilot poppet 28 is pushed to the right,
The pilot seat 27 opens, the orifice 32 from the inlet port 31, the spring chamber 33, the orifice 34 of the seat body 26,
The pilot flow rate Q ₁ flows into the tank 17 through the pilot seat 27, the through hole 35, the passage 36, and the through hole 37.

Here, for convenience, assuming that the tank pressure = 0,
Since the pilot flow rate Q ₁ flows through the orifice 32 built in the main poppet 22, a differential pressure ΔP across the orifice 32 expressed by the following mathematical formula 3 is generated.

(Formula 3) Q ₁ = k ₂ · A ₃ · (ΔP) ^1/2 where k ₂ is a constant and A ₃ is the opening cross-sectional area of the orifice 32.

Then, the preset load F of the spring 23
_{On the} other hand, when F ₂ ≦ Am · ΔP, the main poppet 22 is pushed to the right, and the inlet port 31 and the tank port are
38 is conducted, and Equation 2 is maintained.

That is, according to the formulas 1 and 2, the electric relief valve 15 can arbitrarily set the inlet pressure Pin by the current value I, and in the case where the electric check valve 16 is in the communicating state in FIG. The relief pressure can be changed as desired.

When the current value I supplied to the solenoid coil of the solenoid 29 is set to 0, the inlet pressure Pin also becomes 0. Therefore, when the electric check valve 16 is in the open state, the attachment circuit 13 is in the unload state. Controlled.

As described above, the electric relief valve 15 is composed of the main portion and the pilot portion, and the pilot poppet 28 is
The solenoid 29 presses against the pilot seat 27 instead of the spring.

Therefore, when no current is supplied to the solenoid coil of the solenoid 29, the pilot poppet
Since the thrust force that pushes the 28 onto the pilot seat 27 cannot be obtained, the pilot poppet 28 opens due to the pressure acting on the tip of the pilot poppet 28, and the spring chamber on the opposite side of the main poppet 22 from the inlet port 31 through the orifice 32.
Pilot pressure introduced in 33 (so-called main poppet
The back pressure of 22) decreases, the main poppet 22 opens, and the system pressure acting on the inlet port 31 is unloaded.

On the other hand, when a current is supplied to the solenoid coil of the solenoid 29, the pilot poppet 28 closes the pilot passage, and the back pressure of the spring chamber 33 rises, so that the main poppet 22 closes and the system pressure rises. Then, the force generated by the pilot pressure that acts on the seat area of the pilot poppet 28 seated on the pilot seat 27 and the force of the solenoid 29 are balanced so as to be equal.

When the thrust of the solenoid 29 is applied as shown in FIG. 8, the system pressure acting on the inlet port 31 also rises in response to the electric current.

[0029]

In such a conventional electric relief valve 15, when an excessive surge current is generated in the electric input to the solenoid 29, the thrust of the solenoid 29 also increases in accordance with the current, so that the relief pressure is reduced. The pressure may rise abnormally.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric relief valve capable of preventing an abnormal rise in relief pressure even when an excessive current is input. .

[0031]

According to the invention described in claim 1, a main valve openably and closably provided between a passage to be pressure controlled and a tank, and a passage from the passage to be pressure controlled A pilot valve for controlling the pilot pressure introduced to the opposite side of the main valve, a solenoid having a movable part for driving the pilot valve in the pilot pressure closing direction when energized, and a movable part of the solenoid and the pilot valve. It is an electric relief valve equipped with a spring interposed between the solenoid and a stroke limiter that regulates the movement stroke of the movable part of the solenoid, and even if an excessive current such as surge current is input to the solenoid, the stroke limiter will Since the moving stroke of the movable part is restricted, the force acting on the pilot valve from the movable part of the solenoid via the spring is restricted. , The force for driving the pilot valve to the pilot pressure closed write direction is restricted, the relief pressure passages this force is pressure controlled object to be controlled by the main valve in case of excessive can be prevented risk of abnormally elevated.

According to a second aspect of the present invention, in the stroke limiter according to the first aspect, one engaging portion fixed to the movable portion of the solenoid so as to be movable and adjustable, and one engaging portion having a predetermined stroke movement. Is an electric relief valve having one engaging portion and the other engaging portion provided at an engageable position by means of which one engaging portion is movably fixed to the movable portion of the solenoid. Since the one engaging portion and the other engaging portion are engaged with each other, the moving stroke of the movable portion can be arbitrarily adjusted.

According to a third aspect of the present invention, the stroke limiter according to the first aspect includes one engaging portion provided on a member that compresses the spring by being pressed by the movable portion of the solenoid, and one engaging portion. An electric relief valve having one engaging portion and the other engaging portion provided at an engageable position by a predetermined stroke movement of the portion, the member being pressed by the movable portion of the solenoid to compress the spring; Since the one engaging portion and the other engaging portion of the stroke limiter are provided at positions where they can be engaged with this member, the existing solenoid can be used as it is.

[0034]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to one embodiment shown in FIGS. 1 to 4 and another embodiment shown in FIG. The same parts as those of the conventional electric relief valve shown in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows an electric relief valve 15 having a mechanical function of suppressing the pressure below a certain value even if an excessive current such as a surge current is inputted.

In this electric relief valve 15, the valve body 21
A main poppet 22 as a main valve that is openably and closably provided between the passage 41 to be pressure controlled and the tank 17 inside the
And a spring chamber on the opposite side of the main poppet 22 to the passage 41 from the passage 41 to be pressure controlled through the orifice 32.
A configuration in which a pilot poppet 28 as a pilot valve that controls the pilot pressure introduced in 33 is incorporated, and a configuration including a solenoid 29 that drives this pilot poppet 28 in the pilot pressure closing direction are shown in FIG. It is similar to the conventional one.

Further, the main body 42 of the solenoid 29 and the valve main body
A hollow spacer 44 is interposed between the flange portion 43 of the valve 21 and the body portion 42 of the solenoid 29 and the spacer 44 are coupled by a bolt (not shown), and the spacer 44 and the flange portion 43 of the valve body 21. Are connected by another bolt (not shown).

Between the movable portion 30 of the solenoid 29 and the pilot poppet 28, a coil-shaped spring 47 having an appropriate spring constant is interposed. This spring 47
One spring receiving body 48 as a member for compressing the spring 47 abutting on the movable portion 30 of the solenoid 29 is fitted to one end of the spring 47, and the other end of the spring 47 is
The other spring receiving body 49 that is in contact with the pilot poppet 28 is fitted.

Inside the solenoid 29, a stroke limiter 51 for regulating the movement stroke of the movable portion 30 is built in.

The solenoid 29 has a solenoid coil 52 inside the main body 42, an armature 53 that is moved by an axial thrust corresponding to the amount of energization when energizing the solenoid coil 52, and is integrated with the armature 53. The shaft-shaped movable portion 30 is provided, and the movable portion 30 is driven in a direction of protruding from the main body portion 42 when the solenoid coil 52 is energized.

On the other hand, the stroke limiter 51 of the solenoid 29 is a movable part in the inner space of the cover 54, which is formed separately from the main body 42 and is joined by a bolt (not shown).
One of the engaging parts 55 is fitted to 30 so as to be movable and adjusted, and the screw 56
It is fixed to the movable part 30 by.

Further, an engagement plate 57 is clamped and fixed between the main body 42 and the cover 54. A hole through which the movable portion 30 penetrates is provided in the center of the engaging plate 57, and the other engaging portion 58 is provided around the hole, and one of the engaging portions 55 moves by a predetermined stroke st. The engaging portion 55 can be locked by the other engaging portion 58.

Next, the function and effect of this embodiment will be described.

When current is not supplied to the solenoid coil 52 of the solenoid 29, the thrust force for pressing the pilot poppet 28 against the pilot seat 27 cannot be obtained, so that as shown in FIG. It is opened by the pressure acting on the
26 orifices 34, pilot seat 27, through holes 35, passages
Tank 17 through a series of pilot passages 36 and 37
Since oil flows out, the pilot pressure (so-called back pressure) introduced from the inlet port 31 through the orifice 32 into the spring chamber 33 on the opposite side of the main poppet 22 decreases, and the main poppet 22 separates from the main seat 24. Therefore, the system pressure in passage 41 acting on inlet port 31 is
To unload into tank 17.

On the other hand, the solenoid coil 52 of the solenoid 29
When a current is supplied to the movable part 30, the movable part 30 moves to the right as shown in FIG. 3 and strokes while compressing the spring 47 to a position where a pressing force corresponding to the thrust generated according to the current value is obtained. Until the one engaging portion 55 engages with the other engaging portion 58, the same thrust as the thrust generated by the solenoid 29 is applied to the pilot poppet 28.

At this time, since the pilot poppet 28 closes the pilot passage with a force corresponding to the thrust generated by the solenoid 29, the back pressure of the spring chamber 33 rises and the main poppet 22 operates in the closing direction. Therefore, the system pressure in the passage 41 rises and balances to a pressure such that the force generated in the seat area of the pilot poppet 28 and the thrust of the solenoid 29 become equal. Let the system pressure in the passage 41 be the relief pressure.

Therefore, as shown by the inclined portion in FIG. 4, the relief pressure in the passage 41 rises in accordance with the current value as in the conventional electric relief valve.

As shown in FIG. 3, the moving stroke of the movable portion 30 reaches the predetermined stroke st regulated by the stroke limiter 51, and the one engaging portion 55 and the other engaging portion 55 are moved.
When 58 is engaged and movement of the movable portion 30 is restricted, even if the current value supplied to the solenoid coil 52 rises, the thrust force applied to the spring 47 does not increase beyond a certain value. . Then, a constant thrust is held by the spring 47.

Therefore, in this state, even if an excessive surge current is input to the solenoid coil 52, the movable portion 30 cannot move, so the thrust applied to the pilot poppet 28 is the spring in the compressed state shown in FIG. It is limited to a certain value given by 47 and does not rise any further.

Therefore, as shown in the horizontal portion of FIG. 4, the relief pressure does not rise above a certain value, and the surge cut function can be obtained.

That is, even if a surge current is input to the solenoid coil 52 of the solenoid 29, the stroke limiter
Since 51 restricts the moving stroke of the movable part 30 of the solenoid 29, the force applied to the pilot poppet 28 from the movable part 30 of the solenoid 29 via the spring 47 is restricted,
The force that drives the pilot poppet 28 in the pilot pressure closing direction is also regulated. If this force is excessive, the main poppet
Although the relief pressure of the passage 41 controlled by 22 also rises abnormally, the fear can be prevented.

According to the embodiment shown in FIG. 1,
Remove the cover 54 from the main body 42 of the solenoid 29, and
And the fixed position of the one engaging portion 55 with respect to the movable portion 30 is moved and adjusted, the moving stroke st of the movable portion 30 regulated by the stroke limiter 51 can be arbitrarily adjusted.

Next, FIG. 5 shows another embodiment.

A stroke limiter 61 for restricting the moving stroke of the movable portion 30 of the solenoid 29 is provided between the one spring receiver 48 and the spacer 44.

That is, the stroke limiter 61 is
The spring 47 is pressed by the movable part 30 of the solenoid 29.
To one spring receiver 48 as a member for compressing
One engagement portion 62 formed in a flange shape is provided, and the spacer 44 has a predetermined stroke of the one engagement portion 62.
The other engaging portion 63 is provided at a position at which the engaging portion 62 can be engaged by the movement of st.

In short, the spring receiving body is larger than the inner diameter of the spring fitting hole 64 formed in the center of the spacer 44.
By forming the outer diameter of 48 to be large, the one engagement portion 62 and the other engagement portion 63 are engaged by the movement of one engagement portion 62 by the predetermined stroke st.

Thus, in the electric relief valve 15,
The movable part 30 of the solenoid 29 and the pilot poppet 28 are connected by a spring 47 having an appropriate spring constant, and the thrust of the solenoid 29 is applied to the pilot poppet 28 via the spring 47. Further, a stroke limiter 61 is provided on a member driven by the movable portion 30 of the solenoid 29, and the movable portion 30 of the solenoid 29 is restricted so as not to move more than a predetermined stroke st.

Since the valve structure of the electric relief valve 15 shown in FIG. 5 is the same as that shown in FIG. 1, the same parts are designated by the same reference numerals and the description thereof will be omitted.

Next, the operation of the embodiment shown in FIG. 5 will be described.

The current value supplied to the solenoid coil of the solenoid 29 rises, the moving stroke of the movable portion 30 of the solenoid 29 reaches the predetermined stroke st regulated by the stroke limiter 61, and one engaging portion 62 moves to the other. When engaged with the engaging portion 63, even if the current value supplied to the solenoid coil further increases, the thrust force applied to the spring 47 does not increase beyond a certain value. Then, a constant thrust is held by the spring 47.

Therefore, even if an excessive surge current is input to the solenoid coil of the solenoid 29 and an excessive thrust is generated in the solenoid 29, the thrust applied to the pilot poppet 28 does not rise above a certain value.

Therefore, as shown in the horizontal portion of FIG. 4, the relief pressure does not rise above a certain value, and the surge cut function can be obtained.

In other words, even if the surge current is input to the solenoid 29, the stroke limiter 61 causes the solenoid 29 to operate.
Since the movement stroke of the movable portion 30 of the solenoid 29 is regulated, the force acting on the pilot poppet 28 from the movable portion 30 of the solenoid 29 via the spring 47 is regulated, and the force for driving the pilot poppet 28 in the pilot pressure closing direction is also regulated. Is
If this force is excessively large, the relief pressure of the passage 41, which is the pressure control target controlled by the main poppet 22, also abnormally rises, but this can be prevented.

According to the embodiment shown in FIG. 5,
The spring 47 is pressed by the movable part 30 of the solenoid 29.
One of the spring receiving body 48 for compressing, and the facing position on the spacer 44 side engageable with the spring receiving body 48,
Since the one engaging portion 62 and the other engaging portion 63 of the stroke limiter 61 are provided, the existing solenoid 29 can be used as it is.

[0065]

According to the first aspect of the present invention, even if an excessive current, for example, a surge current is input to the solenoid, the stroke limiter regulates the stroke of the movable portion of the solenoid. The force acting on the pilot poppet via the valve is regulated, the force driving the pilot poppet in the pilot pressure closing direction is also regulated, and when this force is excessive, the relief of the passage to be pressure controlled controlled by the main valve is controlled. It is possible to prevent the pressure from rising abnormally.

According to the second aspect of the present invention, the one engaging portion is movably fixed to the movable portion of the solenoid, and the one engaging portion and the other engaging portion are engaged with each other. The moving stroke of the movable part can be adjusted arbitrarily.

According to the third aspect of the present invention, one member of the stroke limiter and the other member of the stroke limiter are provided at a member pressed by the movable portion of the solenoid to compress the spring and at a position at which the spring is engageable. Since it is provided, the existing solenoid can be used as it is.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an electric relief valve according to the present invention.

FIG. 2 is a sectional view of the electric relief valve of the above when an unloading operation is performed.

FIG. 3 is a sectional view of the electric relief valve when the stroke limiter is operating.

FIG. 4 is a characteristic diagram showing current-relief pressure characteristics of the electric relief valve of the above.

FIG. 5 is a sectional view showing another embodiment of the electric relief valve according to the present invention.

FIG. 6 is a circuit diagram showing a hydraulic circuit in which an electric relief valve is incorporated.

FIG. 7 is a cross-sectional view showing a conventional electric relief valve.

FIG. 8 is a characteristic diagram showing current-thrust characteristics of a solenoid used in a conventional electric relief valve.

[Explanation of symbols]

17 Tank 22 Main poppet as a main valve 28 Pilot poppet as a pilot valve 29 Solenoid 30 Moving part 41 Passage 47 Spring 48 One spring receiver as a member for compressing a spring 51 Stroke limiter 55 One engaging part 58 of the other Engagement part 61 Stroke limiter 62 One engagement part 63 Other engagement part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hitoshi Iwasaki             4-10-1, Yoga, Setagaya-ku, Tokyo             Within Mitsubishi Corporation (72) Inventor Yoshio Aso             2337 Inami, Inami-cho, Kako-gun, Hyogo Stock Association             Shamisen Machinery Works Tsuchiyama Factory (72) Inventor Masahiko Ueno             2337 Inami, Inami-cho, Kako-gun, Hyogo Stock Association             Shamisen Machinery Works Tsuchiyama Factory F-term (reference) 3H056 AA02 BB24 CA02 CB02 CD06                       CE01 EE06 GG04 GG12                 3H059 AA06 AA17 BB06 CD05 CE04                       CF14 EE01 FF03 FF14

Claims (3)

[Claims] 1. A main valve openably and closably provided between a passage to be pressure controlled and a tank, and a pilot pressure introduced from the passage to be pressure controlled to the opposite side of the main valve with respect to this passage. Control solenoid, a solenoid having a movable part that drives the pilot valve in the pilot pressure closing direction when the pilot valve is energized, a spring interposed between the movable part of the solenoid and the pilot valve, and movement of the movable part of the solenoid. An electric relief valve comprising a stroke limiter for regulating a stroke. 2. A stroke limiter is provided at one engagement portion fixed to a movable portion of a solenoid so as to be movable and adjustable, and at a position where one engagement portion can be engaged by a predetermined stroke movement of the one engagement portion. The electric relief valve according to claim 1, further comprising the other engaging portion provided. 3. The stroke limiter engages with one engagement portion provided on a member that is pressed by a movable portion of a solenoid to compress a spring, and one engagement portion by a predetermined stroke movement of the one engagement portion. The electric relief valve according to claim 1, further comprising another engagement portion provided at a position where the electric relief valve can be fitted.