JPS63199902A - Control circuit for hydraulic motor - Google Patents

Abstract

PURPOSE:To control a hydraulic motor according to its working situation by composing a brake circuit of a relief valve whose pressure rise characteristics against time changes and connecting the pressure chamber of the relief valve to the output side of an operating valve. CONSTITUTION:A relief valve R1 provided in a brake circuit is composed of a cylinder body 16 having a main valve R15, a spring R17 which presses the main valve R15, a piston R19 which presses the spring R17 and a spring R18 which has stronger pressing force than the spring R17 and presses the piston R19, and the pressure chamber R11 of the relief valve R1 is connected to the outlet of a pilot valve 10. Owing to the above arrangement, when the speed of a hydraulic motor M is made to change by an operating valve 11, the brake characteristics of the brake circuit can be changed so as to suit the speed of the hydraulic motor M, and thereby the hydraulic motor M is controlled according to its working situation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control circuit for a hydraulic motor used in a traveling device, a swing device, etc. of a hydraulic excavator.

[Conventional technology]

A control circuit for a hydraulic motor, etc. for a hydraulic excavator running device is shown in FIG. 4(a) (prior art circuit diagram created from JP-A No. 61-49175 and Utility Model Application No. 59-58201). There is.

In FIG. 4(a), when the circuit 7 is connected to the pump and the circuit 8 is connected to the tank, the counterbalance valve 3 is switched to the switching position 3a, and the hydraulic motor M is supplied with pressure from the main circuit 1. Oil is supplied and discharged from the main circuit 2. Therefore, the hydraulic motor M rotates in the direction of the arrow Ma, causing the hydraulic excavator to travel.

When the circuit 7.8 is connected to the tank while the hydraulic excavator is running, the counterbalance valve 3 returns to the neutral position 3C,
Main circuits 1 and 2 are connected to circuits 7 and 8 via check valves in neutral position f3c. Therefore, the supply of pressure oil to the hydraulic motor M is stopped, but since the hydraulic motor M is rotated by inertia force, it sucks oil from the main circuit 1 and the main circuit 2
Discharge to.

The oil pressure in the main circuit 2 is the pressure of the relief valve S in the brake circuit 4.
R2 is controlled as shown in FIG. 4(b). This relief valve SR2 (SRI and SRI have the same configuration) is the same as that disclosed in Utility Model Application No. 59-58201. As shown in FIG. 4(b), the characteristics of this relief valve SR2 are such that when the oil pressure in the main circuit 2 begins to rise,
For time t7, the oil pressure is maintained at Pl, and thereafter maintained at oil pressure P2, which is higher than oil pressure P1.

In the hydraulic excavator, when a brake corresponding to the oil pressure P1 is applied to the hydraulic motor M of the traveling device, the brake is applied to an extent that does not cause a shock. And this brake is t
The hydraulic excavator is stopped by being held for three hours. Note that when the hydraulic excavator is started, the relief valve SR1 controls the oil pressure of the main circuit 1 according to a pressure increase characteristic curve of the oil pressure as shown in FIG. 4(b). That is, by maintaining the main circuit oil pressure at oil pressure P1 for t3 hours, mechanical play between the hydraulic motor M and the traveling device (play in the reducer, etc.) is eliminated, and when the oil pressure reaches P2, the hydraulic excavator is activated.

[Problem that the invention seeks to solve]

The brake circuit 4 has a relief valve SR2 connected to the main circuit 2.
By controlling the hydraulic pressure at low pressure P''1?1+time, the cause of impact is eliminated and the hydraulic excavator is stopped without causing impact.

However, recently, the speed of the hydraulic motor M has been controlled to an arbitrary speed between high and low speeds by controlling the swash plate M1 to a high speed position and a low speed position using a cylinder M2, as shown in FIG. 4(a). This cylinder M2 is configured to have a pilot valve 1.
The pilot valve 10 is connected to the high pressure side of the main circuit 1.degree. 2 via the pilot valve 10.

In this device, when the operating valve 11 is operated to the switching position 11a, the pilot valve 10 is switched to the switching position 10a, and the hydraulic pressure on the high pressure side of the main circuit is transferred from the circuit 5 through the pilot valve 10. , cylinder M2ε acts, and swash plate M
By changing the inclination angle of 1, the output of the hydraulic motor M can be changed to
The torque is low.

When the operating valve 11 is returned to the position shown in FIG. 4(a), the cylinder M2 is connected to the tank and the hydraulic motor M outputs low speed and high torque.

The high-speed operation of the hydraulic motor M described above is mainly used for moving the hydraulic excavator, and the low-speed operation is used for work. Therefore, the characteristic required during low-speed operation is accurate position control function.

In other words, it is necessary to improve responsiveness to operations by the operator. On the other hand, the characteristics required during high-speed operation are:
It is necessary to stop the vehicle with as little impact as possible. In this respect, conventional control circuits cannot cope with such changes in the speed of the hydraulic motor.

[Means for solving problems]

The technical means of the present invention for solving the above problems are as follows:
A brake circuit having a relief valve is provided in the main circuit between the hydraulic motor and the counterbalance valve, and the hydraulic motor is controlled to any speed, either high or low, by pilot hydraulic pressure controlled by an operating valve. In the control circuit for a hydraulic motor, the brake circuit includes a pressure chamber and includes a relief valve whose pressure increase characteristics change over time by supplying and discharging pressure oil to the pressure chamber, The pressure chamber of the valve is connected to the output side of an operating valve that controls high and low speeds of the hydraulic motor.

[Effect]

The present invention having the above-mentioned technical means, when the speed of the hydraulic motor is changed by the operation valve, simultaneously changes the speed of the pilot hydraulic motor acting on the hydraulic motor and changes the braking characteristics of the brake circuit to the speed of the hydraulic motor. Therefore, the hydraulic motor can be controlled in accordance with its operating condition.

〔Example〕

Hereinafter, in describing the embodiments, the same reference numerals will be used for parts similar to those in the prior art, and the description thereof will be omitted.

In FIG. 1, 4A is a brake circuit according to an embodiment of the present invention, which includes a relief valve R1 that controls the main circuit 1 pressure and a relief valve R2 that controls the main circuit 2 pressure.

This relief valve RIR2 has pressure chambers R11°R21 that change its braking characteristics, and these pressure chambers R11,
R21 is connected to the pilot circuit P at the outlet of the pilot valve 10.
Connect via R.

The relief valve R1 described above has the configuration shown in FIG. 2(a). (In addition, since the relief valve R2 is also the same, only the relief valve R1 will be explained.) In FIG. A cylindrical body R16 having a communicating slot R13 and a main valve R15 that opens and closes between this day R13 and the discharge passage R14 is fixed, and a spring that presses the main valve R15 is installed in this cylindrical body R16. R17 is provided.This blade R
17 is slidably provided on the main body R12 and supported by a piston R19 that is pressed by a spring R18 set with a stronger pressing force than the spring R17. This piston R1
9 moves to the right by 1 when pressure oil is supplied to the pressure chamber R11. At this time, the pressing force of spring R17 decreases accordingly. Further, a piston R15a is slidably fitted into the main valve R15. This piston R15a is connected to a stopper R12 fixed to the main body R12.
It stops when it comes into contact with a, and the main valve R is inside the main valve R15.
A pressure chamber R15c is formed which is connected to the main circuit 1 through 15 throttles R15b. Note that the pressure receiving area S15 of this piston R15a is smaller than the area S13 of the mouth R13. Also, i2 is the piston R15a and the stopper R12.
The spring chamber R17a, which is spaced from the spring R17a and provided with the spring R17, is connected to the main circuit 2.

Brake circuit 4A having the above-mentioned relief valve RIR2
The two types of braking forces shown in FIG. 2(b) are applied to the hydraulic motor M.

[Operation of the first embodiment] When the operation valve 11 is not operated, as shown in FIG.
Since the cylinder M2 is connected to the tank via the pilot valve 10, the hydraulic motor M rotates at a low speed. Moreover, since no pressure oil is acting on the pressure chambers R11, R21 of the relief valves R1, R2 of the brake circuit 4A, the pistons R19, R29 are pressed by the springs R18, R28, and as shown in FIG. 2(a). in position. Therefore, spring R1
7°R28 is set to a high pressing force.

Assume that in the above state, when pressure oil is supplied from the main circuit 2 to the hydraulic motor M and the hydraulic motor M is rotating in the force direction of the arrow Mb, the supply of pressure oil to the hydraulic motor M is stopped.

Then, the hydraulic motor M moves in the direction of arrow Mb due to its inertia force.
It is driven in the force direction, sucks oil from the main circuit 2, and discharges pressure oil to the main circuit 1.

When the oil pressure of the main circuit 1 acts on the relief valve R1, the pressure oil flows into the pressure chamber R15c via the throttle R15b of the main valve 15. Therefore, the piston R15a moves to the right. Until this piston R15a hits the stopper R12a, the oil pressure P L (kg/cn) of the main circuit 1 is
13 pressure-receiving area 513 (cfl) multiplied by the oil pressure of the main circuit 1, and the pressing force F17 (kg
), the curve (b) in FIG.
i (kg/cffl). (P1=F17/
313) Time controlled by this oil pressure P1 1. is the time required for the piston R15 to hit the stopper R12. Therefore, a braking force corresponding to the pressure PI acts on the hydraulic motor M.

In this way, when the piston R15a of the main valve R15 hits the stopper R12a, the pressure receiving area of the main valve R15 becomes the value obtained by subtracting the pressure receiving area S15 from the pressure receiving area S13. Therefore, it is controlled by the oil pressure P2 of the main circuit 1. (P2=F1
7/513-315) As mentioned above, when the oil pressure in the main circuit 1 is controlled to pi (kg/d), a braking force acts on the hydraulic motor M, but this braking force is When the hydraulic excavator is running at low speed, the braking force is such that it does not cause an impact, and the time t is long enough to absorb the inertial force of the hydraulic excavator when it is running at low speed. Therefore, the hydraulic excavator cuts off the supply of pressure oil to the hydraulic motor M and stops approximately after t1 time.

Next, when the control valve 11 is operated to the switching position 11a, pilot pressure oil is supplied to the cylinder M2, the hydraulic motor M rotates at high speed, and the hydraulic excavator also runs at high pressure.

At this time, the pressure chambers R11, R2 of the relief valves R1, R2
1 is also supplied with pressure oil.

When pressure oil is supplied to the pressure chamber R11 of the relief valve R2,
Since the pistons R19 and R29 move by l against the springs R18 and R2B, the pressing forces of the springs R17 and R27 also change from F17 to a weak value of F17a. Therefore,
The oil pressures P1' and P2' of the main circuit 1 are as follows, as shown in the curve (in FIG. 2).

P1'=F17a/313 P2'=F17'/513-315 Since F17a<F17, the differential pressure across the throttle hole R15b of the main valve R15 also decreases, so the main circuit 1 is maintained at pressure PI'. The time t2 is also the same as the time 1. becomes longer.

When the traveling speed of the hydraulic excavator is increased, the characteristic curve of the brake circuit 4A becomes as shown in the curve in FIG. 2(b). Therefore, the braking force of the hydraulic pressure PI' acts on the hydraulic excavator for a period of t2. However, brake circuit 4
As shown in curve (a) of Fig. 2 ('b), the characteristic of A is 1. when the hydraulic excavator is running at low speed. It is set to stop in time. Therefore, when running at high speed, if the characteristics of the brake circuit 4A are reduced as shown in curve (b), the hydraulic excavator will not stop in time 1g, but will require time t for the brake force of hydraulic pressure P2' to act. shall be.

During this time t, the braking force changes from pressure PI to pressure P2 in accordance with the change. The pressure difference at this time is PS'
Then, the braking force changes by an amount corresponding to this pressure difference. This oil pressure difference PS' is determined to an extent that does not cause an impact on the hydraulic excavator. Therefore, it takes a longer time to stop a hydraulic excavator when it is running at high speed than when it is running at low speed.

Next, relief valves R1 and R2 used in the brake circuit 4A
A second embodiment of the invention will be explained with reference to FIG. 3 (al (b)).
For the parts having the same configuration as 2, the numbers added to the reference RA are the same, and the explanation thereof will be omitted.

This second embodiment and the first embodiment illustrated in FIG. 2(a)
The difference from the embodiment shown in FIG. 2(a) is that the embodiment shown in FIG.
While the characteristics of the main valve R15 are changed by changing the pressing force of the spring that presses the main valve R15, in this second embodiment, the pressure in the pressure chamber RA15c of the main valve RA15 is guided to the damper part RAD. By changing the damper characteristics of the damper section, the characteristics of the brake circuit are changed.

The above configuration relief valve RAI has the following main valve RA15:
The pipe RA15d is slidably inserted into the pipe RA15d, and a damper portion RAD is provided behind the pipe RA15d. This damper part RAD connects the inner hole RAD 13 of the main body RA12 to two chambers RADI.
4. Split into RADI 5. This chamber RAD15 is connected to the pressure chamber RA of the main valve RA15 via a pipe RAD15d.
Connect to D15C. Further, the room RAD14 is the first
It is connected to the spring chamber RAD17a to which the main circuit 2 is connected via the aperture RAD16a and the second aperture RAD16b.

Note that the hole RAD17 is closed by the piston RAD l1. The second throttle 16b described above is configured to be opened and closed by a small piston RAD18, and this small piston RAD18 is operated by the hydraulic pressure of the pilot circuit PJ to close the throttle RAD16b.

[Operation of the Second Embodiment] As described above, it is assumed that the supply and discharge of pressure oil to the hydraulic motor M is cut off, and the hydraulic pressure due to the pumping action of the hydraulic motor M acts on the main circuit 1.

The oil pressure of this main circuit 1 is the throttle RA15b of the main valve RA15.
via pressure chamber RA15C, pipe RA15d, and chamber R.
Acts on AD15. At this time, the chamber RAD14 is
Since it communicates with the spring chamber RAD17a via AD17, the piston RADII moves lightly. Therefore, surge pressure in the main circuit 1 can be eliminated.

When the piston RADII of the damper portion RAD closes the hole RAD17, the chamber RAD14 closes the first. 2nd aperture RAD
It is connected to the spring chamber RA17a only through 16a and 16b. Therefore, the pressure in the pressure chamber RAI5c (7) is controlled to a value that corresponds to the opening area of these two apertures RAD16a and RAD16b. For this reason, main valve RA
15 controls the oil pressure Pi of the main circuit as follows.

P1=R315/R3I 3XPa+F17/RS 1
3-・-・・−−−−−−(1) Pl−・−Main circuit 1
Pressure 5R13-・Area Pa of mouth RA13-・Pressure 5R15 of pressure chamber RA15C--Area F17 of pressure chamber RA15C--Pushing force of spring RA17°Therefore, the oil pressure P1 of the main circuit 1 is the same as that of the damper part RAD. During operation, as shown in the curve (al) of FIG. 3(b), the pressure is maintained at P1, and the time 1.
5 and the throttle RA15b of the main valve RA15.

Next, if the piston RADII moves to the right end,
Since the oil pressure in the pressure chamber RA15C of the main valve RA15 and the oil pressure in the main circuit 1 are equal, the oil pressure in the main circuit 1 is as shown in Fig. 3(b).
As shown in curve (a), the value of R2 is controlled.

P 2-F 17/R313-R315- (2) In the above action, when pressure oil is supplied from the pilot circuit PR and the second throttle RAD 16 b is closed, the oil discharged from the chamber RAD14 of the damper portion RAD is the second aperture RAD
16a, the value of Pa in the above-mentioned equation (1) becomes Pa', which is higher than that.

Therefore, the pressure in the main circuit 1 is also controlled to a value of Pl' which is higher than Pl, as shown in the curve in FIG.

In this second embodiment, as described above, the pilot circuit p
By applying the hydraulic pressure of z to the small piston RAD l 8 and narrowing the aperture opening area of the damper portion, the characteristics shown in Figure 3 (track 1 (a) and (b) of BL) are obtained.

The above-mentioned relief valve RA1. According to the brake circuit using RA2, when the hydraulic excavator is running at a low speed, the hydraulic pressure from the operating valve 11 is not acting, so the small piston RAD18 is not acted on by the hydraulic pressure. For this reason, ζ room RAD
14 is the first. It is discharged into the tank via the second throttle. Therefore, the characteristics of the brake circuit are as shown by curve (a) in FIG. 3(b). Then, when pressure oil is no longer supplied to the hydraulic motor M, the main circuit 1 is controlled to the hydraulic pressure P1, so a braking force corresponding to the hydraulic pressure P1 acts on the hydraulic motor. When this braking force is applied for a period of time 1, the inertia force generated by the low-speed running of the hydraulic excavator is almost absorbed, and the hydraulic excavator comes to a stop. (Similar to the case described above, when running at low speed, the time required for stopping is shortened because it is in the working state.) Next, in order to make the hydraulic excavator run at high speed, the rotation speed of the hydraulic motor is increased. Since the small piston RAD18 closes the second throttle RAD16b, the characteristics of the brake circuit become as shown in the curve (bl) in FIG. 3(b). Then, pressure oil is no longer supplied to the hydraulic motor M. and,
Since the oil pressure of the main circuit 1 is controlled to P1', the oil pressure P1
′ acts on the hydraulic motor M. Since the hydraulic excavator is traveling at high speed, its inertia increases, and it does not stop within the time 1. In order to stop, it requires time t3 during which the hydraulic pressure in the main circuit 1 is controlled to R2. During this time t3, when the hydraulic pressure is controlled from P1 to R2, the brake force changes by an amount corresponding to the pressure difference PS'. This pressure difference PS' is determined to a level that does not cause an impact on the hydraulic excavator. Therefore, it takes a longer time to stop hydraulic pressure when traveling at high speeds than when driving at low speeds.

〔Effect of the invention〕

As explained above, the control circuit according to the present invention is used to control a hydraulic motor that can be controlled to any speed, high or low, using pilot oil pressure controlled by an operation valve, and the brake characteristics of the brake circuit are controlled by the pilot oil pressure. The characteristics are changed using hydraulic pressure to correspond to the speed of the hydraulic motor. Therefore, for machines such as hydraulic excavators, where the content of the work is almost determined according to the operating conditions, it is possible to change the brake characteristics according to the working conditions to match the working conditions. The braking characteristics can be obtained automatically in response to the selection of the speed of the hydraulic motor. Therefore, it has the effect of facilitating operations for the operator.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. 2(a) is a sectional view of the relief valve used in the brake circuit 4 of FIG. 1, FIG. 2(b) is a characteristic curve diagram thereof, and FIG. 3(a) is a sectional view of the relief valve used in the brake circuit 4 of FIG. 3(b) is a sectional view of the second embodiment of the relief valve used in circuit 4, FIG. 3(b) is its characteristic curve diagram, FIG. Characteristic curve diagram of the brake circuit 4 in Figure 4(a). 1.2--Main circuit 3--Counter balance valve 4.4
A-Brake circuit 7. L--Circuit 10--Pilot valve 11...Operating valve R1, R2, RAI, RA2--Relief valve R11, R2L--Pressure chamber R15--Main valve RA15--Main valve RAI)--Damper section application People Japan Air Brake Co., Ltd. Figure 1 Figure 211 (b) Figure 4 (0) Figure 4 (b)

Claims (1)

[Claims] (1) A brake circuit having a relief valve is provided in the main circuit between the hydraulic motor and the counterbalance valve, and the hydraulic motor can be operated at either high speed or low speed using pilot oil pressure controlled by an operating valve. In the control circuit for a hydraulic motor, the brake circuit has a pressure chamber and is configured with a relief valve whose pressure increase characteristics change over time by supplying and discharging hydraulic pressure to the pressure chamber. A control circuit for a hydraulic motor, in which a pressure chamber of a relief valve of the circuit is connected to an output side of an operating valve that controls high and low speeds of the hydraulic motor.