JP2008082537A - Hydraulic travel drive mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic travel drive mechanism for securing power required for emergency escape even when an electric capacity controlled motor is involved in impossible electric control due to such a trouble as breakage, while suppressing a sudden speed reduction during high speed travel. <P>SOLUTION: One of two variable capacity motors for the hydraulic travel drive mechanisms 1 is an electric capacity controlled motor 3 which has a capacity control solenoid proportional valve 32 for controlling an inclined rolling piston in the direction of minimizing a motor capacity with the shut-off of a control current from a controller Ct which inputs detection signals from pressure sensors S5, S5 for detecting pressure in a forward drive side main circuit 5 and a reverse drive side main circuit 6 of a closed circuit. The other variable capacity motor is a pressure capacity controlled motor 4 which has a capacity control valve 43 for controlling the inclined rolling piston in the direction of achieving the motor capacity corresponding to the pressure in the forward drive side main circuit 5 and the reverse drive side main circuit 6 with the shut-off of the control current from the controller Ct. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic travel drive device with HST (Hydrostatic Transmission), and more specifically, an electric capacity control motor provided for changing travel characteristics according to the situation makes electrical control impossible due to occurrence of trouble such as disconnection. The present invention relates to a hydraulic travel drive device that can secure power necessary for emergency escape and can suppress sudden deceleration during high-speed travel.

  A hydraulic travel drive device for a hydraulic travel drive vehicle generally includes a variable displacement pump and a closed circuit in which a variable displacement motor is connected by a main circuit. When the accelerator pedal is returned, the displacement of the variable displacement pump is reduced to generate brake pressure in the main circuit on the motor outlet side, and this brake pressure is converted into torque by the variable displacement pump and absorbed by the prime mover. Thus, a deceleration action can be obtained. As such a hydraulic travel drive device, for example, one having a configuration as described later is known. Hereinafter, an outline of a typical hydraulic travel drive apparatus according to a conventional example will be described.

  The hydraulic travel drive apparatus according to Conventional Example 1 uses a variable displacement motor to make an auxiliary braking function work. More specifically, in an HST vehicle (hydraulic traveling drive vehicle) equipped with an electric capacity control motor whose capacity is controlled by an electric command, during traveling in a state where the selection switch (auxiliary braking switch) of the auxiliary driving device is operated, When the degree of decrease in the accelerator pedal operation amount becomes equal to or greater than the set value, the motor regulator is operated by an external command to increase the capacity of the electric capacity control motor. Thereby, a brake pressure is generated in the main line on the outlet side of the electric capacity control motor. Then, a high braking force is generated together with the original brake pressure generated based on the decrease in the capacity of the variable displacement pump at this time, and the HST vehicle (hydraulic traveling drive vehicle) is decelerated at a larger deceleration than during normal traveling. (For example, refer patent document 1).

  The hydraulic travel drive apparatus according to Conventional Example 2 is designed to prevent over-rotation of the variable displacement motor during inertia travel. More specifically, a variable displacement pump driven by a prime mover, a variable displacement pump connected to the variable displacement pump by a pair of main circuits, and driven by oil discharged from the variable displacement pump, and a pair In the HST hydraulic travel drive device having a bypass line connecting the main circuit, the discharge amount of the variable displacement motor when the variable displacement motor rotates at the maximum allowable rotational speed with the maximum flow rate of the bypass line A flow rate regulating valve that is limited to the following is provided (for example, see Patent Document 2).

  The technology according to Conventional Example 3 (working vehicle emergency traveling mechanism) includes an emergency traveling mechanism that temporarily travels a traveling vehicle in the event of an emergency failure of any of the HST, the control device, the HST, and the control device. It is provided. Specifically, a hydraulic-mechanical transmission that controls a hydraulic continuously variable transmission mechanism (HST), a planetary gear mechanism, a forward / reverse switching mechanism, and a control device connected by an electronic circuit is mounted on the traveling vehicle. An emergency circuit that does not go through the control device is configured in the circuit. When the HST, control device, HST, or control device fails, the movable swash plate angle of the HST hydraulic pump is set to zero, and the engine is rotated with the sun gear rotation of the planetary gear mechanism fixed. (See, for example, Patent Document 3).

The technique (control mechanism for HST vehicle) according to Conventional Example 4 relates to a control mechanism for an HST vehicle that allows low-speed traveling according to the content of the abnormality. More specifically, when an abnormality is detected in the HST component, the controller stops the engine operation and stores the abnormality content. Then, it is determined whether to run the HST vehicle or to allow the HST vehicle to run according to the abnormality stored when the engine is restarted. (For example, refer to Patent Document 4).
JP 2004-332753 A JP-A-6-265013 JP 2003-130176 A JP 2000-170908 A

In the technology according to the above-described conventional example 1 (Japanese Patent Laid-Open No. 2004-332753), the travel characteristics of the hydraulic travel drive vehicle are changed by performing the capacity control of the electric capacity control motor according to the electric command according to the situation. From the viewpoint of sex, there are the following problems to be solved.
(1) When the variable displacement motor is configured to have a small capacity when the control is not performed, such as before the engine is started, a sufficient driving force is obtained when the wiring of the control system is disconnected. It is impossible to run because it is not obtained, and even if it is necessary to escape urgently, it is not possible to escape.
(2) Also, when the variable displacement motor is configured to have a large capacity without being controlled, such as before the engine is started, for example, when the vehicle is traveling at the maximum speed, the variable displacement Since the type motor has a minimum capacity, if the control system wiring is disconnected in such a case, the variable capacity motor will suddenly decelerate due to a sudden change from the minimum capacity to a large capacity, which is extremely dangerous. .

  In the case of the technique according to the above-described conventional example 2 (Japanese Patent Laid-Open No. 6-265013), in order to prevent over-rotation of the variable capacity motor during inertial traveling, A flow rate adjusting valve that restricts the discharge amount of the variable displacement motor when rotating at the maximum allowable number of rotations to less than that is provided. Therefore, the technique according to Conventional Example 1 has the same problem to be solved as in Conventional Example 1.

  In the case of the technology according to the above-described conventional example 3 (Japanese Patent Laid-Open No. 2003-130176), a mechanical device is required in addition to the HST, and the construction of the work vehicle is complicated, which is disadvantageous in terms of manufacturing cost. Become. In addition, when a failure occurs during high-speed traveling, the speed reduction ratio increases rapidly and the vehicle decelerates rapidly, which is extremely dangerous.

  In the case of the technique according to the above-described conventional example 4 (Japanese Patent Laid-Open No. 2000-170908), when an abnormality occurs, it stops at a rapid deceleration or shifts to a low speed running, which is extremely dangerous. .

  Therefore, the object of the present invention is not to provide a mechanical device other than HST, and even if electrical control becomes impossible due to occurrence of trouble such as disconnection, the power necessary for emergency escape can be secured, The present invention also provides a hydraulic travel drive device that makes it possible to suppress sudden deceleration during high-speed travel.

  In order to solve the above-mentioned problem, the gist of the means adopted by the hydraulic travel drive device according to claim 1 of the present invention is provided with a variable displacement pump driven by a prime mover and discharged from this variable displacement pump. In the hydraulic travel drive device comprising a closed circuit in which two variable displacement motors driven by hydraulic oil and having tilting pistons for controlling motor capacity are arranged in parallel, the two variable displacement motors One of the variable capacity motors has a direction in which the motor capacity is minimized by cutting off the control current from the controller that takes in the detection signal from the pressure sensor that detects the pressure of each of the pair of main circuits of the closed circuit. The electric capacity control motor is equipped with a capacity control electromagnetic proportional valve for controlling the tilting piston. It is characterized in that in a direction in which the motor capacity corresponding to a force which is a pressure capacity control motor with capacity control valve for controlling the tilting piston.

  The gist of means adopted by the hydraulic travel drive apparatus according to claim 2 of the present invention is that, in the hydraulic travel drive apparatus according to claim 1, the capacity control valve of the pressure capacity control motor is controlled by a control current from the controller. The switch is configured to introduce a pressure selected by a pressure selection valve that selects one of the pressures of the pair of main circuits.

  The gist of the features of the hydraulic travel drive device according to claim 3 of the present invention is the hydraulic travel drive device according to any one of claims 1 and 2, wherein the electric capacity control motor and A uniaxial axle is driven by the pressure capacity control motor.

  According to a fourth aspect of the present invention, there is provided a variable displacement pump driven by a prime mover, driven by hydraulic oil discharged from the variable displacement pump, and a motor. In the hydraulic travel drive device comprising a closed circuit in which two variable displacement motors having tilting pistons for controlling the displacement are arranged in parallel, one of the two variable displacement motors is variable. The capacity type motor is a first electric capacity control motor provided with a capacity control electromagnetic proportional valve having a function of controlling the tilting piston in a direction in which the motor capacity is minimized when the control current from the controller is cut off. The other variable displacement motor includes a second capacity control electromagnetic proportional valve having a function of controlling the tilting piston in a direction in which the motor capacity becomes maximum when the control current from the controller is cut off. It is characterized in that a gas volume control motor.

  According to a fifth aspect of the present invention, there is provided a hydraulic travel drive device according to claim 4, wherein the controller is provided with a capacity control electromagnetic proportional to the first electric capacity control motor. An auxiliary braking force switching function for demonstrating the auxiliary braking force stepwise by controlling the valve and the capacity control electromagnetic proportional valve of the second electric capacity control motor individually or together to increase the motor capacity is added. It is characterized by.

  The gist of the feature of the hydraulic travel drive apparatus according to claim 6 of the present invention is the hydraulic travel drive apparatus according to any one of claims 4 and 5, wherein the first electric capacity control is performed. A single-axle axle is driven by the motor and the second electric capacity control motor.

According to the hydraulic travel drive device of the first aspect of the present invention, when the capacity control electromagnetic proportional valve becomes uncontrollable due to interruption of the control current from the controller due to trouble such as disconnection, the motor capacity of the electric capacity control motor is minimized. Therefore, a sufficient driving force cannot be obtained.
However, the pressure capacity control motor provided with the pressure capacity control valve is controlled to have a motor capacity corresponding to the pressure of the main circuit. Therefore, since the motor capacity of the pressure capacity control motor increases as the pressure in the main circuit increases, it is possible to obtain an effect that the hydraulic travel drive vehicle traveling by the hydraulic travel drive apparatus can be escaped in an emergency. .

  On the other hand, when the control current from the controller is interrupted due to troubles such as disconnection during high-speed running, the motor capacity of the pressure capacity control motor is maintained at a small capacity because the pressure on the drive side main circuit is low. Therefore, the braking force does not increase. In addition, the electric capacity control motor has a minimum motor capacity and a small braking force. Therefore, the overall braking force does not increase rapidly. For example, since the rapid deceleration is suppressed as a whole of the hydraulic traveling drive vehicle traveling with this hydraulic traveling drive device, the safety improvement effect that the danger caused by the rapid deceleration of the hydraulic traveling drive vehicle at the time of high speed traveling is eliminated. Obtainable.

  Further, according to the hydraulic travel drive apparatus according to claim 2 of the present invention, in addition to the effect of the hydraulic travel drive apparatus according to claim 1, the pressure of the hydraulic oil flowing through the pair of main circuits is controlled by the pressure selection valve. When the travel drive side pressure is selected (the hydraulic fluid inflow pressure of the pressure capacity control motor), the pressure capacity control motor controls the motor capacity according to the travel drive side pressure, and travels even when the brake side pressure increases. If the side pressure does not change much, the deceleration will be slow. On the other hand, if the pressure selection valve selects the brake side (pressure oil control hydraulic fluid outflow side) pressure, the pressure capacity control motor increases in motor capacity and brake force in accordance with the brake side pressure. It can function as an auxiliary brake on long downhills. In addition, various brake force controls can be performed by increasing the motor capacity of the electric capacity control motor by the controller.

  Further, according to the hydraulic travel drive device according to claim 3 of the present invention, in addition to the effect of the hydraulic travel drive device according to claim 1, the brake-side pressure is selected by the pressure selection valve for each axis. The braking force of the axle can be increased. Therefore, when the hydraulic travel drive vehicle has two axles, the brake force of the one-axle axle and the brake force of the two-axle axle are individually changed, thereby gradually changing the grade on a long downhill or the like. It is possible to respond by changing the auxiliary braking force.

  According to the hydraulic travel drive apparatus according to claim 4 of the present invention, when the control current from the controller is interrupted, the motor capacity of the first electric capacity control motor is minimized, so that a sufficient driving force can be obtained. become unable. However, since the motor capacity of the second electric capacity control motor is controlled to be maximized, it is possible to obtain an effect that the hydraulic travel drive vehicle traveling by this hydraulic travel drive device can escape in an emergency. .

On the other hand, when the control current from the controller is interrupted for some reason during high-speed traveling, the motor capacity of the second electric capacity control motor becomes large and the braking force increases.
However, the motor capacity of the first electric capacity control motor is minimized and the braking force is reduced. Therefore, since the increase in the overall braking force is mitigated, for example, sudden deceleration is suppressed as a whole of the hydraulic traveling drive vehicle that travels with this hydraulic traveling drive device. It is possible to obtain an improvement effect of safety that the degree of the risk due to it becomes small.

  According to the hydraulic travel drive apparatus of the fifth aspect of the present invention, in addition to the effect of the hydraulic travel drive apparatus according to the fourth aspect, the controller controls the capacity proportional electromagnetic proportional valve of the first electric capacity control motor. And the capacity control electromagnetic proportional valve of the second electric capacity control motor can be controlled individually or together to increase the motor capacity. Accordingly, the auxiliary braking force can be exerted stepwise according to the slope of the downhill, so that it is possible to travel safely on a long slope.

  The hydraulic travel drive apparatus according to claim 6 of the present invention is configured to drive a one-shaft axle by a first electric capacity control motor and a second electric capacity control motor. Therefore, in addition to the effect of the hydraulic travel drive device according to claim 4, the auxiliary braking force is adjusted more finely according to the long slope of the downhill than in the case of the hydraulic travel drive device according to claim 4. can do.

  Hereinafter, a hydraulic travel drive apparatus according to Embodiment 1 of the present invention will be described with reference to the attached drawings. 1 is a diagram showing a schematic configuration of a hydraulic travel drive apparatus according to Embodiment 1 of the present invention, FIG. 2 is a diagram showing a pump of the hydraulic travel drive apparatus according to Embodiment 1 of the present invention, and FIG. FIG. 4 is a diagram showing an electric capacity control motor of the hydraulic travel drive apparatus according to the first embodiment of the present invention, FIG. 4 is a diagram showing a pressure capacity control motor of the hydraulic travel drive apparatus according to the first embodiment of the present invention, and FIG. It is capacity | capacitance control explanatory drawing of the electric capacity control motor and pressure capacity control motor of the hydraulic travel drive device which concerns on this Embodiment 1. FIG.

Reference numeral 1 shown in FIG. 1 is a hydraulic travel drive device (hydraulic circuit) according to Embodiment 1 of the present invention. The hydraulic travel drive device 1 is mainly composed of a pump 2, an electric capacity control motor 3, and a pressure capacity control motor 4. Each electromagnetic switching valve incorporated in the hydraulic travel drive device 1 is configured to be switched and controlled by the controller Ct.
As shown in FIG. 2, the pump 2 includes a pair of main circuits connected to two ports, that is, a forward drive side main circuit 5 and a reverse drive side main circuit 6. The electric capacity control motor 3 and the pressure capacity control motor 4 are reversibly driven by hydraulic oil discharged from the variable displacement pump 21 and supplied from the forward drive side main circuit 5 and the reverse drive side main circuit 6. It is configured to be.

  The pump driven by the prime mover M together with the variable displacement pump 21 is a charging pump 22 for preventing cavitation of the main circuit. Further, the four-port three-position electromagnetic switching valve 23 that is switched by the control current from the controller Ct is a forward / reverse switching electromagnetic valve, and the one disposed on the upstream side of the forward / reverse switching electromagnetic valve 23 has a pump capacity. This is a pump displacement control electromagnetic proportional valve 24 that performs control.

  As shown in FIG. 3, the driving torque of the electric capacity control motor 3 is transmitted to the wheels provided at both ends of the axle 8 through the differential gear device of the speed reducer 7 and the axle 8. Yes. Further, as shown in FIG. 4, the driving torque of the pressure capacity control motor 4 is transmitted to the wheels provided at both ends of the axle 8 through the differential gear device of the speed reducer 7 and the axle 8. Has been. Hereinafter, the configurations of the electric capacity control motor 3 and the pressure capacity control motor 4 will be described in more detail.

  The electric capacity control motor 3 is supplied from a controller Ct that takes in detection signals from pressure sensors S5 and S6 that detect the pressure of hydraulic oil in the forward drive side main circuit 5 and the reverse drive side main circuit 6 of the closed circuit. A 3-port 2-position capacity control electromagnetic proportional valve 32 that is switched by a control current is provided. The displacement control solenoid proportional valve 32 is configured to be operated by the large-capacity side oil chamber 33a and the small-capacity side oil chamber 33b to control the tilting piston 33 that controls the motor capacity of the electric capacity control motor 3. ing.

  More specifically, the capacity control electromagnetic proportional valve 32 switches from the A position to the B position when a control current is supplied to the solenoid from the controller Ct, and the forward drive side main circuit 5 and the reverse drive side main circuit 6 respectively. Among the hydraulic oil pressures, the high pressure side pressure is supplied to the large capacity side oil chamber 33a via the check valve Vc. That is, the high-pressure side pressure is always supplied to the small-capacity side oil chamber 33b, but the large-capacity-side oil chamber 33a is supplied with the high-pressure side pressure as the primary pressure, and the capacity control electromagnetic proportional valve 32. The control pressure by the command current from the controller Ct is supplied. The position of the tilting piston 33 is determined by this control pressure, and the motor capacity is controlled. On the other hand, when the control current from the controller Ct is interrupted due to a disconnection trouble or the like, the hydraulic oil in the large-capacity side oil chamber 33a is discharged, so that the tilting piston 33 has a minimum motor capacity. It moves to. Note that qmin in FIG. 3 indicates the minimum motor capacity, qmax indicates the maximum motor capacity, and the same applies to FIG.

  The pressure capacity control motor 4 is freely switched between the C position and the D position by excitation and non-excitation under the control of the controller Ct. The forward drive side main circuit 5 and the reverse drive side main circuit 6 are closed circuit. And a 4-port 2-position pressure selection valve 42 for selecting one of the pressures. More specifically, the forward drive side main circuit 5 communicates with one of the two ports on the hydraulic oil inflow side of the pressure selection valve 42 (the lower port in FIG. 4) via the check valve Vc. The reverse drive side main circuit 6 communicates with the other port (the upper port in FIG. 4) via a check valve Vc. That is, when the solenoid is excited by the controller Ct, the pressure selection valve 42 switches to the C position and selects the pressure of the reverse drive side main circuit 6. Further, when de-energized by the controller Ct, the pressure selection valve 42 is switched to the D position and selects the pressure of the forward drive side main circuit 5. The pressure selected by the pressure selection valve 42 is supplied to the capacity control valve 43.

  The secondary pressure side port of the pressure selection valve 42 has a large capacity side oil chamber 44 a that operates a tilting piston 44 that controls the motor capacity of the pressure capacity control motor 4 via the E position of the capacity control valve 43 and a small size. Of the capacity side oil chamber 44b, it communicates with the large capacity side oil chamber 44a. The large-capacity side oil chamber 44 a is configured to communicate with the tank via the F position of the capacity control valve 43. Further, the secondary pressure side port of the pressure selection valve 42 communicates with the capacity control valve 43 and a small capacity side oil chamber 44 b that operates the tilting piston 44.

  That is, the displacement control valve 43 switches to the E position when the solenoid is excited by a command from the controller Ct, and supplies the hydraulic oil supplied from the pressure selection valve 42 to the large-capacity side oil chamber 44a. When excited, the position is switched to the F position, and the hydraulic oil in the large-capacity side oil chamber 44a is discharged to the tank. However, as is well understood from FIG. 4, in the capacity control valve 43, the spool is operated by the pressure supplied from the pressure selection valve 42 even in the case of non-excitation, and the large capacity side oil chamber 44a and the small capacity side oil are Since the pressure capacity control is performed in balance with the chamber 44 b, the motor capacity of the pressure capacity control motor 4 is configured to be a capacity corresponding to the pressure supplied from the pressure selection valve 42.

  Hereinafter, the operation mode of the hydraulic travel drive apparatus according to the first embodiment of the present invention will be described. First, the solenoid of the forward / reverse switching solenoid valve 23 of the regulator (forward / reverse switching solenoid valve 23 + pump capacity control solenoid proportional valve 24) of the pump 2 is excited when the HST vehicle (not shown) equipped with this hydraulic travel drive device 1 moves forward. A case is assumed where hydraulic oil is discharged from the pump 2 to the forward drive side main circuit 5 and the drive pressure is increased. Further, the motor capacity of the electric capacity control motor 3 is controlled as shown in FIG. 5 by the pressure signal from the pressure sensor S5 provided in the forward drive side main circuit 5, and the motor capacity of the pressure capacity control motor 4 is A case where control is performed as shown in FIG. 5 by the capacity control valve 43 will be described as an example.

  When a malfunction such as disconnection occurs in the control circuit that controls the capacity control electromagnetic proportional valve 32 of the electric capacity control motor 3 at the start of traveling of the HST vehicle, the capacity control electromagnetic proportional valve 32 remains in the A position, Since the tilting piston 33 moves in the direction of decreasing the motor capacity of the electric capacity control motor 3, the motor capacity of the electric capacity control motor 3 becomes the minimum capacity.

  Accordingly, even if the HST vehicle is caused to travel from the stopped state while the capacity control electromagnetic proportional 32 is held at the A position, the electric capacity control motor 3 cannot output a sufficient driving torque. However, the motor capacity of the pressure capacity control motor 4 is such that the drive pressure of the forward drive side main circuit 5 is controlled by the capacity control valve 43 via the D position of the pressure selection valve 42, so that the control circuit has problems such as disconnection. Even if this occurs, the pressure capacity control motor 4 can output a sufficient driving torque.

According to the hydraulic travel drive device 1 according to Embodiment 1 of the present invention, the HST vehicle can be traveled by the total drive force of the electric capacity control motor 3 and the pressure capacity control motor 4.
Accordingly, there is no possibility that emergency escape cannot be performed unlike the conventional example, which is extremely effective at the time of emergency escape.

  In addition, when the HST vehicle is traveling at high speed, when the capacity control is suddenly disabled due to disconnection or the like in the control circuit, the motor capacity of the electric capacity control motor 3 becomes small as described above, so sudden deceleration is performed. There is no such thing as causing braking force. On the other hand, since the pressure capacity control motor 4 is not related to electrical control, the motor capacity is maintained according to the pressure, and the motor capacity does not change abruptly. Therefore, according to the hydraulic traveling drive device 1 according to the first embodiment of the present invention, even when the electric control circuit suddenly breaks or the like, it may suddenly decelerate like the conventional example. It is extremely safe because it is not.

  Next, an example in which the pressure capacity control motor 4 functions as an auxiliary brake when going down a long slope will be described. In general, in the case of a large vehicle having a large vehicle weight, an auxiliary brake such as an exhaust brake using an engine exhaust or a retarder is provided. In the case of a retarder, a braking force is generated on the propeller shaft. However, in the case of an HST vehicle, the propeller shaft is often not provided, so that the retarder cannot be equipped in many cases. Therefore, in the case of the pressure capacity control motor 4 of the hydraulic travel drive device 1 according to the first embodiment, as described above, the C position and the D position are switched by switching between excitation and non-excitation of the solenoid by the control from the controller Ct. There is provided a 4-port 2-position pressure selection valve 42 for selecting the pressure of either the forward drive side main circuit 5 in the closed circuit or the reverse drive side main circuit 6. Thus, the function as an auxiliary brake can be exhibited.

  That is, if the pressure selection valve 42 of the pressure capacity control motor 4 is switched to the C position by the control from the controller Ct while the accelerator pedal (not shown) is being returned, the pressure (pump action of the pump action) of the reverse drive side main circuit 6 is switched. Therefore, a pressure higher than the pressure of the forward drive side main circuit 5) is introduced into the displacement control valve 43 as a brake pressure. Therefore, according to the hydraulic travel drive device 1 according to the first embodiment of the present invention, the motor capacity of the pressure capacity control motor 4 increases, so that a large auxiliary braking force can be obtained. Further, as long as the electric control is normal, the pressure of the reverse drive side main circuit 6 is introduced into the capacity control electromagnetic proportional valve 32. Therefore, the motor capacity of the electric capacity control motor 3 is increased, and a larger auxiliary braking force is obtained. It is extremely useful when going down long slopes.

On the other hand, when the vehicle is traveling on a flat ground and it is not necessary to apply the auxiliary brake (the pressure selection valve 42 is in the C position), even if the accelerator pedal is returned, the pressure is lower than the pressure of the reverse drive side main circuit 6. The pressure of the forward drive side main circuit 5 is introduced from the pressure selection valve 42 to the capacity control valve 43.
Accordingly, the motor capacity of the pressure capacity control motor 4 is small, the braking force is small, and inertial traveling that slowly decelerates over time is possible, so the burden of operating the accelerator pedal is reduced.

  Next, a hydraulic traveling drive apparatus according to Embodiment 2 of the present invention will be described with reference to the attached drawings. FIG. 6 is a diagram showing a pump of a hydraulic travel drive apparatus according to Embodiment 2 of the present invention, and FIG. 7 is a hydraulic travel motor (electric capacity control motor +) of the hydraulic travel drive apparatus according to Embodiment 2 of the present invention. It is a figure which shows a pressure capacity control motor. The hydraulic traveling drive apparatus according to the second embodiment of the present invention has the same main configuration as the hydraulic traveling drive apparatus according to the first embodiment, as is well understood in the comparison of related drawings. Are given the same reference numerals, and only the differences will be described. 6 and 7, the control circuit by the controller is omitted.

  That is, the hydraulic travel drive apparatus according to the second embodiment of the present invention includes a pump 2 having the same configuration as that used in the hydraulic travel drive apparatus 1 according to the first embodiment, an electric capacity control motor 3, and a pressure. Two sets of capacity control motors 4 are provided. Then, the driving torque of one set of the electric capacity control motor 3 and the pressure capacity control motor 4 is transmitted to one axle 8 through the transfer 7 ', and the wheels provided at both ends of the axle 8 are driven. It is comprised so that. In the case of the hydraulic travel drive device according to the second embodiment of the present invention, there is one forward / reverse switching electromagnetic valve 23, and the two forward / reverse switching electromagnetic valves 23 are used for two variable displacement pumps 21. The hydraulic oil discharge direction is configured to be switched.

  According to the hydraulic travel drive device according to the second embodiment of the present invention, as described above, the electric capacity control motor 3 and the pressure capacity having the same configuration as that used in the hydraulic travel drive device 1 according to the first embodiment. Since the uniaxial axle 8 is driven by the control motor 4, the same effect as the hydraulic travel drive device according to the first embodiment can be obtained. Furthermore, according to the hydraulic travel drive apparatus according to Embodiment 2 of the present invention, the brake side pressure can be selected by either one or both of the pressure selection valves 42 of the two sets of pressure capacity control motors 4. Therefore, since both the braking force of the one-axle axle 8 and the braking force of the two-axle axle 8 can be increased, it is possible to respond by changing the auxiliary braking force depending on the degree of the gradient on a long downhill or the like. An excellent effect can be exhibited.

A hydraulic travel drive apparatus according to Embodiment 3 of the present invention will be described with reference to the accompanying drawings.
FIG. 8 is a schematic configuration explanatory view of the hydraulic travel drive apparatus according to Embodiment 3 of the present invention, and FIG. 9 is a diagram of the first electric capacity control motor that minimizes the motor capacity when the control current from the controller is cut off. FIG. 10 is a diagram illustrating the configuration, and FIG. 10 is a diagram illustrating the relationship between the motor capacity and the control current for controlling the capacity control electromagnetic proportional valve of the first electric capacity control motor. FIG. 11 is a diagram for explaining the configuration of the second electric capacity control motor in which the motor capacity becomes maximum when the control current from the controller is cut off, and FIG. 12 controls the capacity control electromagnetic proportional valve of the second electric capacity control motor. It is explanatory drawing of the relationship of the motor capacity | capacitance with respect to the control current to do.

  Reference numeral 1 ′ shown in FIG. 8 is a hydraulic travel drive device (hydraulic circuit) according to Embodiment 3 of the present invention. The hydraulic travel drive device 1 ′ includes a variable displacement pump 21 driven by a prime mover M, and is connected to two ports of the variable displacement pump 21 to form a forward drive side main circuit 5 constituting a closed circuit. The main circuit comprising the reverse drive side main circuit 6 is provided. Then, the first electric capacity control motor 50 and the second electric motor that drive the wheel provided at the tip of the axle 8 through the transfer 7 ′ by the hydraulic oil discharged from the variable displacement pump 21 through the main circuit. The capacity control motor 60 is driven.

  As shown in FIG. 9, the first electric capacity control motor 50 includes a capacity control electromagnetic proportional valve 52 controlled by a control current from a controller (not shown). The capacity control electromagnetic proportional valve 52 controls the motor capacity of the first electric capacity control motor 50 by supplying and discharging pressure oil to and from the large capacity oil chamber 53a and the small capacity oil chamber 53b of the tilting piston 53. It is configured to be.

  More specifically, the capacity control electromagnetic proportional valve 52 switches from the G position to the H position when a control current is supplied to the solenoid from the controller, and the forward drive side main circuit 5 and the reverse drive side main circuit 6 The high-pressure side pressure is supplied to the large-capacity-side oil chamber 53a as a primary pressure with a secondary pressure corresponding to the control current. That is, although the high-pressure side pressure is always supplied to the small-capacity side oil chamber 53b, the high-pressure side pressure is supplied to the large-capacity side oil chamber 53a. The tilting piston 53 controls the motor capacity of the first electric capacity control motor 50 in the direction of the motor capacity corresponding to the control current. On the other hand, when the control current is interrupted due to a disconnection trouble or the like, the hydraulic oil in the large-capacity side oil chamber 53a is discharged.

  The second electric capacity control motor 60 includes a capacity control electromagnetic proportional valve 62 controlled by a control current from a controller, and the capacity control electromagnetic proportional valve 62 allows the large capacity side oil chamber of the tilting piston 63 to be controlled. The motor capacity is controlled by supplying and discharging the pressure oil in 63a and the small capacity side oil chamber 63b.

More specifically, the high pressure side pressure of the forward drive side main circuit 5 and the reverse drive side main circuit 6 selected by the check valve Vc is always supplied to the small capacity side oil chamber 63b of the tilting piston 63. It is configured. When the control current from the controller is cut off, the capacity control electromagnetic proportional valve 62 is in the J position, and the high pressure side pressure is supplied to the large capacity oil chamber 63a. Therefore, since the tilting piston 63 moves in the left direction in FIG. 11, the motor capacity of the second electric capacity control motor 60 is maximized as shown in FIG.
On the other hand, when the control current is supplied from the controller, the capacity control electromagnetic proportional valve 62 supplies the secondary pressure corresponding to the current to the large capacity side oil chamber 63a, so that the tilting piston 63 responds to the control current. , Move leftward in FIG. Then, as the control current becomes larger, as shown in FIG. 12, the motor capacity of the second electric capacity control motor 60 is decreased and finally the motor capacity is minimized.

  Further, in order to allow the auxiliary braking force to be exerted stepwise according to the slope of the downhill and to travel safely on a long slope, the controller has a capacity control electromagnetic of the first electric capacity control motor 50. Auxiliary braking force switching function for demonstrating the auxiliary braking force in stages by controlling the proportional valve 52 and the capacity control electromagnetic proportional valve 62 of the second electric capacity control motor 60 individually or together to increase the motor capacity. Is added.

  Hereinafter, the operation mode of the hydraulic travel drive device 1 ′ according to the third embodiment of the present invention will be described. When the control current from the controller is interrupted, the motor capacity of the first electric capacity control motor 50 is minimized. 2 The motor capacity of the electric capacity control motor 60 is maximized. Further, when traveling on a long slope, the capacity control electromagnetic proportional valve 52 of the first electric capacity control motor 50 and the capacity control electromagnetic proportional valve 62 of the second electric capacity control motor 60 are individually or together controlled to be stepwise. Can exert an auxiliary braking force. Therefore, according to the hydraulic travel drive device 1 ′ according to the third embodiment of the present invention, the same effect as in the first embodiment can be obtained. In the case of the hydraulic travel drive device 1 ′ according to the third embodiment, as described above, the first electric capacity control motor 50 and the second electric capacity control motor 60 are used to drive the one-axis axle. Although configured, as in the case of the first embodiment, it can be configured to drive individual axles for each motor.

It is a figure which shows schematic structure of the hydraulic travel drive device which concerns on Embodiment 1 of this invention. It is a figure which shows the pump of the hydraulic traveling drive apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the electric capacity control motor of the hydraulic travel drive apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the pressure capacity control motor of the hydraulic traveling drive apparatus which concerns on Embodiment 1 of this invention. It is capacity | capacitance control explanatory drawing of the electric capacity control motor and pressure capacity control motor of the hydraulic travel drive device which concerns on Embodiment 1 of this invention. It is a figure which shows the pump of the hydraulic traveling drive apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the hydraulic travel motor (electric capacity control motor + pressure capacity control motor) of the hydraulic travel drive apparatus which concerns on Embodiment 2 of this invention. It is typical structure explanatory drawing of the hydraulic traveling drive apparatus which concerns on Embodiment 3 of this invention. FIG. 10 is a configuration explanatory diagram of a first electric capacity control motor according to Embodiment 3 of the present invention, in which the motor capacity is minimized when the control current from the controller is interrupted. FIG. 10 is an explanatory diagram of a relationship between motor capacity and control current for controlling a capacity control electromagnetic proportional valve of a first electric capacity control motor according to Embodiment 3 of the present invention. FIG. 10 is a configuration explanatory diagram of a second electric capacity control motor according to Embodiment 3 of the present invention, in which the motor capacity becomes maximum when the control current from the controller is interrupted. FIG. 10 is an explanatory diagram of a motor capacity relationship with respect to a control current for controlling a capacity control electromagnetic proportional valve of a second electric capacity control motor according to the third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hydraulic travel drive device, 1 '... Hydraulic travel drive device 2 ... Pump, 21 ... Variable displacement pump, 22 ... Charging pump, 23 ... Forward / reverse switching solenoid valve, 24 ... Pump capacity control solenoid proportional valve 3 ... Electricity Capacity control motor, 32 ... Capacity control electromagnetic proportional valve, 33 ... Tilt piston, 33a ... Large capacity side oil chamber, 33b ... Small capacity side oil chamber 4 ... Pressure capacity control motor, 42 ... Pressure selection valve, 43 ... Capacity control Valve 44, tilt piston, 44a ... large capacity side oil chamber, 44b ... small capacity side oil chamber 5 ... forward drive side main circuit 6 ... reverse drive side main circuit 7 ... speed reducer, 7 '... transfer 8 ... axle 50 ... 1st electric capacity control motor, 52 ... Capacity control electromagnetic proportional valve (3 port 2 position), 53 ... Tilt piston, 53a ... Large capacity side oil chamber, 53b ... Small capacity side oil chamber 60 ... 2nd electric capacity control Motor, 62 ... Capacity control electromagnetic Reiben (3 port 2 position), 63 ... tilting piston, 63a ... large side oil chamber, 63 b ... small-capacity side oil chamber Ct ... controller M ... motor S5 ... pressure sensor S6 ... pressure sensor Vc ... check valve

Claims (6)

  In addition to a variable displacement pump driven by a prime mover, two variable displacement motors driven by hydraulic oil discharged from the variable displacement pump and having tilting pistons for controlling the motor displacement are arranged in parallel. In the hydraulic travel drive apparatus including the closed circuit, one of the two variable displacement motors includes a pressure sensor that detects a pressure of each of the pair of main circuits of the closed circuit. This is an electric capacity control motor having a capacity control electromagnetic proportional valve that controls the tilting piston in the direction in which the motor capacity is minimized by cutting off the control current from the controller that takes in the detection signal of the other, and the other variable capacity motor Is a pressure capacity control mode equipped with a capacity control valve that controls the tilting piston in the direction of motor capacity corresponding to the pressure of the main circuit by cutting off the control current from the controller. Hydraulic traveling drive system, characterized in that the motor.   The pressure control valve of the pressure capacity control motor is switched by the control current from the controller, and the pressure selected by the pressure selection valve for selecting one of the pressures of the pair of main circuits is introduced. The hydraulic travel drive apparatus according to claim 1, wherein the hydraulic travel drive apparatus is provided.   3. The hydraulic travel drive apparatus according to claim 1, wherein the electric capacity control motor and the pressure capacity control motor are configured to drive a uniaxial axle. 4. .   A variable displacement pump that is driven by a prime mover is provided, and two variable displacement motors that are driven by hydraulic oil discharged from the variable displacement pump and have tilting pistons that control the motor displacement are arranged in parallel. In the hydraulic travel drive apparatus having a closed circuit, one of the two variable displacement motors has a minimum motor capacity when the control current from the controller is cut off. The first electric capacity control motor is provided with a capacity control electromagnetic proportional valve having a function of controlling the tilting piston in the direction. The other variable capacity motor has a motor capacity when the control current from the controller is interrupted. A hydraulic travel drive device comprising a second electric capacity control motor provided with a capacity control electromagnetic proportional valve having a function of controlling a tilting piston in a maximum direction.   Stepwise by increasing the motor capacity to the controller by individually or together controlling the capacity control electromagnetic proportional valve of the first electric capacity control motor and the capacity control electromagnetic proportional valve of the second electric capacity control motor. 5. The hydraulic travel drive device according to claim 4, further comprising an auxiliary braking force switching function for exerting an auxiliary braking force.   The one-axis axle is configured to be driven by the first electric capacity control motor and the second electric capacity control motor. 6. Hydraulic travel drive device.

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