JP2008223909A - Hydraulic traveling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of cavitation during acceleration while suppressing heat generation of a circuit. <P>SOLUTION: A counterbalance valve 16 as a control valve 15 and a brake valve is provided between a hydraulic pump 11 and a tank T, and a traveling hydraulic motor 12. Return pipelines 34, 35 are provided between the counterbalance valve 16 and the motor 12, for returning oil delivered from the motor 12 during traveling deceleration to an inlet side of the motor 12. The return pipelines 34, 35 are provided with relief valves 36, 37. Assuming the above, the hydraulic traveling device is provided with a bypass line L for returning a portion of the discharged oil from the motor 12 during traveling deceleration to a motor inlet side pipeline 13 via the control valve 15, a throttle 39 for throttling the flow rate of the bypass line L, and an opening and closing valve 40 for opening and closing the bypass line L. The opening and closing valve 40 is constituted to open during traveling deceleration and shutting off during acceleration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic travel device used in a work vehicle such as a wheel excavator or a wheel crane.

  FIG. 3 shows a wheel excavator as an example to which the present invention is applied.

  This wheel excavator is configured by mounting an upper swing body 4 on a lower traveling body 3 having a front wheel 1 and a rear wheel 2 so as to be rotatable about a vertical axis.

  The upper swing body 4 is provided with a cab 5, a work attachment (excavation attachment) 6 and the like, while the lower traveling body 3 is provided with a hydraulic travel device (not shown) using a hydraulic motor as a drive source. The hydraulic motor is rotated by depressing an accelerator pedal in 5 to drive the traveling drive wheels (one or both of the front wheels 1 and the rear wheels 2).

  In such a work vehicle, a technique disclosed in Patent Document 1 is known as a technique for decelerating and stopping the inertial rotation of the hydraulic motor at the time of traveling deceleration when the accelerator pedal depressing operation is stopped (this technique is referred to as known technique 1). ).

  In this known technique 1, a counter balance valve is provided as a brake valve between a hydraulic motor (hereinafter simply referred to as a motor) and a control valve that is switched and operated in conjunction with the depression of an accelerator pedal. A return line is provided between the motor and the motor on both sides of the motor, and a high-pressure relief valve is provided on the return line. When the vehicle is decelerating, a counter balance valve is used between the motor and the control valve. Simultaneously with the shut-off, the brake pressure by the relief valve is generated in the motor outlet side pipe line (reverse side pipe line when traveling forward).

  However, according to this known technique 1, an internal circulation system is employed in which oil is circulated in a short path (hereinafter referred to as a motor internal path) formed by a part of both motor side pipe lines and a return pipe line during traveling deceleration. Therefore, the heat generated by the relief operation of the relief valve is intense.

  More specifically, the amount of oil that circulates internally is determined by the amount of oil in the motor internal path (motor internal oil amount) at the start of deceleration, and the number of circulations is determined by the inertia of the excavator and the amount of oil in the motor. The number of circulations is a value determined by dividing the capacity determined by the motor rotation speed at the start of deceleration x motor capacity by the amount of oil in the motor. The more the number of circulations, that is, the number of times oil passes through the relief valve, the more heat is generated. , Oil temperature rises severely.

  In this case, since the number of oil circulations is increased due to the short internal path, the heat generation of the circuit becomes intense, so that the heat load of the motor is large, which causes the motor to be damaged or the durability to be reduced.

  On the other hand, as a technique for suppressing the heat generation of such a circuit (known technique 2), as shown in FIG. 3 of Patent Document 2, a counterbalance valve is provided with a passage with a throttle that opens in a neutral position. A technique has been proposed in which oil spilled from a motor is returned to the motor through a path of a motor outlet side pipe, a passage with a throttle of a counter balance valve, a control valve, and a motor inlet side pipe during traveling deceleration.

According to this known technique 2, since motor spilled oil is taken out from the motor internal path and circulated (external circulation) through a long path passing through the control valve, the number of oil circulations can be reduced to suppress circuit heat generation.
JP-A 63-266201 JP-A 63-63831

  However, according to the known technique 2, when the accelerator pedal is depressed (accelerated) while decelerating, the control valve is switched to the acceleration position while the counter balance valve is in a neutral state. Circulating oil flows into the tank.

  When this happens, the amount of oil spilled from the motor exceeds the amount of inflow oil, and cavitation occurs.

  The only way to prevent this is to reduce the throttle in the passage with the throttle of the counter balance valve (increase the degree of throttling). This causes the external circulation of oil to stagnate when decelerating. The objective cannot be achieved.

  Accordingly, the present invention provides a hydraulic travel device capable of preventing the occurrence of cavitation during acceleration while suppressing heat generation in a circuit.

  According to the first aspect of the present invention, there is provided a control valve for controlling the rotation direction and speed of the hydraulic motor between a hydraulic pump and a tank as a hydraulic source and a hydraulic motor as a travel drive source. A counter balance valve for blocking the oil flow between the control valve and the hydraulic motor is provided, and between the counter balance valve and the motor, between the motor both-side pipe lines, the hydraulic oil discharged from the hydraulic motor is decelerated during traveling. In a hydraulic traveling apparatus in which a return pipe is provided from the motor outlet side pipe to the motor inlet side pipe and a relief valve for generating a brake pressure is provided in the return pipe, the motor discharge oil is A detour line that returns the part to the motor inlet side line via the control valve, a throttle means for reducing the flow rate of the detour line, and opening and closing the detour line And an on-off valve control means for controlling the on-off valve. The on-off valve control means is configured to open the on-off valve at the time of traveling deceleration and to shut off at the time of acceleration and normal traveling. is there.

  According to a second aspect of the present invention, in the configuration of the first aspect, the on-off valve control means is configured to open the on-off valve on the condition that the meter-out opening area of the control valve becomes equal to or less than a predetermined value during traveling deceleration. Is.

  According to a third aspect of the present invention, there is provided a control valve for controlling the rotation direction and speed of the hydraulic motor between a hydraulic pump and a tank as a hydraulic source and a hydraulic motor as a travel drive source, and at the time of travel deceleration and stop. A counter balance valve for blocking the oil flow between the control valve and the hydraulic motor is provided, and between the counter balance valve and the motor, between the motor both-side pipe lines, the hydraulic oil discharged from the hydraulic motor is decelerated during traveling. In a hydraulic traveling apparatus in which a return pipe is provided for returning the motor from the motor outlet side pipe to the motor inlet side pipe, and a relief valve for generating a brake pressure is provided in the return pipe, the motor discharge oil is supplied to the motor at the time of traveling deceleration. A detour line that returns to the motor inlet line via the control valve, a throttle means for restricting the flow rate of the detour line, and a neutral control valve In this state, a tank line for guiding the discharge oil of the hydraulic pump to the tank, a boost line for guiding the pump discharge oil to the motor inlet side pipe in a neutral state of the control valve, and tank line pressure control means for controlling the pressure of the tank line The tank line pressure control means is configured to set the pressure of the tank line to a high pressure at the time of traveling deceleration and to a low pressure at the time of acceleration and normal traveling.

  According to a fourth aspect of the present invention, in the configuration of the third aspect, the tank line pressure control means includes a tank line relief valve whose set pressure is switched between a high pressure and a low pressure in accordance with the introduced pilot pressure, and the tank line relief valve. The pilot pressure switching valve for switching the pilot pressure introduced to the engine and a controller for controlling the pilot pressure switching valve. The operation of the pilot pressure switching valve based on the signal from the controller at the time of traveling deceleration causes the tank line relief valve to The set pressure is switched to a high pressure and the tank line pressure is set to a high pressure.

  According to the present invention, at the time of traveling deceleration, apart from the internal circulation through the return pipeline, a part of the motor discharge oil is returned to the motor via the control valve by the detour line (external circulation). The circuit heat generation can be suppressed by reducing the number of circulations.

  In this case, by restricting the detour flow rate by the detour line throttling means, it is possible to ensure the flow rate through the return pipe line, so that the original deceleration action can be ensured.

  That is, it is possible to achieve both a deceleration action and a heat generation prevention action by a partial external circulation system.

  In particular, according to the third and fourth aspects of the present invention, when the vehicle is decelerating, the pump discharge oil is introduced to the motor inlet side through the boost line by increasing the pressure of the tank line, and merged with the oil by the partial external circulation method. Therefore, the effect of preventing heat generation is higher.

  In addition, according to the present invention, the occurrence of cavitation during acceleration can be reliably prevented.

  In other words, according to the first and second aspects of the present invention, the bypass line passing through the control valve is closed by the on-off valve during acceleration, so that it is possible to prevent the occurrence of cavitation during the transition period from deceleration to acceleration.

  On the other hand, according to the inventions of claims 3 and 4, cavitation occurs during acceleration because the pump line and the motor inlet side pipe line are always connected via the control valve (in the neutral position by the boost line). There is no fear of it.

  By the way, in the first aspect of the invention, when the on-off valve is opened in a so-called half brake state in which the control valve is stopped before the neutral position during traveling deceleration, that is, when the meter-out opening area of the control valve is still large, the tank passes through the control valve. There is a risk that cavitation will occur due to an increase in the amount of oil that flows into the tank.

  In this regard, according to the second aspect of the invention, the opening / closing valve is opened on condition that the meter-out opening area is less than a certain value, that is, the outflow flow rate from the control valve is at a level that does not cause cavitation. The occurrence of cavitation in the half brake state can be prevented.

  An embodiment of the present invention will be described with reference to FIGS.

1st Embodiment (refer FIG. 1)
In FIG. 1, reference numeral 11 denotes a hydraulic pump (hereinafter simply referred to as a pump) as a traveling hydraulic power source. Both the forward side and the reverse side of the pump 11 and the tank T and a traveling hydraulic motor (hereinafter simply referred to as a motor) 12 are illustrated. A hydraulic pilot type control valve 15 that controls the rotation direction and speed of the motor 12 between the pipe lines 13 and 14 and the flow of oil between the control valve 15 and the motor 12 when traveling and decelerating and stopping. A counter balance valve 16 as a brake valve is provided.

  The pilot ports on both sides of the control valve 15 are connected to the secondary side of an accelerator valve (hydraulic pilot valve) 18 operated by an accelerator pedal 18a via an electromagnetic forward / reverse switching valve 17.

  Thus, when the accelerator pedal 18a is depressed, the secondary pressure of the accelerator valve 18 is sent as a pilot pressure to the control valve 15 via the forward / reverse switching valve 17, and the control valve 15 is moved from the neutral position a to the right side of the figure. Switch to forward position B or reverse position C on the left.

  Reference numerals 19 and 20 denote connection lines that connect the control valve 15 and the motor side pipe lines 13 and 14, reference numerals 21 and 22 denote outlet lines that connect the connection lines 19 and 20 to the outlet port of the counter balance valve 16, and reference numerals 23 and 24 denote Check valves 25 and 26 provided on the connection lines 19 and 20 are check valves provided on the outlet lines 21 and 22.

  Further, the control valve 15 is provided with a communication passage 27 that connects the connection lines 19 and 20 at the neutral position A, and a connection passage 30 that connects the pump line 28 and the tank line 29 at the neutral position A. .

  Here, for example, at the time of forward movement, the pressure of the forward side pipeline 13 is applied to the forward side (left side in the figure) pilot port of the counter balance valve 16, so that the counter balance valve 16 is moved from the neutral position a to the forward position b on the left side in the figure. Switch.

  In this state, the oil discharged from the pump 11 is pump line 28 -control valve 15 -connection line 19 -advance side pipe 13 -motor 12 -reverse side pipe 14 -advance position b of counter balance valve 16 -exit line 22 -Connection line 20-Control valve 15-Tank line 29-Flowing along the path of tank T, the motor 12 rotates in the forward direction, and the rotational force of this motor 12 is applied to the traveling drive wheels (front and rear wheels 1, 2 in FIG. On the other hand, the excavator runs.

  31 is a main relief valve for setting the maximum pressure of the circuit, 32 is a pilot pump as a pilot hydraulic pressure source, and 33 is a pilot relief valve for setting the discharge pressure of the pilot pump 32.

  On the other hand, between the motor both-side pipe lines 13 and 14, return pipe lines 34 and 35 are provided for returning oil flowing out from the outlet side of the motor 12 to the motor inlet side when traveling and decelerating at the time of forward movement and reverse movement, respectively. The return pipes 34 and 35 are provided with relief valves 36 and 37 for generating brake pressure.

  In the relief valves 36 and 37, the pressure of one of the motor side pipe lines 13 and 14 (reverse side pipe line 14 when moving forward and the forward side pipe line 13 when moving backward) is introduced into the pilot port during traveling, and this pressure is constant. Relief operation starts when it rises to. As a result, the braking force due to the set pressure of the relief valves 36 and 37 acts, and the motor 12 is decelerated and stopped.

  In this hydraulic travel device, a bypass line 38, a throttle 39 that restricts the flow rate of the bypass line 38, an electromagnetic on-off valve 40 that opens and closes the bypass line 38, and the on-off valve 40 is controlled to open and close. On-off valve control means is provided.

  The bypass pipe 38 has one end connected to the reverse side pipe 14 and the other end connected to the connection line 20. When the control valve is in a neutral state (during traveling deceleration), the bypass pipe 38, the connection line 20, By the passage 27 and the connection line 19, a detour line L that circulates part of the motor discharge oil via the control valve 15 is configured.

  The on-off valve control means is based on a motor discharge pressure sensor 41 that detects the motor discharge pressure, a pilot pressure sensor 42 that detects the forward pilot pressure sent to the control valve 15, and signals from both sensors 41, 42. And a controller 43 that outputs an operation signal to the on-off valve 40.

  The operation of the hydraulic travel device including the operation of the controller 43 will be described.

  When the pedal depression operation of the accelerator valve 18 is stopped during forward traveling, the control valve 15 returns to the neutral position A, and the supply of oil to the motor 12 is stopped.

  At this time, the motor 12 tries to continue to rotate due to the inertia of the vehicle, but the counter balance valve 16 returns to the neutral position a by stopping the supply of the pilot pressure, so that the oil in the motor circuit is blocked with respect to the tank T. The

  Then, the forward relief valve 36 starts the relief operation from the time when the pressure in the reverse side pipeline 14 rises to a certain value, and the braking force by the set pressure of the relief valve 36 acts to decelerate the motor 12. ·Stop.

  Here, until the motor 12 starts decelerating and stops, the oil discharged from the motor 12 circulates (internally circulates) in a path that returns to the motor 12 through the reverse side pipeline 14 and the return pipeline 34. The temperature is raised by the relief operation of the relief valve 36 for each circulation.

  When the controller 43 determines that the vehicle is decelerating based on the signal from the motor discharge pressure sensor 41 and determines that the meter-out opening area of the control valve 15 is less than a certain value based on the signal from the pilot pressure sensor 42 In addition, an opening signal is output to the on-off valve 40.

  As a result, the on-off valve 40 is switched to the open position on the right side of the figure, the bypass line 38 is opened, and the detour line L is formed. Therefore, a part of the motor discharge oil is separated from the detour line L (bypass line 38, connection Line 20, communication passage 27 of control valve 15, connection line 19) enters forward side pipeline 13, joins oil that has passed through return pipeline 34, and returns to motor 12.

  In this way, a part of the motor discharge oil circulates in the long bypass line L via the control valve that is different from the internal circulation route via the return line 34, so that the oil amount per circulation increases and the relief is performed. Since the number of times the valve passes is reduced, heat generation in the motor circuit can be suppressed.

  In this case, since the bypass flow rate is reduced by the restriction 39 of the bypass pipe line 38, the flow rate passing through the return pipe line 34 can be secured, so that the deceleration action by the original relief valve 36 can be secured.

  That is, it is possible to achieve both a deceleration action and a heat generation prevention action by a partial external circulation system.

  On the other hand, when an acceleration operation is performed by depressing the accelerator pedal 18a from the decelerating state, the pilot pressure of the control valve 15 rises. Therefore, based on a signal from the pilot pressure sensor 42 that detects this, the controller 43 switches from the controller 43 to the on-off valve 40. A close signal is output.

  Thereby, since the on-off valve 40 is closed and the bypass line L is blocked, it is possible to prevent the occurrence of cavitation during the transition period from the deceleration to the acceleration.

  After this, the counter balance valve 16 opens a little later and enters a normal running state.

  By the way, at the time of traveling deceleration, the accelerator pedal 18a may not be completely returned, but may be in a half-pedal state where the accelerator pedal 18a stops halfway (a half brake state where the control valve 15 stops before neutral).

  In this state, since the meter-out opening area of the control valve 15 is still large, if the on-off valve 40 is opened in this state, the amount of oil flowing out to the tank T through the control valve 15 may increase and cavitation may occur. is there.

  In this regard, in this apparatus, the opening / closing valve is provided on condition that the meter-out opening area is not more than a certain value as described above, that is, the flow rate from the control valve 15 is at a level that does not cause cavitation. Since 40 is opened, the occurrence of cavitation in the half brake state can be prevented.

Second embodiment (see FIG. 2)
In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description thereof is omitted.

  In the second embodiment, a point where a bypass line 38 for connecting the reverse travel side line 14 and the connection line 20 is provided, and a point where a throttle 39 is provided in the bypass line 38, during traveling deceleration (of the control valve 15). The point where the detour line L is configured at the time of neutrality is the same as in the first embodiment.

  Differences from the first embodiment are as follows.

  (I) A boost line 44 that connects the tank line 29 and the two connection lines 21 and 21 is provided.

  (Ii) As tank line pressure control means for controlling the pressure of the tank line 29, the tank line 29 is provided with a tank line relief valve 45 for switching the set pressure between a high pressure and a low pressure according to the pilot pressure introduced. The pilot line 46 of the relief valve 45 is connected to the tank T and the pilot pump 20 via an electromagnetic pilot pressure switching valve 47 controlled by a controller 48.

  The pilot pressure switching valve 47 has a low pressure position A that connects the pilot line 46 to the tank T and a high pressure position B that connects the pilot line 46 to the pilot pump 20 and is set to the low pressure position A shown in the figure during normal driving. The

  In this state, the tank line relief valve 45 is set to a low pressure, and the pressure of the tank line 29 becomes a low pressure, so that the oil discharged from the motor 12 returns to the tank T through the tank line 29.

  On the other hand, at the time of traveling deceleration, the switching valve 47 is switched to the high pressure position B by a signal from the controller 48 based on a signal from the motor discharge pressure sensor 41.

  In this state, the tank line relief valve 45 is set to a high pressure, and the pressure of the tank line 29 becomes a high pressure.

  For this reason, at the time of deceleration during forward movement, as in the first embodiment, the internal circulation route through which the motor discharge oil passes through the return line 34, the bypass line L (the bypass line 38, the connection line 20, and the control valve 15) are connected. While returning to the motor 12 by the passage 27, the external circulation route through the connection line 19), the pump discharge oil is sent to the advance side line 13 through the boost line 44 and the outlet line 25 as necessary.

  Thus, since the low temperature oil from the pump 11 is mixed with both the internal and external circulating oil and introduced into the motor 12, the heat generation preventing effect is higher than in the case of the first embodiment.

  Further, according to this embodiment, the pump line 28 and the motor inlet side pipe line are connected (connected by the boost line 44 in the neutral position) regardless of the position of the control valve 15. There is no risk of cavitation.

  According to this embodiment, the pump discharge oil is always sent to the motor inlet side conduit 13 as necessary as described above, and there is no risk of cavitation always including the half brake state. Therefore, unlike the on / off valve 40 of the first embodiment, the controller 48 does not need to use the meter-out opening area of the control valve 15 as a switching condition for the pilot pressure switching valve 47. Or not.

  However, the pilot pressure of the control valve 15 may be detected instead of the motor discharge pressure, and the controller 48 may determine whether or not the vehicle is decelerating based on this pilot pressure.

  By the way, the present invention can be widely applied not only to wheel excavators but also to wheel type work vehicles such as wheel type dozers, wheel type cranes and the like.

It is a circuit block diagram of the hydraulic traveling apparatus concerning 1st Embodiment of this invention. It is a circuit block diagram of the hydraulic traveling apparatus concerning 2nd Embodiment of this invention. It is a schematic side view of a wheel excavator as an application target example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Pump T tank 12 Motor 13 Motor forward side pipeline 14 Motor reverse side pipeline 15 Control valve 16 Counter balance valve L Detour line 19,20 Connection line which constitutes detour line 27 Control valve communication path which constitutes detour line 28 Pump line 29 Tank line 30 Connection passage 32 Pilot pump 34, 35 Return line 36, 37 Relief valve 38 Bypass line constituting bypass line 40 On-off valve 41 Motor discharge pressure sensor constituting on-off valve control means 42 Same pilot Pressure sensor 43 Controller 44 Boost line 45 Tank line relief valve constituting tank pressure control means 46 Pilot line of relief valve 47 Pilot pressure switching valve constituting tank pressure control means 48 Controller

Claims (4)

  Between a hydraulic pump and tank as a hydraulic source and a hydraulic motor as a travel drive source, a control valve for controlling the rotational direction and speed of the hydraulic motor, and at the time of travel deceleration and stop, the control valve and the hydraulic motor A counter balance valve that shuts off the flow of oil between the motor and the motor between the counter balance valve and the motor. In a hydraulic traveling device in which a return pipe is provided to return to the motor inlet side pipe and a relief valve for generating brake pressure is provided in the return pipe, a part of the motor discharge oil is supplied to the motor via a control valve during traveling deceleration. A detour line that returns to the inlet-side pipeline, a throttle means that throttles the flow rate of the detour line, an on-off valve that opens and closes the detour line, and this opening and closing And a closing valve control means for controlling the, the on-off valve control means, the on-off valve opens during travel deceleration, hydraulic traveling apparatus characterized by being configured to block at the time of acceleration and normal running.   2. The hydraulic travel device according to claim 1, wherein the on-off valve control means is configured to open the on-off valve on condition that the meter-out opening area of the control valve becomes equal to or less than a predetermined value during traveling deceleration.   Between a hydraulic pump and tank as a hydraulic source and a hydraulic motor as a travel drive source, a control valve for controlling the rotational direction and speed of the hydraulic motor, and at the time of travel deceleration and stop, the control valve and the hydraulic motor A counter balance valve that shuts off the flow of oil between the motor and the motor between the counter balance valve and the motor. In a hydraulic traveling device in which a return pipe is provided to return to the motor inlet side pipe, and a relief valve for generating brake pressure is provided in the return pipe, motor discharge oil is supplied to the motor inlet side via the control valve at the time of running deceleration. A detour line for returning to the pipeline, a throttle means for restricting the flow rate of the detour line, and the hydraulic pump in the neutral state of the control valve. A tank line for guiding the discharged oil to the tank, a boost line for guiding the pump discharged oil to the motor inlet side pipe in the neutral state of the control valve, and tank line pressure control means for controlling the pressure of the tank line. The hydraulic pressure traveling device is characterized in that the line pressure control means is configured to set the pressure of the tank line to a high pressure during traveling deceleration and to a low pressure during acceleration and normal traveling.   The tank line pressure control means includes a tank line relief valve that switches between a high pressure and a low pressure according to the pilot pressure that is introduced, a pilot pressure switching valve that switches the pilot pressure introduced into the tank line relief valve, The controller for controlling the pilot pressure switching valve is configured to switch the set pressure of the tank line relief valve to a high pressure by operating the pilot pressure switching valve based on a signal from the controller at the time of traveling deceleration to increase the pressure of the tank line. The hydraulic travel device according to claim 3, wherein the hydraulic travel device is configured to be set.

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