FR2847635A1 - MOBILE VEHICLE AUTOMATIC TRANSMISSION DEVICE - Google Patents

Abstract

An automatic transmission device for a hydraulic mobile vehicle comprises transmission speed change control means (14), amount of depression detecting means for detecting an extent of depression of a pedal. accelerator (23A), charge pressure detecting means for detecting a charge pressure of a displacement pump (12) for supplying pressurized oil to a displacement motor (13), speed detection means of vehicle for detecting a vehicle speed of the hydraulic mobile vehicle, and a controller (30) which sends a downshift signal to the gearshift control means to downshift the transmission (14), when the detected load pressure is greater than or equal to a predetermined value, that the depth of depression detected is greater than or equal to a predetermined value, and that the hydraulic mobile vehicle is in a state of deceleration .

Description

MOBILE VEHICLE AUTOMATIC TRANSMISSION DEVICE

HYDRAULIC

  The present invention relates to an automatic transmission device for a hydraulic mobile vehicle.

  A transmission, which is mounted on an industrial vehicle which is a work vehicle, must cover a range of speeds from a range of low speeds from neutral for main operation to normal travel speed to travel on ordinary roads, and therefore it usually features multiple gear ratios as well

  for forward and reverse travel.

  An automatic transmission, which is capable of automatically selecting the optimum gear ratio as a function of the driving state of such a vehicle, is proposed, and, as means of detecting the displacement state, it adopts a sensor for vehicle speed which detects a vehicle travel speed, an acceleration opening degree sensor which detects an amount of depressing of an accelerator pedal, and the like (see, for example, Japanese Patent Left Open

  at the Public Inspection N0 5-223149).

  However, in a hydraulic mobile vehicle, it is effective to change a gear ratio of a transmission combined with a hydraulic motor according to a change in the load applied to a hydraulic pump and a hydraulic motor, and it is impossible to obtain an automatic transmission capable of automatically selecting an optimal speed ratio as a function of the driving condition of the hydraulic mobile vehicle using the technique described in Japanese Patent Left Open to the Public Inspection No 5-223149. In addition, the existing technique described above presents as problems the fact that it is expensive, and that it

  is prone to problems due to a complicated structure, making its maintenance difficult.

  The present invention is carried out in the light of the problems described above, and its object is to provide an automatic transmission device for a hydraulic mobile vehicle capable of automatically selecting an optimal speed ratio according to a

driving condition of the vehicle.

  To achieve the object described above, a first aspect of an automatic transmission device of a hydraulic mobile vehicle according to the present invention comprises * means for controlling the speed change of a transmission; charge pressure detecting means for detecting a charge pressure of a displacement pump for supplying pressurized oil to a displacement motor; vehicle speed detection means for detecting a vehicle speed of the hydraulic mobile vehicle; and a control device which sends a downshift signal to the speed change control means to make the transmission downshift, when the load pressure detected by the load pressure detection means is greater than or equal to a predetermined value, and that it is determined that the hydraulic mobile vehicle is in a state of

  deceleration as a function of the vehicle speed detected by the vehicle speed detection means.

  According to the above constitution, when the charge pressure of the displacement pump is greater than or equal to a predetermined value, and when the hydraulic motor vehicle is in the deceleration state, the transmission downshifts. As a result, in the hydraulic mobile vehicle constituting the work vehicle, the optimal speed ratio is automatically selected according to the driving condition of the vehicle, and it can move comfortably even on the road of travel with a high resistance to movement, such as a slope with a rise,

  without significantly reducing the speed of the vehicle.

  A second aspect of a automatic transmission device for a hydraulic mobile vehicle according to the present invention comprises: means for controlling the speed change of a transmission; means for detecting the depth of depression for detecting the extent of depression of an accelerator pedal, means for detecting charge pressure for detecting a charge pressure for a displacement pump for delivering pressurized oil to a displacement motor; vehicle speed detection means for detecting a vehicle speed of the hydraulic mobile vehicle; and a control device which sends a downshift signal to the speed change control means to make the transmission downshift, when the load pressure detected by the load pressure detection means is greater than or equal to a predetermined value, that the depth of penetration detected by the depth of penetration detection means is greater than or equal to a predetermined value, and that it is determined that the hydraulic mobile vehicle is in a state of deceleration as a function of the speed of vehicle

  detected by the vehicle speed detection means.

  According to the above constitution, when the charge pressure of the displacement pump is greater than or equal to a predetermined value, that the extent of depressing the accelerator pedal is greater than or equal to a predetermined magnitude, and that the hydraulic mobile vehicle is in the deceleration state, the transmission downshifts. As a result, in the hydraulic mobile vehicle constituting a work vehicle, the optimal speed ratio is automatically selected according to the driving state of the vehicle, and it can move comfortably even on the road of travel with great resistance to displacement, such

  only a slope with a climb, without considerably reducing the speed of the vehicle.

  In addition, in the automatic transmission device of the hydraulic mobile vehicle, the speed change control means can be a two-position switching valve. According to the constitution, the transmission speed change control means are constituted by a two-position switching valve with a simple structure at a low cost. As a result, the structure of the automatic transmission device of the hydraulic mobile device is simplified, and, consequently, the production cost of the automatic transmission device of the hydraulic mobile vehicle

can be reduced.

  In the automatic transmission device of the hydraulic mobile vehicle, the transmission can also consist of two stages of movement. According to

  constitution, cost reduction is made possible.

  In addition, as the charging pressure detection means described above are used, performances of the same level as those of the existing technique or

  of a level which presents no problem during practical use can be obtained in spite of an inexpensive constitution, such as a transmission with two speed ratios and a switching valve with two positions.

  The present invention will be better understood on reading

  of the following detailed description, made with reference

  to the accompanying drawings, in which: FIG. 1 is a general diagram of the system of an automatic transmission device according to one embodiment

of the present invention.

  An embodiment according to an automatic transmission of a hydraulic mobile device according to the present invention will be explained with reference to the drawing. Figure 1 is a general diagram of the system of an automatic transmission device. As shown in FIG. 1, a displacement pump 12 is connected to a motor 11, and the displacement pump 12 is driven by the motor 11 and discharges the oil under pressure. The pressurized oil, which is discharged from the displacement pump 12, is supplied to the displacement motor 13 via a displacement control valve 21 and an oil pressure swivel joint 15 The displacement motor 13 is connected to an input shaft (not shown) of a transmission

  14, and it drives the transmission 14.

  A displacement speed detection pump 17 is arranged at the level of the transmission 14, so that the displacement speed detection pump 17 rotates in proportion to the rotation of an output shaft of the transmission 14. An oil under pressure, which is discharged from the displacement speed detection pump 17, is supplied to a displacement speed detection motor 18 via the oil pressure swivel joint 15. The displacement pump 12 is a positive displacement hydraulic pump, and includes

  capacity control means 12C. The displacement motor 13 is a volumetric hydraulic motor, and comprises capacity control means 13C.

  A work vehicle (not shown) has lower displacement equipment (not shown) and an upper rotating superstructure (not shown), and includes working equipment (not shown) at the upper rotating structure, and includes the seal oil pressure swivel 15 at a

  connection part of the moving equipment

  and the upper rotating superstructure. The motor 11 and a control device 30 are arranged in the upper rotating superstructure, and the transmission 14 is arranged in the lower displacement equipment. The transmission 14 is connected to a speed change valve 16, which constitutes speed change control means, via the pivoting oil pressure seal 15. The speed change valve 16 delivers pressurized oil from a transmission pump 19 to a first speed clutch 14F or to a second speed clutch 14S by

  through the oil pressure swivel joint 15.

  The speed change valve 16 is a two position changeover valve with a simple structure and having a low cost, and switches between a first speed position 16A and a position of

  second speed 16B, as shown in FIG. 1, as a function of a speed change signal coming from the control device 30.

  The transmission 14 includes a planetary gear mechanism, and, depending on a pressure signal from the speed change valve 16, it applies pressure to the first speed clutch 14F for low speed or at low speed. second-speed clutch 14S for high speed, or releases the pressure thereof to effect a change of speed change ratio of the planetary gear mechanism, and engages or disengages it to establish the gear ratio. The first speed clutch 14F and the second speed clutch 14S are the clutches of a process for applying pressurized oil to engage the clutch and releasing the pressurized oil for disengaging the clutch. The 14 com35 transmission carries two gear ratios, namely the first and second gear ratios. When the transmission is put into first gear, the gear change valve 16 is put into the first gear position 16A, and the pressurized oil from the gear change valve 16 is applied to the first gear clutch 14F in order to engage the first speed clutch, and the pressurized oil from the second speed clutch 14S is released in order to disengage the second speed clutch 14S, whereby the transmission 14 is put in the first speed. When the transmission 14 is put into second gear, the gear change valve 16 is put into the second gear position 16B, and the pressurized oil from the gear change valve 16 is applied to the clutch. second speed 14S to engage the second speed clutch, and the pressurized oil from the first speed clutch 14F is released to disengage the first speed clutch 14F, whereby the transmission 14

is put in second gear.

  A vehicle speed detection device 35 for producing a vehicle speed signal is disposed at an output shaft of the vehicle speed detection motor 18, and rotates under the effect of the speed detection motor. vehicle 18. For example, a predetermined number of teeth, slots and protrusions and cavities are formed on an outer circumference of the vehicle speed detection device 35. A vehicle speed detection sensor 31 is disposed in close proximity of the outer circumference of the positive vehicle speed detection device 35, and outputs pulses, which occur, for example, when the predetermined number of teeth on the outer circumference of the vehicle speed detection device 35 pass through a signal detection part of the vehicle speed detection sensor 31, such as,

for example, an electrical signal.

  The vehicle speed detection sensor 31 is connected to the control device 30 and sends the vehicle speed signal to the control device 30 in the form of an electrical signal. The vehicle speed detection means have a constitution comprising the vehicle speed detection device 35, the vehicle speed detection sensor 31 and the control device 30 as described above. The controller 30 performs operational processing of the vehicle speed signal to calculate the vehicle speed. The displacement control valve 21 is switched from a neutral position N to a forward displacement position F or to a reverse displacement position R, as shown in the drawing, and controls the direction of the oil under pressure discharged from the displacement pump 12 in order to send it to the displacement motor 13. The displacement control valve 21 re20 receives a pilot displacement pressure, constituting a pilot pressure coming from a displacement switching valve in forward and reverse 22, in a forward pressure side receiving portion 21F or a reverse side pressure receiving portion 21R, whereby it is switched to the traveling position in forward F or in the reverse travel position R from the neutral position N. The travel switch valve in forward and on the reverse 22 is switched to a forward travel position FK, shown in the drawing, in accordance with a forward travel signal from the controller 30, and is switched to a position

  of reverse travel RK as a function of a general reverse travel.

  An accelerator pedal 23A is depressed to actuate a displacement pilot pressure valve 23 so as to cause it to generate a displacement pilot pressure. The pilot displacement pressure, which is that of the means for detecting the extent to which the accelerator pedal 23A is depressed, changes as a function of the extent to which the accelerator pedal 23A is depressed, and, when the depth of depression of the accelerator pedal 23A

  increases, it increases according to a predetermined ratio.

  A displacement pilot pressure sensor 32 is disposed in a circuit between the displacement pilot pressure valve 23 and the forward and reverse displacement switching valve 22, and the displacement pilot pressure sensor 32 sends a signal displacement pilot pressure sensor detected at the control device 30. A displacement charge pressure sensor 33, constituting charge pressure detection means, is disposed at a circuit between the

  displacement pump 12 and the displacement control valve 21, and the displacement charge pressure sensor 33 sends a detected displacement charge pressure signal to the controller.

  A forward and reverse motion switch 34 is connected to the controller 30, and sends a forward motion control signal or a reverse motion control signal to the controller 30. When the device control 30 receives a displacement pilot pressure signal detected by the displacement pilot pressure sensor 32, it calculates a depth of depression of the accelerator pedal 23A as a function of the value of the displacement pilot pressure signal. When the controller 30 receives a displacement load pressure signal detected by the displacement load pressure sensor 33 at the circuit between the displacement pump 12 and the displacement control valve 21, it calculates whether or not no, the pressure of the discharge of oil under pressure by the displacement pump 12 exceeds a predetermined value, as being the load of the displacement resistance. In addition, the controller 30 performs operational processing of the vehicle speed signal, which is an electrical signal, which is detected by the vehicle speed detection sensor 31, in order to calculate the vehicle speed. The control device 30 performs operational processing of a variation over time in the speed of the vehicle, and determines whether it is an acceleration state, in which the speed of the vehicle increases, or a state

  deceleration, in which the vehicle speed decreases.

  When the amount of depression of the accelerator pedal 23A, which is calculated as a function of the magnitude of the previously mentioned displacement pilot pressure signal, is greater than or equal to a predetermined value (for example, the magnitude d depressing three-quarters or more of the full depressing extent of the accelerator pedal 23A), that the displacement charge pressure signal detected by the displacement charge pressure sensor 33 is greater than or equal to one predetermined value of a maximum determined pressure of the displacement pump 12 (for example, greater than or equal to 80% of the maximum determined pressure of the displacement pump 12), and that the displacement state which is obtained by performing a operational processing of the variation in vehicle speed over time is the state of deceleration, in which the vehicle speed is reduced, the control device 30 sends a signal downshift nal to the speed change valve 16 constituting the speed change control means. The gear change valve 16 engages the first speed clutch 14F of the transmission 14 and disengages the second speed clutch 14S to actuate the first speed clutch 14F, whereby the gear ratio is put in the first gear ratio. Transmission 14

  puts the gear in the first forward gear if the current gear is, for example, the second forward gear.

  Next, an operation of the automatic transmission device of the hydraulic mobile vehicle according to the present embodiment will be explained. When an operator switches the forward and reverse motion switch 34 to the forward motion, the forward and reverse motion switch valve 22 is in the forward position FK, and when the operator depresses the accelerator pedal 23A, the pilot displacement pressure is applied to the pressure receiving part of the forward displacement side 21F of the displacement control valve 21, whereby the control valve movement 21 is switched from the neutral position N to the forward movement position F. First, the control device 30 switches the speed change valve 16 to the first speed position 16A as a function of the signal forward travel control of the forward and reverse travel switch 34, and of the gear ratio signal established by a gear shift lever is (not shown), for example the second speed, and engages the first speed clutch 14F and actuates it by disengaging the second speed clutch 14S so as to put the transmission 14 in the first forward speed. The displacement control valve 21 delivers the pressurized oil discharged from the displacement pump 12 to an orifice on the forward displacement side 13F of the displacement motor 13 by

  through the oil pressure swivel joint 15.

  The travel motor rotates in the forward travel direction to drive the transmission

  14, whereby the working vehicle moves forward.

  When the vehicle speed increases and the vehicle speed signal from the vehicle speed detection sensor 31 becomes a predetermined value for switching to the second speed, the control device 30 sends a signal for switching to the higher speed , which is a gear change signal, to the gear change valve 16 to switch the gear change valve 16 to the second gear position 16B, and disengages the first gear clutch 14F, and engages and activates the 'clutch of second vi15 tesse 14S, so as to shift the transmission 14 to the second speed ratio in forward gear. As a result, the work vehicle travels at high speed, but, when traveling on a slope with a climb, the resistance to movement increases, which therefore gradually decreases the speed of the vehicle, and the

  discharge pressure of the displacement pump 12 also increases. The operator depresses the accelerator pedal 23A to fix the speed of the vehicle.

  When the amount of depression on the accelerator pedal 23A, which is calculated as a function of the magnitude of the displacement pilot pressure signal, is greater than or equal to a predetermined value (for example, a depth of depression three-quarters, or more, of the full depressing magnitude of the accelerator pedal 23A), that the displacement charge pressure signal detected by the displacement charge pressure sensor 33 is greater than or equal to one predetermined value of the maximum determined pressure of the displacement pump 12 (for example, 80% or more of the maximum determined pressure of the displacement pump 12), and that the displacement state which is obtained by performing an operational processing of the variation over time of the vehicle speed is the deceleration state, in which the vehicle speed is reduced, the control device 30 sends a downshift signal, which is a s change ignal

  speed, to the speed change valve 16, constituting the speed change control means.

  The gear change valve 16, which receives the downshift signal, is switched to the first gear position 16A, it disengages the second gear clutch 14S from the transmission 14 via the oil pressure swivel joint 15, and it engages and actuates the first speed clutch 14F, so as to consequently carry downshift, in which the gear ratio changes to the first forward speed, which constitutes the lower gear ratio of a gear . Consequently, in the hydraulic mobile vehicle constituting a working vehicle, the optimum speed ratio is automatically selected according to the driving condition of the vehicle, and it can move comfortably even on a traveling road with resistance. at large displacement, such

  than a slope with a climb, without considerably reducing the speed of the vehicle.

  An explanation is given with the transmission 14 comprising two speed ratios, the first speed and the second speed, for example, but a transmission having speed ratios comprising a first, a second and a third speed ratio can be used. In addition, a transmission having a plurality of speed ratios greater than this, for example four speed ratios comprising the fourth speed, or a transmission comprising five speed ratios, further comprising the fifth speed, can be used. The hydraulic mobile vehicle can be a vehicle without an upper rotating superstructure. The present invention can also be applied, for example, to a wheel loader, a

  forklift, or other work vehicles.

  When the automatic transmission device according to the

  present invention is applied to the vehicle without understanding the upper rotating superstructure, it is appropriate to omit the oil pressure swivel joint 15.

  In the embodiment described above, the first speed clutch 14F for a low speed and the second speed clutch 14S for a high speed of the transmission 14 are the clutches according to a method consisting in engaging the clutch by applying pressurized oil and disengage the clutch by releasing the pressurized oil. However, contrary to this, it may be appropriate to adopt a method consisting in having springs for connecting a clutch in the first speed clutch 14F for a low speed and the second speed clutch 14S for a high speed, and to engage the clutch by releasing the oil under pressure and disengage the clutch by applying the oil under pressure. In this process, when the transmission 14 is put into first gear, the pressurized oil going to the first speed clutch 14F from the gear change valve 16 is released so as to engage the first gear speed, and the pressurized oil is applied to the second speed clutch 14S so as to disengage the second speed clutch 14S, whereby the transmission 14 shifts to first speed. However, when the transmission 14 shifts to second gear, the pressurized oil from the second gear clutch 14S to the gear change valve 16 is released so as to engage the second gear clutch, and the pressurized oil is applied to the first speed clutch tesse 14F so as to disengage the first speed clutch 14F, whereby the transmission 14 shifts to the

second gear.

Claims (4)

  1. Automatic transmission device of a hydraulic mobile vehicle, characterized in that it comprises: means for controlling the speed change of a transmission (14); charge pressure detecting means for detecting the charge pressure of a displacement pump (12) for supplying pressurized oil to a displacement motor (13); vehicle speed detecting means for detecting the vehicle speed of the hydraulic mobile vehicle; and a controller (30) which sends a downshift signal to said gear change control means to downshift said transmission (14) when the charge pressure detected by said charge pressure detection means is greater than or equal to a predetermined value, and it is determined that the said hydraulic mobile vehicle is in a deceleration state as a function of the detected vehicle speed   by said vehicle speed detection means.   2. Automatic transmission device of a hydraulic mobile vehicle, characterized in that it comprises: means for controlling the speed change of a transmission (14); depth of sink detection means for detecting a depth of depression of an accelerator pedal (23a); charge pressure detecting means for detecting a charge pressure of a displacement pump (12) for supplying pressurized oil to a displacement motor (13); vehicle speed detection means for detecting a vehicle speed of the hydraulic mobile vehicle; and a controller (30) which sends a downshift signal to said gear change control means to downshift said transmission (14) when the charge pressure detected by said charge pressure detection means is greater than or equal to a predetermined value, that the depth of penetration detected by said depth detection means is greater than or equal to a predetermined value, and that it is determined that said hydraulic mobile vehicle is in a state of deceleration as a function of   the vehicle speed detected by said vehicle speed detection means.   3. Automatic transmission device of the hydraulic mobile vehicle according to claim 1 or claim 2, characterized in that: said speed change control means comprise a two-position switching valve (16).   4. Automatic vehicle transmission device   hydraulic mobile according to any one of claims 1 to 3, characterized in that:   said transmission (14) comprises two stages of displacement.