JP4120441B2 - Hydraulic travel drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a hydraulic travel drive device that hydraulically drives a work vehicle or the like.
[0002]
[Prior art]
  2. Description of the Related Art In recent years, as a means for hydraulically driving a work vehicle such as a wheel loader or a self-propelled excavator, a travel drive device having an HST (Hydrostatic Transmission) has been developed.
[0003]
  For example, in Patent Document 1 below, a variable displacement hydraulic pump driven by a prime mover and a hydraulic motor coupled to a traveling wheel via a transmission constitute a closed circuit, and the rotational speed of the prime mover is determined. A displacement-operating hydraulic pump whose discharge pressure increases as it rises, and a regulator that receives the hydraulic pressure output from the displacement-operating hydraulic pump and increases the capacity of the variable displacement hydraulic pump as the hydraulic pressure increases A travel drive device is disclosed.
[0004]
  Further, in this apparatus, a three-position electromagnetic switching valve is interposed between the regulator and the displacement operating hydraulic pump. In this electromagnetic switching valve, when the shift lever is operated forward, one solenoid is excited and switched to a position for guiding the discharge oil of the displacement operating hydraulic pump to the forward port of the regulator, and the shift lever is moved backward. When operated, the other solenoid is excited and switched to a position for guiding the discharge oil of the capacity-operating hydraulic pump to the reverse port of the regulator. Further, when the shift lever is operated to the neutral position, the solenoids are not excited, and the electromagnetic switching valve is held at the neutral position (a position where the regulator and the capacity operation hydraulic pump are shut off) by the force of the spring. Is done.
[0005]
  According to this device, by switching the electromagnetic switching valve according to the forward / reverse operation of the shift lever, the tilt angle of the variable displacement hydraulic pump is operated in the direction according to the operation, and the tilt By adjusting the angle according to the change in the rotational speed of the prime mover (that is, the displacement of the variable displacement hydraulic pump is operated), the stepless speed change by the hydrostatic pressure is realized.
[0006]
[Patent Document 1]
          JP-A-6-265013 (2nd page, FIG. 1)
[0007]
[Problems to be solved by the invention]
  In the device described in Patent Document 1, since the vehicle is switched between forward and reverse by an electromagnetic switching valve interposed between the regulator and the hydraulic pump, disconnection or short circuit of the electric system related to the electromagnetic switching valve is performed. If an abnormality such as an electromagnetic valve stick occurs and the electromagnetic switching valve does not operate normally, the tilt angle of the variable displacement hydraulic pump, that is, the pump displacement cannot be controlled normally.
[0008]
  In particular, when the solenoid excitation signal input to the electromagnetic switching valve is interrupted due to disconnection of the electrical system during forward traveling or reverse traveling, the electromagnetic switching valve is in the neutral position by the spring force regardless of the driver's operation of the shift lever. Thus, the space between the regulator and the displacement operation hydraulic pump is blocked, and the displacement and the absorption flow rate of the variable displacement hydraulic pump become zero or close to each other. On the other hand, the traveling wheel and the traveling hydraulic motor connected to the rotating wheel rotate, and oil is discharged from the hydraulic motor, so the variable displacement type in which the capacity of the discharged oil is almost zero. When the hydraulic pump cannot absorb, a sudden braking force is generated in the hydraulic motor, causing the vehicle to stop suddenly regardless of the driver's intention, and an excessive torque is generated in the traveling drive system. There is a risk of damage to equipment.
[0009]
  If the circuit pressure rises excessively, the overload relief valve opens to bypass the variable displacement hydraulic pump and circulate the discharge oil of the hydraulic motor to the inflow side of the hydraulic motor. Since a rapid temperature rise occurs in a relief valve or the like, the oil whose temperature has risen due to this flows into the hydraulic motor, which may cause motor seizure or damage to seals.
[0010]
  In view of such circumstances, the present invention effectively suppresses the occurrence of inconveniences such as sudden braking and damage to equipment due to abnormality in displacement operation of a variable displacement hydraulic pump in a travel drive device having an HST. For the purpose.
[0011]
[Means for Solving the Problems]
  As a means for solving the above-mentioned problems, the present invention comprises a variable displacement hydraulic pump driven by a prime mover and a closed circuit including a hydraulic motor coupled to a traveling wheel of a vehicle, and the variable circuit In the hydraulic travel drive apparatus having a capacity operation means for changing the capacity of the capacity type hydraulic pump, the capacity operation means includes a regulator for operating the capacity of the variable capacity hydraulic pump by receiving supply of oil pressure, A hydraulic pressure supply source for supplying hydraulic pressure to the regulator, an allowable position that is interposed between the hydraulic pressure supply source and the regulator, and allows the supply of hydraulic pressure from the hydraulic pressure supply source to the regulator as the switching position; An electromagnetic switching valve having a shut-off position for shutting off the supply of hydraulic pressure, and a switching operation for inputting the command signal to the electromagnetic switching valve. And a manipulation unit, and the electromagnetic switching valve, detent-type electromagnetic switching valve der to retain the operating position when the input of the command signal is interruptedAnd a connection release means for releasing the connection between the hydraulic motor and the traveling wheel when the switching operation means is generating a command signal for setting the detent type electromagnetic switching valve to a shut-off position for the detent type electromagnetic switching valve. WithIs.
[0012]
  According to this device, even if the input of the command signal to the detent type electromagnetic switching valve is interrupted, the operation position of the switching valve is maintained at the current position, so that the pump capacity is reduced due to an abnormal input of the command signal. Sudden changes are prevented and inconveniences caused by this are avoided.
[0013]
  ThisIn this device, when the input of the command signal is interrupted while the switching valve is switched to the allowable position, the switching valve cannot be returned to the neutral position by the operation of the driver.ButIn addition to the switching operation means, a connection release means for releasing the connection between the hydraulic motor and the traveling wheel when the switching operation means is generating a command signal for causing the switching valve to be in a shut-off position. WithTherefore, inconvenience due to failure of the electrical system is prevented in advance.
[0014]
  The regulator has a forward port and a reverse port, and when the hydraulic pressure is supplied to the forward port, the capacity of the variable displacement hydraulic pump is increased forward by an amount corresponding to the hydraulic pressure, and the reverse port is When the supply of hydraulic pressure increases the displacement of the variable displacement hydraulic pump by the amount corresponding to the hydraulic pressure, the displacement operating means serves as the detent electromagnetic switching valve as the hydraulic supply A first electromagnetic switching valve that is switchable between a forward position that allows the supply of hydraulic pressure from the power source to the forward port and a reverse position that blocks the supply of hydraulic pressure from the hydraulic pressure supply source to the reverse port; The solenoid switch valve is arranged in series with the allowable position for allowing the hydraulic pressure supply from the hydraulic pressure supply source to the regulator and the hydraulic pressure from the hydraulic pressure supply source to the regulator. A second electromagnetic switching valve that can be switched to a cutoff position that cuts off the supply, and the switching operation means switches the first electromagnetic switching valve to the forward position during forward running and the second electromagnetic switching valve. The hydraulic pressure is supplied from the hydraulic pressure supply source to the forward port by switching the first electromagnetic switching valve to the reverse position and the second electromagnetic switching valve is set to the allowable position during reverse travel. Accordingly, the hydraulic pressure supply source may supply hydraulic pressure to the reverse port, and the capacity operation unit may allow the hydraulic pressure supply from the hydraulic supply source to the forward port as the detent type electromagnetic switching valve. A forward electromagnetic switching valve that is switchable between an allowable position and a shut-off position that interrupts the supply of hydraulic pressure from the hydraulic pressure supply source to the forward port, and the forward electromagnetic switching valve is arranged in parallel, A reverse electromagnetic switching valve that is switchable between a permissible position that allows the supply of hydraulic pressure from the pressure supply source to the reverse port and a blocking position that blocks the supply of hydraulic pressure from the hydraulic supply source to the reverse port; The switching operation means supplies the hydraulic pressure from the hydraulic supply source to the forward port by switching the forward electromagnetic switching valve to a permissible position and setting the reverse electromagnetic switching valve to a cutoff position during forward traveling, When traveling, the hydraulic switching valve may be switched from the hydraulic supply source to the reverse port by switching the forward electromagnetic switching valve to the cutoff position and setting the reverse electromagnetic switching valve to the allowable position.
[0015]
  In the above apparatus, it is more preferable that the switching abnormality detection means outputs a warning signal to the warning device when the abnormality is detected.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
  First, a reference example of the present invention will be described with reference to FIGS.
[0017]
  FIG. 1 shows a schematic configuration of a vehicle equipped with the hydraulic travel drive apparatus according to the reference example. The vehicle includes a prime mover 12 whose rotational speed increases in conjunction with an accelerator pedal 10, and the power of the prime mover 12 is supplied to a working hydraulic pump 16 via a power distributor 14 and a variable displacement hydraulic pump 18. And supplied to the capacity-operating hydraulic pump 20. Accordingly, the discharge flow rates of the hydraulic pumps 16, 18, and 20 increase as the rotational speed of the prime mover 12 increases.
[0018]
  The variable displacement hydraulic pump 18 forms a closed circuit (HST circuit) together with the hydraulic motor 26. In this reference example, the variable displacement hydraulic pump 18 and the hydraulic motor 26 can operate in both directions, and one port of the variable displacement hydraulic pump 18 is connected to one of the hydraulic motors 26 via the conduit 22. The other port of the hydraulic motor 26 is connected to the other port of the variable displacement hydraulic pump 18 via a conduit 24. When hydraulic oil is discharged from the variable displacement hydraulic pump 18 to the pipeline 22 side, the hydraulic motor 26 rotates in the vehicle forward direction. Conversely, when hydraulic oil is discharged from the pump 18 to the pipeline 24 side. The hydraulic motor 26 rotates in the vehicle reverse direction.
[0019]
  The output shaft of the hydraulic motor 26 is connected to the traveling wheel 30 via a transmission 28. The transmission 28 is shown in a neutral state shown in FIG. 2 (a), a low-speed shift state shown in FIG. 2 (b), and in FIG. 2 (c) according to a shift command signal inputted from the outside. It is possible to switch to three states, i.e., a high speed shift state.
[0020]
  Specifically, the transmission 28 includes an input shaft 28 a connected to the output shaft of the hydraulic motor 26 and an output shaft 28 b connected to the traveling wheel 30, and both shafts 28 a and 28 b are parallel to each other. It is arranged. A small-diameter low-speed gear 50L and a large-diameter high-speed gear 50H are attached to the input shaft 28a so as to be rotatable relative to the input shaft 28a, and the output shaft 28b is connected to the low-speed gear. A low speed gear 51L meshed with the gear 50L and a high speed gear 51H meshed with the high speed gear 50H are fixed so as to rotate integrally with the output shaft 28b.
[0021]
  A clutch drum 52 is fixed to the input shaft 28a so as to rotate integrally with the input shaft 28a. A low-speed clutch is provided between the clutch drum 52 and the low-speed gear 50L and the high-speed gear 50H. A cylinder 53L and a high-speed clutch cylinder 53H are interposed. When no command signal is input to any of the clutch cylinders 53L, 53H, the clutch drum 52 and the gears 50L, 50H are separated from each other by keeping the cylinders 53L, 53H contracted, and the input shaft 28a and the output shaft When the command signal is input to the low speed clutch cylinder 53L, only the cylinder 53L expands to connect the clutch drum 52 and the low speed gear 50L. By connecting, the rotation of the input shaft 28a is transmitted to the output shaft 28b via the low-speed gears 50L and 51L (low-speed gear shifting state in FIG. 5B), and a command signal is input to the high-speed clutch cylinder 53H. When this is done, only the cylinder 53H extends to connect the clutch drum 52 and the high speed gear 50H. Rotation of the input shaft 28a is adapted to be transmitted to the output shaft 28b through gears for high gear 50H, the 51H by (high gear shifting state in FIG (c)).
[0022]
  In FIG. 1, the pipes 22 and 24 are connected to the primary side of the low-pressure relief valve 34 via an overload relief valve 32 with a check valve, respectively, and the secondary side of the low-pressure relief valve 34 is connected to the tank. When the pressure in the pipe line 22 or the pipe line 24 reaches a predetermined allowable pressure, the overload relief valve 32 on the pipe line side opens, and the check valve in the overload relief valve 32 and the other overload relief valve The maximum pressure of the circuit is regulated by opening the pipes 22 and 24 through the.
[0023]
  The pump displacement of the variable displacement hydraulic pump 18 is operated by a displacement operation means 40. The capacity operating means 40 includes a regulator 38, a three-position electromagnetic switching valve 36, a high pressure supply source 42, an electromagnetic proportional pressure reducing valve 44, a shuttle valve 46, a controller 60, and the capacity operating hydraulic pump 20. Is included.
[0024]
  The regulator 38 is supplied with hydraulic pressure from the outside, and increases the pump capacity of the variable displacement hydraulic pump 18 as the hydraulic pressure increases according to the supply direction. Specifically, when hydraulic pressure is supplied from the right port in FIG. 1, the pump capacity of the variable displacement hydraulic pump 18 is increased forward by an amount corresponding to the hydraulic pressure, and when hydraulic pressure is supplied from the left port in FIG. The variable displacement hydraulic pump 18 is configured to increase the pump capacity to the reverse side by an amount corresponding to the hydraulic pressure.
[0025]
  The high-pressure supply source 42 only needs to output a predetermined hydraulic pressure, and a hydraulic pump dedicated to the supply source may be installed. For example, the working hydraulic pump 16 may be used as the high-pressure supply source 42. Is possible. The constant hydraulic pressure output from the high pressure supply source 42 is input to the regulator 38 via the electromagnetic proportional pressure reducing valve 44, the shuttle valve 46, and the electromagnetic switching valve 36. The shuttle valve 46 is connected to the oil outflow side of the displacement operation hydraulic pump 20 via a throttle 47 and a pressure reducing valve 48.
[0026]
  The electromagnetic proportional pressure reducing valve 44 outputs a secondary pressure proportional to the command signal input from the controller 60, and the throttle 47 and the pressure reducing valve 48 from the secondary pressure and the capacity operating hydraulic pump 20. Among the hydraulic pressures output through the high pressure, the higher one is selected by the shuttle valve 46 and guided to the electromagnetic switching valve 36.
[0027]
  In the present invention, the hydraulic pressure supply source for the displacement operation of the variable displacement hydraulic pump 18 is not particularly limited. For example, the hydraulic pressure is supplied to the regulator 38 only from the electromagnetic proportional pressure reducing valve 44 or only from the displacement operation hydraulic pump 20. It may be supplied.
[0028]
  The electromagnetic switching valve 36 is output from the shuttle valve 46 in a neutral position (blocking position; central position in FIG. 1) that blocks between the shuttle valve 46 and the regulator 38 in response to a command signal input from the controller 60. The forward position (right position in the figure) for guiding the hydraulic pressure to be supplied to the forward side port (right port in the figure), and the hydraulic pressure output from the shuttle valve 46 is the reverse port (regarding the figure). Is switched to the reverse position (left position in the figure). That is, the direction of travel drive (forward and reverse) is switched by switching the position of the electromagnetic switching valve 36.
[0029]
  Specifically, a spring center type three-position electromagnetic switching valve is used as the electromagnetic switching valve 36. When one solenoid 36f is excited, the electromagnetic switching valve 36 is switched to the forward position, and the other solenoid 36b is excited. When the two solenoids 36f and 36b are not excited, they are held at the neutral position by the force of the spring.
[0030]
  The controller 60 is connected to a prime mover rotational speed sensor 54, a vehicle speed sensor 56, a shift lever device 58, and the like, and based on electrical signals inputted from these, the switching control of the electromagnetic switching valve 36 and the shift stage switching of the transmission 28 are performed. Take control.
[0031]
  Specifically, the controller 60 includes a command signal creation unit 62, an abnormality determination unit 64, and a transmission operation unit 66 as shown in FIG.
[0032]
  The command signal generator 62 outputs a command signal to the electromagnetic switching valve 36 based on the shift lever position operated by the shift lever device 58 and switches its position.
[0033]
  Specifically, the command signal generator 62 includes a relay contact 62a and a relay coil 62b provided for each solenoid 36f, 36b of the electromagnetic switching valve 36 (however, only one relay contact 62a and relay coil 62b are shown in FIG. 3). ) And a command switching unit 62c.
[0034]
  The relay contact 62a is a normally open contact, and is interposed between a predetermined power source and the solenoid 36f (36b) together with the circuit protection fuse 37, and when the relay coil 62b adjacent to the relay contact 62a is energized. Only closed by its magnetic force.
[0035]
  The command switching unit 62 c is configured to energize an appropriate relay coil 62 b depending on the lever position of the shift lever device 58. Specifically, when the lever position is the forward position, a command signal for energizing the solenoid 36f by energizing the relay coil 62b corresponding to the solenoid 36f is created, and when the lever position is the reverse position, the solenoid 36b A command signal for energizing the solenoid 36b is generated by energizing the relay coil 62b corresponding to, and when the lever position is in the neutral position, no relay coil 62b is energized (that is, no command signal is generated). It is configured.
[0036]
  The command signal generator 62 may use a non-contact circuit using a transistor or the like instead of the relay switch as shown. Whether or not to provide a circuit protection element at the time of a short circuit is an arbitrary matter, and a circuit protection unit using a transistor or the like may be constructed in place of the fuse 37 as described above.
[0037]
  The abnormality determination unit 64 monitors the potentials of the solenoids 36f and 36b, the actual energization status of the solenoids 36f and 36b, the energization status of the relay coil 62b by the command switching unit 62c (that is, the command signal creation status), and When the two do not correspond to each other, it is determined that there is an abnormality and an abnormality determination signal is output to the transmission operation unit 66 (details will be described later), and a warning device (for example, a warning light or alarm device) provided in the vehicle interior ) 55 outputs a warning signal to cause a warning.
[0038]
  The transmission operation unit 66 outputs a command signal to the transmission 28 to change the speed of the transmission. Normally, the transmission operation unit 66 selects a shift position according to the driving state of the vehicle, the downshift operation of the shift lever device 58, and the like. The transmission 28 is controlled so that the transmission 28 is forcibly switched to the neutral state when an abnormality determination signal is input from the abnormality determination unit 64.
[0039]
  The controller 60 also has a role of performing a displacement operation of the variable displacement hydraulic pump 18. Specifically, the controller 60 calculates a command pressure corresponding to the rotational speed detected by the prime mover rotational speed sensor 54, A command signal corresponding to the command pressure is output to the electromagnetic proportional pressure reducing valve 44 and the secondary pressure is adjusted to the command pressure.
[0040]
  The command pressure calculated by the controller 60 is not limited to the pressure corresponding to the rotational speed detected by the prime mover rotational speed sensor 54, and may be a command pressure corresponding to the operation amount of the accelerator pedal, for example. Further, it goes without saying that the control of the controller 60 can be omitted when the regulator 38 is operated only by the discharge oil of the displacement operation hydraulic pump 20.
[0041]
  As described above, the displacement operating hydraulic pump 20 has a discharge pressure that increases as the rotational speed of the prime mover 14 increases. A shuttle valve 46 passes through the throttle 47 and the pressure reducing valve 48 from the hydraulic pump 20. The characteristic of the pressure input to the pressure is equal to or less than the command pressure of the electromagnetic proportional pressure reducing valve 44 in the entire rotational speed region.
[0042]
  A part of the discharge oil of the capacity-operating hydraulic pump 20 is distributed to the pipelines 22 and 24 through the check valves of the overload relief valves 32 with the check valves. Provided for cooling.
[0043]
  Next, the operation of this apparatus will be described with reference to the flowchart of FIG.
[0044]
  When the accelerator pedal 10 is depressed, the rotational speed of the prime mover 12 increases in accordance with the depression, and the rotational speeds of the variable displacement hydraulic pump 18 and the displacement operation pump 20 increase accordingly.
[0045]
  When the lever position is switched to the forward position (YES in step S1 in FIG. 4), the command signal creating unit 62 of the controller 60 creates a signal for exciting the solenoid 36f of the electromagnetic switching valve 36 (step). S2). At this time, if there is no abnormality in the electrical system such as the cable line, the command signal is input to the solenoid 36f (YES in step S3), so that the electromagnetic switching valve 36 is moved forward (right position in FIG. 1). The hydraulic pressure output from the shuttle valve 46 is input to the forward port (the right port in FIG. 1) of the regulator 38. Receiving this, the regulator 38 increases the capacity of the variable displacement hydraulic pump 18 in the forward direction. By this displacement operation, the hydraulic oil is discharged from the variable displacement hydraulic pump 18 to the hydraulic motor 26 through the pipeline 22, and the traveling wheel connected to the output shaft of the hydraulic motor 26 and the output shaft via the transmission 28. 30 rotates in the forward direction.
[0046]
  Here, when there is no abnormality in the electromagnetic proportional pressure reducing valve 44, the secondary pressure is always maintained at a pressure higher than the hydraulic pressure input from the capacity-operating hydraulic pump 20 to the shuttle valve 46. The hydraulic pressure output from the electromagnetic proportional pressure reducing valve 44 is selected at a high level and is guided to the regulator 38. When the electromagnetic proportional pressure reducing valve 44 cannot output a normal secondary pressure due to a failure of the solenoid or the like, the hydraulic pressure on the variable displacement hydraulic pump 20 side is selected at a high level by the shuttle valve 46 and guided to the regulator 38. As a result, normal capacity operation is guaranteed.
[0047]
  Conversely, when the lever position is switched to the reverse position (NO in step S1 and YES in step S6), the command signal creation unit 62 of the controller 60 creates a signal for exciting the solenoid 36b of the electromagnetic switching valve 36. (Step S7). At this time, if there is no abnormality in the electrical system such as the cable line, the command signal is input to the solenoid 36b (YES in step S8), and the electromagnetic switching valve 36 is moved to the reverse position (left position in FIG. 1). The hydraulic pressure output from the shuttle valve 46 is switched to the reverse port (left port in FIG. 1) of the regulator 38, and finally the traveling wheel 30 rotates in the reverse direction.
[0048]
  As described above, when the command signal created by the command signal creation unit 62 of the controller 60 is normally input to the solenoid 36f or 36b (YES in step S3 in FIG. 4 or YES in step S8), The abnormality determination unit 64 of the controller 60 does not output an abnormality determination signal, so that the transmission operation unit 66 outputs to the transmission 28 a shift command corresponding to the shift position determined by the current driving state (step S4). . The same applies when the shift lever is operated to the neutral position (NO in step S1 and NO in step S6).
[0049]
  On the other hand, the command signal is actually input to the solenoid 36f or 36b due to a failure of the electric system or the like, even though the command signal for exciting the solenoid 36f or 36b is generated in the command signal generator 62. If not (NO in step S3 or NO in step S8), the transmission operation unit 66 outputs a neutral command to the transmission 28 regardless of the current shift position, thereby indicating the transmission 28 in FIG. Is forcibly switched to the neutral state (step S5). Thereby, the input shaft 28a and the output shaft 28b of the transmission 28 are disconnected, and the connection between the output shaft of the hydraulic motor 26 and the traveling wheel 30 is released. Such disconnection prevents inconvenience due to a failure of the electrical system in advance.
[0050]
  That is, when a cable disconnection or the like occurs during the forward travel or reverse travel and the command signal to the solenoid 36f or solenoid 36b of the electromagnetic switching valve 36 is suddenly interrupted, the electromagnetic switching valve 36 is automatically activated by the action of the spring. Therefore, the position is switched to the neutral position (the position where the regulator 38 and the shuttle valve 46 are shut off), and the capacity of the variable displacement hydraulic pump 18 becomes zero or a value close thereto, and the pump 18 is in a block state. In this state, when the hydraulic motor 26 continues to rotate at high speed together with the traveling wheels 30 due to the inertia of the vehicle, the discharge side (oil outflow side) pressure of the hydraulic motor 26 suddenly increases to generate a brake pressure, thereby generating the vehicle pressure. Although this may cause a sudden stop or damage to each device, in this device, the controller 60 detects the abnormality. To decouple the hydraulic motor 26 forcibly switched to the neutral of the transmission 28 at the time of from road wheels 30, it is possible to effectively suppress sudden stop or inconvenience damage to the equipment of the vehicle.
[0051]
  In the present invention, the transmission 28 is not limited to the release of the connection between the hydraulic motor 26 and the traveling wheel 30, and a device that does not include a transmission capable of changing the gear position between the two is, for example, Instead of the transmission, a simple clutch may be interposed between the hydraulic motor 26 and the traveling wheel 30, and the clutch may be disconnected in an emergency.
[0052]
  Further, as means for detecting an operation abnormality of the electromagnetic switching valve 36, one using pressure detection means (for example, a pressure switch or a pressure sensor) for detecting a secondary pressure of the electromagnetic switching valve 36 is more preferable. If such a pressure detecting means is used, it is possible to cope with an abnormality of the electromagnetic switching valve 36 itself or the hydraulic pressure supply source.
[0053]
  An example is shown in FIG. The illustrated pressure switch 59 is provided between the electromagnetic switching valve 36 and the forward port and the reverse port of the regulator 38, respectively, and the pressure of the hydraulic oil actually supplied to these ports (that is, the electromagnetic switching valve 36). The pressure switch 59 is turned on only when the secondary pressure is equal to or higher than a certain level. By turning on / off the pressure switch 59, it is possible to determine whether or not the electromagnetic switching valve 36 is actually operating normally. .
[0054]
  Specifically, FIG. 6 shows the control operation of the controller 60 when this pressure switch 59 is used. In the figure, when the shift lever is switched to the forward position (YES in step S1) and a command signal for exciting the solenoid 36f is generated in response thereto (step S2), the abnormality determination unit 64 of the controller 60 is controlled by the regulator 38. It is confirmed whether or not the pressure switch 59 provided on the forward port side is ON (step S3 ').
[0055]
  Further, when the shift lever is switched to the reverse position (NO in step S1, YES in step S6), and in response to this, a command signal for exciting the solenoid 36b is created (step S7), the abnormality determination unit of the controller 60 64 confirms whether or not the pressure switch 59 provided on the reverse port side of the regulator 38 is on (step S8 ').
[0056]
  Here, if the corresponding pressure switch 59 is ON (YES in step S3 ′ or YES in step S8 ′), it is determined that the hydraulic pressure is normally supplied to the regulator 38, and thus an abnormality determination signal. Therefore, the transmission operation unit 66 outputs a command signal corresponding to the shift position to the transmission 28 (step S4). On the other hand, when the corresponding pressure switch 59 remains off (NO in step S3 ′ or NO in step S8 ′), the hydraulic pressure is normally supplied to the regulator 38 due to malfunction of the electromagnetic switching valve 36 or the like. Therefore, the abnormality determination signal is output, so that the transmission operation unit 66 outputs a neutral command to the transmission 28 to forcibly disconnect the hydraulic motor 26 and the traveling wheel 30 (step S5).
[0057]
  In the example shown in FIG. 6, abnormality determination is performed when the secondary pressure is equal to or less than a predetermined value regardless of the magnitude of the command signal. However, the command signal as in the apparatus shown in FIG. If the secondary pressure of the electromagnetic proportional pressure reducing valve 44 and the secondary pressure of the electromagnetic switching valve 36 are increased or decreased in response to the pressure, the secondary pressure of the electromagnetic switching valve 36 is replaced with the pressure switch 59. And a difference between a target secondary pressure to be generated on the secondary side of the electromagnetic switching valve 36 and a secondary pressure actually detected by the pressure sensor is constant according to the command signal. An abnormality determination may be made at the above time.
[0058]
  Further, instead of detecting the secondary pressure of the electromagnetic switching valve 36, for example, when the actual tilt angle of the variable displacement hydraulic pump 18 is detected and the tilt angle does not correspond to the command signal. It is also effective to perform abnormality determination.
[0059]
  Next, an apparatus for avoiding inconvenience due to malfunction of the electromagnetic switching valve 36 by the forced bypass of the variable displacement hydraulic pump 18 will be described with reference to FIGS. Of the components shown in FIGS. 7 and 8, the same components as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof is omitted.
[0060]
  In this apparatus, a bypass oil passage 70 that bypasses the variable displacement hydraulic pump 18 and connects both the conduits 22, 24 is provided between the conduits 22, 24, and in the middle of the bypass oil passage 70. A bypass switching valve 72 is provided. The bypass switching valve 72 is constituted by a two-position electromagnetic switching valve in the illustrated example, and when the excitation signal is not input to the solenoid, the bypass switching valve 72 is switched to a blocking position that blocks the bypass oil passage 70 and the excitation signal is input. Only at times is it possible to switch to the opening position for opening the bypass oil passage 70.
[0061]
  On the other hand, the controller 60 includes a bypass operation unit 68 as shown in FIG. Only when an abnormality determination signal is input from the abnormality determination unit 64, the bypass operation unit 68 inputs an excitation signal to the solenoid of the bypass switching valve 72 to move the bypass switching valve 72 from the shut-off position to the open position. To switch.
[0062]
  The control operation by this controller 60 is shown in FIG. The normal operation is the same as that shown in FIG. That is, when the shift lever is operated to the forward position (YES in Step S1), a signal for exciting the solenoid 36f is created (Step S2), and it is confirmed whether or not the signal is input to the solenoid 36f (Step S3). ). Similarly, when the shift lever is operated to the reverse position (NO in step S1, YES in step S6), a signal for exciting the solenoid 36b is created (step S7), and whether or not the signal is input to the solenoid 36b. Is confirmed (step S8).
[0063]
  Here, when the signal is normally input to the solenoid 36f or the solenoid 36b (YES in step S3 or YES in step S8), the bypass switching valve 72 is not particularly operated, and is kept at the blocking position. Therefore, in this case, the HST operates as usual. On the other hand, when a signal is not normally input to the solenoid 36f or 36b, that is, when an abnormality determination is made (NO in step S3 or NO in step S8), an excitation signal is output to the bypass switching valve 72. Then, this is switched to the open position (step S5 '). As a result, the bypass oil passage 70 is opened, and the inflow side and the outflow side of the hydraulic motor 26 are directly passed by bypassing the variable displacement hydraulic pump 18. Therefore, even if the electromagnetic switching valve 36 unexpectedly returns to the neutral position due to a failure in the electrical system and the capacity of the variable displacement hydraulic pump 18 suddenly decreases, the hydraulic oil flowing out of the hydraulic motor 26 passes through the bypass oil passage 70. By letting it escape to the motor inflow side as it is, it is possible to avoid inconveniences such as occurrence of sudden braking and damage to equipment due to excessive rise in circuit pressure.
[0064]
  In any of the above-described devices, the hydraulic pressure supply to the regulator 38 is switched, that is, the direction of the tilt angle of the variable displacement hydraulic pump 18 is switched using the spring center type electromagnetic switching valve 36. Therefore, when the command signal to be input to the electromagnetic switching valve 36 is not input, the electromagnetic switching valve 36 returns to the neutral position. In the present invention, the command signal is used as the switching valve for performing the switching. By using a switching valve having a function of holding the current operation position when not inputted, specifically a detent type electromagnetic switching valve, even if the command signal is not inputted due to a failure of the electric system, At that time, the inconvenience that the electromagnetic switching valve suddenly returns to the neutral position can be avoided.
[0065]
  However, since the detent type electromagnetic switching valve is generally in a two-positioned position (not in three positions) with solenoids for position switching at both ends thereof, the detent type electromagnetic switching valve can be moved forward / When switching between neutral and reverse, a plurality of electromagnetic switching valves must be used in combination.
[0066]
  An example of the apparatus is shown in FIGS. In FIG. 2A, a first electromagnetic switching valve 82 and a second electromagnetic switching valve 84 are arranged in series between the regulator 38 and the shuttle valve 46, and other than these electromagnetic switching valves 82, 84. The configuration is exactly the same as that shown in FIG.
[0067]
  As the electromagnetic switching valves 82 and 84, detent type two-position electromagnetic switching valves are used. Among these, the first electromagnetic switching valve 82 on the side close to the regulator 38 has solenoids 82a and 82b at both ends thereof, and the second electromagnetic switching valve 84 on the side near the shuttle valve 46 has solenoids 84a on both ends thereof. 84b, and both electromagnetic switching valves 82 and 84 are provided with known means (detent mechanism 80 in the figure) for holding the current operation position when neither solenoid is excited. ing.
[0068]
  When the solenoid 84a is energized, the second electromagnetic switching valve 84 communicates both the forward port and the reverse port of the regulator 38 to the tank regardless of the operation position of the electromagnetic switching valve 82, and is connected to the tank 46 from the shuttle valve 46. When the solenoid 84b is energized while switching to the neutral position (blocking position; left position in the figure) that blocks the hydraulic pressure supply, one port of the regulator 38 is used as the shuttle valve 46 and the other port is used as the tank. The connection position (allowable position; right position in the figure) is switched.
[0069]
  When the solenoid 82a is energized, the first electromagnetic switching valve 82 guides the hydraulic pressure supplied from the second electromagnetic switching valve 84 in the communication position to the forward port side and communicates the reverse port side to the tank. When the solenoid 82b is energized, the hydraulic pressure supplied from the electromagnetic switching valve 84 at the communication position is guided to the reverse port side, and the forward port side is used as a tank. It is switched to the reverse position (the left position in the figure) that communicates.
[0070]
  On the other hand, the controller (equivalent to the controller 60 shown in FIG. 1 and the like) performs a control operation as shown in FIG. 10B according to the operation position of the shift lever.
[0071]
  That is, when the shift lever is switched to the forward position (YES in step S11), the controller 60 excites only the solenoids 82a and 84b in the electromagnetic switching valves 82 and 84 and de-energizes the solenoids 82b and 84a (step S11). S12). As a result, the second electromagnetic switching valve 84 is switched to the right position in FIG. 10A and the first electromagnetic switching valve 82 is switched to the left position in FIG. While being supplied to the forward port, the reverse port of the regulator 38 is communicated with the tank.
[0072]
  On the other hand, when the shift lever is switched to the reverse position (NO in step S11, YES in step S13), the controller 60 excites only the solenoids 82b and 84b in the electromagnetic switching valves 82 and 84, thereby energizing the solenoids 82a and 84a. Is not excited (step S14). As a result, both the electromagnetic switching valves 84 and 82 are switched to the right position in FIG. 10A, and the hydraulic pressure output from the shuttle valve 46 is supplied to the reverse port of the regulator 38, and the forward port of the regulator 38 is Connected to the tank.
[0073]
  When the shift lever is switched to the neutral position (NO in steps S11 and S13), the controller 60 excites only the solenoid 84a of the second electromagnetic switching valve 84 and the other solenoids 82a, 82b, and 84b are inactive. Excitation is performed (step S14). Accordingly, the second electromagnetic switching valve 84 is switched to the left position in FIG. 10A, and both ports of the regulator 38 are communicated with the tank regardless of the position of the first electromagnetic switching valve 82, so that the variable displacement hydraulic pressure can be obtained. The pump capacity of the pump 18 is almost zero.
[0074]
  When two detent type electromagnetic switching valves are used in combination, these electromagnetic switching valves are arranged in parallel between the variable displacement hydraulic pump 18 and the hydraulic supply side (shuttle valve 46 in the example). However, if switching between forward, neutral and reverse, a plurality of electromagnetic switching valves must be used in combination.
[0075]
  An example of the apparatus is shown in FIGS. Of the electromagnetic switching valves 86 and 88 shown in FIG. 5A, the electromagnetic switching valve 88 is a forward electromagnetic switching valve interposed between the shuttle valve 46 and the forward port of the regulator 38, and the electromagnetic switching valve 86 is a shuttle. This is a reverse electromagnetic switching valve interposed between the valve 46 and the reverse port of the regulator 38.
[0076]
  The electromagnetic switching valve 88 has solenoids 88a and 88b at both ends thereof, and when the solenoid 88a is energized, the hydraulic pressure supplied from the shuttle valve 46 is blocked and the advance port communicates with the tank (the left side in the figure). When the solenoid 88b is energized, it is switched to a permissible position (right position in the figure) that allows the hydraulic pressure supply from the shuttle valve 46 to the forward port. Similarly, the electromagnetic switching valve 86 has solenoids 86a and 86b at both ends thereof, and when the solenoid 86a is excited, the hydraulic pressure supplied from the shuttle valve 46 is blocked and the reverse port communicates with the tank. When the solenoid 86b is energized, it is switched to a permissible position (right position in the figure) that allows hydraulic pressure supply from the shuttle valve 46 to the reverse port.
[0077]
  The controller (equivalent to the controller 60 shown in FIG. 1 and the like) performs a control operation as shown in FIG. 11B in accordance with the operation position of the shift lever.
[0078]
  That is, when the shift lever is switched to the forward position (YES in step S11), the controller 60 excites only the solenoids 86a and 88b in the electromagnetic switching valves 86 and 88 and deenergizes the solenoids 86b and 88a (step S11). S12 '). As a result, the electromagnetic switching valve 88 is switched to the right position in FIG. 10A and the electromagnetic switching valve 86 is switched to the left position in FIG. 10, and the hydraulic pressure output from the shuttle valve 46 is supplied to the forward port of the regulator 38. At the same time, the reverse port of the regulator 38 is communicated with the tank.
[0079]
  On the other hand, when the shift lever is switched to the reverse position (NO in step S11, YES in step S13), the controller 60 excites only the solenoids 86b and 88a in the electromagnetic switching valves 86 and 88 to excite the solenoids 86a and 88b. Is de-energized (step S14 '). As a result, the electromagnetic switching valve 88 is switched to the left position in FIG. 10A and the electromagnetic switching valve 86 is switched to the right position in FIG. 10, and the hydraulic pressure output from the shuttle valve 46 is supplied to the reverse port of the regulator 38. At the same time, the forward port of the regulator 38 is communicated with the tank.
[0080]
  When the shift lever is switched to the neutral position (NO in steps S11 and S13), the controller 60 excites only the solenoids 86a and 88a in the electromagnetic switching valves 86 and 88 and deenergizes the solenoids 86b and 88b. (Step S14 '). As a result, both the electromagnetic switching valves 88 and 86 are switched to the left position in FIG. 10A, both ports of the regulator 38 are connected to the tank, and the pump displacement of the variable displacement hydraulic pump 18 becomes substantially zero.
[0081]
  As described above, according to the apparatus shown in FIGS. 10 and 11, even if the input of a command signal to a specific solenoid suddenly stops due to a failure in the electrical system or the like, the detent mechanism 80 provided in each electromagnetic switching valve. Thus, the current valve position is maintained, so that the inconvenience caused by unexpectedly returning the operation position to the neutral position is surely avoided. This is particularly effective when the speed reducer does not have a speed change mechanism, and has the advantage that acceleration and deceleration by the accelerator can be continued.
[0082]
  However, in that case, even if the driver operates the shift lever, the electromagnetic switching valve cannot be returned to the neutral position. Therefore, when the command signal is generated by the controller 60, for example, the transmission 28 shown in FIG. Thus, the controller 60 is configured to forcibly release the connection between the hydraulic motor 26 and the traveling wheel 30 (that is, the controller 60 and the transmission 28 function as connection release means in the apparatus shown in FIG. 1).Just do.
[0083]
  When the reverse speed mode is included in the shift stage of the transmission 28, it is not necessary to switch between forward and reverse on the regulator 38 side, and the regulator 38 having only the forward port is used. Is possible. In that case, the switching valve interposed between the regulator 38 and the hydraulic pressure supply source may be two-positioned, and for example, the detent type electromagnetic switching valve can be used as it is.
[0084]
  Further, the switching valve interposed between the regulator 38 and the hydraulic pressure supply source is not limited to an electromagnetic switching valve, and for example, a pilot switching valve or a manual switching valve may be used.
[0085]
【The invention's effect】
  As described above, according to the present invention, in a hydraulic travel drive apparatus in which a closed circuit is configured by a variable displacement hydraulic pump and a hydraulic motor, when an abnormality occurs in the displacement operation of the variable displacement hydraulic pump. By configuring the switching valve in the capacity operation means with a detent type electromagnetic switching valve having a self-holding function of the valve device, it is possible to effectively suppress the occurrence of sudden braking and damage to the equipment at the time of the abnormality.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram showing an overall configuration of a hydraulic traveling drive apparatus according to a reference example of the present invention.
FIGS. 2A and 2B are skeleton diagrams of a transmission provided in the hydraulic travel drive device, where FIG. 2A is a neutral state, FIG. 2B is a low speed shift state, and FIG. 2C is a high speed shift state; is there.
FIG. 3 is a circuit diagram showing a configuration of a controller provided in the hydraulic travel drive device.
FIG. 4 is a flowchart showing a control operation of the controller.
FIG. 5 is a circuit diagram showing a configuration of a controller when a pressure switch is used as an abnormality detection means.
6 is a flowchart showing a control operation of the controller shown in FIG.
FIG. 7 is a hydraulic circuit diagram showing an overall configuration of a hydraulic travel drive device according to a reference example of the present invention and having a bypass function.
8 is a circuit diagram showing a configuration of a controller provided in the apparatus shown in FIG.
FIG. 9 is a flowchart showing a control operation of the controller shown in FIG. 8;
FIG. 10 is a hydraulic circuit diagram showing an embodiment of the present invention, in which (a) is a hydraulic pressure in which two detent type electromagnetic switching valves are arranged in series as a switching valve interposed between a regulator and a hydraulic pressure supply source; The hydraulic circuit diagram which shows the example of a type travel drive device, (b) is a flowchart which shows the control operation performed in the device.
FIG. 11 is a hydraulic circuit diagram showing an embodiment of the present invention, in which (a) shows a hydraulic pressure in which two detent type electromagnetic switching valves are arranged in parallel as a switching valve interposed between a regulator and a hydraulic pressure supply source; The hydraulic circuit diagram which shows the example of a type travel drive device, (b) is a flowchart which shows the control operation performed in the device.
[Explanation of symbols]
  10 Accelerator pedal
  12 prime mover
  18 Variable displacement hydraulic pump
  20 Hydraulic pump for capacity operation
  22, 24 pipeline
  26 Hydraulic motor
  28 Transmission
  30 Traveling wheels
  36 Solenoid valve
  38 Regulator
  40 Capacity operation means
  42 High pressure hydraulic power source
  44 Proportional solenoid valve
  46 Shuttle valve
  55 Warning device
  59 Pressure switch (pressure detection means)
  60 controller
  62 Command signal generator
  64 Abnormality judgment part
  66 Transmission control unit
  68 Bypass operation section
  70 Bypass oil passage
  72 Bypass switching valve
  80 detent mechanism
  82, 84, 86, 88 Detent type solenoid valve

Claims (4)

A closed circuit including a variable displacement hydraulic pump driven by a prime mover and a hydraulic motor connected to a traveling wheel of the vehicle is configured, and a displacement operation means for changing the displacement of the variable displacement hydraulic pump is provided. In the hydraulic travel drive apparatus, the capacity operating means includes a regulator for operating the capacity of the variable displacement hydraulic pump by receiving supply of oil pressure, a hydraulic pressure supply source for supplying hydraulic pressure to the regulator, An electromagnetic switching valve that is interposed between a hydraulic pressure supply source and the regulator and has a permissible position that allows the hydraulic pressure supply from the hydraulic pressure supply source to the regulator as a switching position and a cutoff position that blocks the hydraulic pressure supply. And a switching operation means for performing a switching operation by inputting a command signal to the electromagnetic switching valve, and the electromagnetic switching valve Ri detent solenoid switching valve der to retain the operating position when the input command signal is interrupted, creating a command signal the is switching operation means to shut-off position the detent-type electromagnetic switching valve in the detent-type electromagnetic switching valve A hydraulic travel drive device comprising: a connection release means for releasing the connection between the hydraulic motor and the travel wheel when the vehicle is running. 2. The hydraulic travel drive apparatus according to claim 1 , wherein the regulator has a forward port and a reverse port, and the supply of hydraulic pressure to the forward port causes the variable displacement hydraulic pump by an amount corresponding to the hydraulic pressure. Increasing the capacity to the forward side, and receiving the supply of hydraulic pressure to the reverse port, the capacity of the variable displacement hydraulic pump is increased to the reverse side by an amount corresponding to the hydraulic pressure, the capacity operation means, The detent type electromagnetic switching valve can be switched between a forward position that allows the supply of hydraulic pressure from the hydraulic supply source to the forward port and a reverse position that blocks the supply of hydraulic pressure from the hydraulic supply source to the reverse port. A first electromagnetic switching valve, a permissible position arranged in series with the first electromagnetic switching valve, and allowing the supply of hydraulic pressure from the hydraulic supply source to the regulator; and the oil A second electromagnetic switching valve that can be switched to a shut-off position that shuts off the supply of hydraulic pressure from the supply source to the regulator, and the switching operation means sets the first electromagnetic switching valve to the forward position when traveling forward. The hydraulic pressure is supplied from the hydraulic pressure supply source to the forward port by switching and setting the second electromagnetic switching valve to a permissible position, while the first electromagnetic switching valve is switched to the reverse position and the second electromagnetic switch during reverse running. The hydraulic travel drive apparatus is characterized in that hydraulic pressure is supplied from the hydraulic supply source to the reverse port by setting the electromagnetic switching valve to an allowable position. 2. The hydraulic travel drive apparatus according to claim 1 , wherein the regulator has a forward port and a reverse port, and the supply of hydraulic pressure to the forward port causes the variable displacement hydraulic pump by an amount corresponding to the hydraulic pressure. Increasing the capacity to the forward side, and receiving the supply of hydraulic pressure to the reverse port, the capacity of the variable displacement hydraulic pump is increased to the reverse side by an amount corresponding to the hydraulic pressure, the capacity operation means, The detent type electromagnetic switching valve can be switched between a permissible position that allows the supply of hydraulic pressure from the hydraulic supply source to the forward port and a blocking position that blocks the supply of hydraulic pressure from the hydraulic supply source to the forward port. A forward electromagnetic switching valve, a permissible position that is arranged in parallel with the forward electromagnetic switching valve and allows the supply of hydraulic pressure from the hydraulic supply source to the reverse port and the hydraulic pressure A reverse electromagnetic switching valve that can be switched to a shut-off position that shuts off the supply of hydraulic pressure from the power source to the reverse port, and the switching operation means switches the forward electromagnetic switching valve to an allowable position during forward traveling and By setting the reverse electromagnetic switching valve to the shut-off position, hydraulic pressure is supplied from the hydraulic supply source to the forward port, while when moving backward, the forward electromagnetic switch valve is switched to the shut-off position and the reverse electromagnetic switch valve is A hydraulic travel drive apparatus characterized in that a hydraulic pressure is supplied from the hydraulic pressure supply source to the reverse port by setting to an allowable position. The hydraulic travel drive apparatus according to any one of claims 1 to 3 , wherein the switching abnormality detecting means outputs a warning signal to the alert apparatus when the abnormality is detected. .

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