JP2004176919A - Speed limit system for hydraulic running vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed limit system for a hydraulic running vehicle capable of limiting speed of the vehicle in a simple structure. <P>SOLUTION: The speed limit system for the hydraulic running vehicle comprises a pump capacity control means 12C controlling capacity of a variable capacity type hydraulic pump 12 for running so that differential pressure between load pressure of a hydraulic motor 13 for running and discharged pressure of the variable capacity type hydraulic pump 12 for running are set to be LS set pressure, a speed detecting means 31 of the hydraulical running vehicle, and a controller 30 changing the LS set pressure when the detected speed exceeds the designated value and lessening capacity of the variable capacity type hydraulic motor for running. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a vehicle speed limiting system for a working vehicle, particularly a hydraulic traveling vehicle.

  2. Description of the Related Art Conventionally, in a hydraulic traveling vehicle that travels by driving a variable displacement traveling hydraulic motor using pressure oil of a traveling hydraulic pump driven by an engine, the maximum vehicle speed is limited by the displacement of the traveling hydraulic pump. The maximum vehicle speed differs depending on the country where the hydraulic vehicle travels, and when exporting hydraulic vehicles to countries with different maximum vehicle speeds, export vehicles equipped with hydraulic pumps with different capacities to each country. It corresponds by that.

  However, if various types of traveling hydraulic pumps having different capacities are prepared for the hydraulic traveling vehicle according to the maximum vehicle speed in each country, the types of traveling hydraulic pumps increase. In addition, the number of types of related parts such as piping adapted for the vehicle hydraulic pump is increased, which leads to an increase in management man-hours. Furthermore, if there is a change in the specifications before shipment, the traveling hydraulic pump must be replaced, resulting in extra assembly man-hours.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a vehicle speed limiting system for a hydraulic traveling vehicle that can limit the vehicle speed with a simple structure.

  In order to achieve the above object, a vehicle speed limiting system for a hydraulic traveling vehicle according to a first aspect of the present invention is a vehicle speed limiting system for a hydraulic traveling vehicle comprising a traveling hydraulic motor and a variable displacement traveling hydraulic pump. Pump displacement control means for controlling the displacement of the variable displacement traveling hydraulic pump such that the differential pressure between the load pressure of the variable displacement traveling hydraulic pump and the discharge pressure of the variable displacement traveling hydraulic pump becomes the load sensing set pressure (hereinafter referred to as the LS set pressure). A vehicle speed detecting means for the hydraulic traveling vehicle, and a controller for changing an LS set pressure to decrease the capacity of the variable displacement hydraulic motor when the vehicle speed detected by the vehicle speed detecting means exceeds a set value. And characterized in that:

  In a second aspect based on the first aspect, the controller includes LS set pressure setting means for setting the LS set pressure, wherein the setting means is configured to set the LS set pressure selected from another plurality of types of LS set pressure setting means. It is configured to be replaceable by means.

  According to the first invention, when the vehicle speed exceeds the set value, the LS set pressure is changed to reduce the capacity of the variable displacement traveling hydraulic motor, so that a vehicle speed limiting system can be realized with a simple configuration.

  Further, according to the second aspect, since the LS set pressure setting means is provided with an exchangeable controller, the LS set pressure setting means is simply exchanged with an LS set pressure setting means selected from a plurality of different types. You can easily change the speed limit.

  Next, a specific embodiment of a vehicle speed limiting system for a hydraulic traveling vehicle according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a system configuration diagram of a vehicle speed limiting system for a hydraulic traveling vehicle according to an embodiment of the present invention.

  A traveling pump 12 is connected to the engine 11, and the traveling pump 12 is driven by the engine 11 to discharge pressure oil. The pressure oil discharged from the travel pump 12 is sent to the travel motor 13 via the travel control valve 21 and the hydraulic swivel joint 15. The traveling motor 13 is connected to an input shaft of the transmission 14 and drives the transmission 14.

  The transmission 14 is provided with a traveling speed detection pump 17, which rotates in proportion to the rotation of the output shaft of the transmission 14. The pressure oil discharged from the traveling speed detection pump 17 is sent to the traveling speed detection motor 18 via the hydraulic swivel joint 15. The traveling pump 12 is a variable displacement hydraulic pump and has a pump displacement control means 12C. The traveling motor 13 is a variable displacement hydraulic motor and has a motor displacement control unit 13C.

  The work vehicle (not shown) includes a lower traveling body (not shown) and an upper revolving body (not shown). The upper revolving unit is provided with a working machine (not shown), and a hydraulic swivel joint 15 is provided at a connection between the lower traveling unit and the upper revolving unit. The engine 11 is provided on an upper revolving unit (not shown), the transmission 14 is provided on a lower traveling unit (not shown), and the controller 30 is provided on an upper revolving unit (not shown).

  The transmission 14 is connected to a shift valve 16 as a shift control means via a hydraulic swivel joint 15. The transmission valve 16 sends pressure oil from a transmission pump 19 to a first-speed clutch 14F or a second-speed clutch 14S of the transmission 14 via a hydraulic swivel joint 15. The transmission valve 16 is a two-position switching valve having a simple structure and low cost, and switches between a first-speed position 16A and a second-speed position 16B shown in FIG.

  The transmission 14 has a planetary gear mechanism, and applies or releases pressure to or from the first speed clutch 14F for low speed or the second speed clutch 14S for high speed in accordance with a pressure signal from the speed change valve 16 to turn on and off. Is set. That is, the first-speed clutch 14F and the second-speed clutch 14S are of a type in which the clutch is engaged by applying pressure oil, and the clutch is released by releasing the pressure oil.

  Further, the transmission 14 has two speed stages of first speed and second speed. When the transmission 14 is set to the first speed, the shift valve 16 is set to the first speed position 16A, the hydraulic oil from the shift valve 16 is applied to the first speed clutch 14F, the first speed clutch is engaged, and the pressure of the second speed clutch 14S is increased. Release the oil and disengage the second speed clutch 14S. When the transmission 14 is set to the second speed, the shift valve 16 is set to the second speed position 16B, the pressure oil from the shift valve 16 is applied to the second speed clutch 14S to engage the second speed clutch, and the pressure of the first speed clutch 14F is increased. Release the oil and disengage the first speed clutch 14F.

  A vehicle speed detection gear 35 for generating a vehicle speed signal is provided on an output shaft of the vehicle speed detection motor 18, and is rotated by the vehicle speed detection motor 18. On the outer periphery of the vehicle speed detection gear 35, for example, a predetermined number of teeth, slits, or irregularities are formed. The vehicle speed detection sensor 31 is provided close to the outer periphery of the vehicle speed detection gear 35, and generates, for example, a pulse generated when a predetermined number of teeth pass through a signal detection unit of the vehicle speed detection sensor 31 as an electric signal.

  A vehicle speed detection sensor 31 serving as a vehicle speed detection means is connected to the controller 30 and transmits a vehicle speed signal to the controller 30 as an electric signal. The controller 30 performs an arithmetic process on the vehicle speed signal to calculate a vehicle speed.

  The traveling control valve 21 switches from the illustrated neutral position N to the forward position F or the reverse position R, and controls the direction of the pressure oil discharged from the traveling pump 12 to send the pressure oil to the traveling motor 13. The traveling control valve 21 receives the traveling pilot pressure, which is the pilot pressure from the forward / reverse switching valve 22, at the forward pressure receiving portion 21F or the reverse pressure receiving portion 21R of the traveling control valve 21, thereby moving from the neutral position N to the forward position F or the reverse position. Switch to position R.

  The forward / reverse switching valve 22 switches to the illustrated forward position FK in response to a forward signal from the controller 30, and switches to the reverse position RK in response to a reverse signal.

  The accelerator pedal 23A operates the traveling pilot pressure valve 23 by being depressed to generate traveling pilot pressure. The traveling pilot pressure, which is a means for detecting the amount of depression of the accelerator pedal 23A, changes according to the amount of depression of the accelerator pedal 23A, and increases at a predetermined rate when the amount of depression of the accelerator pedal 23A increases.

  In a circuit between the traveling pump 12 and the traveling control valve 21, a traveling load pressure sensor 33 as a load pressure detecting means is provided. The traveling load pressure sensor 33 transmits the detected traveling load pressure signal to the controller 30.

  A forward traveling pressure sensor 36 is provided in a circuit between the forward / reverse switching valve 22 of the traveling control valve 21 and the forward pressure receiving portion 21F of the traveling control valve 21. A reverse traveling pressure sensor 37 is provided in a circuit between the forward / reverse switching valve 22 and the reverse pressure receiving portion 21 </ b> R of the traveling control valve 21. The forward traveling pressure sensor 36 transmits an forward traveling signal to the controller 30 when an internal switch is turned on by the traveling pilot pressure, and the reverse traveling pressure sensor 37 transmits a reverse traveling signal when the internal switch is turned on by the traveling pilot pressure.

  The travel control valve 21 is connected to the travel motor 13 via a hydraulic swivel joint 15 by a forward circuit 46F and a reverse circuit 46R. A circuit 47F branched from the forward circuit 46F and a circuit 47R branched from the reverse circuit 46R between the travel control valve 21 and the hydraulic swivel joint 15 are connected via a shuttle valve 42. The output circuit LSM of the shuttle valve 42 is connected to the pump displacement control means 12C. From the shuttle valve 42, the higher pressure oil of the forward circuit 46F and the reverse circuit 46R is output as the motor load pressure LS1 of the traveling motor 13, and enters the pump displacement control means 12C through the output circuit LSM. .

  The discharge circuit 41 of the traveling pump 12 is connected to the traveling control valve 21. The pump pressure detection circuit LSP branched from the discharge circuit 41 is connected to the pump displacement control means 12C. The pump discharge pressure LS2 of the discharge circuit 41 of the traveling pump 12 enters the pump displacement control means 12C.

  The pump displacement control means 12C is connected to the controller 30. The pump displacement control means 12C determines whether the pressure difference ΔLS (= LS2−LS1) between the pump discharge pressure LS2 of the traveling pump 12 and the motor load pressure LS1 of the traveling motor 13 according to the pump displacement signal transmitted from the controller 30. The displacement of the traveling pump 12 is controlled so as to have a predetermined LS set pressure. The pump displacement control means 12C is provided with an LS electromagnetic proportional valve 12CLS so that the LS set pressure can be set according to a signal from the controller 30.

  An electromagnetic coil 12CS and a spring 12CP are provided on both sides of the LS electromagnetic proportional valve 12CLS. In response to a signal from the controller 30, the electromagnetic coil 12CS applies a reaction force to a spool (not shown) of the LS electromagnetic proportional valve 12CLS. The spool of the LS electromagnetic proportional valve 12CLS is formed by the total force of the reaction force of the electromagnetic coil 12CS and the pushing force of the traveling motor 13 due to the motor load pressure LS1, the force of the traveling pump 12 due to the pump discharge pressure LS2, and the spring 12CP. Move to a position where the total force and the force balance. The LS electromagnetic proportional valve 12CLS sends the pressure oil from the discharge circuit 41 of the traveling pump 12 to the pump displacement control cylinder 12CC in accordance with the opening amount of the spool. That is, the pump displacement control means 12C is a load sensing means for detecting a pressure difference ΔLS (= LS2−LS1) between the pump discharge pressure LS2 of the traveling pump 12 and the motor load pressure LS1 of the traveling motor 13. The set pressure of the spool of the LS electromagnetic proportional valve 12CLS balanced by the differential pressure ΔLS is set to the LS set pressure.

  If the force due to the motor load pressure LS1 of the traveling motor 13 increases, the LS electromagnetic proportional valve 12CLS will be at the position 12A shown in the figure, and the pressure oil of the pump displacement control cylinder 12CC will be drained to the oil tank 25, and the swash plate of the traveling pump 12 will be described. 12a is tilted in the illustrated max direction, and the capacity of the traveling pump 12 increases. On the other hand, if the force due to the pump discharge pressure LS2 of the traveling pump 12 increases, the LS electromagnetic proportional valve 12CLS will be at the position 12B, pressure oil will enter the pump displacement control cylinder 12CC, and the swash plate 12a of the traveling pump 12 will be shown in FIG. By tilting in the min direction, the capacity of the traveling pump 12 decreases.

  Here, if the reaction force of the spool due to the electromagnetic coil 12CS of the LS electromagnetic proportional valve 12CLS is reduced, the sum of the force of the traveling pump 12 due to the pump discharge pressure LS2 and the force of the spring 12CP is greater than the force of the electromagnetic coil 12CS. Since the force becomes larger than the sum of the reaction force and the pushing force of the traveling motor 13 due to the motor load pressure LS1, the LS electromagnetic proportional valve 12CLS moves to the position 12B. Thereby, pressure oil enters the pump displacement control cylinder 12CC, the swash plate 12a of the traveling pump 12 is tilted in the min direction, and the displacement of the traveling pump 12 can be reduced. Therefore, by changing the LS set pressure, which is the set pressure as the load sensing means of the pump displacement control means 12C, the swash plate 12a of the traveling pump 12 can be inclined in the min direction, and the displacement of the traveling pump 12 can be reduced. It has become.

  The forward / reverse switch 34 is connected to the controller 30 and transmits a forward command signal or a reverse command signal to the controller 30.

  When the controller 30 receives the traveling load pressure signal detected by the traveling load pressure sensor 33 in the circuit between the traveling pump 12 and the traveling control valve 21, the controller 30 detects the pressure of the hydraulic oil discharged from the traveling pump 12 as a load by the traveling resistance. It is calculated whether the pressure does not exceed a predetermined value.

  The controller 30 calculates the vehicle speed by performing arithmetic processing on a vehicle speed signal which is an electric signal detected by the vehicle speed detection sensor 31, and when the vehicle speed exceeds a predetermined speed, for example, 50 km / h, the capacity of the traveling pump 12 is reduced. A pump displacement reduction signal to be reduced is sent to the pump displacement control means 12C. When the LS electromagnetic proportional valve 12CLS of the pump displacement control means 12C receives the pump displacement reduction signal, it reduces the reaction force of the spool of the electromagnetic proportional valve 12CLS by the electromagnetic coil 12CS. Then, as described above, the sum of the force of the traveling pump 12 due to the pump discharge pressure LS2 and the force of the spring 12CP is the pushing force due to the reaction force of the electromagnetic coil 12CS and the motor load pressure LS1 of the traveling motor 13. Therefore, the LS solenoid proportional valve 12CLS moves to the position 12B and reduces the capacity of the traveling pump 12.

  Further, the controller 30 includes an LS set pressure setting adapter 39 which is LS set pressure setting means capable of setting the LS set pressure. The LS set pressure setting adapter 39 is detachable from the controller 30 by a connector (not shown) so that the controller 30 can be replaced from the outside. For example, by replacing the adapter for the maximum vehicle speed of 50 km / h, the adapter for the maximum vehicle speed of 60 km / h, the adapter for the maximum vehicle speed of 70 km / h, etc., the plural types of the LS set pressure are set, and the plural types of the maximum vehicle speed are set. it can. For example, when the LS set pressure setting adapter 39, which is an adapter for the maximum vehicle speed of 50 km / h, is attached, the vehicle speed is calculated by processing the vehicle speed signal which is an electric signal detected by the vehicle speed detection sensor 31. When the speed exceeds 50 km / h, the capacity of the traveling pump 12 is reduced as described above.

  Next, the operation of the vehicle speed limiting system according to the present embodiment will be described.

  When the operator switches the forward / reverse switch 34 to the forward side, the forward / reverse switching valve 22 is at the forward position FK, and when the accelerator pedal 23A is depressed, the traveling pilot pressure is applied to the forward pressure receiving portion 21F of the traveling control valve 21 and the neutral position. The position is switched from N to the forward position F. The forward running pressure sensor 36 is turned on internally by the running pilot pressure, and transmits a forward running signal to the controller 30.

  The controller 30 first switches the shift valve 16 to the first speed position 16A based on a forward command signal of the forward / reverse switch 34 and a speed stage signal (for example, second speed) set by a speed stage lever (not shown). The transmission 14 is shifted to the first forward speed by engaging the clutch 14F and disengaging the second-speed clutch 14S.

  The traveling control valve 21 sends the pressure oil discharged from the traveling pump 12 to the forward port 13F of the traveling motor 13 via the hydraulic swivel joint 15. The traveling motor 13 rotates in the forward direction to drive the transmission 14, and the work vehicle travels forward.

  When the vehicle speed increases and the vehicle speed signal from the vehicle speed detection sensor 31 exceeds the maximum vehicle speed set, for example, at a vehicle speed of 50 km / h, the controller 30 sends a pump displacement reduction signal for decreasing the displacement of the traveling pump 12 to a pump displacement control. Transmit to the means 12C.

  When the LS electromagnetic proportional valve 12CLS of the pump displacement control means 12C receives the pump displacement decrease signal, it reduces the reaction force of the spool by the electromagnetic coil 12CS. Then, as described above, the sum of the force of the traveling pump 12 due to the pump discharge pressure LS2 and the force of the spring 12CP is the pushing force due to the reaction force of the electromagnetic coil 12CS and the motor load pressure LS1 of the traveling motor 13. LS solenoid proportional valve 12CLS is in position 12B. Pressurized oil enters the pump displacement control cylinder 12CC, and the swash plate 12a of the traveling pump 12 is inclined in the min direction to reduce the displacement of the traveling pump 12.

  Then, when the speed of the work vehicle decreases and becomes equal to or lower than the maximum vehicle speed, for example, 50 km / h, the controller 30 sends a pump displacement signal to the pump displacement control means 12C so as to increase the displacement of the traveling pump 12. Send.

  As described above, in the present embodiment, the vehicle speed can be limited only by sending the pump displacement reduction signal to the LS electromagnetic proportional valve 12CLS of the pump displacement control means 12C and reducing the reaction force of the spool by the electromagnetic coil 12CS. Therefore, in the case where the load sensing means is used as the pump displacement control means 12C of the hydraulic traveling vehicle, the existing pump displacement control means 12C may be used, and no new additional parts are required. Just change it. With such a simple structure, the hydraulic traveling vehicle, which is a working vehicle, can travel without exceeding the maximum speed which is the limit vehicle speed.

  Further, when changing the maximum vehicle speed, it is only necessary to replace the LS set pressure setting adapter 39 which is the LS set pressure setting means and the maximum vehicle speed setting means, and it is possible to easily change the maximum vehicle speed which is the limited vehicle speed. it can.

  Further, the hydraulic traveling vehicle may be a vehicle that does not have an upper revolving structure, and may be applied to, for example, a wheel loader, a forklift, or another work vehicle. When the vehicle speed limiting system of the present invention is applied to a vehicle having no upper revolving structure, the hydraulic swivel joint 15 may be omitted.

  The low-speed first-speed clutch 14F and the high-speed second-speed clutch 14S in the transmission 14 are described as clutches of the type in which the clutch is applied by applying pressure oil, and the clutch is released by releasing the pressure oil.

  Conversely, a clutch connecting spring is provided for the first speed clutch 14F for low speed and the second speed clutch 14S for high speed, the clutch is released by releasing the pressure oil, and the clutch is released by applying the pressure oil. Is also good. That is, when the transmission 14 is set to the first speed, the pressure oil from the shift valve 16 is released to the first speed clutch 14F, the first speed clutch is engaged, and the pressure oil of the second speed clutch 14S is applied to the second speed clutch 14S. And the transmission 14 is set to the first speed. When the transmission 14 is set to the second speed, the pressure oil from the shift valve 16 is released to the second speed clutch 14S to engage the second speed clutch, and the pressure oil of the first speed clutch 14F is applied to disengage the first speed clutch 14F. The transmission 14 may be set to the second speed.

FIG. 1 is a system configuration diagram of a vehicle speed limiting system for a hydraulic traveling vehicle according to the present invention.

Explanation of reference numerals

12 Traveling pump (Variable displacement traveling hydraulic pump)
12C Pump displacement control means 13 Traveling motor (hydraulic motor for traveling)
30 controller 31 vehicle speed detection sensor (vehicle speed detection means)
39 LS set pressure setting adapter (load sensing set pressure setting means)

Claims (2)

In a vehicle speed limiting system of a hydraulic traveling vehicle equipped with a traveling hydraulic motor and a variable displacement traveling hydraulic pump,
Pump displacement control means (12C) for controlling the displacement of the variable displacement hydraulic pump so that the differential pressure between the load pressure of the traveling hydraulic motor and the discharge pressure of the variable displacement hydraulic pump becomes the load sensing set pressure. When,
Vehicle speed detecting means of the hydraulic traveling vehicle,
When the vehicle speed detected by the vehicle speed detecting means exceeds a set value, a controller (30) for changing the load sensing set pressure to reduce the capacity of the variable displacement traveling hydraulic motor;
A vehicle speed limiting system for a hydraulic traveling vehicle, comprising: The controller (30) includes a load sensing set pressure setting means (39) for setting the load sensing set pressure,
The vehicle speed limiting system according to claim 1, wherein the load sensing set pressure setting means is replaceable with a setting means selected from a plurality of different types of load sensing set pressure setting means.

Images